| 1 | /* |
| 2 | * linux/fs/super.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992 Linus Torvalds |
| 5 | * |
| 6 | * super.c contains code to handle: - mount structures |
| 7 | * - super-block tables |
| 8 | * - filesystem drivers list |
| 9 | * - mount system call |
| 10 | * - umount system call |
| 11 | * - ustat system call |
| 12 | * |
| 13 | * GK 2/5/95 - Changed to support mounting the root fs via NFS |
| 14 | * |
| 15 | * Added kerneld support: Jacques Gelinas and Bjorn Ekwall |
| 16 | * Added change_root: Werner Almesberger & Hans Lermen, Feb '96 |
| 17 | * Added options to /proc/mounts: |
| 18 | * Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996. |
| 19 | * Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998 |
| 20 | * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000 |
| 21 | */ |
| 22 | |
| 23 | #include <linux/module.h> |
| 24 | #include <linux/slab.h> |
| 25 | #include <linux/acct.h> |
| 26 | #include <linux/blkdev.h> |
| 27 | #include <linux/mount.h> |
| 28 | #include <linux/security.h> |
| 29 | #include <linux/writeback.h> /* for the emergency remount stuff */ |
| 30 | #include <linux/idr.h> |
| 31 | #include <linux/mutex.h> |
| 32 | #include <linux/backing-dev.h> |
| 33 | #include <linux/rculist_bl.h> |
| 34 | #include <linux/cleancache.h> |
| 35 | #include "internal.h" |
| 36 | |
| 37 | |
| 38 | LIST_HEAD(super_blocks); |
| 39 | DEFINE_SPINLOCK(sb_lock); |
| 40 | |
| 41 | /* |
| 42 | * One thing we have to be careful of with a per-sb shrinker is that we don't |
| 43 | * drop the last active reference to the superblock from within the shrinker. |
| 44 | * If that happens we could trigger unregistering the shrinker from within the |
| 45 | * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we |
| 46 | * take a passive reference to the superblock to avoid this from occurring. |
| 47 | */ |
| 48 | static int prune_super(struct shrinker *shrink, struct shrink_control *sc) |
| 49 | { |
| 50 | struct super_block *sb; |
| 51 | int fs_objects = 0; |
| 52 | int total_objects; |
| 53 | |
| 54 | sb = container_of(shrink, struct super_block, s_shrink); |
| 55 | |
| 56 | /* |
| 57 | * Deadlock avoidance. We may hold various FS locks, and we don't want |
| 58 | * to recurse into the FS that called us in clear_inode() and friends.. |
| 59 | */ |
| 60 | if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS)) |
| 61 | return -1; |
| 62 | |
| 63 | if (!grab_super_passive(sb)) |
| 64 | return !sc->nr_to_scan ? 0 : -1; |
| 65 | |
| 66 | if (sb->s_op && sb->s_op->nr_cached_objects) |
| 67 | fs_objects = sb->s_op->nr_cached_objects(sb); |
| 68 | |
| 69 | total_objects = sb->s_nr_dentry_unused + |
| 70 | sb->s_nr_inodes_unused + fs_objects + 1; |
| 71 | |
| 72 | if (sc->nr_to_scan) { |
| 73 | int dentries; |
| 74 | int inodes; |
| 75 | |
| 76 | /* proportion the scan between the caches */ |
| 77 | dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) / |
| 78 | total_objects; |
| 79 | inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) / |
| 80 | total_objects; |
| 81 | if (fs_objects) |
| 82 | fs_objects = (sc->nr_to_scan * fs_objects) / |
| 83 | total_objects; |
| 84 | /* |
| 85 | * prune the dcache first as the icache is pinned by it, then |
| 86 | * prune the icache, followed by the filesystem specific caches |
| 87 | */ |
| 88 | prune_dcache_sb(sb, dentries); |
| 89 | prune_icache_sb(sb, inodes); |
| 90 | |
| 91 | if (fs_objects && sb->s_op->free_cached_objects) { |
| 92 | sb->s_op->free_cached_objects(sb, fs_objects); |
| 93 | fs_objects = sb->s_op->nr_cached_objects(sb); |
| 94 | } |
| 95 | total_objects = sb->s_nr_dentry_unused + |
| 96 | sb->s_nr_inodes_unused + fs_objects; |
| 97 | } |
| 98 | |
| 99 | total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure; |
| 100 | drop_super(sb); |
| 101 | return total_objects; |
| 102 | } |
| 103 | |
| 104 | /** |
| 105 | * alloc_super - create new superblock |
| 106 | * @type: filesystem type superblock should belong to |
| 107 | * |
| 108 | * Allocates and initializes a new &struct super_block. alloc_super() |
| 109 | * returns a pointer new superblock or %NULL if allocation had failed. |
| 110 | */ |
| 111 | static struct super_block *alloc_super(struct file_system_type *type) |
| 112 | { |
| 113 | struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER); |
| 114 | static const struct super_operations default_op; |
| 115 | |
| 116 | if (s) { |
| 117 | if (security_sb_alloc(s)) { |
| 118 | kfree(s); |
| 119 | s = NULL; |
| 120 | goto out; |
| 121 | } |
| 122 | #ifdef CONFIG_SMP |
| 123 | s->s_files = alloc_percpu(struct list_head); |
| 124 | if (!s->s_files) { |
| 125 | security_sb_free(s); |
| 126 | kfree(s); |
| 127 | s = NULL; |
| 128 | goto out; |
| 129 | } else { |
| 130 | int i; |
| 131 | |
| 132 | for_each_possible_cpu(i) |
| 133 | INIT_LIST_HEAD(per_cpu_ptr(s->s_files, i)); |
| 134 | } |
| 135 | #else |
| 136 | INIT_LIST_HEAD(&s->s_files); |
| 137 | #endif |
| 138 | s->s_bdi = &default_backing_dev_info; |
| 139 | INIT_HLIST_NODE(&s->s_instances); |
| 140 | INIT_HLIST_BL_HEAD(&s->s_anon); |
