Loading...
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 */
310void 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 security_sb_delete(sb);
458
459 if (sb->s_dio_done_wq) {
460 destroy_workqueue(sb->s_dio_done_wq);
461 sb->s_dio_done_wq = NULL;
462 }
463
464 if (sop->put_super)
465 sop->put_super(sb);
466
467 if (!list_empty(&sb->s_inodes)) {
468 printk("VFS: Busy inodes after unmount of %s. "
469 "Self-destruct in 5 seconds. Have a nice day...\n",
470 sb->s_id);
471 }
472 }
473 spin_lock(&sb_lock);
474 /* should be initialized for __put_super_and_need_restart() */
475 hlist_del_init(&sb->s_instances);
476 spin_unlock(&sb_lock);
477 up_write(&sb->s_umount);
478 if (sb->s_bdi != &noop_backing_dev_info) {
479 bdi_put(sb->s_bdi);
480 sb->s_bdi = &noop_backing_dev_info;
481 }
482}
483
484EXPORT_SYMBOL(generic_shutdown_super);
485
486bool mount_capable(struct fs_context *fc)
487{
488 if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
489 return capable(CAP_SYS_ADMIN);
490 else
491 return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
492}
493
494/**
495 * sget_fc - Find or create a superblock
496 * @fc: Filesystem context.
497 * @test: Comparison callback
498 * @set: Setup callback
499 *
500 * Find or create a superblock using the parameters stored in the filesystem
501 * context and the two callback functions.
502 *
503 * If an extant superblock is matched, then that will be returned with an
504 * elevated reference count that the caller must transfer or discard.
505 *
506 * If no match is made, a new superblock will be allocated and basic
507 * initialisation will be performed (s_type, s_fs_info and s_id will be set and
508 * the set() callback will be invoked), the superblock will be published and it
509 * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
510 * as yet unset.
511 */
512struct super_block *sget_fc(struct fs_context *fc,
513 int (*test)(struct super_block *, struct fs_context *),
514 int (*set)(struct super_block *, struct fs_context *))
515{
516 struct super_block *s = NULL;
517 struct super_block *old;
518 struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
519 int err;
520
521retry:
522 spin_lock(&sb_lock);
523 if (test) {
524 hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
525 if (test(old, fc))
526 goto share_extant_sb;
527 }
528 }
529 if (!s) {
530 spin_unlock(&sb_lock);
531 s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
532 if (!s)
533 return ERR_PTR(-ENOMEM);
534 goto retry;
535 }
536
537 s->s_fs_info = fc->s_fs_info;
538 err = set(s, fc);
539 if (err) {
540 s->s_fs_info = NULL;
541 spin_unlock(&sb_lock);
542 destroy_unused_super(s);
543 return ERR_PTR(err);
544 }
545 fc->s_fs_info = NULL;
546 s->s_type = fc->fs_type;
547 s->s_iflags |= fc->s_iflags;
548 strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
549 list_add_tail(&s->s_list, &super_blocks);
550 hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
551 spin_unlock(&sb_lock);
552 get_filesystem(s->s_type);
553 register_shrinker_prepared(&s->s_shrink);
554 return s;
555
556share_extant_sb:
557 if (user_ns != old->s_user_ns) {
558 spin_unlock(&sb_lock);
559 destroy_unused_super(s);
560 return ERR_PTR(-EBUSY);
561 }
562 if (!grab_super(old))
563 goto retry;
564 destroy_unused_super(s);
565 return old;
566}
567EXPORT_SYMBOL(sget_fc);
568
569/**
570 * sget - find or create a superblock
571 * @type: filesystem type superblock should belong to
572 * @test: comparison callback
573 * @set: setup callback
574 * @flags: mount flags
575 * @data: argument to each of them
576 */
577struct super_block *sget(struct file_system_type *type,
578 int (*test)(struct super_block *,void *),
579 int (*set)(struct super_block *,void *),
580 int flags,
581 void *data)
582{
583 struct user_namespace *user_ns = current_user_ns();
584 struct super_block *s = NULL;
585 struct super_block *old;
586 int err;
587
588 /* We don't yet pass the user namespace of the parent
589 * mount through to here so always use &init_user_ns
590 * until that changes.
