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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
43static int thaw_super_locked(struct super_block *sb);
44
45static LIST_HEAD(super_blocks);
46static DEFINE_SPINLOCK(sb_lock);
47
48static 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 */
61static 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
118static 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
157static 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
168static 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 */
176static 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 */
200static 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
278fail:
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 */
288static 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 */
310static 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 */
329void 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
352EXPORT_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 */
362void 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
370EXPORT_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 */
385static 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 */
416bool 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 */
442void 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 fsnotify_sb_delete(sb);
452 cgroup_writeback_umount();
453
454 evict_inodes(sb);
455
456 if (sb->s_dio_done_wq) {
457 destroy_workqueue(sb->s_dio_done_wq);
458 sb->s_dio_done_wq = NULL;
459 }
460
461 if (sop->put_super)
462 sop->put_super(sb);
463
464 if (!list_empty(&sb->s_inodes)) {
465 printk("VFS: Busy inodes after unmount of %s. "
466 "Self-destruct in 5 seconds. Have a nice day...\n",
467 sb->s_id);
468 }
469 }
470 spin_lock(&sb_lock);
471 /* should be initialized for __put_super_and_need_restart() */
472 hlist_del_init(&sb->s_instances);
473 spin_unlock(&sb_lock);
474 up_write(&sb->s_umount);
475 if (sb->s_bdi != &noop_backing_dev_info) {
476 bdi_put(sb->s_bdi);
477 sb->s_bdi = &noop_backing_dev_info;
478 }
479}
480
481EXPORT_SYMBOL(generic_shutdown_super);
482
483bool mount_capable(struct fs_context *fc)
484{
485 if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
486 return capable(CAP_SYS_ADMIN);
487 else
488 return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
489}
490
491/**
492 * sget_fc - Find or create a superblock
493 * @fc: Filesystem context.
494 * @test: Comparison callback
495 * @set: Setup callback
496 *
497 * Find or create a superblock using the parameters stored in the filesystem
498 * context and the two callback functions.
499 *
500 * If an extant superblock is matched, then that will be returned with an
501 * elevated reference count that the caller must transfer or discard.
502 *
503 * If no match is made, a new superblock will be allocated and basic
504 * initialisation will be performed (s_type, s_fs_info and s_id will be set and
505 * the set() callback will be invoked), the superblock will be published and it
506 * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
507 * as yet unset.
508 */
509struct super_block *sget_fc(struct fs_context *fc,
510 int (*test)(struct super_block *, struct fs_context *),
511 int (*set)(struct super_block *, struct fs_context *))
512{
513 struct super_block *s = NULL;
514 struct super_block *old;
515 struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
516 int err;
517
518retry:
519 spin_lock(&sb_lock);
520 if (test) {
521 hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
522 if (test(old, fc))
523 goto share_extant_sb;
524 }
525 }
526 if (!s) {
527 spin_unlock(&sb_lock);
528 s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
529 if (!s)
530 return ERR_PTR(-ENOMEM);
531 goto retry;
532 }
533
534 s->s_fs_info = fc->s_fs_info;
535 err = set(s, fc);
536 if (err) {
537 s->s_fs_info = NULL;
538 spin_unlock(&sb_lock);
539 destroy_unused_super(s);
540 return ERR_PTR(err);
541 }
542 fc->s_fs_info = NULL;
543 s->s_type = fc->fs_type;
544 s->s_iflags |= fc->s_iflags;
545 strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
546 list_add_tail(&s->s_list, &super_blocks);
547 hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
548 spin_unlock(&sb_lock);
549 get_filesystem(s->s_type);
550 register_shrinker_prepared(&s->s_shrink);
551 return s;
552
553share_extant_sb:
554 if (user_ns != old->s_user_ns) {
555 spin_unlock(&sb_lock);
556 destroy_unused_super(s);
557 return ERR_PTR(-EBUSY);
558 }
559 if (!grab_super(old))
560 goto retry;
561 destroy_unused_super(s);
562 return old;
563}
564EXPORT_SYMBOL(sget_fc);
565
566/**
567 * sget - find or create a superblock
568 * @type: filesystem type superblock should belong to
569 * @test: comparison callback
570 * @set: setup callback
571 * @flags: mount flags
572 * @data: argument to each of them
573 */
574struct super_block *sget(struct file_system_type *type,
575 int (*test)(struct super_block *,void *),
576 int (*set)(struct super_block *,void *),
577 int flags,
578 void *data)
579{
580 struct user_namespace *user_ns = current_user_ns();
581 struct super_block *s = NULL;
582 struct super_block *old;
583 int err;
584
585 /* We don't yet pass the user namespace of the parent
586 * mount through to here so always use &init_user_ns
587 * until that changes.
588 */
589 if (flags & SB_SUBMOUNT)
590 user_ns = &init_user_ns;
591
592retry:
593 spin_lock(&sb_lock);
594 if (test) {
595 hlist_for_each_entry(old, &type->fs_supers, s_instances) {
596 if (!test(old, data))
597 continue;
598 if (user_ns != old->s_user_ns) {
599 spin_unlock(&sb_lock);
600 destroy_unused_super(s);
601 return ERR_PTR(-EBUSY);
602 }
603 if (!grab_super(old))
604 goto retry;
605 destroy_unused_super(s);
606 return old;
607 }
608 }
609 if (!s) {
610 spin_unlock(&sb_lock);
611 s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
612 if (!s)
613 return ERR_PTR(-ENOMEM);
614 goto retry;
615 }
616
617 err = set(s, data);
618 if (err) {
619 spin_unlock(&sb_lock);
620 destroy_unused_super(s);
621 return ERR_PTR(err);
622 }
623 s->s_type = type;
624 strlcpy(s->s_id, type->name, sizeof(s->s_id));
625 list_add_tail(&s->s_list, &super_blocks);
626 hlist_add_head(&s->s_instances, &type->fs_supers);
627 spin_unlock(&sb_lock);
628 get_filesystem(type);
629 register_shrinker_prepared(&s->s_shrink);
630 return s;
631}
632EXPORT_SYMBOL(sget);
633
634void drop_super(struct super_block *sb)
635{
636 up_read(&sb->s_umount);
637 put_super(sb);
638}
639
640EXPORT_SYMBOL(drop_super);
641
642void drop_super_exclusive(struct super_block *sb)
643{
644 up_write(&sb->s_umount);
645 put_super(sb);
646}
647EXPORT_SYMBOL(drop_super_exclusive);
648
649static void __iterate_supers(void (*f)(struct super_block *))
650{
651 struct super_block *sb, *p = NULL;
652
653 spin_lock(&sb_lock);
654 list_for_each_entry(sb, &super_blocks, s_list) {
655 if (hlist_unhashed(&sb->s_instances))
656 continue;
657 sb->s_count++;
658 spin_unlock(&sb_lock);
659
660 f(sb);
661
662 spin_lock(&sb_lock);
663 if (p)
664 __put_super(p);
665 p = sb;
666 }
667 if (p)
668 __put_super(p);
669 spin_unlock(&sb_lock);
670}
671/**
672 * iterate_supers - call function for all active superblocks
673 * @f: function to call
674 * @arg: argument to pass to it
675 *
676 * Scans the superblock list and calls given function, passing it
677 * locked superblock and given argument.
678 */
679void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
680{
681 struct super_block *sb, *p = NULL;
682
683 spin_lock(&sb_lock);
684 list_for_each_entry(sb, &super_blocks, s_list) {
685 if (hlist_unhashed(&sb->s_instances))
686 continue;
687 sb->s_count++;
688 spin_unlock(&sb_lock);
689
690 down_read(&sb->s_umount);
691 if (sb->s_root && (sb->s_flags & SB_BORN))
692 f(sb, arg);
693 up_read(&sb->s_umount);
694
695 spin_lock(&sb_lock);
696 if (p)
697 __put_super(p);
698 p = sb;
699 }
700 if (p)
701 __put_super(p);
702 spin_unlock(&sb_lock);
703}
704
705/**
706 * iterate_supers_type - call function for superblocks of given type
707 * @type: fs type
708 * @f: function to call
709 * @arg: argument to pass to it
710 *
711 * Scans the superblock list and calls given function, passing it
712 * locked superblock and given argument.
713 */
714void iterate_supers_type(struct file_system_type *type,
715 void (*f)(struct super_block *, void *), void *arg)
716{
717 struct super_block *sb, *p = NULL;
718
719 spin_lock(&sb_lock);
720 hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
721 sb->s_count++;
722 spin_unlock(&sb_lock);
723
724 down_read(&sb->s_umount);
725 if (sb->s_root && (sb->s_flags & SB_BORN))
726 f(sb, arg);
727 up_read(&sb->s_umount);
728
729 spin_lock(&sb_lock);
730 if (p)
731 __put_super(p);
732 p = sb;
733 }
734 if (p)
735 __put_super(p);
736 spin_unlock(&sb_lock);
737}
738
739EXPORT_SYMBOL(iterate_supers_type);
740
741static struct super_block *__get_super(struct block_device *bdev, bool excl)
742{
743 struct super_block *sb;
744
745 if (!bdev)
746 return NULL;
747
748 spin_lock(&sb_lock);
749rescan:
750 list_for_each_entry(sb, &super_blocks, s_list) {
751 if (hlist_unhashed(&sb->s_instances))
752 continue;
753 if (sb->s_bdev == bdev) {
754 sb->s_count++;
755 spin_unlock(&sb_lock);
756 if (!excl)
757 down_read(&sb->s_umount);
758 else
759 down_write(&sb->s_umount);
760 /* still alive? */
761 if (sb->s_root && (sb->s_flags & SB_BORN))
762 return sb;
763 if (!excl)
764 up_read(&sb->s_umount);
765 else
766 up_write(&sb->s_umount);
767 /* nope, got unmounted */
768 spin_lock(&sb_lock);
769 __put_super(sb);
770 goto rescan;
771 }
772 }
773 spin_unlock(&sb_lock);
774 return NULL;
775}
776
777/**
778 * get_super - get the superblock of a device
779 * @bdev: device to get the superblock for
780 *
781 * Scans the superblock list and finds the superblock of the file system
782 * mounted on the device given. %NULL is returned if no match is found.
783 */
784struct super_block *get_super(struct block_device *bdev)
785{
786 return __get_super(bdev, false);
787}
788EXPORT_SYMBOL(get_super);
789
790static struct super_block *__get_super_thawed(struct block_device *bdev,
791 bool excl)
792{
793 while (1) {
794 struct super_block *s = __get_super(bdev, excl);
795 if (!s || s->s_writers.frozen == SB_UNFROZEN)
796 return s;
797 if (!excl)
798 up_read(&s->s_umount);
799 else
800 up_write(&s->s_umount);
801 wait_event(s->s_writers.wait_unfrozen,
802 s->s_writers.frozen == SB_UNFROZEN);
803 put_super(s);
804 }
805}
806
807/**
808 * get_super_thawed - get thawed superblock of a device
809 * @bdev: device to get the superblock for
810 *
811 * Scans the superblock list and finds the superblock of the file system
812 * mounted on the device. The superblock is returned once it is thawed
813 * (or immediately if it was not frozen). %NULL is returned if no match
814 * is found.
815 */
816struct super_block *get_super_thawed(struct block_device *bdev)
817{
818 return __get_super_thawed(bdev, false);
819}
820EXPORT_SYMBOL(get_super_thawed);
821
822/**
823 * get_super_exclusive_thawed - get thawed superblock of a device
824 * @bdev: device to get the superblock for
825 *
826 * Scans the superblock list and finds the superblock of the file system
827 * mounted on the device. The superblock is returned once it is thawed
828 * (or immediately if it was not frozen) and s_umount semaphore is held
829 * in exclusive mode. %NULL is returned if no match is found.
830 */
831struct super_block *get_super_exclusive_thawed(struct block_device *bdev)
832{
833 return __get_super_thawed(bdev, true);
834}
835EXPORT_SYMBOL(get_super_exclusive_thawed);
836
837/**
838 * get_active_super - get an active reference to the superblock of a device
839 * @bdev: device to get the superblock for
840 *
841 * Scans the superblock list and finds the superblock of the file system
842 * mounted on the device given. Returns the superblock with an active
843 * reference or %NULL if none was found.
844 */
845struct super_block *get_active_super(struct block_device *bdev)
846{
847 struct super_block *sb;
848
849 if (!bdev)
850 return NULL;
851
852restart:
853 spin_lock(&sb_lock);
854 list_for_each_entry(sb, &super_blocks, s_list) {
855 if (hlist_unhashed(&sb->s_instances))
856 continue;
857 if (sb->s_bdev == bdev) {
858 if (!grab_super(sb))
859 goto restart;
860 up_write(&sb->s_umount);
861 return sb;
862 }
863 }
864 spin_unlock(&sb_lock);
865 return NULL;
866}
867
868struct super_block *user_get_super(dev_t dev)
869{
870 struct super_block *sb;
871
872 spin_lock(&sb_lock);
873rescan:
874 list_for_each_entry(sb, &super_blocks, s_list) {
875 if (hlist_unhashed(&sb->s_instances))
876 continue;
877 if (sb->s_dev == dev) {
878 sb->s_count++;
879 spin_unlock(&sb_lock);
880 down_read(&sb->s_umount);
881 /* still alive? */
882 if (sb->s_root && (sb->s_flags & SB_BORN))
883 return sb;
884 up_read(&sb->s_umount);
885 /* nope, got unmounted */
886 spin_lock(&sb_lock);
887 __put_super(sb);
888 goto rescan;
889 }
890 }
891 spin_unlock(&sb_lock);
892 return NULL;
893}
894
895/**
896 * reconfigure_super - asks filesystem to change superblock parameters
897 * @fc: The superblock and configuration
898 *
899 * Alters the configuration parameters of a live superblock.
