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/smp_lock.h>
  30 #include <linux/backing-dev.h>
  31 #include <linux/mount.h>
  32 #include <linux/mpage.h>
  33 #include <linux/swap.h>
  34 #include <linux/writeback.h>
  35 #include <linux/statfs.h>
  36 #include <linux/compat.h>
  37 #include <linux/parser.h>
  38 #include <linux/ctype.h>
  39 #include <linux/namei.h>
  40 #include <linux/miscdevice.h>
  41 #include <linux/magic.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 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_device, Opt_nodatasum, Opt_nodatacow,
  68         Opt_max_extent, Opt_max_inline, Opt_alloc_start, Opt_nobarrier,
  69         Opt_ssd, Opt_nossd, Opt_ssd_spread, Opt_thread_pool, Opt_noacl,
  70         Opt_compress, Opt_notreelog, Opt_ratio, Opt_flushoncommit, Opt_err,
  71 };
  72
  73 static match_table_t tokens = {
  74         {Opt_degraded, "degraded"},
  75         {Opt_subvol, "subvol=%s"},
  76         {Opt_device, "device=%s"},
  77         {Opt_nodatasum, "nodatasum"},
  78         {Opt_nodatacow, "nodatacow"},
  79         {Opt_nobarrier, "nobarrier"},
  80         {Opt_max_extent, "max_extent=%s"},
  81         {Opt_max_inline, "max_inline=%s"},
  82         {Opt_alloc_start, "alloc_start=%s"},
  83         {Opt_thread_pool, "thread_pool=%d"},
  84         {Opt_compress, "compress"},
  85         {Opt_ssd, "ssd"},
  86         {Opt_ssd_spread, "ssd_spread"},
  87         {Opt_nossd, "nossd"},
  88         {Opt_noacl, "noacl"},
  89         {Opt_notreelog, "notreelog"},
  90         {Opt_flushoncommit, "flushoncommit"},
  91         {Opt_ratio, "metadata_ratio=%d"},
  92         {Opt_err, NULL},
  93 };
  94
  95 u64 btrfs_parse_size(char *str)
  96 {
  97         u64 res;
  98         int mult = 1;
  99         char *end;
 100         char last;
 101
 102         res = simple_strtoul(str, &end, 10);
 103
 104         last = end[0];
 105         if (isalpha(last)) {
 106                 last = tolower(last);
 107                 switch (last) {
 108                 case 'g':
 109                         mult *= 1024;
 110                 case 'm':
 111                         mult *= 1024;
 112                 case 'k':
 113                         mult *= 1024;
 114                 }
 115                 res = res * mult;
 116         }
 117         return res;
 118 }
 119
 120 /*
 121  * Regular mount options parser.  Everything that is needed only when
 122  * reading in a new superblock is parsed here.
 123  */
 124 int btrfs_parse_options(struct btrfs_root *root, char *options)
 125 {
 126         struct btrfs_fs_info *info = root->fs_info;
 127         substring_t args[MAX_OPT_ARGS];
 128         char *p, *num;
 129         int intarg;
 130
 131         if (!options)
 132                 return 0;
 133
 134         /*
 135          * strsep changes the string, duplicate it because parse_options
 136          * gets called twice
 137          */
 138         options = kstrdup(options, GFP_NOFS);
 139         if (!options)
 140                 return -ENOMEM;
 141
 142
 143         while ((p = strsep(&options, ",")) != NULL) {
 144                 int token;
 145                 if (!*p)
 146                         continue;
 147
 148                 token = match_token(p, tokens, args);
 149                 switch (token) {
 150                 case Opt_degraded:
 151                         printk(KERN_INFO "btrfs: allowing degraded mounts\n");
 152                         btrfs_set_opt(info->mount_opt, DEGRADED);
 153                         break;
 154                 case Opt_subvol:
 155                 case Opt_device:
 156                         /*
 157                          * These are parsed by btrfs_parse_early_options
 158                          * and can be happily ignored here.
