fs/btrfs/ctree.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2007,2008 Oracle.  All rights reserved.
   4  */
   5
   6 #include <linux/sched.h>
   7 #include <linux/slab.h>
   8 #include <linux/rbtree.h>
   9 #include <linux/mm.h>
  10 #include "ctree.h"
  11 #include "disk-io.h"
  12 #include "transaction.h"
  13 #include "print-tree.h"
  14 #include "locking.h"
  15 #include "volumes.h"
  16
  17 static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
  18                       *root, struct btrfs_path *path, int level);
  19 static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root *root,
  20                       const struct btrfs_key *ins_key, struct btrfs_path *path,
  21                       int data_size, int extend);
  22 static int push_node_left(struct btrfs_trans_handle *trans,
  23                           struct btrfs_fs_info *fs_info,
  24                           struct extent_buffer *dst,
  25                           struct extent_buffer *src, int empty);
  26 static int balance_node_right(struct btrfs_trans_handle *trans,
  27                               struct btrfs_fs_info *fs_info,
  28                               struct extent_buffer *dst_buf,
  29                               struct extent_buffer *src_buf);
  30 static void del_ptr(struct btrfs_root *root, struct btrfs_path *path,
  31                     int level, int slot);
  32
  33 struct btrfs_path *btrfs_alloc_path(void)
  34 {
  35         return kmem_cache_zalloc(btrfs_path_cachep, GFP_NOFS);
  36 }
  37
  38 /*
  39  * set all locked nodes in the path to blocking locks.  This should
  40  * be done before scheduling
  41  */
  42 noinline void btrfs_set_path_blocking(struct btrfs_path *p)
  43 {
  44         int i;
  45         for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
  46                 if (!p->nodes[i] || !p->locks[i])
  47                         continue;
  48                 btrfs_set_lock_blocking_rw(p->nodes[i], p->locks[i]);
  49                 if (p->locks[i] == BTRFS_READ_LOCK)
  50                         p->locks[i] = BTRFS_READ_LOCK_BLOCKING;
  51                 else if (p->locks[i] == BTRFS_WRITE_LOCK)
  52                         p->locks[i] = BTRFS_WRITE_LOCK_BLOCKING;
  53         }
  54 }
  55
  56 /* this also releases the path */
  57 void btrfs_free_path(struct btrfs_path *p)
  58 {
  59         if (!p)
  60                 return;
  61         btrfs_release_path(p);
  62         kmem_cache_free(btrfs_path_cachep, p);
  63 }
  64
  65 /*
  66  * path release drops references on the extent buffers in the path
  67  * and it drops any locks held by this path
  68  *
  69  * It is safe to call this on paths that no locks or extent buffers held.
  70  */
  71 noinline void btrfs_release_path(struct btrfs_path *p)
  72 {
  73         int i;
  74
  75         for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
  76                 p->slots[i] = 0;
  77                 if (!p->nodes[i])
  78                         continue;
  79                 if (p->locks[i]) {
  80                         btrfs_tree_unlock_rw(p->nodes[i], p->locks[i]);
  81                         p->locks[i] = 0;
  82                 }
  83                 free_extent_buffer(p->nodes[i]);
  84                 p->nodes[i] = NULL;
  85         }
  86 }
  87
  88 /*
  89  * safely gets a reference on the root node of a tree.  A lock
  90  * is not taken, so a concurrent writer may put a different node
  91  * at the root of the tree.  See btrfs_lock_root_node for the
  92  * looping required.
  93  *
  94  * The extent buffer returned by this has a reference taken, so
  95  * it won't disappear.  It may stop being the root of the tree
  96  * at any time because there are no locks held.
  97  */
  98 struct extent_buffer *btrfs_root_node(struct btrfs_root *root)
  99 {
 100         struct extent_buffer *eb;
 101
 102         while (1) {
 103                 rcu_read_lock();
 104                 eb = rcu_dereference(root->node);
 105
 106                 /*
 107                  * RCU really hurts here, we could free up the root node because
 108                  * it was COWed but we may not get the new root node yet so do
 109                  * the inc_not_zero dance and if it doesn't work then
 110                  * synchronize_rcu and try again.
 111                  */
 112                 if (atomic_inc_not_zero(&eb->refs)) {
 113                         rcu_read_unlock();
 114                         break;
 115                 }
 116                 rcu_read_unlock();
 117                 synchronize_rcu();
 118         }
 119         return eb;
 120 }
 121
 122 /* loop around taking references on and locking the root node of the
 123  * tree until you end up with a lock on the root.  A locked buffer
 124  * is returned, with a reference held.
 125  */
 126 struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root)
 127 {
 128         struct extent_buffer *eb;
 129
 130         while (1) {
 131                 eb = btrfs_root_node(root);
 132                 btrfs_tree_lock(eb);
 133                 if (eb == root->node)
 134                         break;
 135                 btrfs_tree_unlock(eb);
 136                 free_extent_buffer(eb);
 137         }
 138         return eb;
 139 }
 140
 141 /* loop around taking references on and locking the root node of the
 142  * tree until you end up with a lock on the root.  A locked buffer
 143  * is returned, with a reference held.
 144  */
 145 struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root)
 146 {
 147         struct extent_buffer *eb;
 148
 149         while (1) {
 150                 eb = btrfs_root_node(root);
 151                 btrfs_tree_read_lock(eb);
 152                 if (eb == root->node)
 153                         break;
 154                 btrfs_tree_read_unlock(eb);
 155                 free_extent_buffer(eb);
 156         }
 157         return eb;
 158 }
 159
 160 /* cowonly root (everything not a reference counted cow subvolume), just get
 161  * put onto a simple dirty list.  transaction.c walks this to make sure they
 162  * get properly updated on disk.
 163  */
 164 static void add_root_to_dirty_list(struct btrfs_root *root)
 165 {
 166         struct btrfs_fs_info *fs_info = root->fs_info;
 167
 168         if (test_bit(BTRFS_ROOT_DIRTY, &root->state) ||
 169             !test_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state))
 170                 return;
 171
 172         spin_lock(&fs_info->trans_lock);
 173         if (!test_and_set_bit(BTRFS_ROOT_DIRTY, &root->state)) {
 174                 /* Want the extent tree to be the last on the list */
 175                 if (root->root_key.objectid == BTRFS_EXTENT_TREE_OBJECTID)
 176                         list_move_tail(&root->dirty_list,
 177                                        &fs_info->dirty_cowonly_roots);
 178                 else
 179                         list_move(&root->dirty_list,
 180                                   &fs_info->dirty_cowonly_roots);
 181         }
 182         spin_unlock(&fs_info->trans_lock);
 183 }
 184
 185 /*
 186  * used by snapshot creation to make a copy of a root for a tree with
 187  * a given objectid.  The buffer with the new root node is returned in
 188  * cow_ret, and this func returns zero on success or a negative error code.
 189  */
 190 int btrfs_copy_root(struct btrfs_trans_handle *trans,
 191                       struct btrfs_root *root,
 192                       struct extent_buffer *buf,
 193                       struct extent_buffer **cow_ret, u64 new_root_objectid)
 194 {
 195         struct btrfs_fs_info *fs_info = root->fs_info;
 196         struct extent_buffer *cow;
 197         int ret = 0;
 198         int level;
 199         struct btrfs_disk_key disk_key;
 200
 201         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 202                 trans->transid != fs_info->running_transaction->transid);
 203         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 204                 trans->transid != root->last_trans);
 205
 206         level = btrfs_header_level(buf);
 207         if (level == 0)
 208                 btrfs_item_key(buf, &disk_key, 0);
 209         else
 210                 btrfs_node_key(buf, &disk_key, 0);
 211
 212         cow = btrfs_alloc_tree_block(trans, root, 0, new_root_objectid,
 213                         &disk_key, level, buf->start, 0);
 214         if (IS_ERR(cow))
 215                 return PTR_ERR(cow);
 216
 217         copy_extent_buffer_full(cow, buf);
 218         btrfs_set_header_bytenr(cow, cow->start);
 219         btrfs_set_header_generation(cow, trans->transid);
 220         btrfs_set_header_backref_rev(cow, BTRFS_MIXED_BACKREF_REV);
 221         btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN |
 222                                      BTRFS_HEADER_FLAG_RELOC);
 223         if (new_root_objectid == BTRFS_TREE_RELOC_OBJECTID)
 224                 btrfs_set_header_flag(cow, BTRFS_HEADER_FLAG_RELOC);
 225         else
 226                 btrfs_set_header_owner(cow, new_root_objectid);
 227
 228         write_extent_buffer_fsid(cow, fs_info->fs_devices->metadata_uuid);
 229
 230         WARN_ON(btrfs_header_generation(buf) > trans->transid);
 231         if (new_root_objectid == BTRFS_TREE_RELOC_OBJECTID)
 232                 ret = btrfs_inc_ref(trans, root, cow, 1);
 233         else
 234                 ret = btrfs_inc_ref(trans, root, cow, 0);
 235
 236         if (ret)
 237                 return ret;
 238
 239         btrfs_mark_buffer_dirty(cow);
 240         *cow_ret = cow;
 241         return 0;
 242 }
 243
 244 enum mod_log_op {
 245         MOD_LOG_KEY_REPLACE,
 246         MOD_LOG_KEY_ADD,
 247         MOD_LOG_KEY_REMOVE,
 248         MOD_LOG_KEY_REMOVE_WHILE_FREEING,
 249         MOD_LOG_KEY_REMOVE_WHILE_MOVING,
 250         MOD_LOG_MOVE_KEYS,
 251         MOD_LOG_ROOT_REPLACE,
 252 };
 253
 254 struct tree_mod_root {
 255         u64 logical;
 256         u8 level;
 257 };
 258
 259 struct tree_mod_elem {
 260         struct rb_node node;
 261         u64 logical;
 262         u64 seq;
 263         enum mod_log_op op;
 264
 265         /* this is used for MOD_LOG_KEY_* and MOD_LOG_MOVE_KEYS operations */
 266         int slot;
 267
 268         /* this is used for MOD_LOG_KEY* and MOD_LOG_ROOT_REPLACE */
 269         u64 generation;
 270
 271         /* those are used for op == MOD_LOG_KEY_{REPLACE,REMOVE} */
 272         struct btrfs_disk_key key;
 273         u64 blockptr;
 274
 275         /* this is used for op == MOD_LOG_MOVE_KEYS */
 276         struct {
 277                 int dst_slot;
 278                 int nr_items;
 279         } move;
 280
 281         /* this is used for op == MOD_LOG_ROOT_REPLACE */
 282         struct tree_mod_root old_root;
 283 };
 284
 285 /*
 286  * Pull a new tree mod seq number for our operation.
 287  */
 288 static inline u64 btrfs_inc_tree_mod_seq(struct btrfs_fs_info *fs_info)
 289 {
 290         return atomic64_inc_return(&fs_info->tree_mod_seq);
 291 }
 292
 293 /*
 294  * This adds a new blocker to the tree mod log's blocker list if the @elem
 295  * passed does not already have a sequence number set. So when a caller expects
 296  * to record tree modifications, it should ensure to set elem->seq to zero
 297  * before calling btrfs_get_tree_mod_seq.
 298  * Returns a fresh, unused tree log modification sequence number, even if no new
 299  * blocker was added.
 300  */
 301 u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
 302                            struct seq_list *elem)
 303 {
 304         write_lock(&fs_info->tree_mod_log_lock);
 305         spin_lock(&fs_info->tree_mod_seq_lock);
 306         if (!elem->seq) {
 307                 elem->seq = btrfs_inc_tree_mod_seq(fs_info);
 308                 list_add_tail(&elem->list, &fs_info->tree_mod_seq_list);
 309         }
 310         spin_unlock(&fs_info->tree_mod_seq_lock);
 311         write_unlock(&fs_info->tree_mod_log_lock);
 312
 313         return elem->seq;
 314 }
 315
 316 void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
 317                             struct seq_list *elem)
 318 {
 319         struct rb_root *tm_root;
 320         struct rb_node *node;
 321         struct rb_node *next;
 322         struct seq_list *cur_elem;
 323         struct tree_mod_elem *tm;
 324         u64 min_seq = (u64)-1;
 325         u64 seq_putting = elem->seq;
 326
 327         if (!seq_putting)
 328                 return;
 329
 330         spin_lock(&fs_info->tree_mod_seq_lock);
 331         list_del(&elem->list);
 332         elem->seq = 0;
 333
 334         list_for_each_entry(cur_elem, &fs_info->tree_mod_seq_list, list) {
 335                 if (cur_elem->seq < min_seq) {
 336                         if (seq_putting > cur_elem->seq) {
 337                                 /*
 338                                  * blocker with lower sequence number exists, we
 339                                  * cannot remove anything from the log
 340                                  */
 341                                 spin_unlock(&fs_info->tree_mod_seq_lock);
 342                                 return;
 343                         }
 344                         min_seq = cur_elem->seq;
 345                 }
 346         }
 347         spin_unlock(&fs_info->tree_mod_seq_lock);
 348
 349         /*
 350          * anything that's lower than the lowest existing (read: blocked)
 351          * sequence number can be removed from the tree.
 352          */
 353         write_lock(&fs_info->tree_mod_log_lock);
 354         tm_root = &fs_info->tree_mod_log;
 355         for (node = rb_first(tm_root); node; node = next) {
 356                 next = rb_next(node);
 357                 tm = rb_entry(node, struct tree_mod_elem, node);
 358                 if (tm->seq > min_seq)
 359                         continue;
 360                 rb_erase(node, tm_root);
 361                 kfree(tm);
 362         }
 363         write_unlock(&fs_info->tree_mod_log_lock);
 364 }
 365
 366 /*
 367  * key order of the log:
 368  *       node/leaf start address -> sequence
 369  *
 370  * The 'start address' is the logical address of the *new* root node
 371  * for root replace operations, or the logical address of the affected
 372  * block for all other operations.
 373  *
 374  * Note: must be called with write lock for fs_info::tree_mod_log_lock.
 375  */
 376 static noinline int
 377 __tree_mod_log_insert(struct btrfs_fs_info *fs_info, struct tree_mod_elem *tm)
 378 {
 379         struct rb_root *tm_root;
 380         struct rb_node **new;
 381         struct rb_node *parent = NULL;
 382         struct tree_mod_elem *cur;
 383
 384         tm->seq = btrfs_inc_tree_mod_seq(fs_info);
 385
 386         tm_root = &fs_info->tree_mod_log;
 387         new = &tm_root->rb_node;
 388         while (*new) {
 389                 cur = rb_entry(*new, struct tree_mod_elem, node);
 390                 parent = *new;
 391                 if (cur->logical < tm->logical)
 392                         new = &((*new)->rb_left);
 393                 else if (cur->logical > tm->logical)
 394                         new = &((*new)->rb_right);
 395                 else if (cur->seq < tm->seq)
 396                         new = &((*new)->rb_left);
 397                 else if (cur->seq > tm->seq)
 398                         new = &((*new)->rb_right);
 399                 else
 400                         return -EEXIST;
 401         }
 402
 403         rb_link_node(&tm->node, parent, new);
 404         rb_insert_color(&tm->node, tm_root);
 405         return 0;
 406 }
 407
 408 /*
 409  * Determines if logging can be omitted. Returns 1 if it can. Otherwise, it
 410  * returns zero with the tree_mod_log_lock acquired. The caller must hold
 411  * this until all tree mod log insertions are recorded in the rb tree and then
 412  * write unlock fs_info::tree_mod_log_lock.
 413  */
 414 static inline int tree_mod_dont_log(struct btrfs_fs_info *fs_info,
 415                                     struct extent_buffer *eb) {
 416         smp_mb();
 417         if (list_empty(&(fs_info)->tree_mod_seq_list))
 418                 return 1;
 419         if (eb && btrfs_header_level(eb) == 0)
 420                 return 1;
 421
 422         write_lock(&fs_info->tree_mod_log_lock);
 423         if (list_empty(&(fs_info)->tree_mod_seq_list)) {
 424                 write_unlock(&fs_info->tree_mod_log_lock);
 425                 return 1;
 426         }
 427
 428         return 0;
 429 }
 430
 431 /* Similar to tree_mod_dont_log, but doesn't acquire any locks. */
 432 static inline int tree_mod_need_log(const struct btrfs_fs_info *fs_info,
 433                                     struct extent_buffer *eb)
 434 {
 435         smp_mb();
 436         if (list_empty(&(fs_info)->tree_mod_seq_list))
 437                 return 0;
 438         if (eb && btrfs_header_level(eb) == 0)
 439                 return 0;
 440
 441         return 1;
 442 }
 443
 444 static struct tree_mod_elem *
 445 alloc_tree_mod_elem(struct extent_buffer *eb, int slot,
 446                     enum mod_log_op op, gfp_t flags)
 447 {
 448         struct tree_mod_elem *tm;
 449
 450         tm = kzalloc(sizeof(*tm), flags);
 451         if (!tm)
 452                 return NULL;
 453
 454         tm->logical = eb->start;
 455         if (op != MOD_LOG_KEY_ADD) {
 456                 btrfs_node_key(eb, &tm->key, slot);
 457                 tm->blockptr = btrfs_node_blockptr(eb, slot);
 458         }
 459         tm->op = op;
 460         tm->slot = slot;
 461         tm->generation = btrfs_node_ptr_generation(eb, slot);
 462         RB_CLEAR_NODE(&tm->node);
 463
 464         return tm;
 465 }
 466
 467 static noinline int tree_mod_log_insert_key(struct extent_buffer *eb, int slot,
 468                 enum mod_log_op op, gfp_t flags)
 469 {
 470         struct tree_mod_elem *tm;
 471         int ret;
 472
 473         if (!tree_mod_need_log(eb->fs_info, eb))
 474                 return 0;
 475
 476         tm = alloc_tree_mod_elem(eb, slot, op, flags);
 477         if (!tm)
 478                 return -ENOMEM;
 479
 480         if (tree_mod_dont_log(eb->fs_info, eb)) {
 481                 kfree(tm);
 482                 return 0;
 483         }
 484
 485         ret = __tree_mod_log_insert(eb->fs_info, tm);
 486         write_unlock(&eb->fs_info->tree_mod_log_lock);
 487         if (ret)
 488                 kfree(tm);
 489
 490         return ret;
 491 }
 492
 493 static noinline int tree_mod_log_insert_move(struct extent_buffer *eb,
 494                 int dst_slot, int src_slot, int nr_items)
 495 {
 496         struct tree_mod_elem *tm = NULL;
 497         struct tree_mod_elem **tm_list = NULL;
 498         int ret = 0;
 499         int i;
 500         int locked = 0;
 501
 502         if (!tree_mod_need_log(eb->fs_info, eb))
 503                 return 0;
 504
 505         tm_list = kcalloc(nr_items, sizeof(struct tree_mod_elem *), GFP_NOFS);
 506         if (!tm_list)
 507                 return -ENOMEM;
 508
 509         tm = kzalloc(sizeof(*tm), GFP_NOFS);
 510         if (!tm) {
 511                 ret = -ENOMEM;
 512                 goto free_tms;
 513         }
 514
 515         tm->logical = eb->start;
 516         tm->slot = src_slot;
 517         tm->move.dst_slot = dst_slot;
 518         tm->move.nr_items = nr_items;
 519         tm->op = MOD_LOG_MOVE_KEYS;
 520
 521         for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
 522                 tm_list[i] = alloc_tree_mod_elem(eb, i + dst_slot,
 523                     MOD_LOG_KEY_REMOVE_WHILE_MOVING, GFP_NOFS);
 524                 if (!tm_list[i]) {
 525                         ret = -ENOMEM;
 526                         goto free_tms;
 527                 }
 528         }
 529
 530         if (tree_mod_dont_log(eb->fs_info, eb))
 531                 goto free_tms;
 532         locked = 1;
 533
 534         /*
 535          * When we override something during the move, we log these removals.
 536          * This can only happen when we move towards the beginning of the
 537          * buffer, i.e. dst_slot < src_slot.
 538          */
 539         for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
 540                 ret = __tree_mod_log_insert(eb->fs_info, tm_list[i]);
 541                 if (ret)
 542                         goto free_tms;
 543         }
 544
 545         ret = __tree_mod_log_insert(eb->fs_info, tm);
 546         if (ret)
 547                 goto free_tms;
 548         write_unlock(&eb->fs_info->tree_mod_log_lock);
 549         kfree(tm_list);
 550
 551         return 0;
 552 free_tms:
 553         for (i = 0; i < nr_items; i++) {
 554                 if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
 555                         rb_erase(&tm_list[i]->node, &eb->fs_info->tree_mod_log);
 556                 kfree(tm_list[i]);
 557         }
 558         if (locked)
 559                 write_unlock(&eb->fs_info->tree_mod_log_lock);
 560         kfree(tm_list);
 561         kfree(tm);
 562
 563         return ret;
 564 }
 565
 566 static inline int
 567 __tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
 568                        struct tree_mod_elem **tm_list,
 569                        int nritems)
 570 {
 571         int i, j;
 572         int ret;
 573
 574         for (i = nritems - 1; i >= 0; i--) {
 575                 ret = __tree_mod_log_insert(fs_info, tm_list[i]);
 576                 if (ret) {
 577                         for (j = nritems - 1; j > i; j--)
 578                                 rb_erase(&tm_list[j]->node,
 579                                          &fs_info->tree_mod_log);
 580                         return ret;
 581                 }
 582         }
 583
 584         return 0;
 585 }
 586
 587 static noinline int tree_mod_log_insert_root(struct extent_buffer *old_root,
 588                          struct extent_buffer *new_root, int log_removal)
 589 {
 590         struct btrfs_fs_info *fs_info = old_root->fs_info;
 591         struct tree_mod_elem *tm = NULL;
 592         struct tree_mod_elem **tm_list = NULL;
 593         int nritems = 0;
 594         int ret = 0;
 595         int i;
 596
 597         if (!tree_mod_need_log(fs_info, NULL))
 598                 return 0;
 599
 600         if (log_removal && btrfs_header_level(old_root) > 0) {
 601                 nritems = btrfs_header_nritems(old_root);
 602                 tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *),
 603                                   GFP_NOFS);
 604                 if (!tm_list) {
 605                         ret = -ENOMEM;
 606                         goto free_tms;
 607                 }
 608                 for (i = 0; i < nritems; i++) {
 609                         tm_list[i] = alloc_tree_mod_elem(old_root, i,
 610                             MOD_LOG_KEY_REMOVE_WHILE_FREEING, GFP_NOFS);
 611                         if (!tm_list[i]) {
 612                                 ret = -ENOMEM;
 613                                 goto free_tms;
 614                         }
 615                 }
 616         }
 617
 618         tm = kzalloc(sizeof(*tm), GFP_NOFS);
 619         if (!tm) {
 620                 ret = -ENOMEM;
 621                 goto free_tms;
 622         }
 623
 624         tm->logical = new_root->start;
 625         tm->old_root.logical = old_root->start;
 626         tm->old_root.level = btrfs_header_level(old_root);
 627         tm->generation = btrfs_header_generation(old_root);
 628         tm->op = MOD_LOG_ROOT_REPLACE;
 629
 630         if (tree_mod_dont_log(fs_info, NULL))
 631                 goto free_tms;
 632
 633         if (tm_list)
 634                 ret = __tree_mod_log_free_eb(fs_info, tm_list, nritems);
 635         if (!ret)
 636                 ret = __tree_mod_log_insert(fs_info, tm);
 637
 638         write_unlock(&fs_info->tree_mod_log_lock);
 639         if (ret)
 640                 goto free_tms;
 641         kfree(tm_list);
 642
 643         return ret;
 644
 645 free_tms:
 646         if (tm_list) {
 647                 for (i = 0; i < nritems; i++)
 648                         kfree(tm_list[i]);
 649                 kfree(tm_list);
 650         }
 651         kfree(tm);
 652
 653         return ret;
 654 }
 655
 656 static struct tree_mod_elem *
 657 __tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq,
 658                       int smallest)
 659 {
 660         struct rb_root *tm_root;
 661         struct rb_node *node;
 662         struct tree_mod_elem *cur = NULL;
 663         struct tree_mod_elem *found = NULL;
 664
 665         read_lock(&fs_info->tree_mod_log_lock);
 666         tm_root = &fs_info->tree_mod_log;
 667         node = tm_root->rb_node;
 668         while (node) {
 669                 cur = rb_entry(node, struct tree_mod_elem, node);
 670                 if (cur->logical < start) {
 671                         node = node->rb_left;
 672                 } else if (cur->logical > start) {
 673                         node = node->rb_right;
 674                 } else if (cur->seq < min_seq) {
 675                         node = node->rb_left;
 676                 } else if (!smallest) {
 677                         /* we want the node with the highest seq */
 678                         if (found)
 679                                 BUG_ON(found->seq > cur->seq);
 680                         found = cur;
 681                         node = node->rb_left;
 682                 } else if (cur->seq > min_seq) {
 683                         /* we want the node with the smallest seq */
 684                         if (found)
 685                                 BUG_ON(found->seq < cur->seq);
 686                         found = cur;
 687                         node = node->rb_right;
 688                 } else {
 689                         found = cur;
 690                         break;
 691                 }
 692         }
 693         read_unlock(&fs_info->tree_mod_log_lock);
 694
 695         return found;
 696 }
 697
 698 /*
 699  * this returns the element from the log with the smallest time sequence
 700  * value that's in the log (the oldest log item). any element with a time
 701  * sequence lower than min_seq will be ignored.
 702  */
 703 static struct tree_mod_elem *
 704 tree_mod_log_search_oldest(struct btrfs_fs_info *fs_info, u64 start,
 705                            u64 min_seq)
 706 {
 707         return __tree_mod_log_search(fs_info, start, min_seq, 1);
 708 }
 709
 710 /*
 711  * this returns the element from the log with the largest time sequence
 712  * value that's in the log (the most recent log item). any element with
 713  * a time sequence lower than min_seq will be ignored.
