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_space_cache, 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_space_cache, "space_cache"},
  96         {Opt_err, NULL},
  97 };
  98
  99 /*
 100  * Regular mount options parser.  Everything that is needed only when
 101  * reading in a new superblock is parsed here.
 102  */
 103 int btrfs_parse_options(struct btrfs_root *root, char *options)
 104 {
 105         struct btrfs_fs_info *info = root->fs_info;
 106         substring_t args[MAX_OPT_ARGS];
 107         char *p, *num, *orig;
 108         int intarg;
 109         int ret = 0;
 110
 111         if (!options)
 112                 return 0;
 113
 114         /*
 115          * strsep changes the string, duplicate it because parse_options
 116          * gets called twice
 117          */
 118         options = kstrdup(options, GFP_NOFS);
 119         if (!options)
 120                 return -ENOMEM;
 121
 122         orig = options;
 123
 124         while ((p = strsep(&options, ",")) != NULL) {
 125                 int token;
 126                 if (!*p)
 127                         continue;
 128
 129                 token = match_token(p, tokens, args);
 130                 switch (token) {
 131                 case Opt_degraded:
 132                         printk(KERN_INFO "btrfs: allowing degraded mounts\n");
 133                         btrfs_set_opt(info->mount_opt, DEGRADED);
 134                         break;
 135                 case Opt_subvol:
 136                 case Opt_subvolid:
 137                 case Opt_device:
 138                         /*
 139                          * These are parsed by btrfs_parse_early_options
 140                          * and can be happily ignored here.
 141                          */
 142                         break;
 143                 case Opt_nodatasum:
 144                         printk(KERN_INFO "btrfs: setting nodatasum\n");
 145                         btrfs_set_opt(info->mount_opt, NODATASUM);
 146                         break;
 147                 case Opt_nodatacow:
 148                         printk(KERN_INFO "btrfs: setting nodatacow\n");
 149                         btrfs_set_opt(info->mount_opt, NODATACOW);
 150                         btrfs_set_opt(info->mount_opt, NODATASUM);
 151                         break;
 152                 case Opt_compress:
 153                         printk(KERN_INFO "btrfs: use compression\n");
 154                         btrfs_set_opt(info->mount_opt, COMPRESS);
 155                         break;
 156                 case Opt_compress_force:
 157                         printk(KERN_INFO "btrfs: forcing compression\n");
 158                         btrfs_set_opt(info->mount_opt, FORCE_COMPRESS);
 159                         btrfs_set_opt(info->mount_opt, COMPRESS);
 160                         break;
 161                 case Opt_ssd:
 162                         printk(KERN_INFO "btrfs: use ssd allocation scheme\n");
 163                         btrfs_set_opt(info->mount_opt, SSD);
 164                         break;
 165                 case Opt_ssd_spread:
 166                         printk(KERN_INFO "btrfs: use spread ssd "
 167                                "allocation scheme\n");
 168                         btrfs_set_opt(info->mount_opt, SSD);
 169                         btrfs_set_opt(info->mount_opt, SSD_SPREAD);
 170                         break;
 171                 case Opt_nossd:
 172                         printk(KERN_INFO "btrfs: not using ssd allocation "
 173                                "scheme\n");
 174                         btrfs_set_opt(info->mount_opt, NOSSD);
 175                         btrfs_clear_opt(info->mount_opt, SSD);
 176                         btrfs_clear_opt(info->mount_opt, SSD_SPREAD);
 177                         break;
 178                 case Opt_nobarrier:
 179                         printk(KERN_INFO "btrfs: turning off barriers\n");
 180                         btrfs_set_opt(info->mount_opt, NOBARRIER);
 181                         break;
 182                 case Opt_thread_pool:
 183                         intarg = 0;
 184                         match_int(&args[0], &intarg);
 185                         if (intarg) {
 186                                 info->thread_pool_size = intarg;
 187                                 printk(KERN_INFO "btrfs: thread pool %d\n",
 188                                        info->thread_pool_size);
 189                         }
 190                         break;
 191                 case Opt_max_inline:
 192                         num = match_strdup(&args[0]);
 193                         if (num) {
 194                                 info->max_inline = memparse(num, NULL);
 195                                 kfree(num);
 196
 197                                 if (info->max_inline) {
 198                                         info->max_inline = max_t(u64,
 199                                                 info->max_inline,
 200                                                 root->sectorsize);
 201                                 }
 202                                 printk(KERN_INFO "btrfs: max_inline at %llu\n",
