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