| 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* |
| 3 | * linux/fs/super.c |
| 4 | * |
| 5 | * Copyright (C) 1991, 1992 Linus Torvalds |
| 6 | * |
| 7 | * super.c contains code to handle: - mount structures |
| 8 | * - super-block tables |
| 9 | * - filesystem drivers list |
| 10 | * - mount system call |
| 11 | * - umount system call |
| 12 | * - ustat system call |
| 13 | * |
| 14 | * GK 2/5/95 - Changed to support mounting the root fs via NFS |
| 15 | * |
| 16 | * Added kerneld support: Jacques Gelinas and Bjorn Ekwall |
| 17 | * Added change_root: Werner Almesberger & Hans Lermen, Feb '96 |
| 18 | * Added options to /proc/mounts: |
| 19 | * Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996. |
| 20 | * Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998 |
| 21 | * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000 |
| 22 | */ |
| 23 | |
| 24 | #include <linux/export.h> |
| 25 | #include <linux/slab.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 <linux/fscrypt.h> |
| 36 | #include <linux/fsnotify.h> |
| 37 | #include <linux/lockdep.h> |
| 38 | #include <linux/user_namespace.h> |
| 39 | #include <linux/fs_context.h> |
| 40 | #include <uapi/linux/mount.h> |
| 41 | #include "internal.h" |
| 42 | |
| 43 | static int thaw_super_locked(struct super_block *sb); |
| 44 | |
| 45 | static LIST_HEAD(super_blocks); |
| 46 | static DEFINE_SPINLOCK(sb_lock); |
| 47 | |
| 48 | static char *sb_writers_name[SB_FREEZE_LEVELS] = { |
| 49 | "sb_writers", |
| 50 | "sb_pagefaults", |
| 51 | "sb_internal", |
| 52 | }; |
| 53 | |
| 54 | /* |
| 55 | * One thing we have to be careful of with a per-sb shrinker is that we don't |
| 56 | * drop the last active reference to the superblock from within the shrinker. |
| 57 | * If that happens we could trigger unregistering the shrinker from within the |
| 58 | * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we |
| 59 | * take a passive reference to the superblock to avoid this from occurring. |
| 60 | */ |
| 61 | static unsigned long super_cache_scan(struct shrinker *shrink, |
| 62 | struct shrink_control *sc) |
| 63 | { |
| 64 | struct super_block *sb; |
| 65 | long fs_objects = 0; |
| 66 | long total_objects; |
| 67 | long freed = 0; |
| 68 | long dentries; |
| 69 | long inodes; |
| 70 | |
| 71 | sb = container_of(shrink, struct super_block, s_shrink); |
| 72 | |
| 73 | /* |
| 74 | * Deadlock avoidance. We may hold various FS locks, and we don't want |
| 75 | * to recurse into the FS that called us in clear_inode() and friends.. |
| 76 | */ |
| 77 | if (!(sc->gfp_mask & __GFP_FS)) |
| 78 | return SHRINK_STOP; |
| 79 | |
| 80 | if (!trylock_super(sb)) |
| 81 | return SHRINK_STOP; |
| 82 | |
| 83 | if (sb->s_op->nr_cached_objects) |
| 84 | fs_objects = sb->s_op->nr_cached_objects(sb, sc); |
| 85 | |
| 86 | inodes = list_lru_shrink_count(&sb->s_inode_lru, sc); |
| 87 | dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc); |
| 88 | total_objects = dentries + inodes + fs_objects + 1; |
| 89 | if (!total_objects) |
| 90 | total_objects = 1; |
| 91 | |
| 92 | /* proportion the scan between the caches */ |
| 93 | dentries = mult_frac(sc->nr_to_scan, dentries, total_objects); |
| 94 | inodes = mult_frac(sc->nr_to_scan, inodes, total_objects); |
| 95 | fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects); |
| 96 | |
| 97 | /* |
| 98 | * prune the dcache first as the icache is pinned by it, then |
| 99 | * prune the icache, followed by the filesystem specific caches |
| 100 | * |
| 101 | * Ensure that we always scan at least one object - memcg kmem |
| 102 | * accounting uses this to fully empty the caches. |
| 103 | */ |
| 104 | sc->nr_to_scan = dentries + 1; |
| 105 | freed = prune_dcache_sb(sb, sc); |
| 106 | sc->nr_to_scan = inodes + 1; |
| 107 | freed += prune_icache_sb(sb, sc); |
| 108 | |
| 109 | if (fs_objects) { |
| 110 | sc->nr_to_scan = fs_objects + 1; |
| 111 | freed += sb->s_op->free_cached_objects(sb, sc); |
| 112 | } |
| 113 | |
| 114 | up_read(&sb->s_umount); |
| 115 | return freed; |
| 116 | } |
| 117 | |
| 118 | static unsigned long super_cache_count(struct shrinker *shrink, |
| 119 | struct shrink_control *sc) |
| 120 | { |
| 121 | struct super_block *sb; |
| 122 | long total_objects = 0; |
| 123 | |
| 124 | sb = container_of(shrink, struct super_block, s_shrink); |
| 125 | |
| 126 | /* |
| 127 | * We don't call trylock_super() here as it is a scalability bottleneck, |
| 128 | * so we're exposed to partial setup state. The shrinker rwsem does not |
| 129 | * protect filesystem operations backing list_lru_shrink_count() or |
| 130 | * s_op->nr_cached_objects(). Counts can change between |
| 131 | * super_cache_count and super_cache_scan, so we really don't need locks |
| 132 | * here. |
| 133 | * |
| 134 | * However, if we are currently mounting the superblock, the underlying |
| 135 | * filesystem might be in a state of partial construction and hence it |
| 136 | * is dangerous to access it. trylock_super() uses a SB_BORN check to |
| 137 | * avoid this situation, so do the same here. The memory barrier is |
| 138 | * matched with the one in mount_fs() as we don't hold locks here. |
| 139 | */ |
| 140 | if (!(sb->s_flags & SB_BORN)) |
| 141 | return 0; |
| 142 | smp_rmb(); |
| 143 | |
| 144 | if (sb->s_op && sb->s_op->nr_cached_objects) |
| 145 | total_objects = sb->s_op->nr_cached_objects(sb, sc); |
| 146 | |
| 147 | total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc); |
| 148 | total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc); |
| 149 | |
| 150 | if (!total_objects) |
| 151 | return SHRINK_EMPTY; |
| 152 | |
| 153 | total_objects = vfs_pressure_ratio(total_objects); |
| 154 | return total_objects; |
| 155 | } |
| 156 | |
| 157 | static void destroy_super_work(struct work_struct *work) |
| 158 | { |
| 159 | struct super_block *s = container_of(work, struct super_block, |
| 160 | destroy_work); |
| 161 | int i; |
| 162 | |
| 163 | for (i = 0; i < SB_FREEZE_LEVELS; i++) |
| 164 | percpu_free_rwsem(&s->s_writers.rw_sem[i]); |
| 165 | kfree(s); |
| 166 | } |
| 167 | |
| 168 | static void destroy_super_rcu(struct rcu_head *head) |
| 169 | { |
| 170 | struct super_block *s = container_of(head, struct super_block, rcu); |
| 171 | INIT_WORK(&s->destroy_work, destroy_super_work); |
| 172 | schedule_work(&s->destroy_work); |
| 173 | } |
| 174 | |
| 175 | /* Free a superblock that has never been seen by anyone */ |
| 176 | static void destroy_unused_super(struct super_block *s) |
| 177 | { |
| 178 | if (!s) |
| 179 | return; |
| 180 | up_write(&s->s_umount); |
| 181 | list_lru_destroy(&s->s_dentry_lru); |
| 182 | list_lru_destroy(&s->s_inode_lru); |
| 183 | security_sb_free(s); |
| 184 | put_user_ns(s->s_user_ns); |
| 185 | kfree(s->s_subtype); |
| 186 | free_prealloced_shrinker(&s->s_shrink); |
| 187 | /* no delays needed */ |
| 188 | destroy_super_work(&s->destroy_work); |
| 189 | } |
| 190 | |
| 191 | /** |
| 192 | * alloc_super - create new superblock |
| 193 | * @type: filesystem type superblock should belong to |
| 194 | * @flags: the mount flags |
| 195 | * @user_ns: User namespace for the super_block |
| 196 | * |
| 197 | * Allocates and initializes a new &struct super_block. alloc_super() |
| 198 | * returns a pointer new superblock or %NULL if allocation had failed. |
| 199 | */ |
| 200 | static struct super_block *alloc_super(struct file_system_type *type, int flags, |
| 201 | struct user_namespace *user_ns) |
| 202 | { |
| 203 | struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER); |
| 204 | static const struct super_operations default_op; |
| 205 | int i; |
| 206 | |
| 207 | if (!s) |
| 208 | return NULL; |
| 209 | |
| 210 | INIT_LIST_HEAD(&s->s_mounts); |