900 */
901int reconfigure_super(struct fs_context *fc)
902{
903 struct super_block *sb = fc->root->d_sb;
904 int retval;
905 bool remount_ro = false;
906 bool force = fc->sb_flags & SB_FORCE;
907
908 if (fc->sb_flags_mask & ~MS_RMT_MASK)
909 return -EINVAL;
910 if (sb->s_writers.frozen != SB_UNFROZEN)
911 return -EBUSY;
912
913 retval = security_sb_remount(sb, fc->security);
914 if (retval)
915 return retval;
916
917 if (fc->sb_flags_mask & SB_RDONLY) {
918#ifdef CONFIG_BLOCK
919 if (!(fc->sb_flags & SB_RDONLY) && bdev_read_only(sb->s_bdev))
920 return -EACCES;
921#endif
922
923 remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
924 }
925
926 if (remount_ro) {
927 if (!hlist_empty(&sb->s_pins)) {
928 up_write(&sb->s_umount);
929 group_pin_kill(&sb->s_pins);
930 down_write(&sb->s_umount);
931 if (!sb->s_root)
932 return 0;
933 if (sb->s_writers.frozen != SB_UNFROZEN)
934 return -EBUSY;
935 remount_ro = !sb_rdonly(sb);
936 }
937 }
938 shrink_dcache_sb(sb);
939
940 /* If we are reconfiguring to RDONLY and current sb is read/write,
941 * make sure there are no files open for writing.
942 */
943 if (remount_ro) {
944 if (force) {
945 sb->s_readonly_remount = 1;
946 smp_wmb();
947 } else {
948 retval = sb_prepare_remount_readonly(sb);
949 if (retval)
950 return retval;
951 }
952 }
953
954 if (fc->ops->reconfigure) {
955 retval = fc->ops->reconfigure(fc);
956 if (retval) {
957 if (!force)
958 goto cancel_readonly;
959 /* If forced remount, go ahead despite any errors */
960 WARN(1, "forced remount of a %s fs returned %i\n",
961 sb->s_type->name, retval);
962 }
963 }
964
965 WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
966 (fc->sb_flags & fc->sb_flags_mask)));
967 /* Needs to be ordered wrt mnt_is_readonly() */
968 smp_wmb();
969 sb->s_readonly_remount = 0;
970
971 /*
972 * Some filesystems modify their metadata via some other path than the
973 * bdev buffer cache (eg. use a private mapping, or directories in
974 * pagecache, etc). Also file data modifications go via their own
975 * mappings. So If we try to mount readonly then copy the filesystem
976 * from bdev, we could get stale data, so invalidate it to give a best
977 * effort at coherency.
978 */
979 if (remount_ro && sb->s_bdev)
980 invalidate_bdev(sb->s_bdev);
981 return 0;
982
983cancel_readonly:
984 sb->s_readonly_remount = 0;
985 return retval;
986}
987
988static void do_emergency_remount_callback(struct super_block *sb)
989{
990 down_write(&sb->s_umount);
991 if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
992 !sb_rdonly(sb)) {
993 struct fs_context *fc;
994
995 fc = fs_context_for_reconfigure(sb->s_root,
996 SB_RDONLY | SB_FORCE, SB_RDONLY);
997 if (!IS_ERR(fc)) {
998 if (parse_monolithic_mount_data(fc, NULL) == 0)
999 (void)reconfigure_super(fc);
1000 put_fs_context(fc);
1001 }
1002 }
1003 up_write(&sb->s_umount);
1004}
1005
1006static void do_emergency_remount(struct work_struct *work)
1007{
1008 __iterate_supers(do_emergency_remount_callback);
1009 kfree(work);
1010 printk("Emergency Remount complete\n");
1011}
1012
1013void emergency_remount(void)
1014{
1015 struct work_struct *work;
1016
1017 work = kmalloc(sizeof(*work), GFP_ATOMIC);
1018 if (work) {
1019 INIT_WORK(work, do_emergency_remount);
1020 schedule_work(work);
1021 }
1022}
1023
1024static void do_thaw_all_callback(struct super_block *sb)
1025{
1026 down_write(&sb->s_umount);
1027 if (sb->s_root && sb->s_flags & SB_BORN) {
1028 emergency_thaw_bdev(sb);
1029 thaw_super_locked(sb);
1030 } else {
1031 up_write(&sb->s_umount);
1032 }
1033}
1034
1035static void do_thaw_all(struct work_struct *work)
1036{
1037 __iterate_supers(do_thaw_all_callback);
1038 kfree(work);
1039 printk(KERN_WARNING "Emergency Thaw complete\n");
1040}
1041
1042/**
1043 * emergency_thaw_all -- forcibly thaw every frozen filesystem
1044 *
1045 * Used for emergency unfreeze of all filesystems via SysRq
1046 */
1047void emergency_thaw_all(void)
1048{
1049 struct work_struct *work;
1050
1051 work = kmalloc(sizeof(*work), GFP_ATOMIC);
1052 if (work) {
1053 INIT_WORK(work, do_thaw_all);
1054 schedule_work(work);
1055 }
1056}
1057
1058static DEFINE_IDA(unnamed_dev_ida);
1059
1060/**
1061 * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1062 * @p: Pointer to a dev_t.
1063 *
1064 * Filesystems which don't use real block devices can call this function
1065 * to allocate a virtual block device.
1066 *
1067 * Context: Any context. Frequently called while holding sb_lock.
1068 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1069 * or -ENOMEM if memory allocation failed.
1070 */
1071int get_anon_bdev(dev_t *p)
1072{
1073 int dev;
1074
1075 /*
1076 * Many userspace utilities consider an FSID of 0 invalid.
1077 * Always return at least 1 from get_anon_bdev.
1078 */
1079 dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
1080 GFP_ATOMIC);
1081 if (dev == -ENOSPC)
1082 dev = -EMFILE;
1083 if (dev < 0)
1084 return dev;
1085
1086 *p = MKDEV(0, dev);
1087 return 0;
1088}
1089EXPORT_SYMBOL(get_anon_bdev);
1090
1091void free_anon_bdev(dev_t dev)
1092{
1093 ida_free(&unnamed_dev_ida, MINOR(dev));
1094}
1095EXPORT_SYMBOL(free_anon_bdev);
1096
1097int set_anon_super(struct super_block *s, void *data)
1098{
1099 return get_anon_bdev(&s->s_dev);
1100}
1101EXPORT_SYMBOL(set_anon_super);
1102
1103void kill_anon_super(struct super_block *sb)
1104{
1105 dev_t dev = sb->s_dev;
1106 generic_shutdown_super(sb);
1107 free_anon_bdev(dev);
1108}
1109EXPORT_SYMBOL(kill_anon_super);
1110
1111void kill_litter_super(struct super_block *sb)
1112{
1113 if (sb->s_root)
1114 d_genocide(sb->s_root);
1115 kill_anon_super(sb);
1116}
1117EXPORT_SYMBOL(kill_litter_super);
1118
1119int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
1120{
1121 return set_anon_super(sb, NULL);
1122}
1123EXPORT_SYMBOL(set_anon_super_fc);
1124
1125static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
1126{
1127 return sb->s_fs_info == fc->s_fs_info;
1128}
1129
1130static int test_single_super(struct super_block *s, struct fs_context *fc)
1131{
1132 return 1;
1133}
1134
1135/**
1136 * vfs_get_super - Get a superblock with a search key set in s_fs_info.
1137 * @fc: The filesystem context holding the parameters
1138 * @keying: How to distinguish superblocks
1139 * @fill_super: Helper to initialise a new superblock
1140 *
1141 * Search for a superblock and create a new one if not found. The search
1142 * criterion is controlled by @keying. If the search fails, a new superblock
1143 * is created and @fill_super() is called to initialise it.
1144 *
1145 * @keying can take one of a number of values:
1146 *
1147 * (1) vfs_get_single_super - Only one superblock of this type may exist on the
1148 * system. This is typically used for special system filesystems.
1149 *
1150 * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have
1151 * distinct keys (where the key is in s_fs_info). Searching for the same
1152 * key again will turn up the superblock for that key.
1153 *
1154 * (3) vfs_get_independent_super - Multiple superblocks may exist and are
1155 * unkeyed. Each call will get a new superblock.
1156 *
1157 * A permissions check is made by sget_fc() unless we're getting a superblock
1158 * for a kernel-internal mount or a submount.
1159 */
1160int vfs_get_super(struct fs_context *fc,
1161 enum vfs_get_super_keying keying,
1162 int (*fill_super)(struct super_block *sb,
1163 struct fs_context *fc))
1164{
1165 int (*test)(struct super_block *, struct fs_context *);
1166 struct super_block *sb;
1167 int err;
1168
1169 switch (keying) {
1170 case vfs_get_single_super:
1171 case vfs_get_single_reconf_super:
1172 test = test_single_super;
1173 break;
1174 case vfs_get_keyed_super:
1175 test = test_keyed_super;
1176 break;
1177 case vfs_get_independent_super:
1178 test = NULL;
1179 break;
1180 default:
1181 BUG();
1182 }
1183
1184 sb = sget_fc(fc, test, set_anon_super_fc);
1185 if (IS_ERR(sb))
1186 return PTR_ERR(sb);
1187
1188 if (!sb->s_root) {
1189 err = fill_super(sb, fc);
1190 if (err)
1191 goto error;
1192
1193 sb->s_flags |= SB_ACTIVE;
1194 fc->root = dget(sb->s_root);
1195 } else {
1196 fc->root = dget(sb->s_root);
1197 if (keying == vfs_get_single_reconf_super) {
1198 err = reconfigure_super(fc);
1199 if (err < 0) {
1200 dput(fc->root);
1201 fc->root = NULL;
1202 goto error;
1203 }
1204 }
1205 }
1206
1207 return 0;
1208
1209error:
1210 deactivate_locked_super(sb);
1211 return err;
1212}
1213EXPORT_SYMBOL(vfs_get_super);
1214
1215int get_tree_nodev(struct fs_context *fc,
1216 int (*fill_super)(struct super_block *sb,
1217 struct fs_context *fc))
1218{
1219 return vfs_get_super(fc, vfs_get_independent_super, fill_super);
1220}
1221EXPORT_SYMBOL(get_tree_nodev);
1222
1223int get_tree_single(struct fs_context *fc,
1224 int (*fill_super)(struct super_block *sb,
1225 struct fs_context *fc))
1226{
1227 return vfs_get_super(fc, vfs_get_single_super, fill_super);
1228}
1229EXPORT_SYMBOL(get_tree_single);
1230
1231int get_tree_single_reconf(struct fs_context *fc,
1232 int (*fill_super)(struct super_block *sb,
1233 struct fs_context *fc))
1234{
1235 return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super);
1236}
1237EXPORT_SYMBOL(get_tree_single_reconf);
1238
1239int get_tree_keyed(struct fs_context *fc,
1240 int (*fill_super)(struct super_block *sb,
1241 struct fs_context *fc),
1242 void *key)
1243{
1244 fc->s_fs_info = key;
1245 return vfs_get_super(fc, vfs_get_keyed_super, fill_super);
1246}
1247EXPORT_SYMBOL(get_tree_keyed);
1248
1249#ifdef CONFIG_BLOCK
1250
1251static int set_bdev_super(struct super_block *s, void *data)
1252{
1253 s->s_bdev = data;
1254 s->s_dev = s->s_bdev->bd_dev;
1255 s->s_bdi = bdi_get(s->s_bdev->bd_bdi);
1256
1257 return 0;
1258}
1259
1260static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1261{
1262 return set_bdev_super(s, fc->sget_key);
1263}
1264
1265static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1266{
1267 return s->s_bdev == fc->sget_key;
1268}
1269
1270/**
1271 * get_tree_bdev - Get a superblock based on a single block device
1272 * @fc: The filesystem context holding the parameters
1273 * @fill_super: Helper to initialise a new superblock
1274 */
1275int get_tree_bdev(struct fs_context *fc,
1276 int (*fill_super)(struct super_block *,
1277 struct fs_context *))
1278{
1279 struct block_device *bdev;
1280 struct super_block *s;
1281 fmode_t mode = FMODE_READ | FMODE_EXCL;
1282 int error = 0;
1283
1284 if (!(fc->sb_flags & SB_RDONLY))
1285 mode |= FMODE_WRITE;
1286
1287 if (!fc->source)
1288 return invalf(fc, "No source specified");
1289
1290 bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
1291 if (IS_ERR(bdev)) {
1292 errorf(fc, "%s: Can't open blockdev", fc->source);
1293 return PTR_ERR(bdev);
1294 }
1295
1296 /* Once the superblock is inserted into the list by sget_fc(), s_umount
1297 * will protect the lockfs code from trying to start a snapshot while
1298 * we are mounting
1299 */
1300 mutex_lock(&bdev->bd_fsfreeze_mutex);
1301 if (bdev->bd_fsfreeze_count > 0) {
1302 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1303 blkdev_put(bdev, mode);
1304 warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
1305 return -EBUSY;
1306 }
1307
1308 fc->sb_flags |= SB_NOSEC;
1309 fc->sget_key = bdev;
1310 s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
1311 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1312 if (IS_ERR(s)) {
1313 blkdev_put(bdev, mode);
1314 return PTR_ERR(s);
1315 }
1316
1317 if (s->s_root) {
1318 /* Don't summarily change the RO/RW state. */
1319 if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
1320 warnf(fc, "%pg: Can't mount, would change RO state", bdev);
1321 deactivate_locked_super(s);
1322 blkdev_put(bdev, mode);
1323 return -EBUSY;
1324 }
1325
1326 /*
1327 * s_umount nests inside bd_mutex during
1328 * __invalidate_device(). blkdev_put() acquires
1329 * bd_mutex and can't be called under s_umount. Drop
1330 * s_umount temporarily. This is safe as we're
1331 * holding an active reference.