| 141 | INIT_LIST_HEAD(&s->s_inodes); |
| 142 | INIT_LIST_HEAD(&s->s_dentry_lru); |
| 143 | INIT_LIST_HEAD(&s->s_inode_lru); |
| 144 | spin_lock_init(&s->s_inode_lru_lock); |
| 145 | INIT_LIST_HEAD(&s->s_mounts); |
| 146 | init_rwsem(&s->s_umount); |
| 147 | mutex_init(&s->s_lock); |
| 148 | lockdep_set_class(&s->s_umount, &type->s_umount_key); |
| 149 | /* |
| 150 | * The locking rules for s_lock are up to the |
| 151 | * filesystem. For example ext3fs has different |
| 152 | * lock ordering than usbfs: |
| 153 | */ |
| 154 | lockdep_set_class(&s->s_lock, &type->s_lock_key); |
| 155 | /* |
| 156 | * sget() can have s_umount recursion. |
| 157 | * |
| 158 | * When it cannot find a suitable sb, it allocates a new |
| 159 | * one (this one), and tries again to find a suitable old |
| 160 | * one. |
| 161 | * |
| 162 | * In case that succeeds, it will acquire the s_umount |
| 163 | * lock of the old one. Since these are clearly distrinct |
| 164 | * locks, and this object isn't exposed yet, there's no |
| 165 | * risk of deadlocks. |
| 166 | * |
| 167 | * Annotate this by putting this lock in a different |
| 168 | * subclass. |
| 169 | */ |
| 170 | down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); |
| 171 | s->s_count = 1; |
| 172 | atomic_set(&s->s_active, 1); |
| 173 | mutex_init(&s->s_vfs_rename_mutex); |
| 174 | lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key); |
| 175 | mutex_init(&s->s_dquot.dqio_mutex); |
| 176 | mutex_init(&s->s_dquot.dqonoff_mutex); |
| 177 | init_rwsem(&s->s_dquot.dqptr_sem); |
| 178 | init_waitqueue_head(&s->s_wait_unfrozen); |
| 179 | s->s_maxbytes = MAX_NON_LFS; |
| 180 | s->s_op = &default_op; |
| 181 | s->s_time_gran = 1000000000; |
| 182 | s->cleancache_poolid = -1; |
| 183 | |
| 184 | s->s_shrink.seeks = DEFAULT_SEEKS; |
| 185 | s->s_shrink.shrink = prune_super; |
| 186 | s->s_shrink.batch = 1024; |
| 187 | } |
| 188 | out: |
| 189 | return s; |
| 190 | } |
| 191 | |
| 192 | /** |
| 193 | * destroy_super - frees a superblock |
| 194 | * @s: superblock to free |
| 195 | * |
| 196 | * Frees a superblock. |
| 197 | */ |
| 198 | static inline void destroy_super(struct super_block *s) |
| 199 | { |
| 200 | #ifdef CONFIG_SMP |
| 201 | free_percpu(s->s_files); |
| 202 | #endif |
| 203 | security_sb_free(s); |
| 204 | WARN_ON(!list_empty(&s->s_mounts)); |
| 205 | kfree(s->s_subtype); |
| 206 | kfree(s->s_options); |
| 207 | kfree(s); |
| 208 | } |
| 209 | |
| 210 | /* Superblock refcounting */ |
| 211 | |
| 212 | /* |
| 213 | * Drop a superblock's refcount. The caller must hold sb_lock. |
| 214 | */ |
| 215 | static void __put_super(struct super_block *sb) |
| 216 | { |
| 217 | if (!--sb->s_count) { |
| 218 | list_del_init(&sb->s_list); |
| 219 | destroy_super(sb); |
| 220 | } |
| 221 | } |
| 222 | |
| 223 | /** |
| 224 | * put_super - drop a temporary reference to superblock |
| 225 | * @sb: superblock in question |
| 226 | * |
| 227 | * Drops a temporary reference, frees superblock if there's no |
| 228 | * references left. |
| 229 | */ |
| 230 | static void put_super(struct super_block *sb) |
| 231 | { |
| 232 | spin_lock(&sb_lock); |
| 233 | __put_super(sb); |
| 234 | spin_unlock(&sb_lock); |
| 235 | } |
| 236 | |
| 237 | |
| 238 | /** |
| 239 | * deactivate_locked_super - drop an active reference to superblock |
| 240 | * @s: superblock to deactivate |
| 241 | * |
| 242 | * Drops an active reference to superblock, converting it into a temprory |
| 243 | * one if there is no other active references left. In that case we |
| 244 | * tell fs driver to shut it down and drop the temporary reference we |
| 245 | * had just acquired. |
| 246 | * |
| 247 | * Caller holds exclusive lock on superblock; that lock is released. |
| 248 | */ |
| 249 | void deactivate_locked_super(struct super_block *s) |
| 250 | { |
| 251 | struct file_system_type *fs = s->s_type; |
| 252 | if (atomic_dec_and_test(&s->s_active)) { |
| 253 | cleancache_flush_fs(s); |
| 254 | fs->kill_sb(s); |
| 255 | |
| 256 | /* caches are now gone, we can safely kill the shrinker now */ |
| 257 | unregister_shrinker(&s->s_shrink); |
| 258 | |
| 259 | /* |
| 260 | * We need to call rcu_barrier so all the delayed rcu free |
| 261 | * inodes are flushed before we release the fs module. |
| 262 | */ |
| 263 | rcu_barrier(); |
| 264 | put_filesystem(fs); |
| 265 | put_super(s); |
| 266 | } else { |
| 267 | up_write(&s->s_umount); |
| 268 | } |
| 269 | } |
| 270 | |
| 271 | EXPORT_SYMBOL(deactivate_locked_super); |
| 272 | |
| 273 | /** |
| 274 | * deactivate_super - drop an active reference to superblock |
| 275 | * @s: superblock to deactivate |
| 276 | * |
| 277 | * Variant of deactivate_locked_super(), except that superblock is *not* |
| 278 | * locked by caller. If we are going to drop the final active reference, |
| 279 | * lock will be acquired prior to that. |
| 280 | */ |
| 281 | void deactivate_super(struct super_block *s) |
| 282 | { |
| 283 | if (!atomic_add_unless(&s->s_active, -1, 1)) { |
| 284 | down_write(&s->s_umount); |
| 285 | deactivate_locked_super(s); |