| 211 | s->s_user_ns = get_user_ns(user_ns); |
| 212 | init_rwsem(&s->s_umount); |
| 213 | lockdep_set_class(&s->s_umount, &type->s_umount_key); |
| 214 | /* |
| 215 | * sget() can have s_umount recursion. |
| 216 | * |
| 217 | * When it cannot find a suitable sb, it allocates a new |
| 218 | * one (this one), and tries again to find a suitable old |
| 219 | * one. |
| 220 | * |
| 221 | * In case that succeeds, it will acquire the s_umount |
| 222 | * lock of the old one. Since these are clearly distrinct |
| 223 | * locks, and this object isn't exposed yet, there's no |
| 224 | * risk of deadlocks. |
| 225 | * |
| 226 | * Annotate this by putting this lock in a different |
| 227 | * subclass. |
| 228 | */ |
| 229 | down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); |
| 230 | |
| 231 | if (security_sb_alloc(s)) |
| 232 | goto fail; |
| 233 | |
| 234 | for (i = 0; i < SB_FREEZE_LEVELS; i++) { |
| 235 | if (__percpu_init_rwsem(&s->s_writers.rw_sem[i], |
| 236 | sb_writers_name[i], |
| 237 | &type->s_writers_key[i])) |
| 238 | goto fail; |
| 239 | } |
| 240 | init_waitqueue_head(&s->s_writers.wait_unfrozen); |
| 241 | s->s_bdi = &noop_backing_dev_info; |
| 242 | s->s_flags = flags; |
| 243 | if (s->s_user_ns != &init_user_ns) |
| 244 | s->s_iflags |= SB_I_NODEV; |
| 245 | INIT_HLIST_NODE(&s->s_instances); |
| 246 | INIT_HLIST_BL_HEAD(&s->s_roots); |
| 247 | mutex_init(&s->s_sync_lock); |
| 248 | INIT_LIST_HEAD(&s->s_inodes); |
| 249 | spin_lock_init(&s->s_inode_list_lock); |
| 250 | INIT_LIST_HEAD(&s->s_inodes_wb); |
| 251 | spin_lock_init(&s->s_inode_wblist_lock); |
| 252 | |
| 253 | s->s_count = 1; |
| 254 | atomic_set(&s->s_active, 1); |
| 255 | mutex_init(&s->s_vfs_rename_mutex); |
| 256 | lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key); |
| 257 | init_rwsem(&s->s_dquot.dqio_sem); |
| 258 | s->s_maxbytes = MAX_NON_LFS; |
| 259 | s->s_op = &default_op; |
| 260 | s->s_time_gran = 1000000000; |
| 261 | s->s_time_min = TIME64_MIN; |
| 262 | s->s_time_max = TIME64_MAX; |
| 263 | s->cleancache_poolid = CLEANCACHE_NO_POOL; |
| 264 | |
| 265 | s->s_shrink.seeks = DEFAULT_SEEKS; |
| 266 | s->s_shrink.scan_objects = super_cache_scan; |
| 267 | s->s_shrink.count_objects = super_cache_count; |
| 268 | s->s_shrink.batch = 1024; |
| 269 | s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE; |
| 270 | if (prealloc_shrinker(&s->s_shrink)) |
| 271 | goto fail; |
| 272 | if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink)) |
| 273 | goto fail; |
| 274 | if (list_lru_init_memcg(&s->s_inode_lru, &s->s_shrink)) |
| 275 | goto fail; |
| 276 | return s; |
| 277 | |
| 278 | fail: |
| 279 | destroy_unused_super(s); |
| 280 | return NULL; |
| 281 | } |
| 282 | |
| 283 | /* Superblock refcounting */ |
| 284 | |
| 285 | /* |
| 286 | * Drop a superblock's refcount. The caller must hold sb_lock. |
| 287 | */ |
| 288 | static void __put_super(struct super_block *s) |
| 289 | { |
| 290 | if (!--s->s_count) { |
| 291 | list_del_init(&s->s_list); |
| 292 | WARN_ON(s->s_dentry_lru.node); |
| 293 | WARN_ON(s->s_inode_lru.node); |
| 294 | WARN_ON(!list_empty(&s->s_mounts)); |
| 295 | security_sb_free(s); |
| 296 | fscrypt_sb_free(s); |
| 297 | put_user_ns(s->s_user_ns); |
| 298 | kfree(s->s_subtype); |
| 299 | call_rcu(&s->rcu, destroy_super_rcu); |
| 300 | } |
| 301 | } |
| 302 | |
| 303 | /** |
| 304 | * put_super - drop a temporary reference to superblock |
| 305 | * @sb: superblock in question |
| 306 | * |
| 307 | * Drops a temporary reference, frees superblock if there's no |
| 308 | * references left. |
| 309 | */ |
| 310 | void put_super(struct super_block *sb) |
| 311 | { |
| 312 | spin_lock(&sb_lock); |
| 313 | __put_super(sb); |
| 314 | spin_unlock(&sb_lock); |
| 315 | } |
| 316 | |
| 317 | |
| 318 | /** |
| 319 | * deactivate_locked_super - drop an active reference to superblock |
| 320 | * @s: superblock to deactivate |
| 321 | * |
| 322 | * Drops an active reference to superblock, converting it into a temporary |
| 323 | * one if there is no other active references left. In that case we |
| 324 | * tell fs driver to shut it down and drop the temporary reference we |
| 325 | * had just acquired. |
| 326 | * |
| 327 | * Caller holds exclusive lock on superblock; that lock is released. |
| 328 | */ |
| 329 | void deactivate_locked_super(struct super_block *s) |
| 330 | { |
| 331 | struct file_system_type *fs = s->s_type; |
| 332 | if (atomic_dec_and_test(&s->s_active)) { |
| 333 | cleancache_invalidate_fs(s); |
| 334 | unregister_shrinker(&s->s_shrink); |
| 335 | fs->kill_sb(s); |
| 336 | |
| 337 | /* |
| 338 | * Since list_lru_destroy() may sleep, we cannot call it from |
| 339 | * put_super(), where we hold the sb_lock. Therefore we destroy |
| 340 | * the lru lists right now. |
| 341 | */ |
| 342 | list_lru_destroy(&s->s_dentry_lru); |
| 343 | list_lru_destroy(&s->s_inode_lru); |
| 344 | |
| 345 | put_filesystem(fs); |
| 346 | put_super(s); |
| 347 | } else { |
| 348 | up_write(&s->s_umount); |
| 349 | } |
| 350 | } |
| 351 | |
| 352 | EXPORT_SYMBOL(deactivate_locked_super); |
| 353 | |
| 354 | /** |
| 355 | * deactivate_super - drop an active reference to superblock |
| 356 | * @s: superblock to deactivate |
| 357 | * |
| 358 | * Variant of deactivate_locked_super(), except that superblock is *not* |
| 359 | * locked by caller. If we are going to drop the final active reference, |
| 360 | * lock will be acquired prior to that. |
| 361 | */ |
| 362 | void deactivate_super(struct super_block *s) |
| 363 | { |
| 364 | if (!atomic_add_unless(&s->s_active, -1, 1)) { |
| 365 | down_write(&s->s_umount); |
| 366 | deactivate_locked_super(s); |
| 367 | } |
| 368 | } |
| 369 | |
| 370 | EXPORT_SYMBOL(deactivate_super); |
| 371 | |
| 372 | /** |
| 373 | * grab_super - acquire an active reference |
| 374 | * @s: reference we are trying to make active |
| 375 | * |
| 376 | * Tries to acquire an active reference. grab_super() is used when we |
| 377 | * had just found a superblock in super_blocks or fs_type->fs_supers |
| 378 | * and want to turn it into a full-blown active reference. grab_super() |
| 379 | * is called with sb_lock held and drops it. Returns 1 in case of |
| 380 | * success, 0 if we had failed (superblock contents was already dead or |
| 381 | * dying when grab_super() had been called). Note that this is only |
| 382 | * called for superblocks not in rundown mode (== ones still on ->fs_supers |
| 383 | * of their type), so increment of ->s_count is OK here. |
| 384 | */ |
| 385 | static int grab_super(struct super_block *s) __releases(sb_lock) |
| 386 | { |
| 387 | s->s_count++; |
| 388 | spin_unlock(&sb_lock); |
| 389 | down_write(&s->s_umount); |
| 390 | if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) { |
| 391 | put_super(s); |
| 392 | return 1; |
| 393 | } |
| 394 | up_write(&s->s_umount); |
| 395 | put_super(s); |
| 396 | return 0; |
| 397 | } |
| 398 | |
| 399 | /* |
| 400 | * trylock_super - try to grab ->s_umount shared |
| 401 | * @sb: reference we are trying to grab |
| 402 | * |
| 403 | * Try to prevent fs shutdown. This is used in places where we |
| 404 | * cannot take an active reference but we need to ensure that the |
| 405 | * filesystem is not shut down while we are working on it. It returns |
| 406 | * false if we cannot acquire s_umount or if we lose the race and |
| 407 | * filesystem already got into shutdown, and returns true with the s_umount |
| 408 | * lock held in read mode in case of success. On successful return, |
| 409 | * the caller must drop the s_umount lock when done. |
| 410 | * |
| 411 | * Note that unlike get_super() et.al. this one does *not* bump ->s_count. |
