fs/btrfs/super.c

   1 /*
   2  * Copyright (C) 2007 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/blkdev.h>
  20 #include <linux/module.h>
  21 #include <linux/buffer_head.h>
  22 #include <linux/fs.h>
  23 #include <linux/pagemap.h>
  24 #include <linux/highmem.h>
  25 #include <linux/time.h>
  26 #include <linux/init.h>
  27 #include <linux/seq_file.h>
  28 #include <linux/string.h>
  29 #include <linux/backing-dev.h>
  30 #include <linux/mount.h>
  31 #include <linux/mpage.h>
  32 #include <linux/swap.h>
  33 #include <linux/writeback.h>
  34 #include <linux/statfs.h>
  35 #include <linux/compat.h>
  36 #include <linux/parser.h>
  37 #include <linux/ctype.h>
  38 #include <linux/namei.h>
  39 #include <linux/miscdevice.h>
  40 #include <linux/magic.h>
  41 #include <linux/slab.h>
  42 #include "compat.h"
  43 #include "ctree.h"
  44 #include "disk-io.h"
  45 #include "transaction.h"
  46 #include "btrfs_inode.h"
  47 #include "ioctl.h"
  48 #include "print-tree.h"
  49 #include "xattr.h"
  50 #include "volumes.h"
  51 #include "version.h"
  52 #include "export.h"
  53 #include "compression.h"
  54
  55 static const struct super_operations btrfs_super_ops;
  56
  57 static void btrfs_put_super(struct super_block *sb)
  58 {
  59         struct btrfs_root *root = btrfs_sb(sb);
  60         int ret;
  61
  62         ret = close_ctree(root);
  63         sb->s_fs_info = NULL;
  64 }
  65
  66 enum {
  67         Opt_degraded, Opt_subvol, Opt_subvolid, Opt_device, Opt_nodatasum,
  68         Opt_nodatacow, Opt_max_inline, Opt_alloc_start, Opt_nobarrier, Opt_ssd,
  69         Opt_nossd, Opt_ssd_spread, Opt_thread_pool, Opt_noacl, Opt_compress,
  70         Opt_compress_force, Opt_notreelog, Opt_ratio, Opt_flushoncommit,
  71         Opt_discard, Opt_err,
  72 };
  73
  74 static match_table_t tokens = {
  75         {Opt_degraded, "degraded"},
  76         {Opt_subvol, "subvol=%s"},
  77         {Opt_subvolid, "subvolid=%d"},
  78         {Opt_device, "device=%s"},
  79         {Opt_nodatasum, "nodatasum"},
  80         {Opt_nodatacow, "nodatacow"},
  81         {Opt_nobarrier, "nobarrier"},
  82         {Opt_max_inline, "max_inline=%s"},
  83         {Opt_alloc_start, "alloc_start=%s"},
  84         {Opt_thread_pool, "thread_pool=%d"},
  85         {Opt_compress, "compress"},
  86         {Opt_compress_force, "compress-force"},
  87         {Opt_ssd, "ssd"},
  88         {Opt_ssd_spread, "ssd_spread"},
  89         {Opt_nossd, "nossd"},
  90         {Opt_noacl, "noacl"},
  91         {Opt_notreelog, "notreelog"},
  92         {Opt_flushoncommit, "flushoncommit"},
  93         {Opt_ratio, "metadata_ratio=%d"},
  94         {Opt_discard, "discard"},
  95         {Opt_err, NULL},
  96 };
  97
  98 /*
  99  * Regular mount options parser.  Everything that is needed only when
 100  * reading in a new superblock is parsed here.