 203                                         (unsigned long long)info->max_inline);
 204                         }
 205                         break;
 206                 case Opt_alloc_start:
 207                         num = match_strdup(&args[0]);
 208                         if (num) {
 209                                 info->alloc_start = memparse(num, NULL);
 210                                 kfree(num);
 211                                 printk(KERN_INFO
 212                                         "btrfs: allocations start at %llu\n",
 213                                         (unsigned long long)info->alloc_start);
 214                         }
 215                         break;
 216                 case Opt_noacl:
 217                         root->fs_info->sb->s_flags &= ~MS_POSIXACL;
 218                         break;
 219                 case Opt_notreelog:
 220                         printk(KERN_INFO "btrfs: disabling tree log\n");
 221                         btrfs_set_opt(info->mount_opt, NOTREELOG);
 222                         break;
 223                 case Opt_flushoncommit:
 224                         printk(KERN_INFO "btrfs: turning on flush-on-commit\n");
 225                         btrfs_set_opt(info->mount_opt, FLUSHONCOMMIT);
 226                         break;
 227                 case Opt_ratio:
 228                         intarg = 0;
 229                         match_int(&args[0], &intarg);
 230                         if (intarg) {
 231                                 info->metadata_ratio = intarg;
 232                                 printk(KERN_INFO "btrfs: metadata ratio %d\n",
 233                                        info->metadata_ratio);
 234                         }
 235                         break;
 236                 case Opt_discard:
 237                         btrfs_set_opt(info->mount_opt, DISCARD);
 238                         break;
 239                 case Opt_space_cache:
 240                         printk(KERN_INFO "btrfs: enabling disk space caching\n");
 241                         btrfs_set_opt(info->mount_opt, SPACE_CACHE);
 242                         break;
 243                 case Opt_err:
 244                         printk(KERN_INFO "btrfs: unrecognized mount option "
 245                                "'%s'\n", p);
 246                         ret = -EINVAL;
 247                         goto out;
 248                 default:
 249                         break;
 250                 }
 251         }
 252 out:
 253         kfree(orig);
 254         return ret;
 255 }
 256
 257 /*
 258  * Parse mount options that are required early in the mount process.
 259  *
 260  * All other options will be parsed on much later in the mount process and
 261  * only when we need to allocate a new super block.
 262  */
 263 static int btrfs_parse_early_options(const char *options, fmode_t flags,
 264                 void *holder, char **subvol_name, u64 *subvol_objectid,
 265                 struct btrfs_fs_devices **fs_devices)
 266 {
 267         substring_t args[MAX_OPT_ARGS];
 268         char *opts, *p;
 269         int error = 0;
 270         int intarg;
 271
 272         if (!options)
 273                 goto out;
 274
 275         /*
 276          * strsep changes the string, duplicate it because parse_options
 277          * gets called twice
 278          */
 279         opts = kstrdup(options, GFP_KERNEL);
 280         if (!opts)
 281                 return -ENOMEM;
 282
 283         while ((p = strsep(&opts, ",")) != NULL) {
 284                 int token;
 285                 if (!*p)
 286                         continue;
 287
 288                 token = match_token(p, tokens, args);
 289                 switch (token) {
 290                 case Opt_subvol:
 291                         *subvol_name = match_strdup(&args[0]);
 292                         break;
 293                 case Opt_subvolid:
 294                         intarg = 0;
 295                         error = match_int(&args[0], &intarg);
 296                         if (!error) {
 297                                 /* we want the original fs_tree */
 298                                 if (!intarg)
 299                                         *subvol_objectid =
 300                                                 BTRFS_FS_TREE_OBJECTID;
 301                                 else
 302                                         *subvol_objectid = intarg;
 303                         }
 304                         break;
 305                 case Opt_device:
 306                         error = btrfs_scan_one_device(match_strdup(&args[0]),
 307                                         flags, holder, fs_devices);
 308                         if (error)
 309                                 goto out_free_opts;
 310                         break;
 311                 default:
 312                         break;
 313                 }
 314         }
 315
 316  out_free_opts:
 317         kfree(opts);
 318  out:
 319         /*
 320          * If no subvolume name is specified we use the default one.  Allocate
 321          * a copy of the string "." here so that code later in the
 322          * mount path doesn't care if it's the default volume or another one.