| 412 | * The reason why it's safe is that we are OK with doing trylock instead |
| 413 | * of down_read(). There's a couple of places that are OK with that, but |
| 414 | * it's very much not a general-purpose interface. |
| 415 | */ |
| 416 | bool trylock_super(struct super_block *sb) |
| 417 | { |
| 418 | if (down_read_trylock(&sb->s_umount)) { |
| 419 | if (!hlist_unhashed(&sb->s_instances) && |
| 420 | sb->s_root && (sb->s_flags & SB_BORN)) |
| 421 | return true; |
| 422 | up_read(&sb->s_umount); |
| 423 | } |
| 424 | |
| 425 | return false; |
| 426 | } |
| 427 | |
| 428 | /** |
| 429 | * generic_shutdown_super - common helper for ->kill_sb() |
| 430 | * @sb: superblock to kill |
| 431 | * |
| 432 | * generic_shutdown_super() does all fs-independent work on superblock |
| 433 | * shutdown. Typical ->kill_sb() should pick all fs-specific objects |
| 434 | * that need destruction out of superblock, call generic_shutdown_super() |
| 435 | * and release aforementioned objects. Note: dentries and inodes _are_ |
| 436 | * taken care of and do not need specific handling. |
| 437 | * |
| 438 | * Upon calling this function, the filesystem may no longer alter or |
| 439 | * rearrange the set of dentries belonging to this super_block, nor may it |
| 440 | * change the attachments of dentries to inodes. |
| 441 | */ |
| 442 | void generic_shutdown_super(struct super_block *sb) |
| 443 | { |
| 444 | const struct super_operations *sop = sb->s_op; |
| 445 | |
| 446 | if (sb->s_root) { |
| 447 | shrink_dcache_for_umount(sb); |
| 448 | sync_filesystem(sb); |
| 449 | sb->s_flags &= ~SB_ACTIVE; |
| 450 | |
| 451 | cgroup_writeback_umount(); |
| 452 | |
| 453 | /* evict all inodes with zero refcount */ |
| 454 | evict_inodes(sb); |
| 455 | /* only nonzero refcount inodes can have marks */ |
| 456 | fsnotify_sb_delete(sb); |
| 457 | security_sb_delete(sb); |
| 458 | |
| 459 | if (sb->s_dio_done_wq) { |
| 460 | destroy_workqueue(sb->s_dio_done_wq); |
| 461 | sb->s_dio_done_wq = NULL; |
| 462 | } |
| 463 | |
| 464 | if (sop->put_super) |
| 465 | sop->put_super(sb); |
| 466 | |
| 467 | if (!list_empty(&sb->s_inodes)) { |
| 468 | printk("VFS: Busy inodes after unmount of %s. " |
| 469 | "Self-destruct in 5 seconds. Have a nice day...\n", |
| 470 | sb->s_id); |
| 471 | } |
| 472 | } |
| 473 | spin_lock(&sb_lock); |
| 474 | /* should be initialized for __put_super_and_need_restart() */ |
| 475 | hlist_del_init(&sb->s_instances); |
| 476 | spin_unlock(&sb_lock); |
| 477 | up_write(&sb->s_umount); |
| 478 | if (sb->s_bdi != &noop_backing_dev_info) { |
| 479 | bdi_put(sb->s_bdi); |
| 480 | sb->s_bdi = &noop_backing_dev_info; |
| 481 | } |
| 482 | } |
| 483 | |
| 484 | EXPORT_SYMBOL(generic_shutdown_super); |
| 485 | |
| 486 | bool mount_capable(struct fs_context *fc) |
| 487 | { |
| 488 | if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT)) |
| 489 | return capable(CAP_SYS_ADMIN); |
| 490 | else |
| 491 | return ns_capable(fc->user_ns, CAP_SYS_ADMIN); |
| 492 | } |
| 493 | |
| 494 | /** |
| 495 | * sget_fc - Find or create a superblock |
| 496 | * @fc: Filesystem context. |
| 497 | * @test: Comparison callback |
| 498 | * @set: Setup callback |
| 499 | * |
| 500 | * Find or create a superblock using the parameters stored in the filesystem |
| 501 | * context and the two callback functions. |
| 502 | * |
| 503 | * If an extant superblock is matched, then that will be returned with an |
| 504 | * elevated reference count that the caller must transfer or discard. |
| 505 | * |
| 506 | * If no match is made, a new superblock will be allocated and basic |
| 507 | * initialisation will be performed (s_type, s_fs_info and s_id will be set and |
| 508 | * the set() callback will be invoked), the superblock will be published and it |
| 509 | * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE |
| 510 | * as yet unset. |
| 511 | */ |
| 512 | struct super_block *sget_fc(struct fs_context *fc, |
| 513 | int (*test)(struct super_block *, struct fs_context *), |
| 514 | int (*set)(struct super_block *, struct fs_context *)) |
| 515 | { |
| 516 | struct super_block *s = NULL; |
| 517 | struct super_block *old; |
| 518 | struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns; |
| 519 | int err; |
| 520 | |
| 521 | retry: |
| 522 | spin_lock(&sb_lock); |
| 523 | if (test) { |
| 524 | hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) { |
| 525 | if (test(old, fc)) |
| 526 | goto share_extant_sb; |
| 527 | } |
| 528 | } |
| 529 | if (!s) { |
| 530 | spin_unlock(&sb_lock); |
| 531 | s = alloc_super(fc->fs_type, fc->sb_flags, user_ns); |
| 532 | if (!s) |
| 533 | return ERR_PTR(-ENOMEM); |
| 534 | goto retry; |
| 535 | } |
| 536 | |
| 537 | s->s_fs_info = fc->s_fs_info; |
| 538 | err = set(s, fc); |
| 539 | if (err) { |
| 540 | s->s_fs_info = NULL; |
| 541 | spin_unlock(&sb_lock); |
| 542 | destroy_unused_super(s); |
| 543 | return ERR_PTR(err); |
| 544 | } |
| 545 | fc->s_fs_info = NULL; |
| 546 | s->s_type = fc->fs_type; |
| 547 | s->s_iflags |= fc->s_iflags; |
| 548 | strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id)); |
| 549 | list_add_tail(&s->s_list, &super_blocks); |
| 550 | hlist_add_head(&s->s_instances, &s->s_type->fs_supers); |
| 551 | spin_unlock(&sb_lock); |
| 552 | get_filesystem(s->s_type); |
| 553 | register_shrinker_prepared(&s->s_shrink); |
| 554 | return s; |
| 555 | |
| 556 | share_extant_sb: |
| 557 | if (user_ns != old->s_user_ns) { |
| 558 | spin_unlock(&sb_lock); |
| 559 | destroy_unused_super(s); |
| 560 | return ERR_PTR(-EBUSY); |
| 561 | } |
| 562 | if (!grab_super(old)) |
| 563 | goto retry; |
| 564 | destroy_unused_super(s); |
| 565 | return old; |
| 566 | } |
| 567 | EXPORT_SYMBOL(sget_fc); |
| 568 | |
| 569 | /** |
| 570 | * sget - find or create a superblock |
| 571 | * @type: filesystem type superblock should belong to |
| 572 | * @test: comparison callback |
| 573 | * @set: setup callback |
| 574 | * @flags: mount flags |
| 575 | * @data: argument to each of them |
| 576 | */ |
| 577 | struct super_block *sget(struct file_system_type *type, |
| 578 | int (*test)(struct super_block *,void *), |
| 579 | int (*set)(struct super_block *,void *), |
| 580 | int flags, |
| 581 | void *data) |
| 582 | { |
| 583 | struct user_namespace *user_ns = current_user_ns(); |
| 584 | struct super_block *s = NULL; |
| 585 | struct super_block *old; |
| 586 | int err; |
| 587 | |
| 588 | /* We don't yet pass the user namespace of the parent |
| 589 | * mount through to here so always use &init_user_ns |
| 590 | * until that changes. |
| 591 | */ |
| 592 | if (flags & SB_SUBMOUNT) |
| 593 | user_ns = &init_user_ns; |
| 594 | |
| 595 | retry: |
| 596 | spin_lock(&sb_lock); |
| 597 | if (test) { |
| 598 | hlist_for_each_entry(old, &type->fs_supers, s_instances) { |
| 599 | if (!test(old, data)) |
| 600 | continue; |
| 601 | if (user_ns != old->s_user_ns) { |
| 602 | spin_unlock(&sb_lock); |
| 603 | destroy_unused_super(s); |
| 604 | return ERR_PTR(-EBUSY); |
| 605 | } |
| 606 | if (!grab_super(old)) |
| 607 | goto retry; |
| 608 | destroy_unused_super(s); |
| 609 | return old; |
| 610 | } |
| 611 | } |
| 612 | if (!s) { |
| 613 | spin_unlock(&sb_lock); |
| 614 | s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns); |
| 615 | if (!s) |
| 616 | return ERR_PTR(-ENOMEM); |
| 617 | goto retry; |
| 618 | } |
| 619 | |
| 620 | err = set(s, data); |
| 621 | if (err) { |
| 622 | spin_unlock(&sb_lock); |
| 623 | destroy_unused_super(s); |
| 624 | return ERR_PTR(err); |
| 625 | } |
| 626 | s->s_type = type; |
| 627 | strlcpy(s->s_id, type->name, sizeof(s->s_id)); |
| 628 | list_add_tail(&s->s_list, &super_blocks); |
| 629 | hlist_add_head(&s->s_instances, &type->fs_supers); |