 101  */
 102 int btrfs_parse_options(struct btrfs_root *root, char *options)
 103 {
 104         struct btrfs_fs_info *info = root->fs_info;
 105         substring_t args[MAX_OPT_ARGS];
 106         char *p, *num, *orig;
 107         int intarg;
 108         int ret = 0;
 109
 110         if (!options)
 111                 return 0;
 112
 113         /*
 114          * strsep changes the string, duplicate it because parse_options
 115          * gets called twice
 116          */
 117         options = kstrdup(options, GFP_NOFS);
 118         if (!options)
 119                 return -ENOMEM;
 120
 121         orig = options;
 122
 123         while ((p = strsep(&options, ",")) != NULL) {
 124                 int token;
 125                 if (!*p)
 126                         continue;
 127
 128                 token = match_token(p, tokens, args);
 129                 switch (token) {
 130                 case Opt_degraded:
 131                         printk(KERN_INFO "btrfs: allowing degraded mounts\n");
 132                         btrfs_set_opt(info->mount_opt, DEGRADED);
 133                         break;
 134                 case Opt_subvol:
 135                 case Opt_subvolid:
 136                 case Opt_device:
 137                         /*
 138                          * These are parsed by btrfs_parse_early_options
 139                          * and can be happily ignored here.
 140                          */
 141                         break;
 142                 case Opt_nodatasum:
 143                         printk(KERN_INFO "btrfs: setting nodatasum\n");
 144                         btrfs_set_opt(info->mount_opt, NODATASUM);
 145                         break;
 146                 case Opt_nodatacow:
 147                         printk(KERN_INFO "btrfs: setting nodatacow\n");
 148                         btrfs_set_opt(info->mount_opt, NODATACOW);
 149                         btrfs_set_opt(info->mount_opt, NODATASUM);
 150                         break;
 151                 case Opt_compress:
 152                         printk(KERN_INFO "btrfs: use compression\n");
 153                         btrfs_set_opt(info->mount_opt, COMPRESS);
 154                         break;
 155                 case Opt_compress_force:
 156                         printk(KERN_INFO "btrfs: forcing compression\n");
 157                         btrfs_set_opt(info->mount_opt, FORCE_COMPRESS);
 158                         btrfs_set_opt(info->mount_opt, COMPRESS);
 159                         break;
 160                 case Opt_ssd:
 161                         printk(KERN_INFO "btrfs: use ssd allocation scheme\n");
 162                         btrfs_set_opt(info->mount_opt, SSD);
 163                         break;
 164                 case Opt_ssd_spread:
 165                         printk(KERN_INFO "btrfs: use spread ssd "
 166                                "allocation scheme\n");
 167                         btrfs_set_opt(info->mount_opt, SSD);
 168                         btrfs_set_opt(info->mount_opt, SSD_SPREAD);
 169                         break;
 170                 case Opt_nossd:
 171                         printk(KERN_INFO "btrfs: not using ssd allocation "
 172                                "scheme\n");
 173                         btrfs_set_opt(info->mount_opt, NOSSD);
 174                         btrfs_clear_opt(info->mount_opt, SSD);
 175                         btrfs_clear_opt(info->mount_opt, SSD_SPREAD);
 176                         break;
 177                 case Opt_nobarrier:
 178                         printk(KERN_INFO "btrfs: turning off barriers\n");
 179                         btrfs_set_opt(info->mount_opt, NOBARRIER);
 180                         break;
 181                 case Opt_thread_pool:
 182                         intarg = 0;
 183                         match_int(&args[0], &intarg);
 184                         if (intarg) {
 185                                 info->thread_pool_size = intarg;
 186                                 printk(KERN_INFO "btrfs: thread pool %d\n",
 187                                        info->thread_pool_size);
 188                         }
 189                         break;
 190                 case Opt_max_inline:
 191                         num = match_strdup(&args[0]);
 192                         if (num) {
 193                                 info->max_inline = memparse(num, NULL);
 194                                 kfree(num);
 195
 196                                 if (info->max_inline) {
 197                                         info->max_inline = max_t(u64,
 198                                                 info->max_inline,
 199                                                 root->sectorsize);
 200                                 }
 201                                 printk(KERN_INFO "btrfs: max_inline at %llu\n",
 202                                         (unsigned long long)info->max_inline);
 203                         }
 204                         break;
 205                 case Opt_alloc_start:
 206                         num = match_strdup(&args[0]);
 207                         if (num) {
 208                                 info->alloc_start = memparse(num, NULL);
 209                                 kfree(num);
 210                                 printk(KERN_INFO