1332 */
1333 up_write(&s->s_umount);
1334 blkdev_put(bdev, mode);
1335 down_write(&s->s_umount);
1336 } else {
1337 s->s_mode = mode;
1338 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1339 sb_set_blocksize(s, block_size(bdev));
1340 error = fill_super(s, fc);
1341 if (error) {
1342 deactivate_locked_super(s);
1343 return error;
1344 }
1345
1346 s->s_flags |= SB_ACTIVE;
1347 bdev->bd_super = s;
1348 }
1349
1350 BUG_ON(fc->root);
1351 fc->root = dget(s->s_root);
1352 return 0;
1353}
1354EXPORT_SYMBOL(get_tree_bdev);
1355
1356static int test_bdev_super(struct super_block *s, void *data)
1357{
1358 return (void *)s->s_bdev == data;
1359}
1360
1361struct dentry *mount_bdev(struct file_system_type *fs_type,
1362 int flags, const char *dev_name, void *data,
1363 int (*fill_super)(struct super_block *, void *, int))
1364{
1365 struct block_device *bdev;
1366 struct super_block *s;
1367 fmode_t mode = FMODE_READ | FMODE_EXCL;
1368 int error = 0;
1369
1370 if (!(flags & SB_RDONLY))
1371 mode |= FMODE_WRITE;
1372
1373 bdev = blkdev_get_by_path(dev_name, mode, fs_type);
1374 if (IS_ERR(bdev))
1375 return ERR_CAST(bdev);
1376
1377 /*
1378 * once the super is inserted into the list by sget, s_umount
1379 * will protect the lockfs code from trying to start a snapshot
1380 * while we are mounting
1381 */
1382 mutex_lock(&bdev->bd_fsfreeze_mutex);
1383 if (bdev->bd_fsfreeze_count > 0) {
1384 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1385 error = -EBUSY;
1386 goto error_bdev;
1387 }
1388 s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC,
1389 bdev);
1390 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1391 if (IS_ERR(s))
1392 goto error_s;
1393
1394 if (s->s_root) {
1395 if ((flags ^ s->s_flags) & SB_RDONLY) {
1396 deactivate_locked_super(s);
1397 error = -EBUSY;
1398 goto error_bdev;
1399 }
1400
1401 /*
1402 * s_umount nests inside bd_mutex during
1403 * __invalidate_device(). blkdev_put() acquires
1404 * bd_mutex and can't be called under s_umount. Drop
1405 * s_umount temporarily. This is safe as we're
1406 * holding an active reference.
1407 */
1408 up_write(&s->s_umount);
1409 blkdev_put(bdev, mode);
1410 down_write(&s->s_umount);
1411 } else {
1412 s->s_mode = mode;
1413 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1414 sb_set_blocksize(s, block_size(bdev));
1415 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1416 if (error) {
1417 deactivate_locked_super(s);
1418 goto error;
1419 }
1420
1421 s->s_flags |= SB_ACTIVE;
1422 bdev->bd_super = s;
1423 }
1424
1425 return dget(s->s_root);
1426
1427error_s:
1428 error = PTR_ERR(s);
1429error_bdev:
1430 blkdev_put(bdev, mode);
1431error:
1432 return ERR_PTR(error);
1433}
1434EXPORT_SYMBOL(mount_bdev);
1435
1436void kill_block_super(struct super_block *sb)
1437{
1438 struct block_device *bdev = sb->s_bdev;
1439 fmode_t mode = sb->s_mode;
1440
1441 bdev->bd_super = NULL;
1442 generic_shutdown_super(sb);
1443 sync_blockdev(bdev);
1444 WARN_ON_ONCE(!(mode & FMODE_EXCL));
1445 blkdev_put(bdev, mode | FMODE_EXCL);
1446}
1447
1448EXPORT_SYMBOL(kill_block_super);
1449#endif
1450
1451struct dentry *mount_nodev(struct file_system_type *fs_type,
1452 int flags, void *data,
1453 int (*fill_super)(struct super_block *, void *, int))
1454{
1455 int error;
1456 struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1457
1458 if (IS_ERR(s))
1459 return ERR_CAST(s);
1460
1461 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1462 if (error) {
1463 deactivate_locked_super(s);
1464 return ERR_PTR(error);
1465 }
1466 s->s_flags |= SB_ACTIVE;
1467 return dget(s->s_root);
1468}
1469EXPORT_SYMBOL(mount_nodev);
1470
1471static int reconfigure_single(struct super_block *s,
1472 int flags, void *data)
1473{
1474 struct fs_context *fc;
1475 int ret;
1476
1477 /* The caller really need to be passing fc down into mount_single(),
1478 * then a chunk of this can be removed. [Bollocks -- AV]
1479 * Better yet, reconfiguration shouldn't happen, but rather the second
1480 * mount should be rejected if the parameters are not compatible.
1481 */
1482 fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
1483 if (IS_ERR(fc))
1484 return PTR_ERR(fc);
1485
1486 ret = parse_monolithic_mount_data(fc, data);
1487 if (ret < 0)
1488 goto out;
1489
1490 ret = reconfigure_super(fc);
1491out:
1492 put_fs_context(fc);
1493 return ret;
1494}
1495
1496static int compare_single(struct super_block *s, void *p)
1497{
1498 return 1;
1499}
1500
1501struct dentry *mount_single(struct file_system_type *fs_type,
1502 int flags, void *data,
1503 int (*fill_super)(struct super_block *, void *, int))
1504{
1505 struct super_block *s;
1506 int error;
1507
1508 s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1509 if (IS_ERR(s))
1510 return ERR_CAST(s);
1511 if (!s->s_root) {
1512 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1513 if (!error)
1514 s->s_flags |= SB_ACTIVE;
1515 } else {
1516 error = reconfigure_single(s, flags, data);
1517 }
1518 if (unlikely(error)) {
1519 deactivate_locked_super(s);
1520 return ERR_PTR(error);
1521 }
1522 return dget(s->s_root);
1523}
1524EXPORT_SYMBOL(mount_single);
1525
1526/**
1527 * vfs_get_tree - Get the mountable root
1528 * @fc: The superblock configuration context.
1529 *
1530 * The filesystem is invoked to get or create a superblock which can then later
1531 * be used for mounting. The filesystem places a pointer to the root to be
1532 * used for mounting in @fc->root.
1533 */
1534int vfs_get_tree(struct fs_context *fc)
1535{
1536 struct super_block *sb;
1537 int error;
1538
1539 if (fc->root)
1540 return -EBUSY;
1541
1542 /* Get the mountable root in fc->root, with a ref on the root and a ref
1543 * on the superblock.
1544 */
1545 error = fc->ops->get_tree(fc);
1546 if (error < 0)
1547 return error;
1548
1549 if (!fc->root) {
1550 pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1551 fc->fs_type->name);
1552 /* We don't know what the locking state of the superblock is -
1553 * if there is a superblock.
1554 */
1555 BUG();
1556 }
1557
1558 sb = fc->root->d_sb;
1559 WARN_ON(!sb->s_bdi);
1560
1561 /*
1562 * Write barrier is for super_cache_count(). We place it before setting
1563 * SB_BORN as the data dependency between the two functions is the
1564 * superblock structure contents that we just set up, not the SB_BORN
1565 * flag.
1566 */
1567 smp_wmb();
1568 sb->s_flags |= SB_BORN;
1569
1570 error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
1571 if (unlikely(error)) {
1572 fc_drop_locked(fc);
1573 return error;
1574 }
1575
1576 /*
1577 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1578 * but s_maxbytes was an unsigned long long for many releases. Throw
1579 * this warning for a little while to try and catch filesystems that
1580 * violate this rule.
1581 */
1582 WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1583 "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);
1584
1585 return 0;
1586}
1587EXPORT_SYMBOL(vfs_get_tree);
1588
1589/*
1590 * Setup private BDI for given superblock. It gets automatically cleaned up
1591 * in generic_shutdown_super().
1592 */
1593int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
1594{
1595 struct backing_dev_info *bdi;
1596 int err;
1597 va_list args;
1598
1599 bdi = bdi_alloc(GFP_KERNEL);
1600 if (!bdi)
1601 return -ENOMEM;
1602
1603 bdi->name = sb->s_type->name;
1604
1605 va_start(args, fmt);
1606 err = bdi_register_va(bdi, fmt, args);
1607 va_end(args);
1608 if (err) {
1609 bdi_put(bdi);
1610 return err;
1611 }
1612 WARN_ON(sb->s_bdi != &noop_backing_dev_info);
1613 sb->s_bdi = bdi;
1614
1615 return 0;
1616}
1617EXPORT_SYMBOL(super_setup_bdi_name);
1618
1619/*
1620 * Setup private BDI for given superblock. I gets automatically cleaned up
1621 * in generic_shutdown_super().
1622 */
1623int super_setup_bdi(struct super_block *sb)
1624{
1625 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
1626
1627 return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
1628 atomic_long_inc_return(&bdi_seq));
1629}
1630EXPORT_SYMBOL(super_setup_bdi);
1631
1632/*
1633 * This is an internal function, please use sb_end_{write,pagefault,intwrite}
1634 * instead.
1635 */
1636void __sb_end_write(struct super_block *sb, int level)
1637{
1638 percpu_up_read(sb->s_writers.rw_sem + level-1);
1639}
1640EXPORT_SYMBOL(__sb_end_write);
1641
1642/*
1643 * This is an internal function, please use sb_start_{write,pagefault,intwrite}
1644 * instead.
1645 */
1646int __sb_start_write(struct super_block *sb, int level, bool wait)
1647{
1648 bool force_trylock = false;
1649 int ret = 1;
1650
1651#ifdef CONFIG_LOCKDEP
1652 /*
1653 * We want lockdep to tell us about possible deadlocks with freezing
1654 * but it's it bit tricky to properly instrument it. Getting a freeze
1655 * protection works as getting a read lock but there are subtle
1656 * problems. XFS for example gets freeze protection on internal level
1657 * twice in some cases, which is OK only because we already hold a
1658 * freeze protection also on higher level. Due to these cases we have
1659 * to use wait == F (trylock mode) which must not fail.
1660 */
1661 if (wait) {
1662 int i;
1663
1664 for (i = 0; i < level - 1; i++)
1665 if (percpu_rwsem_is_held(sb->s_writers.rw_sem + i)) {
1666 force_trylock = true;
1667 break;
1668 }
1669 }
1670#endif
1671 if (wait && !force_trylock)
1672 percpu_down_read(sb->s_writers.rw_sem + level-1);
1673 else
1674 ret = percpu_down_read_trylock(sb->s_writers.rw_sem + level-1);
1675
1676 WARN_ON(force_trylock && !ret);
1677 return ret;
1678}
1679EXPORT_SYMBOL(__sb_start_write);
1680
1681/**
1682 * sb_wait_write - wait until all writers to given file system finish
1683 * @sb: the super for which we wait
1684 * @level: type of writers we wait for (normal vs page fault)
1685 *
1686 * This function waits until there are no writers of given type to given file
1687 * system.
1688 */
1689static void sb_wait_write(struct super_block *sb, int level)
1690{
1691 percpu_down_write(sb->s_writers.rw_sem + level-1);
1692}
1693
1694/*
1695 * We are going to return to userspace and forget about these locks, the
1696 * ownership goes to the caller of thaw_super() which does unlock().
1697 */
1698static void lockdep_sb_freeze_release(struct super_block *sb)
1699{
1700 int level;
1701
1702 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1703 percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1704}
1705
1706/*
1707 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1708 */
1709static void lockdep_sb_freeze_acquire(struct super_block *sb)
1710{
1711 int level;
1712
1713 for (level = 0; level < SB_FREEZE_LEVELS; ++level)
1714 percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1715}
1716
1717static void sb_freeze_unlock(struct super_block *sb)
1718{
1719 int level;
1720
1721 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1722 percpu_up_write(sb->s_writers.rw_sem + level);
1723}
1724
1725/**
1726 * freeze_super - lock the filesystem and force it into a consistent state
1727 * @sb: the super to lock
1728 *
1729 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1730 * freeze_fs. Subsequent calls to this without first thawing the fs will return
1731 * -EBUSY.
1732 *
1733 * During this function, sb->s_writers.frozen goes through these values:
1734 *
1735 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1736 *
1737 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1738 * writes should be blocked, though page faults are still allowed. We wait for
1739 * all writes to complete and then proceed to the next stage.
1740 *
1741 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1742 * but internal fs threads can still modify the filesystem (although they
1743 * should not dirty new pages or inodes), writeback can run etc. After waiting
1744 * for all running page faults we sync the filesystem which will clean all
1745 * dirty pages and inodes (no new dirty pages or inodes can be created when
1746 * sync is running).
1747 *
1748 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1749 * modification are blocked (e.g. XFS preallocation truncation on inode
1750 * reclaim). This is usually implemented by blocking new transactions for
1751 * filesystems that have them and need this additional guard. After all
1752 * internal writers are finished we call ->freeze_fs() to finish filesystem
1753 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1754 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1755 *
1756 * sb->s_writers.frozen is protected by sb->s_umount.