| 286 | } |
| 287 | } |
| 288 | |
| 289 | EXPORT_SYMBOL(deactivate_super); |
| 290 | |
| 291 | /** |
| 292 | * grab_super - acquire an active reference |
| 293 | * @s: reference we are trying to make active |
| 294 | * |
| 295 | * Tries to acquire an active reference. grab_super() is used when we |
| 296 | * had just found a superblock in super_blocks or fs_type->fs_supers |
| 297 | * and want to turn it into a full-blown active reference. grab_super() |
| 298 | * is called with sb_lock held and drops it. Returns 1 in case of |
| 299 | * success, 0 if we had failed (superblock contents was already dead or |
| 300 | * dying when grab_super() had been called). |
| 301 | */ |
| 302 | static int grab_super(struct super_block *s) __releases(sb_lock) |
| 303 | { |
| 304 | if (atomic_inc_not_zero(&s->s_active)) { |
| 305 | spin_unlock(&sb_lock); |
| 306 | return 1; |
| 307 | } |
| 308 | /* it's going away */ |
| 309 | s->s_count++; |
| 310 | spin_unlock(&sb_lock); |
| 311 | /* wait for it to die */ |
| 312 | down_write(&s->s_umount); |
| 313 | up_write(&s->s_umount); |
| 314 | put_super(s); |
| 315 | return 0; |
| 316 | } |
| 317 | |
| 318 | /* |
| 319 | * grab_super_passive - acquire a passive reference |
| 320 | * @s: reference we are trying to grab |
| 321 | * |
| 322 | * Tries to acquire a passive reference. This is used in places where we |
| 323 | * cannot take an active reference but we need to ensure that the |
| 324 | * superblock does not go away while we are working on it. It returns |
| 325 | * false if a reference was not gained, and returns true with the s_umount |
| 326 | * lock held in read mode if a reference is gained. On successful return, |
| 327 | * the caller must drop the s_umount lock and the passive reference when |
| 328 | * done. |
| 329 | */ |
| 330 | bool grab_super_passive(struct super_block *sb) |
| 331 | { |
| 332 | spin_lock(&sb_lock); |
| 333 | if (hlist_unhashed(&sb->s_instances)) { |
| 334 | spin_unlock(&sb_lock); |
| 335 | return false; |
| 336 | } |
| 337 | |
| 338 | sb->s_count++; |
| 339 | spin_unlock(&sb_lock); |
| 340 | |
| 341 | if (down_read_trylock(&sb->s_umount)) { |
| 342 | if (sb->s_root && (sb->s_flags & MS_BORN)) |
| 343 | return true; |
| 344 | up_read(&sb->s_umount); |
| 345 | } |
| 346 | |
| 347 | put_super(sb); |
| 348 | return false; |
| 349 | } |
| 350 | |
| 351 | /* |
| 352 | * Superblock locking. We really ought to get rid of these two. |
| 353 | */ |
| 354 | void lock_super(struct super_block * sb) |
| 355 | { |
| 356 | mutex_lock(&sb->s_lock); |
| 357 | } |
| 358 | |
| 359 | void unlock_super(struct super_block * sb) |
| 360 | { |
| 361 | mutex_unlock(&sb->s_lock); |
| 362 | } |
| 363 | |
| 364 | EXPORT_SYMBOL(lock_super); |
| 365 | EXPORT_SYMBOL(unlock_super); |
| 366 | |
| 367 | /** |
| 368 | * generic_shutdown_super - common helper for ->kill_sb() |
| 369 | * @sb: superblock to kill |
| 370 | * |
| 371 | * generic_shutdown_super() does all fs-independent work on superblock |
| 372 | * shutdown. Typical ->kill_sb() should pick all fs-specific objects |
| 373 | * that need destruction out of superblock, call generic_shutdown_super() |
| 374 | * and release aforementioned objects. Note: dentries and inodes _are_ |
| 375 | * taken care of and do not need specific handling. |
| 376 | * |
| 377 | * Upon calling this function, the filesystem may no longer alter or |
| 378 | * rearrange the set of dentries belonging to this super_block, nor may it |
| 379 | * change the attachments of dentries to inodes. |
| 380 | */ |
| 381 | void generic_shutdown_super(struct super_block *sb) |
| 382 | { |
| 383 | const struct super_operations *sop = sb->s_op; |
| 384 | |
| 385 | if (sb->s_root) { |
| 386 | shrink_dcache_for_umount(sb); |
| 387 | sync_filesystem(sb); |
| 388 | sb->s_flags &= ~MS_ACTIVE; |
| 389 | |
| 390 | fsnotify_unmount_inodes(&sb->s_inodes); |
| 391 | |
| 392 | evict_inodes(sb); |
| 393 | |
| 394 | if (sop->put_super) |
| 395 | sop->put_super(sb); |
| 396 | |
| 397 | if (!list_empty(&sb->s_inodes)) { |
| 398 | printk("VFS: Busy inodes after unmount of %s. " |
| 399 | "Self-destruct in 5 seconds. Have a nice day...\n", |
| 400 | sb->s_id); |
| 401 | } |
| 402 | } |
| 403 | spin_lock(&sb_lock); |
| 404 | /* should be initialized for __put_super_and_need_restart() */ |
| 405 | hlist_del_init(&sb->s_instances); |
| 406 | spin_unlock(&sb_lock); |
| 407 | up_write(&sb->s_umount); |
| 408 | } |
| 409 | |
| 410 | EXPORT_SYMBOL(generic_shutdown_super); |
| 411 | |
| 412 | /** |
| 413 | * sget - find or create a superblock |
| 414 | * @type: filesystem type superblock should belong to |
| 415 | * @test: comparison callback |
| 416 | * @set: setup callback |
| 417 | * @data: argument to each of them |
| 418 | */ |
| 419 | struct super_block *sget(struct file_system_type *type, |
| 420 | int (*test)(struct super_block *,void *), |
| 421 | int (*set)(struct super_block *,void *), |
| 422 | void *data) |
| 423 | { |
| 424 | struct super_block *s = NULL; |
| 425 | struct hlist_node *node; |
| 426 | struct super_block *old; |