 211                                         "btrfs: allocations start at %llu\n",
 212                                         (unsigned long long)info->alloc_start);
 213                         }
 214                         break;
 215                 case Opt_noacl:
 216                         root->fs_info->sb->s_flags &= ~MS_POSIXACL;
 217                         break;
 218                 case Opt_notreelog:
 219                         printk(KERN_INFO "btrfs: disabling tree log\n");
 220                         btrfs_set_opt(info->mount_opt, NOTREELOG);
 221                         break;
 222                 case Opt_flushoncommit:
 223                         printk(KERN_INFO "btrfs: turning on flush-on-commit\n");
 224                         btrfs_set_opt(info->mount_opt, FLUSHONCOMMIT);
 225                         break;
 226                 case Opt_ratio:
 227                         intarg = 0;
 228                         match_int(&args[0], &intarg);
 229                         if (intarg) {
 230                                 info->metadata_ratio = intarg;
 231                                 printk(KERN_INFO "btrfs: metadata ratio %d\n",
 232                                        info->metadata_ratio);
 233                         }
 234                         break;
 235                 case Opt_discard:
 236                         btrfs_set_opt(info->mount_opt, DISCARD);
 237                         break;
 238                 case Opt_err:
 239                         printk(KERN_INFO "btrfs: unrecognized mount option "
 240                                "'%s'\n", p);
 241                         ret = -EINVAL;
 242                         goto out;
 243                 default:
 244                         break;
 245                 }
 246         }
 247 out:
 248         kfree(orig);
 249         return ret;
 250 }
 251
 252 /*
 253  * Parse mount options that are required early in the mount process.
 254  *
 255  * All other options will be parsed on much later in the mount process and
 256  * only when we need to allocate a new super block.
 257  */
 258 static int btrfs_parse_early_options(const char *options, fmode_t flags,
 259                 void *holder, char **subvol_name, u64 *subvol_objectid,
 260                 struct btrfs_fs_devices **fs_devices)
 261 {
 262         substring_t args[MAX_OPT_ARGS];
 263         char *opts, *p;
 264         int error = 0;
 265         int intarg;
 266
 267         if (!options)
 268                 goto out;
 269
 270         /*
 271          * strsep changes the string, duplicate it because parse_options
 272          * gets called twice
 273          */
 274         opts = kstrdup(options, GFP_KERNEL);
 275         if (!opts)
 276                 return -ENOMEM;
 277
 278         while ((p = strsep(&opts, ",")) != NULL) {
 279                 int token;
 280                 if (!*p)
 281                         continue;
 282
 283                 token = match_token(p, tokens, args);
 284                 switch (token) {
 285                 case Opt_subvol:
 286                         *subvol_name = match_strdup(&args[0]);
 287                         break;
 288                 case Opt_subvolid:
 289                         intarg = 0;
 290                         error = match_int(&args[0], &intarg);
 291                         if (!error) {
 292                                 /* we want the original fs_tree */
 293                                 if (!intarg)
 294                                         *subvol_objectid =
 295                                                 BTRFS_FS_TREE_OBJECTID;
 296                                 else
 297                                         *subvol_objectid = intarg;
 298                         }
 299                         break;
 300                 case Opt_device:
 301                         error = btrfs_scan_one_device(match_strdup(&args[0]),
 302                                         flags, holder, fs_devices);
 303                         if (error)
 304                                 goto out_free_opts;
 305                         break;
 306                 default:
 307                         break;
 308                 }
 309         }
 310
 311  out_free_opts:
 312         kfree(opts);
 313  out:
 314         /*
 315          * If no subvolume name is specified we use the default one.  Allocate
 316          * a copy of the string "." here so that code later in the
 317          * mount path doesn't care if it's the default volume or another one.
 318          */
 319         if (!*subvol_name) {
 320                 *subvol_name = kstrdup(".", GFP_KERNEL);
 321                 if (!*subvol_name)
 322                         return -ENOMEM;
 323         }
 324         return error;
 325 }
 326
 327 static struct dentry *get_default_root(struct super_block *sb,
 328                                        u64 subvol_objectid)
 329 {
 330         struct btrfs_root *root = sb->s_fs_info;
 331         struct btrfs_root *new_root;
 332         struct btrfs_dir_item *di;
 333         struct btrfs_path *path;
 334         struct btrfs_key location;
 335         struct inode *inode;
 336         struct dentry *dentry;
 337         u64 dir_id;
 338         int new = 0;
 339
 340         /*
 341          * We have a specific subvol we want to mount, just setup location and
 342          * go look up the root.