1757 */
1758int freeze_super(struct super_block *sb)
1759{
1760 int ret;
1761
1762 atomic_inc(&sb->s_active);
1763 down_write(&sb->s_umount);
1764 if (sb->s_writers.frozen != SB_UNFROZEN) {
1765 deactivate_locked_super(sb);
1766 return -EBUSY;
1767 }
1768
1769 if (!(sb->s_flags & SB_BORN)) {
1770 up_write(&sb->s_umount);
1771 return 0; /* sic - it's "nothing to do" */
1772 }
1773
1774 if (sb_rdonly(sb)) {
1775 /* Nothing to do really... */
1776 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1777 up_write(&sb->s_umount);
1778 return 0;
1779 }
1780
1781 sb->s_writers.frozen = SB_FREEZE_WRITE;
1782 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1783 up_write(&sb->s_umount);
1784 sb_wait_write(sb, SB_FREEZE_WRITE);
1785 down_write(&sb->s_umount);
1786
1787 /* Now we go and block page faults... */
1788 sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
1789 sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
1790
1791 /* All writers are done so after syncing there won't be dirty data */
1792 sync_filesystem(sb);
1793
1794 /* Now wait for internal filesystem counter */
1795 sb->s_writers.frozen = SB_FREEZE_FS;
1796 sb_wait_write(sb, SB_FREEZE_FS);
1797
1798 if (sb->s_op->freeze_fs) {
1799 ret = sb->s_op->freeze_fs(sb);
1800 if (ret) {
1801 printk(KERN_ERR
1802 "VFS:Filesystem freeze failed\n");
1803 sb->s_writers.frozen = SB_UNFROZEN;
1804 sb_freeze_unlock(sb);
1805 wake_up(&sb->s_writers.wait_unfrozen);
1806 deactivate_locked_super(sb);
1807 return ret;
1808 }
1809 }
1810 /*
1811 * For debugging purposes so that fs can warn if it sees write activity
1812 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
1813 */
1814 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1815 lockdep_sb_freeze_release(sb);
1816 up_write(&sb->s_umount);
1817 return 0;
1818}
1819EXPORT_SYMBOL(freeze_super);
1820
1821/**
1822 * thaw_super -- unlock filesystem
1823 * @sb: the super to thaw
1824 *
1825 * Unlocks the filesystem and marks it writeable again after freeze_super().
1826 */
1827static int thaw_super_locked(struct super_block *sb)
1828{
1829 int error;
1830
1831 if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
1832 up_write(&sb->s_umount);
1833 return -EINVAL;
1834 }
1835
1836 if (sb_rdonly(sb)) {
1837 sb->s_writers.frozen = SB_UNFROZEN;
1838 goto out;
1839 }
1840
1841 lockdep_sb_freeze_acquire(sb);
1842
1843 if (sb->s_op->unfreeze_fs) {
1844 error = sb->s_op->unfreeze_fs(sb);
1845 if (error) {
1846 printk(KERN_ERR
1847 "VFS:Filesystem thaw failed\n");
1848 lockdep_sb_freeze_release(sb);
1849 up_write(&sb->s_umount);
1850 return error;
1851 }
1852 }
1853
1854 sb->s_writers.frozen = SB_UNFROZEN;
1855 sb_freeze_unlock(sb);
1856out:
1857 wake_up(&sb->s_writers.wait_unfrozen);
1858 deactivate_locked_super(sb);
1859 return 0;
1860}
1861
1862int thaw_super(struct super_block *sb)
1863{
1864 down_write(&sb->s_umount);
1865 return thaw_super_locked(sb);
1866}
1867EXPORT_SYMBOL(thaw_super);
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/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 inline void __super_lock(struct super_block *sb, bool excl)
54{
55 if (excl)
56 down_write(&sb->s_umount);
57 else
58 down_read(&sb->s_umount);
59}
60
61static inline void super_unlock(struct super_block *sb, bool excl)
62{
63 if (excl)
64 up_write(&sb->s_umount);
65 else
66 up_read(&sb->s_umount);
67}
68
69static inline void __super_lock_excl(struct super_block *sb)
70{
71 __super_lock(sb, true);
72}
73
74static inline void super_unlock_excl(struct super_block *sb)
75{
76 super_unlock(sb, true);
77}
78
79static 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 ensures
88 * 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 it
95 * @sb: superblock to wait for
96 * @excl: whether exclusive access is required
97 *
98 * If the superblock has neither passed through vfs_get_tree() or
99 * generic_shutdown_super() yet wait for it to happen. Either superblock
100 * creation will succeed and SB_BORN is set by vfs_get_tree() or we're
101 * 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 with
106 * s_umount held. The function returns false if SB_DYING was
107 * set and without s_umount held.
108 */
109static __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 to
125 * 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 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 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 sure
157 * all initializations in the superblock are seen by the user
158 * 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 sure
163 * ___wait_var_event() either sees SB_BORN set or
164 * 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't
172 * drop the last active reference to the superblock from within the shrinker.
173 * If that happens we could trigger unregistering the shrinker from within the
174 * shrinker path and that leads to deadlock on the shrinker_mutex. Hence we
175 * take a passive reference to the superblock to avoid this from occurring.
176 */
177static 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 want
191 * 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, then
215 * prune the icache, followed by the filesystem specific caches
216 *
217 * Ensure that we always scan at least one object - memcg kmem
218 * 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 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 scalability
244 * bottleneck, so we're exposed to partial setup state. The shrinker
245 * rwsem does not protect filesystem operations backing
246 * list_lru_shrink_count() or s_op->nr_cached_objects(). Counts can
247 * change between super_cache_count and super_cache_scan, so we really
248 * don't need locks here.
249 *
250 * However, if we are currently mounting the superblock, the underlying
251 * filesystem might be in a state of partial construction and hence it
252 * is dangerous to access it. super_trylock_shared() uses a SB_BORN check
253 * to avoid this situation, so do the same here. The memory barrier is
254 * 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 security_sb_free(s);
278 put_user_ns(s->s_user_ns);
279 kfree(s->s_subtype);
280 for (int i = 0; i < SB_FREEZE_LEVELS; i++)
281 percpu_free_rwsem(&s->s_writers.rw_sem[i]);
282 kfree(s);
283}
284
285static void destroy_super_rcu(struct rcu_head *head)
286{
287 struct super_block *s = container_of(head, struct super_block, rcu);
288 INIT_WORK(&s->destroy_work, destroy_super_work);
289 schedule_work(&s->destroy_work);
290}
291
292/* Free a superblock that has never been seen by anyone */
293static void destroy_unused_super(struct super_block *s)
294{
295 if (!s)
296 return;
297 super_unlock_excl(s);
298 list_lru_destroy(&s->s_dentry_lru);
299 list_lru_destroy(&s->s_inode_lru);
300 shrinker_free(s->s_shrink);
301 /* no delays needed */
302 destroy_super_work(&s->destroy_work);
303}
304
305/**
306 * alloc_super - create new superblock
307 * @type: filesystem type superblock should belong to
308 * @flags: the mount flags
309 * @user_ns: User namespace for the super_block
310 *
311 * Allocates and initializes a new &struct super_block. alloc_super()
312 * returns a pointer new superblock or %NULL if allocation had failed.
313 */
314static struct super_block *alloc_super(struct file_system_type *type, int flags,
315 struct user_namespace *user_ns)
316{
317 struct super_block *s = kzalloc(sizeof(struct super_block), GFP_KERNEL);
318 static const struct super_operations default_op;
319 int i;
320
321 if (!s)
322 return NULL;
323
324 INIT_LIST_HEAD(&s->s_mounts);
325 s->s_user_ns = get_user_ns(user_ns);
326 init_rwsem(&s->s_umount);
327 lockdep_set_class(&s->s_umount, &type->s_umount_key);
328 /*
329 * sget() can have s_umount recursion.
330 *
331 * When it cannot find a suitable sb, it allocates a new
332 * one (this one), and tries again to find a suitable old
333 * one.
334 *
335 * In case that succeeds, it will acquire the s_umount
336 * lock of the old one. Since these are clearly distrinct
337 * locks, and this object isn't exposed yet, there's no
338 * risk of deadlocks.
339 *
340 * Annotate this by putting this lock in a different
341 * subclass.
342 */
343 down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
344
345 if (security_sb_alloc(s))
346 goto fail;
347
348 for (i = 0; i < SB_FREEZE_LEVELS; i++) {
349 if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
350 sb_writers_name[i],
351 &type->s_writers_key[i]))
352 goto fail;
353 }
354 s->s_bdi = &noop_backing_dev_info;
355 s->s_flags = flags;
356 if (s->s_user_ns != &init_user_ns)
357 s->s_iflags |= SB_I_NODEV;
358 INIT_HLIST_NODE(&s->s_instances);
359 INIT_HLIST_BL_HEAD(&s->s_roots);
360 mutex_init(&s->s_sync_lock);
361 INIT_LIST_HEAD(&s->s_inodes);
362 spin_lock_init(&s->s_inode_list_lock);
363 INIT_LIST_HEAD(&s->s_inodes_wb);
364 spin_lock_init(&s->s_inode_wblist_lock);
365
366 s->s_count = 1;
367 atomic_set(&s->s_active, 1);
368 mutex_init(&s->s_vfs_rename_mutex);
369 lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
370 init_rwsem(&s->s_dquot.dqio_sem);
371 s->s_maxbytes = MAX_NON_LFS;
372 s->s_op = &default_op;
373 s->s_time_gran = 1000000000;
374 s->s_time_min = TIME64_MIN;
375 s->s_time_max = TIME64_MAX;
376
377 s->s_shrink = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,
378 "sb-%s", type->name);
379 if (!s->s_shrink)
380 goto fail;
381
382 s->s_shrink->scan_objects = super_cache_scan;
383 s->s_shrink->count_objects = super_cache_count;
384 s->s_shrink->batch = 1024;
385 s->s_shrink->private_data = s;
386
387 if (list_lru_init_memcg(&s->s_dentry_lru, s->s_shrink))
388 goto fail;
389 if (list_lru_init_memcg(&s->s_inode_lru, s->s_shrink))
390 goto fail;
391 return s;
392
393fail:
394 destroy_unused_super(s);
395 return NULL;
396}
397
398/* Superblock refcounting */
399
400/*
401 * Drop a superblock's refcount. The caller must hold sb_lock.
402 */
403static void __put_super(struct super_block *s)
404{
405 if (!--s->s_count) {
406 list_del_init(&s->s_list);
407 WARN_ON(s->s_dentry_lru.node);
408 WARN_ON(s->s_inode_lru.node);
409 WARN_ON(!list_empty(&s->s_mounts));
410 call_rcu(&s->rcu, destroy_super_rcu);
411 }
412}
413
414/**
415 * put_super - drop a temporary reference to superblock
416 * @sb: superblock in question
417 *
418 * Drops a temporary reference, frees superblock if there's no
419 * references left.
420 */
421void put_super(struct super_block *sb)
422{
423 spin_lock(&sb_lock);
424 __put_super(sb);
425 spin_unlock(&sb_lock);
426}
427
428static void kill_super_notify(struct super_block *sb)
429{
430 lockdep_assert_not_held(&sb->s_umount);
431
432 /* already notified earlier */
433 if (sb->s_flags & SB_DEAD)
434 return;
435
436 /*
437 * Remove it from @fs_supers so it isn't found by new
438 * sget{_fc}() walkers anymore. Any concurrent mounter still
439 * managing to grab a temporary reference is guaranteed to
440 * already see SB_DYING and will wait until we notify them about
441 * SB_DEAD.
442 */
443 spin_lock(&sb_lock);
444 hlist_del_init(&sb->s_instances);
445 spin_unlock(&sb_lock);
446
447 /*
448 * Let concurrent mounts know that this thing is really dead.
449 * We don't need @sb->s_umount here as every concurrent caller
450 * will see SB_DYING and either discard the superblock or wait
451 * for SB_DEAD.
452 */
453 super_wake(sb, SB_DEAD);
454}
455
456/**
457 * deactivate_locked_super - drop an active reference to superblock
458 * @s: superblock to deactivate
459 *
460 * Drops an active reference to superblock, converting it into a temporary
461 * one if there is no other active references left. In that case we
462 * tell fs driver to shut it down and drop the temporary reference we
463 * had just acquired.
464 *
465 * Caller holds exclusive lock on superblock; that lock is released.
466 */
467void deactivate_locked_super(struct super_block *s)
468{
469 struct file_system_type *fs = s->s_type;
470 if (atomic_dec_and_test(&s->s_active)) {
471 shrinker_free(s->s_shrink);
472 fs->kill_sb(s);
473
474 kill_super_notify(s);
475
476 /*
477 * Since list_lru_destroy() may sleep, we cannot call it from
478 * put_super(), where we hold the sb_lock. Therefore we destroy
479 * the lru lists right now.
480 */
481 list_lru_destroy(&s->s_dentry_lru);
482 list_lru_destroy(&s->s_inode_lru);
483
484 put_filesystem(fs);
485 put_super(s);
486 } else {
487 super_unlock_excl(s);
488 }
489}
490
491EXPORT_SYMBOL(deactivate_locked_super);
492
493/**
494 * deactivate_super - drop an active reference to superblock
495 * @s: superblock to deactivate
496 *
497 * Variant of deactivate_locked_super(), except that superblock is *not*
498 * locked by caller. If we are going to drop the final active reference,
499 * lock will be acquired prior to that.
500 */
501void deactivate_super(struct super_block *s)
502{
503 if (!atomic_add_unless(&s->s_active, -1, 1)) {
504 __super_lock_excl(s);
505 deactivate_locked_super(s);
506 }
507}
508
509EXPORT_SYMBOL(deactivate_super);
510
511/**
512 * grab_super - acquire an active reference to a superblock
513 * @sb: superblock to acquire
514 *
515 * Acquire a temporary reference on a superblock and try to trade it for
516 * an active reference. This is used in sget{_fc}() to wait for a
517 * superblock to either become SB_BORN or for it to pass through
518 * sb->kill() and be marked as SB_DEAD.
519 *
520 * Return: This returns true if an active reference could be acquired,
521 * false if not.
522 */
523static bool grab_super(struct super_block *sb)
524{
525 bool locked;
526
527 sb->s_count++;
528 spin_unlock(&sb_lock);
529 locked = super_lock_excl(sb);
530 if (locked) {
531 if (atomic_inc_not_zero(&sb->s_active)) {
532 put_super(sb);
533 return true;
534 }
535 super_unlock_excl(sb);
536 }
537 wait_var_event(&sb->s_flags, super_flags(sb, SB_DEAD));
538 put_super(sb);
539 return false;
540}
541
542/*
543 * super_trylock_shared - try to grab ->s_umount shared
544 * @sb: reference we are trying to grab
545 *
546 * Try to prevent fs shutdown. This is used in places where we
547 * cannot take an active reference but we need to ensure that the
548 * filesystem is not shut down while we are working on it. It returns
549 * false if we cannot acquire s_umount or if we lose the race and
550 * filesystem already got into shutdown, and returns true with the s_umount
551 * lock held in read mode in case of success. On successful return,
552 * the caller must drop the s_umount lock when done.