591 */
592 if (flags & SB_SUBMOUNT)
593 user_ns = &init_user_ns;
594
595retry:
596 spin_lock(&sb_lock);
597 if (test) {
598 hlist_for_each_entry(old, &type->fs_supers, s_instances) {
599 if (!test(old, data))
600 continue;
601 if (user_ns != old->s_user_ns) {
602 spin_unlock(&sb_lock);
603 destroy_unused_super(s);
604 return ERR_PTR(-EBUSY);
605 }
606 if (!grab_super(old))
607 goto retry;
608 destroy_unused_super(s);
609 return old;
610 }
611 }
612 if (!s) {
613 spin_unlock(&sb_lock);
614 s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
615 if (!s)
616 return ERR_PTR(-ENOMEM);
617 goto retry;
618 }
619
620 err = set(s, data);
621 if (err) {
622 spin_unlock(&sb_lock);
623 destroy_unused_super(s);
624 return ERR_PTR(err);
625 }
626 s->s_type = type;
627 strlcpy(s->s_id, type->name, sizeof(s->s_id));
628 list_add_tail(&s->s_list, &super_blocks);
629 hlist_add_head(&s->s_instances, &type->fs_supers);
630 spin_unlock(&sb_lock);
631 get_filesystem(type);
632 register_shrinker_prepared(&s->s_shrink);
633 return s;
634}
635EXPORT_SYMBOL(sget);
636
637void drop_super(struct super_block *sb)
638{
639 up_read(&sb->s_umount);
640 put_super(sb);
641}
642
643EXPORT_SYMBOL(drop_super);
644
645void drop_super_exclusive(struct super_block *sb)
646{
647 up_write(&sb->s_umount);
648 put_super(sb);
649}
650EXPORT_SYMBOL(drop_super_exclusive);
651
652static void __iterate_supers(void (*f)(struct super_block *))
653{
654 struct super_block *sb, *p = NULL;
655
656 spin_lock(&sb_lock);
657 list_for_each_entry(sb, &super_blocks, s_list) {
658 if (hlist_unhashed(&sb->s_instances))
659 continue;
660 sb->s_count++;
661 spin_unlock(&sb_lock);
662
663 f(sb);
664
665 spin_lock(&sb_lock);
666 if (p)
667 __put_super(p);
668 p = sb;
669 }
670 if (p)
671 __put_super(p);
672 spin_unlock(&sb_lock);
673}
674/**
675 * iterate_supers - call function for all active superblocks
676 * @f: function to call
677 * @arg: argument to pass to it
678 *
679 * Scans the superblock list and calls given function, passing it
680 * locked superblock and given argument.
681 */
682void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
683{
684 struct super_block *sb, *p = NULL;
685
686 spin_lock(&sb_lock);
687 list_for_each_entry(sb, &super_blocks, s_list) {
688 if (hlist_unhashed(&sb->s_instances))
689 continue;
690 sb->s_count++;
691 spin_unlock(&sb_lock);
692
693 down_read(&sb->s_umount);
694 if (sb->s_root && (sb->s_flags & SB_BORN))
695 f(sb, arg);
696 up_read(&sb->s_umount);
697
698 spin_lock(&sb_lock);
699 if (p)
700 __put_super(p);
701 p = sb;
702 }
703 if (p)
704 __put_super(p);
705 spin_unlock(&sb_lock);
706}
707
708/**
709 * iterate_supers_type - call function for superblocks of given type
710 * @type: fs type
711 * @f: function to call
712 * @arg: argument to pass to it
713 *
714 * Scans the superblock list and calls given function, passing it
715 * locked superblock and given argument.
716 */
717void iterate_supers_type(struct file_system_type *type,
718 void (*f)(struct super_block *, void *), void *arg)
719{
720 struct super_block *sb, *p = NULL;
721
722 spin_lock(&sb_lock);
723 hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
724 sb->s_count++;
725 spin_unlock(&sb_lock);
726
727 down_read(&sb->s_umount);
728 if (sb->s_root && (sb->s_flags & SB_BORN))
729 f(sb, arg);
730 up_read(&sb->s_umount);
731
732 spin_lock(&sb_lock);
733 if (p)
734 __put_super(p);
735 p = sb;
736 }
737 if (p)
738 __put_super(p);
739 spin_unlock(&sb_lock);
740}
741
742EXPORT_SYMBOL(iterate_supers_type);
743
744/**
745 * get_super - get the superblock of a device
746 * @bdev: device to get the superblock for
747 *
748 * Scans the superblock list and finds the superblock of the file system
749 * mounted on the device given. %NULL is returned if no match is found.
750 */
751struct super_block *get_super(struct block_device *bdev)
752{
753 struct super_block *sb;
754
755 if (!bdev)
756 return NULL;
757
758 spin_lock(&sb_lock);
759rescan:
760 list_for_each_entry(sb, &super_blocks, s_list) {
761 if (hlist_unhashed(&sb->s_instances))
762 continue;
763 if (sb->s_bdev == bdev) {
764 sb->s_count++;
765 spin_unlock(&sb_lock);
766 down_read(&sb->s_umount);
767 /* still alive? */
768 if (sb->s_root && (sb->s_flags & SB_BORN))
769 return sb;
770 up_read(&sb->s_umount);
771 /* nope, got unmounted */
772 spin_lock(&sb_lock);
773 __put_super(sb);
774 goto rescan;
775 }
776 }
777 spin_unlock(&sb_lock);
778 return NULL;
779}
780
781/**
782 * get_active_super - get an active reference to the superblock of a device
783 * @bdev: device to get the superblock for
784 *
785 * Scans the superblock list and finds the superblock of the file system
786 * mounted on the device given. Returns the superblock with an active
787 * reference or %NULL if none was found.
