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1// SPDX-License-Identifier: GPL-2.02/*3 * linux/fs/super.c4 *5 * Copyright (C) 1991, 1992 Linus Torvalds6 *7 * super.c contains code to handle: - mount structures8 * - super-block tables9 * - filesystem drivers list10 * - mount system call11 * - umount system call12 * - ustat system call13 *14 * GK 2/5/95 - Changed to support mounting the root fs via NFS15 *16 * Added kerneld support: Jacques Gelinas and Bjorn Ekwall17 * Added change_root: Werner Almesberger & Hans Lermen, Feb '9618 * 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-199821 * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 200022 */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/fscrypt.h>35#include <linux/fsnotify.h>36#include <linux/lockdep.h>37#include <linux/user_namespace.h>38#include <linux/fs_context.h>39#include <uapi/linux/mount.h>40#include "internal.h"41 42static int thaw_super_locked(struct super_block *sb, enum freeze_holder who);43 44static LIST_HEAD(super_blocks);45static DEFINE_SPINLOCK(sb_lock);46 47static char *sb_writers_name[SB_FREEZE_LEVELS] = {48 "sb_writers",49 "sb_pagefaults",50 "sb_internal",51};52 53static HWJS_SUSPENDS inline void __super_lock(struct super_block *sb, bool excl)54{55 if (excl)56 down_write(&sb->s_umount);57 else58 down_read(&sb->s_umount);59}60 61static HWJS_SUSPENDS inline void super_unlock(struct super_block *sb, bool excl)62{63 if (excl)64 up_write(&sb->s_umount);65 else66 up_read(&sb->s_umount);67}68 69static HWJS_SUSPENDS inline void __super_lock_excl(struct super_block *sb)70{71 __super_lock(sb, true);72}73 74static HWJS_SUSPENDS inline void super_unlock_excl(struct super_block *sb)75{76 super_unlock(sb, true);77}78 79static HWJS_SUSPENDS inline void super_unlock_shared(struct super_block *sb)80{81 super_unlock(sb, false);82}83 84static bool super_flags(const struct super_block *sb, unsigned int flags)85{86 /*87 * Pairs with smp_store_release() in super_wake() and ensures88 * that we see @flags after we're woken.89 */90 return smp_load_acquire(&sb->s_flags) & flags;91}92 93/**94 * super_lock - wait for superblock to become ready and lock it95 * @sb: superblock to wait for96 * @excl: whether exclusive access is required97 *98 * If the superblock has neither passed through vfs_get_tree() or99 * generic_shutdown_super() yet wait for it to happen. Either superblock100 * creation will succeed and SB_BORN is set by vfs_get_tree() or we're101 * woken and we'll see SB_DYING.102 *103 * The caller must have acquired a temporary reference on @sb->s_count.104 *105 * Return: The function returns true if SB_BORN was set and with106 * s_umount held. The function returns false if SB_DYING was107 * set and without s_umount held.108 */109static HWJS_SUSPENDS __must_check bool super_lock(struct super_block *sb, bool excl)110{111 lockdep_assert_not_held(&sb->s_umount);112 113 /* wait until the superblock is ready or dying */114 wait_var_event(&sb->s_flags, super_flags(sb, SB_BORN | SB_DYING));115 116 /* Don't pointlessly acquire s_umount. */117 if (super_flags(sb, SB_DYING))118 return false;119 120 __super_lock(sb, excl);121 122 /*123 * Has gone through generic_shutdown_super() in the meantime.124 * @sb->s_root is NULL and @sb->s_active is 0. No one needs to125 * grab a reference to this. Tell them so.126 */127 if (sb->s_flags & SB_DYING) {128 super_unlock(sb, excl);129 return false;130 }131 132 WARN_ON_ONCE(!(sb->s_flags & SB_BORN));133 return true;134}135 136/* wait and try to acquire read-side of @sb->s_umount */137static HWJS_SUSPENDS inline bool super_lock_shared(struct super_block *sb)138{139 return super_lock(sb, false);140}141 142/* wait and try to acquire write-side of @sb->s_umount */143static HWJS_SUSPENDS inline bool super_lock_excl(struct super_block *sb)144{145 return super_lock(sb, true);146}147 148/* wake waiters */149#define SUPER_WAKE_FLAGS (SB_BORN | SB_DYING | SB_DEAD)150static void super_wake(struct super_block *sb, unsigned int flag)151{152 WARN_ON_ONCE((flag & ~SUPER_WAKE_FLAGS));153 WARN_ON_ONCE(hweight32(flag & SUPER_WAKE_FLAGS) > 1);154 155 /*156 * Pairs with smp_load_acquire() in super_lock() to make sure157 * all initializations in the superblock are seen by the user158 * seeing SB_BORN sent.159 */160 smp_store_release(&sb->s_flags, sb->s_flags | flag);161 /*162 * Pairs with the barrier in prepare_to_wait_event() to make sure163 * ___wait_var_event() either sees SB_BORN set or164 * waitqueue_active() check in wake_up_var() sees the waiter.165 */166 smp_mb();167 wake_up_var(&sb->s_flags);168}169 170/*171 * One thing we have to be careful of with a per-sb shrinker is that we don't172 * drop the last active reference to the superblock from within the shrinker.173 * If that happens we could trigger unregistering the shrinker from within the174 * shrinker path and that leads to deadlock on the shrinker_mutex. Hence we175 * take a passive reference to the superblock to avoid this from occurring.176 */177static HWJS_SUSPENDS unsigned long super_cache_scan(struct shrinker *shrink,178 struct shrink_control *sc)179{180 struct super_block *sb;181 long fs_objects = 0;182 long total_objects;183 long freed = 0;184 long dentries;185 long inodes;186 187 sb = shrink->private_data;188 189 /*190 * Deadlock avoidance. We may hold various FS locks, and we don't want191 * to recurse into the FS that called us in clear_inode() and friends..192 */193 if (!(sc->gfp_mask & __GFP_FS))194 return SHRINK_STOP;195 196 if (!super_trylock_shared(sb))197 return SHRINK_STOP;198 199 if (sb->s_op->nr_cached_objects)200 fs_objects = sb->s_op->nr_cached_objects(sb, sc);201 202 inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);203 dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);204 total_objects = dentries + inodes + fs_objects + 1;205 if (!total_objects)206 total_objects = 1;207 208 /* proportion the scan between the caches */209 dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);210 inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);211 fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects);212 213 /*214 * prune the dcache first as the icache is pinned by it, then215 * prune the icache, followed by the filesystem specific caches216 *217 * Ensure that we always scan at least one object - memcg kmem218 * accounting uses this to fully empty the caches.219 */220 sc->nr_to_scan = dentries + 1;221 freed = prune_dcache_sb(sb, sc);222 sc->nr_to_scan = inodes + 1;223 freed += prune_icache_sb(sb, sc);224 225 if (fs_objects) {226 sc->nr_to_scan = fs_objects + 1;227 freed += sb->s_op->free_cached_objects(sb, sc);228 }229 230 super_unlock_shared(sb);231 return freed;232}233 234static HWJS_SUSPENDS unsigned long super_cache_count(struct shrinker *shrink,235 struct shrink_control *sc)236{237 struct super_block *sb;238 long total_objects = 0;239 240 sb = shrink->private_data;241 242 /*243 * We don't call super_trylock_shared() here as it is a scalability244 * bottleneck, so we're exposed to partial setup state. The shrinker245 * rwsem does not protect filesystem operations backing246 * list_lru_shrink_count() or s_op->nr_cached_objects(). Counts can247 * change between super_cache_count and super_cache_scan, so we really248 * don't need locks here.249 *250 * However, if we are currently mounting the superblock, the underlying251 * filesystem might be in a state of partial construction and hence it252 * is dangerous to access it. super_trylock_shared() uses a SB_BORN check253 * to avoid this situation, so do the same here. The memory barrier is254 * matched with the one in mount_fs() as we don't hold locks here.255 */256 if (!