 343          */
 344         if (subvol_objectid) {
 345                 location.objectid = subvol_objectid;
 346                 location.type = BTRFS_ROOT_ITEM_KEY;
 347                 location.offset = (u64)-1;
 348                 goto find_root;
 349         }
 350
 351         path = btrfs_alloc_path();
 352         if (!path)
 353                 return ERR_PTR(-ENOMEM);
 354         path->leave_spinning = 1;
 355
 356         /*
 357          * Find the "default" dir item which points to the root item that we
 358          * will mount by default if we haven't been given a specific subvolume
 359          * to mount.
 360          */
 361         dir_id = btrfs_super_root_dir(&root->fs_info->super_copy);
 362         di = btrfs_lookup_dir_item(NULL, root, path, dir_id, "default", 7, 0);
 363         if (!di) {
 364                 /*
 365                  * Ok the default dir item isn't there.  This is weird since
 366                  * it's always been there, but don't freak out, just try and
 367                  * mount to root most subvolume.
 368                  */
 369                 btrfs_free_path(path);
 370                 dir_id = BTRFS_FIRST_FREE_OBJECTID;
 371                 new_root = root->fs_info->fs_root;
 372                 goto setup_root;
 373         }
 374
 375         btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
 376         btrfs_free_path(path);
 377
 378 find_root:
 379         new_root = btrfs_read_fs_root_no_name(root->fs_info, &location);
 380         if (IS_ERR(new_root))
 381                 return ERR_PTR(PTR_ERR(new_root));
 382
 383         if (btrfs_root_refs(&new_root->root_item) == 0)
 384                 return ERR_PTR(-ENOENT);
 385
 386         dir_id = btrfs_root_dirid(&new_root->root_item);
 387 setup_root:
 388         location.objectid = dir_id;
 389         location.type = BTRFS_INODE_ITEM_KEY;
 390         location.offset = 0;
 391
 392         inode = btrfs_iget(sb, &location, new_root, &new);
 393         if (!inode)
 394                 return ERR_PTR(-ENOMEM);
 395
 396         /*
 397          * If we're just mounting the root most subvol put the inode and return
 398          * a reference to the dentry.  We will have already gotten a reference
 399          * to the inode in btrfs_fill_super so we're good to go.
 400          */
 401         if (!new && sb->s_root->d_inode == inode) {
 402                 iput(inode);
 403                 return dget(sb->s_root);
 404         }
 405
 406         if (new) {
 407                 const struct qstr name = { .name = "/", .len = 1 };
 408
 409                 /*
 410                  * New inode, we need to make the dentry a sibling of s_root so
 411                  * everything gets cleaned up properly on unmount.
 412                  */
 413                 dentry = d_alloc(sb->s_root, &name);
 414                 if (!dentry) {
 415                         iput(inode);
 416                         return ERR_PTR(-ENOMEM);
 417                 }
 418                 d_splice_alias(inode, dentry);
 419         } else {
 420                 /*
 421                  * We found the inode in cache, just find a dentry for it and
 422                  * put the reference to the inode we just got.