788 */
789struct super_block *get_active_super(struct block_device *bdev)
790{
791 struct super_block *sb;
792
793 if (!bdev)
794 return NULL;
795
796restart:
797 spin_lock(&sb_lock);
798 list_for_each_entry(sb, &super_blocks, s_list) {
799 if (hlist_unhashed(&sb->s_instances))
800 continue;
801 if (sb->s_bdev == bdev) {
802 if (!grab_super(sb))
803 goto restart;
804 up_write(&sb->s_umount);
805 return sb;
806 }
807 }
808 spin_unlock(&sb_lock);
809 return NULL;
810}
811
812struct super_block *user_get_super(dev_t dev, bool excl)
813{
814 struct super_block *sb;
815
816 spin_lock(&sb_lock);
817rescan:
818 list_for_each_entry(sb, &super_blocks, s_list) {
819 if (hlist_unhashed(&sb->s_instances))
820 continue;
821 if (sb->s_dev == dev) {
822 sb->s_count++;
823 spin_unlock(&sb_lock);
824 if (excl)
825 down_write(&sb->s_umount);
826 else
827 down_read(&sb->s_umount);
828 /* still alive? */
829 if (sb->s_root && (sb->s_flags & SB_BORN))
830 return sb;
831 if (excl)
832 up_write(&sb->s_umount);
833 else
834 up_read(&sb->s_umount);
835 /* nope, got unmounted */
836 spin_lock(&sb_lock);
837 __put_super(sb);
838 goto rescan;
839 }
840 }
841 spin_unlock(&sb_lock);
842 return NULL;
843}
844
845/**
846 * reconfigure_super - asks filesystem to change superblock parameters
847 * @fc: The superblock and configuration
848 *
849 * Alters the configuration parameters of a live superblock.
850 */
851int reconfigure_super(struct fs_context *fc)
852{
853 struct super_block *sb = fc->root->d_sb;
854 int retval;
855 bool remount_ro = false;
856 bool force = fc->sb_flags & SB_FORCE;
857
858 if (fc->sb_flags_mask & ~MS_RMT_MASK)
859 return -EINVAL;
860 if (sb->s_writers.frozen != SB_UNFROZEN)
861 return -EBUSY;
862
863 retval = security_sb_remount(sb, fc->security);
864 if (retval)
865 return retval;
866
867 if (fc->sb_flags_mask & SB_RDONLY) {
868#ifdef CONFIG_BLOCK
869 if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&
870 bdev_read_only(sb->s_bdev))
871 return -EACCES;
872#endif
873
874 remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
875 }
876
877 if (remount_ro) {
878 if (!hlist_empty(&sb->s_pins)) {
879 up_write(&sb->s_umount);
880 group_pin_kill(&sb->s_pins);
881 down_write(&sb->s_umount);
882 if (!sb->s_root)
883 return 0;
884 if (sb->s_writers.frozen != SB_UNFROZEN)
885 return -EBUSY;
886 remount_ro = !sb_rdonly(sb);
887 }
888 }
889 shrink_dcache_sb(sb);
890
891 /* If we are reconfiguring to RDONLY and current sb is read/write,
892 * make sure there are no files open for writing.
893 */
894 if (remount_ro) {
895 if (force) {
896 sb->s_readonly_remount = 1;
897 smp_wmb();
898 } else {
899 retval = sb_prepare_remount_readonly(sb);
900 if (retval)
901 return retval;
902 }
903 }
904
905 if (fc->ops->reconfigure) {
906 retval = fc->ops->reconfigure(fc);
907 if (retval) {
908 if (!force)
909 goto cancel_readonly;
910 /* If forced remount, go ahead despite any errors */
911 WARN(1, "forced remount of a %s fs returned %i\n",
912 sb->s_type->name, retval);
913 }
914 }
915
916 WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
917 (fc->sb_flags & fc->sb_flags_mask)));
918 /* Needs to be ordered wrt mnt_is_readonly() */
919 smp_wmb();
920 sb->s_readonly_remount = 0;
921
922 /*
923 * Some filesystems modify their metadata via some other path than the
924 * bdev buffer cache (eg. use a private mapping, or directories in
925 * pagecache, etc). Also file data modifications go via their own
926 * mappings. So If we try to mount readonly then copy the filesystem
927 * from bdev, we could get stale data, so invalidate it to give a best
928 * effort at coherency.