 323          */
 324         if (!*subvol_name) {
 325                 *subvol_name = kstrdup(".", GFP_KERNEL);
 326                 if (!*subvol_name)
 327                         return -ENOMEM;
 328         }
 329         return error;
 330 }
 331
 332 static struct dentry *get_default_root(struct super_block *sb,
 333                                        u64 subvol_objectid)
 334 {
 335         struct btrfs_root *root = sb->s_fs_info;
 336         struct btrfs_root *new_root;
 337         struct btrfs_dir_item *di;
 338         struct btrfs_path *path;
 339         struct btrfs_key location;
 340         struct inode *inode;
 341         struct dentry *dentry;
 342         u64 dir_id;
 343         int new = 0;
 344
 345         /*
 346          * We have a specific subvol we want to mount, just setup location and
 347          * go look up the root.
 348          */
 349         if (subvol_objectid) {
 350                 location.objectid = subvol_objectid;
 351                 location.type = BTRFS_ROOT_ITEM_KEY;
 352                 location.offset = (u64)-1;
 353                 goto find_root;
 354         }
 355
 356         path = btrfs_alloc_path();
 357         if (!path)
 358                 return ERR_PTR(-ENOMEM);
 359         path->leave_spinning = 1;
 360
 361         /*
 362          * Find the "default" dir item which points to the root item that we
 363          * will mount by default if we haven't been given a specific subvolume
 364          * to mount.
 365          */
 366         dir_id = btrfs_super_root_dir(&root->fs_info->super_copy);
 367         di = btrfs_lookup_dir_item(NULL, root, path, dir_id, "default", 7, 0);
 368         if (IS_ERR(di))
 369                 return ERR_CAST(di);
 370         if (!di) {
 371                 /*
 372                  * Ok the default dir item isn't there.  This is weird since
 373                  * it's always been there, but don't freak out, just try and
 374                  * mount to root most subvolume.
 375                  */
 376                 btrfs_free_path(path);
 377                 dir_id = BTRFS_FIRST_FREE_OBJECTID;
 378                 new_root = root->fs_info->fs_root;
 379                 goto setup_root;
 380         }
 381
 382         btrfs_dir_item_key_to_cpu(path->nodes[0], di, &location);
 383         btrfs_free_path(path);
 384
 385 find_root:
 386         new_root = btrfs_read_fs_root_no_name(root->fs_info, &location);
 387         if (IS_ERR(new_root))
 388                 return ERR_PTR(PTR_ERR(new_root));
 389
 390         if (btrfs_root_refs(&new_root->root_item) == 0)
 391                 return ERR_PTR(-ENOENT);
 392
 393         dir_id = btrfs_root_dirid(&new_root->root_item);
 394 setup_root:
 395         location.objectid = dir_id;
 396         location.type = BTRFS_INODE_ITEM_KEY;
 397         location.offset = 0;
 398
 399         inode = btrfs_iget(sb, &location, new_root, &new);
 400         if (IS_ERR(inode))
 401                 return ERR_CAST(inode);
 402
 403         /*
 404          * If we're just mounting the root most subvol put the inode and return
 405          * a reference to the dentry.  We will have already gotten a reference
 406          * to the inode in btrfs_fill_super so we're good to go.
 407          */
 408         if (!new && sb->s_root->d_inode == inode) {
 409                 iput(inode);
 410                 return dget(sb->s_root);
 411         }
 412
 413         if (new) {
 414                 const struct qstr name = { .name = "/", .len = 1 };
 415
 416                 /*
 417                  * New inode, we need to make the dentry a sibling of s_root so
 418                  * everything gets cleaned up properly on unmount.
 419                  */
 420                 dentry = d_alloc(sb->s_root, &name);
 421                 if (!dentry) {
 422                         iput(inode);
 423                         return ERR_PTR(-ENOMEM);
 424                 }
 425                 d_splice_alias(inode, dentry);
 426         } else {
 427                 /*
 428                  * We found the inode in cache, just find a dentry for it and
 429                  * put the reference to the inode we just got.