| 630 | spin_unlock(&sb_lock); |
| 631 | get_filesystem(type); |
| 632 | register_shrinker_prepared(&s->s_shrink); |
| 633 | return s; |
| 634 | } |
| 635 | EXPORT_SYMBOL(sget); |
| 636 | |
| 637 | void drop_super(struct super_block *sb) |
| 638 | { |
| 639 | up_read(&sb->s_umount); |
| 640 | put_super(sb); |
| 641 | } |
| 642 | |
| 643 | EXPORT_SYMBOL(drop_super); |
| 644 | |
| 645 | void drop_super_exclusive(struct super_block *sb) |
| 646 | { |
| 647 | up_write(&sb->s_umount); |
| 648 | put_super(sb); |
| 649 | } |
| 650 | EXPORT_SYMBOL(drop_super_exclusive); |
| 651 | |
| 652 | static void __iterate_supers(void (*f)(struct super_block *)) |
| 653 | { |
| 654 | struct super_block *sb, *p = NULL; |
| 655 | |
| 656 | spin_lock(&sb_lock); |
| 657 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 658 | if (hlist_unhashed(&sb->s_instances)) |
| 659 | continue; |
| 660 | sb->s_count++; |
| 661 | spin_unlock(&sb_lock); |
| 662 | |
| 663 | f(sb); |
| 664 | |
| 665 | spin_lock(&sb_lock); |
| 666 | if (p) |
| 667 | __put_super(p); |
| 668 | p = sb; |
| 669 | } |
| 670 | if (p) |
| 671 | __put_super(p); |
| 672 | spin_unlock(&sb_lock); |
| 673 | } |
| 674 | /** |
| 675 | * iterate_supers - call function for all active superblocks |
| 676 | * @f: function to call |
| 677 | * @arg: argument to pass to it |
| 678 | * |
| 679 | * Scans the superblock list and calls given function, passing it |
| 680 | * locked superblock and given argument. |
| 681 | */ |
| 682 | void iterate_supers(void (*f)(struct super_block *, void *), void *arg) |
| 683 | { |
| 684 | struct super_block *sb, *p = NULL; |
| 685 | |
| 686 | spin_lock(&sb_lock); |
| 687 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 688 | if (hlist_unhashed(&sb->s_instances)) |
| 689 | continue; |
| 690 | sb->s_count++; |
| 691 | spin_unlock(&sb_lock); |
| 692 | |
| 693 | down_read(&sb->s_umount); |
| 694 | if (sb->s_root && (sb->s_flags & SB_BORN)) |
| 695 | f(sb, arg); |
| 696 | up_read(&sb->s_umount); |
| 697 | |
| 698 | spin_lock(&sb_lock); |
| 699 | if (p) |
| 700 | __put_super(p); |
| 701 | p = sb; |
| 702 | } |
| 703 | if (p) |
| 704 | __put_super(p); |
| 705 | spin_unlock(&sb_lock); |
| 706 | } |
| 707 | |
| 708 | /** |
| 709 | * iterate_supers_type - call function for superblocks of given type |
| 710 | * @type: fs type |
| 711 | * @f: function to call |
| 712 | * @arg: argument to pass to it |
| 713 | * |
| 714 | * Scans the superblock list and calls given function, passing it |
| 715 | * locked superblock and given argument. |
| 716 | */ |
| 717 | void iterate_supers_type(struct file_system_type *type, |
| 718 | void (*f)(struct super_block *, void *), void *arg) |
| 719 | { |
| 720 | struct super_block *sb, *p = NULL; |
| 721 | |
| 722 | spin_lock(&sb_lock); |
| 723 | hlist_for_each_entry(sb, &type->fs_supers, s_instances) { |
| 724 | sb->s_count++; |
| 725 | spin_unlock(&sb_lock); |
| 726 | |
| 727 | down_read(&sb->s_umount); |
| 728 | if (sb->s_root && (sb->s_flags & SB_BORN)) |
| 729 | f(sb, arg); |
| 730 | up_read(&sb->s_umount); |
| 731 | |
| 732 | spin_lock(&sb_lock); |
| 733 | if (p) |
| 734 | __put_super(p); |
| 735 | p = sb; |
| 736 | } |
| 737 | if (p) |
| 738 | __put_super(p); |
| 739 | spin_unlock(&sb_lock); |
| 740 | } |
| 741 | |
| 742 | EXPORT_SYMBOL(iterate_supers_type); |
| 743 | |
| 744 | /** |
| 745 | * get_super - get the superblock of a device |
| 746 | * @bdev: device to get the superblock for |
| 747 | * |
| 748 | * Scans the superblock list and finds the superblock of the file system |
| 749 | * mounted on the device given. %NULL is returned if no match is found. |
| 750 | */ |
| 751 | struct super_block *get_super(struct block_device *bdev) |
| 752 | { |
| 753 | struct super_block *sb; |
| 754 | |
| 755 | if (!bdev) |
| 756 | return NULL; |
| 757 | |
| 758 | spin_lock(&sb_lock); |
| 759 | rescan: |
| 760 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 761 | if (hlist_unhashed(&sb->s_instances)) |
| 762 | continue; |
| 763 | if (sb->s_bdev == bdev) { |
| 764 | sb->s_count++; |
| 765 | spin_unlock(&sb_lock); |
| 766 | down_read(&sb->s_umount); |
| 767 | /* still alive? */ |
| 768 | if (sb->s_root && (sb->s_flags & SB_BORN)) |
| 769 | return sb; |
| 770 | up_read(&sb->s_umount); |
| 771 | /* nope, got unmounted */ |
| 772 | spin_lock(&sb_lock); |
| 773 | __put_super(sb); |
| 774 | goto rescan; |
| 775 | } |
| 776 | } |
| 777 | spin_unlock(&sb_lock); |
| 778 | return NULL; |
| 779 | } |
| 780 | |
| 781 | /** |
| 782 | * get_active_super - get an active reference to the superblock of a device |
| 783 | * @bdev: device to get the superblock for |
| 784 | * |
| 785 | * Scans the superblock list and finds the superblock of the file system |
| 786 | * mounted on the device given. Returns the superblock with an active |
| 787 | * reference or %NULL if none was found. |
| 788 | */ |
| 789 | struct super_block *get_active_super(struct block_device *bdev) |
| 790 | { |
| 791 | struct super_block *sb; |
| 792 | |
| 793 | if (!bdev) |
| 794 | return NULL; |
| 795 | |
| 796 | restart: |
| 797 | spin_lock(&sb_lock); |
| 798 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 799 | if (hlist_unhashed(&sb->s_instances)) |
| 800 | continue; |
| 801 | if (sb->s_bdev == bdev) { |
| 802 | if (!grab_super(sb)) |
| 803 | goto restart; |
| 804 | up_write(&sb->s_umount); |
| 805 | return sb; |
| 806 | } |
| 807 | } |
| 808 | spin_unlock(&sb_lock); |
| 809 | return NULL; |
| 810 | } |
| 811 | |
| 812 | struct super_block *user_get_super(dev_t dev, bool excl) |
| 813 | { |
| 814 | struct super_block *sb; |
| 815 | |
| 816 | spin_lock(&sb_lock); |
| 817 | rescan: |
| 818 | list_for_each_entry(sb, &super_blocks, s_list) { |
| 819 | if (hlist_unhashed(&sb->s_instances)) |
| 820 | continue; |
| 821 | if (sb->s_dev == dev) { |
| 822 | sb->s_count++; |
| 823 | spin_unlock(&sb_lock); |
| 824 | if (excl) |
| 825 | down_write(&sb->s_umount); |
| 826 | else |
| 827 | down_read(&sb->s_umount); |
| 828 | /* still alive? */ |
| 829 | if (sb->s_root && (sb->s_flags & SB_BORN)) |
| 830 | return sb; |
| 831 | if (excl) |
| 832 | up_write(&sb->s_umount); |
| 833 | else |
| 834 | up_read(&sb->s_umount); |
| 835 | /* nope, got unmounted */ |
| 836 | spin_lock(&sb_lock); |
| 837 | __put_super(sb); |
| 838 | goto rescan; |
| 839 | } |
| 840 | } |
| 841 | spin_unlock(&sb_lock); |
| 842 | return NULL; |
| 843 | } |
| 844 | |
| 845 | /** |
| 846 | * reconfigure_super - asks filesystem to change superblock parameters |
| 847 | * @fc: The superblock and configuration |
| 848 | * |
| 849 | * Alters the configuration parameters of a live superblock. |
| 850 | */ |
| 851 | int reconfigure_super(struct fs_context *fc) |
| 852 | { |
| 853 | struct super_block *sb = fc->root->d_sb; |
| 854 | int retval; |
| 855 | bool remount_ro = false; |
| 856 | bool force = fc->sb_flags & SB_FORCE; |
| 857 | |
| 858 | if (fc->sb_flags_mask & ~MS_RMT_MASK) |
| 859 | return -EINVAL; |
| 860 | if (sb->s_writers.frozen != SB_UNFROZEN) |
| 861 | return -EBUSY; |
| 862 | |
| 863 | retval = security_sb_remount(sb, fc->security); |
| 864 | if (retval) |
| 865 | return retval; |
| 866 | |
| 867 | if (fc->sb_flags_mask & SB_RDONLY) { |
| 868 | #ifdef CONFIG_BLOCK |
| 869 | if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev && |
| 870 | bdev_read_only(sb->s_bdev)) |
| 871 | return -EACCES; |
| 872 | #endif |
| 873 | |
| 874 | remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb); |
| 875 | } |
| 876 | |
| 877 | if (remount_ro) { |
| 878 | if (!hlist_empty(&sb->s_pins)) { |
| 879 | up_write(&sb->s_umount); |
| 880 | group_pin_kill(&sb->s_pins); |
| 881 | down_write(&sb->s_umount); |
| 882 | if (!sb->s_root) |
| 883 | return 0; |