| 427 | int err; |
| 428 | |
| 429 | retry: |
| 430 | spin_lock(&sb_lock); |
| 431 | if (test) { |
| 432 | hlist_for_each_entry(old, node, &type->fs_supers, s_instances) { |
| 433 | if (!test(old, data)) |
| 434 | continue; |
| 435 | if (!grab_super(old)) |
| 436 | goto retry; |
| 437 | if (s) { |
| 438 | up_write(&s->s_umount); |
| 439 | destroy_super(s); |
| 440 | s = NULL; |
| 441 | } |
| 442 | down_write(&old->s_umount); |
| 443 | if (unlikely(!(old->s_flags & MS_BORN))) { |
| 444 | deactivate_locked_super(old); |
| 445 | goto retry; |
| 446 | } |
| 447 | return old; |
| 448 | } |
| 449 | } |
| 450 | if (!s) { |
| 451 | spin_unlock(&sb_lock); |
| 452 | s = alloc_super(type); |
| 453 | if (!s) |
| 454 | return ERR_PTR(-ENOMEM); |
| 455 | goto retry; |
| 456 | } |
| 457 | |
| 458 | err = set(s, data); |
| 459 | if (err) { |
| 460 | spin_unlock(&sb_lock); |
| 461 | up_write(&s->s_umount); |
| 462 | destroy_super(s); |
| 463 | return ERR_PTR(err); |
| 464 | } |
| 465 | s->s_type = type; |
| 466 | strlcpy(s->s_id, type->name, sizeof(s->s_id)); |
| 467 | list_add_tail(&s->s_list, &super_blocks); |
| 468 | hlist_add_head(&s->s_instances, &type->fs_supers); |
| 469 | spin_unlock(&sb_lock); |
| 470 | get_filesystem(type); |
| 471 | register_shrinker(&s->s_shrink); |
| 472 | return s; |
| 473 | } |
| 474 | |
| 475 | EXPORT_SYMBOL(sget); |
| 476 | |
| 477 | void drop_super(struct super_block *sb) |
| 478 | { |
| 479 | up_read(&sb->s_umount); |
| 480 | put_super(sb); |
| 481 | } |
| 482 | |
| 483 | EXPORT_SYMBOL(drop_super); |
| 484 | |
| 485 | /** |
| 486 | * sync_supers - helper for periodic superblock writeback |
| 487 | * |
| 488 | * Call the write_super method if present on all dirty superblocks in |
| 489 | * the system. This is for the periodic writeback used by most older |
| 490 | * filesystems. For data integrity superblock writeback use |
| 491 | * sync_filesystems() instead. |
| 492 | * |
| 493 | * Note: check the dirty flag before waiting, so we don't |
| 494 | * hold up the sync while mounting a device. (The newly |
| 495 | * mounted device won't need syncing.) |
| 496 | */ |
| 497 | void sync_supers(void) |
| 498 | { |
| 499 | struct super_block *sb, *p = NULL; |
| 500 | |
| 501 | spin_lock(&sb_lock); |
| 502 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 503 | if (hlist_unhashed(&sb->s_instances)) |
| 504 | continue; |
| 505 | if (sb->s_op->write_super && sb->s_dirt) { |
| 506 | sb->s_count++; |
| 507 | spin_unlock(&sb_lock); |
| 508 | |
| 509 | down_read(&sb->s_umount); |
| 510 | if (sb->s_root && sb->s_dirt && (sb->s_flags & MS_BORN)) |
| 511 | sb->s_op->write_super(sb); |
| 512 | up_read(&sb->s_umount); |
| 513 | |
| 514 | spin_lock(&sb_lock); |
| 515 | if (p) |
| 516 | __put_super(p); |
| 517 | p = sb; |
| 518 | } |
| 519 | } |
| 520 | if (p) |
| 521 | __put_super(p); |
| 522 | spin_unlock(&sb_lock); |
| 523 | } |
| 524 | |
| 525 | /** |
| 526 | * iterate_supers - call function for all active superblocks |
| 527 | * @f: function to call |
| 528 | * @arg: argument to pass to it |
| 529 | * |
| 530 | * Scans the superblock list and calls given function, passing it |
| 531 | * locked superblock and given argument. |
| 532 | */ |
| 533 | void iterate_supers(void (*f)(struct super_block *, void *), void *arg) |
| 534 | { |
| 535 | struct super_block *sb, *p = NULL; |
| 536 | |
| 537 | spin_lock(&sb_lock); |
| 538 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 539 | if (hlist_unhashed(&sb->s_instances)) |
| 540 | continue; |
| 541 | sb->s_count++; |
| 542 | spin_unlock(&sb_lock); |
| 543 | |
| 544 | down_read(&sb->s_umount); |
| 545 | if (sb->s_root && (sb->s_flags & MS_BORN)) |
| 546 | f(sb, arg); |
| 547 | up_read(&sb->s_umount); |
| 548 | |
| 549 | spin_lock(&sb_lock); |
| 550 | if (p) |
| 551 | __put_super(p); |
| 552 | p = sb; |
| 553 | } |
| 554 | if (p) |
| 555 | __put_super(p); |
| 556 | spin_unlock(&sb_lock); |
| 557 | } |
| 558 | |
| 559 | /** |
| 560 | * iterate_supers_type - call function for superblocks of given type |
| 561 | * @type: fs type |
| 562 | * @f: function to call |
| 563 | * @arg: argument to pass to it |
| 564 | * |
| 565 | * Scans the superblock list and calls given function, passing it |
| 566 | * locked superblock and given argument. |
| 567 | */ |
| 568 | void iterate_supers_type(struct file_system_type *type, |
| 569 | void (*f)(struct super_block *, void *), void *arg) |
| 570 | { |
| 571 | struct super_block *sb, *p = NULL; |
| 572 | struct hlist_node *node; |
| 573 | |
| 574 | spin_lock(&sb_lock); |
| 575 | hlist_for_each_entry(sb, node, &type->fs_supers, s_instances) { |
| 576 | sb->s_count++; |
| 577 | spin_unlock(&sb_lock); |
| 578 | |
| 579 | down_read(&sb->s_umount); |
| 580 | if (sb->s_root && (sb->s_flags & MS_BORN)) |
| 581 | f(sb, arg); |
| 582 | up_read(&sb->s_umount); |
| 583 | |
| 584 | spin_lock(&sb_lock); |
| 585 | if (p) |
| 586 | __put_super(p); |
| 587 | p = sb; |
| 588 | } |
| 589 | if (p) |
| 590 | __put_super(p); |
| 591 | spin_unlock(&sb_lock); |
| 592 | } |
| 593 | |
| 594 | EXPORT_SYMBOL(iterate_supers_type); |