 430                  */
 431                 dentry = d_find_alias(inode);
 432                 iput(inode);
 433         }
 434
 435         return dentry;
 436 }
 437
 438 static int btrfs_fill_super(struct super_block *sb,
 439                             struct btrfs_fs_devices *fs_devices,
 440                             void *data, int silent)
 441 {
 442         struct inode *inode;
 443         struct dentry *root_dentry;
 444         struct btrfs_super_block *disk_super;
 445         struct btrfs_root *tree_root;
 446         struct btrfs_key key;
 447         int err;
 448
 449         sb->s_maxbytes = MAX_LFS_FILESIZE;
 450         sb->s_magic = BTRFS_SUPER_MAGIC;
 451         sb->s_op = &btrfs_super_ops;
 452         sb->s_export_op = &btrfs_export_ops;
 453         sb->s_xattr = btrfs_xattr_handlers;
 454         sb->s_time_gran = 1;
 455 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 456         sb->s_flags |= MS_POSIXACL;
 457 #endif
 458
 459         tree_root = open_ctree(sb, fs_devices, (char *)data);
 460
 461         if (IS_ERR(tree_root)) {
 462                 printk("btrfs: open_ctree failed\n");
 463                 return PTR_ERR(tree_root);
 464         }
 465         sb->s_fs_info = tree_root;
 466         disk_super = &tree_root->fs_info->super_copy;
 467
 468         key.objectid = BTRFS_FIRST_FREE_OBJECTID;
 469         key.type = BTRFS_INODE_ITEM_KEY;
 470         key.offset = 0;
 471         inode = btrfs_iget(sb, &key, tree_root->fs_info->fs_root, NULL);
 472         if (IS_ERR(inode)) {
 473                 err = PTR_ERR(inode);
 474                 goto fail_close;
 475         }
 476
 477         root_dentry = d_alloc_root(inode);
 478         if (!root_dentry) {
 479                 iput(inode);
 480                 err = -ENOMEM;
 481                 goto fail_close;
 482         }
 483
 484         sb->s_root = root_dentry;
 485
 486         save_mount_options(sb, data);
 487         return 0;
 488
 489 fail_close:
 490         close_ctree(tree_root);
 491         return err;
 492 }
 493
 494 int btrfs_sync_fs(struct super_block *sb, int wait)
 495 {
 496         struct btrfs_trans_handle *trans;
 497         struct btrfs_root *root = btrfs_sb(sb);
 498         int ret;
 499
 500         if (!wait) {
 501                 filemap_flush(root->fs_info->btree_inode->i_mapping);
 502                 return 0;
 503         }
 504
 505         btrfs_start_delalloc_inodes(root, 0);
 506         btrfs_wait_ordered_extents(root, 0, 0);
 507
 508         trans = btrfs_start_transaction(root, 0);
 509         ret = btrfs_commit_transaction(trans, root);
 510         return ret;
 511 }
 512
 513 static int btrfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 514 {
 515         struct btrfs_root *root = btrfs_sb(vfs->mnt_sb);
 516         struct btrfs_fs_info *info = root->fs_info;
 517
 518         if (btrfs_test_opt(root, DEGRADED))
 519                 seq_puts(seq, ",degraded");
 520         if (btrfs_test_opt(root, NODATASUM))
 521                 seq_puts(seq, ",nodatasum");
 522         if (btrfs_test_opt(root, NODATACOW))
 523                 seq_puts(seq, ",nodatacow");
 524         if (btrfs_test_opt(root, NOBARRIER))
 525                 seq_puts(seq, ",nobarrier");
 526         if (info->max_inline != 8192 * 1024)
 527                 seq_printf(seq, ",max_inline=%llu",
 528                            (unsigned long long)info->max_inline);
 529         if (info->alloc_start != 0)
 530                 seq_printf(seq, ",alloc_start=%llu",
 531                            (unsigned long long)info->alloc_start);
 532         if (info->thread_pool_size !=  min_t(unsigned long,
 533                                              num_online_cpus() + 2, 8))
 534                 seq_printf(seq, ",thread_pool=%d", info->thread_pool_size);
 535         if (btrfs_test_opt(root, COMPRESS))
 536                 seq_puts(seq, ",compress");
 537         if (btrfs_test_opt(root, NOSSD))
 538                 seq_puts(seq, ",nossd");
 539         if (btrfs_test_opt(root, SSD_SPREAD))
 540                 seq_puts(seq, ",ssd_spread");
 541         else if (btrfs_test_opt(root, SSD))
 542                 seq_puts(seq, ",ssd");
 543         if (btrfs_test_opt(root, NOTREELOG))
 544                 seq_puts(seq, ",notreelog");
 545         if (btrfs_test_opt(root, FLUSHONCOMMIT))
 546                 seq_puts(seq, ",flushoncommit");
 547         if (btrfs_test_opt(root, DISCARD))
 548                 seq_puts(seq, ",discard");
 549         if (!(root->fs_info->sb->s_flags & MS_POSIXACL))
 550                 seq_puts(seq, ",noacl");
 551         return 0;
 552 }
 553
 554 static int btrfs_test_super(struct super_block *s, void *data)
 555 {
 556         struct btrfs_fs_devices *test_fs_devices = data;
 557         struct btrfs_root *root = btrfs_sb(s);
 558
 559         return root->fs_info->fs_devices == test_fs_devices;
 560 }
 561
 562 /*
 563  * Find a superblock for the given device / mount point.