(sb->s_flags & SB_BORN))257 return 0;258 smp_rmb();259 260 if (sb->s_op && sb->s_op->nr_cached_objects)261 total_objects = sb->s_op->nr_cached_objects(sb, sc);262 263 total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);264 total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);265 266 if (!total_objects)267 return SHRINK_EMPTY;268 269 total_objects = vfs_pressure_ratio(total_objects);270 return total_objects;271}272 273static void destroy_super_work(struct work_struct *work)274{275 struct super_block *s = container_of(work, struct super_block,276 destroy_work);277 fsnotify_sb_free(s);278 security_sb_free(s);279 put_user_ns(s->s_user_ns);280 kfree(s->s_subtype);281 for (int i = 0; i < SB_FREEZE_LEVELS; i++)282 percpu_free_rwsem(&s->s_writers.rw_sem[i]);283 kfree(s);284}285 286static HWJS_SUSPENDS void destroy_super_rcu(struct rcu_head *head)287{288 struct super_block *s = container_of(head, struct super_block, rcu);289 INIT_WORK(&s->destroy_work, destroy_super_work);290 schedule_work(&s->destroy_work);291}292 293/* Free a superblock that has never been seen by anyone */294static HWJS_SUSPENDS void destroy_unused_super(struct super_block *s)295{296 if (!s)297 return;298 super_unlock_excl(s);299 list_lru_destroy(&s->s_dentry_lru);300 list_lru_destroy(&s->s_inode_lru);301 shrinker_free(s->s_shrink);302 /* no delays needed */303 destroy_super_work(&s->destroy_work);304}305 306/**307 * alloc_super - create new superblock308 * @type: filesystem type superblock should belong to309 * @flags: the mount flags310 * @user_ns: User namespace for the super_block311 *312 * Allocates and initializes a new &struct super_block. alloc_super()313 * returns a pointer new superblock or %NULL if allocation had failed.314 */315static HWJS_SUSPENDS struct super_block *alloc_super(struct file_system_type *type, int flags,316 struct user_namespace *user_ns)317{318 struct super_block *s = kzalloc(sizeof(struct super_block), GFP_KERNEL);319 static const struct super_operations default_op;320 int i;321 322 if (!s)323 return NULL;324 325 INIT_LIST_HEAD(&s->s_mounts);326 s->s_user_ns = get_user_ns(user_ns);327 init_rwsem(&s->s_umount);328 lockdep_set_class(&s->s_umount, &type->s_umount_key);329 /*330 * sget() can have s_umount recursion.331 *332 * When it cannot find a suitable sb, it allocates a new333 * one (this one), and tries again to find a suitable old334 * one.335 *336 * In case that succeeds, it will acquire the s_umount337 * lock of the old one. Since these are clearly distrinct338 * locks, and this object isn't exposed yet, there's no339 * risk of deadlocks.340 *341 * Annotate this by putting this lock in a different342 * subclass.343 */344 down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);345 346 if (security_sb_alloc(s))347 goto fail;348 349 for (i = 0; i < SB_FREEZE_LEVELS; i++) {350 if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],351 sb_writers_name[i],352 &type->s_writers_key[i]))353 goto fail;354 }355 s->s_bdi = &noop_backing_dev_info;356 s->s_flags = flags;357 if (s->s_user_ns != &init_user_ns)358 s->s_iflags |= SB_I_NODEV;359 INIT_HLIST_NODE(&s->s_instances);360 INIT_HLIST_BL_HEAD(&s->s_roots);361 mutex_init(&s->s_sync_lock);362 INIT_LIST_HEAD(&s->s_inodes);363 spin_lock_init(&s->s_inode_list_lock);364 INIT_LIST_HEAD(&s->s_inodes_wb);365 spin_lock_init(&s->s_inode_wblist_lock);366 367 s->s_count = 1;368 atomic_set(&s->s_active, 1);369 mutex_init(&s->s_vfs_rename_mutex);370 lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);371 init_rwsem(&s->s_dquot.dqio_sem);372 s->s_maxbytes = MAX_NON_LFS;373 s->s_op = &default_op;374 s->s_time_gran = 1000000000;375 s->s_time_min = TIME64_MIN;376 s->s_time_max = TIME64_MAX;377 378 s->s_shrink = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,379 "sb-%s", type->name);380 if (!s->s_shrink)381 goto fail;382 383 s->s_shrink->scan_objects = super_cache_scan;384 s->s_shrink->count_objects = super_cache_count;385 s->s_shrink->batch = 1024;386 s->s_shrink->private_data = s;387 388 if (list_lru_init_memcg(&s->s_dentry_lru, s->s_shrink))389 goto fail;390 if (list_lru_init_memcg(&s->s_inode_lru, s->s_shrink))391 goto fail;392 return s;393 394fail:395 destroy_unused_super(s);396 return NULL;397}398 399/* Superblock refcounting */400 401/*402 * Drop a superblock's refcount. The caller must hold sb_lock.403 */404static void __put_super(struct super_block *s)405{406 if (!--s->s_count) {407 list_del_init(&s->s_list);408 WARN_ON(s->s_dentry_lru.node);409 WARN_ON(s->s_inode_lru.node);410 WARN_ON(!list_empty(&s->s_mounts));411 call_rcu(&s->rcu, destroy_super_rcu);412 }413}414 415/**416 * put_super - drop a temporary reference to superblock417 * @sb: superblock in question418 *419 * Drops a temporary reference, frees superblock if there's no420 * references left.421 */422void put_super(struct super_block *sb)423{424 spin_lock(&sb_lock);425 __put_super(sb);426 spin_unlock(&sb_lock);427}428 429static HWJS_SUSPENDS void kill_super_notify(struct super_block *sb)430{431 lockdep_assert_not_held(&sb->s_umount);432 433 /* already notified earlier */434 if (sb->s_flags & SB_DEAD)435 return;436 437 /*438 * Remove it from @fs_supers so it isn't found by new439 * sget{_fc}() walkers anymore. Any concurrent mounter still440 * managing to grab a temporary reference is guaranteed to441 * already see SB_DYING and will wait until we notify them about442 * SB_DEAD.443 */444 spin_lock(&sb_lock);445 hlist_del_init(&sb->s_instances);446 spin_unlock(&sb_lock);447 448 /*449 * Let concurrent mounts know that this thing is really dead.450 * We don't need @sb->s_umount here as every concurrent caller451 * will see SB_DYING and either discard the superblock or wait452 * for SB_DEAD.453 */454 super_wake(sb, SB_DEAD);455}456 457/**458 * deactivate_locked_super - drop an active reference to superblock459 * @s: superblock to deactivate460 *461 * Drops an active reference to superblock, converting it into a temporary462 * one if there is no other active references left. In that case we463 * tell fs driver to shut it down and drop the temporary reference we464 * had just acquired.465 *466 * Caller holds exclusive lock on superblock; that lock is released.467 */468void deactivate_locked_super(struct super_block *s)469{470 struct file_system_type *fs = s->s_type;471 if (atomic_dec_and_test(&s->s_active)) {472 shrinker_free(s->s_shrink);473 fs->kill_sb(s);474 475 kill_super_notify(s);476 477 /*478 * Since list_lru_destroy() may sleep, we cannot call it from479 * put_super(), where we hold the sb_lock. Therefore we destroy480 * the lru lists right now.481 */482 list_lru_destroy(&s->s_dentry_lru);483 list_lru_destroy(&s->s_inode_lru);484 485 put_filesystem(fs);486 put_super(s);487 } else {488 super_unlock_excl(s);489 }490}491 492EXPORT_SYMBOL(deactivate_locked_super);493 494/**495 * deactivate_super - drop an active reference to superblock496 * @s: superblock to deactivate497 *498 * Variant of deactivate_locked_super(), except that superblock is *not*499 * locked by caller. If we are going to drop the final active reference,500 * lock will be acquired prior to that.501 */502void deactivate_super(struct super_block *s)503{504 if (!atomic_add_unless(&s->s_active, -1, 1)) {505 __super_lock_excl(s);506 deactivate_locked_super(s);507 }508}509 510EXPORT_SYMBOL(deactivate_super);511 512/**513 * grab_super - acquire an active reference to a superblock514 * @sb: superblock to acquire515 *516 * Acquire a temporary reference on a superblock and try to trade it for517 * an active reference. This is used in sget{_fc}() to wait for a518 * superblock to either become SB_BORN or for it to pass through519 * sb->kill() and be marked as SB_DEAD.520 *521 * Return: This returns true if an active reference could be acquired,522 * false if not.523 */524static HWJS_SUSPENDS bool grab_super(struct super_block *sb)525{526 bool locked;527 528 sb->s_count++;529 spin_unlock(&sb_lock);530 locked = super_lock_excl(sb);531 if (locked) {532 if (atomic_inc_not_zero(&sb->s_active)) {533 put_super(sb);534 return true;535 }536 super_unlock_excl(sb);537 }538 wait_var_event(&sb->s_flags, super_flags(sb, SB_DEAD));539 put_super(sb);540 return false;541}542 543/*544 * super_trylock_shared - try to grab ->s_umount shared545 * @sb: reference we are trying to grab546 *547 * Try to prevent fs shutdown. This is used in places where we548 * cannot take an active reference but we need to ensure that the549 * filesystem is not shut down while we are working on it. It returns550 * false if we cannot acquire s_umount or if we lose the race and551 * filesystem already got into shutdown, and returns true with the s_umount552 * lock held in read mode in case of success. On successful return,553 * the caller must drop the s_umount lock when done.554 *555 * Note that unlike get_super() et.al. this one does *not* bump ->s_count.556 * The reason why it's safe is that we are OK with doing trylock instead557 * of down_read(). There's a couple of places that are OK with that, but558 * it's very much not a general-purpose interface.559 */560bool super_trylock_shared(struct super_block *sb)561{562 if (down_read_trylock(&sb->s_umount)) {563 if (!