929 */
930 if (remount_ro && sb->s_bdev)
931 invalidate_bdev(sb->s_bdev);
932 return 0;
933
934cancel_readonly:
935 sb->s_readonly_remount = 0;
936 return retval;
937}
938
939static void do_emergency_remount_callback(struct super_block *sb)
940{
941 down_write(&sb->s_umount);
942 if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
943 !sb_rdonly(sb)) {
944 struct fs_context *fc;
945
946 fc = fs_context_for_reconfigure(sb->s_root,
947 SB_RDONLY | SB_FORCE, SB_RDONLY);
948 if (!IS_ERR(fc)) {
949 if (parse_monolithic_mount_data(fc, NULL) == 0)
950 (void)reconfigure_super(fc);
951 put_fs_context(fc);
952 }
953 }
954 up_write(&sb->s_umount);
955}
956
957static void do_emergency_remount(struct work_struct *work)
958{
959 __iterate_supers(do_emergency_remount_callback);
960 kfree(work);
961 printk("Emergency Remount complete\n");
962}
963
964void emergency_remount(void)
965{
966 struct work_struct *work;
967
968 work = kmalloc(sizeof(*work), GFP_ATOMIC);
969 if (work) {
970 INIT_WORK(work, do_emergency_remount);
971 schedule_work(work);
972 }
973}
974
975static void do_thaw_all_callback(struct super_block *sb)
976{
977 down_write(&sb->s_umount);
978 if (sb->s_root && sb->s_flags & SB_BORN) {
979 emergency_thaw_bdev(sb);
980 thaw_super_locked(sb);
981 } else {
982 up_write(&sb->s_umount);
983 }
984}
985
986static void do_thaw_all(struct work_struct *work)
987{
988 __iterate_supers(do_thaw_all_callback);
989 kfree(work);
990 printk(KERN_WARNING "Emergency Thaw complete\n");
991}
992
993/**
994 * emergency_thaw_all -- forcibly thaw every frozen filesystem
995 *
996 * Used for emergency unfreeze of all filesystems via SysRq
997 */
998void emergency_thaw_all(void)
999{
1000 struct work_struct *work;
1001
1002 work = kmalloc(sizeof(*work), GFP_ATOMIC);
1003 if (work) {
1004 INIT_WORK(work, do_thaw_all);
1005 schedule_work(work);
1006 }
1007}
1008
1009static DEFINE_IDA(unnamed_dev_ida);
1010
1011/**
1012 * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1013 * @p: Pointer to a dev_t.
1014 *
1015 * Filesystems which don't use real block devices can call this function
1016 * to allocate a virtual block device.
1017 *
1018 * Context: Any context. Frequently called while holding sb_lock.
1019 * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1020 * or -ENOMEM if memory allocation failed.
1021 */
1022int get_anon_bdev(dev_t *p)
1023{
1024 int dev;
1025
1026 /*
1027 * Many userspace utilities consider an FSID of 0 invalid.
1028 * Always return at least 1 from get_anon_bdev.
1029 */
1030 dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
1031 GFP_ATOMIC);
1032 if (dev == -ENOSPC)
1033 dev = -EMFILE;
1034 if (dev < 0)
1035 return dev;
1036
1037 *p = MKDEV(0, dev);
1038 return 0;
1039}
1040EXPORT_SYMBOL(get_anon_bdev);
1041
1042void free_anon_bdev(dev_t dev)
1043{
1044 ida_free(&unnamed_dev_ida, MINOR(dev));
1045}
1046EXPORT_SYMBOL(free_anon_bdev);
1047
1048int set_anon_super(struct super_block *s, void *data)
1049{
1050 return get_anon_bdev(&s->s_dev);
1051}
1052EXPORT_SYMBOL(set_anon_super);
1053
1054void kill_anon_super(struct super_block *sb)
1055{
1056 dev_t dev = sb->s_dev;
1057 generic_shutdown_super(sb);
1058 free_anon_bdev(dev);
1059}
1060EXPORT_SYMBOL(kill_anon_super);
1061
1062void kill_litter_super(struct super_block *sb)
1063{
1064 if (sb->s_root)
1065 d_genocide(sb->s_root);
1066 kill_anon_super(sb);
1067}
1068EXPORT_SYMBOL(kill_litter_super);
1069
1070int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
1071{
1072 return set_anon_super(sb, NULL);
1073}
1074EXPORT_SYMBOL(set_anon_super_fc);
1075
1076static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
1077{
1078 return sb->s_fs_info == fc->s_fs_info;
1079}
1080
1081static int test_single_super(struct super_block *s, struct fs_context *fc)
1082{
1083 return 1;
1084}
1085
1086/**
1087 * vfs_get_super - Get a superblock with a search key set in s_fs_info.
1088 * @fc: The filesystem context holding the parameters
1089 * @keying: How to distinguish superblocks
1090 * @fill_super: Helper to initialise a new superblock
1091 *
1092 * Search for a superblock and create a new one if not found. The search
1093 * criterion is controlled by @keying. If the search fails, a new superblock
1094 * is created and @fill_super() is called to initialise it.
1095 *
1096 * @keying can take one of a number of values:
1097 *
1098 * (1) vfs_get_single_super - Only one superblock of this type may exist on the
1099 * system. This is typically used for special system filesystems.
1100 *
1101 * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have
1102 * distinct keys (where the key is in s_fs_info). Searching for the same
1103 * key again will turn up the superblock for that key.
1104 *
1105 * (3) vfs_get_independent_super - Multiple superblocks may exist and are
1106 * unkeyed. Each call will get a new superblock.
1107 *
1108 * A permissions check is made by sget_fc() unless we're getting a superblock
1109 * for a kernel-internal mount or a submount.