| 595 | |
| 596 | /** |
| 597 | * get_super - get the superblock of a device |
| 598 | * @bdev: device to get the superblock for |
| 599 | * |
| 600 | * Scans the superblock list and finds the superblock of the file system |
| 601 | * mounted on the device given. %NULL is returned if no match is found. |
| 602 | */ |
| 603 | |
| 604 | struct super_block *get_super(struct block_device *bdev) |
| 605 | { |
| 606 | struct super_block *sb; |
| 607 | |
| 608 | if (!bdev) |
| 609 | return NULL; |
| 610 | |
| 611 | spin_lock(&sb_lock); |
| 612 | rescan: |
| 613 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 614 | if (hlist_unhashed(&sb->s_instances)) |
| 615 | continue; |
| 616 | if (sb->s_bdev == bdev) { |
| 617 | sb->s_count++; |
| 618 | spin_unlock(&sb_lock); |
| 619 | down_read(&sb->s_umount); |
| 620 | /* still alive? */ |
| 621 | if (sb->s_root && (sb->s_flags & MS_BORN)) |
| 622 | return sb; |
| 623 | up_read(&sb->s_umount); |
| 624 | /* nope, got unmounted */ |
| 625 | spin_lock(&sb_lock); |
| 626 | __put_super(sb); |
| 627 | goto rescan; |
| 628 | } |
| 629 | } |
| 630 | spin_unlock(&sb_lock); |
| 631 | return NULL; |
| 632 | } |
| 633 | |
| 634 | EXPORT_SYMBOL(get_super); |
| 635 | |
| 636 | /** |
| 637 | * get_active_super - get an active reference to the superblock of a device |
| 638 | * @bdev: device to get the superblock for |
| 639 | * |
| 640 | * Scans the superblock list and finds the superblock of the file system |
| 641 | * mounted on the device given. Returns the superblock with an active |
| 642 | * reference or %NULL if none was found. |
| 643 | */ |
| 644 | struct super_block *get_active_super(struct block_device *bdev) |
| 645 | { |
| 646 | struct super_block *sb; |
| 647 | |
| 648 | if (!bdev) |
| 649 | return NULL; |
| 650 | |
| 651 | restart: |
| 652 | spin_lock(&sb_lock); |
| 653 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 654 | if (hlist_unhashed(&sb->s_instances)) |
| 655 | continue; |
| 656 | if (sb->s_bdev == bdev) { |
| 657 | if (grab_super(sb)) /* drops sb_lock */ |
| 658 | return sb; |
| 659 | else |
| 660 | goto restart; |
| 661 | } |
| 662 | } |
| 663 | spin_unlock(&sb_lock); |
| 664 | return NULL; |
| 665 | } |
| 666 | |
| 667 | struct super_block *user_get_super(dev_t dev) |
| 668 | { |
| 669 | struct super_block *sb; |
| 670 | |
| 671 | spin_lock(&sb_lock); |
| 672 | rescan: |
| 673 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 674 | if (hlist_unhashed(&sb->s_instances)) |
| 675 | continue; |
| 676 | if (sb->s_dev == dev) { |
| 677 | sb->s_count++; |
| 678 | spin_unlock(&sb_lock); |
| 679 | down_read(&sb->s_umount); |
| 680 | /* still alive? */ |
| 681 | if (sb->s_root && (sb->s_flags & MS_BORN)) |
| 682 | return sb; |
| 683 | up_read(&sb->s_umount); |
| 684 | /* nope, got unmounted */ |
| 685 | spin_lock(&sb_lock); |
| 686 | __put_super(sb); |
| 687 | goto rescan; |
| 688 | } |
| 689 | } |
| 690 | spin_unlock(&sb_lock); |
| 691 | return NULL; |
| 692 | } |
| 693 | |
| 694 | /** |
| 695 | * do_remount_sb - asks filesystem to change mount options. |
| 696 | * @sb: superblock in question |
| 697 | * @flags: numeric part of options |
| 698 | * @data: the rest of options |
| 699 | * @force: whether or not to force the change |
| 700 | * |
| 701 | * Alters the mount options of a mounted file system. |
| 702 | */ |
| 703 | int do_remount_sb(struct super_block *sb, int flags, void *data, int force) |
| 704 | { |
| 705 | int retval; |
| 706 | int remount_ro; |
| 707 | |
| 708 | if (sb->s_frozen != SB_UNFROZEN) |
| 709 | return -EBUSY; |
| 710 | |
| 711 | #ifdef CONFIG_BLOCK |
| 712 | if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev)) |
| 713 | return -EACCES; |
| 714 | #endif |
| 715 | |
| 716 | if (flags & MS_RDONLY) |
| 717 | acct_auto_close(sb); |
| 718 | shrink_dcache_sb(sb); |
| 719 | sync_filesystem(sb); |
| 720 | |
| 721 | remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY); |
| 722 | |
| 723 | /* If we are remounting RDONLY and current sb is read/write, |
| 724 | make sure there are no rw files opened */ |
| 725 | if (remount_ro) { |
| 726 | if (force) { |
| 727 | mark_files_ro(sb); |
| 728 | } else { |
| 729 | retval = sb_prepare_remount_readonly(sb); |
| 730 | if (retval) |
| 731 | return retval; |
| 732 | } |
| 733 | } |
| 734 | |
| 735 | if (sb->s_op->remount_fs) { |
| 736 | retval = sb->s_op->remount_fs(sb, &flags, data); |
| 737 | if (retval) { |
| 738 | if (!force) |
| 739 | goto cancel_readonly; |
| 740 | /* If forced remount, go ahead despite any errors */ |
| 741 | WARN(1, "forced remount of a %s fs returned %i\n", |
| 742 | sb->s_type->name, retval); |
| 743 | } |
| 744 | } |
| 745 | sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK); |
| 746 | /* Needs to be ordered wrt mnt_is_readonly() */ |
| 747 | smp_wmb(); |
| 748 | sb->s_readonly_remount = 0; |
| 749 | |
| 750 | /* |
| 751 | * Some filesystems modify their metadata via some other path than the |
| 752 | * bdev buffer cache (eg. use a private mapping, or directories in |
| 753 | * pagecache, etc). Also file data modifications go via their own |