| 884 | if (sb->s_writers.frozen != SB_UNFROZEN) |
| 885 | return -EBUSY; |
| 886 | remount_ro = !sb_rdonly(sb); |
| 887 | } |
| 888 | } |
| 889 | shrink_dcache_sb(sb); |
| 890 | |
| 891 | /* If we are reconfiguring to RDONLY and current sb is read/write, |
| 892 | * make sure there are no files open for writing. |
| 893 | */ |
| 894 | if (remount_ro) { |
| 895 | if (force) { |
| 896 | sb->s_readonly_remount = 1; |
| 897 | smp_wmb(); |
| 898 | } else { |
| 899 | retval = sb_prepare_remount_readonly(sb); |
| 900 | if (retval) |
| 901 | return retval; |
| 902 | } |
| 903 | } |
| 904 | |
| 905 | if (fc->ops->reconfigure) { |
| 906 | retval = fc->ops->reconfigure(fc); |
| 907 | if (retval) { |
| 908 | if (!force) |
| 909 | goto cancel_readonly; |
| 910 | /* If forced remount, go ahead despite any errors */ |
| 911 | WARN(1, "forced remount of a %s fs returned %i\n", |
| 912 | sb->s_type->name, retval); |
| 913 | } |
| 914 | } |
| 915 | |
| 916 | WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) | |
| 917 | (fc->sb_flags & fc->sb_flags_mask))); |
| 918 | /* Needs to be ordered wrt mnt_is_readonly() */ |
| 919 | smp_wmb(); |
| 920 | sb->s_readonly_remount = 0; |
| 921 | |
| 922 | /* |
| 923 | * Some filesystems modify their metadata via some other path than the |
| 924 | * bdev buffer cache (eg. use a private mapping, or directories in |
| 925 | * pagecache, etc). Also file data modifications go via their own |
| 926 | * mappings. So If we try to mount readonly then copy the filesystem |
| 927 | * from bdev, we could get stale data, so invalidate it to give a best |
| 928 | * effort at coherency. |
| 929 | */ |
| 930 | if (remount_ro && sb->s_bdev) |
| 931 | invalidate_bdev(sb->s_bdev); |
| 932 | return 0; |
| 933 | |
| 934 | cancel_readonly: |
| 935 | sb->s_readonly_remount = 0; |
| 936 | return retval; |
| 937 | } |
| 938 | |
| 939 | static void do_emergency_remount_callback(struct super_block *sb) |
| 940 | { |
| 941 | down_write(&sb->s_umount); |
| 942 | if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) && |
| 943 | !sb_rdonly(sb)) { |
| 944 | struct fs_context *fc; |
| 945 | |
| 946 | fc = fs_context_for_reconfigure(sb->s_root, |
| 947 | SB_RDONLY | SB_FORCE, SB_RDONLY); |
| 948 | if (!IS_ERR(fc)) { |
| 949 | if (parse_monolithic_mount_data(fc, NULL) == 0) |
| 950 | (void)reconfigure_super(fc); |
| 951 | put_fs_context(fc); |
| 952 | } |
| 953 | } |
| 954 | up_write(&sb->s_umount); |
| 955 | } |
| 956 | |
| 957 | static void do_emergency_remount(struct work_struct *work) |
| 958 | { |
| 959 | __iterate_supers(do_emergency_remount_callback); |
| 960 | kfree(work); |
| 961 | printk("Emergency Remount complete\n"); |
| 962 | } |
| 963 | |
| 964 | void emergency_remount(void) |
| 965 | { |
| 966 | struct work_struct *work; |
| 967 | |
| 968 | work = kmalloc(sizeof(*work), GFP_ATOMIC); |
| 969 | if (work) { |
| 970 | INIT_WORK(work, do_emergency_remount); |
| 971 | schedule_work(work); |
| 972 | } |
| 973 | } |
| 974 | |
| 975 | static void do_thaw_all_callback(struct super_block *sb) |
| 976 | { |
| 977 | down_write(&sb->s_umount); |
| 978 | if (sb->s_root && sb->s_flags & SB_BORN) { |
| 979 | emergency_thaw_bdev(sb); |
| 980 | thaw_super_locked(sb); |
| 981 | } else { |
| 982 | up_write(&sb->s_umount); |
| 983 | } |
| 984 | } |
| 985 | |
| 986 | static void do_thaw_all(struct work_struct *work) |
| 987 | { |
| 988 | __iterate_supers(do_thaw_all_callback); |
| 989 | kfree(work); |
| 990 | printk(KERN_WARNING "Emergency Thaw complete\n"); |
| 991 | } |
| 992 | |
| 993 | /** |
| 994 | * emergency_thaw_all -- forcibly thaw every frozen filesystem |
| 995 | * |
| 996 | * Used for emergency unfreeze of all filesystems via SysRq |
| 997 | */ |
| 998 | void emergency_thaw_all(void) |
| 999 | { |
| 1000 | struct work_struct *work; |
| 1001 | |
| 1002 | work = kmalloc(sizeof(*work), GFP_ATOMIC); |
| 1003 | if (work) { |
| 1004 | INIT_WORK(work, do_thaw_all); |
| 1005 | schedule_work(work); |
| 1006 | } |
| 1007 | } |
| 1008 | |
| 1009 | static DEFINE_IDA(unnamed_dev_ida); |
| 1010 | |
| 1011 | /** |
| 1012 | * get_anon_bdev - Allocate a block device for filesystems which don't have one. |
| 1013 | * @p: Pointer to a dev_t. |
| 1014 | * |
| 1015 | * Filesystems which don't use real block devices can call this function |
| 1016 | * to allocate a virtual block device. |
| 1017 | * |
| 1018 | * Context: Any context. Frequently called while holding sb_lock. |
| 1019 | * Return: 0 on success, -EMFILE if there are no anonymous bdevs left |
| 1020 | * or -ENOMEM if memory allocation failed. |
| 1021 | */ |
| 1022 | int get_anon_bdev(dev_t *p) |
| 1023 | { |
| 1024 | int dev; |
| 1025 | |
| 1026 | /* |
| 1027 | * Many userspace utilities consider an FSID of 0 invalid. |
| 1028 | * Always return at least 1 from get_anon_bdev. |
| 1029 | */ |
| 1030 | dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1, |
| 1031 | GFP_ATOMIC); |
| 1032 | if (dev == -ENOSPC) |
| 1033 | dev = -EMFILE; |
| 1034 | if (dev < 0) |
| 1035 | return dev; |
| 1036 | |
| 1037 | *p = MKDEV(0, dev); |
| 1038 | return 0; |
| 1039 | } |
| 1040 | EXPORT_SYMBOL(get_anon_bdev); |
| 1041 | |
| 1042 | void free_anon_bdev(dev_t dev) |
| 1043 | { |
| 1044 | ida_free(&unnamed_dev_ida, MINOR(dev)); |
| 1045 | } |
| 1046 | EXPORT_SYMBOL(free_anon_bdev); |
| 1047 | |
| 1048 | int set_anon_super(struct super_block *s, void *data) |
| 1049 | { |
| 1050 | return get_anon_bdev(&s->s_dev); |
| 1051 | } |
| 1052 | EXPORT_SYMBOL(set_anon_super); |
| 1053 | |
| 1054 | void kill_anon_super(struct super_block *sb) |
| 1055 | { |
| 1056 | dev_t dev = sb->s_dev; |
| 1057 | generic_shutdown_super(sb); |
| 1058 | free_anon_bdev(dev); |
| 1059 | } |
| 1060 | EXPORT_SYMBOL(kill_anon_super); |
| 1061 | |
| 1062 | void kill_litter_super(struct super_block *sb) |
| 1063 | { |
| 1064 | if (sb->s_root) |
| 1065 | d_genocide(sb->s_root); |
| 1066 | kill_anon_super(sb); |
| 1067 | } |
| 1068 | EXPORT_SYMBOL(kill_litter_super); |
| 1069 | |
| 1070 | int set_anon_super_fc(struct super_block *sb, struct fs_context *fc) |
| 1071 | { |
| 1072 | return set_anon_super(sb, NULL); |
| 1073 | } |
| 1074 | EXPORT_SYMBOL(set_anon_super_fc); |
| 1075 | |
| 1076 | static int test_keyed_super(struct super_block *sb, struct fs_context *fc) |
| 1077 | { |
| 1078 | return sb->s_fs_info == fc->s_fs_info; |
| 1079 | } |
| 1080 | |
| 1081 | static int test_single_super(struct super_block *s, struct fs_context *fc) |
| 1082 | { |
| 1083 | return 1; |
| 1084 | } |
| 1085 | |
| 1086 | /** |
| 1087 | * vfs_get_super - Get a superblock with a search key set in s_fs_info. |
| 1088 | * @fc: The filesystem context holding the parameters |
| 1089 | * @keying: How to distinguish superblocks |
| 1090 | * @fill_super: Helper to initialise a new superblock |
| 1091 | * |
| 1092 | * Search for a superblock and create a new one if not found. The search |
| 1093 | * criterion is controlled by @keying. If the search fails, a new superblock |
| 1094 | * is created and @fill_super() is called to initialise it. |
| 1095 | * |
| 1096 | * @keying can take one of a number of values: |
| 1097 | * |
| 1098 | * (1) vfs_get_single_super - Only one superblock of this type may exist on the |
| 1099 | * system. This is typically used for special system filesystems. |
| 1100 | * |
| 1101 | * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have |
| 1102 | * distinct keys (where the key is in s_fs_info). Searching for the same |
| 1103 | * key again will turn up the superblock for that key. |
| 1104 | * |
| 1105 | * (3) vfs_get_independent_super - Multiple superblocks may exist and are |
| 1106 | * unkeyed. Each call will get a new superblock. |
| 1107 | * |
