Line data Source code
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 :
43 : static int thaw_super_locked(struct super_block *sb);
44 :
45 : static LIST_HEAD(super_blocks);
46 : static DEFINE_SPINLOCK(sb_lock);
47 :
48 : static 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 : */
61 0 : static unsigned long super_cache_scan(struct shrinker *shrink,
62 : struct shrink_control *sc)
63 : {
64 0 : struct super_block *sb;
65 0 : long fs_objects = 0;
66 0 : long total_objects;
67 0 : long freed = 0;
68 0 : long dentries;
69 0 : long inodes;
70 :
71 0 : 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 0 : if (!(sc->gfp_mask & __GFP_FS))
78 : return SHRINK_STOP;
79 :
80 0 : if (!trylock_super(sb))
81 : return SHRINK_STOP;
82 :
83 0 : if (sb->s_op->nr_cached_objects)
84 0 : fs_objects = sb->s_op->nr_cached_objects(sb, sc);
85 :
86 0 : inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
87 0 : dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
88 0 : total_objects = dentries + inodes + fs_objects + 1;
89 0 : if (!total_objects)
90 0 : total_objects = 1;
91 :
92 : /* proportion the scan between the caches */
93 0 : dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
94 0 : inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
95 0 : 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 0 : sc->nr_to_scan = dentries + 1;
105 0 : freed = prune_dcache_sb(sb, sc);
106 0 : sc->nr_to_scan = inodes + 1;
107 0 : freed += prune_icache_sb(sb, sc);
108 :
109 0 : if (fs_objects) {
110 0 : sc->nr_to_scan = fs_objects + 1;
111 0 : freed += sb->s_op->free_cached_objects(sb, sc);
112 : }
113 :
114 0 : up_read(&sb->s_umount);
115 0 : return freed;
116 : }
117 :
118 0 : static unsigned long super_cache_count(struct shrinker *shrink,
119 : struct shrink_control *sc)
120 : {
121 0 : struct super_block *sb;
122 0 : long total_objects = 0;
123 :
124 0 : 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 0 : if (!(sb->s_flags & SB_BORN))
141 : return 0;
142 0 : smp_rmb();
143 :
144 0 : if (sb->s_op && sb->s_op->nr_cached_objects)
145 0 : total_objects = sb->s_op->nr_cached_objects(sb, sc);
146 :
147 0 : total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
148 0 : total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
149 :
150 0 : if (!total_objects)
151 : return SHRINK_EMPTY;
152 :
153 0 : total_objects = vfs_pressure_ratio(total_objects);
154 0 : return total_objects;
155 : }
156 :
157 99 : static void destroy_super_work(struct work_struct *work)
158 : {
159 99 : struct super_block *s = container_of(work, struct super_block,
160 : destroy_work);
161 99 : int i;
162 :
163 396 : for (i = 0; i < SB_FREEZE_LEVELS; i++)
164 297 : percpu_free_rwsem(&s->s_writers.rw_sem[i]);
165 99 : kfree(s);
166 99 : }
167 :
168 99 : static void destroy_super_rcu(struct rcu_head *head)
169 : {
170 99 : struct super_block *s = container_of(head, struct super_block, rcu);
171 99 : INIT_WORK(&s->destroy_work, destroy_super_work);
172 99 : schedule_work(&s->destroy_work);
173 99 : }
174 :
175 : /* Free a superblock that has never been seen by anyone */
176 3 : static void destroy_unused_super(struct super_block *s)
177 : {
178 3 : if (!s)
179 : return;
180 0 : up_write(&s->s_umount);
181 0 : list_lru_destroy(&s->s_dentry_lru);
182 0 : list_lru_destroy(&s->s_inode_lru);
183 0 : security_sb_free(s);
184 0 : put_user_ns(s->s_user_ns);
185 0 : kfree(s->s_subtype);
186 0 : free_prealloced_shrinker(&s->s_shrink);
187 : /* no delays needed */
188 0 : 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 : */
200 123 : static struct super_block *alloc_super(struct file_system_type *type, int flags,
201 : struct user_namespace *user_ns)
202 : {
203 123 : struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
204 123 : static const struct super_operations default_op;
205 123 : int i;
206 :
207 123 : if (!s)
208 : return NULL;
209 :
210 123 : INIT_LIST_HEAD(&s->s_mounts);
211 123 : s->s_user_ns = get_user_ns(user_ns);
212 123 : init_rwsem(&s->s_umount);
213 123 : 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 : */
229 123 : down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
230 :
231 123 : if (security_sb_alloc(s))
232 0 : goto fail;
233 :
234 492 : for (i = 0; i < SB_FREEZE_LEVELS; i++) {
235 369 : if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
236 369 : sb_writers_name[i],
237 : &type->s_writers_key[i]))
238 0 : goto fail;
239 : }
240 123 : init_waitqueue_head(&s->s_writers.wait_unfrozen);
241 123 : s->s_bdi = &noop_backing_dev_info;
242 123 : s->s_flags = flags;
243 123 : if (s->s_user_ns != &init_user_ns)
244 0 : s->s_iflags |= SB_I_NODEV;
245 123 : INIT_HLIST_NODE(&s->s_instances);
246 123 : INIT_HLIST_BL_HEAD(&s->s_roots);
247 123 : mutex_init(&s->s_sync_lock);
248 123 : INIT_LIST_HEAD(&s->s_inodes);
249 123 : spin_lock_init(&s->s_inode_list_lock);
250 123 : INIT_LIST_HEAD(&s->s_inodes_wb);
251 123 : spin_lock_init(&s->s_inode_wblist_lock);
252 :
253 123 : s->s_count = 1;
254 123 : atomic_set(&s->s_active, 1);
255 123 : mutex_init(&s->s_vfs_rename_mutex);
256 123 : lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
257 123 : init_rwsem(&s->s_dquot.dqio_sem);
258 123 : s->s_maxbytes = MAX_NON_LFS;
259 123 : s->s_op = &default_op;
260 123 : s->s_time_gran = 1000000000;
261 123 : s->s_time_min = TIME64_MIN;
262 123 : s->s_time_max = TIME64_MAX;
263 123 : s->cleancache_poolid = CLEANCACHE_NO_POOL;
264 :
265 123 : s->s_shrink.seeks = DEFAULT_SEEKS;
266 123 : s->s_shrink.scan_objects = super_cache_scan;
267 123 : s->s_shrink.count_objects = super_cache_count;
268 123 : s->s_shrink.batch = 1024;
269 123 : s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
270 123 : if (prealloc_shrinker(&s->s_shrink))
271 0 : goto fail;
272 123 : if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink))
273 0 : goto fail;
274 123 : if (list_lru_init_memcg(&s->s_inode_lru, &s->s_shrink))
275 0 : goto fail;
276 : return s;
277 :
278 0 : fail:
279 0 : destroy_unused_super(s);
280 0 : return NULL;
281 : }
282 :
283 : /* Superblock refcounting */
284 :
285 : /*
286 : * Drop a superblock's refcount. The caller must hold sb_lock.