 564  *
 565  * Note:  This is based on get_sb_bdev from fs/super.c with a few additions
 566  *        for multiple device setup.  Make sure to keep it in sync.
 567  */
 568 static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
 569                 const char *dev_name, void *data, struct vfsmount *mnt)
 570 {
 571         struct block_device *bdev = NULL;
 572         struct super_block *s;
 573         struct dentry *root;
 574         struct btrfs_fs_devices *fs_devices = NULL;
 575         fmode_t mode = FMODE_READ;
 576         char *subvol_name = NULL;
 577         u64 subvol_objectid = 0;
 578         int error = 0;
 579         int found = 0;
 580
 581         if (!(flags & MS_RDONLY))
 582                 mode |= FMODE_WRITE;
 583
 584         error = btrfs_parse_early_options(data, mode, fs_type,
 585                                           &subvol_name, &subvol_objectid,
 586                                           &fs_devices);
 587         if (error)
 588                 return error;
 589
 590         error = btrfs_scan_one_device(dev_name, mode, fs_type, &fs_devices);
 591         if (error)
 592                 goto error_free_subvol_name;
 593
 594         error = btrfs_open_devices(fs_devices, mode, fs_type);
 595         if (error)
 596                 goto error_free_subvol_name;
 597
 598         if (!(flags & MS_RDONLY) && fs_devices->rw_devices == 0) {
 599                 error = -EACCES;
 600                 goto error_close_devices;
 601         }
 602
 603         bdev = fs_devices->latest_bdev;
 604         s = sget(fs_type, btrfs_test_super, set_anon_super, fs_devices);
 605         if (IS_ERR(s))
 606                 goto error_s;
 607
 608         if (s->s_root) {
 609                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 610                         deactivate_locked_super(s);
 611                         error = -EBUSY;
 612                         goto error_close_devices;
 613                 }
 614
 615                 found = 1;
 616                 btrfs_close_devices(fs_devices);
 617         } else {
 618                 char b[BDEVNAME_SIZE];
 619
 620                 s->s_flags = flags;
 621                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 622                 error = btrfs_fill_super(s, fs_devices, data,
 623                                          flags & MS_SILENT ? 1 : 0);
 624                 if (error) {
 625                         deactivate_locked_super(s);
 626                         goto error_free_subvol_name;
 627                 }
 628
 629                 btrfs_sb(s)->fs_info->bdev_holder = fs_type;
 630                 s->s_flags |= MS_ACTIVE;
 631         }
 632
 633         root = get_default_root(s, subvol_objectid);
 634         if (IS_ERR(root)) {
 635                 error = PTR_ERR(root);
 636                 deactivate_locked_super(s);
 637                 goto error;
 638         }
 639         /* if they gave us a subvolume name bind mount into that */
 640         if (strcmp(subvol_name, ".")) {
 641                 struct dentry *new_root;
 642                 mutex_lock(&root->d_inode->i_mutex);
 643                 new_root = lookup_one_len(subvol_name, root,
 644                                       strlen(subvol_name));
 645                 mutex_unlock(&root->d_inode->i_mutex);
 646
 647                 if (IS_ERR(new_root)) {
 648                         deactivate_locked_super(s);
 649                         error = PTR_ERR(new_root);
 650                         dput(root);
 651                         goto error_close_devices;
 652                 }
 653                 if (!new_root->d_inode) {
 654                         dput(root);
 655                         dput(new_root);
 656                         deactivate_locked_super(s);
 657                         error = -ENXIO;
 658                         goto error_close_devices;
 659                 }
 660                 dput(root);
 661                 root = new_root;