| 1108 | * A permissions check is made by sget_fc() unless we're getting a superblock |
| 1109 | * for a kernel-internal mount or a submount. |
| 1110 | */ |
| 1111 | int vfs_get_super(struct fs_context *fc, |
| 1112 | enum vfs_get_super_keying keying, |
| 1113 | int (*fill_super)(struct super_block *sb, |
| 1114 | struct fs_context *fc)) |
| 1115 | { |
| 1116 | int (*test)(struct super_block *, struct fs_context *); |
| 1117 | struct super_block *sb; |
| 1118 | int err; |
| 1119 | |
| 1120 | switch (keying) { |
| 1121 | case vfs_get_single_super: |
| 1122 | case vfs_get_single_reconf_super: |
| 1123 | test = test_single_super; |
| 1124 | break; |
| 1125 | case vfs_get_keyed_super: |
| 1126 | test = test_keyed_super; |
| 1127 | break; |
| 1128 | case vfs_get_independent_super: |
| 1129 | test = NULL; |
| 1130 | break; |
| 1131 | default: |
| 1132 | BUG(); |
| 1133 | } |
| 1134 | |
| 1135 | sb = sget_fc(fc, test, set_anon_super_fc); |
| 1136 | if (IS_ERR(sb)) |
| 1137 | return PTR_ERR(sb); |
| 1138 | |
| 1139 | if (!sb->s_root) { |
| 1140 | err = fill_super(sb, fc); |
| 1141 | if (err) |
| 1142 | goto error; |
| 1143 | |
| 1144 | sb->s_flags |= SB_ACTIVE; |
| 1145 | fc->root = dget(sb->s_root); |
| 1146 | } else { |
| 1147 | fc->root = dget(sb->s_root); |
| 1148 | if (keying == vfs_get_single_reconf_super) { |
| 1149 | err = reconfigure_super(fc); |
| 1150 | if (err < 0) { |
| 1151 | dput(fc->root); |
| 1152 | fc->root = NULL; |
| 1153 | goto error; |
| 1154 | } |
| 1155 | } |
| 1156 | } |
| 1157 | |
| 1158 | return 0; |
| 1159 | |
| 1160 | error: |
| 1161 | deactivate_locked_super(sb); |
| 1162 | return err; |
| 1163 | } |
| 1164 | EXPORT_SYMBOL(vfs_get_super); |
| 1165 | |
| 1166 | int get_tree_nodev(struct fs_context *fc, |
| 1167 | int (*fill_super)(struct super_block *sb, |
| 1168 | struct fs_context *fc)) |
| 1169 | { |
| 1170 | return vfs_get_super(fc, vfs_get_independent_super, fill_super); |
| 1171 | } |
| 1172 | EXPORT_SYMBOL(get_tree_nodev); |
| 1173 | |
| 1174 | int get_tree_single(struct fs_context *fc, |
| 1175 | int (*fill_super)(struct super_block *sb, |
| 1176 | struct fs_context *fc)) |
| 1177 | { |
| 1178 | return vfs_get_super(fc, vfs_get_single_super, fill_super); |
| 1179 | } |
| 1180 | EXPORT_SYMBOL(get_tree_single); |
| 1181 | |
| 1182 | int get_tree_single_reconf(struct fs_context *fc, |
| 1183 | int (*fill_super)(struct super_block *sb, |
| 1184 | struct fs_context *fc)) |
| 1185 | { |
| 1186 | return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super); |
| 1187 | } |
| 1188 | EXPORT_SYMBOL(get_tree_single_reconf); |
| 1189 | |
| 1190 | int get_tree_keyed(struct fs_context *fc, |
| 1191 | int (*fill_super)(struct super_block *sb, |
| 1192 | struct fs_context *fc), |
| 1193 | void *key) |
| 1194 | { |
| 1195 | fc->s_fs_info = key; |
| 1196 | return vfs_get_super(fc, vfs_get_keyed_super, fill_super); |
| 1197 | } |
| 1198 | EXPORT_SYMBOL(get_tree_keyed); |
| 1199 | |
| 1200 | #ifdef CONFIG_BLOCK |
| 1201 | |
| 1202 | static int set_bdev_super(struct super_block *s, void *data) |
| 1203 | { |
| 1204 | s->s_bdev = data; |
| 1205 | s->s_dev = s->s_bdev->bd_dev; |
| 1206 | s->s_bdi = bdi_get(s->s_bdev->bd_disk->bdi); |
| 1207 | |
| 1208 | if (blk_queue_stable_writes(s->s_bdev->bd_disk->queue)) |
| 1209 | s->s_iflags |= SB_I_STABLE_WRITES; |
| 1210 | return 0; |
| 1211 | } |
| 1212 | |
| 1213 | static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc) |
| 1214 | { |
| 1215 | return set_bdev_super(s, fc->sget_key); |
| 1216 | } |
| 1217 | |
| 1218 | static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc) |
| 1219 | { |
| 1220 | return s->s_bdev == fc->sget_key; |
| 1221 | } |
| 1222 | |
| 1223 | /** |
| 1224 | * get_tree_bdev - Get a superblock based on a single block device |
| 1225 | * @fc: The filesystem context holding the parameters |
| 1226 | * @fill_super: Helper to initialise a new superblock |
| 1227 | */ |
| 1228 | int get_tree_bdev(struct fs_context *fc, |
| 1229 | int (*fill_super)(struct super_block *, |
| 1230 | struct fs_context *)) |
| 1231 | { |
| 1232 | struct block_device *bdev; |
| 1233 | struct super_block *s; |
| 1234 | fmode_t mode = FMODE_READ | FMODE_EXCL; |
| 1235 | int error = 0; |
| 1236 | |
| 1237 | if (!(fc->sb_flags & SB_RDONLY)) |
| 1238 | mode |= FMODE_WRITE; |
| 1239 | |
| 1240 | if (!fc->source) |
| 1241 | return invalf(fc, "No source specified"); |
| 1242 | |
| 1243 | bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type); |
| 1244 | if (IS_ERR(bdev)) { |
| 1245 | errorf(fc, "%s: Can't open blockdev", fc->source); |
| 1246 | return PTR_ERR(bdev); |
| 1247 | } |
| 1248 | |
| 1249 | /* Once the superblock is inserted into the list by sget_fc(), s_umount |
| 1250 | * will protect the lockfs code from trying to start a snapshot while |
| 1251 | * we are mounting |
| 1252 | */ |
| 1253 | mutex_lock(&bdev->bd_fsfreeze_mutex); |
| 1254 | if (bdev->bd_fsfreeze_count > 0) { |
| 1255 | mutex_unlock(&bdev->bd_fsfreeze_mutex); |
| 1256 | warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev); |
| 1257 | blkdev_put(bdev, mode); |
| 1258 | return -EBUSY; |
| 1259 | } |
| 1260 | |
| 1261 | fc->sb_flags |= SB_NOSEC; |
| 1262 | fc->sget_key = bdev; |
| 1263 | s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc); |
| 1264 | mutex_unlock(&bdev->bd_fsfreeze_mutex); |
| 1265 | if (IS_ERR(s)) { |
| 1266 | blkdev_put(bdev, mode); |
| 1267 | return PTR_ERR(s); |
| 1268 | } |
| 1269 | |
| 1270 | if (s->s_root) { |
| 1271 | /* Don't summarily change the RO/RW state. */ |
| 1272 | if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) { |
| 1273 | warnf(fc, "%pg: Can't mount, would change RO state", bdev); |
| 1274 | deactivate_locked_super(s); |
| 1275 | blkdev_put(bdev, mode); |
| 1276 | return -EBUSY; |
| 1277 | } |
| 1278 | |
| 1279 | /* |
| 1280 | * s_umount nests inside open_mutex during |
| 1281 | * __invalidate_device(). blkdev_put() acquires |
| 1282 | * open_mutex and can't be called under s_umount. Drop |
| 1283 | * s_umount temporarily. This is safe as we're |
| 1284 | * holding an active reference. |
| 1285 | */ |
| 1286 | up_write(&s->s_umount); |
| 1287 | blkdev_put(bdev, mode); |
| 1288 | down_write(&s->s_umount); |
| 1289 | } else { |
| 1290 | s->s_mode = mode; |
| 1291 | snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev); |
| 1292 | sb_set_blocksize(s, block_size(bdev)); |
| 1293 | error = fill_super(s, fc); |
| 1294 | if (error) { |
| 1295 | deactivate_locked_super(s); |
| 1296 | return error; |
| 1297 | } |
| 1298 | |
| 1299 | s->s_flags |= SB_ACTIVE; |
| 1300 | bdev->bd_super = s; |
| 1301 | } |
| 1302 | |
| 1303 | BUG_ON(fc->root); |
| 1304 | fc->root = dget(s->s_root); |
| 1305 | return 0; |
| 1306 | } |
| 1307 | EXPORT_SYMBOL(get_tree_bdev); |
| 1308 | |
| 1309 | static int test_bdev_super(struct super_block *s, void *data) |
| 1310 | { |
| 1311 | return (void *)s->s_bdev == data; |
| 1312 | } |
| 1313 | |
| 1314 | struct dentry *mount_bdev(struct file_system_type *fs_type, |
| 1315 | int flags, const char *dev_name, void *data, |
| 1316 | int (*fill_super)(struct super_block *, void *, int)) |
| 1317 | { |
| 1318 | struct block_device *bdev; |
| 1319 | struct super_block *s; |
| 1320 | fmode_t mode = FMODE_READ | FMODE_EXCL; |
| 1321 | int error = 0; |
| 1322 | |
| 1323 | if (!(flags & SB_RDONLY)) |
| 1324 | mode |= FMODE_WRITE; |
| 1325 | |
| 1326 | bdev = blkdev_get_by_path(dev_name, mode, fs_type); |
| 1327 | if (IS_ERR(bdev)) |
| 1328 | return ERR_CAST(bdev); |
| 1329 | |
| 1330 | /* |
| 1331 | * once the super is inserted into the list by sget, s_umount |
| 1332 | * will protect the lockfs code from trying to start a snapshot |
| 1333 | * while we are mounting |
| 1334 | */ |