287 : */
288 102 : static void __put_super(struct super_block *s)
289 : {
290 102 : if (!--s->s_count) {
291 99 : list_del_init(&s->s_list);
292 99 : WARN_ON(s->s_dentry_lru.node);
293 99 : WARN_ON(s->s_inode_lru.node);
294 99 : WARN_ON(!list_empty(&s->s_mounts));
295 99 : security_sb_free(s);
296 99 : fscrypt_sb_free(s);
297 99 : put_user_ns(s->s_user_ns);
298 99 : kfree(s->s_subtype);
299 99 : call_rcu(&s->rcu, destroy_super_rcu);
300 : }
301 102 : }
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 : */
310 102 : void put_super(struct super_block *sb)
311 : {
312 102 : spin_lock(&sb_lock);
313 102 : __put_super(sb);
314 102 : spin_unlock(&sb_lock);
315 102 : }
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 : */
329 99 : void deactivate_locked_super(struct super_block *s)
330 : {
331 99 : struct file_system_type *fs = s->s_type;
332 198 : if (atomic_dec_and_test(&s->s_active)) {
333 99 : cleancache_invalidate_fs(s);
334 99 : unregister_shrinker(&s->s_shrink);
335 99 : 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 99 : list_lru_destroy(&s->s_dentry_lru);
343 99 : list_lru_destroy(&s->s_inode_lru);
344 :
345 99 : put_filesystem(fs);
346 99 : put_super(s);
347 : } else {
348 0 : up_write(&s->s_umount);
349 : }
350 99 : }
351 :
352 : EXPORT_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 : */
362 1363 : void deactivate_super(struct super_block *s)
363 : {
364 2726 : if (!atomic_add_unless(&s->s_active, -1, 1)) {
365 98 : down_write(&s->s_umount);
366 98 : deactivate_locked_super(s);
367 : }
368 1363 : }
369 :
370 : EXPORT_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 : */
385 3 : static int grab_super(struct super_block *s) __releases(sb_lock)
386 : {
387 3 : s->s_count++;
388 3 : spin_unlock(&sb_lock);
389 3 : down_write(&s->s_umount);
390 6 : if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) {
391 3 : put_super(s);
392 3 : return 1;
393 : }
394 0 : up_write(&s->s_umount);
395 0 : put_super(s);
396 0 : 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 : */
416 7 : bool trylock_super(struct super_block *sb)
417 : {
418 7 : if (down_read_trylock(&sb->s_umount)) {
419 7 : if (!hlist_unhashed(&sb->s_instances) &&
420 7 : sb->s_root && (sb->s_flags & SB_BORN))
421 : return true;
422 0 : 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 : */
442 99 : void generic_shutdown_super(struct super_block *sb)
443 : {
444 99 : const struct super_operations *sop = sb->s_op;
445 :
446 99 : if (sb->s_root) {
447 98 : shrink_dcache_for_umount(sb);
448 98 : sync_filesystem(sb);
449 98 : sb->s_flags &= ~SB_ACTIVE;
450 :
451 98 : cgroup_writeback_umount();
452 :
453 : /* evict all inodes with zero refcount */
454 98 : evict_inodes(sb);
455 : /* only nonzero refcount inodes can have marks */
456 98 : fsnotify_sb_delete(sb);
457 98 : security_sb_delete(sb);
458 :
459 98 : if (sb->s_dio_done_wq) {
460 0 : destroy_workqueue(sb->s_dio_done_wq);
461 0 : sb->s_dio_done_wq = NULL;
462 : }
463 :
464 98 : if (sop->put_super)
465 97 : sop->put_super(sb);
466 :
467 98 : if (!list_empty(&sb->s_inodes)) {
468 0 : printk("VFS: Busy inodes after unmount of %s. "
469 : "Self-destruct in 5 seconds. Have a nice day...\n",
470 0 : sb->s_id);
471 : }
472 : }
473 99 : spin_lock(&sb_lock);
474 : /* should be initialized for __put_super_and_need_restart() */
475 99 : hlist_del_init(&sb->s_instances);
476 99 : spin_unlock(&sb_lock);
477 99 : up_write(&sb->s_umount);
478 99 : if (sb->s_bdi != &noop_backing_dev_info) {
479 1 : bdi_put(sb->s_bdi);
480 1 : sb->s_bdi = &noop_backing_dev_info;
481 : }
482 99 : }
483 :
484 : EXPORT_SYMBOL(generic_shutdown_super);
485 :
486 116 : bool mount_capable(struct fs_context *fc)
487 : {
488 116 : if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
489 5 : return capable(CAP_SYS_ADMIN);
490 : else
491 111 : 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 : */
512 118 : struct 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 : {
516 118 : struct super_block *s = NULL;
517 118 : struct super_block *old;
518 118 : struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
519 234 : int err;
520 :
521 : retry:
522 234 : spin_lock(&sb_lock);
523 234 : if (test) {
524 20 : hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
525 2 : if (test(old, fc))
526 2 : goto share_extant_sb;
527 : }
528 : }
529 232 : if (!s) {
530 116 : spin_unlock(&sb_lock);
531 116 : s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
532 116 : if (!s)
533 118 : return ERR_PTR(-ENOMEM);
534 116 : goto retry;
535 : }
536 :
537 116 : s->s_fs_info = fc->s_fs_info;
538 116 : err = set(s, fc);
539 116 : if (err) {