1110 */
1111int vfs_get_super(struct fs_context *fc,
1112 enum vfs_get_super_keying keying,
1113 int (*fill_super)(struct super_block *sb,
1114 struct fs_context *fc))
1115{
1116 int (*test)(struct super_block *, struct fs_context *);
1117 struct super_block *sb;
1118 int err;
1119
1120 switch (keying) {
1121 case vfs_get_single_super:
1122 case vfs_get_single_reconf_super:
1123 test = test_single_super;
1124 break;
1125 case vfs_get_keyed_super:
1126 test = test_keyed_super;
1127 break;
1128 case vfs_get_independent_super:
1129 test = NULL;
1130 break;
1131 default:
1132 BUG();
1133 }
1134
1135 sb = sget_fc(fc, test, set_anon_super_fc);
1136 if (IS_ERR(sb))
1137 return PTR_ERR(sb);
1138
1139 if (!sb->s_root) {
1140 err = fill_super(sb, fc);
1141 if (err)
1142 goto error;
1143
1144 sb->s_flags |= SB_ACTIVE;
1145 fc->root = dget(sb->s_root);
1146 } else {
1147 fc->root = dget(sb->s_root);
1148 if (keying == vfs_get_single_reconf_super) {
1149 err = reconfigure_super(fc);
1150 if (err < 0) {
1151 dput(fc->root);
1152 fc->root = NULL;
1153 goto error;
1154 }
1155 }
1156 }
1157
1158 return 0;
1159
1160error:
1161 deactivate_locked_super(sb);
1162 return err;
1163}
1164EXPORT_SYMBOL(vfs_get_super);
1165
1166int get_tree_nodev(struct fs_context *fc,
1167 int (*fill_super)(struct super_block *sb,
1168 struct fs_context *fc))
1169{
1170 return vfs_get_super(fc, vfs_get_independent_super, fill_super);
1171}
1172EXPORT_SYMBOL(get_tree_nodev);
1173
1174int get_tree_single(struct fs_context *fc,
1175 int (*fill_super)(struct super_block *sb,
1176 struct fs_context *fc))
1177{
1178 return vfs_get_super(fc, vfs_get_single_super, fill_super);
1179}
1180EXPORT_SYMBOL(get_tree_single);
1181
1182int get_tree_single_reconf(struct fs_context *fc,
1183 int (*fill_super)(struct super_block *sb,
1184 struct fs_context *fc))
1185{
1186 return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super);
1187}
1188EXPORT_SYMBOL(get_tree_single_reconf);
1189
1190int get_tree_keyed(struct fs_context *fc,
1191 int (*fill_super)(struct super_block *sb,
1192 struct fs_context *fc),
1193 void *key)
1194{
1195 fc->s_fs_info = key;
1196 return vfs_get_super(fc, vfs_get_keyed_super, fill_super);
1197}
1198EXPORT_SYMBOL(get_tree_keyed);
1199
1200#ifdef CONFIG_BLOCK
1201
1202static int set_bdev_super(struct super_block *s, void *data)
1203{
1204 s->s_bdev = data;
1205 s->s_dev = s->s_bdev->bd_dev;
1206 s->s_bdi = bdi_get(s->s_bdev->bd_bdi);
1207
1208 if (blk_queue_stable_writes(s->s_bdev->bd_disk->queue))
1209 s->s_iflags |= SB_I_STABLE_WRITES;
1210 return 0;
1211}
1212
1213static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1214{
1215 return set_bdev_super(s, fc->sget_key);
1216}
1217
1218static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1219{
1220 return s->s_bdev == fc->sget_key;
1221}
1222
1223/**
1224 * get_tree_bdev - Get a superblock based on a single block device
1225 * @fc: The filesystem context holding the parameters
1226 * @fill_super: Helper to initialise a new superblock
1227 */
1228int get_tree_bdev(struct fs_context *fc,
1229 int (*fill_super)(struct super_block *,
1230 struct fs_context *))
1231{
1232 struct block_device *bdev;
1233 struct super_block *s;
1234 fmode_t mode = FMODE_READ | FMODE_EXCL;
1235 int error = 0;
1236
1237 if (!(fc->sb_flags & SB_RDONLY))
1238 mode |= FMODE_WRITE;
1239
1240 if (!fc->source)
1241 return invalf(fc, "No source specified");
1242
1243 bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
1244 if (IS_ERR(bdev)) {
1245 errorf(fc, "%s: Can't open blockdev", fc->source);
1246 return PTR_ERR(bdev);
1247 }
1248
1249 /* Once the superblock is inserted into the list by sget_fc(), s_umount
1250 * will protect the lockfs code from trying to start a snapshot while
1251 * we are mounting
1252 */
1253 mutex_lock(&bdev->bd_fsfreeze_mutex);
1254 if (bdev->bd_fsfreeze_count > 0) {
1255 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1256 warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
1257 blkdev_put(bdev, mode);
1258 return -EBUSY;
1259 }
1260
1261 fc->sb_flags |= SB_NOSEC;
1262 fc->sget_key = bdev;
1263 s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
1264 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1265 if (IS_ERR(s)) {
1266 blkdev_put(bdev, mode);
1267 return PTR_ERR(s);
1268 }
1269
1270 if (s->s_root) {
1271 /* Don't summarily change the RO/RW state. */
1272 if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
1273 warnf(fc, "%pg: Can't mount, would change RO state", bdev);
1274 deactivate_locked_super(s);
1275 blkdev_put(bdev, mode);
1276 return -EBUSY;
1277 }
1278
1279 /*
1280 * s_umount nests inside open_mutex during
1281 * __invalidate_device(). blkdev_put() acquires
1282 * open_mutex and can't be called under s_umount. Drop
1283 * s_umount temporarily. This is safe as we're
1284 * holding an active reference.