 159                          */
 160                         break;
 161                 case Opt_nodatasum:
 162                         printk(KERN_INFO "btrfs: setting nodatacsum\n");
 163                         btrfs_set_opt(info->mount_opt, NODATASUM);
 164                         break;
 165                 case Opt_nodatacow:
 166                         printk(KERN_INFO "btrfs: setting nodatacow\n");
 167                         btrfs_set_opt(info->mount_opt, NODATACOW);
 168                         btrfs_set_opt(info->mount_opt, NODATASUM);
 169                         break;
 170                 case Opt_compress:
 171                         printk(KERN_INFO "btrfs: use compression\n");
 172                         btrfs_set_opt(info->mount_opt, COMPRESS);
 173                         break;
 174                 case Opt_ssd:
 175                         printk(KERN_INFO "btrfs: use ssd allocation scheme\n");
 176                         btrfs_set_opt(info->mount_opt, SSD);
 177                         break;
 178                 case Opt_ssd_spread:
 179                         printk(KERN_INFO "btrfs: use spread ssd "
 180                                "allocation scheme\n");
 181                         btrfs_set_opt(info->mount_opt, SSD);
 182                         btrfs_set_opt(info->mount_opt, SSD_SPREAD);
 183                         break;
 184                 case Opt_nossd:
 185                         printk(KERN_INFO "btrfs: not using ssd allocation "
 186                                "scheme\n");
 187                         btrfs_clear_opt(info->mount_opt, SSD);
 188                         btrfs_clear_opt(info->mount_opt, SSD_SPREAD);
 189                         break;
 190                 case Opt_nobarrier:
 191                         printk(KERN_INFO "btrfs: turning off barriers\n");
 192                         btrfs_set_opt(info->mount_opt, NOBARRIER);
 193                         break;
 194                 case Opt_thread_pool:
 195                         intarg = 0;
 196                         match_int(&args[0], &intarg);
 197                         if (intarg) {
 198                                 info->thread_pool_size = intarg;
 199                                 printk(KERN_INFO "btrfs: thread pool %d\n",
 200                                        info->thread_pool_size);
 201                         }
 202                         break;
 203                 case Opt_max_extent:
 204                         num = match_strdup(&args[0]);
 205                         if (num) {
 206                                 info->max_extent = btrfs_parse_size(num);
 207                                 kfree(num);
 208
 209                                 info->max_extent = max_t(u64,
 210                                         info->max_extent, root->sectorsize);
 211                                 printk(KERN_INFO "btrfs: max_extent at %llu\n",
 212                                        (unsigned long long)info->max_extent);
 213                         }
 214                         break;
 215                 case Opt_max_inline:
 216                         num = match_strdup(&args[0]);
 217                         if (num) {
 218                                 info->max_inline = btrfs_parse_size(num);
 219                                 kfree(num);
 220
 221                                 if (info->max_inline) {
 222                                         info->max_inline = max_t(u64,
 223                                                 info->max_inline,
 224                                                 root->sectorsize);
 225                                 }
 226                                 printk(KERN_INFO "btrfs: max_inline at %llu\n",
 227                                         (unsigned long long)info->max_inline);
 228                         }
 229                         break;
 230                 case Opt_alloc_start:
 231                         num = match_strdup(&args[0]);
 232                         if (num) {
 233                                 info->alloc_start = btrfs_parse_size(num);
 234                                 kfree(num);
 235                                 printk(KERN_INFO
 236                                         "btrfs: allocations start at %llu\n",
 237                                         (unsigned long long)info->alloc_start);
 238                         }
 239                         break;
 240                 case Opt_noacl:
 241                         root->fs_info->sb->s_flags &= ~MS_POSIXACL;
 242                         break;
 243                 case Opt_notreelog:
 244                         printk(KERN_INFO "btrfs: disabling tree log\n");
 245                         btrfs_set_opt(info->mount_opt, NOTREELOG);
 246                         break;
 247                 case Opt_flushoncommit:
 248                         printk(KERN_INFO "btrfs: turning on flush-on-commit\n");
 249                         btrfs_set_opt(info->mount_opt, FLUSHONCOMMIT);
 250                         break;
 251                 case Opt_ratio:
 252                         intarg = 0;
 253                         match_int(&args[0], &intarg);
 254                         if (intarg) {
 255                                 info->metadata_ratio = intarg;
 256                                 printk(KERN_INFO "btrfs: metadata ratio %d\n",
 257                                        info->metadata_ratio);
 258                         }
 259                         break;
 260                 default:
 261                         break;
 262                 }
 263         }
 264         kfree(options);
 265         return 0;
 266 }
 267
 268 /*
 269  * Parse mount options that are required early in the mount process.