553 *
554 * Note that unlike get_super() et.al. this one does *not* bump ->s_count.
555 * The reason why it's safe is that we are OK with doing trylock instead
556 * of down_read(). There's a couple of places that are OK with that, but
557 * it's very much not a general-purpose interface.
558 */
559bool super_trylock_shared(struct super_block *sb)
560{
561 if (down_read_trylock(&sb->s_umount)) {
562 if (!(sb->s_flags & SB_DYING) && sb->s_root &&
563 (sb->s_flags & SB_BORN))
564 return true;
565 super_unlock_shared(sb);
566 }
567
568 return false;
569}
570
571/**
572 * retire_super - prevents superblock from being reused
573 * @sb: superblock to retire
574 *
575 * The function marks superblock to be ignored in superblock test, which
576 * prevents it from being reused for any new mounts. If the superblock has
577 * a private bdi, it also unregisters it, but doesn't reduce the refcount
578 * of the superblock to prevent potential races. The refcount is reduced
579 * by generic_shutdown_super(). The function can not be called
580 * concurrently with generic_shutdown_super(). It is safe to call the
581 * function multiple times, subsequent calls have no effect.
582 *
583 * The marker will affect the re-use only for block-device-based
584 * superblocks. Other superblocks will still get marked if this function
585 * is used, but that will not affect their reusability.
586 */
587void retire_super(struct super_block *sb)
588{
589 WARN_ON(!sb->s_bdev);
590 __super_lock_excl(sb);
591 if (sb->s_iflags & SB_I_PERSB_BDI) {
592 bdi_unregister(sb->s_bdi);
593 sb->s_iflags &= ~SB_I_PERSB_BDI;
594 }
595 sb->s_iflags |= SB_I_RETIRED;
596 super_unlock_excl(sb);
597}
598EXPORT_SYMBOL(retire_super);
599
600/**
601 * generic_shutdown_super - common helper for ->kill_sb()
602 * @sb: superblock to kill
603 *
604 * generic_shutdown_super() does all fs-independent work on superblock
605 * shutdown. Typical ->kill_sb() should pick all fs-specific objects
606 * that need destruction out of superblock, call generic_shutdown_super()
607 * and release aforementioned objects. Note: dentries and inodes _are_
608 * taken care of and do not need specific handling.
609 *
610 * Upon calling this function, the filesystem may no longer alter or
611 * rearrange the set of dentries belonging to this super_block, nor may it
612 * change the attachments of dentries to inodes.
613 */
614void generic_shutdown_super(struct super_block *sb)
615{
616 const struct super_operations *sop = sb->s_op;
617
618 if (sb->s_root) {
619 shrink_dcache_for_umount(sb);
620 sync_filesystem(sb);
621 sb->s_flags &= ~SB_ACTIVE;
622
623 cgroup_writeback_umount();
624
625 /* Evict all inodes with zero refcount. */
626 evict_inodes(sb);
627
628 /*
629 * Clean up and evict any inodes that still have references due
630 * to fsnotify or the security policy.
631 */
632 fsnotify_sb_delete(sb);
633 security_sb_delete(sb);
634
635 if (sb->s_dio_done_wq) {
636 destroy_workqueue(sb->s_dio_done_wq);
637 sb->s_dio_done_wq = NULL;
638 }
639
640 if (sop->put_super)
641 sop->put_super(sb);
642
643 /*
644 * Now that all potentially-encrypted inodes have been evicted,
645 * the fscrypt keyring can be destroyed.
646 */
647 fscrypt_destroy_keyring(sb);
648
649 if (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes),
650 "VFS: Busy inodes after unmount of %s (%s)",
651 sb->s_id, sb->s_type->name)) {
652 /*
653 * Adding a proper bailout path here would be hard, but
654 * we can at least make it more likely that a later
655 * iput_final() or such crashes cleanly.
656 */
657 struct inode *inode;
658
659 spin_lock(&sb->s_inode_list_lock);
660 list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
661 inode->i_op = VFS_PTR_POISON;
662 inode->i_sb = VFS_PTR_POISON;
663 inode->i_mapping = VFS_PTR_POISON;
664 }
665 spin_unlock(&sb->s_inode_list_lock);
666 }
667 }
668 /*
669 * Broadcast to everyone that grabbed a temporary reference to this
670 * superblock before we removed it from @fs_supers that the superblock
671 * is dying. Every walker of @fs_supers outside of sget{_fc}() will now
672 * discard this superblock and treat it as dead.
673 *
674 * We leave the superblock on @fs_supers so it can be found by
675 * sget{_fc}() until we passed sb->kill_sb().
676 */
677 super_wake(sb, SB_DYING);
678 super_unlock_excl(sb);
679 if (sb->s_bdi != &noop_backing_dev_info) {
680 if (sb->s_iflags & SB_I_PERSB_BDI)
681 bdi_unregister(sb->s_bdi);
682 bdi_put(sb->s_bdi);
683 sb->s_bdi = &noop_backing_dev_info;
684 }
685}
686
687EXPORT_SYMBOL(generic_shutdown_super);
688
689bool mount_capable(struct fs_context *fc)
690{
691 if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
692 return capable(CAP_SYS_ADMIN);
693 else
694 return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
695}
696
697/**
698 * sget_fc - Find or create a superblock
699 * @fc: Filesystem context.
700 * @test: Comparison callback
701 * @set: Setup callback
702 *
703 * Create a new superblock or find an existing one.
704 *
705 * The @test callback is used to find a matching existing superblock.
706 * Whether or not the requested parameters in @fc are taken into account
707 * is specific to the @test callback that is used. They may even be
708 * completely ignored.
709 *
710 * If an extant superblock is matched, it will be returned unless:
711 *
712 * (1) the namespace the filesystem context @fc and the extant
713 * superblock's namespace differ
714 *
715 * (2) the filesystem context @fc has requested that reusing an extant
716 * superblock is not allowed
717 *
718 * In both cases EBUSY will be returned.
719 *
720 * If no match is made, a new superblock will be allocated and basic
721 * initialisation will be performed (s_type, s_fs_info and s_id will be
722 * set and the @set callback will be invoked), the superblock will be
723 * published and it will be returned in a partially constructed state
724 * with SB_BORN and SB_ACTIVE as yet unset.
725 *
726 * Return: On success, an extant or newly created superblock is
727 * returned. On failure an error pointer is returned.
728 */
729struct super_block *sget_fc(struct fs_context *fc,
730 int (*test)(struct super_block *, struct fs_context *),
731 int (*set)(struct super_block *, struct fs_context *))
732{
733 struct super_block *s = NULL;
734 struct super_block *old;
735 struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
736 int err;
737
738retry:
739 spin_lock(&sb_lock);
740 if (test) {
741 hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
742 if (test(old, fc))
743 goto share_extant_sb;
744 }
745 }
746 if (!s) {
747 spin_unlock(&sb_lock);
748 s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
749 if (!s)
750 return ERR_PTR(-ENOMEM);
751 goto retry;
752 }
753
754 s->s_fs_info = fc->s_fs_info;
755 err = set(s, fc);
756 if (err) {
757 s->s_fs_info = NULL;
758 spin_unlock(&sb_lock);
759 destroy_unused_super(s);
760 return ERR_PTR(err);
761 }
762 fc->s_fs_info = NULL;
763 s->s_type = fc->fs_type;
764 s->s_iflags |= fc->s_iflags;
765 strscpy(s->s_id, s->s_type->name, sizeof(s->s_id));
766 /*
767 * Make the superblock visible on @super_blocks and @fs_supers.
768 * It's in a nascent state and users should wait on SB_BORN or
769 * SB_DYING to be set.
770 */
771 list_add_tail(&s->s_list, &super_blocks);
772 hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
773 spin_unlock(&sb_lock);
774 get_filesystem(s->s_type);
775 shrinker_register(s->s_shrink);
776 return s;
777
778share_extant_sb:
779 if (user_ns != old->s_user_ns || fc->exclusive) {
780 spin_unlock(&sb_lock);
781 destroy_unused_super(s);
782 if (fc->exclusive)
783 warnfc(fc, "reusing existing filesystem not allowed");
784 else
785 warnfc(fc, "reusing existing filesystem in another namespace not allowed");
786 return ERR_PTR(-EBUSY);
787 }
788 if (!grab_super(old))
789 goto retry;
790 destroy_unused_super(s);
791 return old;
792}
793EXPORT_SYMBOL(sget_fc);
794
795/**
796 * sget - find or create a superblock
797 * @type: filesystem type superblock should belong to
798 * @test: comparison callback
799 * @set: setup callback
800 * @flags: mount flags
801 * @data: argument to each of them
802 */
803struct super_block *sget(struct file_system_type *type,
804 int (*test)(struct super_block *,void *),
805 int (*set)(struct super_block *,void *),
806 int flags,
807 void *data)
808{
809 struct user_namespace *user_ns = current_user_ns();
810 struct super_block *s = NULL;
811 struct super_block *old;
812 int err;
813
814 /* We don't yet pass the user namespace of the parent
815 * mount through to here so always use &init_user_ns
816 * until that changes.
817 */
818 if (flags & SB_SUBMOUNT)
819 user_ns = &init_user_ns;
820
821retry:
822 spin_lock(&sb_lock);
823 if (test) {
824 hlist_for_each_entry(old, &type->fs_supers, s_instances) {
825 if (!test(old, data))
826 continue;
827 if (user_ns != old->s_user_ns) {
828 spin_unlock(&sb_lock);
829 destroy_unused_super(s);
830 return ERR_PTR(-EBUSY);
831 }
832 if (!grab_super(old))
833 goto retry;
834 destroy_unused_super(s);
835 return old;
836 }
837 }
838 if (!s) {
839 spin_unlock(&sb_lock);
840 s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
841 if (!s)
842 return ERR_PTR(-ENOMEM);
843 goto retry;
844 }
845
846 err = set(s, data);
847 if (err) {
848 spin_unlock(&sb_lock);
849 destroy_unused_super(s);
850 return ERR_PTR(err);
851 }
852 s->s_type = type;
853 strscpy(s->s_id, type->name, sizeof(s->s_id));
854 list_add_tail(&s->s_list, &super_blocks);
855 hlist_add_head(&s->s_instances, &type->fs_supers);
856 spin_unlock(&sb_lock);
857 get_filesystem(type);
858 shrinker_register(s->s_shrink);
859 return s;
860}
861EXPORT_SYMBOL(sget);
862
863void drop_super(struct super_block *sb)
864{
865 super_unlock_shared(sb);
866 put_super(sb);
867}
868
869EXPORT_SYMBOL(drop_super);
870
871void drop_super_exclusive(struct super_block *sb)
872{
873 super_unlock_excl(sb);
874 put_super(sb);
875}
876EXPORT_SYMBOL(drop_super_exclusive);
877
878static void __iterate_supers(void (*f)(struct super_block *))
879{
880 struct super_block *sb, *p = NULL;
881
882 spin_lock(&sb_lock);
883 list_for_each_entry(sb, &super_blocks, s_list) {
884 if (super_flags(sb, SB_DYING))
885 continue;
886 sb->s_count++;
887 spin_unlock(&sb_lock);
888
889 f(sb);
890
891 spin_lock(&sb_lock);
892 if (p)
893 __put_super(p);
894 p = sb;
895 }
896 if (p)
897 __put_super(p);
898 spin_unlock(&sb_lock);
899}
900/**
901 * iterate_supers - call function for all active superblocks
902 * @f: function to call
903 * @arg: argument to pass to it
904 *
905 * Scans the superblock list and calls given function, passing it
906 * locked superblock and given argument.
907 */
908void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
909{
910 struct super_block *sb, *p = NULL;
911
912 spin_lock(&sb_lock);
913 list_for_each_entry(sb, &super_blocks, s_list) {
914 bool locked;
915
916 sb->s_count++;
917 spin_unlock(&sb_lock);
918
919 locked = super_lock_shared(sb);
920 if (locked) {
921 if (sb->s_root)
922 f(sb, arg);
923 super_unlock_shared(sb);
924 }
925
926 spin_lock(&sb_lock);
927 if (p)
928 __put_super(p);
929 p = sb;
930 }
931 if (p)
932 __put_super(p);
933 spin_unlock(&sb_lock);
934}
935
936/**
937 * iterate_supers_type - call function for superblocks of given type
938 * @type: fs type
939 * @f: function to call
940 * @arg: argument to pass to it
941 *
942 * Scans the superblock list and calls given function, passing it
943 * locked superblock and given argument.
944 */
945void iterate_supers_type(struct file_system_type *type,
946 void (*f)(struct super_block *, void *), void *arg)
947{
948 struct super_block *sb, *p = NULL;
949
950 spin_lock(&sb_lock);
951 hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
952 bool locked;
953
954 sb->s_count++;
955 spin_unlock(&sb_lock);
956
957 locked = super_lock_shared(sb);
958 if (locked) {
959 if (sb->s_root)
960 f(sb, arg);
961 super_unlock_shared(sb);
962 }
963
964 spin_lock(&sb_lock);
965 if (p)
966 __put_super(p);
967 p = sb;
968 }
969 if (p)
970 __put_super(p);
971 spin_unlock(&sb_lock);
972}
973
974EXPORT_SYMBOL(iterate_supers_type);
975
976struct super_block *user_get_super(dev_t dev, bool excl)
977{
978 struct super_block *sb;
979
980 spin_lock(&sb_lock);
981 list_for_each_entry(sb, &super_blocks, s_list) {
982 if (sb->s_dev == dev) {
983 bool locked;
984
985 sb->s_count++;
986 spin_unlock(&sb_lock);
987 /* still alive? */
988 locked = super_lock(sb, excl);
989 if (locked) {
990 if (sb->s_root)
991 return sb;
992 super_unlock(sb, excl);
993 }
994 /* nope, got unmounted */
995 spin_lock(&sb_lock);
996 __put_super(sb);
997 break;
998 }
999 }
1000 spin_unlock(&sb_lock);
1001 return NULL;
1002}
1003
1004/**
1005 * reconfigure_super - asks filesystem to change superblock parameters
1006 * @fc: The superblock and configuration
1007 *
1008 * Alters the configuration parameters of a live superblock.