 714  */
 715 static struct tree_mod_elem *
 716 tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq)
 717 {
 718         return __tree_mod_log_search(fs_info, start, min_seq, 0);
 719 }
 720
 721 static noinline int
 722 tree_mod_log_eb_copy(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
 723                      struct extent_buffer *src, unsigned long dst_offset,
 724                      unsigned long src_offset, int nr_items)
 725 {
 726         int ret = 0;
 727         struct tree_mod_elem **tm_list = NULL;
 728         struct tree_mod_elem **tm_list_add, **tm_list_rem;
 729         int i;
 730         int locked = 0;
 731
 732         if (!tree_mod_need_log(fs_info, NULL))
 733                 return 0;
 734
 735         if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0)
 736                 return 0;
 737
 738         tm_list = kcalloc(nr_items * 2, sizeof(struct tree_mod_elem *),
 739                           GFP_NOFS);
 740         if (!tm_list)
 741                 return -ENOMEM;
 742
 743         tm_list_add = tm_list;
 744         tm_list_rem = tm_list + nr_items;
 745         for (i = 0; i < nr_items; i++) {
 746                 tm_list_rem[i] = alloc_tree_mod_elem(src, i + src_offset,
 747                     MOD_LOG_KEY_REMOVE, GFP_NOFS);
 748                 if (!tm_list_rem[i]) {
 749                         ret = -ENOMEM;
 750                         goto free_tms;
 751                 }
 752
 753                 tm_list_add[i] = alloc_tree_mod_elem(dst, i + dst_offset,
 754                     MOD_LOG_KEY_ADD, GFP_NOFS);
 755                 if (!tm_list_add[i]) {
 756                         ret = -ENOMEM;
 757                         goto free_tms;
 758                 }
 759         }
 760
 761         if (tree_mod_dont_log(fs_info, NULL))
 762                 goto free_tms;
 763         locked = 1;
 764
 765         for (i = 0; i < nr_items; i++) {
 766                 ret = __tree_mod_log_insert(fs_info, tm_list_rem[i]);
 767                 if (ret)
 768                         goto free_tms;
 769                 ret = __tree_mod_log_insert(fs_info, tm_list_add[i]);
 770                 if (ret)
 771                         goto free_tms;
 772         }
 773
 774         write_unlock(&fs_info->tree_mod_log_lock);
 775         kfree(tm_list);
 776
 777         return 0;
 778
 779 free_tms:
 780         for (i = 0; i < nr_items * 2; i++) {
 781                 if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
 782                         rb_erase(&tm_list[i]->node, &fs_info->tree_mod_log);
 783                 kfree(tm_list[i]);
 784         }
 785         if (locked)
 786                 write_unlock(&fs_info->tree_mod_log_lock);
 787         kfree(tm_list);
 788
 789         return ret;
 790 }
 791
 792 static noinline int tree_mod_log_free_eb(struct extent_buffer *eb)
 793 {
 794         struct tree_mod_elem **tm_list = NULL;
 795         int nritems = 0;
 796         int i;
 797         int ret = 0;
 798
 799         if (btrfs_header_level(eb) == 0)
 800                 return 0;
 801
 802         if (!tree_mod_need_log(eb->fs_info, NULL))
 803                 return 0;
 804
 805         nritems = btrfs_header_nritems(eb);
 806         tm_list = kcalloc(nritems, sizeof(struct tree_mod_elem *), GFP_NOFS);
 807         if (!tm_list)
 808                 return -ENOMEM;
 809
 810         for (i = 0; i < nritems; i++) {
 811                 tm_list[i] = alloc_tree_mod_elem(eb, i,
 812                     MOD_LOG_KEY_REMOVE_WHILE_FREEING, GFP_NOFS);
 813                 if (!tm_list[i]) {
 814                         ret = -ENOMEM;
 815                         goto free_tms;
 816                 }
 817         }
 818
 819         if (tree_mod_dont_log(eb->fs_info, eb))
 820                 goto free_tms;
 821
 822         ret = __tree_mod_log_free_eb(eb->fs_info, tm_list, nritems);
 823         write_unlock(&eb->fs_info->tree_mod_log_lock);
 824         if (ret)
 825                 goto free_tms;
 826         kfree(tm_list);
 827
 828         return 0;
 829
 830 free_tms:
 831         for (i = 0; i < nritems; i++)
 832                 kfree(tm_list[i]);
 833         kfree(tm_list);
 834
 835         return ret;
 836 }
 837
 838 /*
 839  * check if the tree block can be shared by multiple trees
 840  */
 841 int btrfs_block_can_be_shared(struct btrfs_root *root,
 842                               struct extent_buffer *buf)
 843 {
 844         /*
 845          * Tree blocks not in reference counted trees and tree roots
 846          * are never shared. If a block was allocated after the last
 847          * snapshot and the block was not allocated by tree relocation,
 848          * we know the block is not shared.
 849          */
 850         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
 851             buf != root->node && buf != root->commit_root &&
 852             (btrfs_header_generation(buf) <=
 853              btrfs_root_last_snapshot(&root->root_item) ||
 854              btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)))
 855                 return 1;
 856
 857         return 0;
 858 }
 859
 860 static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
 861                                        struct btrfs_root *root,
 862                                        struct extent_buffer *buf,
 863                                        struct extent_buffer *cow,
 864                                        int *last_ref)
 865 {
 866         struct btrfs_fs_info *fs_info = root->fs_info;
 867         u64 refs;
 868         u64 owner;
 869         u64 flags;
 870         u64 new_flags = 0;
 871         int ret;
 872
 873         /*
 874          * Backrefs update rules:
 875          *
 876          * Always use full backrefs for extent pointers in tree block
 877          * allocated by tree relocation.
 878          *
 879          * If a shared tree block is no longer referenced by its owner
 880          * tree (btrfs_header_owner(buf) == root->root_key.objectid),
 881          * use full backrefs for extent pointers in tree block.
 882          *
 883          * If a tree block is been relocating
 884          * (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID),
 885          * use full backrefs for extent pointers in tree block.
 886          * The reason for this is some operations (such as drop tree)
 887          * are only allowed for blocks use full backrefs.
 888          */
 889
 890         if (btrfs_block_can_be_shared(root, buf)) {
 891                 ret = btrfs_lookup_extent_info(trans, fs_info, buf->start,
 892                                                btrfs_header_level(buf), 1,
 893                                                &refs, &flags);
 894                 if (ret)
 895                         return ret;
 896                 if (refs == 0) {
 897                         ret = -EROFS;
 898                         btrfs_handle_fs_error(fs_info, ret, NULL);
 899                         return ret;
 900                 }
 901         } else {
 902                 refs = 1;
 903                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
 904                     btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
 905                         flags = BTRFS_BLOCK_FLAG_FULL_BACKREF;
 906                 else
 907                         flags = 0;
 908         }
 909
 910         owner = btrfs_header_owner(buf);
 911         BUG_ON(owner == BTRFS_TREE_RELOC_OBJECTID &&
 912                !(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF));
 913
 914         if (refs > 1) {
 915                 if ((owner == root->root_key.objectid ||
 916                      root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) &&
 917                     !(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)) {
 918                         ret = btrfs_inc_ref(trans, root, buf, 1);
 919                         if (ret)
 920                                 return ret;
 921
 922                         if (root->root_key.objectid ==
 923                             BTRFS_TREE_RELOC_OBJECTID) {
 924                                 ret = btrfs_dec_ref(trans, root, buf, 0);
 925                                 if (ret)
 926                                         return ret;
 927                                 ret = btrfs_inc_ref(trans, root, cow, 1);
 928                                 if (ret)
 929                                         return ret;
 930                         }
 931                         new_flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
 932                 } else {
 933
 934                         if (root->root_key.objectid ==
 935                             BTRFS_TREE_RELOC_OBJECTID)
 936                                 ret = btrfs_inc_ref(trans, root, cow, 1);
 937                         else
 938                                 ret = btrfs_inc_ref(trans, root, cow, 0);
 939                         if (ret)
 940                                 return ret;
 941                 }
 942                 if (new_flags != 0) {
 943                         int level = btrfs_header_level(buf);
 944
 945                         ret = btrfs_set_disk_extent_flags(trans, fs_info,
 946                                                           buf->start,
 947                                                           buf->len,
 948                                                           new_flags, level, 0);
 949                         if (ret)
 950                                 return ret;
 951                 }
 952         } else {
 953                 if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
 954                         if (root->root_key.objectid ==
 955                             BTRFS_TREE_RELOC_OBJECTID)
 956                                 ret = btrfs_inc_ref(trans, root, cow, 1);
 957                         else
 958                                 ret = btrfs_inc_ref(trans, root, cow, 0);
 959                         if (ret)
 960                                 return ret;
 961                         ret = btrfs_dec_ref(trans, root, buf, 1);
 962                         if (ret)
 963                                 return ret;
 964                 }
 965                 clean_tree_block(fs_info, buf);
 966                 *last_ref = 1;
 967         }
 968         return 0;
 969 }
 970
 971 static struct extent_buffer *alloc_tree_block_no_bg_flush(
 972                                           struct btrfs_trans_handle *trans,
 973                                           struct btrfs_root *root,
 974                                           u64 parent_start,
 975                                           const struct btrfs_disk_key *disk_key,
 976                                           int level,
 977                                           u64 hint,
 978                                           u64 empty_size)
 979 {
 980         struct btrfs_fs_info *fs_info = root->fs_info;
 981         struct extent_buffer *ret;
 982
 983         /*
 984          * If we are COWing a node/leaf from the extent, chunk, device or free
 985          * space trees, make sure that we do not finish block group creation of
 986          * pending block groups. We do this to avoid a deadlock.
 987          * COWing can result in allocation of a new chunk, and flushing pending
 988          * block groups (btrfs_create_pending_block_groups()) can be triggered
 989          * when finishing allocation of a new chunk. Creation of a pending block
 990          * group modifies the extent, chunk, device and free space trees,
 991          * therefore we could deadlock with ourselves since we are holding a
 992          * lock on an extent buffer that btrfs_create_pending_block_groups() may
 993          * try to COW later.
 994          * For similar reasons, we also need to delay flushing pending block
 995          * groups when splitting a leaf or node, from one of those trees, since
 996          * we are holding a write lock on it and its parent or when inserting a
 997          * new root node for one of those trees.
 998          */
 999         if (root == fs_info->extent_root ||
1000             root == fs_info->chunk_root ||
1001             root == fs_info->dev_root ||
1002             root == fs_info->free_space_root)
1003                 trans->can_flush_pending_bgs = false;
1004
1005         ret = btrfs_alloc_tree_block(trans, root, parent_start,
1006                                      root->root_key.objectid, disk_key, level,
1007                                      hint, empty_size);
1008         trans->can_flush_pending_bgs = true;
1009
1010         return ret;
1011 }
1012
1013 /*
1014  * does the dirty work in cow of a single block.  The parent block (if
1015  * supplied) is updated to point to the new cow copy.  The new buffer is marked
1016  * dirty and returned locked.  If you modify the block it needs to be marked
1017  * dirty again.
1018  *
1019  * search_start -- an allocation hint for the new block
1020  *
1021  * empty_size -- a hint that you plan on doing more cow.  This is the size in
1022  * bytes the allocator should try to find free next to the block it returns.
1023  * This is just a hint and may be ignored by the allocator.
1024  */
1025 static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
1026                              struct btrfs_root *root,
1027                              struct extent_buffer *buf,
1028                              struct extent_buffer *parent, int parent_slot,
1029                              struct extent_buffer **cow_ret,
1030                              u64 search_start, u64 empty_size)
1031 {
1032         struct btrfs_fs_info *fs_info = root->fs_info;
1033         struct btrfs_disk_key disk_key;
1034         struct extent_buffer *cow;
1035         int level, ret;
1036         int last_ref = 0;
1037         int unlock_orig = 0;
1038         u64 parent_start = 0;
1039
1040         if (*cow_ret == buf)
1041                 unlock_orig = 1;
1042
1043         btrfs_assert_tree_locked(buf);
1044
1045         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
1046                 trans->transid != fs_info->running_transaction->transid);
1047         WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
1048                 trans->transid != root->last_trans);
1049
1050         level = btrfs_header_level(buf);
1051
1052         if (level == 0)
1053                 btrfs_item_key(buf, &disk_key, 0);
1054         else
1055                 btrfs_node_key(buf, &disk_key, 0);
1056
1057         if ((root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) && parent)
1058                 parent_start = parent->start;
1059
1060         cow = alloc_tree_block_no_bg_flush(trans, root, parent_start, &disk_key,
1061                                            level, search_start, empty_size);
1062         if (IS_ERR(cow))
1063                 return PTR_ERR(cow);
1064
1065         /* cow is set to blocking by btrfs_init_new_buffer */
1066
1067         copy_extent_buffer_full(cow, buf);
1068         btrfs_set_header_bytenr(cow, cow->start);
1069         btrfs_set_header_generation(cow, trans->transid);
1070         btrfs_set_header_backref_rev(cow, BTRFS_MIXED_BACKREF_REV);
1071         btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN |
1072                                      BTRFS_HEADER_FLAG_RELOC);
1073         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1074                 btrfs_set_header_flag(cow, BTRFS_HEADER_FLAG_RELOC);
1075         else
1076                 btrfs_set_header_owner(cow, root->root_key.objectid);
1077
1078         write_extent_buffer_fsid(cow, fs_info->fs_devices->metadata_uuid);
1079
1080         ret = update_ref_for_cow(trans, root, buf, cow, &last_ref);
1081         if (ret) {
1082                 btrfs_abort_transaction(trans, ret);
1083                 return ret;
1084         }
1085
1086         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
1087                 ret = btrfs_reloc_cow_block(trans, root, buf, cow);
1088                 if (ret) {
1089                         btrfs_abort_transaction(trans, ret);
1090                         return ret;
1091                 }
1092         }
1093
1094         if (buf == root->node) {
1095                 WARN_ON(parent && parent != buf);
1096                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
1097                     btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
1098                         parent_start = buf->start;
1099
1100                 extent_buffer_get(cow);
1101                 ret = tree_mod_log_insert_root(root->node, cow, 1);
1102                 BUG_ON(ret < 0);
1103                 rcu_assign_pointer(root->node, cow);
1104
1105                 btrfs_free_tree_block(trans, root, buf, parent_start,
1106                                       last_ref);
1107                 free_extent_buffer(buf);
1108                 add_root_to_dirty_list(root);
1109         } else {
1110                 WARN_ON(trans->transid != btrfs_header_generation(parent));
1111                 tree_mod_log_insert_key(parent, parent_slot,
1112                                         MOD_LOG_KEY_REPLACE, GFP_NOFS);
1113                 btrfs_set_node_blockptr(parent, parent_slot,
1114                                         cow->start);
1115                 btrfs_set_node_ptr_generation(parent, parent_slot,
1116                                               trans->transid);
1117                 btrfs_mark_buffer_dirty(parent);
1118                 if (last_ref) {
1119                         ret = tree_mod_log_free_eb(buf);
1120                         if (ret) {
1121                                 btrfs_abort_transaction(trans, ret);
1122                                 return ret;
1123                         }
1124                 }
1125                 btrfs_free_tree_block(trans, root, buf, parent_start,
1126                                       last_ref);
1127         }
1128         if (unlock_orig)
1129                 btrfs_tree_unlock(buf);
1130         free_extent_buffer_stale(buf);
1131         btrfs_mark_buffer_dirty(cow);
1132         *cow_ret = cow;
1133         return 0;
1134 }
1135
1136 /*
1137  * returns the logical address of the oldest predecessor of the given root.
1138  * entries older than time_seq are ignored.
1139  */
1140 static struct tree_mod_elem *__tree_mod_log_oldest_root(
1141                 struct extent_buffer *eb_root, u64 time_seq)
1142 {
1143         struct tree_mod_elem *tm;
1144         struct tree_mod_elem *found = NULL;
1145         u64 root_logical = eb_root->start;
1146         int looped = 0;
1147
1148         if (!time_seq)
1149                 return NULL;
1150
1151         /*
1152          * the very last operation that's logged for a root is the
1153          * replacement operation (if it is replaced at all). this has
1154          * the logical address of the *new* root, making it the very
1155          * first operation that's logged for this root.
1156          */
1157         while (1) {
1158                 tm = tree_mod_log_search_oldest(eb_root->fs_info, root_logical,
1159                                                 time_seq);
1160                 if (!looped && !tm)
1161                         return NULL;
1162                 /*
1163                  * if there are no tree operation for the oldest root, we simply
1164                  * return it. this should only happen if that (old) root is at
1165                  * level 0.
1166                  */
1167                 if (!tm)
1168                         break;
1169
1170                 /*
1171                  * if there's an operation that's not a root replacement, we
1172                  * found the oldest version of our root. normally, we'll find a
1173                  * MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here.
1174                  */
1175                 if (tm->op != MOD_LOG_ROOT_REPLACE)
1176                         break;
1177
1178                 found = tm;
1179                 root_logical = tm->old_root.logical;
1180                 looped = 1;
1181         }
1182
1183         /* if there's no old root to return, return what we found instead */
1184         if (!found)
1185                 found = tm;
1186
1187         return found;
1188 }
1189
1190 /*
1191  * tm is a pointer to the first operation to rewind within eb. then, all
1192  * previous operations will be rewound (until we reach something older than
1193  * time_seq).
1194  */
1195 static void
1196 __tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct extent_buffer *eb,
1197                       u64 time_seq, struct tree_mod_elem *first_tm)
1198 {
1199         u32 n;
1200         struct rb_node *next;
1201         struct tree_mod_elem *tm = first_tm;
1202         unsigned long o_dst;
1203         unsigned long o_src;
1204         unsigned long p_size = sizeof(struct btrfs_key_ptr);
1205
1206         n = btrfs_header_nritems(eb);
1207         read_lock(&fs_info->tree_mod_log_lock);
1208         while (tm && tm->seq >= time_seq) {
1209                 /*
1210                  * all the operations are recorded with the operator used for
1211                  * the modification. as we're going backwards, we do the
1212                  * opposite of each operation here.
1213                  */
1214                 switch (tm->op) {
1215                 case MOD_LOG_KEY_REMOVE_WHILE_FREEING:
1216                         BUG_ON(tm->slot < n);
1217                         /* Fallthrough */
1218                 case MOD_LOG_KEY_REMOVE_WHILE_MOVING:
1219                 case MOD_LOG_KEY_REMOVE:
1220                         btrfs_set_node_key(eb, &tm->key, tm->slot);
1221                         btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
1222                         btrfs_set_node_ptr_generation(eb, tm->slot,
1223                                                       tm->generation);
1224                         n++;
1225                         break;
1226                 case MOD_LOG_KEY_REPLACE:
1227                         BUG_ON(tm->slot >= n);
1228                         btrfs_set_node_key(eb, &tm->key, tm->slot);
1229                         btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
1230                         btrfs_set_node_ptr_generation(eb, tm->slot,
1231                                                       tm->generation);
1232                         break;
1233                 case MOD_LOG_KEY_ADD:
1234                         /* if a move operation is needed it's in the log */
1235                         n--;
1236                         break;
1237                 case MOD_LOG_MOVE_KEYS:
1238                         o_dst = btrfs_node_key_ptr_offset(tm->slot);
1239                         o_src = btrfs_node_key_ptr_offset(tm->move.dst_slot);
1240                         memmove_extent_buffer(eb, o_dst, o_src,
1241                                               tm->move.nr_items * p_size);
1242                         break;
1243                 case MOD_LOG_ROOT_REPLACE:
1244                         /*
1245                          * this operation is special. for roots, this must be
1246                          * handled explicitly before rewinding.
1247                          * for non-roots, this operation may exist if the node
1248                          * was a root: root A -> child B; then A gets empty and
1249                          * B is promoted to the new root. in the mod log, we'll
1250                          * have a root-replace operation for B, a tree block
1251                          * that is no root. we simply ignore that operation.
1252                          */
1253                         break;
1254                 }
1255                 next = rb_next(&tm->node);
1256                 if (!next)
1257                         break;
1258                 tm = rb_entry(next, struct tree_mod_elem, node);
1259                 if (tm->logical != first_tm->logical)
1260                         break;
1261         }
1262         read_unlock(&fs_info->tree_mod_log_lock);
1263         btrfs_set_header_nritems(eb, n);
1264 }
1265
1266 /*
1267  * Called with eb read locked. If the buffer cannot be rewound, the same buffer
1268  * is returned. If rewind operations happen, a fresh buffer is returned. The
1269  * returned buffer is always read-locked. If the returned buffer is not the
1270  * input buffer, the lock on the input buffer is released and the input buffer
1271  * is freed (its refcount is decremented).
1272  */
1273 static struct extent_buffer *
1274 tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
1275                     struct extent_buffer *eb, u64 time_seq)
1276 {
1277         struct extent_buffer *eb_rewin;
1278         struct tree_mod_elem *tm;
1279
1280         if (!time_seq)
1281                 return eb;
1282
1283         if (btrfs_header_level(eb) == 0)
1284                 return eb;
1285
1286         tm = tree_mod_log_search(fs_info, eb->start, time_seq);
1287         if (!tm)
1288                 return eb;
1289
1290         btrfs_set_path_blocking(path);
1291         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1292
1293         if (tm->op == MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
1294                 BUG_ON(tm->slot != 0);
1295                 eb_rewin = alloc_dummy_extent_buffer(fs_info, eb->start);
1296                 if (!eb_rewin) {
1297                         btrfs_tree_read_unlock_blocking(eb);
1298                         free_extent_buffer(eb);
1299                         return NULL;
1300                 }
1301                 btrfs_set_header_bytenr(eb_rewin, eb->start);
1302                 btrfs_set_header_backref_rev(eb_rewin,
1303                                              btrfs_header_backref_rev(eb));
1304                 btrfs_set_header_owner(eb_rewin, btrfs_header_owner(eb));
1305                 btrfs_set_header_level(eb_rewin, btrfs_header_level(eb));
1306         } else {
1307                 eb_rewin = btrfs_clone_extent_buffer(eb);
1308                 if (!eb_rewin) {
1309                         btrfs_tree_read_unlock_blocking(eb);
1310                         free_extent_buffer(eb);
1311                         return NULL;
1312                 }
1313         }
1314
1315         btrfs_tree_read_unlock_blocking(eb);
1316         free_extent_buffer(eb);
1317
1318         btrfs_tree_read_lock(eb_rewin);
1319         __tree_mod_log_rewind(fs_info, eb_rewin, time_seq, tm);
1320         WARN_ON(btrfs_header_nritems(eb_rewin) >
1321                 BTRFS_NODEPTRS_PER_BLOCK(fs_info));
1322
1323         return eb_rewin;
1324 }
1325
1326 /*
1327  * get_old_root() rewinds the state of @root's root node to the given @time_seq
1328  * value. If there are no changes, the current root->root_node is returned. If
1329  * anything changed in between, there's a fresh buffer allocated on which the
1330  * rewind operations are done. In any case, the returned buffer is read locked.
1331  * Returns NULL on error (with no locks held).
1332  */
1333 static inline struct extent_buffer *
1334 get_old_root(struct btrfs_root *root, u64 time_seq)
1335 {
1336         struct btrfs_fs_info *fs_info = root->fs_info;
1337         struct tree_mod_elem *tm;
1338         struct extent_buffer *eb = NULL;
1339         struct extent_buffer *eb_root;
1340         struct extent_buffer *old;
1341         struct tree_mod_root *old_root = NULL;
1342         u64 old_generation = 0;
1343         u64 logical;
1344         int level;
1345
1346         eb_root = btrfs_read_lock_root_node(root);
1347         tm = __tree_mod_log_oldest_root(eb_root, time_seq);
1348         if (!tm)
1349                 return eb_root;
1350
1351         if (tm->op == MOD_LOG_ROOT_REPLACE) {
1352                 old_root = &tm->old_root;
1353                 old_generation = tm->generation;
1354                 logical = old_root->logical;
1355                 level = old_root->level;
1356         } else {
1357                 logical = eb_root->start;
1358                 level = btrfs_header_level(eb_root);
1359         }
1360
1361         tm = tree_mod_log_search(fs_info, logical, time_seq);
1362         if (old_root && tm && tm->op != MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
1363                 btrfs_tree_read_unlock(eb_root);
1364                 free_extent_buffer(eb_root);
1365                 old = read_tree_block(fs_info, logical, 0, level, NULL);
1366                 if (WARN_ON(IS_ERR(old) || !extent_buffer_uptodate(old))) {
1367                         if (!IS_ERR(old))
1368                                 free_extent_buffer(old);
1369                         btrfs_warn(fs_info,
1370                                    "failed to read tree block %llu from get_old_root",
1371                                    logical);
1372                 } else {
1373                         eb = btrfs_clone_extent_buffer(old);
1374                         free_extent_buffer(old);
1375                 }
1376         } else if (old_root) {
1377                 btrfs_tree_read_unlock(eb_root);
1378                 free_extent_buffer(eb_root);
1379                 eb = alloc_dummy_extent_buffer(fs_info, logical);
1380         } else {
1381                 btrfs_set_lock_blocking_rw(eb_root, BTRFS_READ_LOCK);
1382                 eb = btrfs_clone_extent_buffer(eb_root);
1383                 btrfs_tree_read_unlock_blocking(eb_root);
1384                 free_extent_buffer(eb_root);
1385         }
1386
1387         if (!eb)
1388                 return NULL;
1389         btrfs_tree_read_lock(eb);
1390         if (old_root) {
1391                 btrfs_set_header_bytenr(eb, eb->start);
1392                 btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV);
1393                 btrfs_set_header_owner(eb, btrfs_header_owner(eb_root));
1394                 btrfs_set_header_level(eb, old_root->level);
1395                 btrfs_set_header_generation(eb, old_generation);
1396         }
1397         if (tm)
1398                 __tree_mod_log_rewind(fs_info, eb, time_seq, tm);
1399         else
1400                 WARN_ON(btrfs_header_level(eb) != 0);
1401         WARN_ON(btrfs_header_nritems(eb) > BTRFS_NODEPTRS_PER_BLOCK(fs_info));
1402
1403         return eb;
1404 }
1405
1406 int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
1407 {
1408         struct tree_mod_elem *tm;
1409         int level;
1410         struct extent_buffer *eb_root = btrfs_root_node(root);
1411
1412         tm = __tree_mod_log_oldest_root(eb_root, time_seq);
1413         if (tm && tm->op == MOD_LOG_ROOT_REPLACE) {
1414                 level = tm->old_root.level;
1415         } else {
1416                 level = btrfs_header_level(eb_root);
1417         }
1418         free_extent_buffer(eb_root);
1419
1420         return level;
1421 }
1422
1423 static inline int should_cow_block(struct btrfs_trans_handle *trans,
1424                                    struct btrfs_root *root,
1425                                    struct extent_buffer *buf)
1426 {
1427         if (btrfs_is_testing(root->fs_info))
1428                 return 0;
1429
1430         /* Ensure we can see the FORCE_COW bit */
1431         smp_mb__before_atomic();
1432
1433         /*
1434          * We do not need to cow a block if
1435          * 1) this block is not created or changed in this transaction;
1436          * 2) this block does not belong to TREE_RELOC tree;
1437          * 3) the root is not forced COW.
1438          *
1439          * What is forced COW:
1440          *    when we create snapshot during committing the transaction,
1441          *    after we've finished copying src root, we must COW the shared
1442          *    block to ensure the metadata consistency.
1443          */
1444         if (btrfs_header_generation(buf) == trans->transid &&
1445             !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN) &&
1446             !(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID &&
1447               btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)) &&
1448             !test_bit(BTRFS_ROOT_FORCE_COW, &root->state))
1449                 return 0;
1450         return 1;
1451 }
1452
1453 /*
1454  * cows a single block, see __btrfs_cow_block for the real work.