540 0 : s->s_fs_info = NULL;
541 0 : spin_unlock(&sb_lock);
542 0 : destroy_unused_super(s);
543 0 : return ERR_PTR(err);
544 : }
545 116 : fc->s_fs_info = NULL;
546 116 : s->s_type = fc->fs_type;
547 116 : s->s_iflags |= fc->s_iflags;
548 116 : strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
549 116 : list_add_tail(&s->s_list, &super_blocks);
550 116 : hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
551 116 : spin_unlock(&sb_lock);
552 116 : get_filesystem(s->s_type);
553 116 : register_shrinker_prepared(&s->s_shrink);
554 116 : return s;
555 :
556 2 : share_extant_sb:
557 2 : if (user_ns != old->s_user_ns) {
558 0 : spin_unlock(&sb_lock);
559 0 : destroy_unused_super(s);
560 0 : return ERR_PTR(-EBUSY);
561 : }
562 2 : if (!grab_super(old))
563 0 : goto retry;
564 2 : destroy_unused_super(s);
565 2 : return old;
566 : }
567 : EXPORT_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 : */
577 8 : struct 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 8 : struct user_namespace *user_ns = current_user_ns();
584 8 : struct super_block *s = NULL;
585 8 : struct super_block *old;
586 8 : 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 8 : if (flags & SB_SUBMOUNT)
593 8 : user_ns = &init_user_ns;
594 :
595 8 : retry:
596 15 : spin_lock(&sb_lock);
597 15 : if (test) {
598 18 : hlist_for_each_entry(old, &type->fs_supers, s_instances) {
599 1 : if (!test(old, data))
600 0 : continue;
601 1 : if (user_ns != old->s_user_ns) {
602 0 : spin_unlock(&sb_lock);
603 0 : destroy_unused_super(s);
604 0 : return ERR_PTR(-EBUSY);
605 : }
606 1 : if (!grab_super(old))
607 0 : goto retry;
608 1 : destroy_unused_super(s);
609 1 : return old;
610 : }
611 : }
612 14 : if (!s) {
613 7 : spin_unlock(&sb_lock);
614 7 : s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
615 7 : if (!s)
616 8 : return ERR_PTR(-ENOMEM);
617 7 : goto retry;
618 : }
619 :
620 7 : err = set(s, data);
621 7 : if (err) {
622 0 : spin_unlock(&sb_lock);
623 0 : destroy_unused_super(s);
624 0 : return ERR_PTR(err);
625 : }
626 7 : s->s_type = type;
627 7 : strlcpy(s->s_id, type->name, sizeof(s->s_id));
628 7 : list_add_tail(&s->s_list, &super_blocks);
629 7 : hlist_add_head(&s->s_instances, &type->fs_supers);
630 7 : spin_unlock(&sb_lock);
631 7 : get_filesystem(type);
632 7 : register_shrinker_prepared(&s->s_shrink);
633 7 : return s;
634 : }
635 : EXPORT_SYMBOL(sget);
636 :
637 0 : void drop_super(struct super_block *sb)
638 : {
639 0 : up_read(&sb->s_umount);
640 0 : put_super(sb);
641 0 : }
642 :
643 : EXPORT_SYMBOL(drop_super);
644 :
645 0 : void drop_super_exclusive(struct super_block *sb)
646 : {
647 0 : up_write(&sb->s_umount);
648 0 : put_super(sb);
649 0 : }
650 : EXPORT_SYMBOL(drop_super_exclusive);
651 :
652 0 : static void __iterate_supers(void (*f)(struct super_block *))
653 : {
654 0 : struct super_block *sb, *p = NULL;
655 :
656 0 : spin_lock(&sb_lock);
657 0 : list_for_each_entry(sb, &super_blocks, s_list) {
658 0 : if (hlist_unhashed(&sb->s_instances))
659 0 : continue;
660 0 : sb->s_count++;
661 0 : spin_unlock(&sb_lock);
662 :
663 0 : f(sb);
664 :
665 0 : spin_lock(&sb_lock);
666 0 : if (p)
667 0 : __put_super(p);
668 : p = sb;
669 : }
670 0 : if (p)
671 0 : __put_super(p);
672 0 : spin_unlock(&sb_lock);
673 0 : }
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 : */
682 0 : void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
683 : {
684 0 : struct super_block *sb, *p = NULL;
685 :
686 0 : spin_lock(&sb_lock);
687 0 : list_for_each_entry(sb, &super_blocks, s_list) {
688 0 : if (hlist_unhashed(&sb->s_instances))
689 0 : continue;
690 0 : sb->s_count++;
691 0 : spin_unlock(&sb_lock);
692 :
693 0 : down_read(&sb->s_umount);
694 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
695 0 : f(sb, arg);
696 0 : up_read(&sb->s_umount);
697 :
698 0 : spin_lock(&sb_lock);
699 0 : if (p)
700 0 : __put_super(p);
701 : p = sb;
702 : }
703 0 : if (p)
704 0 : __put_super(p);
705 0 : spin_unlock(&sb_lock);
706 0 : }
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 : */
717 0 : void iterate_supers_type(struct file_system_type *type,
718 : void (*f)(struct super_block *, void *), void *arg)
719 : {
720 0 : struct super_block *sb, *p = NULL;
721 :
722 0 : spin_lock(&sb_lock);
723 0 : hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
724 0 : sb->s_count++;
725 0 : spin_unlock(&sb_lock);
726 :
727 0 : down_read(&sb->s_umount);
728 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
729 0 : f(sb, arg);
730 0 : up_read(&sb->s_umount);
731 :
732 0 : spin_lock(&sb_lock);
733 0 : if (p)
734 0 : __put_super(p);
735 0 : p = sb;
736 : }