1009 */
1010int reconfigure_super(struct fs_context *fc)
1011{
1012 struct super_block *sb = fc->root->d_sb;
1013 int retval;
1014 bool remount_ro = false;
1015 bool remount_rw = false;
1016 bool force = fc->sb_flags & SB_FORCE;
1017
1018 if (fc->sb_flags_mask & ~MS_RMT_MASK)
1019 return -EINVAL;
1020 if (sb->s_writers.frozen != SB_UNFROZEN)
1021 return -EBUSY;
1022
1023 retval = security_sb_remount(sb, fc->security);
1024 if (retval)
1025 return retval;
1026
1027 if (fc->sb_flags_mask & SB_RDONLY) {
1028#ifdef CONFIG_BLOCK
1029 if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&
1030 bdev_read_only(sb->s_bdev))
1031 return -EACCES;
1032#endif
1033 remount_rw = !(fc->sb_flags & SB_RDONLY) && sb_rdonly(sb);
1034 remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
1035 }
1036
1037 if (remount_ro) {
1038 if (!hlist_empty(&sb->s_pins)) {
1039 super_unlock_excl(sb);
1040 group_pin_kill(&sb->s_pins);
1041 __super_lock_excl(sb);
1042 if (!sb->s_root)
1043 return 0;
1044 if (sb->s_writers.frozen != SB_UNFROZEN)
1045 return -EBUSY;
1046 remount_ro = !sb_rdonly(sb);
1047 }
1048 }
1049 shrink_dcache_sb(sb);
1050
1051 /* If we are reconfiguring to RDONLY and current sb is read/write,
1052 * make sure there are no files open for writing.
1053 */
1054 if (remount_ro) {
1055 if (force) {
1056 sb_start_ro_state_change(sb);
1057 } else {
1058 retval = sb_prepare_remount_readonly(sb);
1059 if (retval)
1060 return retval;
1061 }
1062 } else if (remount_rw) {
1063 /*
1064 * Protect filesystem's reconfigure code from writes from
1065 * userspace until reconfigure finishes.
1066 */
1067 sb_start_ro_state_change(sb);
1068 }
1069
1070 if (fc->ops->reconfigure) {
1071 retval = fc->ops->reconfigure(fc);
1072 if (retval) {
1073 if (!force)
1074 goto cancel_readonly;
1075 /* If forced remount, go ahead despite any errors */
1076 WARN(1, "forced remount of a %s fs returned %i\n",
1077 sb->s_type->name, retval);
1078 }
1079 }
1080
1081 WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
1082 (fc->sb_flags & fc->sb_flags_mask)));
1083 sb_end_ro_state_change(sb);
1084
1085 /*
1086 * Some filesystems modify their metadata via some other path than the
1087 * bdev buffer cache (eg. use a private mapping, or directories in
1088 * pagecache, etc). Also file data modifications go via their own
1089 * mappings. So If we try to mount readonly then copy the filesystem
1090 * from bdev, we could get stale data, so invalidate it to give a best
1091 * effort at coherency.
1092 */
1093 if (remount_ro && sb->s_bdev)
1094 invalidate_bdev(sb->s_bdev);
1095 return 0;
1096
1097cancel_readonly:
1098 sb_end_ro_state_change(sb);
1099 return retval;
1100}
1101
1102static void do_emergency_remount_callback(struct super_block *sb)
1103{
1104 bool locked = super_lock_excl(sb);
1105
1106 if (locked && sb->s_root && sb->s_bdev && !sb_rdonly(sb)) {
1107 struct fs_context *fc;
1108
1109 fc = fs_context_for_reconfigure(sb->s_root,
1110 SB_RDONLY | SB_FORCE, SB_RDONLY);
1111 if (!IS_ERR(fc)) {
1112 if (parse_monolithic_mount_data(fc, NULL) == 0)
1113 (void)reconfigure_super(fc);
1114 put_fs_context(fc);
1115 }
1116 }
1117 if (locked)
1118 super_unlock_excl(sb);
1119}
1120
1121static void do_emergency_remount(struct work_struct *work)
1122{
1123 __iterate_supers(do_emergency_remount_callback);
1124 kfree(work);
1125 printk("Emergency Remount complete\n");
1126}
1127
1128void emergency_remount(void)
1129{
1130 struct work_struct *work;
1131
1132 work = kmalloc(sizeof(*work), GFP_ATOMIC);
1133 if (work) {
1134 INIT_WORK(work, do_emergency_remount);
1135 schedule_work(work);
1136 }
1137}
1138
1139static void do_thaw_all_callback(struct super_block *sb)
1140{
1141 bool locked = super_lock_excl(sb);
1142
1143 if (locked && sb->s_root) {
1144 if (IS_ENABLED(CONFIG_BLOCK))
1145 while (sb->s_bdev && !bdev_thaw(sb->s_bdev))
1146 pr_warn("Emergency Thaw on %pg\n", sb->s_bdev);
1147 thaw_super_locked(sb, FREEZE_HOLDER_USERSPACE);
1148 return;
1149 }
1150 if (locked)
1151 super_unlock_excl(sb);
1152}
1153
1154static void do_thaw_all(struct work_struct *work)
1155{
1156 __iterate_supers(do_thaw_all_callback);
1157 kfree(work);
1158 printk(KERN_WARNING "Emergency Thaw complete\n");
1159}
1160
1161/**
1162 * emergency_thaw_all -- forcibly thaw every frozen filesystem
1163 *
1164 * Used for emergency unfreeze of all filesystems via SysRq
1165 */
1166void emergency_thaw_all(void)
1167{
1168 struct work_struct *work;
1169
1170 work = kmalloc(sizeof(*work), GFP_ATOMIC);
1171 if (work) {
1172 INIT_WORK(work, do_thaw_all);
1173 schedule_work(work);
1174 }
1175}
1176
1177static DEFINE_IDA(unnamed_dev_ida);
1178
1179/**
1180 * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1181 * @p: Pointer to a dev_t.
1182 *
1183 * Filesystems which don't use real block devices can call this function
1184 * to allocate a virtual block device.
1185 *
1186 * Context: Any context. Frequently called while holding sb_lock.
1187 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1188 * or -ENOMEM if memory allocation failed.
1189 */
1190int get_anon_bdev(dev_t *p)
1191{
1192 int dev;
1193
1194 /*
1195 * Many userspace utilities consider an FSID of 0 invalid.
1196 * Always return at least 1 from get_anon_bdev.
1197 */
1198 dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
1199 GFP_ATOMIC);
1200 if (dev == -ENOSPC)
1201 dev = -EMFILE;
1202 if (dev < 0)
1203 return dev;
1204
1205 *p = MKDEV(0, dev);
1206 return 0;
1207}
1208EXPORT_SYMBOL(get_anon_bdev);
1209
1210void free_anon_bdev(dev_t dev)
1211{
1212 ida_free(&unnamed_dev_ida, MINOR(dev));
1213}
1214EXPORT_SYMBOL(free_anon_bdev);
1215
1216int set_anon_super(struct super_block *s, void *data)
1217{
1218 return get_anon_bdev(&s->s_dev);
1219}
1220EXPORT_SYMBOL(set_anon_super);
1221
1222void kill_anon_super(struct super_block *sb)
1223{
1224 dev_t dev = sb->s_dev;
1225 generic_shutdown_super(sb);
1226 kill_super_notify(sb);
1227 free_anon_bdev(dev);
1228}
1229EXPORT_SYMBOL(kill_anon_super);
1230
1231void kill_litter_super(struct super_block *sb)
1232{
1233 if (sb->s_root)
1234 d_genocide(sb->s_root);
1235 kill_anon_super(sb);
1236}
1237EXPORT_SYMBOL(kill_litter_super);
1238
1239int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
1240{
1241 return set_anon_super(sb, NULL);
1242}
1243EXPORT_SYMBOL(set_anon_super_fc);
1244
1245static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
1246{
1247 return sb->s_fs_info == fc->s_fs_info;
1248}
1249
1250static int test_single_super(struct super_block *s, struct fs_context *fc)
1251{
1252 return 1;
1253}
1254
1255static int vfs_get_super(struct fs_context *fc,
1256 int (*test)(struct super_block *, struct fs_context *),
1257 int (*fill_super)(struct super_block *sb,
1258 struct fs_context *fc))
1259{
1260 struct super_block *sb;
1261 int err;
1262
1263 sb = sget_fc(fc, test, set_anon_super_fc);
1264 if (IS_ERR(sb))
1265 return PTR_ERR(sb);
1266
1267 if (!sb->s_root) {
1268 err = fill_super(sb, fc);
1269 if (err)
1270 goto error;
1271
1272 sb->s_flags |= SB_ACTIVE;
1273 }
1274
1275 fc->root = dget(sb->s_root);
1276 return 0;
1277
1278error:
1279 deactivate_locked_super(sb);
1280 return err;
1281}
1282
1283int get_tree_nodev(struct fs_context *fc,
1284 int (*fill_super)(struct super_block *sb,
1285 struct fs_context *fc))
1286{
1287 return vfs_get_super(fc, NULL, fill_super);
1288}
1289EXPORT_SYMBOL(get_tree_nodev);
1290
1291int get_tree_single(struct fs_context *fc,
1292 int (*fill_super)(struct super_block *sb,
1293 struct fs_context *fc))
1294{
1295 return vfs_get_super(fc, test_single_super, fill_super);
1296}
1297EXPORT_SYMBOL(get_tree_single);
1298
1299int get_tree_keyed(struct fs_context *fc,
1300 int (*fill_super)(struct super_block *sb,
1301 struct fs_context *fc),
1302 void *key)
1303{
1304 fc->s_fs_info = key;
1305 return vfs_get_super(fc, test_keyed_super, fill_super);
1306}
1307EXPORT_SYMBOL(get_tree_keyed);
1308
1309static int set_bdev_super(struct super_block *s, void *data)
1310{
1311 s->s_dev = *(dev_t *)data;
1312 return 0;
1313}
1314
1315static int super_s_dev_set(struct super_block *s, struct fs_context *fc)
1316{
1317 return set_bdev_super(s, fc->sget_key);
1318}
1319
1320static int super_s_dev_test(struct super_block *s, struct fs_context *fc)
1321{
1322 return !(s->s_iflags & SB_I_RETIRED) &&
1323 s->s_dev == *(dev_t *)fc->sget_key;
1324}
1325
1326/**
1327 * sget_dev - Find or create a superblock by device number
1328 * @fc: Filesystem context.
1329 * @dev: device number
1330 *
1331 * Find or create a superblock using the provided device number that
1332 * will be stored in fc->sget_key.
1333 *
1334 * If an extant superblock is matched, then that will be returned with
1335 * an elevated reference count that the caller must transfer or discard.
1336 *
1337 * If no match is made, a new superblock will be allocated and basic
1338 * initialisation will be performed (s_type, s_fs_info, s_id, s_dev will
1339 * be set). The superblock will be published and it will be returned in
1340 * a partially constructed state with SB_BORN and SB_ACTIVE as yet
1341 * unset.
1342 *
1343 * Return: an existing or newly created superblock on success, an error
1344 * pointer on failure.
1345 */
1346struct super_block *sget_dev(struct fs_context *fc, dev_t dev)
1347{
1348 fc->sget_key = &dev;
1349 return sget_fc(fc, super_s_dev_test, super_s_dev_set);
1350}
1351EXPORT_SYMBOL(sget_dev);
1352
1353#ifdef CONFIG_BLOCK
1354/*
1355 * Lock the superblock that is holder of the bdev. Returns the superblock
1356 * pointer if we successfully locked the superblock and it is alive. Otherwise
1357 * we return NULL and just unlock bdev->bd_holder_lock.
1358 *
1359 * The function must be called with bdev->bd_holder_lock and releases it.
1360 */
1361static struct super_block *bdev_super_lock(struct block_device *bdev, bool excl)
1362 __releases(&bdev->bd_holder_lock)
1363{
1364 struct super_block *sb = bdev->bd_holder;
1365 bool locked;
1366
1367 lockdep_assert_held(&bdev->bd_holder_lock);
1368 lockdep_assert_not_held(&sb->s_umount);
1369 lockdep_assert_not_held(&bdev->bd_disk->open_mutex);
1370
1371 /* Make sure sb doesn't go away from under us */
1372 spin_lock(&sb_lock);
1373 sb->s_count++;
1374 spin_unlock(&sb_lock);
1375
1376 mutex_unlock(&bdev->bd_holder_lock);
1377
1378 locked = super_lock(sb, excl);
1379
1380 /*
1381 * If the superblock wasn't already SB_DYING then we hold
1382 * s_umount and can safely drop our temporary reference.