(sb->s_flags & SB_DYING) && sb->s_root &&564 (sb->s_flags & SB_BORN))565 return true;566 super_unlock_shared(sb);567 }568 569 return false;570}571 572/**573 * retire_super - prevents superblock from being reused574 * @sb: superblock to retire575 *576 * The function marks superblock to be ignored in superblock test, which577 * prevents it from being reused for any new mounts. If the superblock has578 * a private bdi, it also unregisters it, but doesn't reduce the refcount579 * of the superblock to prevent potential races. The refcount is reduced580 * by generic_shutdown_super(). The function can not be called581 * concurrently with generic_shutdown_super(). It is safe to call the582 * function multiple times, subsequent calls have no effect.583 *584 * The marker will affect the re-use only for block-device-based585 * superblocks. Other superblocks will still get marked if this function586 * is used, but that will not affect their reusability.587 */588void retire_super(struct super_block *sb)589{590 WARN_ON(!sb->s_bdev);591 __super_lock_excl(sb);592 if (sb->s_iflags & SB_I_PERSB_BDI) {593 bdi_unregister(sb->s_bdi);594 sb->s_iflags &= ~SB_I_PERSB_BDI;595 }596 sb->s_iflags |= SB_I_RETIRED;597 super_unlock_excl(sb);598}599EXPORT_SYMBOL(retire_super);600 601/**602 * generic_shutdown_super - common helper for ->kill_sb()603 * @sb: superblock to kill604 *605 * generic_shutdown_super() does all fs-independent work on superblock606 * shutdown. Typical ->kill_sb() should pick all fs-specific objects607 * that need destruction out of superblock, call generic_shutdown_super()608 * and release aforementioned objects. Note: dentries and inodes _are_609 * taken care of and do not need specific handling.610 *611 * Upon calling this function, the filesystem may no longer alter or612 * rearrange the set of dentries belonging to this super_block, nor may it613 * change the attachments of dentries to inodes.614 */615void generic_shutdown_super(struct super_block *sb)616{617 const struct super_operations *sop = sb->s_op;618 619 if (sb->s_root) {620 shrink_dcache_for_umount(sb);621 sync_filesystem(sb);622 sb->s_flags &= ~SB_ACTIVE;623 624 cgroup_writeback_umount(sb);625 626 /* Evict all inodes with zero refcount. */627 evict_inodes(sb);628 629 /*630 * Clean up and evict any inodes that still have references due631 * to fsnotify or the security policy.632 */633 fsnotify_sb_delete(sb);634 security_sb_delete(sb);635 636 if (sb->s_dio_done_wq) {637 destroy_workqueue(sb->s_dio_done_wq);638 sb->s_dio_done_wq = NULL;639 }640 641 if (sop->put_super)642 sop->put_super(sb);643 644 /*645 * Now that all potentially-encrypted inodes have been evicted,646 * the fscrypt keyring can be destroyed.647 */648 fscrypt_destroy_keyring(sb);649 650 if (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes),651 "VFS: Busy inodes after unmount of %s (%s)",652 sb->s_id, sb->s_type->name)) {653 /*654 * Adding a proper bailout path here would be hard, but655 * we can at least make it more likely that a later656 * iput_final() or such crashes cleanly.657 */658 struct inode *inode;659 660 spin_lock(&sb->s_inode_list_lock);661 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {662 inode->i_op = VFS_PTR_POISON;663 inode->i_sb = VFS_PTR_POISON;664 inode->i_mapping = VFS_PTR_POISON;665 }666 spin_unlock(&sb->s_inode_list_lock);667 }668 }669 /*670 * Broadcast to everyone that grabbed a temporary reference to this671 * superblock before we removed it from @fs_supers that the superblock672 * is dying. Every walker of @fs_supers outside of sget{_fc}() will now673 * discard this superblock and treat it as dead.674 *675 * We leave the superblock on @fs_supers so it can be found by676 * sget{_fc}() until we passed sb->kill_sb().677 */678 super_wake(sb, SB_DYING);679 super_unlock_excl(sb);680 if (sb->s_bdi != &noop_backing_dev_info) {681 if (sb->s_iflags & SB_I_PERSB_BDI)682 bdi_unregister(sb->s_bdi);683 bdi_put(sb->s_bdi);684 sb->s_bdi = &noop_backing_dev_info;685 }686}687 688EXPORT_SYMBOL(generic_shutdown_super);689 690bool mount_capable(struct fs_context *fc)691{692 if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))693 return capable(CAP_SYS_ADMIN);694 else695 return ns_capable(fc->user_ns, CAP_SYS_ADMIN);696}697 698/**699 * sget_fc - Find or create a superblock700 * @fc: Filesystem context.701 * @test: Comparison callback702 * @set: Setup callback703 *704 * Create a new superblock or find an existing one.705 *706 * The @test callback is used to find a matching existing superblock.707 * Whether or not the requested parameters in @fc are taken into account708 * is specific to the @test callback that is used. They may even be709 * completely ignored.710 *711 * If an extant superblock is matched, it will be returned unless:712 *713 * (1) the namespace the filesystem context @fc and the extant714 * superblock's namespace differ715 *716 * (2) the filesystem context @fc has requested that reusing an extant717 * superblock is not allowed718 *719 * In both cases EBUSY will be returned.720 *721 * If no match is made, a new superblock will be allocated and basic722 * initialisation will be performed (s_type, s_fs_info and s_id will be723 * set and the @set callback will be invoked), the superblock will be724 * published and it will be returned in a partially constructed state725 * with SB_BORN and SB_ACTIVE as yet unset.726 *727 * Return: On success, an extant or newly created superblock is728 * returned. On failure an error pointer is returned.729 */730struct super_block *sget_fc(struct fs_context *fc,731 int (*test)(struct super_block *, struct fs_context *),732 int (*set)(struct super_block *, struct fs_context *))733{734 struct super_block *s = NULL;735 struct super_block *old;736 struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;737 int err;738 739 /*740 * Never allow s_user_ns != &init_user_ns when FS_USERNS_MOUNT is741 * not set, as the filesystem is likely unprepared to handle it.742 * This can happen when fsconfig() is called from init_user_ns with743 * an fs_fd opened in another user namespace.744 */745 if (user_ns != &init_user_ns && !(fc->fs_type->fs_flags & FS_USERNS_MOUNT)) {746 errorfc(fc, "VFS: Mounting from non-initial user namespace is not allowed");747 return ERR_PTR(-EPERM);748 }749 750retry:751 spin_lock(&sb_lock);752 if (test) {753 hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {754 if (test(old, fc))755 goto share_extant_sb;756 }757 }758 if (!s) {759 spin_unlock(&sb_lock);760 s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);761 if (!s)762 return ERR_PTR(-ENOMEM);763 goto retry;764 }765 766 s->s_fs_info = fc->s_fs_info;767 err = set(s, fc);768 if (err) {769 s->s_fs_info = NULL;770 spin_unlock(&sb_lock);771 destroy_unused_super(s);772 return ERR_PTR(err);773 }774 fc->s_fs_info = NULL;775 s->s_type = fc->fs_type;776 s->s_iflags |= fc->s_iflags;777 strscpy(s->s_id, s->s_type->name, sizeof(s->s_id));778 /*779 * Make the superblock visible on @super_blocks and @fs_supers.780 * It's in a nascent state and users should wait on SB_BORN or781 * SB_DYING to be set.782 */783 list_add_tail(&s->s_list, &super_blocks);784 hlist_add_head(&s->s_instances, &s->s_type->fs_supers);785 spin_unlock(&sb_lock);786 get_filesystem(s->s_type);787 shrinker_register(s->s_shrink);788 return s;789 790share_extant_sb:791 if (user_ns != old->s_user_ns || fc->exclusive) {792 spin_unlock(&sb_lock);793 destroy_unused_super(s);794 if (fc->exclusive)795 warnfc(fc, "reusing existing filesystem not allowed");796 else797 warnfc(fc, "reusing existing filesystem in another namespace not allowed");798 return ERR_PTR(-EBUSY);799 }800 if (!grab_super(old))801 goto retry;802 destroy_unused_super(s);803 