| 1335 | mutex_lock(&bdev->bd_fsfreeze_mutex); |
| 1336 | if (bdev->bd_fsfreeze_count > 0) { |
| 1337 | mutex_unlock(&bdev->bd_fsfreeze_mutex); |
| 1338 | error = -EBUSY; |
| 1339 | goto error_bdev; |
| 1340 | } |
| 1341 | s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC, |
| 1342 | bdev); |
| 1343 | mutex_unlock(&bdev->bd_fsfreeze_mutex); |
| 1344 | if (IS_ERR(s)) |
| 1345 | goto error_s; |
| 1346 | |
| 1347 | if (s->s_root) { |
| 1348 | if ((flags ^ s->s_flags) & SB_RDONLY) { |
| 1349 | deactivate_locked_super(s); |
| 1350 | error = -EBUSY; |
| 1351 | goto error_bdev; |
| 1352 | } |
| 1353 | |
| 1354 | /* |
| 1355 | * s_umount nests inside open_mutex during |
| 1356 | * __invalidate_device(). blkdev_put() acquires |
| 1357 | * open_mutex and can't be called under s_umount. Drop |
| 1358 | * s_umount temporarily. This is safe as we're |
| 1359 | * holding an active reference. |
| 1360 | */ |
| 1361 | up_write(&s->s_umount); |
| 1362 | blkdev_put(bdev, mode); |
| 1363 | down_write(&s->s_umount); |
| 1364 | } else { |
| 1365 | s->s_mode = mode; |
| 1366 | snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev); |
| 1367 | sb_set_blocksize(s, block_size(bdev)); |
| 1368 | error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); |
| 1369 | if (error) { |
| 1370 | deactivate_locked_super(s); |
| 1371 | goto error; |
| 1372 | } |
| 1373 | |
| 1374 | s->s_flags |= SB_ACTIVE; |
| 1375 | bdev->bd_super = s; |
| 1376 | } |
| 1377 | |
| 1378 | return dget(s->s_root); |
| 1379 | |
| 1380 | error_s: |
| 1381 | error = PTR_ERR(s); |
| 1382 | error_bdev: |
| 1383 | blkdev_put(bdev, mode); |
| 1384 | error: |
| 1385 | return ERR_PTR(error); |
| 1386 | } |
| 1387 | EXPORT_SYMBOL(mount_bdev); |
| 1388 | |
| 1389 | void kill_block_super(struct super_block *sb) |
| 1390 | { |
| 1391 | struct block_device *bdev = sb->s_bdev; |
| 1392 | fmode_t mode = sb->s_mode; |
| 1393 | |
| 1394 | bdev->bd_super = NULL; |
| 1395 | generic_shutdown_super(sb); |
| 1396 | sync_blockdev(bdev); |
| 1397 | WARN_ON_ONCE(!(mode & FMODE_EXCL)); |
| 1398 | blkdev_put(bdev, mode | FMODE_EXCL); |
| 1399 | } |
| 1400 | |
| 1401 | EXPORT_SYMBOL(kill_block_super); |
| 1402 | #endif |
| 1403 | |
| 1404 | struct dentry *mount_nodev(struct file_system_type *fs_type, |
| 1405 | int flags, void *data, |
| 1406 | int (*fill_super)(struct super_block *, void *, int)) |
| 1407 | { |
| 1408 | int error; |
| 1409 | struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL); |
| 1410 | |
| 1411 | if (IS_ERR(s)) |
| 1412 | return ERR_CAST(s); |
| 1413 | |
| 1414 | error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); |
| 1415 | if (error) { |
| 1416 | deactivate_locked_super(s); |
| 1417 | return ERR_PTR(error); |
| 1418 | } |
| 1419 | s->s_flags |= SB_ACTIVE; |
| 1420 | return dget(s->s_root); |
| 1421 | } |
| 1422 | EXPORT_SYMBOL(mount_nodev); |
| 1423 | |
| 1424 | static int reconfigure_single(struct super_block *s, |
| 1425 | int flags, void *data) |
| 1426 | { |
| 1427 | struct fs_context *fc; |
| 1428 | int ret; |
| 1429 | |
| 1430 | /* The caller really need to be passing fc down into mount_single(), |
| 1431 | * then a chunk of this can be removed. [Bollocks -- AV] |
| 1432 | * Better yet, reconfiguration shouldn't happen, but rather the second |
| 1433 | * mount should be rejected if the parameters are not compatible. |
| 1434 | */ |
| 1435 | fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK); |
| 1436 | if (IS_ERR(fc)) |
| 1437 | return PTR_ERR(fc); |
| 1438 | |
| 1439 | ret = parse_monolithic_mount_data(fc, data); |
| 1440 | if (ret < 0) |
| 1441 | goto out; |
| 1442 | |
| 1443 | ret = reconfigure_super(fc); |
| 1444 | out: |
| 1445 | put_fs_context(fc); |
| 1446 | return ret; |
| 1447 | } |
| 1448 | |
| 1449 | static int compare_single(struct super_block *s, void *p) |
| 1450 | { |
| 1451 | return 1; |
| 1452 | } |
| 1453 | |
| 1454 | struct dentry *mount_single(struct file_system_type *fs_type, |
| 1455 | int flags, void *data, |
| 1456 | int (*fill_super)(struct super_block *, void *, int)) |
| 1457 | { |
| 1458 | struct super_block *s; |
| 1459 | int error; |
| 1460 | |
| 1461 | s = sget(fs_type, compare_single, set_anon_super, flags, NULL); |
| 1462 | if (IS_ERR(s)) |
| 1463 | return ERR_CAST(s); |
| 1464 | if (!s->s_root) { |
| 1465 | error = fill_super(s, data, flags & SB_SILENT ? 1 : 0); |
| 1466 | if (!error) |
| 1467 | s->s_flags |= SB_ACTIVE; |
| 1468 | } else { |
| 1469 | error = reconfigure_single(s, flags, data); |
| 1470 | } |
| 1471 | if (unlikely(error)) { |
| 1472 | deactivate_locked_super(s); |
| 1473 | return ERR_PTR(error); |
| 1474 | } |
| 1475 | return dget(s->s_root); |
| 1476 | } |
| 1477 | EXPORT_SYMBOL(mount_single); |
| 1478 | |
| 1479 | /** |
| 1480 | * vfs_get_tree - Get the mountable root |
| 1481 | * @fc: The superblock configuration context. |
| 1482 | * |
| 1483 | * The filesystem is invoked to get or create a superblock which can then later |
| 1484 | * be used for mounting. The filesystem places a pointer to the root to be |
| 1485 | * used for mounting in @fc->root. |
| 1486 | */ |
| 1487 | int vfs_get_tree(struct fs_context *fc) |
| 1488 | { |
| 1489 | struct super_block *sb; |
| 1490 | int error; |
| 1491 | |
| 1492 | if (fc->root) |
| 1493 | return -EBUSY; |
| 1494 | |
| 1495 | /* Get the mountable root in fc->root, with a ref on the root and a ref |
| 1496 | * on the superblock. |
| 1497 | */ |
| 1498 | error = fc->ops->get_tree(fc); |
| 1499 | if (error < 0) |
| 1500 | return error; |
| 1501 | |
| 1502 | if (!fc->root) { |
| 1503 | pr_err("Filesystem %s get_tree() didn't set fc->root\n", |
| 1504 | fc->fs_type->name); |
| 1505 | /* We don't know what the locking state of the superblock is - |
| 1506 | * if there is a superblock. |
| 1507 | */ |
| 1508 | BUG(); |
| 1509 | } |
| 1510 | |
| 1511 | sb = fc->root->d_sb; |
| 1512 | WARN_ON(!sb->s_bdi); |
| 1513 | |
| 1514 | /* |
| 1515 | * Write barrier is for super_cache_count(). We place it before setting |
| 1516 | * SB_BORN as the data dependency between the two functions is the |
| 1517 | * superblock structure contents that we just set up, not the SB_BORN |
| 1518 | * flag. |
| 1519 | */ |
| 1520 | smp_wmb(); |
| 1521 | sb->s_flags |= SB_BORN; |
| 1522 | |
| 1523 | error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL); |
| 1524 | if (unlikely(error)) { |
| 1525 | fc_drop_locked(fc); |
| 1526 | return error; |
| 1527 | } |
| 1528 | |
| 1529 | /* |
| 1530 | * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE |
| 1531 | * but s_maxbytes was an unsigned long long for many releases. Throw |
| 1532 | * this warning for a little while to try and catch filesystems that |
| 1533 | * violate this rule. |
| 1534 | */ |
| 1535 | WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to " |
| 1536 | "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes); |
| 1537 | |
| 1538 | return 0; |
| 1539 | } |
| 1540 | EXPORT_SYMBOL(vfs_get_tree); |
| 1541 | |
| 1542 | /* |
| 1543 | * Setup private BDI for given superblock. It gets automatically cleaned up |
| 1544 | * in generic_shutdown_super(). |
| 1545 | */ |
| 1546 | int super_setup_bdi_name(struct super_block *sb, char *fmt, ...) |
| 1547 | { |
| 1548 | struct backing_dev_info *bdi; |
| 1549 | int err; |
| 1550 | va_list args; |
| 1551 | |
| 1552 | bdi = bdi_alloc(NUMA_NO_NODE); |
| 1553 | if (!bdi) |
| 1554 | return -ENOMEM; |
| 1555 | |
| 1556 | va_start(args, fmt); |
| 1557 | err = bdi_register_va(bdi, fmt, args); |
| 1558 | va_end(args); |
| 1559 | if (err) { |
| 1560 | bdi_put(bdi); |
| 1561 | return err; |
| 1562 | } |
| 1563 | WARN_ON(sb->s_bdi != &noop_backing_dev_info); |
| 1564 | sb->s_bdi = bdi; |
| 1565 | |
| 1566 | return 0; |
| 1567 | } |