1455  * This version of it has extra checks so that a block isn't COWed more than
1456  * once per transaction, as long as it hasn't been written yet
1457  */
1458 noinline int btrfs_cow_block(struct btrfs_trans_handle *trans,
1459                     struct btrfs_root *root, struct extent_buffer *buf,
1460                     struct extent_buffer *parent, int parent_slot,
1461                     struct extent_buffer **cow_ret)
1462 {
1463         struct btrfs_fs_info *fs_info = root->fs_info;
1464         u64 search_start;
1465         int ret;
1466
1467         if (test_bit(BTRFS_ROOT_DELETING, &root->state))
1468                 btrfs_err(fs_info,
1469                         "COW'ing blocks on a fs root that's being dropped");
1470
1471         if (trans->transaction != fs_info->running_transaction)
1472                 WARN(1, KERN_CRIT "trans %llu running %llu\n",
1473                        trans->transid,
1474                        fs_info->running_transaction->transid);
1475
1476         if (trans->transid != fs_info->generation)
1477                 WARN(1, KERN_CRIT "trans %llu running %llu\n",
1478                        trans->transid, fs_info->generation);
1479
1480         if (!should_cow_block(trans, root, buf)) {
1481                 trans->dirty = true;
1482                 *cow_ret = buf;
1483                 return 0;
1484         }
1485
1486         search_start = buf->start & ~((u64)SZ_1G - 1);
1487
1488         if (parent)
1489                 btrfs_set_lock_blocking(parent);
1490         btrfs_set_lock_blocking(buf);
1491
1492         ret = __btrfs_cow_block(trans, root, buf, parent,
1493                                  parent_slot, cow_ret, search_start, 0);
1494
1495         trace_btrfs_cow_block(root, buf, *cow_ret);
1496
1497         return ret;
1498 }
1499
1500 /*
1501  * helper function for defrag to decide if two blocks pointed to by a
1502  * node are actually close by
1503  */
1504 static int close_blocks(u64 blocknr, u64 other, u32 blocksize)
1505 {
1506         if (blocknr < other && other - (blocknr + blocksize) < 32768)
1507                 return 1;
1508         if (blocknr > other && blocknr - (other + blocksize) < 32768)
1509                 return 1;
1510         return 0;
1511 }
1512
1513 /*
1514  * compare two keys in a memcmp fashion
1515  */
1516 static int comp_keys(const struct btrfs_disk_key *disk,
1517                      const struct btrfs_key *k2)
1518 {
1519         struct btrfs_key k1;
1520
1521         btrfs_disk_key_to_cpu(&k1, disk);
1522
1523         return btrfs_comp_cpu_keys(&k1, k2);
1524 }
1525
1526 /*
1527  * same as comp_keys only with two btrfs_key's
1528  */
1529 int btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2)
1530 {
1531         if (k1->objectid > k2->objectid)
1532                 return 1;
1533         if (k1->objectid < k2->objectid)
1534                 return -1;
1535         if (k1->type > k2->type)
1536                 return 1;
1537         if (k1->type < k2->type)
1538                 return -1;
1539         if (k1->offset > k2->offset)
1540                 return 1;
1541         if (k1->offset < k2->offset)
1542                 return -1;
1543         return 0;
1544 }
1545
1546 /*
1547  * this is used by the defrag code to go through all the
1548  * leaves pointed to by a node and reallocate them so that
1549  * disk order is close to key order
1550  */
1551 int btrfs_realloc_node(struct btrfs_trans_handle *trans,
1552                        struct btrfs_root *root, struct extent_buffer *parent,
1553                        int start_slot, u64 *last_ret,
1554                        struct btrfs_key *progress)
1555 {
1556         struct btrfs_fs_info *fs_info = root->fs_info;
1557         struct extent_buffer *cur;
1558         u64 blocknr;
1559         u64 gen;
1560         u64 search_start = *last_ret;
1561         u64 last_block = 0;
1562         u64 other;
1563         u32 parent_nritems;
1564         int end_slot;
1565         int i;
1566         int err = 0;
1567         int parent_level;
1568         int uptodate;
1569         u32 blocksize;
1570         int progress_passed = 0;
1571         struct btrfs_disk_key disk_key;
1572
1573         parent_level = btrfs_header_level(parent);
1574
1575         WARN_ON(trans->transaction != fs_info->running_transaction);
1576         WARN_ON(trans->transid != fs_info->generation);
1577
1578         parent_nritems = btrfs_header_nritems(parent);
1579         blocksize = fs_info->nodesize;
1580         end_slot = parent_nritems - 1;
1581
1582         if (parent_nritems <= 1)
1583                 return 0;
1584
1585         btrfs_set_lock_blocking(parent);
1586
1587         for (i = start_slot; i <= end_slot; i++) {
1588                 struct btrfs_key first_key;
1589                 int close = 1;
1590
1591                 btrfs_node_key(parent, &disk_key, i);
1592                 if (!progress_passed && comp_keys(&disk_key, progress) < 0)
1593                         continue;
1594
1595                 progress_passed = 1;
1596                 blocknr = btrfs_node_blockptr(parent, i);
1597                 gen = btrfs_node_ptr_generation(parent, i);
1598                 btrfs_node_key_to_cpu(parent, &first_key, i);
1599                 if (last_block == 0)
1600                         last_block = blocknr;
1601
1602                 if (i > 0) {
1603                         other = btrfs_node_blockptr(parent, i - 1);
1604                         close = close_blocks(blocknr, other, blocksize);
1605                 }
1606                 if (!close && i < end_slot) {
1607                         other = btrfs_node_blockptr(parent, i + 1);
1608                         close = close_blocks(blocknr, other, blocksize);
1609                 }
1610                 if (close) {
1611                         last_block = blocknr;
1612                         continue;
1613                 }
1614
1615                 cur = find_extent_buffer(fs_info, blocknr);
1616                 if (cur)
1617                         uptodate = btrfs_buffer_uptodate(cur, gen, 0);
1618                 else
1619                         uptodate = 0;
1620                 if (!cur || !uptodate) {
1621                         if (!cur) {
1622                                 cur = read_tree_block(fs_info, blocknr, gen,
1623                                                       parent_level - 1,
1624                                                       &first_key);
1625                                 if (IS_ERR(cur)) {
1626                                         return PTR_ERR(cur);
1627                                 } else if (!extent_buffer_uptodate(cur)) {
1628                                         free_extent_buffer(cur);
1629                                         return -EIO;
1630                                 }
1631                         } else if (!uptodate) {
1632                                 err = btrfs_read_buffer(cur, gen,
1633                                                 parent_level - 1,&first_key);
1634                                 if (err) {
1635                                         free_extent_buffer(cur);
1636                                         return err;
1637                                 }
1638                         }
1639                 }
1640                 if (search_start == 0)
1641                         search_start = last_block;
1642
1643                 btrfs_tree_lock(cur);
1644                 btrfs_set_lock_blocking(cur);
1645                 err = __btrfs_cow_block(trans, root, cur, parent, i,
1646                                         &cur, search_start,
1647                                         min(16 * blocksize,
1648                                             (end_slot - i) * blocksize));
1649                 if (err) {
1650                         btrfs_tree_unlock(cur);
1651                         free_extent_buffer(cur);
1652                         break;
1653                 }
1654                 search_start = cur->start;
1655                 last_block = cur->start;
1656                 *last_ret = search_start;
1657                 btrfs_tree_unlock(cur);
1658                 free_extent_buffer(cur);
1659         }
1660         return err;
1661 }
1662
1663 /*
1664  * search for key in the extent_buffer.  The items start at offset p,
1665  * and they are item_size apart.  There are 'max' items in p.
1666  *
1667  * the slot in the array is returned via slot, and it points to
1668  * the place where you would insert key if it is not found in
1669  * the array.
1670  *
1671  * slot may point to max if the key is bigger than all of the keys
1672  */
1673 static noinline int generic_bin_search(struct extent_buffer *eb,
1674                                        unsigned long p, int item_size,
1675                                        const struct btrfs_key *key,
1676                                        int max, int *slot)
1677 {
1678         int low = 0;
1679         int high = max;
1680         int mid;
1681         int ret;
1682         struct btrfs_disk_key *tmp = NULL;
1683         struct btrfs_disk_key unaligned;
1684         unsigned long offset;
1685         char *kaddr = NULL;
1686         unsigned long map_start = 0;
1687         unsigned long map_len = 0;
1688         int err;
1689
1690         if (low > high) {
1691                 btrfs_err(eb->fs_info,
1692                  "%s: low (%d) > high (%d) eb %llu owner %llu level %d",
1693                           __func__, low, high, eb->start,
1694                           btrfs_header_owner(eb), btrfs_header_level(eb));
1695                 return -EINVAL;
1696         }
1697
1698         while (low < high) {
1699                 mid = (low + high) / 2;
1700                 offset = p + mid * item_size;
1701
1702                 if (!kaddr || offset < map_start ||
1703                     (offset + sizeof(struct btrfs_disk_key)) >
1704                     map_start + map_len) {
1705
1706                         err = map_private_extent_buffer(eb, offset,
1707                                                 sizeof(struct btrfs_disk_key),
1708                                                 &kaddr, &map_start, &map_len);
1709
1710                         if (!err) {
1711                                 tmp = (struct btrfs_disk_key *)(kaddr + offset -
1712                                                         map_start);
1713                         } else if (err == 1) {
1714                                 read_extent_buffer(eb, &unaligned,
1715                                                    offset, sizeof(unaligned));
1716                                 tmp = &unaligned;
1717                         } else {
1718                                 return err;
1719                         }
1720
1721                 } else {
1722                         tmp = (struct btrfs_disk_key *)(kaddr + offset -
1723                                                         map_start);
1724                 }
1725                 ret = comp_keys(tmp, key);
1726
1727                 if (ret < 0)
1728                         low = mid + 1;
1729                 else if (ret > 0)
1730                         high = mid;
1731                 else {
1732                         *slot = mid;
1733                         return 0;
1734                 }
1735         }
1736         *slot = low;
1737         return 1;
1738 }
1739
1740 /*
1741  * simple bin_search frontend that does the right thing for
1742  * leaves vs nodes
1743  */
1744 int btrfs_bin_search(struct extent_buffer *eb, const struct btrfs_key *key,
1745                      int level, int *slot)
1746 {
1747         if (level == 0)
1748                 return generic_bin_search(eb,
1749                                           offsetof(struct btrfs_leaf, items),
1750                                           sizeof(struct btrfs_item),
1751                                           key, btrfs_header_nritems(eb),
1752                                           slot);
1753         else
1754                 return generic_bin_search(eb,
1755                                           offsetof(struct btrfs_node, ptrs),
1756                                           sizeof(struct btrfs_key_ptr),
1757                                           key, btrfs_header_nritems(eb),
1758                                           slot);
1759 }
1760
1761 static void root_add_used(struct btrfs_root *root, u32 size)
1762 {
1763         spin_lock(&root->accounting_lock);
1764         btrfs_set_root_used(&root->root_item,
1765                             btrfs_root_used(&root->root_item) + size);
1766         spin_unlock(&root->accounting_lock);
1767 }
1768
1769 static void root_sub_used(struct btrfs_root *root, u32 size)
1770 {
1771         spin_lock(&root->accounting_lock);
1772         btrfs_set_root_used(&root->root_item,
1773                             btrfs_root_used(&root->root_item) - size);
1774         spin_unlock(&root->accounting_lock);
1775 }
1776
1777 /* given a node and slot number, this reads the blocks it points to.  The
1778  * extent buffer is returned with a reference taken (but unlocked).
1779  */
1780 static noinline struct extent_buffer *
1781 read_node_slot(struct btrfs_fs_info *fs_info, struct extent_buffer *parent,
1782                int slot)
1783 {
1784         int level = btrfs_header_level(parent);
1785         struct extent_buffer *eb;
1786         struct btrfs_key first_key;
1787
1788         if (slot < 0 || slot >= btrfs_header_nritems(parent))
1789                 return ERR_PTR(-ENOENT);
1790
1791         BUG_ON(level == 0);
1792
1793         btrfs_node_key_to_cpu(parent, &first_key, slot);
1794         eb = read_tree_block(fs_info, btrfs_node_blockptr(parent, slot),
1795                              btrfs_node_ptr_generation(parent, slot),
1796                              level - 1, &first_key);
1797         if (!IS_ERR(eb) && !extent_buffer_uptodate(eb)) {
1798                 free_extent_buffer(eb);
1799                 eb = ERR_PTR(-EIO);
1800         }
1801
1802         return eb;
1803 }
1804
1805 /*
1806  * node level balancing, used to make sure nodes are in proper order for
1807  * item deletion.  We balance from the top down, so we have to make sure
1808  * that a deletion won't leave an node completely empty later on.
1809  */
1810 static noinline int balance_level(struct btrfs_trans_handle *trans,
1811                          struct btrfs_root *root,
1812                          struct btrfs_path *path, int level)
1813 {
1814         struct btrfs_fs_info *fs_info = root->fs_info;
1815         struct extent_buffer *right = NULL;
1816         struct extent_buffer *mid;
1817         struct extent_buffer *left = NULL;
1818         struct extent_buffer *parent = NULL;
1819         int ret = 0;
1820         int wret;
1821         int pslot;
1822         int orig_slot = path->slots[level];
1823         u64 orig_ptr;
1824
1825         ASSERT(level > 0);
1826
1827         mid = path->nodes[level];
1828
1829         WARN_ON(path->locks[level] != BTRFS_WRITE_LOCK &&
1830                 path->locks[level] != BTRFS_WRITE_LOCK_BLOCKING);
1831         WARN_ON(btrfs_header_generation(mid) != trans->transid);
1832
1833         orig_ptr = btrfs_node_blockptr(mid, orig_slot);
1834
1835         if (level < BTRFS_MAX_LEVEL - 1) {
1836                 parent = path->nodes[level + 1];
1837                 pslot = path->slots[level + 1];
1838         }
1839
1840         /*
1841          * deal with the case where there is only one pointer in the root
1842          * by promoting the node below to a root
1843          */
1844         if (!parent) {
1845                 struct extent_buffer *child;
1846
1847                 if (btrfs_header_nritems(mid) != 1)
1848                         return 0;
1849
1850                 /* promote the child to a root */
1851                 child = read_node_slot(fs_info, mid, 0);
1852                 if (IS_ERR(child)) {
1853                         ret = PTR_ERR(child);
1854                         btrfs_handle_fs_error(fs_info, ret, NULL);
1855                         goto enospc;
1856                 }
1857
1858                 btrfs_tree_lock(child);
1859                 btrfs_set_lock_blocking(child);
1860                 ret = btrfs_cow_block(trans, root, child, mid, 0, &child);
1861                 if (ret) {
1862                         btrfs_tree_unlock(child);
1863                         free_extent_buffer(child);
1864                         goto enospc;
1865                 }
1866
1867                 ret = tree_mod_log_insert_root(root->node, child, 1);
1868                 BUG_ON(ret < 0);
1869                 rcu_assign_pointer(root->node, child);
1870
1871                 add_root_to_dirty_list(root);
1872                 btrfs_tree_unlock(child);
1873
1874                 path->locks[level] = 0;
1875                 path->nodes[level] = NULL;
1876                 clean_tree_block(fs_info, mid);
1877                 btrfs_tree_unlock(mid);
1878                 /* once for the path */
1879                 free_extent_buffer(mid);
1880
1881                 root_sub_used(root, mid->len);
1882                 btrfs_free_tree_block(trans, root, mid, 0, 1);
1883                 /* once for the root ptr */
1884                 free_extent_buffer_stale(mid);
1885                 return 0;
1886         }
1887         if (btrfs_header_nritems(mid) >
1888             BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4)
1889                 return 0;
1890
1891         left = read_node_slot(fs_info, parent, pslot - 1);
1892         if (IS_ERR(left))
1893                 left = NULL;
1894
1895         if (left) {
1896                 btrfs_tree_lock(left);
1897                 btrfs_set_lock_blocking(left);
1898                 wret = btrfs_cow_block(trans, root, left,
1899                                        parent, pslot - 1, &left);
1900                 if (wret) {
1901                         ret = wret;
1902                         goto enospc;
1903                 }
1904         }
1905
1906         right = read_node_slot(fs_info, parent, pslot + 1);
1907         if (IS_ERR(right))
1908                 right = NULL;
1909
1910         if (right) {
1911                 btrfs_tree_lock(right);
1912                 btrfs_set_lock_blocking(right);
1913                 wret = btrfs_cow_block(trans, root, right,
1914                                        parent, pslot + 1, &right);
1915                 if (wret) {
1916                         ret = wret;
1917                         goto enospc;
1918                 }
1919         }
1920
1921         /* first, try to make some room in the middle buffer */
1922         if (left) {
1923                 orig_slot += btrfs_header_nritems(left);
1924                 wret = push_node_left(trans, fs_info, left, mid, 1);
1925                 if (wret < 0)
1926                         ret = wret;
1927         }
1928
1929         /*
1930          * then try to empty the right most buffer into the middle
1931          */
1932         if (right) {
1933                 wret = push_node_left(trans, fs_info, mid, right, 1);
1934                 if (wret < 0 && wret != -ENOSPC)
1935                         ret = wret;
1936                 if (btrfs_header_nritems(right) == 0) {
1937                         clean_tree_block(fs_info, right);
1938                         btrfs_tree_unlock(right);
1939                         del_ptr(root, path, level + 1, pslot + 1);
1940                         root_sub_used(root, right->len);
1941                         btrfs_free_tree_block(trans, root, right, 0, 1);
1942                         free_extent_buffer_stale(right);
1943                         right = NULL;
1944                 } else {
1945                         struct btrfs_disk_key right_key;
1946                         btrfs_node_key(right, &right_key, 0);
1947                         ret = tree_mod_log_insert_key(parent, pslot + 1,
1948                                         MOD_LOG_KEY_REPLACE, GFP_NOFS);
1949                         BUG_ON(ret < 0);
1950                         btrfs_set_node_key(parent, &right_key, pslot + 1);
1951                         btrfs_mark_buffer_dirty(parent);
1952                 }
1953         }
1954         if (btrfs_header_nritems(mid) == 1) {
1955                 /*
1956                  * we're not allowed to leave a node with one item in the
1957                  * tree during a delete.  A deletion from lower in the tree
1958                  * could try to delete the only pointer in this node.
1959                  * So, pull some keys from the left.
1960                  * There has to be a left pointer at this point because
1961                  * otherwise we would have pulled some pointers from the
1962                  * right
1963                  */
1964                 if (!left) {
1965                         ret = -EROFS;
1966                         btrfs_handle_fs_error(fs_info, ret, NULL);
1967                         goto enospc;
1968                 }
1969                 wret = balance_node_right(trans, fs_info, mid, left);
1970                 if (wret < 0) {
1971                         ret = wret;
1972                         goto enospc;
1973                 }
1974                 if (wret == 1) {
1975                         wret = push_node_left(trans, fs_info, left, mid, 1);
1976                         if (wret < 0)
1977                                 ret = wret;
1978                 }
1979                 BUG_ON(wret == 1);
1980         }
1981         if (btrfs_header_nritems(mid) == 0) {
1982                 clean_tree_block(fs_info, mid);
1983                 btrfs_tree_unlock(mid);
1984                 del_ptr(root, path, level + 1, pslot);
1985                 root_sub_used(root, mid->len);
1986                 btrfs_free_tree_block(trans, root, mid, 0, 1);
1987                 free_extent_buffer_stale(mid);
1988                 mid = NULL;
1989         } else {
1990                 /* update the parent key to reflect our changes */
1991                 struct btrfs_disk_key mid_key;
1992                 btrfs_node_key(mid, &mid_key, 0);
1993                 ret = tree_mod_log_insert_key(parent, pslot,
1994                                 MOD_LOG_KEY_REPLACE, GFP_NOFS);
1995                 BUG_ON(ret < 0);
1996                 btrfs_set_node_key(parent, &mid_key, pslot);
1997                 btrfs_mark_buffer_dirty(parent);
1998         }
1999
2000         /* update the path */
2001         if (left) {
2002                 if (btrfs_header_nritems(left) > orig_slot) {
2003                         extent_buffer_get(left);
2004                         /* left was locked after cow */
2005                         path->nodes[level] = left;
2006                         path->slots[level + 1] -= 1;
2007                         path->slots[level] = orig_slot;
2008                         if (mid) {
2009                                 btrfs_tree_unlock(mid);
2010                                 free_extent_buffer(mid);
2011                         }
2012                 } else {
2013                         orig_slot -= btrfs_header_nritems(left);
2014                         path->slots[level] = orig_slot;
2015                 }
2016         }
2017         /* double check we haven't messed things up */
2018         if (orig_ptr !=
2019             btrfs_node_blockptr(path->nodes[level], path->slots[level]))
2020                 BUG();
2021 enospc:
2022         if (right) {
2023                 btrfs_tree_unlock(right);
2024                 free_extent_buffer(right);
2025         }
2026         if (left) {
2027                 if (path->nodes[level] != left)
2028                         btrfs_tree_unlock(left);
2029                 free_extent_buffer(left);
2030         }
2031         return ret;
2032 }
2033
2034 /* Node balancing for insertion.  Here we only split or push nodes around
2035  * when they are completely full.  This is also done top down, so we
2036  * have to be pessimistic.
2037  */
2038 static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
2039                                           struct btrfs_root *root,
2040                                           struct btrfs_path *path, int level)
2041 {
2042         struct btrfs_fs_info *fs_info = root->fs_info;
2043         struct extent_buffer *right = NULL;
2044         struct extent_buffer *mid;
2045         struct extent_buffer *left = NULL;
2046         struct extent_buffer *parent = NULL;
2047         int ret = 0;
2048         int wret;
2049         int pslot;
2050         int orig_slot = path->slots[level];
2051
2052         if (level == 0)
2053                 return 1;
2054
2055         mid = path->nodes[level];
2056         WARN_ON(btrfs_header_generation(mid) != trans->transid);
2057
2058         if (level < BTRFS_MAX_LEVEL - 1) {
2059                 parent = path->nodes[level + 1];
2060                 pslot = path->slots[level + 1];
2061         }
2062
2063         if (!parent)
2064                 return 1;
2065
2066         left = read_node_slot(fs_info, parent, pslot - 1);
2067         if (IS_ERR(left))
2068                 left = NULL;
2069
2070         /* first, try to make some room in the middle buffer */
2071         if (left) {
2072                 u32 left_nr;
2073
2074                 btrfs_tree_lock(left);
2075                 btrfs_set_lock_blocking(left);
2076
2077                 left_nr = btrfs_header_nritems(left);
2078                 if (left_nr >= BTRFS_NODEPTRS_PER_BLOCK(fs_info) - 1) {
2079                         wret = 1;
2080                 } else {
2081                         ret = btrfs_cow_block(trans, root, left, parent,
2082                                               pslot - 1, &left);
2083                         if (ret)
2084                                 wret = 1;
2085                         else {
2086                                 wret = push_node_left(trans, fs_info,
2087                                                       left, mid, 0);
2088                         }
2089                 }
2090                 if (wret < 0)
2091                         ret = wret;
2092                 if (wret == 0) {
2093                         struct btrfs_disk_key disk_key;
2094                         orig_slot += left_nr;
2095                         btrfs_node_key(mid, &disk_key, 0);
2096                         ret = tree_mod_log_insert_key(parent, pslot,
2097                                         MOD_LOG_KEY_REPLACE, GFP_NOFS);
2098                         BUG_ON(ret < 0);
2099                         btrfs_set_node_key(parent, &disk_key, pslot);
2100                         btrfs_mark_buffer_dirty(parent);
2101                         if (btrfs_header_nritems(left) > orig_slot) {
2102                                 path->nodes[level] = left;
2103                                 path->slots[level + 1] -= 1;
2104                                 path->slots[level] = orig_slot;
2105                                 btrfs_tree_unlock(mid);
2106                                 free_extent_buffer(mid);
2107                         } else {
2108                                 orig_slot -=
2109                                         btrfs_header_nritems(left);
2110                                 path->slots[level] = orig_slot;
2111                                 btrfs_tree_unlock(left);
2112                                 free_extent_buffer(left);
2113                         }
2114                         return 0;
2115                 }
2116                 btrfs_tree_unlock(left);
2117                 free_extent_buffer(left);
2118         }
2119         right = read_node_slot(fs_info, parent, pslot + 1);
2120         if (IS_ERR(right))
2121                 right = NULL;
2122
2123         /*
2124          * then try to empty the right most buffer into the middle
2125          */
2126         if (right) {
2127                 u32 right_nr;
2128
2129                 btrfs_tree_lock(right);
2130                 btrfs_set_lock_blocking(right);
2131
2132                 right_nr = btrfs_header_nritems(right);
2133                 if (right_nr >= BTRFS_NODEPTRS_PER_BLOCK(fs_info) - 1) {
2134                         wret = 1;
2135                 } else {
2136                         ret = btrfs_cow_block(trans, root, right,
2137                                               parent, pslot + 1,
2138                                               &right);
2139                         if (ret)
2140                                 wret = 1;
2141                         else {
2142                                 wret = balance_node_right(trans, fs_info,
2143                                                           right, mid);
2144                         }
2145                 }
2146                 if (wret < 0)
2147                         ret = wret;
2148                 if (wret == 0) {
2149                         struct btrfs_disk_key disk_key;
2150
2151                         btrfs_node_key(right, &disk_key, 0);
2152                         ret = tree_mod_log_insert_key(parent, pslot + 1,
2153                                         MOD_LOG_KEY_REPLACE, GFP_NOFS);
2154                         BUG_ON(ret < 0);
2155                         btrfs_set_node_key(parent, &disk_key, pslot + 1);
2156                         btrfs_mark_buffer_dirty(parent);
2157
2158                         if (btrfs_header_nritems(mid) <= orig_slot) {
2159                                 path->nodes[level] = right;
2160                                 path->slots[level + 1] += 1;
2161                                 path->slots[level] = orig_slot -
2162                                         btrfs_header_nritems(mid);
2163                                 btrfs_tree_unlock(mid);
2164                                 free_extent_buffer(mid);
2165                         } else {
2166                                 btrfs_tree_unlock(right);
2167                                 free_extent_buffer(right);
2168                         }
2169                         return 0;
2170                 }
2171                 btrfs_tree_unlock(right);
2172                 free_extent_buffer(right);
2173         }
2174         return 1;
2175 }
2176
2177 /*
2178  * readahead one full node of leaves, finding things that are close
2179  * to the block in 'slot', and triggering ra on them.