 423                  */
 424                 dentry = d_find_alias(inode);
 425                 iput(inode);
 426         }
 427
 428         return dentry;
 429 }
 430
 431 static int btrfs_fill_super(struct super_block *sb,
 432                             struct btrfs_fs_devices *fs_devices,
 433                             void *data, int silent)
 434 {
 435         struct inode *inode;
 436         struct dentry *root_dentry;
 437         struct btrfs_super_block *disk_super;
 438         struct btrfs_root *tree_root;
 439         struct btrfs_key key;
 440         int err;
 441
 442         sb->s_maxbytes = MAX_LFS_FILESIZE;
 443         sb->s_magic = BTRFS_SUPER_MAGIC;
 444         sb->s_op = &btrfs_super_ops;
 445         sb->s_export_op = &btrfs_export_ops;
 446         sb->s_xattr = btrfs_xattr_handlers;
 447         sb->s_time_gran = 1;
 448 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 449         sb->s_flags |= MS_POSIXACL;
 450 #endif
 451
 452         tree_root = open_ctree(sb, fs_devices, (char *)data);
 453
 454         if (IS_ERR(tree_root)) {
 455                 printk("btrfs: open_ctree failed\n");
 456                 return PTR_ERR(tree_root);
 457         }
 458         sb->s_fs_info = tree_root;
 459         disk_super = &tree_root->fs_info->super_copy;
 460
 461         key.objectid = BTRFS_FIRST_FREE_OBJECTID;
 462         key.type = BTRFS_INODE_ITEM_KEY;
 463         key.offset = 0;
 464         inode = btrfs_iget(sb, &key, tree_root->fs_info->fs_root, NULL);
 465         if (IS_ERR(inode)) {
 466                 err = PTR_ERR(inode);
 467                 goto fail_close;
 468         }
 469
 470         root_dentry = d_alloc_root(inode);
 471         if (!root_dentry) {
 472                 iput(inode);
 473                 err = -ENOMEM;
 474                 goto fail_close;
 475         }
 476
 477         sb->s_root = root_dentry;
 478
 479         save_mount_options(sb, data);
 480         return 0;
 481
 482 fail_close:
 483         close_ctree(tree_root);
 484         return err;
 485 }
 486
 487 int btrfs_sync_fs(struct super_block *sb, int wait)
 488 {
 489         struct btrfs_trans_handle *trans;
 490         struct btrfs_root *root = btrfs_sb(sb);
 491         int ret;
 492
 493         if (!wait) {
 494                 filemap_flush(root->fs_info->btree_inode->i_mapping);
 495                 return 0;
 496         }
 497
 498         btrfs_start_delalloc_inodes(root, 0);
 499         btrfs_wait_ordered_extents(root, 0, 0);
 500
 501         trans = btrfs_start_transaction(root, 1);
 502         ret = btrfs_commit_transaction(trans, root);
 503         return ret;
 504 }
 505
 506 static int btrfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 507 {
 508         struct btrfs_root *root = btrfs_sb(vfs->mnt_sb);
 509         struct btrfs_fs_info *info = root->fs_info;
 510
 511         if (btrfs_test_opt(root, DEGRADED))
 512                 seq_puts(seq, ",degraded");
 513         if (btrfs_test_opt(root, NODATASUM))
 514                 seq_puts(seq, ",nodatasum");
 515         if (btrfs_test_opt(root, NODATACOW))
 516                 seq_puts(seq, ",nodatacow");
 517         if (btrfs_test_opt(root, NOBARRIER))
 518                 seq_puts(seq, ",nobarrier");
 519         if (info->max_inline != 8192 * 1024)
 520                 seq_printf(seq, ",max_inline=%llu",
 521                            (unsigned long long)info->max_inline);
 522         if (info->alloc_start != 0)
 523                 seq_printf(seq, ",alloc_start=%llu",
 524                            (unsigned long long)info->alloc_start);
 525         if (info->thread_pool_size !=  min_t(unsigned long,
 526                                              num_online_cpus() + 2, 8))
 527                 seq_printf(seq, ",thread_pool=%d", info->thread_pool_size);
 528         if (btrfs_test_opt(root, COMPRESS))
 529                 seq_puts(seq, ",compress");
 530         if (btrfs_test_opt(root, NOSSD))
 531                 seq_puts(seq, ",nossd");
 532         if (btrfs_test_opt(root, SSD_SPREAD))
 533                 seq_puts(seq, ",ssd_spread");
 534         else if (btrfs_test_opt(root, SSD))
 535                 seq_puts(seq, ",ssd");
 536         if (btrfs_test_opt(root, NOTREELOG))
 537                 seq_puts(seq, ",notreelog");
 538         if (btrfs_test_opt(root, FLUSHONCOMMIT))
 539                 seq_puts(seq, ",flushoncommit");
 540         if (btrfs_test_opt(root, DISCARD))
 541                 seq_puts(seq, ",discard");
 542         if (!(root->fs_info->sb->s_flags & MS_POSIXACL))
 543                 seq_puts(seq, ",noacl");
 544         return 0;
 545 }
 546
 547 static int btrfs_test_super(struct super_block *s, void *data)
 548 {
 549         struct btrfs_fs_devices *test_fs_devices = data;
 550         struct btrfs_root *root = btrfs_sb(s);
 551
 552         return root->fs_info->fs_devices == test_fs_devices;
 553 }
 554
 555 /*
 556  * Find a superblock for the given device / mount point.