737 0 : if (p)
738 0 : __put_super(p);
739 0 : spin_unlock(&sb_lock);
740 0 : }
741 :
742 : EXPORT_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 : */
751 0 : struct super_block *get_super(struct block_device *bdev)
752 : {
753 0 : struct super_block *sb;
754 :
755 0 : if (!bdev)
756 : return NULL;
757 :
758 0 : spin_lock(&sb_lock);
759 0 : rescan:
760 0 : list_for_each_entry(sb, &super_blocks, s_list) {
761 0 : if (hlist_unhashed(&sb->s_instances))
762 0 : continue;
763 0 : if (sb->s_bdev == bdev) {
764 0 : sb->s_count++;
765 0 : spin_unlock(&sb_lock);
766 0 : down_read(&sb->s_umount);
767 : /* still alive? */
768 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
769 0 : return sb;
770 0 : up_read(&sb->s_umount);
771 : /* nope, got unmounted */
772 0 : spin_lock(&sb_lock);
773 0 : __put_super(sb);
774 0 : goto rescan;
775 : }
776 : }
777 0 : spin_unlock(&sb_lock);
778 0 : 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 : */
789 0 : struct super_block *get_active_super(struct block_device *bdev)
790 : {
791 0 : struct super_block *sb;
792 :
793 0 : if (!bdev)
794 : return NULL;
795 :
796 0 : restart:
797 0 : spin_lock(&sb_lock);
798 0 : list_for_each_entry(sb, &super_blocks, s_list) {
799 0 : if (hlist_unhashed(&sb->s_instances))
800 0 : continue;
801 0 : if (sb->s_bdev == bdev) {
802 0 : if (!grab_super(sb))
803 0 : goto restart;
804 0 : up_write(&sb->s_umount);
805 0 : return sb;
806 : }
807 : }
808 0 : spin_unlock(&sb_lock);
809 0 : return NULL;
810 : }
811 :
812 0 : struct super_block *user_get_super(dev_t dev, bool excl)
813 : {
814 0 : struct super_block *sb;
815 :
816 0 : spin_lock(&sb_lock);
817 0 : rescan:
818 0 : list_for_each_entry(sb, &super_blocks, s_list) {
819 0 : if (hlist_unhashed(&sb->s_instances))
820 0 : continue;
821 0 : if (sb->s_dev == dev) {
822 0 : sb->s_count++;
823 0 : spin_unlock(&sb_lock);
824 0 : if (excl)
825 0 : down_write(&sb->s_umount);
826 : else
827 0 : down_read(&sb->s_umount);
828 : /* still alive? */
829 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
830 0 : return sb;
831 0 : if (excl)
832 0 : up_write(&sb->s_umount);
833 : else
834 0 : up_read(&sb->s_umount);
835 : /* nope, got unmounted */
836 0 : spin_lock(&sb_lock);
837 0 : __put_super(sb);
838 0 : goto rescan;
839 : }
840 : }
841 0 : spin_unlock(&sb_lock);
842 0 : 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 : */
851 3 : int reconfigure_super(struct fs_context *fc)
852 : {
853 3 : struct super_block *sb = fc->root->d_sb;
854 3 : int retval;
855 3 : bool remount_ro = false;
856 3 : bool force = fc->sb_flags & SB_FORCE;
857 :
858 3 : if (fc->sb_flags_mask & ~MS_RMT_MASK)
859 : return -EINVAL;
860 3 : if (sb->s_writers.frozen != SB_UNFROZEN)
861 : return -EBUSY;
862 :
863 3 : retval = security_sb_remount(sb, fc->security);
864 3 : if (retval)
865 : return retval;
866 :
867 3 : if (fc->sb_flags_mask & SB_RDONLY) {
868 : #ifdef CONFIG_BLOCK
869 4 : if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&
870 1 : bdev_read_only(sb->s_bdev))
871 : return -EACCES;
872 : #endif
873 :
874 3 : remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
875 : }
876 :
877 3 : if (remount_ro) {
878 1 : if (!hlist_empty(&sb->s_pins)) {
879 0 : up_write(&sb->s_umount);
880 0 : group_pin_kill(&sb->s_pins);
881 0 : down_write(&sb->s_umount);
882 0 : if (!sb->s_root)
883 : return 0;
884 0 : if (sb->s_writers.frozen != SB_UNFROZEN)
885 : return -EBUSY;
886 0 : remount_ro = !sb_rdonly(sb);
887 : }
888 : }
889 3 : 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 3 : if (remount_ro) {
895 1 : if (force) {
896 0 : sb->s_readonly_remount = 1;
897 0 : smp_wmb();
898 : } else {
899 1 : retval = sb_prepare_remount_readonly(sb);
900 1 : if (retval)
901 : return retval;
902 : }
903 : }
904 :
905 3 : if (fc->ops->reconfigure) {
906 3 : retval = fc->ops->reconfigure(fc);
907 3 : if (retval) {
908 0 : if (!force)
909 0 : goto cancel_readonly;
910 : /* If forced remount, go ahead despite any errors */
911 0 : WARN(1, "forced remount of a %s fs returned %i\n",
912 : sb->s_type->name, retval);
913 : }
914 : }
915 :
916 3 : 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 3 : smp_wmb();
920 3 : 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 3 : if (remount_ro && sb->s_bdev)
931 0 : invalidate_bdev(sb->s_bdev);
932 : return 0;
933 :
934 0 : cancel_readonly:
935 0 : sb->s_readonly_remount = 0;
936 0 : return retval;
937 : }
938 :
939 0 : static void do_emergency_remount_callback(struct super_block *sb)
940 : {
941 0 : down_write(&sb->s_umount);
942 0 : if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
943 0 : !sb_rdonly(sb)) {