 662         }
 663
 664         mnt->mnt_sb = s;
 665         mnt->mnt_root = root;
 666
 667         kfree(subvol_name);
 668         return 0;
 669
 670 error_s:
 671         error = PTR_ERR(s);
 672 error_close_devices:
 673         btrfs_close_devices(fs_devices);
 674 error_free_subvol_name:
 675         kfree(subvol_name);
 676 error:
 677         return error;
 678 }
 679
 680 static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 681 {
 682         struct btrfs_root *root = btrfs_sb(sb);
 683         int ret;
 684
 685         ret = btrfs_parse_options(root, data);
 686         if (ret)
 687                 return -EINVAL;
 688
 689         if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
 690                 return 0;
 691
 692         if (*flags & MS_RDONLY) {
 693                 sb->s_flags |= MS_RDONLY;
 694
 695                 ret =  btrfs_commit_super(root);
 696                 WARN_ON(ret);
 697         } else {
 698                 if (root->fs_info->fs_devices->rw_devices == 0)
 699                         return -EACCES;
 700
 701                 if (btrfs_super_log_root(&root->fs_info->super_copy) != 0)
 702                         return -EINVAL;
 703
 704                 ret = btrfs_cleanup_fs_roots(root->fs_info);
 705                 WARN_ON(ret);
 706
 707                 /* recover relocation */
 708                 ret = btrfs_recover_relocation(root);
 709                 WARN_ON(ret);
 710
 711                 sb->s_flags &= ~MS_RDONLY;
 712         }
 713
 714         return 0;
 715 }
 716
 717 static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 718 {
 719         struct btrfs_root *root = btrfs_sb(dentry->d_sb);
 720         struct btrfs_super_block *disk_super = &root->fs_info->super_copy;
 721         struct list_head *head = &root->fs_info->space_info;
 722         struct btrfs_space_info *found;
 723         u64 total_used = 0;
 724         int bits = dentry->d_sb->s_blocksize_bits;
 725         __be32 *fsid = (__be32 *)root->fs_info->fsid;
 726
 727         rcu_read_lock();
 728         list_for_each_entry_rcu(found, head, list)
 729                 total_used += found->disk_used;
 730         rcu_read_unlock();
 731
 732         buf->f_namelen = BTRFS_NAME_LEN;
 733         buf->f_blocks = btrfs_super_total_bytes(disk_super) >> bits;
 734         buf->f_bfree = buf->f_blocks - (total_used >> bits);
 735         buf->f_bavail = buf->f_bfree;
 736         buf->f_bsize = dentry->d_sb->s_blocksize;
 737         buf->f_type = BTRFS_SUPER_MAGIC;
 738
 739         /* We treat it as constant endianness (it doesn't matter _which_)
 740            because we want the fsid to come out the same whether mounted
 741            on a big-endian or little-endian host */
 742         buf->f_fsid.val[0] = be32_to_cpu(fsid[0]) ^ be32_to_cpu(fsid[2]);
 743         buf->f_fsid.val[1] = be32_to_cpu(fsid[1]) ^ be32_to_cpu(fsid[3]);
 744         /* Mask in the root object ID too, to disambiguate subvols */
 745         buf->f_fsid.val[0] ^= BTRFS_I(dentry->d_inode)->root->objectid >> 32;
 746         buf->f_fsid.val[1] ^= BTRFS_I(dentry->d_inode)->root->objectid;
 747
 748         return 0;
 749 }
 750
 751 static struct file_system_type btrfs_fs_type = {
 752         .owner          = THIS_MODULE,
 753         .name           = "btrfs",
 754         .get_sb         = btrfs_get_sb,
 755         .kill_sb        = kill_anon_super,
 756         .fs_flags       = FS_REQUIRES_DEV,
 757 };
 758
 759 /*
 760  * used by btrfsctl to scan devices when no FS is mounted
 761  */
 762 static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 763                                 unsigned long arg)
 764 {
 765         struct btrfs_ioctl_vol_args *vol;
 766         struct btrfs_fs_devices *fs_devices;
 767         int ret = -ENOTTY;
 768
 769         if (!capable(CAP_SYS_ADMIN))
 770                 return -EPERM;
 771
 772         vol = memdup_user((void __user *)arg, sizeof(*vol));
 773         if (IS_ERR(vol))