 270  *
 271  * All other options will be parsed on much later in the mount process and
 272  * only when we need to allocate a new super block.
 273  */
 274 static int btrfs_parse_early_options(const char *options, fmode_t flags,
 275                 void *holder, char **subvol_name,
 276                 struct btrfs_fs_devices **fs_devices)
 277 {
 278         substring_t args[MAX_OPT_ARGS];
 279         char *opts, *p;
 280         int error = 0;
 281
 282         if (!options)
 283                 goto out;
 284
 285         /*
 286          * strsep changes the string, duplicate it because parse_options
 287          * gets called twice
 288          */
 289         opts = kstrdup(options, GFP_KERNEL);
 290         if (!opts)
 291                 return -ENOMEM;
 292
 293         while ((p = strsep(&opts, ",")) != NULL) {
 294                 int token;
 295                 if (!*p)
 296                         continue;
 297
 298                 token = match_token(p, tokens, args);
 299                 switch (token) {
 300                 case Opt_subvol:
 301                         *subvol_name = match_strdup(&args[0]);
 302                         break;
 303                 case Opt_device:
 304                         error = btrfs_scan_one_device(match_strdup(&args[0]),
 305                                         flags, holder, fs_devices);
 306                         if (error)
 307                                 goto out_free_opts;
 308                         break;
 309                 default:
 310                         break;
 311                 }
 312         }
 313
 314  out_free_opts:
 315         kfree(opts);
 316  out:
 317         /*
 318          * If no subvolume name is specified we use the default one.  Allocate
 319          * a copy of the string "." here so that code later in the
 320          * mount path doesn't care if it's the default volume or another one.
 321          */
 322         if (!*subvol_name) {
 323                 *subvol_name = kstrdup(".", GFP_KERNEL);
 324                 if (!*subvol_name)
 325                         return -ENOMEM;
 326         }
 327         return error;
 328 }
 329
 330 static int btrfs_fill_super(struct super_block *sb,
 331                             struct btrfs_fs_devices *fs_devices,
 332                             void *data, int silent)
 333 {
 334         struct inode *inode;
 335         struct dentry *root_dentry;
 336         struct btrfs_super_block *disk_super;
 337         struct btrfs_root *tree_root;
 338         struct btrfs_key key;
 339         int err;
 340
 341         sb->s_maxbytes = MAX_LFS_FILESIZE;
 342         sb->s_magic = BTRFS_SUPER_MAGIC;
 343         sb->s_op = &btrfs_super_ops;
 344         sb->s_export_op = &btrfs_export_ops;
 345         sb->s_xattr = btrfs_xattr_handlers;
 346         sb->s_time_gran = 1;
 347         sb->s_flags |= MS_POSIXACL;
 348
 349         tree_root = open_ctree(sb, fs_devices, (char *)data);
 350
 351         if (IS_ERR(tree_root)) {
 352                 printk("btrfs: open_ctree failed\n");
 353                 return PTR_ERR(tree_root);
 354         }
 355         sb->s_fs_info = tree_root;
 356         disk_super = &tree_root->fs_info->super_copy;
 357
 358         key.objectid = BTRFS_FIRST_FREE_OBJECTID;
 359         key.type = BTRFS_INODE_ITEM_KEY;
 360         key.offset = 0;
 361         inode = btrfs_iget(sb, &key, tree_root->fs_info->fs_root);
 362         if (IS_ERR(inode)) {
 363                 err = PTR_ERR(inode);
 364                 goto fail_close;
 365         }
 366
 367         root_dentry = d_alloc_root(inode);
 368         if (!root_dentry) {
 369                 iput(inode);