2180  */
2181 static void reada_for_search(struct btrfs_fs_info *fs_info,
2182                              struct btrfs_path *path,
2183                              int level, int slot, u64 objectid)
2184 {
2185         struct extent_buffer *node;
2186         struct btrfs_disk_key disk_key;
2187         u32 nritems;
2188         u64 search;
2189         u64 target;
2190         u64 nread = 0;
2191         struct extent_buffer *eb;
2192         u32 nr;
2193         u32 blocksize;
2194         u32 nscan = 0;
2195
2196         if (level != 1)
2197                 return;
2198
2199         if (!path->nodes[level])
2200                 return;
2201
2202         node = path->nodes[level];
2203
2204         search = btrfs_node_blockptr(node, slot);
2205         blocksize = fs_info->nodesize;
2206         eb = find_extent_buffer(fs_info, search);
2207         if (eb) {
2208                 free_extent_buffer(eb);
2209                 return;
2210         }
2211
2212         target = search;
2213
2214         nritems = btrfs_header_nritems(node);
2215         nr = slot;
2216
2217         while (1) {
2218                 if (path->reada == READA_BACK) {
2219                         if (nr == 0)
2220                                 break;
2221                         nr--;
2222                 } else if (path->reada == READA_FORWARD) {
2223                         nr++;
2224                         if (nr >= nritems)
2225                                 break;
2226                 }
2227                 if (path->reada == READA_BACK && objectid) {
2228                         btrfs_node_key(node, &disk_key, nr);
2229                         if (btrfs_disk_key_objectid(&disk_key) != objectid)
2230                                 break;
2231                 }
2232                 search = btrfs_node_blockptr(node, nr);
2233                 if ((search <= target && target - search <= 65536) ||
2234                     (search > target && search - target <= 65536)) {
2235                         readahead_tree_block(fs_info, search);
2236                         nread += blocksize;
2237                 }
2238                 nscan++;
2239                 if ((nread > 65536 || nscan > 32))
2240                         break;
2241         }
2242 }
2243
2244 static noinline void reada_for_balance(struct btrfs_fs_info *fs_info,
2245                                        struct btrfs_path *path, int level)
2246 {
2247         int slot;
2248         int nritems;
2249         struct extent_buffer *parent;
2250         struct extent_buffer *eb;
2251         u64 gen;
2252         u64 block1 = 0;
2253         u64 block2 = 0;
2254
2255         parent = path->nodes[level + 1];
2256         if (!parent)
2257                 return;
2258
2259         nritems = btrfs_header_nritems(parent);
2260         slot = path->slots[level + 1];
2261
2262         if (slot > 0) {
2263                 block1 = btrfs_node_blockptr(parent, slot - 1);
2264                 gen = btrfs_node_ptr_generation(parent, slot - 1);
2265                 eb = find_extent_buffer(fs_info, block1);
2266                 /*
2267                  * if we get -eagain from btrfs_buffer_uptodate, we
2268                  * don't want to return eagain here.  That will loop
2269                  * forever
2270                  */
2271                 if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0)
2272                         block1 = 0;
2273                 free_extent_buffer(eb);
2274         }
2275         if (slot + 1 < nritems) {
2276                 block2 = btrfs_node_blockptr(parent, slot + 1);
2277                 gen = btrfs_node_ptr_generation(parent, slot + 1);
2278                 eb = find_extent_buffer(fs_info, block2);
2279                 if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0)
2280                         block2 = 0;
2281                 free_extent_buffer(eb);
2282         }
2283
2284         if (block1)
2285                 readahead_tree_block(fs_info, block1);
2286         if (block2)
2287                 readahead_tree_block(fs_info, block2);
2288 }
2289
2290
2291 /*
2292  * when we walk down the tree, it is usually safe to unlock the higher layers
2293  * in the tree.  The exceptions are when our path goes through slot 0, because
2294  * operations on the tree might require changing key pointers higher up in the
2295  * tree.
2296  *
2297  * callers might also have set path->keep_locks, which tells this code to keep
2298  * the lock if the path points to the last slot in the block.  This is part of
2299  * walking through the tree, and selecting the next slot in the higher block.
2300  *
2301  * lowest_unlock sets the lowest level in the tree we're allowed to unlock.  so
2302  * if lowest_unlock is 1, level 0 won't be unlocked
2303  */
2304 static noinline void unlock_up(struct btrfs_path *path, int level,
2305                                int lowest_unlock, int min_write_lock_level,
2306                                int *write_lock_level)
2307 {
2308         int i;
2309         int skip_level = level;
2310         int no_skips = 0;
2311         struct extent_buffer *t;
2312
2313         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
2314                 if (!path->nodes[i])
2315                         break;
2316                 if (!path->locks[i])
2317                         break;
2318                 if (!no_skips && path->slots[i] == 0) {
2319                         skip_level = i + 1;
2320                         continue;
2321                 }
2322                 if (!no_skips && path->keep_locks) {
2323                         u32 nritems;
2324                         t = path->nodes[i];
2325                         nritems = btrfs_header_nritems(t);
2326                         if (nritems < 1 || path->slots[i] >= nritems - 1) {
2327                                 skip_level = i + 1;
2328                                 continue;
2329                         }
2330                 }
2331                 if (skip_level < i && i >= lowest_unlock)
2332                         no_skips = 1;
2333
2334                 t = path->nodes[i];
2335                 if (i >= lowest_unlock && i > skip_level) {
2336                         btrfs_tree_unlock_rw(t, path->locks[i]);
2337                         path->locks[i] = 0;
2338                         if (write_lock_level &&
2339                             i > min_write_lock_level &&
2340                             i <= *write_lock_level) {
2341                                 *write_lock_level = i - 1;
2342                         }
2343                 }
2344         }
2345 }
2346
2347 /*
2348  * This releases any locks held in the path starting at level and
2349  * going all the way up to the root.
2350  *
2351  * btrfs_search_slot will keep the lock held on higher nodes in a few
2352  * corner cases, such as COW of the block at slot zero in the node.  This
2353  * ignores those rules, and it should only be called when there are no
2354  * more updates to be done higher up in the tree.
2355  */
2356 noinline void btrfs_unlock_up_safe(struct btrfs_path *path, int level)
2357 {
2358         int i;
2359
2360         if (path->keep_locks)
2361                 return;
2362
2363         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
2364                 if (!path->nodes[i])
2365                         continue;
2366                 if (!path->locks[i])
2367                         continue;
2368                 btrfs_tree_unlock_rw(path->nodes[i], path->locks[i]);
2369                 path->locks[i] = 0;
2370         }
2371 }
2372
2373 /*
2374  * helper function for btrfs_search_slot.  The goal is to find a block
2375  * in cache without setting the path to blocking.  If we find the block
2376  * we return zero and the path is unchanged.
2377  *
2378  * If we can't find the block, we set the path blocking and do some
2379  * reada.  -EAGAIN is returned and the search must be repeated.
2380  */
2381 static int
2382 read_block_for_search(struct btrfs_root *root, struct btrfs_path *p,
2383                       struct extent_buffer **eb_ret, int level, int slot,
2384                       const struct btrfs_key *key)
2385 {
2386         struct btrfs_fs_info *fs_info = root->fs_info;
2387         u64 blocknr;
2388         u64 gen;
2389         struct extent_buffer *b = *eb_ret;
2390         struct extent_buffer *tmp;
2391         struct btrfs_key first_key;
2392         int ret;
2393         int parent_level;
2394
2395         blocknr = btrfs_node_blockptr(b, slot);
2396         gen = btrfs_node_ptr_generation(b, slot);
2397         parent_level = btrfs_header_level(b);
2398         btrfs_node_key_to_cpu(b, &first_key, slot);
2399
2400         tmp = find_extent_buffer(fs_info, blocknr);
2401         if (tmp) {
2402                 /* first we do an atomic uptodate check */
2403                 if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {
2404                         *eb_ret = tmp;
2405                         return 0;
2406                 }
2407
2408                 /* the pages were up to date, but we failed
2409                  * the generation number check.  Do a full
2410                  * read for the generation number that is correct.
2411                  * We must do this without dropping locks so
2412                  * we can trust our generation number
2413                  */
2414                 btrfs_set_path_blocking(p);
2415
2416                 /* now we're allowed to do a blocking uptodate check */
2417                 ret = btrfs_read_buffer(tmp, gen, parent_level - 1, &first_key);
2418                 if (!ret) {
2419                         *eb_ret = tmp;
2420                         return 0;
2421                 }
2422                 free_extent_buffer(tmp);
2423                 btrfs_release_path(p);
2424                 return -EIO;
2425         }
2426
2427         /*
2428          * reduce lock contention at high levels
2429          * of the btree by dropping locks before
2430          * we read.  Don't release the lock on the current
2431          * level because we need to walk this node to figure
2432          * out which blocks to read.
2433          */
2434         btrfs_unlock_up_safe(p, level + 1);
2435         btrfs_set_path_blocking(p);
2436
2437         if (p->reada != READA_NONE)
2438                 reada_for_search(fs_info, p, level, slot, key->objectid);
2439
2440         ret = -EAGAIN;
2441         tmp = read_tree_block(fs_info, blocknr, gen, parent_level - 1,
2442                               &first_key);
2443         if (!IS_ERR(tmp)) {
2444                 /*
2445                  * If the read above didn't mark this buffer up to date,
2446                  * it will never end up being up to date.  Set ret to EIO now
2447                  * and give up so that our caller doesn't loop forever
2448                  * on our EAGAINs.
2449                  */
2450                 if (!extent_buffer_uptodate(tmp))
2451                         ret = -EIO;
2452                 free_extent_buffer(tmp);
2453         } else {
2454                 ret = PTR_ERR(tmp);
2455         }
2456
2457         btrfs_release_path(p);
2458         return ret;
2459 }
2460
2461 /*
2462  * helper function for btrfs_search_slot.  This does all of the checks
2463  * for node-level blocks and does any balancing required based on
2464  * the ins_len.
2465  *
2466  * If no extra work was required, zero is returned.  If we had to
2467  * drop the path, -EAGAIN is returned and btrfs_search_slot must
2468  * start over
2469  */
2470 static int
2471 setup_nodes_for_search(struct btrfs_trans_handle *trans,
2472                        struct btrfs_root *root, struct btrfs_path *p,
2473                        struct extent_buffer *b, int level, int ins_len,
2474                        int *write_lock_level)
2475 {
2476         struct btrfs_fs_info *fs_info = root->fs_info;
2477         int ret;
2478
2479         if ((p->search_for_split || ins_len > 0) && btrfs_header_nritems(b) >=
2480             BTRFS_NODEPTRS_PER_BLOCK(fs_info) - 3) {
2481                 int sret;
2482
2483                 if (*write_lock_level < level + 1) {
2484                         *write_lock_level = level + 1;
2485                         btrfs_release_path(p);
2486                         goto again;
2487                 }
2488
2489                 btrfs_set_path_blocking(p);
2490                 reada_for_balance(fs_info, p, level);
2491                 sret = split_node(trans, root, p, level);
2492
2493                 BUG_ON(sret > 0);
2494                 if (sret) {
2495                         ret = sret;
2496                         goto done;
2497                 }
2498                 b = p->nodes[level];
2499         } else if (ins_len < 0 && btrfs_header_nritems(b) <
2500                    BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 2) {
2501                 int sret;
2502
2503                 if (*write_lock_level < level + 1) {
2504                         *write_lock_level = level + 1;
2505                         btrfs_release_path(p);
2506                         goto again;
2507                 }
2508
2509                 btrfs_set_path_blocking(p);
2510                 reada_for_balance(fs_info, p, level);
2511                 sret = balance_level(trans, root, p, level);
2512
2513                 if (sret) {
2514                         ret = sret;
2515                         goto done;
2516                 }
2517                 b = p->nodes[level];
2518                 if (!b) {
2519                         btrfs_release_path(p);
2520                         goto again;
2521                 }
2522                 BUG_ON(btrfs_header_nritems(b) == 1);
2523         }
2524         return 0;
2525
2526 again:
2527         ret = -EAGAIN;
2528 done:
2529         return ret;
2530 }
2531
2532 static void key_search_validate(struct extent_buffer *b,
2533                                 const struct btrfs_key *key,
2534                                 int level)
2535 {
2536 #ifdef CONFIG_BTRFS_ASSERT
2537         struct btrfs_disk_key disk_key;
2538
2539         btrfs_cpu_key_to_disk(&disk_key, key);
2540
2541         if (level == 0)
2542                 ASSERT(!memcmp_extent_buffer(b, &disk_key,
2543                     offsetof(struct btrfs_leaf, items[0].key),
2544                     sizeof(disk_key)));
2545         else
2546                 ASSERT(!memcmp_extent_buffer(b, &disk_key,
2547                     offsetof(struct btrfs_node, ptrs[0].key),
2548                     sizeof(disk_key)));
2549 #endif
2550 }
2551
2552 static int key_search(struct extent_buffer *b, const struct btrfs_key *key,
2553                       int level, int *prev_cmp, int *slot)
2554 {
2555         if (*prev_cmp != 0) {
2556                 *prev_cmp = btrfs_bin_search(b, key, level, slot);
2557                 return *prev_cmp;
2558         }
2559
2560         key_search_validate(b, key, level);
2561         *slot = 0;
2562
2563         return 0;
2564 }
2565
2566 int btrfs_find_item(struct btrfs_root *fs_root, struct btrfs_path *path,
2567                 u64 iobjectid, u64 ioff, u8 key_type,
2568                 struct btrfs_key *found_key)
2569 {
2570         int ret;
2571         struct btrfs_key key;
2572         struct extent_buffer *eb;
2573
2574         ASSERT(path);
2575         ASSERT(found_key);
2576
2577         key.type = key_type;
2578         key.objectid = iobjectid;
2579         key.offset = ioff;
2580
2581         ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
2582         if (ret < 0)
2583                 return ret;
2584
2585         eb = path->nodes[0];
2586         if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
2587                 ret = btrfs_next_leaf(fs_root, path);
2588                 if (ret)
2589                         return ret;
2590                 eb = path->nodes[0];
2591         }
2592
2593         btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
2594         if (found_key->type != key.type ||
2595                         found_key->objectid != key.objectid)
2596                 return 1;
2597
2598         return 0;
2599 }
2600
2601 static struct extent_buffer *btrfs_search_slot_get_root(struct btrfs_root *root,
2602                                                         struct btrfs_path *p,
2603                                                         int write_lock_level)
2604 {
2605         struct btrfs_fs_info *fs_info = root->fs_info;
2606         struct extent_buffer *b;
2607         int root_lock;
2608         int level = 0;
2609
2610         /* We try very hard to do read locks on the root */
2611         root_lock = BTRFS_READ_LOCK;
2612
2613         if (p->search_commit_root) {
2614                 /*
2615                  * The commit roots are read only so we always do read locks,
2616                  * and we always must hold the commit_root_sem when doing
2617                  * searches on them, the only exception is send where we don't
2618                  * want to block transaction commits for a long time, so
2619                  * we need to clone the commit root in order to avoid races
2620                  * with transaction commits that create a snapshot of one of
2621                  * the roots used by a send operation.
2622                  */
2623                 if (p->need_commit_sem) {
2624                         down_read(&fs_info->commit_root_sem);
2625                         b = btrfs_clone_extent_buffer(root->commit_root);
2626                         up_read(&fs_info->commit_root_sem);
2627                         if (!b)
2628                                 return ERR_PTR(-ENOMEM);
2629
2630                 } else {
2631                         b = root->commit_root;
2632                         extent_buffer_get(b);
2633                 }
2634                 level = btrfs_header_level(b);
2635                 /*
2636                  * Ensure that all callers have set skip_locking when
2637                  * p->search_commit_root = 1.
2638                  */
2639                 ASSERT(p->skip_locking == 1);
2640
2641                 goto out;
2642         }
2643
2644         if (p->skip_locking) {
2645                 b = btrfs_root_node(root);
2646                 level = btrfs_header_level(b);
2647                 goto out;
2648         }
2649
2650         /*
2651          * If the level is set to maximum, we can skip trying to get the read
2652          * lock.
2653          */
2654         if (write_lock_level < BTRFS_MAX_LEVEL) {
2655                 /*
2656                  * We don't know the level of the root node until we actually
2657                  * have it read locked
2658                  */
2659                 b = btrfs_read_lock_root_node(root);
2660                 level = btrfs_header_level(b);
2661                 if (level > write_lock_level)
2662                         goto out;
2663
2664                 /* Whoops, must trade for write lock */
2665                 btrfs_tree_read_unlock(b);
2666                 free_extent_buffer(b);
2667         }
2668
2669         b = btrfs_lock_root_node(root);
2670         root_lock = BTRFS_WRITE_LOCK;
2671
2672         /* The level might have changed, check again */
2673         level = btrfs_header_level(b);
2674
2675 out:
2676         p->nodes[level] = b;
2677         if (!p->skip_locking)
2678                 p->locks[level] = root_lock;
2679         /*
2680          * Callers are responsible for dropping b's references.
2681          */
2682         return b;
2683 }
2684
2685
2686 /*
2687  * btrfs_search_slot - look for a key in a tree and perform necessary
2688  * modifications to preserve tree invariants.
2689  *
2690  * @trans:      Handle of transaction, used when modifying the tree
2691  * @p:          Holds all btree nodes along the search path
2692  * @root:       The root node of the tree
2693  * @key:        The key we are looking for
2694  * @ins_len:    Indicates purpose of search, for inserts it is 1, for
2695  *              deletions it's -1. 0 for plain searches
2696  * @cow:        boolean should CoW operations be performed. Must always be 1
2697  *              when modifying the tree.
2698  *
2699  * If @ins_len > 0, nodes and leaves will be split as we walk down the tree.
2700  * If @ins_len < 0, nodes will be merged as we walk down the tree (if possible)
2701  *
2702  * If @key is found, 0 is returned and you can find the item in the leaf level
2703  * of the path (level 0)
2704  *
2705  * If @key isn't found, 1 is returned and the leaf level of the path (level 0)
2706  * points to the slot where it should be inserted
2707  *
2708  * If an error is encountered while searching the tree a negative error number
2709  * is returned
2710  */
2711 int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root,
2712                       const struct btrfs_key *key, struct btrfs_path *p,
2713                       int ins_len, int cow)
2714 {
2715         struct btrfs_fs_info *fs_info = root->fs_info;
2716         struct extent_buffer *b;
2717         int slot;
2718         int ret;
2719         int err;
2720         int level;
2721         int lowest_unlock = 1;
2722         /* everything at write_lock_level or lower must be write locked */
2723         int write_lock_level = 0;
2724         u8 lowest_level = 0;
2725         int min_write_lock_level;
2726         int prev_cmp;
2727
2728         lowest_level = p->lowest_level;
2729         WARN_ON(lowest_level && ins_len > 0);
2730         WARN_ON(p->nodes[0] != NULL);
2731         BUG_ON(!cow && ins_len);
2732
2733         if (ins_len < 0) {
2734                 lowest_unlock = 2;
2735
2736                 /* when we are removing items, we might have to go up to level
2737                  * two as we update tree pointers  Make sure we keep write
2738                  * for those levels as well
2739                  */
2740                 write_lock_level = 2;
2741         } else if (ins_len > 0) {
2742                 /*
2743                  * for inserting items, make sure we have a write lock on
2744                  * level 1 so we can update keys
2745                  */
2746                 write_lock_level = 1;
2747         }
2748
2749         if (!cow)
2750                 write_lock_level = -1;
2751
2752         if (cow && (p->keep_locks || p->lowest_level))
2753                 write_lock_level = BTRFS_MAX_LEVEL;
2754
2755         min_write_lock_level = write_lock_level;
2756
2757 again:
2758         prev_cmp = -1;
2759         b = btrfs_search_slot_get_root(root, p, write_lock_level);
2760         if (IS_ERR(b)) {
2761                 ret = PTR_ERR(b);
2762                 goto done;
2763         }
2764
2765         while (b) {
2766                 level = btrfs_header_level(b);
2767
2768                 /*
2769                  * setup the path here so we can release it under lock
2770                  * contention with the cow code
2771                  */
2772                 if (cow) {
2773                         bool last_level = (level == (BTRFS_MAX_LEVEL - 1));
2774
2775                         /*
2776                          * if we don't really need to cow this block
2777                          * then we don't want to set the path blocking,
2778                          * so we test it here
2779                          */
2780                         if (!should_cow_block(trans, root, b)) {
2781                                 trans->dirty = true;
2782                                 goto cow_done;
2783                         }
2784
2785                         /*
2786                          * must have write locks on this node and the
2787                          * parent
2788                          */
2789                         if (level > write_lock_level ||
2790                             (level + 1 > write_lock_level &&
2791                             level + 1 < BTRFS_MAX_LEVEL &&
2792                             p->nodes[level + 1])) {
2793                                 write_lock_level = level + 1;
2794                                 btrfs_release_path(p);
2795                                 goto again;
2796                         }
2797
2798                         btrfs_set_path_blocking(p);
2799                         if (last_level)
2800                                 err = btrfs_cow_block(trans, root, b, NULL, 0,
2801                                                       &b);
2802                         else
2803                                 err = btrfs_cow_block(trans, root, b,
2804                                                       p->nodes[level + 1],
2805                                                       p->slots[level + 1], &b);
2806                         if (err) {
2807                                 ret = err;
2808                                 goto done;
2809                         }
2810                 }
2811 cow_done:
2812                 p->nodes[level] = b;
2813                 /*
2814                  * Leave path with blocking locks to avoid massive
2815                  * lock context switch, this is made on purpose.
2816                  */
2817
2818                 /*
2819                  * we have a lock on b and as long as we aren't changing
2820                  * the tree, there is no way to for the items in b to change.
2821                  * It is safe to drop the lock on our parent before we
2822                  * go through the expensive btree search on b.
2823                  *
2824                  * If we're inserting or deleting (ins_len != 0), then we might
2825                  * be changing slot zero, which may require changing the parent.
2826                  * So, we can't drop the lock until after we know which slot
2827                  * we're operating on.
2828                  */
2829                 if (!ins_len && !p->keep_locks) {
2830                         int u = level + 1;
2831
2832                         if (u < BTRFS_MAX_LEVEL && p->locks[u]) {
2833                                 btrfs_tree_unlock_rw(p->nodes[u], p->locks[u]);
2834                                 p->locks[u] = 0;
2835                         }
2836                 }
2837
2838                 ret = key_search(b, key, level, &prev_cmp, &slot);
2839                 if (ret < 0)
2840                         goto done;
2841
2842                 if (level != 0) {
2843                         int dec = 0;
2844                         if (ret && slot > 0) {
2845                                 dec = 1;
2846                                 slot -= 1;
2847                         }
2848                         p->slots[level] = slot;
2849                         err = setup_nodes_for_search(trans, root, p, b, level,
2850                                              ins_len, &write_lock_level);
2851                         if (err == -EAGAIN)
2852                                 goto again;
2853                         if (err) {
2854                                 ret = err;
2855                                 goto done;
2856                         }
2857                         b = p->nodes[level];
2858                         slot = p->slots[level];
2859
2860                         /*
2861                          * slot 0 is special, if we change the key
2862                          * we have to update the parent pointer
2863                          * which means we must have a write lock
2864                          * on the parent
2865                          */
2866                         if (slot == 0 && ins_len &&
2867                             write_lock_level < level + 1) {
2868                                 write_lock_level = level + 1;
2869                                 btrfs_release_path(p);
2870                                 goto again;
2871                         }
2872
2873                         unlock_up(p, level, lowest_unlock,
2874                                   min_write_lock_level, &write_lock_level);
2875
2876                         if (level == lowest_level) {
2877                                 if (dec)
2878                                         p->slots[level]++;
2879                                 goto done;
2880                         }
2881
2882                         err = read_block_for_search(root, p, &b, level,
2883                                                     slot, key);
2884                         if (err == -EAGAIN)
2885                                 goto again;
2886                         if (err) {
2887                                 ret = err;
2888                                 goto done;
2889                         }
2890
2891                         if (!p->skip_locking) {
2892                                 level = btrfs_header_level(b);
2893                                 if (level <= write_lock_level) {
2894                                         err = btrfs_try_tree_write_lock(b);
2895                                         if (!err) {
2896                                                 btrfs_set_path_blocking(p);
2897                                                 btrfs_tree_lock(b);
2898                                         }
2899                                         p->locks[level] = BTRFS_WRITE_LOCK;
2900                                 } else {
2901                                         err = btrfs_tree_read_lock_atomic(b);
2902                                         if (!err) {
2903                                                 btrfs_set_path_blocking(p);
2904                                                 btrfs_tree_read_lock(b);
2905                                         }
2906                                         p->locks[level] = BTRFS_READ_LOCK;
2907                                 }
2908                                 p->nodes[level] = b;
2909                         }
2910                 } else {
2911                         p->slots[level] = slot;
2912                         if (ins_len > 0 &&
2913                             btrfs_leaf_free_space(fs_info, b) < ins_len) {
2914                                 if (write_lock_level < 1) {
2915                                         write_lock_level = 1;
2916                                         btrfs_release_path(p);
2917                                         goto again;
2918                                 }
2919
2920                                 btrfs_set_path_blocking(p);
2921                                 err = split_leaf(trans, root, key,
2922                                                  p, ins_len, ret == 0);
2923
2924                                 BUG_ON(err > 0);
2925                                 if (err) {
2926                                         ret = err;
2927                                         goto done;
2928                                 }
2929                         }
2930                         if (!p->search_for_split)
2931                                 unlock_up(p, level, lowest_unlock,
2932                                           min_write_lock_level, NULL);
2933                         goto done;
2934                 }
2935         }
2936         ret = 1;
2937 done:
2938         /*
2939          * we don't really know what they plan on doing with the path
2940          * from here on, so for now just mark it as blocking
2941          */
2942         if (!p->leave_spinning)
2943                 btrfs_set_path_blocking(p);
2944         if (ret < 0 && !p->skip_release_on_error)
2945                 btrfs_release_path(p);
2946         return ret;
2947 }
2948
2949 /*
2950  * Like btrfs_search_slot, this looks for a key in the given tree. It uses the
2951  * current state of the tree together with the operations recorded in the tree
2952  * modification log to search for the key in a previous version of this tree, as
2953  * denoted by the time_seq parameter.
2954  *
2955  * Naturally, there is no support for insert, delete or cow operations.
2956  *
2957  * The resulting path and return value will be set up as if we called
2958  * btrfs_search_slot at that point in time with ins_len and cow both set to 0.
2959  */
2960 int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key,
2961                           struct btrfs_path *p, u64 time_seq)
2962 {
2963         struct btrfs_fs_info *fs_info = root->fs_info;
2964         struct extent_buffer *b;
2965         int slot;
2966         int ret;
2967         int err;
2968         int level;
2969         int lowest_unlock = 1;
2970         u8 lowest_level = 0;
2971         int prev_cmp = -1;
2972
2973         lowest_level = p->lowest_level;
2974         WARN_ON(p->nodes[0] != NULL);
2975
2976         if (p->search_commit_root) {
2977                 BUG_ON(time_seq);
2978                 return btrfs_search_slot(NULL, root, key, p, 0, 0);
2979         }
2980
2981 again:
2982         b = get_old_root(root, time_seq);
2983         if (!b) {
2984                 ret = -EIO;
2985                 goto done;
2986         }
2987         level = btrfs_header_level(b);
2988         p->locks[level] = BTRFS_READ_LOCK;
2989
2990         while (b) {
2991                 level = btrfs_header_level(b);
2992                 p->nodes[level] = b;
2993
2994                 /*
2995                  * we have a lock on b and as long as we aren't changing
2996                  * the tree, there is no way to for the items in b to change.