return old;804}805EXPORT_SYMBOL(sget_fc);806 807/**808 * sget - find or create a superblock809 * @type: filesystem type superblock should belong to810 * @test: comparison callback811 * @set: setup callback812 * @flags: mount flags813 * @data: argument to each of them814 */815struct super_block *sget(struct file_system_type *type,816 int (*test)(struct super_block *,void *),817 int (*set)(struct super_block *,void *),818 int flags,819 void *data)820{821 struct user_namespace *user_ns = current_user_ns();822 struct super_block *s = NULL;823 struct super_block *old;824 int err;825 826 /* We don't yet pass the user namespace of the parent827 * mount through to here so always use &init_user_ns828 * until that changes.829 */830 if (flags & SB_SUBMOUNT)831 user_ns = &init_user_ns;832 833retry:834 spin_lock(&sb_lock);835 if (test) {836 hlist_for_each_entry(old, &type->fs_supers, s_instances) {837 if (!test(old, data))838 continue;839 if (user_ns != old->s_user_ns) {840 spin_unlock(&sb_lock);841 destroy_unused_super(s);842 return ERR_PTR(-EBUSY);843 }844 if (!grab_super(old))845 goto retry;846 destroy_unused_super(s);847 return old;848 }849 }850 if (!s) {851 spin_unlock(&sb_lock);852 s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);853 if (!s)854 return ERR_PTR(-ENOMEM);855 goto retry;856 }857 858 err = set(s, data);859 if (err) {860 spin_unlock(&sb_lock);861 destroy_unused_super(s);862 return ERR_PTR(err);863 }864 s->s_type = type;865 strscpy(s->s_id, type->name, sizeof(s->s_id));866 list_add_tail(&s->s_list, &super_blocks);867 hlist_add_head(&s->s_instances, &type->fs_supers);868 spin_unlock(&sb_lock);869 get_filesystem(type);870 shrinker_register(s->s_shrink);871 return s;872}873EXPORT_SYMBOL(sget);874 875void drop_super(struct super_block *sb)876{877 super_unlock_shared(sb);878 put_super(sb);879}880 881EXPORT_SYMBOL(drop_super);882 883void drop_super_exclusive(struct super_block *sb)884{885 super_unlock_excl(sb);886 put_super(sb);887}888EXPORT_SYMBOL(drop_super_exclusive);889 890static HWJS_SUSPENDS void __iterate_supers(void (*f)(struct super_block *))891{892 struct super_block *sb, *p = NULL;893 894 spin_lock(&sb_lock);895 list_for_each_entry(sb, &super_blocks, s_list) {896 if (super_flags(sb, SB_DYING))897 continue;898 sb->s_count++;899 spin_unlock(&sb_lock);900 901 f(sb);902 903 spin_lock(&sb_lock);904 if (p)905 __put_super(p);906 p = sb;907 }908 if (p)909 __put_super(p);910 spin_unlock(&sb_lock);911}912/**913 * iterate_supers - call function for all active superblocks914 * @f: function to call915 * @arg: argument to pass to it916 *917 * Scans the superblock list and calls given function, passing it918 * locked superblock and given argument.919 */920void iterate_supers(void (*f)(struct super_block *, void *), void *arg)921{922 struct super_block *sb, *p = NULL;923 924 spin_lock(&sb_lock);925 list_for_each_entry(sb, &super_blocks, s_list) {926 bool locked;927 928 sb->s_count++;929 spin_unlock(&sb_lock);930 931 locked = super_lock_shared(sb);932 if (locked) {933 if (sb->s_root)934 f(sb, arg);935 super_unlock_shared(sb);936 }937 938 spin_lock(&sb_lock);939 if (p)940 __put_super(p);941 p = sb;942 }943 if (p)944 __put_super(p);945 spin_unlock(&sb_lock);946}947 948/**949 * iterate_supers_type - call function for superblocks of given type950 * @type: fs type951 * @f: function to call952 * @arg: argument to pass to it953 *954 * Scans the superblock list and calls given function, passing it955 * locked superblock and given argument.956 */957void iterate_supers_type(struct file_system_type *type,958 void (*f)(struct super_block *, void *), void *arg)959{960 struct super_block *sb, *p = NULL;961 962 spin_lock(&sb_lock);963 hlist_for_each_entry(sb, &type->fs_supers, s_instances) {964 bool locked;965 966 sb->s_count++;967 spin_unlock(&sb_lock);968 969 locked = super_lock_shared(sb);970 if (locked) {971 if (sb->s_root)972 f(sb, arg);973 super_unlock_shared(sb);974 }975 976 spin_lock(&sb_lock);977 if (p)978 __put_super(p);979 p = sb;980 }981 if (p)982 __put_super(p);983 spin_unlock(&sb_lock);984}985 986EXPORT_SYMBOL(iterate_supers_type);987 988struct super_block *user_get_super(dev_t dev, bool excl)989{990 struct super_block *sb;991 992 spin_lock(&sb_lock);993 list_for_each_entry(sb, &super_blocks, s_list) {994 if (sb->s_dev == dev) {995 bool locked;996 997 sb->s_count++;998 spin_unlock(&sb_lock);999 /* still alive? */1000 locked = super_lock(sb, excl);1001 if (locked) {1002 if (sb->s_root)1003 return sb;1004 super_unlock(sb, excl);1005 }1006 /* nope, got unmounted */1007 spin_lock(&sb_lock);1008 __put_super(sb);1009 break;1010 }1011 }1012 spin_unlock(&sb_lock);1013 return NULL;1014}1015 1016/**1017 * reconfigure_super - asks filesystem to change superblock parameters1018 * @fc: The superblock and configuration1019 *1020 * Alters the configuration parameters of a live superblock.1021 */1022int reconfigure_super(struct fs_context *fc)1023{1024 struct super_block *sb = fc->root->d_sb;1025 int retval;1026 bool remount_ro = false;1027 bool remount_rw = false;1028 bool force = fc->sb_flags & SB_FORCE;1029 1030 if (fc->sb_flags_mask & ~MS_RMT_MASK)1031 return -EINVAL;1032 if (sb->s_writers.frozen != SB_UNFROZEN)1033 return -EBUSY;1034 1035 retval = security_sb_remount(sb, fc->security);1036 if (retval)1037 return retval;1038 1039 if (fc->sb_flags_mask & SB_RDONLY) {1040#ifdef CONFIG_BLOCK1041 if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&1042 bdev_read_only(sb->s_bdev))1043 return -EACCES;1044#endif1045 remount_rw = !(fc->sb_flags & SB_RDONLY) && sb_rdonly(sb);1046 remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);1047 }1048 1049 if (remount_ro) {1050 if (!hlist_empty(&sb->s_pins)) {1051 super_unlock_excl(sb);1052 group_pin_kill(&sb->s_pins);1053 __super_lock_excl(sb);1054 if (!sb->s_root)1055 return 0;1056 if (sb->s_writers.frozen != SB_UNFROZEN)1057 return -EBUSY;1058 remount_ro = !sb_rdonly(sb);1059 }1060 }1061 shrink_dcache_sb(sb);1062 1063 /* If we are reconfiguring to RDONLY and current sb is read/write,1064 * make sure there are no files open for writing.1065 */1066 if (remount_ro) {1067 if (force) {1068 sb_start_ro_state_change(sb);1069 } else {1070 retval = sb_prepare_remount_readonly(sb);1071 if (retval)1072 return retval;1073 }1074 } else if (remount_rw) {1075 /*1076 * Protect filesystem's reconfigure code from writes from1077 * userspace until reconfigure finishes.1078 */1079 sb_start_ro_state_change(sb);1080 }1081 1082 if (fc->ops->reconfigure) {1083 retval = fc->ops->reconfigure(fc);1084 if (retval) {1085 if (!force)1086 goto cancel_readonly;1087 /* If forced remount, go ahead despite any errors */1088 WARN(1, "forced remount of a %s fs returned %i\n",1089 sb->s_type->name, retval);1090 }1091 }1092 1093 WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |1094 (fc->sb_flags & fc->sb_flags_mask)));1095 sb_end_ro_state_change(sb);1096 1097 /*1098 * Some filesystems modify their metadata via some other path than the1099 * bdev buffer cache (eg. use a private mapping, or directories in1100 * pagecache, etc). Also file data modifications go via their own1101 * mappings. So If we try to mount readonly then copy the filesystem1102 * from bdev, we could get stale data, so invalidate it to give a best1103 * effort at coherency.1104 */1105 if (remount_ro && sb->s_bdev)1106 invalidate_bdev(sb->s_bdev);1107 return 0;1108 1109cancel_readonly:1110 sb_end_ro_state_change(sb);1111 return retval;1112}1113 1114static HWJS_SUSPENDS void do_emergency_remount_callback(struct super_block *sb)1115{1116 bool locked = super_lock_excl(sb);1117 1118 if (locked && sb->s_root && sb->s_bdev && !sb_rdonly(sb)) {1119 struct fs_context *fc;1120 1121 fc = fs_context_for_reconfigure(sb->s_root,1122 SB_RDONLY | SB_FORCE, SB_RDONLY);1123 if (!IS_ERR(fc)) {1124 if (parse_monolithic_mount_data(fc, NULL) == 0)1125 (void)reconfigure_super(fc);1126 put_fs_context(fc);1127 }1128 }1129 if (locked)1130 super_unlock_excl(sb);1131}1132 1133static HWJS_SUSPENDS void do_emergency_remount(struct work_struct *work)1134{1135 __iterate_supers(do_emergency_remount_callback);1136 kfree(work);1137 printk("Emergency Remount