 370                 err = -ENOMEM;
 371                 goto fail_close;
 372         }
 373 #if 0
 374         /* this does the super kobj at the same time */
 375         err = btrfs_sysfs_add_super(tree_root->fs_info);
 376         if (err)
 377                 goto fail_close;
 378 #endif
 379
 380         sb->s_root = root_dentry;
 381
 382         save_mount_options(sb, data);
 383         return 0;
 384
 385 fail_close:
 386         close_ctree(tree_root);
 387         return err;
 388 }
 389
 390 int btrfs_sync_fs(struct super_block *sb, int wait)
 391 {
 392         struct btrfs_trans_handle *trans;
 393         struct btrfs_root *root = btrfs_sb(sb);
 394         int ret;
 395
 396         if (sb->s_flags & MS_RDONLY)
 397                 return 0;
 398
 399         sb->s_dirt = 0;
 400         if (!wait) {
 401                 filemap_flush(root->fs_info->btree_inode->i_mapping);
 402                 return 0;
 403         }
 404
 405         btrfs_start_delalloc_inodes(root);
 406         btrfs_wait_ordered_extents(root, 0);
 407
 408         trans = btrfs_start_transaction(root, 1);
 409         ret = btrfs_commit_transaction(trans, root);
 410         sb->s_dirt = 0;
 411         return ret;
 412 }
 413
 414 static int btrfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 415 {
 416         struct btrfs_root *root = btrfs_sb(vfs->mnt_sb);
 417         struct btrfs_fs_info *info = root->fs_info;
 418
 419         if (btrfs_test_opt(root, DEGRADED))
 420                 seq_puts(seq, ",degraded");
 421         if (btrfs_test_opt(root, NODATASUM))
 422                 seq_puts(seq, ",nodatasum");
 423         if (btrfs_test_opt(root, NODATACOW))
 424                 seq_puts(seq, ",nodatacow");
 425         if (btrfs_test_opt(root, NOBARRIER))
 426                 seq_puts(seq, ",nobarrier");
 427         if (info->max_extent != (u64)-1)
 428                 seq_printf(seq, ",max_extent=%llu",
 429                            (unsigned long long)info->max_extent);
 430         if (info->max_inline != 8192 * 1024)
 431                 seq_printf(seq, ",max_inline=%llu",
 432                            (unsigned long long)info->max_inline);
 433         if (info->alloc_start != 0)
 434                 seq_printf(seq, ",alloc_start=%llu",
 435                            (unsigned long long)info->alloc_start);
 436         if (info->thread_pool_size !=  min_t(unsigned long,
 437                                              num_online_cpus() + 2, 8))
 438                 seq_printf(seq, ",thread_pool=%d", info->thread_pool_size);
 439         if (btrfs_test_opt(root, COMPRESS))
 440                 seq_puts(seq, ",compress");
 441         if (btrfs_test_opt(root, SSD_SPREAD))
 442                 seq_puts(seq, ",ssd_spread");
 443         else if (btrfs_test_opt(root, SSD))
 444                 seq_puts(seq, ",ssd");
 445         if (btrfs_test_opt(root, NOTREELOG))
 446                 seq_puts(seq, ",notreelog");
 447         if (btrfs_test_opt(root, FLUSHONCOMMIT))
 448                 seq_puts(seq, ",flushoncommit");
 449         if (!(root->fs_info->sb->s_flags & MS_POSIXACL))
 450                 seq_puts(seq, ",noacl");
 451         return 0;
 452 }
 453
 454 static void btrfs_write_super(struct super_block *sb)
 455 {
 456         sb->s_dirt = 0;
 457 }
 458
 459 static int btrfs_test_super(struct super_block *s, void *data)
 460 {
 461         struct btrfs_fs_devices *test_fs_devices = data;
 462         struct btrfs_root *root = btrfs_sb(s);
 463
 464         return root->fs_info->fs_devices == test_fs_devices;
 465 }
 466
 467 /*
 468  * Find a superblock for the given device / mount point.