| 1568 | EXPORT_SYMBOL(super_setup_bdi_name); |
| 1569 | |
| 1570 | /* |
| 1571 | * Setup private BDI for given superblock. I gets automatically cleaned up |
| 1572 | * in generic_shutdown_super(). |
| 1573 | */ |
| 1574 | int super_setup_bdi(struct super_block *sb) |
| 1575 | { |
| 1576 | static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0); |
| 1577 | |
| 1578 | return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name, |
| 1579 | atomic_long_inc_return(&bdi_seq)); |
| 1580 | } |
| 1581 | EXPORT_SYMBOL(super_setup_bdi); |
| 1582 | |
| 1583 | /** |
| 1584 | * sb_wait_write - wait until all writers to given file system finish |
| 1585 | * @sb: the super for which we wait |
| 1586 | * @level: type of writers we wait for (normal vs page fault) |
| 1587 | * |
| 1588 | * This function waits until there are no writers of given type to given file |
| 1589 | * system. |
| 1590 | */ |
| 1591 | static void sb_wait_write(struct super_block *sb, int level) |
| 1592 | { |
| 1593 | percpu_down_write(sb->s_writers.rw_sem + level-1); |
| 1594 | } |
| 1595 | |
| 1596 | /* |
| 1597 | * We are going to return to userspace and forget about these locks, the |
| 1598 | * ownership goes to the caller of thaw_super() which does unlock(). |
| 1599 | */ |
| 1600 | static void lockdep_sb_freeze_release(struct super_block *sb) |
| 1601 | { |
| 1602 | int level; |
| 1603 | |
| 1604 | for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--) |
| 1605 | percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_); |
| 1606 | } |
| 1607 | |
| 1608 | /* |
| 1609 | * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb). |
| 1610 | */ |
| 1611 | static void lockdep_sb_freeze_acquire(struct super_block *sb) |
| 1612 | { |
| 1613 | int level; |
| 1614 | |
| 1615 | for (level = 0; level < SB_FREEZE_LEVELS; ++level) |
| 1616 | percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_); |
| 1617 | } |
| 1618 | |
| 1619 | static void sb_freeze_unlock(struct super_block *sb) |
| 1620 | { |
| 1621 | int level; |
| 1622 | |
| 1623 | for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--) |
| 1624 | percpu_up_write(sb->s_writers.rw_sem + level); |
| 1625 | } |
| 1626 | |
| 1627 | /** |
| 1628 | * freeze_super - lock the filesystem and force it into a consistent state |
| 1629 | * @sb: the super to lock |
| 1630 | * |
| 1631 | * Syncs the super to make sure the filesystem is consistent and calls the fs's |
| 1632 | * freeze_fs. Subsequent calls to this without first thawing the fs will return |
| 1633 | * -EBUSY. |
| 1634 | * |
| 1635 | * During this function, sb->s_writers.frozen goes through these values: |
| 1636 | * |
| 1637 | * SB_UNFROZEN: File system is normal, all writes progress as usual. |
| 1638 | * |
| 1639 | * SB_FREEZE_WRITE: The file system is in the process of being frozen. New |
| 1640 | * writes should be blocked, though page faults are still allowed. We wait for |
| 1641 | * all writes to complete and then proceed to the next stage. |
| 1642 | * |
| 1643 | * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked |
| 1644 | * but internal fs threads can still modify the filesystem (although they |
| 1645 | * should not dirty new pages or inodes), writeback can run etc. After waiting |
| 1646 | * for all running page faults we sync the filesystem which will clean all |
| 1647 | * dirty pages and inodes (no new dirty pages or inodes can be created when |
| 1648 | * sync is running). |
| 1649 | * |
| 1650 | * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs |
| 1651 | * modification are blocked (e.g. XFS preallocation truncation on inode |
| 1652 | * reclaim). This is usually implemented by blocking new transactions for |
| 1653 | * filesystems that have them and need this additional guard. After all |
| 1654 | * internal writers are finished we call ->freeze_fs() to finish filesystem |
| 1655 | * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is |
| 1656 | * mostly auxiliary for filesystems to verify they do not modify frozen fs. |
| 1657 | * |
| 1658 | * sb->s_writers.frozen is protected by sb->s_umount. |
| 1659 | */ |
| 1660 | int freeze_super(struct super_block *sb) |
| 1661 | { |
| 1662 | int ret; |
| 1663 | |
| 1664 | atomic_inc(&sb->s_active); |
| 1665 | down_write(&sb->s_umount); |
| 1666 | if (sb->s_writers.frozen != SB_UNFROZEN) { |
| 1667 | deactivate_locked_super(sb); |
| 1668 | return -EBUSY; |
| 1669 | } |
| 1670 | |
| 1671 | if (!(sb->s_flags & SB_BORN)) { |
| 1672 | up_write(&sb->s_umount); |
| 1673 | return 0; /* sic - it's "nothing to do" */ |
| 1674 | } |
| 1675 | |
| 1676 | if (sb_rdonly(sb)) { |
| 1677 | /* Nothing to do really... */ |
| 1678 | sb->s_writers.frozen = SB_FREEZE_COMPLETE; |
| 1679 | up_write(&sb->s_umount); |
| 1680 | return 0; |
| 1681 | } |
| 1682 | |
| 1683 | sb->s_writers.frozen = SB_FREEZE_WRITE; |
| 1684 | /* Release s_umount to preserve sb_start_write -> s_umount ordering */ |
| 1685 | up_write(&sb->s_umount); |
| 1686 | sb_wait_write(sb, SB_FREEZE_WRITE); |
| 1687 | down_write(&sb->s_umount); |
| 1688 | |
| 1689 | /* Now we go and block page faults... */ |
| 1690 | sb->s_writers.frozen = SB_FREEZE_PAGEFAULT; |
| 1691 | sb_wait_write(sb, SB_FREEZE_PAGEFAULT); |
| 1692 | |
| 1693 | /* All writers are done so after syncing there won't be dirty data */ |
| 1694 | sync_filesystem(sb); |
| 1695 | |
| 1696 | /* Now wait for internal filesystem counter */ |
| 1697 | sb->s_writers.frozen = SB_FREEZE_FS; |
| 1698 | sb_wait_write(sb, SB_FREEZE_FS); |
| 1699 | |
| 1700 | if (sb->s_op->freeze_fs) { |
| 1701 | ret = sb->s_op->freeze_fs(sb); |
| 1702 | if (ret) { |
| 1703 | printk(KERN_ERR |
| 1704 | "VFS:Filesystem freeze failed\n"); |
| 1705 | sb->s_writers.frozen = SB_UNFROZEN; |
| 1706 | sb_freeze_unlock(sb); |
| 1707 | wake_up(&sb->s_writers.wait_unfrozen); |
| 1708 | deactivate_locked_super(sb); |
| 1709 | return ret; |
| 1710 | } |
| 1711 | } |
| 1712 | /* |
| 1713 | * For debugging purposes so that fs can warn if it sees write activity |
| 1714 | * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super(). |
| 1715 | */ |
| 1716 | sb->s_writers.frozen = SB_FREEZE_COMPLETE; |
| 1717 | lockdep_sb_freeze_release(sb); |
| 1718 | up_write(&sb->s_umount); |
| 1719 | return 0; |
| 1720 | } |
| 1721 | EXPORT_SYMBOL(freeze_super); |
| 1722 | |
| 1723 | static int thaw_super_locked(struct super_block *sb) |
| 1724 | { |
| 1725 | int error; |
| 1726 | |
| 1727 | if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) { |
| 1728 | up_write(&sb->s_umount); |
| 1729 | return -EINVAL; |
| 1730 | } |
| 1731 | |
| 1732 | if (sb_rdonly(sb)) { |
| 1733 | sb->s_writers.frozen = SB_UNFROZEN; |
| 1734 | goto out; |
| 1735 | } |
| 1736 | |
| 1737 | lockdep_sb_freeze_acquire(sb); |
| 1738 | |
| 1739 | if (sb->s_op->unfreeze_fs) { |
| 1740 | error = sb->s_op->unfreeze_fs(sb); |
| 1741 | if (error) { |
| 1742 | printk(KERN_ERR |
| 1743 | "VFS:Filesystem thaw failed\n"); |
| 1744 | lockdep_sb_freeze_release(sb); |
| 1745 | up_write(&sb->s_umount); |
| 1746 | return error; |
| 1747 | } |
| 1748 | } |
| 1749 | |
| 1750 | sb->s_writers.frozen = SB_UNFROZEN; |
| 1751 | sb_freeze_unlock(sb); |
| 1752 | out: |
| 1753 | wake_up(&sb->s_writers.wait_unfrozen); |
| 1754 | deactivate_locked_super(sb); |
| 1755 | return 0; |
| 1756 | } |
| 1757 | |
| 1758 | /** |
| 1759 | * thaw_super -- unlock filesystem |
| 1760 | * @sb: the super to thaw |
| 1761 | * |
| 1762 | * Unlocks the filesystem and marks it writeable again after freeze_super(). |
| 1763 | */ |
| 1764 | int thaw_super(struct super_block *sb) |
| 1765 | { |
| 1766 | down_write(&sb->s_umount); |
| 1767 | return thaw_super_locked(sb); |
| 1768 | } |
| 1769 | EXPORT_SYMBOL(thaw_super); |