complete\n");1138}1139 1140void emergency_remount(void)1141{1142 struct work_struct *work;1143 1144 work = kmalloc(sizeof(*work), GFP_ATOMIC);1145 if (work) {1146 INIT_WORK(work, do_emergency_remount);1147 schedule_work(work);1148 }1149}1150 1151static HWJS_SUSPENDS void do_thaw_all_callback(struct super_block *sb)1152{1153 bool locked = super_lock_excl(sb);1154 1155 if (locked && sb->s_root) {1156 if (IS_ENABLED(CONFIG_BLOCK))1157 while (sb->s_bdev && !bdev_thaw(sb->s_bdev))1158 pr_warn("Emergency Thaw on %pg\n", sb->s_bdev);1159 thaw_super_locked(sb, FREEZE_HOLDER_USERSPACE);1160 return;1161 }1162 if (locked)1163 super_unlock_excl(sb);1164}1165 1166static HWJS_SUSPENDS void do_thaw_all(struct work_struct *work)1167{1168 __iterate_supers(do_thaw_all_callback);1169 kfree(work);1170 printk(KERN_WARNING "Emergency Thaw complete\n");1171}1172 1173/**1174 * emergency_thaw_all -- forcibly thaw every frozen filesystem1175 *1176 * Used for emergency unfreeze of all filesystems via SysRq1177 */1178void emergency_thaw_all(void)1179{1180 struct work_struct *work;1181 1182 work = kmalloc(sizeof(*work), GFP_ATOMIC);1183 if (work) {1184 INIT_WORK(work, do_thaw_all);1185 schedule_work(work);1186 }1187}1188 1189static DEFINE_IDA(unnamed_dev_ida);1190 1191/**1192 * get_anon_bdev - Allocate a block device for filesystems which don't have one.1193 * @p: Pointer to a dev_t.1194 *1195 * Filesystems which don't use real block devices can call this function1196 * to allocate a virtual block device.1197 *1198 * Context: Any context. Frequently called while holding sb_lock.1199 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left1200 * or -ENOMEM if memory allocation failed.1201 */1202int get_anon_bdev(dev_t *p)1203{1204 int dev;1205 1206 /*1207 * Many userspace utilities consider an FSID of 0 invalid.1208 * Always return at least 1 from get_anon_bdev.1209 */1210 dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,1211 GFP_ATOMIC);1212 if (dev == -ENOSPC)1213 dev = -EMFILE;1214 if (dev < 0)1215 return dev;1216 1217 *p = MKDEV(0, dev);1218 return 0;1219}1220EXPORT_SYMBOL(get_anon_bdev);1221 1222void free_anon_bdev(dev_t dev)1223{1224 ida_free(&unnamed_dev_ida, MINOR(dev));1225}1226EXPORT_SYMBOL(free_anon_bdev);1227 1228int set_anon_super(struct super_block *s, void *data)1229{1230 return get_anon_bdev(&s->s_dev);1231}1232EXPORT_SYMBOL(set_anon_super);1233 1234void kill_anon_super(struct super_block *sb)1235{1236 dev_t dev = sb->s_dev;1237 generic_shutdown_super(sb);1238 kill_super_notify(sb);1239 free_anon_bdev(dev);1240}1241EXPORT_SYMBOL(kill_anon_super);1242 1243void kill_litter_super(struct super_block *sb)1244{1245 if (sb->s_root)1246 d_genocide(sb->s_root);1247 kill_anon_super(sb);1248}1249EXPORT_SYMBOL(kill_litter_super);1250 1251int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)1252{1253 return set_anon_super(sb, NULL);1254}1255EXPORT_SYMBOL(set_anon_super_fc);1256 1257static int test_keyed_super(struct super_block *sb, struct fs_context *fc)1258{1259 return sb->s_fs_info == fc->s_fs_info;1260}1261 1262static int test_single_super(struct super_block *s, struct fs_context *fc)1263{1264 return 1;1265}1266 1267static HWJS_SUSPENDS int vfs_get_super(struct fs_context *fc,1268 int (*test)(struct super_block *, struct fs_context *),1269 int (*fill_super)(struct super_block *sb,1270 struct fs_context *fc))1271{1272 struct super_block *sb;1273 int err;1274 1275 sb = sget_fc(fc, test, set_anon_super_fc);1276 if (IS_ERR(sb))1277 return PTR_ERR(sb);1278 1279 if (!sb->s_root) {1280 err = fill_super(sb, fc);1281 if (err)1282 goto error;1283 1284 sb->s_flags |= SB_ACTIVE;1285 }1286 1287 fc->root = dget(sb->s_root);1288 return 0;1289 1290error:1291 deactivate_locked_super(sb);1292 return err;1293}1294 1295int get_tree_nodev(struct fs_context *fc,1296 int (*fill_super)(struct super_block *sb,1297 struct fs_context *fc))1298{1299 return vfs_get_super(fc, NULL, fill_super);1300}1301EXPORT_SYMBOL(get_tree_nodev);1302 1303int get_tree_single(struct fs_context *fc,1304 int (*fill_super)(struct super_block *sb,1305 struct fs_context *fc))1306{1307 return vfs_get_super(fc, test_single_super, fill_super);1308}1309EXPORT_SYMBOL(get_tree_single);1310 1311int get_tree_keyed(struct fs_context *fc,1312 int (*fill_super)(struct super_block *sb,1313 struct fs_context *fc),1314 void *key)1315{1316 fc->s_fs_info = key;1317 return vfs_get_super(fc, test_keyed_super, fill_super);1318}1319EXPORT_SYMBOL(get_tree_keyed);1320 1321static int set_bdev_super(struct super_block *s, void *data)1322{1323 s->s_dev = *(dev_t *)data;1324 return 0;1325}1326 1327static int super_s_dev_set(struct super_block *s, struct fs_context *fc)1328{1329 return set_bdev_super(s, fc->sget_key);1330}1331 1332static int super_s_dev_test(struct super_block *s, struct fs_context *fc)1333{1334 return !(s->s_iflags & SB_I_RETIRED) &&1335 s->s_dev == *(dev_t *)fc->sget_key;1336}1337 1338/**1339 * sget_dev - Find or create a superblock by device number1340 * @fc: Filesystem context.1341 * @dev: device number1342 *1343 * Find or create a superblock using the provided device number that1344 * will be stored in fc->sget_key.1345 *1346 * If an extant superblock is matched, then that will be returned with1347 * an elevated reference count that the caller must transfer or discard.1348 *1349 * If no match is made, a new superblock will be allocated and basic1350 * initialisation will be performed (s_type, s_fs_info, s_id, s_dev will1351 * be set). The superblock will be published and it will be returned in1352 * a partially constructed state with SB_BORN and SB_ACTIVE as yet1353 * unset.1354 *1355 * Return: an existing or newly created superblock on success, an error1356 * pointer on failure.1357 */1358struct super_block *sget_dev(struct fs_context *fc, dev_t dev)1359{1360 fc->sget_key = &dev;1361 return sget_fc(fc, super_s_dev_test, super_s_dev_set);1362}1363EXPORT_SYMBOL(sget_dev);1364 1365#ifdef CONFIG_BLOCK1366/*1367 * Lock the superblock that is holder of the bdev. Returns the superblock1368 * pointer if we successfully locked the superblock and it is alive. Otherwise1369 * we return NULL and just unlock bdev->bd_holder_lock.1370 *1371 * The function must be called with bdev->bd_holder_lock and releases it.1372 */1373static struct super_block *bdev_super_lock(struct block_device *bdev, bool excl)1374 __releases(&bdev->bd_holder_lock)1375{1376 struct super_block *sb = bdev->bd_holder;1377 bool locked;1378 1379 lockdep_assert_held(&bdev->bd_holder_lock);1380 lockdep_assert_not_held(&sb->s_umount);1381 lockdep_assert_not_held(&bdev->bd_disk->open_mutex);1382 1383 /* Make sure sb doesn't go away from under us */1384 spin_lock(&sb_lock);1385 sb->s_count++;1386 spin_unlock(&sb_lock);1387 1388 mutex_unlock(&bdev->bd_holder_lock);1389 1390 locked = super_lock(sb, excl);1391 1392 /*1393 * If the superblock wasn't already SB_DYING then we hold1394 * s_umount and can safely drop our temporary reference.1395 */1396 put_super(sb);1397 1398 if (!locked)1399 return NULL;1400 1401 if (!sb->s_root || !