2997                  * It is safe to drop the lock on our parent before we
2998                  * go through the expensive btree search on b.
2999                  */
3000                 btrfs_unlock_up_safe(p, level + 1);
3001
3002                 /*
3003                  * Since we can unwind ebs we want to do a real search every
3004                  * time.
3005                  */
3006                 prev_cmp = -1;
3007                 ret = key_search(b, key, level, &prev_cmp, &slot);
3008
3009                 if (level != 0) {
3010                         int dec = 0;
3011                         if (ret && slot > 0) {
3012                                 dec = 1;
3013                                 slot -= 1;
3014                         }
3015                         p->slots[level] = slot;
3016                         unlock_up(p, level, lowest_unlock, 0, NULL);
3017
3018                         if (level == lowest_level) {
3019                                 if (dec)
3020                                         p->slots[level]++;
3021                                 goto done;
3022                         }
3023
3024                         err = read_block_for_search(root, p, &b, level,
3025                                                     slot, key);
3026                         if (err == -EAGAIN)
3027                                 goto again;
3028                         if (err) {
3029                                 ret = err;
3030                                 goto done;
3031                         }
3032
3033                         level = btrfs_header_level(b);
3034                         err = btrfs_tree_read_lock_atomic(b);
3035                         if (!err) {
3036                                 btrfs_set_path_blocking(p);
3037                                 btrfs_tree_read_lock(b);
3038                         }
3039                         b = tree_mod_log_rewind(fs_info, p, b, time_seq);
3040                         if (!b) {
3041                                 ret = -ENOMEM;
3042                                 goto done;
3043                         }
3044                         p->locks[level] = BTRFS_READ_LOCK;
3045                         p->nodes[level] = b;
3046                 } else {
3047                         p->slots[level] = slot;
3048                         unlock_up(p, level, lowest_unlock, 0, NULL);
3049                         goto done;
3050                 }
3051         }
3052         ret = 1;
3053 done:
3054         if (!p->leave_spinning)
3055                 btrfs_set_path_blocking(p);
3056         if (ret < 0)
3057                 btrfs_release_path(p);
3058
3059         return ret;
3060 }
3061
3062 /*
3063  * helper to use instead of search slot if no exact match is needed but
3064  * instead the next or previous item should be returned.
3065  * When find_higher is true, the next higher item is returned, the next lower
3066  * otherwise.
3067  * When return_any and find_higher are both true, and no higher item is found,
3068  * return the next lower instead.
3069  * When return_any is true and find_higher is false, and no lower item is found,
3070  * return the next higher instead.
3071  * It returns 0 if any item is found, 1 if none is found (tree empty), and
3072  * < 0 on error
3073  */
3074 int btrfs_search_slot_for_read(struct btrfs_root *root,
3075                                const struct btrfs_key *key,
3076                                struct btrfs_path *p, int find_higher,
3077                                int return_any)
3078 {
3079         int ret;
3080         struct extent_buffer *leaf;
3081
3082 again:
3083         ret = btrfs_search_slot(NULL, root, key, p, 0, 0);
3084         if (ret <= 0)
3085                 return ret;
3086         /*
3087          * a return value of 1 means the path is at the position where the
3088          * item should be inserted. Normally this is the next bigger item,
3089          * but in case the previous item is the last in a leaf, path points
3090          * to the first free slot in the previous leaf, i.e. at an invalid
3091          * item.
3092          */
3093         leaf = p->nodes[0];
3094
3095         if (find_higher) {
3096                 if (p->slots[0] >= btrfs_header_nritems(leaf)) {
3097                         ret = btrfs_next_leaf(root, p);
3098                         if (ret <= 0)
3099                                 return ret;
3100                         if (!return_any)
3101                                 return 1;
3102                         /*
3103                          * no higher item found, return the next
3104                          * lower instead
3105                          */
3106                         return_any = 0;
3107                         find_higher = 0;
3108                         btrfs_release_path(p);
3109                         goto again;
3110                 }
3111         } else {
3112                 if (p->slots[0] == 0) {
3113                         ret = btrfs_prev_leaf(root, p);
3114                         if (ret < 0)
3115                                 return ret;
3116                         if (!ret) {
3117                                 leaf = p->nodes[0];
3118                                 if (p->slots[0] == btrfs_header_nritems(leaf))
3119                                         p->slots[0]--;
3120                                 return 0;
3121                         }
3122                         if (!return_any)
3123                                 return 1;
3124                         /*
3125                          * no lower item found, return the next
3126                          * higher instead
3127                          */
3128                         return_any = 0;
3129                         find_higher = 1;
3130                         btrfs_release_path(p);
3131                         goto again;
3132                 } else {
3133                         --p->slots[0];
3134                 }
3135         }
3136         return 0;
3137 }
3138
3139 /*
3140  * adjust the pointers going up the tree, starting at level
3141  * making sure the right key of each node is points to 'key'.
3142  * This is used after shifting pointers to the left, so it stops
3143  * fixing up pointers when a given leaf/node is not in slot 0 of the
3144  * higher levels
3145  *
3146  */
3147 static void fixup_low_keys(struct btrfs_path *path,
3148                            struct btrfs_disk_key *key, int level)
3149 {
3150         int i;
3151         struct extent_buffer *t;
3152         int ret;
3153
3154         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
3155                 int tslot = path->slots[i];
3156
3157                 if (!path->nodes[i])
3158                         break;
3159                 t = path->nodes[i];
3160                 ret = tree_mod_log_insert_key(t, tslot, MOD_LOG_KEY_REPLACE,
3161                                 GFP_ATOMIC);
3162                 BUG_ON(ret < 0);
3163                 btrfs_set_node_key(t, key, tslot);
3164                 btrfs_mark_buffer_dirty(path->nodes[i]);
3165                 if (tslot != 0)
3166                         break;
3167         }
3168 }
3169
3170 /*
3171  * update item key.
3172  *
3173  * This function isn't completely safe. It's the caller's responsibility
3174  * that the new key won't break the order
3175  */
3176 void btrfs_set_item_key_safe(struct btrfs_fs_info *fs_info,
3177                              struct btrfs_path *path,
3178                              const struct btrfs_key *new_key)
3179 {
3180         struct btrfs_disk_key disk_key;
3181         struct extent_buffer *eb;
3182         int slot;
3183
3184         eb = path->nodes[0];
3185         slot = path->slots[0];
3186         if (slot > 0) {
3187                 btrfs_item_key(eb, &disk_key, slot - 1);
3188                 BUG_ON(comp_keys(&disk_key, new_key) >= 0);
3189         }
3190         if (slot < btrfs_header_nritems(eb) - 1) {
3191                 btrfs_item_key(eb, &disk_key, slot + 1);
3192                 BUG_ON(comp_keys(&disk_key, new_key) <= 0);
3193         }
3194
3195         btrfs_cpu_key_to_disk(&disk_key, new_key);
3196         btrfs_set_item_key(eb, &disk_key, slot);
3197         btrfs_mark_buffer_dirty(eb);
3198         if (slot == 0)
3199                 fixup_low_keys(path, &disk_key, 1);
3200 }
3201
3202 /*
3203  * try to push data from one node into the next node left in the
3204  * tree.
3205  *
3206  * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
3207  * error, and > 0 if there was no room in the left hand block.
3208  */
3209 static int push_node_left(struct btrfs_trans_handle *trans,
3210                           struct btrfs_fs_info *fs_info,
3211                           struct extent_buffer *dst,
3212                           struct extent_buffer *src, int empty)
3213 {
3214         int push_items = 0;
3215         int src_nritems;
3216         int dst_nritems;
3217         int ret = 0;
3218
3219         src_nritems = btrfs_header_nritems(src);
3220         dst_nritems = btrfs_header_nritems(dst);
3221         push_items = BTRFS_NODEPTRS_PER_BLOCK(fs_info) - dst_nritems;
3222         WARN_ON(btrfs_header_generation(src) != trans->transid);
3223         WARN_ON(btrfs_header_generation(dst) != trans->transid);
3224
3225         if (!empty && src_nritems <= 8)
3226                 return 1;
3227
3228         if (push_items <= 0)
3229                 return 1;
3230
3231         if (empty) {
3232                 push_items = min(src_nritems, push_items);
3233                 if (push_items < src_nritems) {
3234                         /* leave at least 8 pointers in the node if
3235                          * we aren't going to empty it
3236                          */
3237                         if (src_nritems - push_items < 8) {
3238                                 if (push_items <= 8)
3239                                         return 1;
3240                                 push_items -= 8;
3241                         }
3242                 }
3243         } else
3244                 push_items = min(src_nritems - 8, push_items);
3245
3246         ret = tree_mod_log_eb_copy(fs_info, dst, src, dst_nritems, 0,
3247                                    push_items);
3248         if (ret) {
3249                 btrfs_abort_transaction(trans, ret);
3250                 return ret;
3251         }
3252         copy_extent_buffer(dst, src,
3253                            btrfs_node_key_ptr_offset(dst_nritems),
3254                            btrfs_node_key_ptr_offset(0),
3255                            push_items * sizeof(struct btrfs_key_ptr));
3256
3257         if (push_items < src_nritems) {
3258                 /*
3259                  * Don't call tree_mod_log_insert_move here, key removal was
3260                  * already fully logged by tree_mod_log_eb_copy above.
3261                  */
3262                 memmove_extent_buffer(src, btrfs_node_key_ptr_offset(0),
3263                                       btrfs_node_key_ptr_offset(push_items),
3264                                       (src_nritems - push_items) *
3265                                       sizeof(struct btrfs_key_ptr));
3266         }
3267         btrfs_set_header_nritems(src, src_nritems - push_items);
3268         btrfs_set_header_nritems(dst, dst_nritems + push_items);
3269         btrfs_mark_buffer_dirty(src);
3270         btrfs_mark_buffer_dirty(dst);
3271
3272         return ret;
3273 }
3274
3275 /*
3276  * try to push data from one node into the next node right in the
3277  * tree.
3278  *
3279  * returns 0 if some ptrs were pushed, < 0 if there was some horrible
3280  * error, and > 0 if there was no room in the right hand block.
3281  *
3282  * this will  only push up to 1/2 the contents of the left node over
3283  */
3284 static int balance_node_right(struct btrfs_trans_handle *trans,
3285                               struct btrfs_fs_info *fs_info,
3286                               struct extent_buffer *dst,
3287                               struct extent_buffer *src)
3288 {
3289         int push_items = 0;
3290         int max_push;
3291         int src_nritems;
3292         int dst_nritems;
3293         int ret = 0;
3294
3295         WARN_ON(btrfs_header_generation(src) != trans->transid);
3296         WARN_ON(btrfs_header_generation(dst) != trans->transid);
3297
3298         src_nritems = btrfs_header_nritems(src);
3299         dst_nritems = btrfs_header_nritems(dst);
3300         push_items = BTRFS_NODEPTRS_PER_BLOCK(fs_info) - dst_nritems;
3301         if (push_items <= 0)
3302                 return 1;
3303
3304         if (src_nritems < 4)
3305                 return 1;
3306
3307         max_push = src_nritems / 2 + 1;
3308         /* don't try to empty the node */
3309         if (max_push >= src_nritems)
3310                 return 1;
3311
3312         if (max_push < push_items)
3313                 push_items = max_push;
3314
3315         ret = tree_mod_log_insert_move(dst, push_items, 0, dst_nritems);
3316         BUG_ON(ret < 0);
3317         memmove_extent_buffer(dst, btrfs_node_key_ptr_offset(push_items),
3318                                       btrfs_node_key_ptr_offset(0),
3319                                       (dst_nritems) *
3320                                       sizeof(struct btrfs_key_ptr));
3321
3322         ret = tree_mod_log_eb_copy(fs_info, dst, src, 0,
3323                                    src_nritems - push_items, push_items);
3324         if (ret) {
3325                 btrfs_abort_transaction(trans, ret);
3326                 return ret;
3327         }
3328         copy_extent_buffer(dst, src,
3329                            btrfs_node_key_ptr_offset(0),
3330                            btrfs_node_key_ptr_offset(src_nritems - push_items),
3331                            push_items * sizeof(struct btrfs_key_ptr));
3332
3333         btrfs_set_header_nritems(src, src_nritems - push_items);
3334         btrfs_set_header_nritems(dst, dst_nritems + push_items);
3335
3336         btrfs_mark_buffer_dirty(src);
3337         btrfs_mark_buffer_dirty(dst);
3338
3339         return ret;
3340 }
3341
3342 /*
3343  * helper function to insert a new root level in the tree.
3344  * A new node is allocated, and a single item is inserted to
3345  * point to the existing root
3346  *
3347  * returns zero on success or < 0 on failure.
3348  */
3349 static noinline int insert_new_root(struct btrfs_trans_handle *trans,
3350                            struct btrfs_root *root,
3351                            struct btrfs_path *path, int level)
3352 {
3353         struct btrfs_fs_info *fs_info = root->fs_info;
3354         u64 lower_gen;
3355         struct extent_buffer *lower;
3356         struct extent_buffer *c;
3357         struct extent_buffer *old;
3358         struct btrfs_disk_key lower_key;
3359         int ret;
3360
3361         BUG_ON(path->nodes[level]);
3362         BUG_ON(path->nodes[level-1] != root->node);
3363
3364         lower = path->nodes[level-1];
3365         if (level == 1)
3366                 btrfs_item_key(lower, &lower_key, 0);
3367         else
3368                 btrfs_node_key(lower, &lower_key, 0);
3369
3370         c = alloc_tree_block_no_bg_flush(trans, root, 0, &lower_key, level,
3371                                          root->node->start, 0);
3372         if (IS_ERR(c))
3373                 return PTR_ERR(c);
3374
3375         root_add_used(root, fs_info->nodesize);
3376
3377         btrfs_set_header_nritems(c, 1);
3378         btrfs_set_node_key(c, &lower_key, 0);
3379         btrfs_set_node_blockptr(c, 0, lower->start);
3380         lower_gen = btrfs_header_generation(lower);
3381         WARN_ON(lower_gen != trans->transid);
3382
3383         btrfs_set_node_ptr_generation(c, 0, lower_gen);
3384
3385         btrfs_mark_buffer_dirty(c);
3386
3387         old = root->node;
3388         ret = tree_mod_log_insert_root(root->node, c, 0);
3389         BUG_ON(ret < 0);
3390         rcu_assign_pointer(root->node, c);
3391
3392         /* the super has an extra ref to root->node */
3393         free_extent_buffer(old);
3394
3395         add_root_to_dirty_list(root);
3396         extent_buffer_get(c);
3397         path->nodes[level] = c;
3398         path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
3399         path->slots[level] = 0;
3400         return 0;
3401 }
3402
3403 /*
3404  * worker function to insert a single pointer in a node.
3405  * the node should have enough room for the pointer already
3406  *
3407  * slot and level indicate where you want the key to go, and
3408  * blocknr is the block the key points to.
3409  */
3410 static void insert_ptr(struct btrfs_trans_handle *trans,
3411                        struct btrfs_fs_info *fs_info, struct btrfs_path *path,
3412                        struct btrfs_disk_key *key, u64 bytenr,
3413                        int slot, int level)
3414 {
3415         struct extent_buffer *lower;
3416         int nritems;
3417         int ret;
3418
3419         BUG_ON(!path->nodes[level]);
3420         btrfs_assert_tree_locked(path->nodes[level]);
3421         lower = path->nodes[level];
3422         nritems = btrfs_header_nritems(lower);
3423         BUG_ON(slot > nritems);
3424         BUG_ON(nritems == BTRFS_NODEPTRS_PER_BLOCK(fs_info));
3425         if (slot != nritems) {
3426                 if (level) {
3427                         ret = tree_mod_log_insert_move(lower, slot + 1, slot,
3428                                         nritems - slot);
3429                         BUG_ON(ret < 0);
3430                 }
3431                 memmove_extent_buffer(lower,
3432                               btrfs_node_key_ptr_offset(slot + 1),
3433                               btrfs_node_key_ptr_offset(slot),
3434                               (nritems - slot) * sizeof(struct btrfs_key_ptr));
3435         }
3436         if (level) {
3437                 ret = tree_mod_log_insert_key(lower, slot, MOD_LOG_KEY_ADD,
3438                                 GFP_NOFS);
3439                 BUG_ON(ret < 0);
3440         }
3441         btrfs_set_node_key(lower, key, slot);
3442         btrfs_set_node_blockptr(lower, slot, bytenr);
3443         WARN_ON(trans->transid == 0);
3444         btrfs_set_node_ptr_generation(lower, slot, trans->transid);
3445         btrfs_set_header_nritems(lower, nritems + 1);
3446         btrfs_mark_buffer_dirty(lower);
3447 }
3448
3449 /*
3450  * split the node at the specified level in path in two.
3451  * The path is corrected to point to the appropriate node after the split
3452  *
3453  * Before splitting this tries to make some room in the node by pushing
3454  * left and right, if either one works, it returns right away.
3455  *
3456  * returns 0 on success and < 0 on failure
3457  */
3458 static noinline int split_node(struct btrfs_trans_handle *trans,
3459                                struct btrfs_root *root,
3460                                struct btrfs_path *path, int level)
3461 {
3462         struct btrfs_fs_info *fs_info = root->fs_info;
3463         struct extent_buffer *c;
3464         struct extent_buffer *split;
3465         struct btrfs_disk_key disk_key;
3466         int mid;
3467         int ret;
3468         u32 c_nritems;
3469
3470         c = path->nodes[level];
3471         WARN_ON(btrfs_header_generation(c) != trans->transid);
3472         if (c == root->node) {
3473                 /*
3474                  * trying to split the root, lets make a new one
3475                  *
3476                  * tree mod log: We don't log_removal old root in
3477                  * insert_new_root, because that root buffer will be kept as a
3478                  * normal node. We are going to log removal of half of the
3479                  * elements below with tree_mod_log_eb_copy. We're holding a
3480                  * tree lock on the buffer, which is why we cannot race with
3481                  * other tree_mod_log users.
3482                  */
3483                 ret = insert_new_root(trans, root, path, level + 1);
3484                 if (ret)
3485                         return ret;
3486         } else {
3487                 ret = push_nodes_for_insert(trans, root, path, level);
3488                 c = path->nodes[level];
3489                 if (!ret && btrfs_header_nritems(c) <
3490                     BTRFS_NODEPTRS_PER_BLOCK(fs_info) - 3)
3491                         return 0;
3492                 if (ret < 0)
3493                         return ret;
3494         }
3495
3496         c_nritems = btrfs_header_nritems(c);
3497         mid = (c_nritems + 1) / 2;
3498         btrfs_node_key(c, &disk_key, mid);
3499
3500         split = alloc_tree_block_no_bg_flush(trans, root, 0, &disk_key, level,
3501                                              c->start, 0);
3502         if (IS_ERR(split))
3503                 return PTR_ERR(split);
3504
3505         root_add_used(root, fs_info->nodesize);
3506         ASSERT(btrfs_header_level(c) == level);
3507
3508         ret = tree_mod_log_eb_copy(fs_info, split, c, 0, mid, c_nritems - mid);
3509         if (ret) {
3510                 btrfs_abort_transaction(trans, ret);
3511                 return ret;
3512         }
3513         copy_extent_buffer(split, c,
3514                            btrfs_node_key_ptr_offset(0),
3515                            btrfs_node_key_ptr_offset(mid),
3516                            (c_nritems - mid) * sizeof(struct btrfs_key_ptr));
3517         btrfs_set_header_nritems(split, c_nritems - mid);
3518         btrfs_set_header_nritems(c, mid);
3519         ret = 0;
3520
3521         btrfs_mark_buffer_dirty(c);
3522         btrfs_mark_buffer_dirty(split);
3523
3524         insert_ptr(trans, fs_info, path, &disk_key, split->start,
3525                    path->slots[level + 1] + 1, level + 1);
3526
3527         if (path->slots[level] >= mid) {
3528                 path->slots[level] -= mid;
3529                 btrfs_tree_unlock(c);
3530                 free_extent_buffer(c);
3531                 path->nodes[level] = split;
3532                 path->slots[level + 1] += 1;
3533         } else {
3534                 btrfs_tree_unlock(split);
3535                 free_extent_buffer(split);
3536         }
3537         return ret;
3538 }
3539
3540 /*
3541  * how many bytes are required to store the items in a leaf.  start
3542  * and nr indicate which items in the leaf to check.  This totals up the
3543  * space used both by the item structs and the item data
3544  */
3545 static int leaf_space_used(struct extent_buffer *l, int start, int nr)
3546 {
3547         struct btrfs_item *start_item;
3548         struct btrfs_item *end_item;
3549         struct btrfs_map_token token;
3550         int data_len;
3551         int nritems = btrfs_header_nritems(l);
3552         int end = min(nritems, start + nr) - 1;
3553
3554         if (!nr)
3555                 return 0;
3556         btrfs_init_map_token(&token);
3557         start_item = btrfs_item_nr(start);
3558         end_item = btrfs_item_nr(end);
3559         data_len = btrfs_token_item_offset(l, start_item, &token) +
3560                 btrfs_token_item_size(l, start_item, &token);
3561         data_len = data_len - btrfs_token_item_offset(l, end_item, &token);
3562         data_len += sizeof(struct btrfs_item) * nr;
3563         WARN_ON(data_len < 0);
3564         return data_len;
3565 }
3566
3567 /*
3568  * The space between the end of the leaf items and
3569  * the start of the leaf data.  IOW, how much room
3570  * the leaf has left for both items and data
3571  */
3572 noinline int btrfs_leaf_free_space(struct btrfs_fs_info *fs_info,
3573                                    struct extent_buffer *leaf)
3574 {
3575         int nritems = btrfs_header_nritems(leaf);
3576         int ret;
3577
3578         ret = BTRFS_LEAF_DATA_SIZE(fs_info) - leaf_space_used(leaf, 0, nritems);
3579         if (ret < 0) {
3580                 btrfs_crit(fs_info,
3581                            "leaf free space ret %d, leaf data size %lu, used %d nritems %d",
3582                            ret,
3583                            (unsigned long) BTRFS_LEAF_DATA_SIZE(fs_info),
3584                            leaf_space_used(leaf, 0, nritems), nritems);
3585         }
3586         return ret;
3587 }
3588
3589 /*
3590  * min slot controls the lowest index we're willing to push to the
3591  * right.  We'll push up to and including min_slot, but no lower
3592  */
3593 static noinline int __push_leaf_right(struct btrfs_fs_info *fs_info,
3594                                       struct btrfs_path *path,
3595                                       int data_size, int empty,
3596                                       struct extent_buffer *right,
3597                                       int free_space, u32 left_nritems,
3598                                       u32 min_slot)
3599 {
3600         struct extent_buffer *left = path->nodes[0];
3601         struct extent_buffer *upper = path->nodes[1];
3602         struct btrfs_map_token token;
3603         struct btrfs_disk_key disk_key;
3604         int slot;
3605         u32 i;
3606         int push_space = 0;
3607         int push_items = 0;
3608         struct btrfs_item *item;
3609         u32 nr;
3610         u32 right_nritems;
3611         u32 data_end;
3612         u32 this_item_size;
3613
3614         btrfs_init_map_token(&token);
3615
3616         if (empty)
3617                 nr = 0;
3618         else
3619                 nr = max_t(u32, 1, min_slot);
3620
3621         if (path->slots[0] >= left_nritems)
3622                 push_space += data_size;
3623
3624         slot = path->slots[1];
3625         i = left_nritems - 1;
3626         while (i >= nr) {
3627                 item = btrfs_item_nr(i);
3628
3629                 if (!empty && push_items > 0) {
3630                         if (path->slots[0] > i)
3631                                 break;
3632                         if (path->slots[0] == i) {
3633                                 int space = btrfs_leaf_free_space(fs_info, left);
3634                                 if (space + push_space * 2 > free_space)
3635                                         break;
3636                         }
3637                 }
3638
3639                 if (path->slots[0] == i)
3640                         push_space += data_size;
3641
3642                 this_item_size = btrfs_item_size(left, item);
3643                 if (this_item_size + sizeof(*item) + push_space > free_space)
3644                         break;
3645
3646                 push_items++;
3647                 push_space += this_item_size + sizeof(*item);
3648                 if (i == 0)
3649                         break;
3650                 i--;
3651         }
3652
3653         if (push_items == 0)
3654                 goto out_unlock;
3655
3656         WARN_ON(!empty && push_items == left_nritems);
3657
3658         /* push left to right */
3659         right_nritems = btrfs_header_nritems(right);
3660
3661         push_space = btrfs_item_end_nr(left, left_nritems - push_items);
3662         push_space -= leaf_data_end(fs_info, left);
3663
3664         /* make room in the right data area */
3665         data_end = leaf_data_end(fs_info, right);
3666         memmove_extent_buffer(right,
3667                               BTRFS_LEAF_DATA_OFFSET + data_end - push_space,
3668                               BTRFS_LEAF_DATA_OFFSET + data_end,
3669                               BTRFS_LEAF_DATA_SIZE(fs_info) - data_end);
3670
3671         /* copy from the left data area */
3672         copy_extent_buffer(right, left, BTRFS_LEAF_DATA_OFFSET +
3673                      BTRFS_LEAF_DATA_SIZE(fs_info) - push_space,
3674                      BTRFS_LEAF_DATA_OFFSET + leaf_data_end(fs_info, left),
3675                      push_space);
3676
3677         memmove_extent_buffer(right, btrfs_item_nr_offset(push_items),
3678                               btrfs_item_nr_offset(0),
3679                               right_nritems * sizeof(struct btrfs_item));
3680
3681         /* copy the items from left to right */
3682         copy_extent_buffer(right, left, btrfs_item_nr_offset(0),
3683                    btrfs_item_nr_offset(left_nritems - push_items),
3684                    push_items * sizeof(struct btrfs_item));
3685
3686         /* update the item pointers */
3687         right_nritems += push_items;
3688         btrfs_set_header_nritems(right, right_nritems);
3689         push_space = BTRFS_LEAF_DATA_SIZE(fs_info);
3690         for (i = 0; i < right_nritems; i++) {
3691                 item = btrfs_item_nr(i);
3692                 push_space -= btrfs_token_item_size(right, item, &token);
3693                 btrfs_set_token_item_offset(right, item, push_space, &token);
3694         }
3695
3696         left_nritems -= push_items;
3697         btrfs_set_header_nritems(left, left_nritems);
3698
3699         if (left_nritems)
3700                 btrfs_mark_buffer_dirty(left);
3701         else
3702                 clean_tree_block(fs_info, left);
3703
3704         btrfs_mark_buffer_dirty(right);
3705
3706         btrfs_item_key(right, &disk_key, 0);
3707         btrfs_set_node_key(upper, &disk_key, slot + 1);
3708         btrfs_mark_buffer_dirty(upper);
3709
3710         /* then fixup the leaf pointer in the path */
3711         if (path->slots[0] >= left_nritems) {
3712                 path->slots[0] -= left_nritems;
3713                 if (btrfs_header_nritems(path->nodes[0]) == 0)
3714                         clean_tree_block(fs_info, path->nodes[0]);
3715                 btrfs_tree_unlock(path->nodes[0]);
3716                 free_extent_buffer(path->nodes[0]);
3717                 path->nodes[0] = right;
3718                 path->slots[1] += 1;
3719         } else {
3720                 btrfs_tree_unlock(right);
3721                 free_extent_buffer(right);
3722         }
3723         return 0;
3724
3725 out_unlock:
3726         btrfs_tree_unlock(right);
3727         free_extent_buffer(right);
3728         return 1;
3729 }
3730
3731 /*
3732  * push some data in the path leaf to the right, trying to free up at
3733  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3734  *
3735  * returns 1 if the push failed because the other node didn't have enough
3736  * room, 0 if everything worked out and < 0 if there were major errors.