 469  *
 470  * Note:  This is based on get_sb_bdev from fs/super.c with a few additions
 471  *        for multiple device setup.  Make sure to keep it in sync.
 472  */
 473 static int btrfs_get_sb(struct file_system_type *fs_type, int flags,
 474                 const char *dev_name, void *data, struct vfsmount *mnt)
 475 {
 476         char *subvol_name = NULL;
 477         struct block_device *bdev = NULL;
 478         struct super_block *s;
 479         struct dentry *root;
 480         struct btrfs_fs_devices *fs_devices = NULL;
 481         fmode_t mode = FMODE_READ;
 482         int error = 0;
 483
 484         if (!(flags & MS_RDONLY))
 485                 mode |= FMODE_WRITE;
 486
 487         error = btrfs_parse_early_options(data, mode, fs_type,
 488                                           &subvol_name, &fs_devices);
 489         if (error)
 490                 return error;
 491
 492         error = btrfs_scan_one_device(dev_name, mode, fs_type, &fs_devices);
 493         if (error)
 494                 goto error_free_subvol_name;
 495
 496         error = btrfs_open_devices(fs_devices, mode, fs_type);
 497         if (error)
 498                 goto error_free_subvol_name;
 499
 500         if (!(flags & MS_RDONLY) && fs_devices->rw_devices == 0) {
 501                 error = -EACCES;
 502                 goto error_close_devices;
 503         }
 504
 505         bdev = fs_devices->latest_bdev;
 506         s = sget(fs_type, btrfs_test_super, set_anon_super, fs_devices);
 507         if (IS_ERR(s))
 508                 goto error_s;
 509
 510         if (s->s_root) {
 511                 if ((flags ^ s->s_flags) & MS_RDONLY) {
 512                         deactivate_locked_super(s);
 513                         error = -EBUSY;
 514                         goto error_close_devices;
 515                 }
 516
 517                 btrfs_close_devices(fs_devices);
 518         } else {
 519                 char b[BDEVNAME_SIZE];
 520
 521                 s->s_flags = flags;
 522                 strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
 523                 error = btrfs_fill_super(s, fs_devices, data,
 524                                          flags & MS_SILENT ? 1 : 0);
 525                 if (error) {
 526                         deactivate_locked_super(s);
 527                         goto error_free_subvol_name;
 528                 }
 529
 530                 btrfs_sb(s)->fs_info->bdev_holder = fs_type;
 531                 s->s_flags |= MS_ACTIVE;
 532         }
 533
 534         if (!strcmp(subvol_name, "."))