 774                 return PTR_ERR(vol);
 775
 776         switch (cmd) {
 777         case BTRFS_IOC_SCAN_DEV:
 778                 ret = btrfs_scan_one_device(vol->name, FMODE_READ,
 779                                             &btrfs_fs_type, &fs_devices);
 780                 break;
 781         }
 782
 783         kfree(vol);
 784         return ret;
 785 }
 786
 787 static int btrfs_freeze(struct super_block *sb)
 788 {
 789         struct btrfs_root *root = btrfs_sb(sb);
 790         mutex_lock(&root->fs_info->transaction_kthread_mutex);
 791         mutex_lock(&root->fs_info->cleaner_mutex);
 792         return 0;
 793 }
 794
 795 static int btrfs_unfreeze(struct super_block *sb)
 796 {
 797         struct btrfs_root *root = btrfs_sb(sb);
 798         mutex_unlock(&root->fs_info->cleaner_mutex);
 799         mutex_unlock(&root->fs_info->transaction_kthread_mutex);
 800         return 0;
 801 }
 802
 803 static const struct super_operations btrfs_super_ops = {
 804         .drop_inode     = btrfs_drop_inode,
 805         .evict_inode    = btrfs_evict_inode,
 806         .put_super      = btrfs_put_super,
 807         .sync_fs        = btrfs_sync_fs,
 808         .show_options   = btrfs_show_options,
 809         .write_inode    = btrfs_write_inode,
 810         .dirty_inode    = btrfs_dirty_inode,
 811         .alloc_inode    = btrfs_alloc_inode,
 812         .destroy_inode  = btrfs_destroy_inode,
 813         .statfs         = btrfs_statfs,
 814         .remount_fs     = btrfs_remount,
 815         .freeze_fs      = btrfs_freeze,
 816         .unfreeze_fs    = btrfs_unfreeze,
 817 };
 818
 819 static const struct file_operations btrfs_ctl_fops = {
 820         .unlocked_ioctl  = btrfs_control_ioctl,
 821         .compat_ioctl = btrfs_control_ioctl,
 822         .owner   = THIS_MODULE,
 823 };
 824
 825 static struct miscdevice btrfs_misc = {
 826         .minor          = BTRFS_MINOR,
 827         .name           = "btrfs-control",
 828         .fops           = &btrfs_ctl_fops
 829 };
 830
 831 MODULE_ALIAS_MISCDEV(BTRFS_MINOR);
 832 MODULE_ALIAS("devname:btrfs-control");
 833
 834 static int btrfs_interface_init(void)
 835 {
 836         return misc_register(&btrfs_misc);
 837 }
 838
 839 static void btrfs_interface_exit(void)
 840 {
 841         if (misc_deregister(&btrfs_misc) < 0)
 842                 printk(KERN_INFO "misc_deregister failed for control device");
 843 }
 844
 845 static int __init init_btrfs_fs(void)
 846 {
 847         int err;
 848
 849         err = btrfs_init_sysfs();
 850         if (err)
 851                 return err;
 852
 853         err = btrfs_init_cachep();
 854         if (err)
 855                 goto free_sysfs;
 856
 857         err = extent_io_init();
 858         if (err)
 859                 goto free_cachep;
 860
 861         err = extent_map_init();
 862         if (err)
 863                 goto free_extent_io;
 864
 865         err = btrfs_interface_init();
 866         if (err)
 867                 goto free_extent_map;
 868
 869         err = register_filesystem(&btrfs_fs_type);
 870         if (err)
 871                 goto unregister_ioctl;
 872
 873         printk(KERN_INFO "%s loaded\n", BTRFS_BUILD_VERSION);
 874         return 0;
 875
 876 unregister_ioctl:
 877         btrfs_interface_exit();
 878 free_extent_map:
 879         extent_map_exit();
 880 free_extent_io:
 881         extent_io_exit();
 882 free_cachep:
 883         btrfs_destroy_cachep();
 884 free_sysfs:
 885         btrfs_exit_sysfs();
 886         return err;
 887 }
 888
 889 static void __exit exit_btrfs_fs(void)
 890 {
 891         btrfs_destroy_cachep();
 892         extent_map_exit();
 893         extent_io_exit();
 894         btrfs_interface_exit();
 895         unregister_filesystem(&btrfs_fs_type);
 896         btrfs_exit_sysfs();
 897         btrfs_cleanup_fs_uuids();
 898         btrfs_zlib_exit();
 899 }
 900
 901 module_init(init_btrfs_fs)
 902 module_exit(exit_btrfs_fs)
 903
 904 MODULE_LICENSE("GPL");