(sb->s_flags & SB_ACTIVE)) {1402 super_unlock(sb, excl);1403 return NULL;1404 }1405 1406 return sb;1407}1408 1409static void fs_bdev_mark_dead(struct block_device *bdev, bool surprise)1410{1411 struct super_block *sb;1412 1413 sb = bdev_super_lock(bdev, false);1414 if (!sb)1415 return;1416 1417 if (!surprise)1418 sync_filesystem(sb);1419 shrink_dcache_sb(sb);1420 invalidate_inodes(sb);1421 if (sb->s_op->shutdown)1422 sb->s_op->shutdown(sb);1423 1424 super_unlock_shared(sb);1425}1426 1427static void fs_bdev_sync(struct block_device *bdev)1428{1429 struct super_block *sb;1430 1431 sb = bdev_super_lock(bdev, false);1432 if (!sb)1433 return;1434 1435 sync_filesystem(sb);1436 super_unlock_shared(sb);1437}1438 1439static struct super_block *get_bdev_super(struct block_device *bdev)1440{1441 bool active = false;1442 struct super_block *sb;1443 1444 sb = bdev_super_lock(bdev, true);1445 if (sb) {1446 active = atomic_inc_not_zero(&sb->s_active);1447 super_unlock_excl(sb);1448 }1449 if (!active)1450 return NULL;1451 return sb;1452}1453 1454/**1455 * fs_bdev_freeze - freeze owning filesystem of block device1456 * @bdev: block device1457 *1458 * Freeze the filesystem that owns this block device if it is still1459 * active.1460 *1461 * A filesystem that owns multiple block devices may be frozen from each1462 * block device and won't be unfrozen until all block devices are1463 * unfrozen. Each block device can only freeze the filesystem once as we1464 * nest freezes for block devices in the block layer.1465 *1466 * Return: If the freeze was successful zero is returned. If the freeze1467 * failed a negative error code is returned.1468 */1469static int fs_bdev_freeze(struct block_device *bdev)1470{1471 struct super_block *sb;1472 int error = 0;1473 1474 lockdep_assert_held(&bdev->bd_fsfreeze_mutex);1475 1476 sb = get_bdev_super(bdev);1477 if (!sb)1478 return -EINVAL;1479 1480 if (sb->s_op->freeze_super)1481 error = sb->s_op->freeze_super(sb,1482 FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);1483 else1484 error = freeze_super(sb,1485 FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);1486 if (!error)1487 error = sync_blockdev(bdev);1488 deactivate_super(sb);1489 return error;1490}1491 1492/**1493 * fs_bdev_thaw - thaw owning filesystem of block device1494 * @bdev: block device1495 *1496 * Thaw the filesystem that owns this block device.1497 *1498 * A filesystem that owns multiple block devices may be frozen from each1499 * block device and won't be unfrozen until all block devices are1500 * unfrozen. Each block device can only freeze the filesystem once as we1501 * nest freezes for block devices in the block layer.1502 *1503 * Return: If the thaw was successful zero is returned. If the thaw1504 * failed a negative error code is returned. If this function1505 * returns zero it doesn't mean that the filesystem is unfrozen1506 * as it may have been frozen multiple times (kernel may hold a1507 * freeze or might be frozen from other block devices).1508 */1509static int fs_bdev_thaw(struct block_device *bdev)1510{1511 struct super_block *sb;1512 int error;1513 1514 lockdep_assert_held(&bdev->bd_fsfreeze_mutex);1515 1516 /*1517 * The block device may have been frozen before it was claimed by a1518 * filesystem. Concurrently another process might try to mount that1519 * frozen block device and has temporarily claimed the block device for1520 * that purpose causing a concurrent fs_bdev_thaw() to end up here. The1521 * mounter is already about to abort mounting because they still saw an1522 * elevanted bdev->bd_fsfreeze_count so get_bdev_super() will return1523 * NULL in that case.1524 */1525 sb = get_bdev_super(bdev);1526 if (!sb)1527 return -EINVAL;1528 1529 if (sb->s_op->thaw_super)1530 error = sb->s_op->thaw_super(sb,1531 FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);1532 else1533 error = thaw_super(sb,1534 FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);1535 deactivate_super(sb);1536 return error;1537}1538 1539const struct blk_holder_ops fs_holder_ops = {1540 .mark_dead = fs_bdev_mark_dead,1541 .sync = fs_bdev_sync,1542 .freeze = fs_bdev_freeze,1543 .thaw = fs_bdev_thaw,1544};1545EXPORT_SYMBOL_GPL(fs_holder_ops);1546 1547int setup_bdev_super(struct super_block *sb, int sb_flags,1548 struct fs_context *fc)1549{1550 blk_mode_t mode = sb_open_mode(sb_flags);1551 struct file *bdev_file;1552 struct block_device *bdev;1553 1554 bdev_file = bdev_file_open_by_dev(sb->s_dev, mode, sb, &fs_holder_ops);1555 if (IS_ERR(bdev_file)) {1556 if (fc)1557 errorf(fc, "%s: Can't open blockdev", fc->source);1558 return PTR_ERR(bdev_file);1559 }1560 bdev = file_bdev(bdev_file);1561 1562 /*1563 * This really should be in blkdev_get_by_dev, but right now can't due1564 * to legacy issues that require us to allow opening a block device node1565 * writable from userspace even for a read-only block device.1566 */1567 if ((mode & BLK_OPEN_WRITE) && bdev_read_only(bdev)) {1568 bdev_fput(bdev_file);1569 return -EACCES;1570 }1571 1572 /*1573 * It is enough to check bdev was not frozen before we set1574 * s_bdev as freezing will wait until SB_BORN is set.1575 */1576 if (atomic_read(&bdev->bd_fsfreeze_count) > 0) {1577 if (fc)1578 warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);1579 bdev_fput(bdev_file);1580 return -EBUSY;1581 }1582 spin_lock(&sb_lock);1583 sb->s_bdev_file = bdev_file;1584 sb->s_bdev = bdev;1585 sb->s_bdi = bdi_get(bdev->bd_disk->bdi);1586 if (bdev_stable_writes(bdev))1587 sb->s_iflags |= SB_I_STABLE_WRITES;1588 spin_unlock(&sb_lock);1589 1590 snprintf(sb->s_id, sizeof(sb->s_id), "%pg", bdev);1591 shrinker_debugfs_rename(sb->s_shrink, "sb-%s:%s", sb->s_type->name,1592 sb->s_id);1593 sb_set_blocksize(sb, block_size(bdev));1594 return 0;1595}1596EXPORT_SYMBOL_GPL(setup_bdev_super);1597 1598/**1599 * get_tree_bdev_flags - Get a superblock based on a single block device1600 * @fc: The filesystem context holding the parameters1601 * @fill_super: Helper to initialise a new superblock1602 * @flags: GET_TREE_BDEV_* flags1603 */1604int get_tree_bdev_flags(struct fs_context *fc,1605 int (*fill_super)(struct super_block *sb,1606 struct fs_context *fc), unsigned int flags)1607{1608 struct super_block *s;1609 int error = 0;1610 dev_t dev;1611 1612 if (!fc->source)1613 return invalf(fc, "No source specified");1614 1615 error = lookup_bdev(fc->source, &dev);1616 if (error) {1617 if (!(flags & GET_TREE_BDEV_QUIET_LOOKUP))1618 errorf(fc, "%s: Can't lookup blockdev", fc->source);1619 return error;1620 }1621 fc->sb_flags |= SB_NOSEC;1622 s = sget_dev(fc, dev);1623 if (IS_ERR(s))1624 return PTR_ERR(s);1625 1626 if (s->s_root) {1627 /* Don't summarily change the RO/RW state. */1628 if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {1629 warnf(fc, "%pg: Can't mount, would change RO state", s->s_bdev);1630 deactivate_locked_super(s);1631 return -EBUSY;1632 }1633 } else {1634 error = setup_bdev_super(s, fc->sb_flags, fc);1635 if (!error)1636 error = fill_super(s, fc);1637 if (error) {1638 deactivate_locked_super(s);1639 return error;1640 }1641 s->s_flags |= SB_ACTIVE;1642 }1643 1644 BUG_ON(fc->root);1645 fc->root = dget(s->s_root);1646 return 0;1647}1648EXPORT_SYMBOL_GPL(get_tree_bdev_flags);1649 1650/**1651 * get_tree_bdev - Get a superblock based on a single block device1652 * @fc: The filesystem context holding the parameters1653 * @fill_super: Helper to initialise a new superblock1654 */1655int get_tree_bdev(struct fs_context *fc,1656 int (*fill_super)(struct super_block *,1657 struct fs_context *))1658{1659 return get_tree_bdev_flags(fc, fill_super, 0);1660}1661EXPORT_SYMBOL(get_tree_bdev);1662 1663static int test_bdev_super(struct super_block *s, void *data)1664{1665 return !(s->s_iflags & SB_I_RETIRED) && s->s_dev == *(dev_t *)data;1666}1667 1668struct dentry *mount_bdev(struct file_system_type *fs_type,1669 int flags, const char *dev_name, void *data,1670 int (*fill_super)(struct super_block *, void *, int))1671{1672 struct super_block *s;1673 int error;1674 dev_t dev;1675 1676 error = lookup_bdev(dev_name, &dev);1677 if (error)1678 return ERR_PTR(error);1679 1680 flags |= SB_NOSEC;1681 s = sget(fs_type, test_bdev_super, set_bdev_super, flags, &dev);1682 if (IS_ERR(s))1683 return ERR_CAST(s);1684 1685 if (s->s_root) {1686 if ((flags ^ s->s_flags) & SB_RDONLY) {1687 deactivate_locked_super(s);1688 return ERR_PTR(-EBUSY);1689 }1690 } else {1691 error = setup_bdev_super(s, flags, NULL);1692 if (!error)1693 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);1694 if (error) {1695 deactivate_locked_super(s);1696 return ERR_PTR(error);1697 }1698 1699 s->s_flags |= SB_ACTIVE;1700 }1701 1702 return dget(s->s_root);1703}1704EXPORT_SYMBOL(mount_bdev);1705 1706void kill_block_super(struct super_block *sb)1707{1708 struct block_device *bdev = sb->s_bdev;1709 1710 generic_shutdown_super(sb);1711 if (bdev) {1712 sync_blockdev(bdev);1713 bdev_fput(sb->s_bdev_file);1714 }1715}1716 1717EXPORT_SYMBOL(kill_block_super);1718#endif1719 1720struct dentry *mount_nodev(struct file_system_type *fs_type,1721 int flags, void *data,1722 int (*fill_super)(struct super_block *, void *, int))1723{1724 int error;1725 struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);1726 1727 if (IS_ERR(s))1728 return ERR_CAST(s);1729 1730 