| 754 | * mappings. So If we try to mount readonly then copy the filesystem |
| 755 | * from bdev, we could get stale data, so invalidate it to give a best |
| 756 | * effort at coherency. |
| 757 | */ |
| 758 | if (remount_ro && sb->s_bdev) |
| 759 | invalidate_bdev(sb->s_bdev); |
| 760 | return 0; |
| 761 | |
| 762 | cancel_readonly: |
| 763 | sb->s_readonly_remount = 0; |
| 764 | return retval; |
| 765 | } |
| 766 | |
| 767 | static void do_emergency_remount(struct work_struct *work) |
| 768 | { |
| 769 | struct super_block *sb, *p = NULL; |
| 770 | |
| 771 | spin_lock(&sb_lock); |
| 772 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 773 | if (hlist_unhashed(&sb->s_instances)) |
| 774 | continue; |
| 775 | sb->s_count++; |
| 776 | spin_unlock(&sb_lock); |
| 777 | down_write(&sb->s_umount); |
| 778 | if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) && |
| 779 | !(sb->s_flags & MS_RDONLY)) { |
| 780 | /* |
| 781 | * What lock protects sb->s_flags?? |
| 782 | */ |
| 783 | do_remount_sb(sb, MS_RDONLY, NULL, 1); |
| 784 | } |
| 785 | up_write(&sb->s_umount); |
| 786 | spin_lock(&sb_lock); |
| 787 | if (p) |
| 788 | __put_super(p); |
| 789 | p = sb; |
| 790 | } |
| 791 | if (p) |
| 792 | __put_super(p); |
| 793 | spin_unlock(&sb_lock); |
| 794 | kfree(work); |
| 795 | printk("Emergency Remount complete\n"); |
| 796 | } |
| 797 | |
| 798 | void emergency_remount(void) |
| 799 | { |
| 800 | struct work_struct *work; |
| 801 | |
| 802 | work = kmalloc(sizeof(*work), GFP_ATOMIC); |
| 803 | if (work) { |
| 804 | INIT_WORK(work, do_emergency_remount); |
| 805 | schedule_work(work); |
| 806 | } |
| 807 | } |
| 808 | |
| 809 | /* |
| 810 | * Unnamed block devices are dummy devices used by virtual |
| 811 | * filesystems which don't use real block-devices. -- jrs |
| 812 | */ |
| 813 | |
| 814 | static DEFINE_IDA(unnamed_dev_ida); |
| 815 | static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */ |
| 816 | static int unnamed_dev_start = 0; /* don't bother trying below it */ |
| 817 | |
| 818 | int get_anon_bdev(dev_t *p) |
| 819 | { |
| 820 | int dev; |
| 821 | int error; |
| 822 | |
| 823 | retry: |
| 824 | if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0) |
| 825 | return -ENOMEM; |
| 826 | spin_lock(&unnamed_dev_lock); |
| 827 | error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev); |
| 828 | if (!error) |
| 829 | unnamed_dev_start = dev + 1; |
| 830 | spin_unlock(&unnamed_dev_lock); |
| 831 | if (error == -EAGAIN) |
| 832 | /* We raced and lost with another CPU. */ |
| 833 | goto retry; |
| 834 | else if (error) |
| 835 | return -EAGAIN; |
| 836 | |
| 837 | if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) { |
| 838 | spin_lock(&unnamed_dev_lock); |
| 839 | ida_remove(&unnamed_dev_ida, dev); |
| 840 | if (unnamed_dev_start > dev) |
| 841 | unnamed_dev_start = dev; |
| 842 | spin_unlock(&unnamed_dev_lock); |
| 843 | return -EMFILE; |
| 844 | } |
| 845 | *p = MKDEV(0, dev & MINORMASK); |
| 846 | return 0; |
| 847 | } |
| 848 | EXPORT_SYMBOL(get_anon_bdev); |
| 849 | |
| 850 | void free_anon_bdev(dev_t dev) |
| 851 | { |
| 852 | int slot = MINOR(dev); |
| 853 | spin_lock(&unnamed_dev_lock); |
| 854 | ida_remove(&unnamed_dev_ida, slot); |
| 855 | if (slot < unnamed_dev_start) |
| 856 | unnamed_dev_start = slot; |
| 857 | spin_unlock(&unnamed_dev_lock); |
| 858 | } |
| 859 | EXPORT_SYMBOL(free_anon_bdev); |
| 860 | |
| 861 | int set_anon_super(struct super_block *s, void *data) |
| 862 | { |
| 863 | int error = get_anon_bdev(&s->s_dev); |
| 864 | if (!error) |
| 865 | s->s_bdi = &noop_backing_dev_info; |
| 866 | return error; |
| 867 | } |
| 868 | |
| 869 | EXPORT_SYMBOL(set_anon_super); |
| 870 | |
| 871 | void kill_anon_super(struct super_block *sb) |
| 872 | { |
| 873 | dev_t dev = sb->s_dev; |
| 874 | generic_shutdown_super(sb); |
| 875 | free_anon_bdev(dev); |
| 876 | } |
| 877 | |
| 878 | EXPORT_SYMBOL(kill_anon_super); |
| 879 | |
| 880 | void kill_litter_super(struct super_block *sb) |
| 881 | { |
| 882 | if (sb->s_root) |
| 883 | d_genocide(sb->s_root); |
| 884 | kill_anon_super(sb); |
| 885 | } |
| 886 | |
| 887 | EXPORT_SYMBOL(kill_litter_super); |
| 888 | |
| 889 | static int ns_test_super(struct super_block *sb, void *data) |
| 890 | { |
| 891 | return sb->s_fs_info == data; |
| 892 | } |
| 893 | |
| 894 | static int ns_set_super(struct super_block *sb, void *data) |
| 895 | { |
| 896 | sb->s_fs_info = data; |
| 897 | return set_anon_super(sb, NULL); |
| 898 | } |
| 899 | |
| 900 | struct dentry *mount_ns(struct file_system_type *fs_type, int flags, |
| 901 | void *data, int (*fill_super)(struct super_block *, void *, int)) |
| 902 | { |
| 903 | struct super_block *sb; |
| 904 | |
| 905 | sb = sget(fs_type, ns_test_super, ns_set_super, data); |
| 906 | if (IS_ERR(sb)) |
| 907 | return ERR_CAST(sb); |
| 908 | |
| 909 | if (!sb->s_root) { |
| 910 | int err; |
| 911 | sb->s_flags = flags; |
| 912 | err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0); |
| 913 | if (err) { |
| 914 | deactivate_locked_super(sb); |