 557  *
 558  * Note:  This is based on get_sb_bdev from fs/super.c with a few additions
 559  *        for multiple device setup.  Make sure to keep it in sync.
 560  */
 561 static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
 562                 const char *dev_name, void *data, struct vfsmount *mnt)
 563 {
 564         struct block_device *bdev = NULL;
 565         struct super_block *s;
 566         struct dentry *root;
 567         struct btrfs_fs_devices *fs_devices = NULL;
 568         fmode_t mode = FMODE_READ;
 569         char *subvol_name = NULL;
 570         u64 subvol_objectid = 0;
 571         int error = 0;
 572         int found = 0;
 573
 574         if (!(flags & MS_RDONLY))
 575                 mode |= FMODE_WRITE;
 576
 577         error = btrfs_parse_early_options(data, mode, fs_type,
 578                                           &subvol_name, &subvol_objectid,
 579                                           &fs_devices);
 580         if (error)
 581                 return error;
 582
 583         error = btrfs_scan_one_device(dev_name, mode, fs_type, &fs_devices);
 584         if (error)
 585                 goto error_free_subvol_name;
 586
 587         error = btrfs_open_devices(fs_devices, mode, fs_type);
 588         if (error)
 589                 goto error_free_subvol_name;
 590
 591         if (!(flags & MS_RDONLY) && fs_devices->rw_devices == 0) {
 592                 error = -EACCES;
 593                 goto error_close_devices;
 594         }
 595
 596         bdev = fs_devices->latest_bdev;
 597         s = sget(fs_type, btrfs_test_super, set_anon_super, fs_devices);
 598         if (IS_ERR(s))
 599                 goto error_s;
 600
 601         if (s->s_root) {
 602                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 603                         deactivate_locked_super(s);
 604                         error = -EBUSY;
 605                         goto error_close_devices;
 606                 }
 607
 608                 found = 1;
 609                 btrfs_close_devices(fs_devices);
 610         } else {
 611                 char b[BDEVNAME_SIZE];
 612
 613                 s->s_flags = flags;
 614                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 615                 error = btrfs_fill_super(s, fs_devices, data,
 616                                          flags & MS_SILENT ? 1 : 0);
 617                 if (error) {
 618                         deactivate_locked_super(s);
 619                         goto error_free_subvol_name;
 620                 }
 621
 622                 btrfs_sb(s)->fs_info->bdev_holder = fs_type;
 623                 s->s_flags |= MS_ACTIVE;
 624         }
 625
 626         root = get_default_root(s, subvol_objectid);
 627         if (IS_ERR(root)) {
 628                 error = PTR_ERR(root);
 629                 deactivate_locked_super(s);
 630                 goto error;
 631         }
 632         /* if they gave us a subvolume name bind mount into that */
 633         if (strcmp(subvol_name, ".")) {
 634                 struct dentry *new_root;
 635                 mutex_lock(&root->d_inode->i_mutex);
 636                 new_root = lookup_one_len(subvol_name, root,
 637                                       strlen(subvol_name));
 638                 mutex_unlock(&root->d_inode->i_mutex);
 639
 640                 if (IS_ERR(new_root)) {
 641                         deactivate_locked_super(s);
 642                         error = PTR_ERR(new_root);
 643                         dput(root);
 644                         goto error_close_devices;
 645                 }
 646                 if (!new_root->d_inode) {
 647                         dput(root);
 648                         dput(new_root);
 649                         deactivate_locked_super(s);
 650                         error = -ENXIO;
 651                         goto error_close_devices;
 652                 }
 653                 dput(root);