944 0 : struct fs_context *fc;
945 :
946 0 : fc = fs_context_for_reconfigure(sb->s_root,
947 : SB_RDONLY | SB_FORCE, SB_RDONLY);
948 0 : if (!IS_ERR(fc)) {
949 0 : if (parse_monolithic_mount_data(fc, NULL) == 0)
950 0 : (void)reconfigure_super(fc);
951 0 : put_fs_context(fc);
952 : }
953 : }
954 0 : up_write(&sb->s_umount);
955 0 : }
956 :
957 0 : static void do_emergency_remount(struct work_struct *work)
958 : {
959 0 : __iterate_supers(do_emergency_remount_callback);
960 0 : kfree(work);
961 0 : printk("Emergency Remount complete\n");
962 0 : }
963 :
964 0 : void emergency_remount(void)
965 : {
966 0 : struct work_struct *work;
967 :
968 0 : work = kmalloc(sizeof(*work), GFP_ATOMIC);
969 0 : if (work) {
970 0 : INIT_WORK(work, do_emergency_remount);
971 0 : schedule_work(work);
972 : }
973 0 : }
974 :
975 0 : static void do_thaw_all_callback(struct super_block *sb)
976 : {
977 0 : down_write(&sb->s_umount);
978 0 : if (sb->s_root && sb->s_flags & SB_BORN) {
979 0 : emergency_thaw_bdev(sb);
980 0 : thaw_super_locked(sb);
981 : } else {
982 0 : up_write(&sb->s_umount);
983 : }
984 0 : }
985 :
986 0 : static void do_thaw_all(struct work_struct *work)
987 : {
988 0 : __iterate_supers(do_thaw_all_callback);
989 0 : kfree(work);
990 0 : printk(KERN_WARNING "Emergency Thaw complete\n");
991 0 : }
992 :
993 : /**
994 : * emergency_thaw_all -- forcibly thaw every frozen filesystem
995 : *
996 : * Used for emergency unfreeze of all filesystems via SysRq
997 : */
998 0 : void emergency_thaw_all(void)
999 : {
1000 0 : struct work_struct *work;
1001 :
1002 0 : work = kmalloc(sizeof(*work), GFP_ATOMIC);
1003 0 : if (work) {
1004 0 : INIT_WORK(work, do_thaw_all);
1005 0 : schedule_work(work);
1006 : }
1007 0 : }
1008 :
1009 : static 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 : */
1022 125 : int get_anon_bdev(dev_t *p)
1023 : {
1024 125 : 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 125 : dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
1031 : GFP_ATOMIC);
1032 125 : if (dev == -ENOSPC)
1033 : dev = -EMFILE;
1034 125 : if (dev < 0)
1035 0 : return dev;
1036 :
1037 125 : *p = MKDEV(0, dev);
1038 125 : return 0;
1039 : }
1040 : EXPORT_SYMBOL(get_anon_bdev);
1041 :
1042 102 : void free_anon_bdev(dev_t dev)
1043 : {
1044 4 : ida_free(&unnamed_dev_ida, MINOR(dev));
1045 4 : }
1046 : EXPORT_SYMBOL(free_anon_bdev);
1047 :
1048 121 : int set_anon_super(struct super_block *s, void *data)
1049 : {
1050 5 : return get_anon_bdev(&s->s_dev);
1051 : }
1052 : EXPORT_SYMBOL(set_anon_super);
1053 :
1054 98 : void kill_anon_super(struct super_block *sb)
1055 : {
1056 98 : dev_t dev = sb->s_dev;
1057 98 : generic_shutdown_super(sb);
1058 98 : free_anon_bdev(dev);
1059 98 : }
1060 : EXPORT_SYMBOL(kill_anon_super);
1061 :
1062 95 : void kill_litter_super(struct super_block *sb)
1063 : {
1064 95 : if (sb->s_root)
1065 95 : d_genocide(sb->s_root);
1066 95 : kill_anon_super(sb);
1067 95 : }
1068 : EXPORT_SYMBOL(kill_litter_super);
1069 :
1070 116 : int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
1071 : {
1072 116 : return set_anon_super(sb, NULL);
1073 : }
1074 : EXPORT_SYMBOL(set_anon_super_fc);
1075 :
1076 1 : static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
1077 : {
1078 1 : return sb->s_fs_info == fc->s_fs_info;
1079 : }
1080 :
1081 0 : static int test_single_super(struct super_block *s, struct fs_context *fc)
1082 : {
1083 0 : 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 : */
1111 114 : int 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 114 : int (*test)(struct super_block *, struct fs_context *);
1117 114 : struct super_block *sb;
1118 114 : int err;
1119 :
1120 114 : 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 0 : default:
1132 0 : BUG();
1133 : }
1134 :
1135 114 : sb = sget_fc(fc, test, set_anon_super_fc);
1136 114 : if (IS_ERR(sb))
1137 0 : return PTR_ERR(sb);
1138 :
1139 114 : if (!sb->s_root) {
1140 113 : err = fill_super(sb, fc);
1141 113 : if (err)
1142 0 : goto error;
1143 :
1144 113 : sb->s_flags |= SB_ACTIVE;
1145 226 : fc->root = dget(sb->s_root);
1146 : } else {
1147 1 : fc->root = dget(sb->s_root);
1148 1 : if (keying == vfs_get_single_reconf_super) {
1149 0 : err = reconfigure_super(fc);
1150 0 : if (err < 0) {
1151 0 : dput(fc->root);
1152 0 : fc->root = NULL;
1153 0 : goto error;
1154 : }
1155 : }
1156 : }
1157 :
1158 : return 0;
1159 :
1160 0 : error:
1161 0 : deactivate_locked_super(sb);
1162 0 : return err;
1163 : }
1164 : EXPORT_SYMBOL(vfs_get_super);
1165 :
1166 112 : int get_tree_nodev(struct fs_context *fc,
1167 : int (*fill_super)(struct super_block *sb,