1285 */
1286 up_write(&s->s_umount);
1287 blkdev_put(bdev, mode);
1288 down_write(&s->s_umount);
1289 } else {
1290 s->s_mode = mode;
1291 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1292 sb_set_blocksize(s, block_size(bdev));
1293 error = fill_super(s, fc);
1294 if (error) {
1295 deactivate_locked_super(s);
1296 return error;
1297 }
1298
1299 s->s_flags |= SB_ACTIVE;
1300 bdev->bd_super = s;
1301 }
1302
1303 BUG_ON(fc->root);
1304 fc->root = dget(s->s_root);
1305 return 0;
1306}
1307EXPORT_SYMBOL(get_tree_bdev);
1308
1309static int test_bdev_super(struct super_block *s, void *data)
1310{
1311 return (void *)s->s_bdev == data;
1312}
1313
1314struct dentry *mount_bdev(struct file_system_type *fs_type,
1315 int flags, const char *dev_name, void *data,
1316 int (*fill_super)(struct super_block *, void *, int))
1317{
1318 struct block_device *bdev;
1319 struct super_block *s;
1320 fmode_t mode = FMODE_READ | FMODE_EXCL;
1321 int error = 0;
1322
1323 if (!(flags & SB_RDONLY))
1324 mode |= FMODE_WRITE;
1325
1326 bdev = blkdev_get_by_path(dev_name, mode, fs_type);
1327 if (IS_ERR(bdev))
1328 return ERR_CAST(bdev);
1329
1330 /*
1331 * once the super is inserted into the list by sget, s_umount
1332 * will protect the lockfs code from trying to start a snapshot
1333 * while we are mounting
1334 */
1335 mutex_lock(&bdev->bd_fsfreeze_mutex);
1336 if (bdev->bd_fsfreeze_count > 0) {
1337 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1338 error = -EBUSY;
1339 goto error_bdev;
1340 }
1341 s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC,
1342 bdev);
1343 mutex_unlock(&bdev->bd_fsfreeze_mutex);
1344 if (IS_ERR(s))
1345 goto error_s;
1346
1347 if (s->s_root) {
1348 if ((flags ^ s->s_flags) & SB_RDONLY) {
1349 deactivate_locked_super(s);
1350 error = -EBUSY;
1351 goto error_bdev;
1352 }
1353
1354 /*
1355 * s_umount nests inside open_mutex during
1356 * __invalidate_device(). blkdev_put() acquires
1357 * open_mutex and can't be called under s_umount. Drop
1358 * s_umount temporarily. This is safe as we're
1359 * holding an active reference.
1360 */
1361 up_write(&s->s_umount);
1362 blkdev_put(bdev, mode);
1363 down_write(&s->s_umount);
1364 } else {
1365 s->s_mode = mode;
1366 snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1367 sb_set_blocksize(s, block_size(bdev));
1368 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1369 if (error) {
1370 deactivate_locked_super(s);
1371 goto error;
1372 }
1373
1374 s->s_flags |= SB_ACTIVE;
1375 bdev->bd_super = s;
1376 }
1377
1378 return dget(s->s_root);
1379
1380error_s:
1381 error = PTR_ERR(s);
1382error_bdev:
1383 blkdev_put(bdev, mode);
1384error:
1385 return ERR_PTR(error);
1386}
1387EXPORT_SYMBOL(mount_bdev);
1388
1389void kill_block_super(struct super_block *sb)
1390{
1391 struct block_device *bdev = sb->s_bdev;
1392 fmode_t mode = sb->s_mode;
1393
1394 bdev->bd_super = NULL;
1395 generic_shutdown_super(sb);
1396 sync_blockdev(bdev);
1397 WARN_ON_ONCE(!(mode & FMODE_EXCL));
1398 blkdev_put(bdev, mode | FMODE_EXCL);
1399}
1400
1401EXPORT_SYMBOL(kill_block_super);
1402#endif
1403
1404struct dentry *mount_nodev(struct file_system_type *fs_type,
1405 int flags, void *data,
1406 int (*fill_super)(struct super_block *, void *, int))
1407{
1408 int error;
1409 struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1410
1411 if (IS_ERR(s))
1412 return ERR_CAST(s);
1413
1414 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1415 if (error) {
1416 deactivate_locked_super(s);
1417 return ERR_PTR(error);
1418 }
1419 s->s_flags |= SB_ACTIVE;
1420 return dget(s->s_root);
1421}
1422EXPORT_SYMBOL(mount_nodev);
1423
1424static int reconfigure_single(struct super_block *s,
1425 int flags, void *data)
1426{
1427 struct fs_context *fc;
1428 int ret;
1429
1430 /* The caller really need to be passing fc down into mount_single(),
1431 * then a chunk of this can be removed. [Bollocks -- AV]
1432 * Better yet, reconfiguration shouldn't happen, but rather the second
1433 * mount should be rejected if the parameters are not compatible.