 654                 root = new_root;
 655         }
 656
 657         mnt->mnt_sb = s;
 658         mnt->mnt_root = root;
 659
 660         kfree(subvol_name);
 661         return 0;
 662
 663 error_s:
 664         error = PTR_ERR(s);
 665 error_close_devices:
 666         btrfs_close_devices(fs_devices);
 667 error_free_subvol_name:
 668         kfree(subvol_name);
 669 error:
 670         return error;
 671 }
 672
 673 static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 674 {
 675         struct btrfs_root *root = btrfs_sb(sb);
 676         int ret;
 677
 678         ret = btrfs_parse_options(root, data);
 679         if (ret)
 680                 return -EINVAL;
 681
 682         if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
 683                 return 0;
 684
 685         if (*flags & MS_RDONLY) {
 686                 sb->s_flags |= MS_RDONLY;
 687
 688                 ret =  btrfs_commit_super(root);
 689                 WARN_ON(ret);
 690         } else {
 691                 if (root->fs_info->fs_devices->rw_devices == 0)
 692                         return -EACCES;
 693
 694                 if (btrfs_super_log_root(&root->fs_info->super_copy) != 0)
 695                         return -EINVAL;
 696
 697                 /* recover relocation */
 698                 ret = btrfs_recover_relocation(root);
 699                 WARN_ON(ret);
 700
 701                 ret = btrfs_cleanup_fs_roots(root->fs_info);
 702                 WARN_ON(ret);
 703
 704                 sb->s_flags &= ~MS_RDONLY;
 705         }
 706
 707         return 0;
 708 }
 709
 710 static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 711 {
 712         struct btrfs_root *root = btrfs_sb(dentry->d_sb);
 713         struct btrfs_super_block *disk_super = &root->fs_info->super_copy;
 714         struct list_head *head = &root->fs_info->space_info;
 715         struct btrfs_space_info *found;
 716         u64 total_used = 0;
 717         int bits = dentry->d_sb->s_blocksize_bits;
 718         __be32 *fsid = (__be32 *)root->fs_info->fsid;
 719
 720         rcu_read_lock();
 721         list_for_each_entry_rcu(found, head, list)
 722                 total_used += found->disk_used;
 723         rcu_read_unlock();
 724
 725         buf->f_namelen = BTRFS_NAME_LEN;
 726         buf->f_blocks = btrfs_super_total_bytes(disk_super) >> bits;
 727         buf->f_bfree = buf->f_blocks - (total_used >> bits);
 728         buf->f_bavail = buf->f_bfree;
 729         buf->f_bsize = dentry->d_sb->s_blocksize;
 730         buf->f_type = BTRFS_SUPER_MAGIC;
 731
 732         /* We treat it as constant endianness (it doesn't matter _which_)
 733            because we want the fsid to come out the same whether mounted
 734            on a big-endian or little-endian host */
 735         buf->f_fsid.val[0] = be32_to_cpu(fsid[0]) ^ be32_to_cpu(fsid[2]);
 736         buf->f_fsid.val[1] = be32_to_cpu(fsid[1]) ^ be32_to_cpu(fsid[3]);
 737         /* Mask in the root object ID too, to disambiguate subvols */
 738         buf->f_fsid.val[0] ^= BTRFS_I(dentry->d_inode)->root->objectid >> 32;
 739         buf->f_fsid.val[1] ^= BTRFS_I(dentry->d_inode)->root->objectid;
 740
 741         return 0;
 742 }
 743
 744 static struct file_system_type btrfs_fs_type = {
 745         .owner          = THIS_MODULE,
 746         .name           = "btrfs",
 747         .get_sb         = btrfs_get_sb,
 748         .kill_sb        = kill_anon_super,
 749         .fs_flags       = FS_REQUIRES_DEV,
 750 };
 751
 752 /*
 753  * used by btrfsctl to scan devices when no FS is mounted
 754  */
 755 static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 756                                 unsigned long arg)
 757 {
 758         struct btrfs_ioctl_vol_args *vol;
 759         struct btrfs_fs_devices *fs_devices;
 760         int ret = -ENOTTY;
 761
 762         if (!capable(CAP_SYS_ADMIN))
 763                 return -EPERM;
 764
 765         vol = memdup_user((void __user *)arg, sizeof(*vol));
