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