3737  *
3738  * this will push starting from min_slot to the end of the leaf.  It won't
3739  * push any slot lower than min_slot
3740  */
3741 static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
3742                            *root, struct btrfs_path *path,
3743                            int min_data_size, int data_size,
3744                            int empty, u32 min_slot)
3745 {
3746         struct btrfs_fs_info *fs_info = root->fs_info;
3747         struct extent_buffer *left = path->nodes[0];
3748         struct extent_buffer *right;
3749         struct extent_buffer *upper;
3750         int slot;
3751         int free_space;
3752         u32 left_nritems;
3753         int ret;
3754
3755         if (!path->nodes[1])
3756                 return 1;
3757
3758         slot = path->slots[1];
3759         upper = path->nodes[1];
3760         if (slot >= btrfs_header_nritems(upper) - 1)
3761                 return 1;
3762
3763         btrfs_assert_tree_locked(path->nodes[1]);
3764
3765         right = read_node_slot(fs_info, upper, slot + 1);
3766         /*
3767          * slot + 1 is not valid or we fail to read the right node,
3768          * no big deal, just return.
3769          */
3770         if (IS_ERR(right))
3771                 return 1;
3772
3773         btrfs_tree_lock(right);
3774         btrfs_set_lock_blocking(right);
3775
3776         free_space = btrfs_leaf_free_space(fs_info, right);
3777         if (free_space < data_size)
3778                 goto out_unlock;
3779
3780         /* cow and double check */
3781         ret = btrfs_cow_block(trans, root, right, upper,
3782                               slot + 1, &right);
3783         if (ret)
3784                 goto out_unlock;
3785
3786         free_space = btrfs_leaf_free_space(fs_info, right);
3787         if (free_space < data_size)
3788                 goto out_unlock;
3789
3790         left_nritems = btrfs_header_nritems(left);
3791         if (left_nritems == 0)
3792                 goto out_unlock;
3793
3794         if (path->slots[0] == left_nritems && !empty) {
3795                 /* Key greater than all keys in the leaf, right neighbor has
3796                  * enough room for it and we're not emptying our leaf to delete
3797                  * it, therefore use right neighbor to insert the new item and
3798                  * no need to touch/dirty our left leaf. */
3799                 btrfs_tree_unlock(left);
3800                 free_extent_buffer(left);
3801                 path->nodes[0] = right;
3802                 path->slots[0] = 0;
3803                 path->slots[1]++;
3804                 return 0;
3805         }
3806
3807         return __push_leaf_right(fs_info, path, min_data_size, empty,
3808                                 right, free_space, left_nritems, min_slot);
3809 out_unlock:
3810         btrfs_tree_unlock(right);
3811         free_extent_buffer(right);
3812         return 1;
3813 }
3814
3815 /*
3816  * push some data in the path leaf to the left, trying to free up at
3817  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3818  *
3819  * max_slot can put a limit on how far into the leaf we'll push items.  The
3820  * item at 'max_slot' won't be touched.  Use (u32)-1 to make us do all the
3821  * items
3822  */
3823 static noinline int __push_leaf_left(struct btrfs_fs_info *fs_info,
3824                                      struct btrfs_path *path, int data_size,
3825                                      int empty, struct extent_buffer *left,
3826                                      int free_space, u32 right_nritems,
3827                                      u32 max_slot)
3828 {
3829         struct btrfs_disk_key disk_key;
3830         struct extent_buffer *right = path->nodes[0];
3831         int i;
3832         int push_space = 0;
3833         int push_items = 0;
3834         struct btrfs_item *item;
3835         u32 old_left_nritems;
3836         u32 nr;
3837         int ret = 0;
3838         u32 this_item_size;
3839         u32 old_left_item_size;
3840         struct btrfs_map_token token;
3841
3842         btrfs_init_map_token(&token);
3843
3844         if (empty)
3845                 nr = min(right_nritems, max_slot);
3846         else
3847                 nr = min(right_nritems - 1, max_slot);
3848
3849         for (i = 0; i < nr; i++) {
3850                 item = btrfs_item_nr(i);
3851
3852                 if (!empty && push_items > 0) {
3853                         if (path->slots[0] < i)
3854                                 break;
3855                         if (path->slots[0] == i) {
3856                                 int space = btrfs_leaf_free_space(fs_info, right);
3857                                 if (space + push_space * 2 > free_space)
3858                                         break;
3859                         }
3860                 }
3861
3862                 if (path->slots[0] == i)
3863                         push_space += data_size;
3864
3865                 this_item_size = btrfs_item_size(right, item);
3866                 if (this_item_size + sizeof(*item) + push_space > free_space)
3867                         break;
3868
3869                 push_items++;
3870                 push_space += this_item_size + sizeof(*item);
3871         }
3872
3873         if (push_items == 0) {
3874                 ret = 1;
3875                 goto out;
3876         }
3877         WARN_ON(!empty && push_items == btrfs_header_nritems(right));
3878
3879         /* push data from right to left */
3880         copy_extent_buffer(left, right,
3881                            btrfs_item_nr_offset(btrfs_header_nritems(left)),
3882                            btrfs_item_nr_offset(0),
3883                            push_items * sizeof(struct btrfs_item));
3884
3885         push_space = BTRFS_LEAF_DATA_SIZE(fs_info) -
3886                      btrfs_item_offset_nr(right, push_items - 1);
3887
3888         copy_extent_buffer(left, right, BTRFS_LEAF_DATA_OFFSET +
3889                      leaf_data_end(fs_info, left) - push_space,
3890                      BTRFS_LEAF_DATA_OFFSET +
3891                      btrfs_item_offset_nr(right, push_items - 1),
3892                      push_space);
3893         old_left_nritems = btrfs_header_nritems(left);
3894         BUG_ON(old_left_nritems <= 0);
3895
3896         old_left_item_size = btrfs_item_offset_nr(left, old_left_nritems - 1);
3897         for (i = old_left_nritems; i < old_left_nritems + push_items; i++) {
3898                 u32 ioff;
3899
3900                 item = btrfs_item_nr(i);
3901
3902                 ioff = btrfs_token_item_offset(left, item, &token);
3903                 btrfs_set_token_item_offset(left, item,
3904                       ioff - (BTRFS_LEAF_DATA_SIZE(fs_info) - old_left_item_size),
3905                       &token);
3906         }
3907         btrfs_set_header_nritems(left, old_left_nritems + push_items);
3908
3909         /* fixup right node */
3910         if (push_items > right_nritems)
3911                 WARN(1, KERN_CRIT "push items %d nr %u\n", push_items,
3912                        right_nritems);
3913
3914         if (push_items < right_nritems) {
3915                 push_space = btrfs_item_offset_nr(right, push_items - 1) -
3916                                                   leaf_data_end(fs_info, right);
3917                 memmove_extent_buffer(right, BTRFS_LEAF_DATA_OFFSET +
3918                                       BTRFS_LEAF_DATA_SIZE(fs_info) - push_space,
3919                                       BTRFS_LEAF_DATA_OFFSET +
3920                                       leaf_data_end(fs_info, right), push_space);
3921
3922                 memmove_extent_buffer(right, btrfs_item_nr_offset(0),
3923                               btrfs_item_nr_offset(push_items),
3924                              (btrfs_header_nritems(right) - push_items) *
3925                              sizeof(struct btrfs_item));
3926         }
3927         right_nritems -= push_items;
3928         btrfs_set_header_nritems(right, right_nritems);
3929         push_space = BTRFS_LEAF_DATA_SIZE(fs_info);
3930         for (i = 0; i < right_nritems; i++) {
3931                 item = btrfs_item_nr(i);
3932
3933                 push_space = push_space - btrfs_token_item_size(right,
3934                                                                 item, &token);
3935                 btrfs_set_token_item_offset(right, item, push_space, &token);
3936         }
3937
3938         btrfs_mark_buffer_dirty(left);
3939         if (right_nritems)
3940                 btrfs_mark_buffer_dirty(right);
3941         else
3942                 clean_tree_block(fs_info, right);
3943
3944         btrfs_item_key(right, &disk_key, 0);
3945         fixup_low_keys(path, &disk_key, 1);
3946
3947         /* then fixup the leaf pointer in the path */
3948         if (path->slots[0] < push_items) {
3949                 path->slots[0] += old_left_nritems;
3950                 btrfs_tree_unlock(path->nodes[0]);
3951                 free_extent_buffer(path->nodes[0]);
3952                 path->nodes[0] = left;
3953                 path->slots[1] -= 1;
3954         } else {
3955                 btrfs_tree_unlock(left);
3956                 free_extent_buffer(left);
3957                 path->slots[0] -= push_items;
3958         }
3959         BUG_ON(path->slots[0] < 0);
3960         return ret;
3961 out:
3962         btrfs_tree_unlock(left);
3963         free_extent_buffer(left);
3964         return ret;
3965 }
3966
3967 /*
3968  * push some data in the path leaf to the left, trying to free up at
3969  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3970  *
3971  * max_slot can put a limit on how far into the leaf we'll push items.  The
3972  * item at 'max_slot' won't be touched.  Use (u32)-1 to make us push all the
3973  * items
3974  */
3975 static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
3976                           *root, struct btrfs_path *path, int min_data_size,
3977                           int data_size, int empty, u32 max_slot)
3978 {
3979         struct btrfs_fs_info *fs_info = root->fs_info;
3980         struct extent_buffer *right = path->nodes[0];
3981         struct extent_buffer *left;
3982         int slot;
3983         int free_space;
3984         u32 right_nritems;
3985         int ret = 0;
3986
3987         slot = path->slots[1];
3988         if (slot == 0)
3989                 return 1;
3990         if (!path->nodes[1])
3991                 return 1;
3992
3993         right_nritems = btrfs_header_nritems(right);
3994         if (right_nritems == 0)
3995                 return 1;
3996
3997         btrfs_assert_tree_locked(path->nodes[1]);
3998
3999         left = read_node_slot(fs_info, path->nodes[1], slot - 1);
4000         /*
4001          * slot - 1 is not valid or we fail to read the left node,
4002          * no big deal, just return.
4003          */
4004         if (IS_ERR(left))
4005                 return 1;
4006
4007         btrfs_tree_lock(left);
4008         btrfs_set_lock_blocking(left);
4009
4010         free_space = btrfs_leaf_free_space(fs_info, left);
4011         if (free_space < data_size) {
4012                 ret = 1;
4013                 goto out;
4014         }
4015
4016         /* cow and double check */
4017         ret = btrfs_cow_block(trans, root, left,
4018                               path->nodes[1], slot - 1, &left);
4019         if (ret) {
4020                 /* we hit -ENOSPC, but it isn't fatal here */
4021                 if (ret == -ENOSPC)
4022                         ret = 1;
4023                 goto out;
4024         }
4025
4026         free_space = btrfs_leaf_free_space(fs_info, left);
4027         if (free_space < data_size) {
4028                 ret = 1;
4029                 goto out;
4030         }
4031
4032         return __push_leaf_left(fs_info, path, min_data_size,
4033                                empty, left, free_space, right_nritems,
4034                                max_slot);
4035 out:
4036         btrfs_tree_unlock(left);
4037         free_extent_buffer(left);
4038         return ret;
4039 }
4040
4041 /*
4042  * split the path's leaf in two, making sure there is at least data_size
4043  * available for the resulting leaf level of the path.
4044  */
4045 static noinline void copy_for_split(struct btrfs_trans_handle *trans,
4046                                     struct btrfs_fs_info *fs_info,
4047                                     struct btrfs_path *path,
4048                                     struct extent_buffer *l,
4049                                     struct extent_buffer *right,
4050                                     int slot, int mid, int nritems)
4051 {
4052         int data_copy_size;
4053         int rt_data_off;
4054         int i;
4055         struct btrfs_disk_key disk_key;
4056         struct btrfs_map_token token;
4057
4058         btrfs_init_map_token(&token);
4059
4060         nritems = nritems - mid;
4061         btrfs_set_header_nritems(right, nritems);
4062         data_copy_size = btrfs_item_end_nr(l, mid) - leaf_data_end(fs_info, l);
4063
4064         copy_extent_buffer(right, l, btrfs_item_nr_offset(0),
4065                            btrfs_item_nr_offset(mid),
4066                            nritems * sizeof(struct btrfs_item));
4067
4068         copy_extent_buffer(right, l,
4069                      BTRFS_LEAF_DATA_OFFSET + BTRFS_LEAF_DATA_SIZE(fs_info) -
4070                      data_copy_size, BTRFS_LEAF_DATA_OFFSET +
4071                      leaf_data_end(fs_info, l), data_copy_size);
4072
4073         rt_data_off = BTRFS_LEAF_DATA_SIZE(fs_info) - btrfs_item_end_nr(l, mid);
4074
4075         for (i = 0; i < nritems; i++) {
4076                 struct btrfs_item *item = btrfs_item_nr(i);
4077                 u32 ioff;
4078
4079                 ioff = btrfs_token_item_offset(right, item, &token);
4080                 btrfs_set_token_item_offset(right, item,
4081                                             ioff + rt_data_off, &token);
4082         }
4083
4084         btrfs_set_header_nritems(l, mid);
4085         btrfs_item_key(right, &disk_key, 0);
4086         insert_ptr(trans, fs_info, path, &disk_key, right->start,
4087                    path->slots[1] + 1, 1);
4088
4089         btrfs_mark_buffer_dirty(right);
4090         btrfs_mark_buffer_dirty(l);
4091         BUG_ON(path->slots[0] != slot);
4092
4093         if (mid <= slot) {
4094                 btrfs_tree_unlock(path->nodes[0]);
4095                 free_extent_buffer(path->nodes[0]);
4096                 path->nodes[0] = right;
4097                 path->slots[0] -= mid;
4098                 path->slots[1] += 1;
4099         } else {
4100                 btrfs_tree_unlock(right);
4101                 free_extent_buffer(right);
4102         }
4103
4104         BUG_ON(path->slots[0] < 0);
4105 }
4106
4107 /*
4108  * double splits happen when we need to insert a big item in the middle
4109  * of a leaf.  A double split can leave us with 3 mostly empty leaves:
4110  * leaf: [ slots 0 - N] [ our target ] [ N + 1 - total in leaf ]
4111  *          A                 B                 C
4112  *
4113  * We avoid this by trying to push the items on either side of our target
4114  * into the adjacent leaves.  If all goes well we can avoid the double split
4115  * completely.
4116  */
4117 static noinline int push_for_double_split(struct btrfs_trans_handle *trans,
4118                                           struct btrfs_root *root,
4119                                           struct btrfs_path *path,
4120                                           int data_size)
4121 {
4122         struct btrfs_fs_info *fs_info = root->fs_info;
4123         int ret;
4124         int progress = 0;
4125         int slot;
4126         u32 nritems;
4127         int space_needed = data_size;
4128
4129         slot = path->slots[0];
4130         if (slot < btrfs_header_nritems(path->nodes[0]))
4131                 space_needed -= btrfs_leaf_free_space(fs_info, path->nodes[0]);
4132
4133         /*
4134          * try to push all the items after our slot into the
4135          * right leaf
4136          */
4137         ret = push_leaf_right(trans, root, path, 1, space_needed, 0, slot);
4138         if (ret < 0)
4139                 return ret;
4140
4141         if (ret == 0)
4142                 progress++;
4143
4144         nritems = btrfs_header_nritems(path->nodes[0]);
4145         /*
4146          * our goal is to get our slot at the start or end of a leaf.  If
4147          * we've done so we're done
4148          */
4149         if (path->slots[0] == 0 || path->slots[0] == nritems)
4150                 return 0;
4151
4152         if (btrfs_leaf_free_space(fs_info, path->nodes[0]) >= data_size)
4153                 return 0;
4154
4155         /* try to push all the items before our slot into the next leaf */
4156         slot = path->slots[0];
4157         space_needed = data_size;
4158         if (slot > 0)
4159                 space_needed -= btrfs_leaf_free_space(fs_info, path->nodes[0]);
4160         ret = push_leaf_left(trans, root, path, 1, space_needed, 0, slot);
4161         if (ret < 0)
4162                 return ret;
4163
4164         if (ret == 0)
4165                 progress++;
4166
4167         if (progress)
4168                 return 0;
4169         return 1;
4170 }
4171
4172 /*
4173  * split the path's leaf in two, making sure there is at least data_size
4174  * available for the resulting leaf level of the path.
4175  *
4176  * returns 0 if all went well and < 0 on failure.
4177  */
4178 static noinline int split_leaf(struct btrfs_trans_handle *trans,
4179                                struct btrfs_root *root,
4180                                const struct btrfs_key *ins_key,
4181                                struct btrfs_path *path, int data_size,
4182                                int extend)
4183 {
4184         struct btrfs_disk_key disk_key;
4185         struct extent_buffer *l;
4186         u32 nritems;
4187         int mid;
4188         int slot;
4189         struct extent_buffer *right;
4190         struct btrfs_fs_info *fs_info = root->fs_info;
4191         int ret = 0;
4192         int wret;
4193         int split;
4194         int num_doubles = 0;
4195         int tried_avoid_double = 0;
4196
4197         l = path->nodes[0];
4198         slot = path->slots[0];
4199         if (extend && data_size + btrfs_item_size_nr(l, slot) +
4200             sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(fs_info))
4201                 return -EOVERFLOW;
4202
4203         /* first try to make some room by pushing left and right */
4204         if (data_size && path->nodes[1]) {
4205                 int space_needed = data_size;
4206
4207                 if (slot < btrfs_header_nritems(l))
4208                         space_needed -= btrfs_leaf_free_space(fs_info, l);
4209
4210                 wret = push_leaf_right(trans, root, path, space_needed,
4211                                        space_needed, 0, 0);
4212                 if (wret < 0)
4213                         return wret;
4214                 if (wret) {
4215                         space_needed = data_size;
4216                         if (slot > 0)
4217                                 space_needed -= btrfs_leaf_free_space(fs_info,
4218                                                                       l);
4219                         wret = push_leaf_left(trans, root, path, space_needed,
4220                                               space_needed, 0, (u32)-1);
4221                         if (wret < 0)
4222                                 return wret;
4223                 }
4224                 l = path->nodes[0];
4225
4226                 /* did the pushes work? */
4227                 if (btrfs_leaf_free_space(fs_info, l) >= data_size)
4228                         return 0;
4229         }
4230
4231         if (!path->nodes[1]) {
4232                 ret = insert_new_root(trans, root, path, 1);
4233                 if (ret)
4234                         return ret;
4235         }
4236 again:
4237         split = 1;
4238         l = path->nodes[0];
4239         slot = path->slots[0];
4240         nritems = btrfs_header_nritems(l);
4241         mid = (nritems + 1) / 2;
4242
4243         if (mid <= slot) {
4244                 if (nritems == 1 ||
4245                     leaf_space_used(l, mid, nritems - mid) + data_size >
4246                         BTRFS_LEAF_DATA_SIZE(fs_info)) {
4247                         if (slot >= nritems) {
4248                                 split = 0;
4249                         } else {
4250                                 mid = slot;
4251                                 if (mid != nritems &&
4252                                     leaf_space_used(l, mid, nritems - mid) +
4253                                     data_size > BTRFS_LEAF_DATA_SIZE(fs_info)) {
4254                                         if (data_size && !tried_avoid_double)
4255                                                 goto push_for_double;
4256                                         split = 2;
4257                                 }
4258                         }
4259                 }
4260         } else {
4261                 if (leaf_space_used(l, 0, mid) + data_size >
4262                         BTRFS_LEAF_DATA_SIZE(fs_info)) {
4263                         if (!extend && data_size && slot == 0) {
4264                                 split = 0;
4265                         } else if ((extend || !data_size) && slot == 0) {
4266                                 mid = 1;
4267                         } else {
4268                                 mid = slot;
4269                                 if (mid != nritems &&
4270                                     leaf_space_used(l, mid, nritems - mid) +
4271                                     data_size > BTRFS_LEAF_DATA_SIZE(fs_info)) {
4272                                         if (data_size && !tried_avoid_double)
4273                                                 goto push_for_double;
4274                                         split = 2;
4275                                 }
4276                         }
4277                 }
4278         }
4279
4280         if (split == 0)
4281                 btrfs_cpu_key_to_disk(&disk_key, ins_key);
4282         else
4283                 btrfs_item_key(l, &disk_key, mid);
4284
4285         right = alloc_tree_block_no_bg_flush(trans, root, 0, &disk_key, 0,
4286                                              l->start, 0);
4287         if (IS_ERR(right))
4288                 return PTR_ERR(right);
4289
4290         root_add_used(root, fs_info->nodesize);
4291
4292         if (split == 0) {
4293                 if (mid <= slot) {
4294                         btrfs_set_header_nritems(right, 0);
4295                         insert_ptr(trans, fs_info, path, &disk_key,
4296                                    right->start, path->slots[1] + 1, 1);
4297                         btrfs_tree_unlock(path->nodes[0]);
4298                         free_extent_buffer(path->nodes[0]);
4299                         path->nodes[0] = right;
4300                         path->slots[0] = 0;
4301                         path->slots[1] += 1;
4302                 } else {
4303                         btrfs_set_header_nritems(right, 0);
4304                         insert_ptr(trans, fs_info, path, &disk_key,
4305                                    right->start, path->slots[1], 1);
4306                         btrfs_tree_unlock(path->nodes[0]);
4307                         free_extent_buffer(path->nodes[0]);
4308                         path->nodes[0] = right;
4309                         path->slots[0] = 0;
4310                         if (path->slots[1] == 0)
4311                                 fixup_low_keys(path, &disk_key, 1);
4312                 }
4313                 /*
4314                  * We create a new leaf 'right' for the required ins_len and
4315                  * we'll do btrfs_mark_buffer_dirty() on this leaf after copying
4316                  * the content of ins_len to 'right'.
4317                  */
4318                 return ret;
4319         }
4320
4321         copy_for_split(trans, fs_info, path, l, right, slot, mid, nritems);
4322
4323         if (split == 2) {
4324                 BUG_ON(num_doubles != 0);
4325                 num_doubles++;
4326                 goto again;
4327         }
4328
4329         return 0;
4330
4331 push_for_double:
4332         push_for_double_split(trans, root, path, data_size);
4333         tried_avoid_double = 1;
4334         if (btrfs_leaf_free_space(fs_info, path->nodes[0]) >= data_size)
4335                 return 0;
4336         goto again;
4337 }
4338
4339 static noinline int setup_leaf_for_split(struct btrfs_trans_handle *trans,
4340                                          struct btrfs_root *root,
4341                                          struct btrfs_path *path, int ins_len)
4342 {
4343         struct btrfs_fs_info *fs_info = root->fs_info;
4344         struct btrfs_key key;
4345         struct extent_buffer *leaf;
4346         struct btrfs_file_extent_item *fi;
4347         u64 extent_len = 0;
4348         u32 item_size;
4349         int ret;
4350
4351         leaf = path->nodes[0];
4352         btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4353
4354         BUG_ON(key.type != BTRFS_EXTENT_DATA_KEY &&
4355                key.type != BTRFS_EXTENT_CSUM_KEY);
4356
4357         if (btrfs_leaf_free_space(fs_info, leaf) >= ins_len)
4358                 return 0;
4359
4360         item_size = btrfs_item_size_nr(leaf, path->slots[0]);
4361         if (key.type == BTRFS_EXTENT_DATA_KEY) {
4362                 fi = btrfs_item_ptr(leaf, path->slots[0],
4363                                     struct btrfs_file_extent_item);
4364                 extent_len = btrfs_file_extent_num_bytes(leaf, fi);
4365         }
4366         btrfs_release_path(path);
4367
4368         path->keep_locks = 1;
4369         path->search_for_split = 1;
4370         ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
4371         path->search_for_split = 0;
4372         if (ret > 0)
4373                 ret = -EAGAIN;
4374         if (ret < 0)
4375                 goto err;
4376
4377         ret = -EAGAIN;
4378         leaf = path->nodes[0];
4379         /* if our item isn't there, return now */
4380         if (item_size != btrfs_item_size_nr(leaf, path->slots[0]))
4381                 goto err;
4382
4383         /* the leaf has  changed, it now has room.  return now */
4384         if (btrfs_leaf_free_space(fs_info, path->nodes[0]) >= ins_len)
4385                 goto err;
4386
4387         if (key.type == BTRFS_EXTENT_DATA_KEY) {
4388                 fi = btrfs_item_ptr(leaf, path->slots[0],
4389                                     struct btrfs_file_extent_item);
4390                 if (extent_len != btrfs_file_extent_num_bytes(leaf, fi))
4391                         goto err;
4392         }
4393
4394         btrfs_set_path_blocking(path);
4395         ret = split_leaf(trans, root, &key, path, ins_len, 1);
4396         if (ret)
4397                 goto err;
4398
4399         path->keep_locks = 0;
4400         btrfs_unlock_up_safe(path, 1);
4401         return 0;
4402 err:
4403         path->keep_locks = 0;
4404         return ret;
4405 }
4406
4407 static noinline int split_item(struct btrfs_fs_info *fs_info,
4408                                struct btrfs_path *path,
4409                                const struct btrfs_key *new_key,
4410                                unsigned long split_offset)
4411 {
4412         struct extent_buffer *leaf;
4413         struct btrfs_item *item;
4414         struct btrfs_item *new_item;
4415         int slot;
4416         char *buf;
4417         u32 nritems;
4418         u32 item_size;
4419         u32 orig_offset;
4420         struct btrfs_disk_key disk_key;
4421
4422         leaf = path->nodes[0];
4423         BUG_ON(btrfs_leaf_free_space(fs_info, leaf) < sizeof(struct btrfs_item));
4424
4425         btrfs_set_path_blocking(path);
4426
4427         item = btrfs_item_nr(path->slots[0]);
4428         orig_offset = btrfs_item_offset(leaf, item);
4429         item_size = btrfs_item_size(leaf, item);
4430
4431         buf = kmalloc(item_size, GFP_NOFS);
4432         if (!buf)
4433                 return -ENOMEM;
4434
4435         read_extent_buffer(leaf, buf, btrfs_item_ptr_offset(leaf,
4436                             path->slots[0]), item_size);
4437
4438         slot = path->slots[0] + 1;
4439         nritems = btrfs_header_nritems(leaf);
4440         if (slot != nritems) {
4441                 /* shift the items */
4442                 memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + 1),
4443                                 btrfs_item_nr_offset(slot),
4444                                 (nritems - slot) * sizeof(struct btrfs_item));
4445         }
4446
4447         btrfs_cpu_key_to_disk(&disk_key, new_key);
4448         btrfs_set_item_key(leaf, &disk_key, slot);
4449
4450         new_item = btrfs_item_nr(slot);
4451
4452         btrfs_set_item_offset(leaf, new_item, orig_offset);
4453         btrfs_set_item_size(leaf, new_item, item_size - split_offset);
4454
4455         btrfs_set_item_offset(leaf, item,
4456                               orig_offset + item_size - split_offset);
4457         btrfs_set_item_size(leaf, item, split_offset);
4458
4459         btrfs_set_header_nritems(leaf, nritems + 1);
4460
4461         /* write the data for the start of the original item */
4462         write_extent_buffer(leaf, buf,
4463                             btrfs_item_ptr_offset(leaf, path->slots[0]),
4464                             split_offset);
4465
4466         /* write the data for the new item */
4467         write_extent_buffer(leaf, buf + split_offset,
4468                             btrfs_item_ptr_offset(leaf, slot),
4469                             item_size - split_offset);
4470         btrfs_mark_buffer_dirty(leaf);
4471
4472         BUG_ON(btrfs_leaf_free_space(fs_info, leaf) < 0);
4473         kfree(buf);
4474         return 0;
4475 }
4476
4477 /*
4478  * This function splits a single item into two items,
4479  * giving 'new_key' to the new item and splitting the
4480  * old one at split_offset (from the start of the item).
