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