| 915 | return ERR_PTR(err); |
| 916 | } |
| 917 | |
| 918 | sb->s_flags |= MS_ACTIVE; |
| 919 | } |
| 920 | |
| 921 | return dget(sb->s_root); |
| 922 | } |
| 923 | |
| 924 | EXPORT_SYMBOL(mount_ns); |
| 925 | |
| 926 | #ifdef CONFIG_BLOCK |
| 927 | static int set_bdev_super(struct super_block *s, void *data) |
| 928 | { |
| 929 | s->s_bdev = data; |
| 930 | s->s_dev = s->s_bdev->bd_dev; |
| 931 | |
| 932 | /* |
| 933 | * We set the bdi here to the queue backing, file systems can |
| 934 | * overwrite this in ->fill_super() |
| 935 | */ |
| 936 | s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info; |
| 937 | return 0; |
| 938 | } |
| 939 | |
| 940 | static int test_bdev_super(struct super_block *s, void *data) |
| 941 | { |
| 942 | return (void *)s->s_bdev == data; |
| 943 | } |
| 944 | |
| 945 | struct dentry *mount_bdev(struct file_system_type *fs_type, |
| 946 | int flags, const char *dev_name, void *data, |
| 947 | int (*fill_super)(struct super_block *, void *, int)) |
| 948 | { |
| 949 | struct block_device *bdev; |
| 950 | struct super_block *s; |
| 951 | fmode_t mode = FMODE_READ | FMODE_EXCL; |
| 952 | int error = 0; |
| 953 | |
| 954 | if (!(flags & MS_RDONLY)) |
| 955 | mode |= FMODE_WRITE; |
| 956 | |
| 957 | bdev = blkdev_get_by_path(dev_name, mode, fs_type); |
| 958 | if (IS_ERR(bdev)) |
| 959 | return ERR_CAST(bdev); |
| 960 | |
| 961 | /* |
| 962 | * once the super is inserted into the list by sget, s_umount |
| 963 | * will protect the lockfs code from trying to start a snapshot |
| 964 | * while we are mounting |
| 965 | */ |
| 966 | mutex_lock(&bdev->bd_fsfreeze_mutex); |
| 967 | if (bdev->bd_fsfreeze_count > 0) { |
| 968 | mutex_unlock(&bdev->bd_fsfreeze_mutex); |
| 969 | error = -EBUSY; |
| 970 | goto error_bdev; |
| 971 | } |
| 972 | s = sget(fs_type, test_bdev_super, set_bdev_super, bdev); |
| 973 | mutex_unlock(&bdev->bd_fsfreeze_mutex); |
| 974 | if (IS_ERR(s)) |
| 975 | goto error_s; |
| 976 | |
| 977 | if (s->s_root) { |
| 978 | if ((flags ^ s->s_flags) & MS_RDONLY) { |
| 979 | deactivate_locked_super(s); |
| 980 | error = -EBUSY; |
| 981 | goto error_bdev; |
| 982 | } |
| 983 | |
| 984 | /* |
| 985 | * s_umount nests inside bd_mutex during |
| 986 | * __invalidate_device(). blkdev_put() acquires |
| 987 | * bd_mutex and can't be called under s_umount. Drop |
| 988 | * s_umount temporarily. This is safe as we're |
| 989 | * holding an active reference. |
| 990 | */ |
| 991 | up_write(&s->s_umount); |
| 992 | blkdev_put(bdev, mode); |
| 993 | down_write(&s->s_umount); |
| 994 | } else { |
| 995 | char b[BDEVNAME_SIZE]; |
| 996 | |
| 997 | s->s_flags = flags | MS_NOSEC; |
| 998 | s->s_mode = mode; |
| 999 | strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id)); |
| 1000 | sb_set_blocksize(s, block_size(bdev)); |
| 1001 | error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); |
| 1002 | if (error) { |
| 1003 | deactivate_locked_super(s); |
| 1004 | goto error; |
| 1005 | } |
| 1006 | |
| 1007 | s->s_flags |= MS_ACTIVE; |
| 1008 | bdev->bd_super = s; |
| 1009 | } |
| 1010 | |
| 1011 | return dget(s->s_root); |
| 1012 | |
| 1013 | error_s: |
| 1014 | error = PTR_ERR(s); |
| 1015 | error_bdev: |
| 1016 | blkdev_put(bdev, mode); |
| 1017 | error: |
| 1018 | return ERR_PTR(error); |
| 1019 | } |
| 1020 | EXPORT_SYMBOL(mount_bdev); |
| 1021 | |
| 1022 | void kill_block_super(struct super_block *sb) |
| 1023 | { |
| 1024 | struct block_device *bdev = sb->s_bdev; |
| 1025 | fmode_t mode = sb->s_mode; |
| 1026 | |
| 1027 | bdev->bd_super = NULL; |
| 1028 | generic_shutdown_super(sb); |
| 1029 | sync_blockdev(bdev); |
| 1030 | WARN_ON_ONCE(!(mode & FMODE_EXCL)); |
| 1031 | blkdev_put(bdev, mode | FMODE_EXCL); |
| 1032 | } |
| 1033 | |
| 1034 | EXPORT_SYMBOL(kill_block_super); |
| 1035 | #endif |
| 1036 | |
| 1037 | struct dentry *mount_nodev(struct file_system_type *fs_type, |
| 1038 | int flags, void *data, |
| 1039 | int (*fill_super)(struct super_block *, void *, int)) |
| 1040 | { |
| 1041 | int error; |
| 1042 | struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL); |
| 1043 | |
| 1044 | if (IS_ERR(s)) |
| 1045 | return ERR_CAST(s); |
| 1046 | |
| 1047 | s->s_flags = flags; |
| 1048 | |
| 1049 | error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); |
| 1050 | if (error) { |
| 1051 | deactivate_locked_super(s); |
| 1052 | return ERR_PTR(error); |
| 1053 | } |
| 1054 | s->s_flags |= MS_ACTIVE; |
| 1055 | return dget(s->s_root); |
| 1056 | } |
| 1057 | EXPORT_SYMBOL(mount_nodev); |
| 1058 | |
| 1059 | static int compare_single(struct super_block *s, void *p) |
| 1060 | { |
| 1061 | return 1; |
| 1062 | } |
| 1063 | |
| 1064 | struct dentry *mount_single(struct file_system_type *fs_type, |
| 1065 | int flags, void *data, |
| 1066 | int (*fill_super)(struct super_block *, void *, int)) |
| 1067 | { |
| 1068 | struct super_block *s; |
| 1069 | int error; |
| 1070 | |
| 1071 | s = sget(fs_type, compare_single, set_anon_super, NULL); |
| 1072 | if (IS_ERR(s)) |
| 1073 | return ERR_CAST(s); |
| 1074 | if (!s->s_root) { |