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);1731 if (error) {1732 deactivate_locked_super(s);1733 return ERR_PTR(error);1734 }1735 s->s_flags |= SB_ACTIVE;1736 return dget(s->s_root);1737}1738EXPORT_SYMBOL(mount_nodev);1739 1740int reconfigure_single(struct super_block *s,1741 int flags, void *data)1742{1743 struct fs_context *fc;1744 int ret;1745 1746 /* The caller really need to be passing fc down into mount_single(),1747 * then a chunk of this can be removed. [Bollocks -- AV]1748 * Better yet, reconfiguration shouldn't happen, but rather the second1749 * mount should be rejected if the parameters are not compatible.1750 */1751 fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);1752 if (IS_ERR(fc))1753 return PTR_ERR(fc);1754 1755 ret = parse_monolithic_mount_data(fc, data);1756 if (ret < 0)1757 goto out;1758 1759 ret = reconfigure_super(fc);1760out:1761 put_fs_context(fc);1762 return ret;1763}1764 1765static int compare_single(struct super_block *s, void *p)1766{1767 return 1;1768}1769 1770struct dentry *mount_single(struct file_system_type *fs_type,1771 int flags, void *data,1772 int (*fill_super)(struct super_block *, void *, int))1773{1774 struct super_block *s;1775 int error;1776 1777 s = sget(fs_type, compare_single, set_anon_super, flags, NULL);1778 if (IS_ERR(s))1779 return ERR_CAST(s);1780 if (!s->s_root) {1781 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);1782 if (!error)1783 s->s_flags |= SB_ACTIVE;1784 } else {1785 error = reconfigure_single(s, flags, data);1786 }1787 if (unlikely(error)) {1788 deactivate_locked_super(s);1789 return ERR_PTR(error);1790 }1791 return dget(s->s_root);1792}1793EXPORT_SYMBOL(mount_single);1794 1795/**1796 * vfs_get_tree - Get the mountable root1797 * @fc: The superblock configuration context.1798 *1799 * The filesystem is invoked to get or create a superblock which can then later1800 * be used for mounting. The filesystem places a pointer to the root to be1801 * used for mounting in @fc->root.1802 */1803int vfs_get_tree(struct fs_context *fc)1804{1805 struct super_block *sb;1806 int error;1807 1808 if (fc->root)1809 return -EBUSY;1810 1811 /* Get the mountable root in fc->root, with a ref on the root and a ref1812 * on the superblock.1813 */1814 error = fc->ops->get_tree(fc);1815 if (error < 0)1816 return error;1817 1818 if (!fc->root) {1819 pr_err("Filesystem %s get_tree() didn't set fc->root, returned %i\n",1820 fc->fs_type->name, error);1821 /* We don't know what the locking state of the superblock is -1822 * if there is a superblock.1823 */1824 BUG();1825 }1826 1827 sb = fc->root->d_sb;1828 WARN_ON(!sb->s_bdi);1829 1830 /*1831 * super_wake() contains a memory barrier which also care of1832 * ordering for super_cache_count(). We place it before setting1833 * SB_BORN as the data dependency between the two functions is1834 * the superblock structure contents that we just set up, not1835 * the SB_BORN flag.1836 */1837 super_wake(sb, SB_BORN);1838 1839 error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);1840 if (unlikely(error)) {1841 fc_drop_locked(fc);1842 return error;1843 }1844 1845 /*1846 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE1847 * but s_maxbytes was an unsigned long long for many releases. Throw1848 * this warning for a little while to try and catch filesystems that1849 * violate this rule.1850 */1851 WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "1852 "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);1853 1854 return 0;1855}1856EXPORT_SYMBOL(vfs_get_tree);1857 1858/*1859 * Setup private BDI for given superblock. It gets automatically cleaned up1860 * in generic_shutdown_super().1861 */1862int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)1863{1864 struct backing_dev_info *bdi;1865 int err;1866 va_list args;1867 1868 bdi = bdi_alloc(NUMA_NO_NODE);1869 if (!bdi)1870 return -ENOMEM;1871 1872 va_start(args, fmt);1873 err = bdi_register_va(bdi, fmt, args);1874 va_end(args);1875 if (err) {1876 bdi_put(bdi);1877 return err;1878 }1879 WARN_ON(sb->s_bdi != &noop_backing_dev_info);1880 sb->s_bdi = bdi;1881 sb->s_iflags |= SB_I_PERSB_BDI;1882 1883 return 0;1884}1885EXPORT_SYMBOL(super_setup_bdi_name);1886 1887/*1888 * Setup private BDI for given superblock. I gets automatically cleaned up1889 * in generic_shutdown_super().1890 */1891int super_setup_bdi(struct super_block *sb)1892{1893 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);1894 1895 return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,1896 atomic_long_inc_return(&bdi_seq));1897}1898EXPORT_SYMBOL(super_setup_bdi);1899 1900/**1901 * sb_wait_write - wait until all writers to given file system finish1902 * @sb: the super for which we wait1903 * @level: type of writers we wait for (normal vs page fault)1904 *1905 * This function waits until there are no writers of given type to given file1906 * system.1907 */1908static HWJS_SUSPENDS void sb_wait_write(struct super_block *sb, int level)1909{1910 percpu_down_write(sb->s_writers.rw_sem + level-1);1911}1912 1913/*1914 * We are going to return to userspace and forget about these locks, the1915 * ownership goes to the caller of thaw_super() which does unlock().1916 */1917static void lockdep_sb_freeze_release(struct super_block *sb)1918{1919 int level;1920 1921 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)1922 percpu_rwsem_release(sb->s_writers.rw_sem + level, _THIS_IP_);1923}1924 1925/*1926 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).1927 */1928static void lockdep_sb_freeze_acquire(struct super_block *sb)1929{1930 int level;1931 1932 for (level = 0; level < SB_FREEZE_LEVELS; ++level)1933 percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);1934}1935 1936static void sb_freeze_unlock(struct super_block *sb, int level)1937{1938 for (level--; level >= 0; level--)1939 percpu_up_write(sb->s_writers.rw_sem + level);1940}1941 1942static HWJS_SUSPENDS int wait_for_partially_frozen(struct super_block *sb)1943{1944 int ret = 0;1945 1946 do {1947 unsigned short old = sb->s_writers.frozen;1948 1949 up_write(&sb->s_umount);1950 ret = wait_var_event_killable(&sb->s_writers.frozen,1951 sb->s_writers.frozen != old);1952 down_write(&sb->s_umount);1953 } while (ret == 0 &&1954 sb->s_writers.frozen != SB_UNFROZEN &&1955 sb->s_writers.frozen != SB_FREEZE_COMPLETE);1956 1957 return ret;1958}1959 1960#define FREEZE_HOLDERS (FREEZE_HOLDER_KERNEL | FREEZE_HOLDER_USERSPACE)1961#define FREEZE_FLAGS (FREEZE_HOLDERS | FREEZE_MAY_NEST)1962 1963static inline int freeze_inc(struct super_block *sb, enum freeze_holder who)1964{1965 WARN_ON_ONCE((who & ~FREEZE_FLAGS));1966 WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);1967 1968 if (who & FREEZE_HOLDER_KERNEL)1969 ++sb->s_writers.freeze_kcount;1970 if (who & FREEZE_HOLDER_USERSPACE)1971 ++sb->s_writers.freeze_ucount;1972 return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount;1973}1974 1975static inline int freeze_dec(struct super_block *sb, enum freeze_holder who)1976{1977 WARN_ON_ONCE((who & ~FREEZE_FLAGS));1978 WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);1979 1980 if ((who & FREEZE_HOLDER_KERNEL) && sb->s_writers.freeze_kcount)1981 --sb->s_writers.freeze_kcount;1982 if ((who & FREEZE_HOLDER_USERSPACE) && sb->s_writers.freeze_ucount)1983 --sb->s_writers.freeze_ucount;1984 return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount;1985}1986 1987static inline bool may_freeze(struct super_block *sb, enum freeze_holder who)1988{1989 WARN_ON_ONCE((who & ~FREEZE_FLAGS));1990 WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);1991 1992 if (who & FREEZE_HOLDER_KERNEL)1993 return (who & FREEZE_MAY_NEST) ||1994 sb->s_writers.freeze_kcount == 0;1995 if (who & FREEZE_HOLDER_USERSPACE)1996 return (who & FREEZE_MAY_NEST) ||1997 sb->s_writers.freeze_ucount == 0;1998 return false;1999}2000 2001/**2002 * freeze_super - lock the filesystem and force it into a consistent state2003 * @sb: the super to lock2004 * @who: context that wants to freeze2005 *2006 * Syncs the super to make sure the filesystem is consistent and calls the fs's2007 * freeze_fs. Subsequent calls to this without first thawing the fs may return2008 * -EBUSY.2009 *2010 * @who should be:2011 * * %FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs;2012 * * %FREEZE_HOLDER_KERNEL if the kernel wants to freeze the fs.2013 * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed.2014 *2015 * The @who argument distinguishes between the kernel and userspace trying to2016 * freeze the filesystem. Although there cannot be multiple kernel freezes or2017 * multiple userspace freezes in effect at any given time, the kernel and2018 * userspace can both hold a filesystem frozen. The filesystem remains frozen2019 * until there are no kernel or userspace freezes in effect.2020 *2021 * A filesystem may hold multiple devices and thus a filesystems may be2022 * frozen through the block layer via multiple block devices. In this2023 * case the request is marked as being allowed to nest by passing2024 * FREEZE_MAY_NEST. The filesystem remains frozen until all block2025 * devices are unfrozen. If multiple freezes are attempted without2026 * FREEZE_MAY_NEST -EBUSY will be returned.2027 *2028 * During this function, sb->s_writers.frozen goes through these values:2029 *2030 * SB_UNFROZEN: File system is normal, all writes progress as usual.2031 *2032 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New2033 * writes should be blocked, though page faults are still allowed. We wait for2034 * all writes to complete and then proceed to the next stage.2035 *2036 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked2037 * but internal fs threads can still modify the filesystem (although they2038 * should not dirty new pages or inodes), writeback can run etc. After waiting2039 * for all running page faults we sync the filesystem which will clean all2040 * dirty pages and inodes (no new dirty pages or inodes can be created when2041 * sync is running).2042 *2043 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs2044 * modification are blocked (e.g. XFS preallocation truncation on inode2045 * reclaim). This is usually implemented by blocking new transactions for2046 * filesystems that have them and need this additional guard. After all2047 * internal writers are finished we call ->freeze_fs() to finish filesystem2048 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is2049 * mostly auxiliary for filesystems to verify they do not modify frozen fs.2050 *2051 * sb->s_writers.frozen is protected by sb->s_umount.2052 *2053 * Return: If the freeze was successful zero is returned. If the freeze2054 * failed a negative error code is returned.2055 */2056int freeze_super(struct super_block *sb, enum freeze_holder who)2057{2058 int ret;2059 2060 if (!super_lock_excl(sb)) {2061 WARN_ON_ONCE("Dying superblock while freezing!");2062 return -EINVAL;2063 }2064 atomic_inc(&sb->s_active);2065 2066retry:2067 if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) {2068 if (may_freeze(sb, who))2069 ret = !!WARN_ON_ONCE(freeze_inc(sb, who) == 1);2070 else2071 ret = -EBUSY;2072 /* All freezers share a single active reference. */2073 deactivate_locked_super(sb);2074 return ret;2075 }2076 2077 if (sb->s_writers.frozen != SB_UNFROZEN) {2078 ret = wait_for_partially_frozen(sb);2079 if (ret) {2080 deactivate_locked_super(sb);2081 return ret;2082 }2083 2084 goto retry;2085 }2086 2087 if (sb_rdonly(sb)) {2088 /* Nothing to do really... */2089 WARN_ON_ONCE(freeze_inc(sb, who) > 1);2090 sb->s_writers.frozen = SB_FREEZE_COMPLETE;2091 wake_up_var(&sb->s_writers.frozen);2092 super_unlock_excl(sb);2093 return 0;2094 }2095 2096 sb->s_writers.frozen = SB_FREEZE_WRITE;2097 /* Release s_umount to preserve sb_start_write -> s_umount ordering */2098 super_unlock_excl(sb);2099 sb_wait_write(sb, SB_FREEZE_WRITE);2100 __super_lock_excl(sb);2101 2102 /* Now we go and block page faults... */2103 sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;2104 sb_wait_write(sb, SB_FREEZE_PAGEFAULT);2105 2106 /* All writers are done so after syncing there won't be dirty data */2107 ret = sync_filesystem(sb);2108 if (ret) {2109 sb->s_writers.frozen = SB_UNFROZEN;2110 sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT);2111 wake_up_var(&sb->s_writers.frozen);2112 deactivate_locked_super(sb);2113 return ret;2114 }2115 2116 /* Now wait for internal filesystem counter */2117 sb->s_writers.frozen = SB_FREEZE_FS;2118 sb_wait_write(sb, SB_FREEZE_FS);2119 2120 if (sb->s_op->freeze_fs) {2121 ret = sb->s_op->freeze_fs(sb);2122 if (ret) {2123 printk(KERN_ERR2124 "VFS:Filesystem freeze failed\n");2125 sb->s_writers.frozen = SB_UNFROZEN;2126 sb_freeze_unlock(sb, SB_FREEZE_FS);2127 wake_up_var(&sb->s_writers.frozen);2128 deactivate_locked_super(sb);2129 return ret;2130 }2131 }2132 /*2133 * For debugging purposes so that fs can warn if it sees write activity2134 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().2135 */2136 WARN_ON_ONCE(freeze_inc(sb, who) > 1);2137 sb->s_writers.frozen = SB_FREEZE_COMPLETE;2138 wake_up_var(&sb->s_writers.frozen);2139 lockdep_sb_freeze_release(sb);2140 super_unlock_excl(sb);2141 return 0;2142}2143EXPORT_SYMBOL(freeze_super);2144 2145/*2146 * Undoes the effect of a freeze_super_locked call. If the filesystem is2147 * frozen both by userspace and the kernel, a thaw call from either source2148 * removes that state without releasing the other state or unlocking the2149 * filesystem.2150 */2151static HWJS_SUSPENDS int thaw_super_locked(struct super_block *sb, enum freeze_holder who)2152{2153 int error = -EINVAL;2154 2155 if (sb->s_writers.frozen != SB_FREEZE_COMPLETE)2156 goto out_unlock;2157 2158 /*2159 * All freezers share a single active reference.2160 * So just unlock in case there are any left.2161 */2162 if (freeze_dec(sb, who))2163 goto out_unlock;2164 2165 if (sb_rdonly(sb)) {2166 sb->s_writers.frozen = SB_UNFROZEN;2167 wake_up_var(&sb->s_writers.frozen);2168 goto out_deactivate;2169 }2170 2171 lockdep_sb_freeze_acquire(sb);2172 2173 if (sb->s_op->unfreeze_fs) {2174 error = sb->s_op->unfreeze_fs(sb);2175 if (error) {2176 pr_err("VFS: Filesystem thaw failed\n");2177 freeze_inc(sb, who);2178 lockdep_sb_freeze_release(sb);2179 goto out_unlock;2180 }2181 }2182 2183 sb->s_writers.frozen = SB_UNFROZEN;2184 wake_up_var(&sb->s_writers.frozen);2185 sb_freeze_unlock(sb, SB_FREEZE_FS);2186out_deactivate:2187 deactivate_locked_super(sb);2188 return 0;2189 2190out_unlock:2191 super_unlock_excl(sb);2192 return error;2193}2194 2195/**2196 * thaw_super -- unlock filesystem2197 * @sb: the super to thaw2198 * @who: context that wants to freeze2199 *2200 * Unlocks the filesystem and marks it writeable again after freeze_super()2201 * if there are no remaining freezes on the filesystem.2202 *2203 * @who should be:2204 * * %FREEZE_HOLDER_USERSPACE if userspace wants to thaw the fs;2205 * * %FREEZE_HOLDER_KERNEL if the kernel wants to thaw the fs.2206 * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed2207 *2208 * A filesystem may hold multiple devices and thus a filesystems may2209 * have been frozen through the block layer via multiple block devices.2210 * The filesystem remains frozen until all block devices are unfrozen.2211 */2212int thaw_super(struct super_block *sb, enum freeze_holder who)2213{2214 if (!super_lock_excl(sb)) {2215 WARN_ON_ONCE("Dying superblock while thawing!");2216 return -EINVAL;2217 }2218 return thaw_super_locked(sb, who);2219}2220EXPORT_SYMBOL(thaw_super);2221 2222/*2223 * Create workqueue for deferred direct IO completions. We allocate the2224 * workqueue when it's first needed. This avoids creating workqueue for2225 * filesystems that don't need it and also allows us to create the workqueue2226 * late enough so the we can include s_id in the name of the workqueue.2227 */2228int sb_init_dio_done_wq(struct super_block *sb)2229{2230 struct workqueue_struct *old;2231 struct workqueue_struct *wq = alloc_workqueue("dio/%s",2232 WQ_MEM_RECLAIM, 0,2233 sb->s_id);2234 if (!wq)2235 return -ENOMEM;2236 /*2237 * This has to be atomic as more DIOs can race to create the workqueue2238 */2239 old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);2240 /* Someone created workqueue before us? Free ours... */2241 if (old)2242 destroy_workqueue(wq);2243 return 0;2244}2245EXPORT_SYMBOL_GPL(sb_init_dio_done_wq);2246