1434 */
1435 fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
1436 if (IS_ERR(fc))
1437 return PTR_ERR(fc);
1438
1439 ret = parse_monolithic_mount_data(fc, data);
1440 if (ret < 0)
1441 goto out;
1442
1443 ret = reconfigure_super(fc);
1444out:
1445 put_fs_context(fc);
1446 return ret;
1447}
1448
1449static int compare_single(struct super_block *s, void *p)
1450{
1451 return 1;
1452}
1453
1454struct dentry *mount_single(struct file_system_type *fs_type,
1455 int flags, void *data,
1456 int (*fill_super)(struct super_block *, void *, int))
1457{
1458 struct super_block *s;
1459 int error;
1460
1461 s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1462 if (IS_ERR(s))
1463 return ERR_CAST(s);
1464 if (!s->s_root) {
1465 error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1466 if (!error)
1467 s->s_flags |= SB_ACTIVE;
1468 } else {
1469 error = reconfigure_single(s, flags, data);
1470 }
1471 if (unlikely(error)) {
1472 deactivate_locked_super(s);
1473 return ERR_PTR(error);
1474 }
1475 return dget(s->s_root);
1476}
1477EXPORT_SYMBOL(mount_single);
1478
1479/**
1480 * vfs_get_tree - Get the mountable root
1481 * @fc: The superblock configuration context.
1482 *
1483 * The filesystem is invoked to get or create a superblock which can then later
1484 * be used for mounting. The filesystem places a pointer to the root to be
1485 * used for mounting in @fc->root.
1486 */
1487int vfs_get_tree(struct fs_context *fc)
1488{
1489 struct super_block *sb;
1490 int error;
1491
1492 if (fc->root)
1493 return -EBUSY;
1494
1495 /* Get the mountable root in fc->root, with a ref on the root and a ref
1496 * on the superblock.
1497 */
1498 error = fc->ops->get_tree(fc);
1499 if (error < 0)
1500 return error;
1501
1502 if (!fc->root) {
1503 pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1504 fc->fs_type->name);
1505 /* We don't know what the locking state of the superblock is -
1506 * if there is a superblock.
1507 */
1508 BUG();
1509 }
1510
1511 sb = fc->root->d_sb;
1512 WARN_ON(!sb->s_bdi);
1513
1514 /*
1515 * Write barrier is for super_cache_count(). We place it before setting
1516 * SB_BORN as the data dependency between the two functions is the
1517 * superblock structure contents that we just set up, not the SB_BORN
1518 * flag.
1519 */
1520 smp_wmb();
1521 sb->s_flags |= SB_BORN;
1522
1523 error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
1524 if (unlikely(error)) {
1525 fc_drop_locked(fc);
1526 return error;
1527 }
1528
1529 /*
1530 * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1531 * but s_maxbytes was an unsigned long long for many releases. Throw
1532 * this warning for a little while to try and catch filesystems that
1533 * violate this rule.
1534 */
1535 WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1536 "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);
1537
1538 return 0;
1539}
1540EXPORT_SYMBOL(vfs_get_tree);
1541
1542/*
1543 * Setup private BDI for given superblock. It gets automatically cleaned up
1544 * in generic_shutdown_super().
1545 */
1546int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
1547{
1548 struct backing_dev_info *bdi;
1549 int err;
1550 va_list args;
1551
1552 bdi = bdi_alloc(NUMA_NO_NODE);
1553 if (!bdi)
1554 return -ENOMEM;
1555
1556 va_start(args, fmt);
1557 err = bdi_register_va(bdi, fmt, args);
1558 va_end(args);
1559 if (err) {
1560 bdi_put(bdi);
1561 return err;
1562 }
1563 WARN_ON(sb->s_bdi != &noop_backing_dev_info);
1564 sb->s_bdi = bdi;
1565
1566 return 0;
1567}
1568EXPORT_SYMBOL(super_setup_bdi_name);
1569
1570/*
1571 * Setup private BDI for given superblock. I gets automatically cleaned up
1572 * in generic_shutdown_super().
1573 */
1574int super_setup_bdi(struct super_block *sb)
1575{
1576 static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
1577
1578 return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
1579 atomic_long_inc_return(&bdi_seq));
1580}
1581EXPORT_SYMBOL(super_setup_bdi);
1582
1583/**
1584 * sb_wait_write - wait until all writers to given file system finish
1585 * @sb: the super for which we wait
1586 * @level: type of writers we wait for (normal vs page fault)
1587 *
1588 * This function waits until there are no writers of given type to given file
1589 * system.
1590 */
1591static void sb_wait_write(struct super_block *sb, int level)
1592{
1593 percpu_down_write(sb->s_writers.rw_sem + level-1);
1594}
1595
1596/*
1597 * We are going to return to userspace and forget about these locks, the
1598 * ownership goes to the caller of thaw_super() which does unlock().