 766         if (IS_ERR(vol))
 767                 return PTR_ERR(vol);
 768
 769         switch (cmd) {
 770         case BTRFS_IOC_SCAN_DEV:
 771                 ret = btrfs_scan_one_device(vol->name, FMODE_READ,
 772                                             &btrfs_fs_type, &fs_devices);
 773                 break;
 774         }
 775
 776         kfree(vol);
 777         return ret;
 778 }
 779
 780 static int btrfs_freeze(struct super_block *sb)
 781 {
 782         struct btrfs_root *root = btrfs_sb(sb);
 783         mutex_lock(&root->fs_info->transaction_kthread_mutex);
 784         mutex_lock(&root->fs_info->cleaner_mutex);
 785         return 0;
 786 }
 787
 788 static int btrfs_unfreeze(struct super_block *sb)
 789 {
 790         struct btrfs_root *root = btrfs_sb(sb);
 791         mutex_unlock(&root->fs_info->cleaner_mutex);
 792         mutex_unlock(&root->fs_info->transaction_kthread_mutex);
 793         return 0;
 794 }
 795
 796 static const struct super_operations btrfs_super_ops = {
 797         .drop_inode     = btrfs_drop_inode,
 798         .delete_inode   = btrfs_delete_inode,
 799         .put_super      = btrfs_put_super,
 800         .sync_fs        = btrfs_sync_fs,
 801         .show_options   = btrfs_show_options,
 802         .write_inode    = btrfs_write_inode,
 803         .dirty_inode    = btrfs_dirty_inode,
 804         .alloc_inode    = btrfs_alloc_inode,
 805         .destroy_inode  = btrfs_destroy_inode,
 806         .statfs         = btrfs_statfs,
 807         .remount_fs     = btrfs_remount,
 808         .freeze_fs      = btrfs_freeze,
 809         .unfreeze_fs    = btrfs_unfreeze,
 810 };
 811
 812 static const struct file_operations btrfs_ctl_fops = {
 813         .unlocked_ioctl  = btrfs_control_ioctl,
 814         .compat_ioctl = btrfs_control_ioctl,
 815         .owner   = THIS_MODULE,
 816 };
 817
 818 static struct miscdevice btrfs_misc = {
 819         .minor          = MISC_DYNAMIC_MINOR,
 820         .name           = "btrfs-control",
 821         .fops           = &btrfs_ctl_fops
 822 };
 823
 824 static int btrfs_interface_init(void)
 825 {
 826         return misc_register(&btrfs_misc);
 827 }
 828
 829 static void btrfs_interface_exit(void)
 830 {
 831         if (misc_deregister(&btrfs_misc) < 0)
 832                 printk(KERN_INFO "misc_deregister failed for control device");
 833 }
 834
 835 static int __init init_btrfs_fs(void)
 836 {
 837         int err;
 838
 839         err = btrfs_init_sysfs();
 840         if (err)
 841                 return err;
 842
 843         err = btrfs_init_cachep();
 844         if (err)
 845                 goto free_sysfs;
 846
 847         err = extent_io_init();
 848         if (err)
 849                 goto free_cachep;
 850
 851         err = extent_map_init();
 852         if (err)
 853                 goto free_extent_io;
 854
 855         err = btrfs_interface_init();
 856         if (err)
 857                 goto free_extent_map;
 858
 859         err = register_filesystem(&btrfs_fs_type);
 860         if (err)
 861                 goto unregister_ioctl;
 862
 863         printk(KERN_INFO "%s loaded\n", BTRFS_BUILD_VERSION);
 864         return 0;
 865
 866 unregister_ioctl:
 867         btrfs_interface_exit();
 868 free_extent_map:
 869         extent_map_exit();
 870 free_extent_io:
 871         extent_io_exit();
 872 free_cachep:
 873         btrfs_destroy_cachep();
 874 free_sysfs:
 875         btrfs_exit_sysfs();
 876         return err;
 877 }
 878
 879 static void __exit exit_btrfs_fs(void)
 880 {
 881         btrfs_destroy_cachep();
 882         extent_map_exit();
 883         extent_io_exit();
 884         btrfs_interface_exit();
 885         unregister_filesystem(&btrfs_fs_type);
 886         btrfs_exit_sysfs();
 887         btrfs_cleanup_fs_uuids();
 888         btrfs_zlib_exit();
 889 }
 890
 891 module_init(init_btrfs_fs)
 892 module_exit(exit_btrfs_fs)
 893
 894 MODULE_LICENSE("GPL");