| 1075 | s->s_flags = flags; |
| 1076 | error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); |
| 1077 | if (error) { |
| 1078 | deactivate_locked_super(s); |
| 1079 | return ERR_PTR(error); |
| 1080 | } |
| 1081 | s->s_flags |= MS_ACTIVE; |
| 1082 | } else { |
| 1083 | do_remount_sb(s, flags, data, 0); |
| 1084 | } |
| 1085 | return dget(s->s_root); |
| 1086 | } |
| 1087 | EXPORT_SYMBOL(mount_single); |
| 1088 | |
| 1089 | struct dentry * |
| 1090 | mount_fs(struct file_system_type *type, int flags, const char *name, void *data) |
| 1091 | { |
| 1092 | struct dentry *root; |
| 1093 | struct super_block *sb; |
| 1094 | char *secdata = NULL; |
| 1095 | int error = -ENOMEM; |
| 1096 | |
| 1097 | if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) { |
| 1098 | secdata = alloc_secdata(); |
| 1099 | if (!secdata) |
| 1100 | goto out; |
| 1101 | |
| 1102 | error = security_sb_copy_data(data, secdata); |
| 1103 | if (error) |
| 1104 | goto out_free_secdata; |
| 1105 | } |
| 1106 | |
| 1107 | root = type->mount(type, flags, name, data); |
| 1108 | if (IS_ERR(root)) { |
| 1109 | error = PTR_ERR(root); |
| 1110 | goto out_free_secdata; |
| 1111 | } |
| 1112 | sb = root->d_sb; |
| 1113 | BUG_ON(!sb); |
| 1114 | WARN_ON(!sb->s_bdi); |
| 1115 | WARN_ON(sb->s_bdi == &default_backing_dev_info); |
| 1116 | sb->s_flags |= MS_BORN; |
| 1117 | |
| 1118 | error = security_sb_kern_mount(sb, flags, secdata); |
| 1119 | if (error) |
| 1120 | goto out_sb; |
| 1121 | |
| 1122 | /* |
| 1123 | * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE |
| 1124 | * but s_maxbytes was an unsigned long long for many releases. Throw |
| 1125 | * this warning for a little while to try and catch filesystems that |
| 1126 | * violate this rule. |
| 1127 | */ |
| 1128 | WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to " |
| 1129 | "negative value (%lld)\n", type->name, sb->s_maxbytes); |
| 1130 | |
| 1131 | up_write(&sb->s_umount); |
| 1132 | free_secdata(secdata); |
| 1133 | return root; |
| 1134 | out_sb: |
| 1135 | dput(root); |
| 1136 | deactivate_locked_super(sb); |
| 1137 | out_free_secdata: |
| 1138 | free_secdata(secdata); |
| 1139 | out: |
| 1140 | return ERR_PTR(error); |
| 1141 | } |
| 1142 | |
| 1143 | /** |
| 1144 | * freeze_super - lock the filesystem and force it into a consistent state |
| 1145 | * @sb: the super to lock |
| 1146 | * |
| 1147 | * Syncs the super to make sure the filesystem is consistent and calls the fs's |
| 1148 | * freeze_fs. Subsequent calls to this without first thawing the fs will return |
| 1149 | * -EBUSY. |
| 1150 | */ |
| 1151 | int freeze_super(struct super_block *sb) |
| 1152 | { |
| 1153 | int ret; |
| 1154 | |
| 1155 | atomic_inc(&sb->s_active); |
| 1156 | down_write(&sb->s_umount); |
| 1157 | if (sb->s_frozen) { |
| 1158 | deactivate_locked_super(sb); |
| 1159 | return -EBUSY; |
| 1160 | } |
| 1161 | |
| 1162 | if (!(sb->s_flags & MS_BORN)) { |
| 1163 | up_write(&sb->s_umount); |
| 1164 | return 0; /* sic - it's "nothing to do" */ |
| 1165 | } |
| 1166 | |
| 1167 | if (sb->s_flags & MS_RDONLY) { |
| 1168 | sb->s_frozen = SB_FREEZE_TRANS; |
| 1169 | smp_wmb(); |
| 1170 | up_write(&sb->s_umount); |
| 1171 | return 0; |
| 1172 | } |
| 1173 | |
| 1174 | sb->s_frozen = SB_FREEZE_WRITE; |
| 1175 | smp_wmb(); |
| 1176 | |
| 1177 | sync_filesystem(sb); |
| 1178 | |
| 1179 | sb->s_frozen = SB_FREEZE_TRANS; |
| 1180 | smp_wmb(); |
| 1181 | |
| 1182 | sync_blockdev(sb->s_bdev); |
| 1183 | if (sb->s_op->freeze_fs) { |
| 1184 | ret = sb->s_op->freeze_fs(sb); |
| 1185 | if (ret) { |
| 1186 | printk(KERN_ERR |
| 1187 | "VFS:Filesystem freeze failed\n"); |
| 1188 | sb->s_frozen = SB_UNFROZEN; |
| 1189 | smp_wmb(); |
| 1190 | wake_up(&sb->s_wait_unfrozen); |
| 1191 | deactivate_locked_super(sb); |
| 1192 | return ret; |
| 1193 | } |
| 1194 | } |
| 1195 | up_write(&sb->s_umount); |
| 1196 | return 0; |
| 1197 | } |
| 1198 | EXPORT_SYMBOL(freeze_super); |
| 1199 | |
| 1200 | /** |
| 1201 | * thaw_super -- unlock filesystem |
| 1202 | * @sb: the super to thaw |
| 1203 | * |
| 1204 | * Unlocks the filesystem and marks it writeable again after freeze_super(). |
| 1205 | */ |
| 1206 | int thaw_super(struct super_block *sb) |
| 1207 | { |
| 1208 | int error; |
| 1209 | |
| 1210 | down_write(&sb->s_umount); |
| 1211 | if (sb->s_frozen == SB_UNFROZEN) { |
| 1212 | up_write(&sb->s_umount); |
| 1213 | return -EINVAL; |
| 1214 | } |
| 1215 | |
| 1216 | if (sb->s_flags & MS_RDONLY) |
| 1217 | goto out; |
| 1218 | |
| 1219 | if (sb->s_op->unfreeze_fs) { |
| 1220 | error = sb->s_op->unfreeze_fs(sb); |
| 1221 | if (error) { |
| 1222 | printk(KERN_ERR |
| 1223 | "VFS:Filesystem thaw failed\n"); |
| 1224 | sb->s_frozen = SB_FREEZE_TRANS; |
| 1225 | up_write(&sb->s_umount); |
| 1226 | return error; |
| 1227 | } |
| 1228 | } |
| 1229 | |
| 1230 | out: |
| 1231 | sb->s_frozen = SB_UNFROZEN; |
| 1232 | smp_wmb(); |
| 1233 | wake_up(&sb->s_wait_unfrozen); |
| 1234 | deactivate_locked_super(sb); |
| 1235 | |
| 1236 | return 0; |
| 1237 | } |
| 1238 | EXPORT_SYMBOL(thaw_super); |