 535                 root = dget(s->s_root);
 536         else {
 537                 mutex_lock(&s->s_root->d_inode->i_mutex);
 538                 root = lookup_one_len(subvol_name, s->s_root,
 539                                       strlen(subvol_name));
 540                 mutex_unlock(&s->s_root->d_inode->i_mutex);
 541
 542                 if (IS_ERR(root)) {
 543                         deactivate_locked_super(s);
 544                         error = PTR_ERR(root);
 545                         goto error_free_subvol_name;
 546                 }
 547                 if (!root->d_inode) {
 548                         dput(root);
 549                         deactivate_locked_super(s);
 550                         error = -ENXIO;
 551                         goto error_free_subvol_name;
 552                 }
 553         }
 554
 555         mnt->mnt_sb = s;
 556         mnt->mnt_root = root;
 557
 558         kfree(subvol_name);
 559         return 0;
 560
 561 error_s:
 562         error = PTR_ERR(s);
 563 error_close_devices:
 564         btrfs_close_devices(fs_devices);
 565 error_free_subvol_name:
 566         kfree(subvol_name);
 567         return error;
 568 }
 569
 570 static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 571 {
 572         struct btrfs_root *root = btrfs_sb(sb);
 573         int ret;
 574
 575         ret = btrfs_parse_options(root, data);
 576         if (ret)
 577                 return -EINVAL;
 578
 579         if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
 580                 return 0;
 581
 582         if (*flags & MS_RDONLY) {
 583                 sb->s_flags |= MS_RDONLY;
 584
 585                 ret =  btrfs_commit_super(root);
 586                 WARN_ON(ret);
 587         } else {
 588                 if (root->fs_info->fs_devices->rw_devices == 0)
 589                         return -EACCES;
 590
 591                 if (btrfs_super_log_root(&root->fs_info->super_copy) != 0)
 592                         return -EINVAL;
 593
 594                 /* recover relocation */
 595                 ret = btrfs_recover_relocation(root);
 596                 WARN_ON(ret);
 597
 598                 ret = btrfs_cleanup_fs_roots(root->fs_info);
 599                 WARN_ON(ret);
 600
 601                 sb->s_flags &= ~MS_RDONLY;
 602         }
 603
 604         return 0;
 605 }
 606
 607 static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 608 {
 609         struct btrfs_root *root = btrfs_sb(dentry->d_sb);
 610         struct btrfs_super_block *disk_super = &root->fs_info->super_copy;
 611         int bits = dentry->d_sb->s_blocksize_bits;
 612         __be32 *fsid = (__be32 *)root->fs_info->fsid;
 613
 614         buf->f_namelen = BTRFS_NAME_LEN;
 615         buf->f_blocks = btrfs_super_total_bytes(disk_super) >> bits;
 616         buf->f_bfree = buf->f_blocks -
 617                 (btrfs_super_bytes_used(disk_super) >> bits);
 618         buf->f_bavail = buf->f_bfree;
 619         buf->f_bsize = dentry->d_sb->s_blocksize;
 620         buf->f_type = BTRFS_SUPER_MAGIC;
 621
 622         /* We treat it as constant endianness (it doesn't matter _which_)
 623            because we want the fsid to come out the same whether mounted
 624            on a big-endian or little-endian host */
 625         buf->f_fsid.val[0] = be32_to_cpu(fsid[0]) ^ be32_to_cpu(fsid[2]);
 626         buf->f_fsid.val[1] = be32_to_cpu(fsid[1]) ^ be32_to_cpu(fsid[3]);
 627         /* Mask in the root object ID too, to disambiguate subvols */
 628         buf->f_fsid.val[0] ^= BTRFS_I(dentry->d_inode)->root->objectid >> 32;
 629         buf->f_fsid.val[1] ^= BTRFS_I(dentry->d_inode)->root->objectid;
 630
 631         return 0;
 632 }
 633
 634 static struct file_system_type btrfs_fs_type = {
 635         .owner          = THIS_MODULE,
 636         .name           = "btrfs",
 637         .get_sb         = btrfs_get_sb,
 638         .kill_sb        = kill_anon_super,
 639         .fs_flags       = FS_REQUIRES_DEV,
 640 };
 641
 642 /*
 643  * used by btrfsctl to scan devices when no FS is mounted
 644  */
 645 static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 646                                 unsigned long arg)
 647 {