4481  *
4482  * The path may be released by this operation.  After
4483  * the split, the path is pointing to the old item.  The
4484  * new item is going to be in the same node as the old one.
4485  *
4486  * Note, the item being split must be smaller enough to live alone on
4487  * a tree block with room for one extra struct btrfs_item
4488  *
4489  * This allows us to split the item in place, keeping a lock on the
4490  * leaf the entire time.
4491  */
4492 int btrfs_split_item(struct btrfs_trans_handle *trans,
4493                      struct btrfs_root *root,
4494                      struct btrfs_path *path,
4495                      const struct btrfs_key *new_key,
4496                      unsigned long split_offset)
4497 {
4498         int ret;
4499         ret = setup_leaf_for_split(trans, root, path,
4500                                    sizeof(struct btrfs_item));
4501         if (ret)
4502                 return ret;
4503
4504         ret = split_item(root->fs_info, path, new_key, split_offset);
4505         return ret;
4506 }
4507
4508 /*
4509  * This function duplicate a item, giving 'new_key' to the new item.
4510  * It guarantees both items live in the same tree leaf and the new item
4511  * is contiguous with the original item.
4512  *
4513  * This allows us to split file extent in place, keeping a lock on the
4514  * leaf the entire time.
4515  */
4516 int btrfs_duplicate_item(struct btrfs_trans_handle *trans,
4517                          struct btrfs_root *root,
4518                          struct btrfs_path *path,
4519                          const struct btrfs_key *new_key)
4520 {
4521         struct extent_buffer *leaf;
4522         int ret;
4523         u32 item_size;
4524
4525         leaf = path->nodes[0];
4526         item_size = btrfs_item_size_nr(leaf, path->slots[0]);
4527         ret = setup_leaf_for_split(trans, root, path,
4528                                    item_size + sizeof(struct btrfs_item));
4529         if (ret)
4530                 return ret;
4531
4532         path->slots[0]++;
4533         setup_items_for_insert(root, path, new_key, &item_size,
4534                                item_size, item_size +
4535                                sizeof(struct btrfs_item), 1);
4536         leaf = path->nodes[0];
4537         memcpy_extent_buffer(leaf,
4538                              btrfs_item_ptr_offset(leaf, path->slots[0]),
4539                              btrfs_item_ptr_offset(leaf, path->slots[0] - 1),
4540                              item_size);
4541         return 0;
4542 }
4543
4544 /*
4545  * make the item pointed to by the path smaller.  new_size indicates
4546  * how small to make it, and from_end tells us if we just chop bytes
4547  * off the end of the item or if we shift the item to chop bytes off
4548  * the front.
4549  */
4550 void btrfs_truncate_item(struct btrfs_fs_info *fs_info,
4551                          struct btrfs_path *path, u32 new_size, int from_end)
4552 {
4553         int slot;
4554         struct extent_buffer *leaf;
4555         struct btrfs_item *item;
4556         u32 nritems;
4557         unsigned int data_end;
4558         unsigned int old_data_start;
4559         unsigned int old_size;
4560         unsigned int size_diff;
4561         int i;
4562         struct btrfs_map_token token;
4563
4564         btrfs_init_map_token(&token);
4565
4566         leaf = path->nodes[0];
4567         slot = path->slots[0];
4568
4569         old_size = btrfs_item_size_nr(leaf, slot);
4570         if (old_size == new_size)
4571                 return;
4572
4573         nritems = btrfs_header_nritems(leaf);
4574         data_end = leaf_data_end(fs_info, leaf);
4575
4576         old_data_start = btrfs_item_offset_nr(leaf, slot);
4577
4578         size_diff = old_size - new_size;
4579
4580         BUG_ON(slot < 0);
4581         BUG_ON(slot >= nritems);
4582
4583         /*
4584          * item0..itemN ... dataN.offset..dataN.size .. data0.size
4585          */
4586         /* first correct the data pointers */
4587         for (i = slot; i < nritems; i++) {
4588                 u32 ioff;
4589                 item = btrfs_item_nr(i);
4590
4591                 ioff = btrfs_token_item_offset(leaf, item, &token);
4592                 btrfs_set_token_item_offset(leaf, item,
4593                                             ioff + size_diff, &token);
4594         }
4595
4596         /* shift the data */
4597         if (from_end) {
4598                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4599                               data_end + size_diff, BTRFS_LEAF_DATA_OFFSET +
4600                               data_end, old_data_start + new_size - data_end);
4601         } else {
4602                 struct btrfs_disk_key disk_key;
4603                 u64 offset;
4604
4605                 btrfs_item_key(leaf, &disk_key, slot);
4606
4607                 if (btrfs_disk_key_type(&disk_key) == BTRFS_EXTENT_DATA_KEY) {
4608                         unsigned long ptr;
4609                         struct btrfs_file_extent_item *fi;
4610
4611                         fi = btrfs_item_ptr(leaf, slot,
4612                                             struct btrfs_file_extent_item);
4613                         fi = (struct btrfs_file_extent_item *)(
4614                              (unsigned long)fi - size_diff);
4615
4616                         if (btrfs_file_extent_type(leaf, fi) ==
4617                             BTRFS_FILE_EXTENT_INLINE) {
4618                                 ptr = btrfs_item_ptr_offset(leaf, slot);
4619                                 memmove_extent_buffer(leaf, ptr,
4620                                       (unsigned long)fi,
4621                                       BTRFS_FILE_EXTENT_INLINE_DATA_START);
4622                         }
4623                 }
4624
4625                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4626                               data_end + size_diff, BTRFS_LEAF_DATA_OFFSET +
4627                               data_end, old_data_start - data_end);
4628
4629                 offset = btrfs_disk_key_offset(&disk_key);
4630                 btrfs_set_disk_key_offset(&disk_key, offset + size_diff);
4631                 btrfs_set_item_key(leaf, &disk_key, slot);
4632                 if (slot == 0)
4633                         fixup_low_keys(path, &disk_key, 1);
4634         }
4635
4636         item = btrfs_item_nr(slot);
4637         btrfs_set_item_size(leaf, item, new_size);
4638         btrfs_mark_buffer_dirty(leaf);
4639
4640         if (btrfs_leaf_free_space(fs_info, leaf) < 0) {
4641                 btrfs_print_leaf(leaf);
4642                 BUG();
4643         }
4644 }
4645
4646 /*
4647  * make the item pointed to by the path bigger, data_size is the added size.
4648  */
4649 void btrfs_extend_item(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
4650                        u32 data_size)
4651 {
4652         int slot;
4653         struct extent_buffer *leaf;
4654         struct btrfs_item *item;
4655         u32 nritems;
4656         unsigned int data_end;
4657         unsigned int old_data;
4658         unsigned int old_size;
4659         int i;
4660         struct btrfs_map_token token;
4661
4662         btrfs_init_map_token(&token);
4663
4664         leaf = path->nodes[0];
4665
4666         nritems = btrfs_header_nritems(leaf);
4667         data_end = leaf_data_end(fs_info, leaf);
4668
4669         if (btrfs_leaf_free_space(fs_info, leaf) < data_size) {
4670                 btrfs_print_leaf(leaf);
4671                 BUG();
4672         }
4673         slot = path->slots[0];
4674         old_data = btrfs_item_end_nr(leaf, slot);
4675
4676         BUG_ON(slot < 0);
4677         if (slot >= nritems) {
4678                 btrfs_print_leaf(leaf);
4679                 btrfs_crit(fs_info, "slot %d too large, nritems %d",
4680                            slot, nritems);
4681                 BUG_ON(1);
4682         }
4683
4684         /*
4685          * item0..itemN ... dataN.offset..dataN.size .. data0.size
4686          */
4687         /* first correct the data pointers */
4688         for (i = slot; i < nritems; i++) {
4689                 u32 ioff;
4690                 item = btrfs_item_nr(i);
4691
4692                 ioff = btrfs_token_item_offset(leaf, item, &token);
4693                 btrfs_set_token_item_offset(leaf, item,
4694                                             ioff - data_size, &token);
4695         }
4696
4697         /* shift the data */
4698         memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4699                       data_end - data_size, BTRFS_LEAF_DATA_OFFSET +
4700                       data_end, old_data - data_end);
4701
4702         data_end = old_data;
4703         old_size = btrfs_item_size_nr(leaf, slot);
4704         item = btrfs_item_nr(slot);
4705         btrfs_set_item_size(leaf, item, old_size + data_size);
4706         btrfs_mark_buffer_dirty(leaf);
4707
4708         if (btrfs_leaf_free_space(fs_info, leaf) < 0) {
4709                 btrfs_print_leaf(leaf);
4710                 BUG();
4711         }
4712 }
4713
4714 /*
4715  * this is a helper for btrfs_insert_empty_items, the main goal here is
4716  * to save stack depth by doing the bulk of the work in a function
4717  * that doesn't call btrfs_search_slot
4718  */
4719 void setup_items_for_insert(struct btrfs_root *root, struct btrfs_path *path,
4720                             const struct btrfs_key *cpu_key, u32 *data_size,
4721                             u32 total_data, u32 total_size, int nr)
4722 {
4723         struct btrfs_fs_info *fs_info = root->fs_info;
4724         struct btrfs_item *item;
4725         int i;
4726         u32 nritems;
4727         unsigned int data_end;
4728         struct btrfs_disk_key disk_key;
4729         struct extent_buffer *leaf;
4730         int slot;
4731         struct btrfs_map_token token;
4732
4733         if (path->slots[0] == 0) {
4734                 btrfs_cpu_key_to_disk(&disk_key, cpu_key);
4735                 fixup_low_keys(path, &disk_key, 1);
4736         }
4737         btrfs_unlock_up_safe(path, 1);
4738
4739         btrfs_init_map_token(&token);
4740
4741         leaf = path->nodes[0];
4742         slot = path->slots[0];
4743
4744         nritems = btrfs_header_nritems(leaf);
4745         data_end = leaf_data_end(fs_info, leaf);
4746
4747         if (btrfs_leaf_free_space(fs_info, leaf) < total_size) {
4748                 btrfs_print_leaf(leaf);
4749                 btrfs_crit(fs_info, "not enough freespace need %u have %d",
4750                            total_size, btrfs_leaf_free_space(fs_info, leaf));
4751                 BUG();
4752         }
4753
4754         if (slot != nritems) {
4755                 unsigned int old_data = btrfs_item_end_nr(leaf, slot);
4756
4757                 if (old_data < data_end) {
4758                         btrfs_print_leaf(leaf);
4759                         btrfs_crit(fs_info, "slot %d old_data %d data_end %d",
4760                                    slot, old_data, data_end);
4761                         BUG_ON(1);
4762                 }
4763                 /*
4764                  * item0..itemN ... dataN.offset..dataN.size .. data0.size
4765                  */
4766                 /* first correct the data pointers */
4767                 for (i = slot; i < nritems; i++) {
4768                         u32 ioff;
4769
4770                         item = btrfs_item_nr(i);
4771                         ioff = btrfs_token_item_offset(leaf, item, &token);
4772                         btrfs_set_token_item_offset(leaf, item,
4773                                                     ioff - total_data, &token);
4774                 }
4775                 /* shift the items */
4776                 memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + nr),
4777                               btrfs_item_nr_offset(slot),
4778                               (nritems - slot) * sizeof(struct btrfs_item));
4779
4780                 /* shift the data */
4781                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4782                               data_end - total_data, BTRFS_LEAF_DATA_OFFSET +
4783                               data_end, old_data - data_end);
4784                 data_end = old_data;
4785         }
4786
4787         /* setup the item for the new data */
4788         for (i = 0; i < nr; i++) {
4789                 btrfs_cpu_key_to_disk(&disk_key, cpu_key + i);
4790                 btrfs_set_item_key(leaf, &disk_key, slot + i);
4791                 item = btrfs_item_nr(slot + i);
4792                 btrfs_set_token_item_offset(leaf, item,
4793                                             data_end - data_size[i], &token);
4794                 data_end -= data_size[i];
4795                 btrfs_set_token_item_size(leaf, item, data_size[i], &token);
4796         }
4797
4798         btrfs_set_header_nritems(leaf, nritems + nr);
4799         btrfs_mark_buffer_dirty(leaf);
4800
4801         if (btrfs_leaf_free_space(fs_info, leaf) < 0) {
4802                 btrfs_print_leaf(leaf);
4803                 BUG();
4804         }
4805 }
4806
4807 /*
4808  * Given a key and some data, insert items into the tree.
4809  * This does all the path init required, making room in the tree if needed.
4810  */
4811 int btrfs_insert_empty_items(struct btrfs_trans_handle *trans,
4812                             struct btrfs_root *root,
4813                             struct btrfs_path *path,
4814                             const struct btrfs_key *cpu_key, u32 *data_size,
4815                             int nr)
4816 {
4817         int ret = 0;
4818         int slot;
4819         int i;
4820         u32 total_size = 0;
4821         u32 total_data = 0;
4822
4823         for (i = 0; i < nr; i++)
4824                 total_data += data_size[i];
4825
4826         total_size = total_data + (nr * sizeof(struct btrfs_item));
4827         ret = btrfs_search_slot(trans, root, cpu_key, path, total_size, 1);
4828         if (ret == 0)
4829                 return -EEXIST;
4830         if (ret < 0)
4831                 return ret;
4832
4833         slot = path->slots[0];
4834         BUG_ON(slot < 0);
4835
4836         setup_items_for_insert(root, path, cpu_key, data_size,
4837                                total_data, total_size, nr);
4838         return 0;
4839 }
4840
4841 /*
4842  * Given a key and some data, insert an item into the tree.
4843  * This does all the path init required, making room in the tree if needed.
4844  */
4845 int btrfs_insert_item(struct btrfs_trans_handle *trans, struct btrfs_root *root,
4846                       const struct btrfs_key *cpu_key, void *data,
4847                       u32 data_size)
4848 {
4849         int ret = 0;
4850         struct btrfs_path *path;
4851         struct extent_buffer *leaf;
4852         unsigned long ptr;
4853
4854         path = btrfs_alloc_path();
4855         if (!path)
4856                 return -ENOMEM;
4857         ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
4858         if (!ret) {
4859                 leaf = path->nodes[0];
4860                 ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
4861                 write_extent_buffer(leaf, data, ptr, data_size);
4862                 btrfs_mark_buffer_dirty(leaf);
4863         }
4864         btrfs_free_path(path);
4865         return ret;
4866 }
4867
4868 /*
4869  * delete the pointer from a given node.
4870  *
4871  * the tree should have been previously balanced so the deletion does not
4872  * empty a node.
4873  */
4874 static void del_ptr(struct btrfs_root *root, struct btrfs_path *path,
4875                     int level, int slot)
4876 {
4877         struct extent_buffer *parent = path->nodes[level];
4878         u32 nritems;
4879         int ret;
4880
4881         nritems = btrfs_header_nritems(parent);
4882         if (slot != nritems - 1) {
4883                 if (level) {
4884                         ret = tree_mod_log_insert_move(parent, slot, slot + 1,
4885                                         nritems - slot - 1);
4886                         BUG_ON(ret < 0);
4887                 }
4888                 memmove_extent_buffer(parent,
4889                               btrfs_node_key_ptr_offset(slot),
4890                               btrfs_node_key_ptr_offset(slot + 1),
4891                               sizeof(struct btrfs_key_ptr) *
4892                               (nritems - slot - 1));
4893         } else if (level) {
4894                 ret = tree_mod_log_insert_key(parent, slot, MOD_LOG_KEY_REMOVE,
4895                                 GFP_NOFS);
4896                 BUG_ON(ret < 0);
4897         }
4898
4899         nritems--;
4900         btrfs_set_header_nritems(parent, nritems);
4901         if (nritems == 0 && parent == root->node) {
4902                 BUG_ON(btrfs_header_level(root->node) != 1);
4903                 /* just turn the root into a leaf and break */
4904                 btrfs_set_header_level(root->node, 0);
4905         } else if (slot == 0) {
4906                 struct btrfs_disk_key disk_key;
4907
4908                 btrfs_node_key(parent, &disk_key, 0);
4909                 fixup_low_keys(path, &disk_key, level + 1);
4910         }
4911         btrfs_mark_buffer_dirty(parent);
4912 }
4913
4914 /*
4915  * a helper function to delete the leaf pointed to by path->slots[1] and
4916  * path->nodes[1].
4917  *
4918  * This deletes the pointer in path->nodes[1] and frees the leaf
4919  * block extent.  zero is returned if it all worked out, < 0 otherwise.
4920  *
4921  * The path must have already been setup for deleting the leaf, including
4922  * all the proper balancing.  path->nodes[1] must be locked.
4923  */
4924 static noinline void btrfs_del_leaf(struct btrfs_trans_handle *trans,
4925                                     struct btrfs_root *root,
4926                                     struct btrfs_path *path,
4927                                     struct extent_buffer *leaf)
4928 {
4929         WARN_ON(btrfs_header_generation(leaf) != trans->transid);
4930         del_ptr(root, path, 1, path->slots[1]);
4931
4932         /*
4933          * btrfs_free_extent is expensive, we want to make sure we
4934          * aren't holding any locks when we call it
4935          */
4936         btrfs_unlock_up_safe(path, 0);
4937
4938         root_sub_used(root, leaf->len);
4939
4940         extent_buffer_get(leaf);
4941         btrfs_free_tree_block(trans, root, leaf, 0, 1);
4942         free_extent_buffer_stale(leaf);
4943 }
4944 /*
4945  * delete the item at the leaf level in path.  If that empties
4946  * the leaf, remove it from the tree
4947  */
4948 int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root,
4949                     struct btrfs_path *path, int slot, int nr)
4950 {
4951         struct btrfs_fs_info *fs_info = root->fs_info;
4952         struct extent_buffer *leaf;
4953         struct btrfs_item *item;
4954         u32 last_off;
4955         u32 dsize = 0;
4956         int ret = 0;
4957         int wret;
4958         int i;
4959         u32 nritems;
4960         struct btrfs_map_token token;
4961
4962         btrfs_init_map_token(&token);
4963
4964         leaf = path->nodes[0];
4965         last_off = btrfs_item_offset_nr(leaf, slot + nr - 1);
4966
4967         for (i = 0; i < nr; i++)
4968                 dsize += btrfs_item_size_nr(leaf, slot + i);
4969
4970         nritems = btrfs_header_nritems(leaf);
4971
4972         if (slot + nr != nritems) {
4973                 int data_end = leaf_data_end(fs_info, leaf);
4974
4975                 memmove_extent_buffer(leaf, BTRFS_LEAF_DATA_OFFSET +
4976                               data_end + dsize,
4977                               BTRFS_LEAF_DATA_OFFSET + data_end,
4978                               last_off - data_end);
4979
4980                 for (i = slot + nr; i < nritems; i++) {
4981                         u32 ioff;
4982
4983                         item = btrfs_item_nr(i);
4984                         ioff = btrfs_token_item_offset(leaf, item, &token);
4985                         btrfs_set_token_item_offset(leaf, item,
4986                                                     ioff + dsize, &token);
4987                 }
4988
4989                 memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot),
4990                               btrfs_item_nr_offset(slot + nr),
4991                               sizeof(struct btrfs_item) *
4992                               (nritems - slot - nr));
4993         }
4994         btrfs_set_header_nritems(leaf, nritems - nr);
4995         nritems -= nr;
4996
4997         /* delete the leaf if we've emptied it */
4998         if (nritems == 0) {
4999                 if (leaf == root->node) {
5000                         btrfs_set_header_level(leaf, 0);
5001                 } else {
5002                         btrfs_set_path_blocking(path);
5003                         clean_tree_block(fs_info, leaf);
5004                         btrfs_del_leaf(trans, root, path, leaf);
5005                 }
5006         } else {
5007                 int used = leaf_space_used(leaf, 0, nritems);
5008                 if (slot == 0) {
5009                         struct btrfs_disk_key disk_key;
5010
5011                         btrfs_item_key(leaf, &disk_key, 0);
5012                         fixup_low_keys(path, &disk_key, 1);
5013                 }
5014
5015                 /* delete the leaf if it is mostly empty */
5016                 if (used < BTRFS_LEAF_DATA_SIZE(fs_info) / 3) {
5017                         /* push_leaf_left fixes the path.
5018                          * make sure the path still points to our leaf
5019                          * for possible call to del_ptr below
5020                          */
5021                         slot = path->slots[1];
5022                         extent_buffer_get(leaf);
5023
5024                         btrfs_set_path_blocking(path);
5025                         wret = push_leaf_left(trans, root, path, 1, 1,
5026                                               1, (u32)-1);
5027                         if (wret < 0 && wret != -ENOSPC)
5028                                 ret = wret;
5029
5030                         if (path->nodes[0] == leaf &&
5031                             btrfs_header_nritems(leaf)) {
5032                                 wret = push_leaf_right(trans, root, path, 1,
5033                                                        1, 1, 0);
5034                                 if (wret < 0 && wret != -ENOSPC)
5035                                         ret = wret;
5036                         }
5037
5038                         if (btrfs_header_nritems(leaf) == 0) {
5039                                 path->slots[1] = slot;
5040                                 btrfs_del_leaf(trans, root, path, leaf);
5041                                 free_extent_buffer(leaf);
5042                                 ret = 0;
5043                         } else {
5044                                 /* if we're still in the path, make sure
5045                                  * we're dirty.  Otherwise, one of the
5046                                  * push_leaf functions must have already
5047                                  * dirtied this buffer
5048                                  */
5049                                 if (path->nodes[0] == leaf)
5050                                         btrfs_mark_buffer_dirty(leaf);
5051                                 free_extent_buffer(leaf);
5052                         }
5053                 } else {
5054                         btrfs_mark_buffer_dirty(leaf);
5055                 }
5056         }
5057         return ret;
5058 }
5059
5060 /*
5061  * search the tree again to find a leaf with lesser keys
5062  * returns 0 if it found something or 1 if there are no lesser leaves.
5063  * returns < 0 on io errors.
5064  *
5065  * This may release the path, and so you may lose any locks held at the
5066  * time you call it.
5067  */
5068 int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path)
5069 {
5070         struct btrfs_key key;
5071         struct btrfs_disk_key found_key;
5072         int ret;
5073
5074         btrfs_item_key_to_cpu(path->nodes[0], &key, 0);
5075
5076         if (key.offset > 0) {
5077                 key.offset--;
5078         } else if (key.type > 0) {
5079                 key.type--;
5080                 key.offset = (u64)-1;
5081         } else if (key.objectid > 0) {
5082                 key.objectid--;
5083                 key.type = (u8)-1;
5084                 key.offset = (u64)-1;
5085         } else {
5086                 return 1;
5087         }
5088
5089         btrfs_release_path(path);
5090         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
5091         if (ret < 0)
5092                 return ret;
5093         btrfs_item_key(path->nodes[0], &found_key, 0);
5094         ret = comp_keys(&found_key, &key);
5095         /*
5096          * We might have had an item with the previous key in the tree right
5097          * before we released our path. And after we released our path, that
5098          * item might have been pushed to the first slot (0) of the leaf we
5099          * were holding due to a tree balance. Alternatively, an item with the
5100          * previous key can exist as the only element of a leaf (big fat item).
5101          * Therefore account for these 2 cases, so that our callers (like
5102          * btrfs_previous_item) don't miss an existing item with a key matching
5103          * the previous key we computed above.
5104          */
5105         if (ret <= 0)
5106                 return 0;
5107         return 1;
5108 }
5109
5110 /*
5111  * A helper function to walk down the tree starting at min_key, and looking
5112  * for nodes or leaves that are have a minimum transaction id.
5113  * This is used by the btree defrag code, and tree logging
5114  *
5115  * This does not cow, but it does stuff the starting key it finds back
5116  * into min_key, so you can call btrfs_search_slot with cow=1 on the
5117  * key and get a writable path.
5118  *
5119  * This honors path->lowest_level to prevent descent past a given level
5120  * of the tree.
5121  *
5122  * min_trans indicates the oldest transaction that you are interested
5123  * in walking through.  Any nodes or leaves older than min_trans are
5124  * skipped over (without reading them).
5125  *
5126  * returns zero if something useful was found, < 0 on error and 1 if there
5127  * was nothing in the tree that matched the search criteria.
5128  */
5129 int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
5130                          struct btrfs_path *path,
5131                          u64 min_trans)
5132 {
5133         struct btrfs_fs_info *fs_info = root->fs_info;
5134         struct extent_buffer *cur;
5135         struct btrfs_key found_key;
5136         int slot;
5137         int sret;
5138         u32 nritems;
5139         int level;
5140         int ret = 1;
5141         int keep_locks = path->keep_locks;
5142
5143         path->keep_locks = 1;
5144 again:
5145         cur = btrfs_read_lock_root_node(root);
5146         level = btrfs_header_level(cur);
5147         WARN_ON(path->nodes[level]);
5148         path->nodes[level] = cur;
5149         path->locks[level] = BTRFS_READ_LOCK;
5150
5151         if (btrfs_header_generation(cur) < min_trans) {
5152                 ret = 1;
5153                 goto out;
5154         }
5155         while (1) {
5156                 nritems = btrfs_header_nritems(cur);
5157                 level = btrfs_header_level(cur);
5158                 sret = btrfs_bin_search(cur, min_key, level, &slot);
5159
5160                 /* at the lowest level, we're done, setup the path and exit */
5161                 if (level == path->lowest_level) {
5162                         if (slot >= nritems)
5163                                 goto find_next_key;
5164                         ret = 0;
5165                         path->slots[level] = slot;
5166                         btrfs_item_key_to_cpu(cur, &found_key, slot);
5167                         goto out;
5168                 }
5169                 if (sret && slot > 0)
5170                         slot--;
5171                 /*
5172                  * check this node pointer against the min_trans parameters.