1168 : struct fs_context *fc))
1169 : {
1170 112 : return vfs_get_super(fc, vfs_get_independent_super, fill_super);
1171 : }
1172 : EXPORT_SYMBOL(get_tree_nodev);
1173 :
1174 0 : int get_tree_single(struct fs_context *fc,
1175 : int (*fill_super)(struct super_block *sb,
1176 : struct fs_context *fc))
1177 : {
1178 0 : return vfs_get_super(fc, vfs_get_single_super, fill_super);
1179 : }
1180 : EXPORT_SYMBOL(get_tree_single);
1181 :
1182 0 : int get_tree_single_reconf(struct fs_context *fc,
1183 : int (*fill_super)(struct super_block *sb,
1184 : struct fs_context *fc))
1185 : {
1186 0 : return vfs_get_super(fc, vfs_get_single_reconf_super, fill_super);
1187 : }
1188 : EXPORT_SYMBOL(get_tree_single_reconf);
1189 :
1190 2 : int 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 2 : fc->s_fs_info = key;
1196 2 : return vfs_get_super(fc, vfs_get_keyed_super, fill_super);
1197 : }
1198 : EXPORT_SYMBOL(get_tree_keyed);
1199 :
1200 : #ifdef CONFIG_BLOCK
1201 :
1202 2 : static int set_bdev_super(struct super_block *s, void *data)
1203 : {
1204 2 : s->s_bdev = data;
1205 2 : s->s_dev = s->s_bdev->bd_dev;
1206 2 : s->s_bdi = bdi_get(s->s_bdev->bd_bdi);
1207 :
1208 2 : if (blk_queue_stable_writes(s->s_bdev->bd_disk->queue))
1209 0 : s->s_iflags |= SB_I_STABLE_WRITES;
1210 2 : return 0;
1211 : }
1212 :
1213 0 : static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1214 : {
1215 0 : return set_bdev_super(s, fc->sget_key);
1216 : }
1217 :
1218 0 : static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1219 : {
1220 0 : 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 : */
1228 0 : int get_tree_bdev(struct fs_context *fc,
1229 : int (*fill_super)(struct super_block *,
1230 : struct fs_context *))
1231 : {
1232 0 : struct block_device *bdev;
1233 0 : struct super_block *s;
1234 0 : fmode_t mode = FMODE_READ | FMODE_EXCL;
1235 0 : int error = 0;
1236 :
1237 0 : if (!(fc->sb_flags & SB_RDONLY))
1238 0 : mode |= FMODE_WRITE;
1239 :
1240 0 : if (!fc->source)
1241 0 : return invalf(fc, "No source specified");
1242 :
1243 0 : bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
1244 0 : if (IS_ERR(bdev)) {
1245 0 : errorf(fc, "%s: Can't open blockdev", fc->source);
1246 0 : 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 0 : mutex_lock(&bdev->bd_fsfreeze_mutex);
1254 0 : if (bdev->bd_fsfreeze_count > 0) {
1255 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1256 0 : warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
1257 0 : blkdev_put(bdev, mode);
1258 0 : return -EBUSY;
1259 : }
1260 :
1261 0 : fc->sb_flags |= SB_NOSEC;
1262 0 : fc->sget_key = bdev;
1263 0 : s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
1264 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1265 0 : if (IS_ERR(s)) {
1266 0 : blkdev_put(bdev, mode);
1267 0 : return PTR_ERR(s);
1268 : }
1269 :
1270 0 : if (s->s_root) {
1271 : /* Don't summarily change the RO/RW state. */
1272 0 : if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
1273 0 : warnf(fc, "%pg: Can't mount, would change RO state", bdev);
1274 0 : deactivate_locked_super(s);
1275 0 : blkdev_put(bdev, mode);
1276 0 : return -EBUSY;
1277 : }
1278 :
1279 : /*
1280 : * s_umount nests inside bd_mutex during
1281 : * __invalidate_device(). blkdev_put() acquires
1282 : * bd_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 0 : up_write(&s->s_umount);
1287 0 : blkdev_put(bdev, mode);
1288 0 : down_write(&s->s_umount);
1289 : } else {
1290 0 : s->s_mode = mode;
1291 0 : snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1292 0 : sb_set_blocksize(s, block_size(bdev));
1293 0 : error = fill_super(s, fc);
1294 0 : if (error) {
1295 0 : deactivate_locked_super(s);
1296 0 : return error;
1297 : }
1298 :
1299 0 : s->s_flags |= SB_ACTIVE;
1300 0 : bdev->bd_super = s;
1301 : }
1302 :
1303 0 : BUG_ON(fc->root);
1304 0 : fc->root = dget(s->s_root);
1305 0 : return 0;
1306 : }
1307 : EXPORT_SYMBOL(get_tree_bdev);
1308 :
1309 0 : static int test_bdev_super(struct super_block *s, void *data)
1310 : {
1311 0 : return (void *)s->s_bdev == data;
1312 : }
1313 :
1314 2 : struct 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 2 : struct block_device *bdev;
1319 2 : struct super_block *s;
1320 2 : fmode_t mode = FMODE_READ | FMODE_EXCL;
1321 2 : int error = 0;
1322 :
1323 2 : if (!(flags & SB_RDONLY))
1324 0 : mode |= FMODE_WRITE;
1325 :
1326 2 : bdev = blkdev_get_by_path(dev_name, mode, fs_type);
1327 2 : if (IS_ERR(bdev))
1328 2 : 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 2 : mutex_lock(&bdev->bd_fsfreeze_mutex);
1336 2 : if (bdev->bd_fsfreeze_count > 0) {