1599 */
1600static void lockdep_sb_freeze_release(struct super_block *sb)
1601{
1602 int level;
1603
1604 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1605 percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1606}
1607
1608/*
1609 * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1610 */
1611static void lockdep_sb_freeze_acquire(struct super_block *sb)
1612{
1613 int level;
1614
1615 for (level = 0; level < SB_FREEZE_LEVELS; ++level)
1616 percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1617}
1618
1619static void sb_freeze_unlock(struct super_block *sb)
1620{
1621 int level;
1622
1623 for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1624 percpu_up_write(sb->s_writers.rw_sem + level);
1625}
1626
1627/**
1628 * freeze_super - lock the filesystem and force it into a consistent state
1629 * @sb: the super to lock
1630 *
1631 * Syncs the super to make sure the filesystem is consistent and calls the fs's
1632 * freeze_fs. Subsequent calls to this without first thawing the fs will return
1633 * -EBUSY.
1634 *
1635 * During this function, sb->s_writers.frozen goes through these values:
1636 *
1637 * SB_UNFROZEN: File system is normal, all writes progress as usual.
1638 *
1639 * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1640 * writes should be blocked, though page faults are still allowed. We wait for
1641 * all writes to complete and then proceed to the next stage.
1642 *
1643 * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1644 * but internal fs threads can still modify the filesystem (although they
1645 * should not dirty new pages or inodes), writeback can run etc. After waiting
1646 * for all running page faults we sync the filesystem which will clean all
1647 * dirty pages and inodes (no new dirty pages or inodes can be created when
1648 * sync is running).
1649 *
1650 * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1651 * modification are blocked (e.g. XFS preallocation truncation on inode
1652 * reclaim). This is usually implemented by blocking new transactions for
1653 * filesystems that have them and need this additional guard. After all
1654 * internal writers are finished we call ->freeze_fs() to finish filesystem
1655 * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1656 * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1657 *
1658 * sb->s_writers.frozen is protected by sb->s_umount.
1659 */
1660int freeze_super(struct super_block *sb)
1661{
1662 int ret;
1663
1664 atomic_inc(&sb->s_active);
1665 down_write(&sb->s_umount);
1666 if (sb->s_writers.frozen != SB_UNFROZEN) {
1667 deactivate_locked_super(sb);
1668 return -EBUSY;
1669 }
1670
1671 if (!(sb->s_flags & SB_BORN)) {
1672 up_write(&sb->s_umount);
1673 return 0; /* sic - it's "nothing to do" */
1674 }
1675
1676 if (sb_rdonly(sb)) {
1677 /* Nothing to do really... */
1678 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1679 up_write(&sb->s_umount);
1680 return 0;
1681 }
1682
1683 sb->s_writers.frozen = SB_FREEZE_WRITE;
1684 /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1685 up_write(&sb->s_umount);
1686 sb_wait_write(sb, SB_FREEZE_WRITE);
1687 down_write(&sb->s_umount);
1688
1689 /* Now we go and block page faults... */
1690 sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
1691 sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
1692
1693 /* All writers are done so after syncing there won't be dirty data */
1694 sync_filesystem(sb);
1695
1696 /* Now wait for internal filesystem counter */
1697 sb->s_writers.frozen = SB_FREEZE_FS;
1698 sb_wait_write(sb, SB_FREEZE_FS);
1699
1700 if (sb->s_op->freeze_fs) {
1701 ret = sb->s_op->freeze_fs(sb);
1702 if (ret) {
1703 printk(KERN_ERR
1704 "VFS:Filesystem freeze failed\n");
1705 sb->s_writers.frozen = SB_UNFROZEN;
1706 sb_freeze_unlock(sb);
1707 wake_up(&sb->s_writers.wait_unfrozen);
1708 deactivate_locked_super(sb);
1709 return ret;
1710 }
1711 }
1712 /*
1713 * For debugging purposes so that fs can warn if it sees write activity
1714 * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
1715 */
1716 sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1717 lockdep_sb_freeze_release(sb);
1718 up_write(&sb->s_umount);
1719 return 0;
1720}
1721EXPORT_SYMBOL(freeze_super);
1722
1723static int thaw_super_locked(struct super_block *sb)
1724{
1725 int error;
1726
1727 if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
1728 up_write(&sb->s_umount);
1729 return -EINVAL;
1730 }
1731
1732 if (sb_rdonly(sb)) {
1733 sb->s_writers.frozen = SB_UNFROZEN;
1734 goto out;
1735 }
1736
1737 lockdep_sb_freeze_acquire(sb);
1738
1739 if (sb->s_op->unfreeze_fs) {
1740 error = sb->s_op->unfreeze_fs(sb);
1741 if (error) {
1742 printk(KERN_ERR
1743 "VFS:Filesystem thaw failed\n");
1744 lockdep_sb_freeze_release(sb);
1745 up_write(&sb->s_umount);
1746 return error;
1747 }
1748 }
1749
1750 sb->s_writers.frozen = SB_UNFROZEN;
1751 sb_freeze_unlock(sb);
1752out:
1753 wake_up(&sb->s_writers.wait_unfrozen);
1754 deactivate_locked_super(sb);
1755 return 0;
1756}
1757
1758/**
1759 * thaw_super -- unlock filesystem
1760 * @sb: the super to thaw
1761 *
1762 * Unlocks the filesystem and marks it writeable again after freeze_super().
1763 */
1764int thaw_super(struct super_block *sb)
1765{
1766 down_write(&sb->s_umount);
1767 return thaw_super_locked(sb);
1768}
1769EXPORT_SYMBOL(thaw_super);