1383 */
1384 put_super(sb);
1385
1386 if (!locked)
1387 return NULL;
1388
1389 if (!sb->s_root || !(sb->s_flags & SB_ACTIVE)) {
1390 super_unlock(sb, excl);
1391 return NULL;
1392 }
1393
1394 return sb;
1395}
1396
1397static void fs_bdev_mark_dead(struct block_device *bdev, bool surprise)
1398{
1399 struct super_block *sb;
1400
1401 sb = bdev_super_lock(bdev, false);
1402 if (!sb)
1403 return;
1404
1405 if (!surprise)
1406 sync_filesystem(sb);
1407 shrink_dcache_sb(sb);
1408 invalidate_inodes(sb);
1409 if (sb->s_op->shutdown)
1410 sb->s_op->shutdown(sb);
1411
1412 super_unlock_shared(sb);
1413}
1414
1415static void fs_bdev_sync(struct block_device *bdev)
1416{
1417 struct super_block *sb;
1418
1419 sb = bdev_super_lock(bdev, false);
1420 if (!sb)
1421 return;
1422
1423 sync_filesystem(sb);
1424 super_unlock_shared(sb);
1425}
1426
1427static struct super_block *get_bdev_super(struct block_device *bdev)
1428{
1429 bool active = false;
1430 struct super_block *sb;
1431
1432 sb = bdev_super_lock(bdev, true);
1433 if (sb) {
1434 active = atomic_inc_not_zero(&sb->s_active);
1435 super_unlock_excl(sb);
1436 }
1437 if (!active)
1438 return NULL;
1439 return sb;
1440}
1441
1442/**
1443 * fs_bdev_freeze - freeze owning filesystem of block device
1444 * @bdev: block device
1445 *
1446 * Freeze the filesystem that owns this block device if it is still
1447 * active.
1448 *
1449 * A filesystem that owns multiple block devices may be frozen from each
1450 * block device and won't be unfrozen until all block devices are
1451 * unfrozen. Each block device can only freeze the filesystem once as we
1452 * nest freezes for block devices in the block layer.
1453 *
1454 * Return: If the freeze was successful zero is returned. If the freeze
1455 * failed a negative error code is returned.
1456 */
1457static int fs_bdev_freeze(struct block_device *bdev)
1458{
1459 struct super_block *sb;
1460 int error = 0;
1461
1462 lockdep_assert_held(&bdev->bd_fsfreeze_mutex);
1463
1464 sb = get_bdev_super(bdev);
1465 if (!sb)
1466 return -EINVAL;
1467
1468 if (sb->s_op->freeze_super)
1469 error = sb->s_op->freeze_super(sb,
1470 FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);
1471 else
1472 error = freeze_super(sb,
1473 FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);
1474 if (!error)
1475 error = sync_blockdev(bdev);
1476 deactivate_super(sb);
1477 return error;
1478}
1479
1480/**
1481 * fs_bdev_thaw - thaw owning filesystem of block device
1482 * @bdev: block device
1483 *
1484 * Thaw the filesystem that owns this block device.
1485 *
1486 * A filesystem that owns multiple block devices may be frozen from each
1487 * block device and won't be unfrozen until all block devices are
1488 * unfrozen. Each block device can only freeze the filesystem once as we
1489 * nest freezes for block devices in the block layer.
1490 *
1491 * Return: If the thaw was successful zero is returned. If the thaw
1492 * failed a negative error code is returned. If this function
1493 * returns zero it doesn't mean that the filesystem is unfrozen
1494 * as it may have been frozen multiple times (kernel may hold a
1495 * freeze or might be frozen from other block devices).
1496 */
1497static int fs_bdev_thaw(struct block_device *bdev)
1498{
1499 struct super_block *sb;
1500 int error;
1501
1502 lockdep_assert_held(&bdev->bd_fsfreeze_mutex);
1503
1504 sb = get_bdev_super(bdev);
1505 if (WARN_ON_ONCE(!sb))
1506 return -EINVAL;
1507
1508 if (sb->s_op->thaw_super)
1509 error = sb->s_op->thaw_super(sb,
1510 FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);
1511 else
1512 error = thaw_super(sb,
1513 FREEZE_MAY_NEST | FREEZE_HOLDER_USERSPACE);
1514 deactivate_super(sb);
1515 return error;
1516}
1517
1518const struct blk_holder_ops fs_holder_ops = {
1519 .mark_dead = fs_bdev_mark_dead,
1520 .sync = fs_bdev_sync,
1521 .freeze = fs_bdev_freeze,
1522 .thaw = fs_bdev_thaw,
1523};
1524EXPORT_SYMBOL_GPL(fs_holder_ops);
1525
1526int setup_bdev_super(struct super_block *sb, int sb_flags,
1527 struct fs_context *fc)
1528{
1529 blk_mode_t mode = sb_open_mode(sb_flags);
1530 struct file *bdev_file;
1531 struct block_device *bdev;
1532
1533 bdev_file = bdev_file_open_by_dev(sb->s_dev, mode, sb, &fs_holder_ops);
1534 if (IS_ERR(bdev_file)) {
1535 if (fc)
1536 errorf(fc, "%s: Can't open blockdev", fc->source);
1537 return PTR_ERR(bdev_file);
1538 }
1539 bdev = file_bdev(bdev_file);
1540
1541 /*
1542 * This really should be in blkdev_get_by_dev, but right now can't due
1543 * to legacy issues that require us to allow opening a block device node
1544 * writable from userspace even for a read-only block device.
1545 */
1546 if ((mode & BLK_OPEN_WRITE) && bdev_read_only(bdev)) {
1547 bdev_fput(bdev_file);
1548 return -EACCES;
1549 }
1550
1551 /*
1552 * It is enough to check bdev was not frozen before we set
1553 * s_bdev as freezing will wait until SB_BORN is set.
1554 */
1555 if (atomic_read(&bdev->bd_fsfreeze_count) > 0) {
1556 if (fc)
1557 warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
1558 bdev_fput(bdev_file);
1559 return -EBUSY;
1560 }
1561 spin_lock(&sb_lock);
1562 sb->s_bdev_file = bdev_file;
1563 sb->s_bdev = bdev;
1564 sb->s_bdi = bdi_get(bdev->bd_disk->bdi);
1565 if (bdev_stable_writes(bdev))
1566 sb->s_iflags |= SB_I_STABLE_WRITES;
1567 spin_unlock(&sb_lock);
1568
1569 snprintf(sb->s_id, sizeof(sb->s_id), "%pg", bdev);
1570 shrinker_debugfs_rename(sb->s_shrink, "sb-%s:%s", sb->s_type->name,
1571 sb->s_id);
1572 sb_set_blocksize(sb, block_size(bdev));
1573 return 0;
1574}
1575EXPORT_SYMBOL_GPL(setup_bdev_super);
1576
1577/**
1578 * get_tree_bdev - Get a superblock based on a single block device
1579 * @fc: The filesystem context holding the parameters
1580 * @fill_super: Helper to initialise a new superblock
1581 */
1582int get_tree_bdev(struct fs_context *fc,
1583 int (*fill_super)(struct super_block *,
1584 struct fs_context *))
1585{
1586 struct super_block *s;
1587 int error = 0;
1588 dev_t dev;
1589
1590 if (!fc->source)
1591 return invalf(fc, "No source specified");
1592
1593 error = lookup_bdev(fc->source, &dev);
1594 if (error) {
1595 errorf(fc, "%s: Can't lookup blockdev", fc->source);
1596 return error;
1597 }
1598
1599 fc->sb_flags |= SB_NOSEC;
1600 s = sget_dev(fc, dev);
1601 if (IS_ERR(s))
1602 return PTR_ERR(s);
1603
1604 if (s->s_root) {
1605 /* Don't summarily change the RO/RW state. */
1606 if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
1607 warnf(fc, "%pg: Can't mount, would change RO state", s->s_bdev);
1608 deactivate_locked_super(s);
1609 return -EBUSY;
1610 }
1611 } else {
1612 error = setup_bdev_super(s, fc->sb_flags, fc);
1613 if (!error)
1614 error = fill_super(s, fc);
1615 if (error) {
1616 deactivate_locked_super(s);
1617 return error;
1618 }
1619 s->s_flags |= SB_ACTIVE;
1620 }
1621
1622 BUG_ON(fc->root);
1623 fc->root = dget(s->s_root);
1624 return 0;
1625}
1626EXPORT_SYMBOL(get_tree_bdev);
1627
1628static int test_bdev_super(struct super_block *s, void *data)
1629{
1630 return !(s->s_iflags & SB_I_RETIRED) && s->s_dev == *(dev_t *)data;
1631}
1632
1633struct dentry *mount_bdev(struct file_system_type *fs_type,
1634 int flags, const char *dev_name, void *data,
1635 int (*fill_super)(struct super_block *, void *, int))
1636{
1637 struct super_block *s;
1638 int error;
1639 dev_t dev;
1640
1641 error = lookup_bdev(dev_name, &dev);
1642 if (error)
1643 return ERR_PTR(error);
1644
1645 flags |= SB_NOSEC;
1646 s = sget(fs_type, test_bdev_super, set_bdev_super, flags, &dev);
1647 if (IS_ERR(s))
1648 return ERR_CAST(s);
1649
1650 if (s->s_root) {
1651 if ((flags ^ s->s_flags) & SB_RDONLY) {
1652 deactivate_locked_super(s);
1653 return ERR_PTR(-EBUSY);
1654 }
1655 } else {
1656 error = setup_bdev_super(s, flags, NULL);
1657 if (!error)
1658 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1659 if (error) {
1660 deactivate_locked_super(s);
1661 return ERR_PTR(error);
1662 }
1663
1664 s->s_flags |= SB_ACTIVE;
1665 }
1666
1667 return dget(s->s_root);
1668}
1669EXPORT_SYMBOL(mount_bdev);
1670
1671void kill_block_super(struct super_block *sb)
1672{
1673 struct block_device *bdev = sb->s_bdev;
1674
1675 generic_shutdown_super(sb);
1676 if (bdev) {
1677 sync_blockdev(bdev);
1678 bdev_fput(sb->s_bdev_file);
1679 }
1680}
1681
1682EXPORT_SYMBOL(kill_block_super);
1683#endif
1684
1685struct dentry *mount_nodev(struct file_system_type *fs_type,
1686 int flags, void *data,
1687 int (*fill_super)(struct super_block *, void *, int))
1688{
1689 int error;
1690 struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1691
1692 if (IS_ERR(s))
1693 return ERR_CAST(s);
1694
1695 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1696 if (error) {
1697 deactivate_locked_super(s);
1698 return ERR_PTR(error);
1699 }
1700 s->s_flags |= SB_ACTIVE;
1701 return dget(s->s_root);
1702}
1703EXPORT_SYMBOL(mount_nodev);
1704
1705int reconfigure_single(struct super_block *s,
1706 int flags, void *data)
1707{
1708 struct fs_context *fc;
1709 int ret;
1710
1711 /* The caller really need to be passing fc down into mount_single(),
1712 * then a chunk of this can be removed. [Bollocks -- AV]
1713 * Better yet, reconfiguration shouldn't happen, but rather the second
1714 * mount should be rejected if the parameters are not compatible.
1715 */
1716 fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
1717 if (IS_ERR(fc))
1718 return PTR_ERR(fc);
1719
1720 ret = parse_monolithic_mount_data(fc, data);
1721 if (ret < 0)
1722 goto out;
1723
1724 ret = reconfigure_super(fc);
1725out:
1726 put_fs_context(fc);
1727 return ret;
1728}
1729
1730static int compare_single(struct super_block *s, void *p)
1731{
1732 return 1;
1733}
1734
1735struct dentry *mount_single(struct file_system_type *fs_type,
1736 int flags, void *data,
1737 int (*fill_super)(struct super_block *, void *, int))
1738{
1739 struct super_block *s;
1740 int error;
1741
1742 s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1743 if (IS_ERR(s))
1744 return ERR_CAST(s);
1745 if (!s->s_root) {
1746 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1747 if (!error)
1748 s->s_flags |= SB_ACTIVE;
1749 } else {
1750 error = reconfigure_single(s, flags, data);
1751 }
1752 if (unlikely(error)) {
1753 deactivate_locked_super(s);
1754 return ERR_PTR(error);
1755 }
1756 return dget(s->s_root);
1757}
1758EXPORT_SYMBOL(mount_single);
1759
1760/**
1761 * vfs_get_tree - Get the mountable root
1762 * @fc: The superblock configuration context.
1763 *
1764 * The filesystem is invoked to get or create a superblock which can then later
1765 * be used for mounting. The filesystem places a pointer to the root to be
1766 * used for mounting in @fc->root.
1767 */
1768int vfs_get_tree(struct fs_context *fc)
1769{
1770 struct super_block *sb;
1771 int error;
1772
1773 if (fc->root)
1774 return -EBUSY;
1775
1776 /* Get the mountable root in fc->root, with a ref on the root and a ref
1777 * on the superblock.
1778 */
1779 error = fc->ops->get_tree(fc);
1780 if (error < 0)
1781 return error;
1782
1783 if (!fc->root) {
1784 pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1785 fc->fs_type->name);
1786 /* We don't know what the locking state of the superblock is -
1787 * if there is a superblock.
1788 */
1789 BUG();
1790 }
1791
1792 sb = fc->root->d_sb;
1793 WARN_ON(!sb->s_bdi);
1794
1795 /*
1796 * super_wake() contains a memory barrier which also care of
1797 * ordering for super_cache_count(). We place it before setting
1798 * SB_BORN as the data dependency between the two functions is
1799 * the superblock structure contents that we just set up, not
1800 * the SB_BORN flag.
1801 */
1802 super_wake(sb, SB_BORN);
1803
1804 error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
1805 if (unlikely(error)) {
1806 fc_drop_locked(fc);
1807 return error;
1808 }
1809
1810 /*
1811 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1812 * but s_maxbytes was an unsigned long long for many releases. Throw
1813 * this warning for a little while to try and catch filesystems that
1814 * violate this rule.
1815 */
1816 WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1817 "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);
1818
1819 return 0;
1820}
1821EXPORT_SYMBOL(vfs_get_tree);
1822
1823/*
1824 * Setup private BDI for given superblock. It gets automatically cleaned up
1825 * in generic_shutdown_super().