1337 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1338 0 : error = -EBUSY;
1339 0 : goto error_bdev;
1340 : }
1341 2 : s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC,
1342 : bdev);
1343 2 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1344 2 : if (IS_ERR(s))
1345 0 : goto error_s;
1346 :
1347 2 : if (s->s_root) {
1348 0 : if ((flags ^ s->s_flags) & SB_RDONLY) {
1349 0 : deactivate_locked_super(s);
1350 0 : error = -EBUSY;
1351 0 : goto error_bdev;
1352 : }
1353 :
1354 : /*
1355 : * s_umount nests inside bd_mutex during
1356 : * __invalidate_device(). blkdev_put() acquires
1357 : * bd_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 0 : up_write(&s->s_umount);
1362 0 : blkdev_put(bdev, mode);
1363 0 : down_write(&s->s_umount);
1364 : } else {
1365 2 : s->s_mode = mode;
1366 2 : snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1367 2 : sb_set_blocksize(s, block_size(bdev));
1368 2 : error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1369 2 : if (error) {
1370 1 : deactivate_locked_super(s);
1371 1 : goto error;
1372 : }
1373 :
1374 1 : s->s_flags |= SB_ACTIVE;
1375 1 : bdev->bd_super = s;
1376 : }
1377 :
1378 1 : return dget(s->s_root);
1379 :
1380 0 : error_s:
1381 0 : error = PTR_ERR(s);
1382 0 : error_bdev:
1383 0 : blkdev_put(bdev, mode);
1384 1 : error:
1385 1 : return ERR_PTR(error);
1386 : }
1387 : EXPORT_SYMBOL(mount_bdev);
1388 :
1389 1 : void kill_block_super(struct super_block *sb)
1390 : {
1391 1 : struct block_device *bdev = sb->s_bdev;
1392 1 : fmode_t mode = sb->s_mode;
1393 :
1394 1 : bdev->bd_super = NULL;
1395 1 : generic_shutdown_super(sb);
1396 1 : sync_blockdev(bdev);
1397 1 : WARN_ON_ONCE(!(mode & FMODE_EXCL));
1398 1 : blkdev_put(bdev, mode | FMODE_EXCL);
1399 1 : }
1400 :
1401 : EXPORT_SYMBOL(kill_block_super);
1402 : #endif
1403 :
1404 3 : struct 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 3 : int error;
1409 3 : struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1410 :
1411 3 : if (IS_ERR(s))
1412 3 : return ERR_CAST(s);
1413 :
1414 3 : error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1415 3 : if (error) {
1416 0 : deactivate_locked_super(s);
1417 0 : return ERR_PTR(error);
1418 : }
1419 3 : s->s_flags |= SB_ACTIVE;
1420 3 : return dget(s->s_root);
1421 : }
1422 : EXPORT_SYMBOL(mount_nodev);
1423 :
1424 1 : static int reconfigure_single(struct super_block *s,
1425 : int flags, void *data)
1426 : {
1427 1 : struct fs_context *fc;
1428 1 : 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 1 : fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
1436 1 : if (IS_ERR(fc))
1437 0 : return PTR_ERR(fc);
1438 :
1439 1 : ret = parse_monolithic_mount_data(fc, data);
1440 1 : if (ret < 0)
1441 0 : goto out;
1442 :
1443 1 : ret = reconfigure_super(fc);
1444 1 : out:
1445 1 : put_fs_context(fc);
1446 1 : return ret;
1447 : }
1448 :
1449 1 : static int compare_single(struct super_block *s, void *p)
1450 : {
1451 1 : return 1;
1452 : }
1453 :
1454 3 : struct 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 3 : struct super_block *s;
1459 3 : int error;
1460 :
1461 3 : s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1462 3 : if (IS_ERR(s))
1463 3 : return ERR_CAST(s);
1464 3 : if (!s->s_root) {
1465 2 : error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1466 2 : if (!error)
1467 2 : s->s_flags |= SB_ACTIVE;
1468 : } else {
1469 1 : error = reconfigure_single(s, flags, data);
1470 : }
1471 3 : if (unlikely(error)) {
1472 0 : deactivate_locked_super(s);
1473 0 : return ERR_PTR(error);
1474 : }
1475 3 : return dget(s->s_root);
1476 : }
1477 : EXPORT_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 : */
1487 128 : int vfs_get_tree(struct fs_context *fc)
1488 : {
1489 128 : struct super_block *sb;
1490 128 : int error;
1491 :
1492 128 : 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 128 : error = fc->ops->get_tree(fc);
1499 128 : if (error < 0)
1500 : return error;
1501 :
1502 127 : if (!fc->root) {
1503 0 : 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 0 : BUG();
1509 : }
1510 :
1511 127 : sb = fc->root->d_sb;
1512 127 : 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 127 : smp_wmb();
1521 127 : sb->s_flags |= SB_BORN;
1522 :
1523 127 : error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
1524 127 : if (unlikely(error)) {
1525 0 : fc_drop_locked(fc);
1526 0 : 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 127 : 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 : }
1540 : EXPORT_SYMBOL(vfs_get_tree);
1541 :
1542 : /*
1543 : * Setup private BDI for given superblock. It gets automatically cleaned up
1544 : * in generic_shutdown_super().