 648         struct btrfs_ioctl_vol_args *vol;
 649         struct btrfs_fs_devices *fs_devices;
 650         int ret = -ENOTTY;
 651
 652         if (!capable(CAP_SYS_ADMIN))
 653                 return -EPERM;
 654
 655         vol = memdup_user((void __user *)arg, sizeof(*vol));
 656         if (IS_ERR(vol))
 657                 return PTR_ERR(vol);
 658
 659         switch (cmd) {
 660         case BTRFS_IOC_SCAN_DEV:
 661                 ret = btrfs_scan_one_device(vol->name, FMODE_READ,
 662                                             &btrfs_fs_type, &fs_devices);
 663                 break;
 664         }
 665
 666         kfree(vol);
 667         return ret;
 668 }
 669
 670 static int btrfs_freeze(struct super_block *sb)
 671 {
 672         struct btrfs_root *root = btrfs_sb(sb);
 673         mutex_lock(&root->fs_info->transaction_kthread_mutex);
 674         mutex_lock(&root->fs_info->cleaner_mutex);
 675         return 0;
 676 }
 677
 678 static int btrfs_unfreeze(struct super_block *sb)
 679 {
 680         struct btrfs_root *root = btrfs_sb(sb);
 681         mutex_unlock(&root->fs_info->cleaner_mutex);
 682         mutex_unlock(&root->fs_info->transaction_kthread_mutex);
 683         return 0;
 684 }
 685
 686 static struct super_operations btrfs_super_ops = {
 687         .delete_inode   = btrfs_delete_inode,
 688         .put_super      = btrfs_put_super,
 689         .write_super    = btrfs_write_super,
 690         .sync_fs        = btrfs_sync_fs,
 691         .show_options   = btrfs_show_options,
 692         .write_inode    = btrfs_write_inode,
 693         .dirty_inode    = btrfs_dirty_inode,
 694         .alloc_inode    = btrfs_alloc_inode,
 695         .destroy_inode  = btrfs_destroy_inode,
 696         .statfs         = btrfs_statfs,
 697         .remount_fs     = btrfs_remount,
 698         .freeze_fs      = btrfs_freeze,
 699         .unfreeze_fs    = btrfs_unfreeze,
 700 };
 701
 702 static const struct file_operations btrfs_ctl_fops = {
 703         .unlocked_ioctl  = btrfs_control_ioctl,
 704         .compat_ioctl = btrfs_control_ioctl,
 705         .owner   = THIS_MODULE,
 706 };
 707
 708 static struct miscdevice btrfs_misc = {
 709         .minor          = MISC_DYNAMIC_MINOR,
 710         .name           = "btrfs-control",
 711         .fops           = &btrfs_ctl_fops
 712 };
 713
 714 static int btrfs_interface_init(void)
 715 {
 716         return misc_register(&btrfs_misc);
 717 }
 718
 719 static void btrfs_interface_exit(void)
 720 {
 721         if (misc_deregister(&btrfs_misc) < 0)
 722                 printk(KERN_INFO "misc_deregister failed for control device");
 723 }
 724
 725 static int __init init_btrfs_fs(void)
 726 {
 727         int err;
 728
 729         err = btrfs_init_sysfs();
 730         if (err)
 731                 return err;
 732
 733         err = btrfs_init_cachep();
 734         if (err)
 735                 goto free_sysfs;
 736
 737         err = extent_io_init();
 738         if (err)
 739                 goto free_cachep;
 740
 741         err = extent_map_init();
 742         if (err)
 743                 goto free_extent_io;
 744
 745         err = btrfs_interface_init();
 746         if (err)
 747                 goto free_extent_map;
 748
 749         err = register_filesystem(&btrfs_fs_type);
 750         if (err)
 751                 goto unregister_ioctl;
 752
 753         printk(KERN_INFO "%s loaded\n", BTRFS_BUILD_VERSION);
 754         return 0;
 755
 756 unregister_ioctl:
 757         btrfs_interface_exit();
 758 free_extent_map:
 759         extent_map_exit();
 760 free_extent_io:
 761         extent_io_exit();
 762 free_cachep:
 763         btrfs_destroy_cachep();
 764 free_sysfs:
 765         btrfs_exit_sysfs();
 766         return err;
 767 }
 768
 769 static void __exit exit_btrfs_fs(void)
 770 {
 771         btrfs_destroy_cachep();
 772         extent_map_exit();
 773         extent_io_exit();
 774         btrfs_interface_exit();
 775         unregister_filesystem(&btrfs_fs_type);
 776         btrfs_exit_sysfs();
 777         btrfs_cleanup_fs_uuids();
 778         btrfs_zlib_exit();
 779 }
 780
 781 module_init(init_btrfs_fs)
 782 module_exit(exit_btrfs_fs)
 783
 784 MODULE_LICENSE("GPL");