5173                  * If it is too old, old, skip to the next one.
5174                  */
5175                 while (slot < nritems) {
5176                         u64 gen;
5177
5178                         gen = btrfs_node_ptr_generation(cur, slot);
5179                         if (gen < min_trans) {
5180                                 slot++;
5181                                 continue;
5182                         }
5183                         break;
5184                 }
5185 find_next_key:
5186                 /*
5187                  * we didn't find a candidate key in this node, walk forward
5188                  * and find another one
5189                  */
5190                 if (slot >= nritems) {
5191                         path->slots[level] = slot;
5192                         btrfs_set_path_blocking(path);
5193                         sret = btrfs_find_next_key(root, path, min_key, level,
5194                                                   min_trans);
5195                         if (sret == 0) {
5196                                 btrfs_release_path(path);
5197                                 goto again;
5198                         } else {
5199                                 goto out;
5200                         }
5201                 }
5202                 /* save our key for returning back */
5203                 btrfs_node_key_to_cpu(cur, &found_key, slot);
5204                 path->slots[level] = slot;
5205                 if (level == path->lowest_level) {
5206                         ret = 0;
5207                         goto out;
5208                 }
5209                 btrfs_set_path_blocking(path);
5210                 cur = read_node_slot(fs_info, cur, slot);
5211                 if (IS_ERR(cur)) {
5212                         ret = PTR_ERR(cur);
5213                         goto out;
5214                 }
5215
5216                 btrfs_tree_read_lock(cur);
5217
5218                 path->locks[level - 1] = BTRFS_READ_LOCK;
5219                 path->nodes[level - 1] = cur;
5220                 unlock_up(path, level, 1, 0, NULL);
5221         }
5222 out:
5223         path->keep_locks = keep_locks;
5224         if (ret == 0) {
5225                 btrfs_unlock_up_safe(path, path->lowest_level + 1);
5226                 btrfs_set_path_blocking(path);
5227                 memcpy(min_key, &found_key, sizeof(found_key));
5228         }
5229         return ret;
5230 }
5231
5232 static int tree_move_down(struct btrfs_fs_info *fs_info,
5233                            struct btrfs_path *path,
5234                            int *level)
5235 {
5236         struct extent_buffer *eb;
5237
5238         BUG_ON(*level == 0);
5239         eb = read_node_slot(fs_info, path->nodes[*level], path->slots[*level]);
5240         if (IS_ERR(eb))
5241                 return PTR_ERR(eb);
5242
5243         path->nodes[*level - 1] = eb;
5244         path->slots[*level - 1] = 0;
5245         (*level)--;
5246         return 0;
5247 }
5248
5249 static int tree_move_next_or_upnext(struct btrfs_path *path,
5250                                     int *level, int root_level)
5251 {
5252         int ret = 0;
5253         int nritems;
5254         nritems = btrfs_header_nritems(path->nodes[*level]);
5255
5256         path->slots[*level]++;
5257
5258         while (path->slots[*level] >= nritems) {
5259                 if (*level == root_level)
5260                         return -1;
5261
5262                 /* move upnext */
5263                 path->slots[*level] = 0;
5264                 free_extent_buffer(path->nodes[*level]);
5265                 path->nodes[*level] = NULL;
5266                 (*level)++;
5267                 path->slots[*level]++;
5268
5269                 nritems = btrfs_header_nritems(path->nodes[*level]);
5270                 ret = 1;
5271         }
5272         return ret;
5273 }
5274
5275 /*
5276  * Returns 1 if it had to move up and next. 0 is returned if it moved only next
5277  * or down.
5278  */
5279 static int tree_advance(struct btrfs_fs_info *fs_info,
5280                         struct btrfs_path *path,
5281                         int *level, int root_level,
5282                         int allow_down,
5283                         struct btrfs_key *key)
5284 {
5285         int ret;
5286
5287         if (*level == 0 || !allow_down) {
5288                 ret = tree_move_next_or_upnext(path, level, root_level);
5289         } else {
5290                 ret = tree_move_down(fs_info, path, level);
5291         }
5292         if (ret >= 0) {
5293                 if (*level == 0)
5294                         btrfs_item_key_to_cpu(path->nodes[*level], key,
5295                                         path->slots[*level]);
5296                 else
5297                         btrfs_node_key_to_cpu(path->nodes[*level], key,
5298                                         path->slots[*level]);
5299         }
5300         return ret;
5301 }
5302
5303 static int tree_compare_item(struct btrfs_path *left_path,
5304                              struct btrfs_path *right_path,
5305                              char *tmp_buf)
5306 {
5307         int cmp;
5308         int len1, len2;
5309         unsigned long off1, off2;
5310
5311         len1 = btrfs_item_size_nr(left_path->nodes[0], left_path->slots[0]);
5312         len2 = btrfs_item_size_nr(right_path->nodes[0], right_path->slots[0]);
5313         if (len1 != len2)
5314                 return 1;
5315
5316         off1 = btrfs_item_ptr_offset(left_path->nodes[0], left_path->slots[0]);
5317         off2 = btrfs_item_ptr_offset(right_path->nodes[0],
5318                                 right_path->slots[0]);
5319
5320         read_extent_buffer(left_path->nodes[0], tmp_buf, off1, len1);
5321
5322         cmp = memcmp_extent_buffer(right_path->nodes[0], tmp_buf, off2, len1);
5323         if (cmp)
5324                 return 1;
5325         return 0;
5326 }
5327
5328 #define ADVANCE 1
5329 #define ADVANCE_ONLY_NEXT -1
5330
5331 /*
5332  * This function compares two trees and calls the provided callback for
5333  * every changed/new/deleted item it finds.
5334  * If shared tree blocks are encountered, whole subtrees are skipped, making
5335  * the compare pretty fast on snapshotted subvolumes.
5336  *
5337  * This currently works on commit roots only. As commit roots are read only,
5338  * we don't do any locking. The commit roots are protected with transactions.
5339  * Transactions are ended and rejoined when a commit is tried in between.
5340  *
5341  * This function checks for modifications done to the trees while comparing.
5342  * If it detects a change, it aborts immediately.
5343  */
5344 int btrfs_compare_trees(struct btrfs_root *left_root,
5345                         struct btrfs_root *right_root,
5346                         btrfs_changed_cb_t changed_cb, void *ctx)
5347 {
5348         struct btrfs_fs_info *fs_info = left_root->fs_info;
5349         int ret;
5350         int cmp;
5351         struct btrfs_path *left_path = NULL;
5352         struct btrfs_path *right_path = NULL;
5353         struct btrfs_key left_key;
5354         struct btrfs_key right_key;
5355         char *tmp_buf = NULL;
5356         int left_root_level;
5357         int right_root_level;
5358         int left_level;
5359         int right_level;
5360         int left_end_reached;
5361         int right_end_reached;
5362         int advance_left;
5363         int advance_right;
5364         u64 left_blockptr;
5365         u64 right_blockptr;
5366         u64 left_gen;
5367         u64 right_gen;
5368
5369         left_path = btrfs_alloc_path();
5370         if (!left_path) {
5371                 ret = -ENOMEM;
5372                 goto out;
5373         }
5374         right_path = btrfs_alloc_path();
5375         if (!right_path) {
5376                 ret = -ENOMEM;
5377                 goto out;
5378         }
5379
5380         tmp_buf = kvmalloc(fs_info->nodesize, GFP_KERNEL);
5381         if (!tmp_buf) {
5382                 ret = -ENOMEM;
5383                 goto out;
5384         }
5385
5386         left_path->search_commit_root = 1;
5387         left_path->skip_locking = 1;
5388         right_path->search_commit_root = 1;
5389         right_path->skip_locking = 1;
5390
5391         /*
5392          * Strategy: Go to the first items of both trees. Then do
5393          *
5394          * If both trees are at level 0
5395          *   Compare keys of current items
5396          *     If left < right treat left item as new, advance left tree
5397          *       and repeat
5398          *     If left > right treat right item as deleted, advance right tree
5399          *       and repeat
5400          *     If left == right do deep compare of items, treat as changed if
5401          *       needed, advance both trees and repeat
5402          * If both trees are at the same level but not at level 0
5403          *   Compare keys of current nodes/leafs
5404          *     If left < right advance left tree and repeat
5405          *     If left > right advance right tree and repeat
5406          *     If left == right compare blockptrs of the next nodes/leafs
5407          *       If they match advance both trees but stay at the same level
5408          *         and repeat
5409          *       If they don't match advance both trees while allowing to go
5410          *         deeper and repeat
5411          * If tree levels are different
5412          *   Advance the tree that needs it and repeat
5413          *
5414          * Advancing a tree means:
5415          *   If we are at level 0, try to go to the next slot. If that's not
5416          *   possible, go one level up and repeat. Stop when we found a level
5417          *   where we could go to the next slot. We may at this point be on a
5418          *   node or a leaf.
5419          *
5420          *   If we are not at level 0 and not on shared tree blocks, go one
5421          *   level deeper.
5422          *
5423          *   If we are not at level 0 and on shared tree blocks, go one slot to
5424          *   the right if possible or go up and right.
5425          */
5426
5427         down_read(&fs_info->commit_root_sem);
5428         left_level = btrfs_header_level(left_root->commit_root);
5429         left_root_level = left_level;
5430         left_path->nodes[left_level] =
5431                         btrfs_clone_extent_buffer(left_root->commit_root);
5432         if (!left_path->nodes[left_level]) {
5433                 up_read(&fs_info->commit_root_sem);
5434                 ret = -ENOMEM;
5435                 goto out;
5436         }
5437
5438         right_level = btrfs_header_level(right_root->commit_root);
5439         right_root_level = right_level;
5440         right_path->nodes[right_level] =
5441                         btrfs_clone_extent_buffer(right_root->commit_root);
5442         if (!right_path->nodes[right_level]) {
5443                 up_read(&fs_info->commit_root_sem);
5444                 ret = -ENOMEM;
5445                 goto out;
5446         }
5447         up_read(&fs_info->commit_root_sem);
5448
5449         if (left_level == 0)
5450                 btrfs_item_key_to_cpu(left_path->nodes[left_level],
5451                                 &left_key, left_path->slots[left_level]);
5452         else
5453                 btrfs_node_key_to_cpu(left_path->nodes[left_level],
5454                                 &left_key, left_path->slots[left_level]);
5455         if (right_level == 0)
5456                 btrfs_item_key_to_cpu(right_path->nodes[right_level],
5457                                 &right_key, right_path->slots[right_level]);
5458         else
5459                 btrfs_node_key_to_cpu(right_path->nodes[right_level],
5460                                 &right_key, right_path->slots[right_level]);
5461
5462         left_end_reached = right_end_reached = 0;
5463         advance_left = advance_right = 0;
5464
5465         while (1) {
5466                 if (advance_left && !left_end_reached) {
5467                         ret = tree_advance(fs_info, left_path, &left_level,
5468                                         left_root_level,
5469                                         advance_left != ADVANCE_ONLY_NEXT,
5470                                         &left_key);
5471                         if (ret == -1)
5472                                 left_end_reached = ADVANCE;
5473                         else if (ret < 0)
5474                                 goto out;
5475                         advance_left = 0;
5476                 }
5477                 if (advance_right && !right_end_reached) {
5478                         ret = tree_advance(fs_info, right_path, &right_level,
5479                                         right_root_level,
5480                                         advance_right != ADVANCE_ONLY_NEXT,
5481                                         &right_key);
5482                         if (ret == -1)
5483                                 right_end_reached = ADVANCE;
5484                         else if (ret < 0)
5485                                 goto out;
5486                         advance_right = 0;
5487                 }
5488
5489                 if (left_end_reached && right_end_reached) {
5490                         ret = 0;
5491                         goto out;
5492                 } else if (left_end_reached) {
5493                         if (right_level == 0) {
5494                                 ret = changed_cb(left_path, right_path,
5495                                                 &right_key,
5496                                                 BTRFS_COMPARE_TREE_DELETED,
5497                                                 ctx);
5498                                 if (ret < 0)
5499                                         goto out;
5500                         }
5501                         advance_right = ADVANCE;
5502                         continue;
5503                 } else if (right_end_reached) {
5504                         if (left_level == 0) {
5505                                 ret = changed_cb(left_path, right_path,
5506                                                 &left_key,
5507                                                 BTRFS_COMPARE_TREE_NEW,
5508                                                 ctx);
5509                                 if (ret < 0)
5510                                         goto out;
5511                         }
5512                         advance_left = ADVANCE;
5513                         continue;
5514                 }
5515
5516                 if (left_level == 0 && right_level == 0) {
5517                         cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
5518                         if (cmp < 0) {
5519                                 ret = changed_cb(left_path, right_path,
5520                                                 &left_key,
5521                                                 BTRFS_COMPARE_TREE_NEW,
5522                                                 ctx);
5523                                 if (ret < 0)
5524                                         goto out;
5525                                 advance_left = ADVANCE;
5526                         } else if (cmp > 0) {
5527                                 ret = changed_cb(left_path, right_path,
5528                                                 &right_key,
5529                                                 BTRFS_COMPARE_TREE_DELETED,
5530                                                 ctx);
5531                                 if (ret < 0)
5532                                         goto out;
5533                                 advance_right = ADVANCE;
5534                         } else {
5535                                 enum btrfs_compare_tree_result result;
5536
5537                                 WARN_ON(!extent_buffer_uptodate(left_path->nodes[0]));
5538                                 ret = tree_compare_item(left_path, right_path,
5539                                                         tmp_buf);
5540                                 if (ret)
5541                                         result = BTRFS_COMPARE_TREE_CHANGED;
5542                                 else
5543                                         result = BTRFS_COMPARE_TREE_SAME;
5544                                 ret = changed_cb(left_path, right_path,
5545                                                  &left_key, result, ctx);
5546                                 if (ret < 0)
5547                                         goto out;
5548                                 advance_left = ADVANCE;
5549                                 advance_right = ADVANCE;
5550                         }
5551                 } else if (left_level == right_level) {
5552                         cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
5553                         if (cmp < 0) {
5554                                 advance_left = ADVANCE;
5555                         } else if (cmp > 0) {
5556                                 advance_right = ADVANCE;
5557                         } else {
5558                                 left_blockptr = btrfs_node_blockptr(
5559                                                 left_path->nodes[left_level],
5560                                                 left_path->slots[left_level]);
5561                                 right_blockptr = btrfs_node_blockptr(
5562                                                 right_path->nodes[right_level],
5563                                                 right_path->slots[right_level]);
5564                                 left_gen = btrfs_node_ptr_generation(
5565                                                 left_path->nodes[left_level],
5566                                                 left_path->slots[left_level]);
5567                                 right_gen = btrfs_node_ptr_generation(
5568                                                 right_path->nodes[right_level],
5569                                                 right_path->slots[right_level]);
5570                                 if (left_blockptr == right_blockptr &&
5571                                     left_gen == right_gen) {
5572                                         /*
5573                                          * As we're on a shared block, don't
5574                                          * allow to go deeper.
5575                                          */
5576                                         advance_left = ADVANCE_ONLY_NEXT;
5577                                         advance_right = ADVANCE_ONLY_NEXT;
5578                                 } else {
5579                                         advance_left = ADVANCE;
5580                                         advance_right = ADVANCE;
5581                                 }
5582                         }
5583                 } else if (left_level < right_level) {
5584                         advance_right = ADVANCE;
5585                 } else {
5586                         advance_left = ADVANCE;
5587                 }
5588         }
5589
5590 out:
5591         btrfs_free_path(left_path);
5592         btrfs_free_path(right_path);
5593         kvfree(tmp_buf);
5594         return ret;
5595 }
5596
5597 /*
5598  * this is similar to btrfs_next_leaf, but does not try to preserve
5599  * and fixup the path.  It looks for and returns the next key in the
5600  * tree based on the current path and the min_trans parameters.
5601  *
5602  * 0 is returned if another key is found, < 0 if there are any errors
5603  * and 1 is returned if there are no higher keys in the tree
5604  *
5605  * path->keep_locks should be set to 1 on the search made before
5606  * calling this function.
5607  */
5608 int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
5609                         struct btrfs_key *key, int level, u64 min_trans)
5610 {
5611         int slot;
5612         struct extent_buffer *c;
5613
5614         WARN_ON(!path->keep_locks);
5615         while (level < BTRFS_MAX_LEVEL) {
5616                 if (!path->nodes[level])
5617                         return 1;
5618
5619                 slot = path->slots[level] + 1;
5620                 c = path->nodes[level];
5621 next:
5622                 if (slot >= btrfs_header_nritems(c)) {
5623                         int ret;
5624                         int orig_lowest;
5625                         struct btrfs_key cur_key;
5626                         if (level + 1 >= BTRFS_MAX_LEVEL ||
5627                             !path->nodes[level + 1])
5628                                 return 1;
5629
5630                         if (path->locks[level + 1]) {
5631                                 level++;
5632                                 continue;
5633                         }
5634
5635                         slot = btrfs_header_nritems(c) - 1;
5636                         if (level == 0)
5637                                 btrfs_item_key_to_cpu(c, &cur_key, slot);
5638                         else
5639                                 btrfs_node_key_to_cpu(c, &cur_key, slot);
5640
5641                         orig_lowest = path->lowest_level;
5642                         btrfs_release_path(path);
5643                         path->lowest_level = level;
5644                         ret = btrfs_search_slot(NULL, root, &cur_key, path,
5645                                                 0, 0);
5646                         path->lowest_level = orig_lowest;
5647                         if (ret < 0)
5648                                 return ret;
5649
5650                         c = path->nodes[level];
5651                         slot = path->slots[level];
5652                         if (ret == 0)
5653                                 slot++;
5654                         goto next;
5655                 }
5656
5657                 if (level == 0)
5658                         btrfs_item_key_to_cpu(c, key, slot);
5659                 else {
5660                         u64 gen = btrfs_node_ptr_generation(c, slot);
5661
5662                         if (gen < min_trans) {
5663                                 slot++;
5664                                 goto next;
5665                         }
5666                         btrfs_node_key_to_cpu(c, key, slot);
5667                 }
5668                 return 0;
5669         }
5670         return 1;
5671 }
5672
5673 /*
5674  * search the tree again to find a leaf with greater keys
5675  * returns 0 if it found something or 1 if there are no greater leaves.
5676  * returns < 0 on io errors.
5677  */
5678 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
5679 {
5680         return btrfs_next_old_leaf(root, path, 0);
5681 }
5682
5683 int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
5684                         u64 time_seq)
5685 {
5686         int slot;
5687         int level;
5688         struct extent_buffer *c;
5689         struct extent_buffer *next;
5690         struct btrfs_key key;
5691         u32 nritems;
5692         int ret;
5693         int old_spinning = path->leave_spinning;
5694         int next_rw_lock = 0;
5695
5696         nritems = btrfs_header_nritems(path->nodes[0]);
5697         if (nritems == 0)
5698                 return 1;
5699
5700         btrfs_item_key_to_cpu(path->nodes[0], &key, nritems - 1);
5701 again:
5702         level = 1;
5703         next = NULL;
5704         next_rw_lock = 0;
5705         btrfs_release_path(path);
5706
5707         path->keep_locks = 1;
5708         path->leave_spinning = 1;
5709
5710         if (time_seq)
5711                 ret = btrfs_search_old_slot(root, &key, path, time_seq);
5712         else
5713                 ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
5714         path->keep_locks = 0;
5715
5716         if (ret < 0)
5717                 return ret;
5718
5719         nritems = btrfs_header_nritems(path->nodes[0]);
5720         /*
5721          * by releasing the path above we dropped all our locks.  A balance
5722          * could have added more items next to the key that used to be
5723          * at the very end of the block.  So, check again here and
5724          * advance the path if there are now more items available.
5725          */
5726         if (nritems > 0 && path->slots[0] < nritems - 1) {
5727                 if (ret == 0)
5728                         path->slots[0]++;
5729                 ret = 0;
5730                 goto done;
5731         }
5732         /*
5733          * So the above check misses one case:
5734          * - after releasing the path above, someone has removed the item that
5735          *   used to be at the very end of the block, and balance between leafs
5736          *   gets another one with bigger key.offset to replace it.
5737          *
5738          * This one should be returned as well, or we can get leaf corruption
5739          * later(esp. in __btrfs_drop_extents()).
5740          *
5741          * And a bit more explanation about this check,
5742          * with ret > 0, the key isn't found, the path points to the slot
5743          * where it should be inserted, so the path->slots[0] item must be the
5744          * bigger one.
5745          */
5746         if (nritems > 0 && ret > 0 && path->slots[0] == nritems - 1) {
5747                 ret = 0;
5748                 goto done;
5749         }
5750
5751         while (level < BTRFS_MAX_LEVEL) {
5752                 if (!path->nodes[level]) {
5753                         ret = 1;
5754                         goto done;
5755                 }
5756
5757                 slot = path->slots[level] + 1;
5758                 c = path->nodes[level];
5759                 if (slot >= btrfs_header_nritems(c)) {
5760                         level++;
5761                         if (level == BTRFS_MAX_LEVEL) {
5762                                 ret = 1;
5763                                 goto done;
5764                         }
5765                         continue;
5766                 }
5767
5768                 if (next) {
5769                         btrfs_tree_unlock_rw(next, next_rw_lock);
5770                         free_extent_buffer(next);
5771                 }
5772
5773                 next = c;
5774                 next_rw_lock = path->locks[level];
5775                 ret = read_block_for_search(root, path, &next, level,
5776                                             slot, &key);
5777                 if (ret == -EAGAIN)
5778                         goto again;
5779
5780                 if (ret < 0) {
5781                         btrfs_release_path(path);
5782                         goto done;
5783                 }
5784
5785                 if (!path->skip_locking) {
5786                         ret = btrfs_try_tree_read_lock(next);
5787                         if (!ret && time_seq) {
5788                                 /*
5789                                  * If we don't get the lock, we may be racing
5790                                  * with push_leaf_left, holding that lock while
5791                                  * itself waiting for the leaf we've currently
5792                                  * locked. To solve this situation, we give up
5793                                  * on our lock and cycle.
5794                                  */
5795                                 free_extent_buffer(next);
5796                                 btrfs_release_path(path);
5797                                 cond_resched();
5798                                 goto again;
5799                         }
5800                         if (!ret) {
5801                                 btrfs_set_path_blocking(path);
5802                                 btrfs_tree_read_lock(next);
5803                         }
5804                         next_rw_lock = BTRFS_READ_LOCK;
5805                 }
5806                 break;
5807         }
5808         path->slots[level] = slot;
5809         while (1) {
5810                 level--;
5811                 c = path->nodes[level];
5812                 if (path->locks[level])
5813                         btrfs_tree_unlock_rw(c, path->locks[level]);
5814
5815                 free_extent_buffer(c);
5816                 path->nodes[level] = next;
5817                 path->slots[level] = 0;
5818                 if (!path->skip_locking)
5819                         path->locks[level] = next_rw_lock;
5820                 if (!level)
5821                         break;
5822
5823                 ret = read_block_for_search(root, path, &next, level,
5824                                             0, &key);
5825                 if (ret == -EAGAIN)
5826                         goto again;
5827
5828                 if (ret < 0) {
5829                         btrfs_release_path(path);
5830                         goto done;
5831                 }
5832
5833                 if (!path->skip_locking) {
5834                         ret = btrfs_try_tree_read_lock(next);
5835                         if (!ret) {
5836                                 btrfs_set_path_blocking(path);
5837                                 btrfs_tree_read_lock(next);
5838                         }
5839                         next_rw_lock = BTRFS_READ_LOCK;
5840                 }
5841         }
5842         ret = 0;
5843 done:
5844         unlock_up(path, 0, 1, 0, NULL);
5845         path->leave_spinning = old_spinning;
5846         if (!old_spinning)
5847                 btrfs_set_path_blocking(path);
5848
5849         return ret;
5850 }
5851
5852 /*
5853  * this uses btrfs_prev_leaf to walk backwards in the tree, and keeps
5854  * searching until it gets past min_objectid or finds an item of 'type'
5855  *
5856  * returns 0 if something is found, 1 if nothing was found and < 0 on error
5857  */
5858 int btrfs_previous_item(struct btrfs_root *root,
5859                         struct btrfs_path *path, u64 min_objectid,
5860                         int type)
5861 {
5862         struct btrfs_key found_key;
5863         struct extent_buffer *leaf;
5864         u32 nritems;
5865         int ret;
5866
5867         while (1) {
5868                 if (path->slots[0] == 0) {
5869                         btrfs_set_path_blocking(path);
5870                         ret = btrfs_prev_leaf(root, path);
5871                         if (ret != 0)
5872                                 return ret;
5873                 } else {
5874                         path->slots[0]--;
5875                 }
5876                 leaf = path->nodes[0];
5877                 nritems = btrfs_header_nritems(leaf);
5878                 if (nritems == 0)
5879                         return 1;
5880                 if (path->slots[0] == nritems)
5881                         path->slots[0]--;
5882
5883                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
5884                 if (found_key.objectid < min_objectid)
5885                         break;
5886                 if (found_key.type == type)
5887                         return 0;
5888                 if (found_key.objectid == min_objectid &&
5889                     found_key.type < type)
5890                         break;
5891         }
5892         return 1;
5893 }
5894
5895 /*
5896  * search in extent tree to find a previous Metadata/Data extent item with
5897  * min objecitd.
5898  *
5899  * returns 0 if something is found, 1 if nothing was found and < 0 on error
5900  */
5901 int btrfs_previous_extent_item(struct btrfs_root *root,
5902                         struct btrfs_path *path, u64 min_objectid)
5903 {
5904         struct btrfs_key found_key;
5905         struct extent_buffer *leaf;
5906         u32 nritems;
5907         int ret;
5908
5909         while (1) {
5910                 if (path->slots[0] == 0) {
5911                         btrfs_set_path_blocking(path);
5912                         ret = btrfs_prev_leaf(root, path);
5913                         if (ret != 0)
5914                                 return ret;
5915                 } else {
5916                         path->slots[0]--;
5917                 }
5918                 leaf = path->nodes[0];
5919                 nritems = btrfs_header_nritems(leaf);
5920                 if (nritems == 0)
5921                         return 1;
5922                 if (path->slots[0] == nritems)
5923                         path->slots[0]--;
5924
5925                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
5926                 if (found_key.objectid < min_objectid)
5927                         break;
5928                 if (found_key.type == BTRFS_EXTENT_ITEM_KEY ||
5929                     found_key.type == BTRFS_METADATA_ITEM_KEY)
5930                         return 0;
5931                 if (found_key.objectid == min_objectid &&
5932                     found_key.type < BTRFS_EXTENT_ITEM_KEY)
5933                         break;
5934         }
5935         return 1;
5936 }