1826 */
1827int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
1828{
1829 struct backing_dev_info *bdi;
1830 int err;
1831 va_list args;
1832
1833 bdi = bdi_alloc(NUMA_NO_NODE);
1834 if (!bdi)
1835 return -ENOMEM;
1836
1837 va_start(args, fmt);
1838 err = bdi_register_va(bdi, fmt, args);
1839 va_end(args);
1840 if (err) {
1841 bdi_put(bdi);
1842 return err;
1843 }
1844 WARN_ON(sb->s_bdi != &noop_backing_dev_info);
1845 sb->s_bdi = bdi;
1846 sb->s_iflags |= SB_I_PERSB_BDI;
1847
1848 return 0;
1849}
1850EXPORT_SYMBOL(super_setup_bdi_name);
1851
1852/*
1853 * Setup private BDI for given superblock. I gets automatically cleaned up
1854 * in generic_shutdown_super().
1855 */
1856int super_setup_bdi(struct super_block *sb)
1857{
1858 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
1859
1860 return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
1861 atomic_long_inc_return(&bdi_seq));
1862}
1863EXPORT_SYMBOL(super_setup_bdi);
1864
1865/**
1866 * sb_wait_write - wait until all writers to given file system finish
1867 * @sb: the super for which we wait
1868 * @level: type of writers we wait for (normal vs page fault)
1869 *
1870 * This function waits until there are no writers of given type to given file
1871 * system.
1872 */
1873static void sb_wait_write(struct super_block *sb, int level)
1874{
1875 percpu_down_write(sb->s_writers.rw_sem + level-1);
1876}
1877
1878/*
1879 * We are going to return to userspace and forget about these locks, the
1880 * ownership goes to the caller of thaw_super() which does unlock().
1881 */
1882static void lockdep_sb_freeze_release(struct super_block *sb)
1883{
1884 int level;
1885
1886 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1887 percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1888}
1889
1890/*
1891 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1892 */
1893static void lockdep_sb_freeze_acquire(struct super_block *sb)
1894{
1895 int level;
1896
1897 for (level = 0; level < SB_FREEZE_LEVELS; ++level)
1898 percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1899}
1900
1901static void sb_freeze_unlock(struct super_block *sb, int level)
1902{
1903 for (level--; level >= 0; level--)
1904 percpu_up_write(sb->s_writers.rw_sem + level);
1905}
1906
1907static int wait_for_partially_frozen(struct super_block *sb)
1908{
1909 int ret = 0;
1910
1911 do {
1912 unsigned short old = sb->s_writers.frozen;
1913
1914 up_write(&sb->s_umount);
1915 ret = wait_var_event_killable(&sb->s_writers.frozen,
1916 sb->s_writers.frozen != old);
1917 down_write(&sb->s_umount);
1918 } while (ret == 0 &&
1919 sb->s_writers.frozen != SB_UNFROZEN &&
1920 sb->s_writers.frozen != SB_FREEZE_COMPLETE);
1921
1922 return ret;
1923}
1924
1925#define FREEZE_HOLDERS (FREEZE_HOLDER_KERNEL | FREEZE_HOLDER_USERSPACE)
1926#define FREEZE_FLAGS (FREEZE_HOLDERS | FREEZE_MAY_NEST)
1927
1928static inline int freeze_inc(struct super_block *sb, enum freeze_holder who)
1929{
1930 WARN_ON_ONCE((who & ~FREEZE_FLAGS));
1931 WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
1932
1933 if (who & FREEZE_HOLDER_KERNEL)
1934 ++sb->s_writers.freeze_kcount;
1935 if (who & FREEZE_HOLDER_USERSPACE)
1936 ++sb->s_writers.freeze_ucount;
1937 return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount;
1938}
1939
1940static inline int freeze_dec(struct super_block *sb, enum freeze_holder who)
1941{
1942 WARN_ON_ONCE((who & ~FREEZE_FLAGS));
1943 WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
1944
1945 if ((who & FREEZE_HOLDER_KERNEL) && sb->s_writers.freeze_kcount)
1946 --sb->s_writers.freeze_kcount;
1947 if ((who & FREEZE_HOLDER_USERSPACE) && sb->s_writers.freeze_ucount)
1948 --sb->s_writers.freeze_ucount;
1949 return sb->s_writers.freeze_kcount + sb->s_writers.freeze_ucount;
1950}
1951
1952static inline bool may_freeze(struct super_block *sb, enum freeze_holder who)
1953{
1954 WARN_ON_ONCE((who & ~FREEZE_FLAGS));
1955 WARN_ON_ONCE(hweight32(who & FREEZE_HOLDERS) > 1);
1956
1957 if (who & FREEZE_HOLDER_KERNEL)
1958 return (who & FREEZE_MAY_NEST) ||
1959 sb->s_writers.freeze_kcount == 0;
1960 if (who & FREEZE_HOLDER_USERSPACE)
1961 return (who & FREEZE_MAY_NEST) ||
1962 sb->s_writers.freeze_ucount == 0;
1963 return false;
1964}
1965
1966/**
1967 * freeze_super - lock the filesystem and force it into a consistent state
1968 * @sb: the super to lock
1969 * @who: context that wants to freeze
1970 *
1971 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1972 * freeze_fs. Subsequent calls to this without first thawing the fs may return
1973 * -EBUSY.
1974 *
1975 * @who should be:
1976 * * %FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs;
1977 * * %FREEZE_HOLDER_KERNEL if the kernel wants to freeze the fs.
1978 * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed.
1979 *
1980 * The @who argument distinguishes between the kernel and userspace trying to
1981 * freeze the filesystem. Although there cannot be multiple kernel freezes or
1982 * multiple userspace freezes in effect at any given time, the kernel and
1983 * userspace can both hold a filesystem frozen. The filesystem remains frozen
1984 * until there are no kernel or userspace freezes in effect.
1985 *
1986 * A filesystem may hold multiple devices and thus a filesystems may be
1987 * frozen through the block layer via multiple block devices. In this
1988 * case the request is marked as being allowed to nest by passing
1989 * FREEZE_MAY_NEST. The filesystem remains frozen until all block
1990 * devices are unfrozen. If multiple freezes are attempted without
1991 * FREEZE_MAY_NEST -EBUSY will be returned.
1992 *
1993 * During this function, sb->s_writers.frozen goes through these values:
1994 *
1995 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1996 *
1997 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1998 * writes should be blocked, though page faults are still allowed. We wait for
1999 * all writes to complete and then proceed to the next stage.
2000 *
2001 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
2002 * but internal fs threads can still modify the filesystem (although they
2003 * should not dirty new pages or inodes), writeback can run etc. After waiting
2004 * for all running page faults we sync the filesystem which will clean all
2005 * dirty pages and inodes (no new dirty pages or inodes can be created when
2006 * sync is running).
2007 *
2008 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
2009 * modification are blocked (e.g. XFS preallocation truncation on inode
2010 * reclaim). This is usually implemented by blocking new transactions for
2011 * filesystems that have them and need this additional guard. After all
2012 * internal writers are finished we call ->freeze_fs() to finish filesystem
2013 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
2014 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
2015 *
2016 * sb->s_writers.frozen is protected by sb->s_umount.
2017 *
2018 * Return: If the freeze was successful zero is returned. If the freeze
2019 * failed a negative error code is returned.
2020 */
2021int freeze_super(struct super_block *sb, enum freeze_holder who)
2022{
2023 int ret;
2024
2025 if (!super_lock_excl(sb)) {
2026 WARN_ON_ONCE("Dying superblock while freezing!");
2027 return -EINVAL;
2028 }
2029 atomic_inc(&sb->s_active);
2030
2031retry:
2032 if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) {
2033 if (may_freeze(sb, who))
2034 ret = !!WARN_ON_ONCE(freeze_inc(sb, who) == 1);
2035 else
2036 ret = -EBUSY;
2037 /* All freezers share a single active reference. */
2038 deactivate_locked_super(sb);
2039 return ret;
2040 }
2041
2042 if (sb->s_writers.frozen != SB_UNFROZEN) {
2043 ret = wait_for_partially_frozen(sb);
2044 if (ret) {
2045 deactivate_locked_super(sb);
2046 return ret;
2047 }
2048
2049 goto retry;
2050 }
2051
2052 if (sb_rdonly(sb)) {
2053 /* Nothing to do really... */
2054 WARN_ON_ONCE(freeze_inc(sb, who) > 1);
2055 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
2056 wake_up_var(&sb->s_writers.frozen);
2057 super_unlock_excl(sb);
2058 return 0;
2059 }
2060
2061 sb->s_writers.frozen = SB_FREEZE_WRITE;
2062 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
2063 super_unlock_excl(sb);
2064 sb_wait_write(sb, SB_FREEZE_WRITE);
2065 __super_lock_excl(sb);
2066
2067 /* Now we go and block page faults... */
2068 sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
2069 sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
2070
2071 /* All writers are done so after syncing there won't be dirty data */
2072 ret = sync_filesystem(sb);
2073 if (ret) {
2074 sb->s_writers.frozen = SB_UNFROZEN;
2075 sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT);
2076 wake_up_var(&sb->s_writers.frozen);
2077 deactivate_locked_super(sb);
2078 return ret;
2079 }
2080
2081 /* Now wait for internal filesystem counter */
2082 sb->s_writers.frozen = SB_FREEZE_FS;
2083 sb_wait_write(sb, SB_FREEZE_FS);
2084
2085 if (sb->s_op->freeze_fs) {
2086 ret = sb->s_op->freeze_fs(sb);
2087 if (ret) {
2088 printk(KERN_ERR
2089 "VFS:Filesystem freeze failed\n");
2090 sb->s_writers.frozen = SB_UNFROZEN;
2091 sb_freeze_unlock(sb, SB_FREEZE_FS);
2092 wake_up_var(&sb->s_writers.frozen);
2093 deactivate_locked_super(sb);
2094 return ret;
2095 }
2096 }
2097 /*
2098 * For debugging purposes so that fs can warn if it sees write activity
2099 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
2100 */
2101 WARN_ON_ONCE(freeze_inc(sb, who) > 1);
2102 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
2103 wake_up_var(&sb->s_writers.frozen);
2104 lockdep_sb_freeze_release(sb);
2105 super_unlock_excl(sb);
2106 return 0;
2107}
2108EXPORT_SYMBOL(freeze_super);
2109
2110/*
2111 * Undoes the effect of a freeze_super_locked call. If the filesystem is
2112 * frozen both by userspace and the kernel, a thaw call from either source
2113 * removes that state without releasing the other state or unlocking the
2114 * filesystem.
2115 */
2116static int thaw_super_locked(struct super_block *sb, enum freeze_holder who)
2117{
2118 int error = -EINVAL;
2119
2120 if (sb->s_writers.frozen != SB_FREEZE_COMPLETE)
2121 goto out_unlock;
2122
2123 /*
2124 * All freezers share a single active reference.
2125 * So just unlock in case there are any left.
2126 */
2127 if (freeze_dec(sb, who))
2128 goto out_unlock;
2129
2130 if (sb_rdonly(sb)) {
2131 sb->s_writers.frozen = SB_UNFROZEN;
2132 wake_up_var(&sb->s_writers.frozen);
2133 goto out_deactivate;
2134 }
2135
2136 lockdep_sb_freeze_acquire(sb);
2137
2138 if (sb->s_op->unfreeze_fs) {
2139 error = sb->s_op->unfreeze_fs(sb);
2140 if (error) {
2141 pr_err("VFS: Filesystem thaw failed\n");
2142 freeze_inc(sb, who);
2143 lockdep_sb_freeze_release(sb);
2144 goto out_unlock;
2145 }
2146 }
2147
2148 sb->s_writers.frozen = SB_UNFROZEN;
2149 wake_up_var(&sb->s_writers.frozen);
2150 sb_freeze_unlock(sb, SB_FREEZE_FS);
2151out_deactivate:
2152 deactivate_locked_super(sb);
2153 return 0;
2154
2155out_unlock:
2156 super_unlock_excl(sb);
2157 return error;
2158}
2159
2160/**
2161 * thaw_super -- unlock filesystem
2162 * @sb: the super to thaw
2163 * @who: context that wants to freeze
2164 *
2165 * Unlocks the filesystem and marks it writeable again after freeze_super()
2166 * if there are no remaining freezes on the filesystem.
2167 *
2168 * @who should be:
2169 * * %FREEZE_HOLDER_USERSPACE if userspace wants to thaw the fs;
2170 * * %FREEZE_HOLDER_KERNEL if the kernel wants to thaw the fs.
2171 * * %FREEZE_MAY_NEST whether nesting freeze and thaw requests is allowed
2172 *
2173 * A filesystem may hold multiple devices and thus a filesystems may
2174 * have been frozen through the block layer via multiple block devices.
2175 * The filesystem remains frozen until all block devices are unfrozen.
2176 */
2177int thaw_super(struct super_block *sb, enum freeze_holder who)
2178{
2179 if (!super_lock_excl(sb)) {
2180 WARN_ON_ONCE("Dying superblock while thawing!");
2181 return -EINVAL;
2182 }
2183 return thaw_super_locked(sb, who);
2184}
2185EXPORT_SYMBOL(thaw_super);
2186
2187/*
2188 * Create workqueue for deferred direct IO completions. We allocate the
2189 * workqueue when it's first needed. This avoids creating workqueue for
2190 * filesystems that don't need it and also allows us to create the workqueue
2191 * late enough so the we can include s_id in the name of the workqueue.
2192 */
2193int sb_init_dio_done_wq(struct super_block *sb)
2194{
2195 struct workqueue_struct *old;
2196 struct workqueue_struct *wq = alloc_workqueue("dio/%s",
2197 WQ_MEM_RECLAIM, 0,
2198 sb->s_id);
2199 if (!wq)
2200 return -ENOMEM;
2201 /*
2202 * This has to be atomic as more DIOs can race to create the workqueue
2203 */
2204 old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
2205 /* Someone created workqueue before us? Free ours... */
2206 if (old)
2207 destroy_workqueue(wq);
2208 return 0;
2209}
2210EXPORT_SYMBOL_GPL(sb_init_dio_done_wq);