1545 : */
1546 0 : int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
1547 : {
1548 0 : struct backing_dev_info *bdi;
1549 0 : int err;
1550 0 : va_list args;
1551 :
1552 0 : bdi = bdi_alloc(NUMA_NO_NODE);
1553 0 : if (!bdi)
1554 : return -ENOMEM;
1555 :
1556 0 : va_start(args, fmt);
1557 0 : err = bdi_register_va(bdi, fmt, args);
1558 0 : va_end(args);
1559 0 : if (err) {
1560 0 : bdi_put(bdi);
1561 0 : return err;
1562 : }
1563 0 : WARN_ON(sb->s_bdi != &noop_backing_dev_info);
1564 0 : sb->s_bdi = bdi;
1565 :
1566 0 : return 0;
1567 : }
1568 : EXPORT_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 : */
1574 0 : int super_setup_bdi(struct super_block *sb)
1575 : {
1576 0 : static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
1577 :
1578 0 : return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
1579 : atomic_long_inc_return(&bdi_seq));
1580 : }
1581 : EXPORT_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 : */
1591 0 : static void sb_wait_write(struct super_block *sb, int level)
1592 : {
1593 0 : 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 : */
1600 0 : static void lockdep_sb_freeze_release(struct super_block *sb)
1601 : {
1602 0 : int level;
1603 :
1604 0 : for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1605 0 : percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1606 0 : }
1607 :
1608 : /*
1609 : * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1610 : */
1611 0 : static void lockdep_sb_freeze_acquire(struct super_block *sb)
1612 : {
1613 0 : int level;
1614 :
1615 0 : for (level = 0; level < SB_FREEZE_LEVELS; ++level)
1616 0 : percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1617 0 : }
1618 :
1619 0 : static void sb_freeze_unlock(struct super_block *sb)
1620 : {
1621 0 : int level;
1622 :
1623 0 : for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1624 0 : percpu_up_write(sb->s_writers.rw_sem + level);
1625 0 : }
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 : */
1660 0 : int freeze_super(struct super_block *sb)
1661 : {
1662 0 : int ret;
1663 :
1664 0 : atomic_inc(&sb->s_active);
1665 0 : down_write(&sb->s_umount);
1666 0 : if (sb->s_writers.frozen != SB_UNFROZEN) {
1667 0 : deactivate_locked_super(sb);
1668 0 : return -EBUSY;
1669 : }
1670 :
1671 0 : if (!(sb->s_flags & SB_BORN)) {
1672 0 : up_write(&sb->s_umount);
1673 0 : return 0; /* sic - it's "nothing to do" */
1674 : }
1675 :
1676 0 : if (sb_rdonly(sb)) {
1677 : /* Nothing to do really... */
1678 0 : sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1679 0 : up_write(&sb->s_umount);
1680 0 : return 0;
1681 : }
1682 :
1683 0 : sb->s_writers.frozen = SB_FREEZE_WRITE;
1684 : /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1685 0 : up_write(&sb->s_umount);
1686 0 : sb_wait_write(sb, SB_FREEZE_WRITE);
1687 0 : down_write(&sb->s_umount);
1688 :
1689 : /* Now we go and block page faults... */
1690 0 : sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
1691 0 : sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
1692 :
1693 : /* All writers are done so after syncing there won't be dirty data */
1694 0 : sync_filesystem(sb);
1695 :
1696 : /* Now wait for internal filesystem counter */
1697 0 : sb->s_writers.frozen = SB_FREEZE_FS;
1698 0 : sb_wait_write(sb, SB_FREEZE_FS);
1699 :
1700 0 : if (sb->s_op->freeze_fs) {
1701 0 : ret = sb->s_op->freeze_fs(sb);
1702 0 : if (ret) {
1703 0 : printk(KERN_ERR
1704 : "VFS:Filesystem freeze failed\n");
1705 0 : sb->s_writers.frozen = SB_UNFROZEN;
1706 0 : sb_freeze_unlock(sb);
1707 0 : wake_up(&sb->s_writers.wait_unfrozen);
1708 0 : deactivate_locked_super(sb);
1709 0 : 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 0 : sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1717 0 : lockdep_sb_freeze_release(sb);
1718 0 : up_write(&sb->s_umount);
1719 0 : return 0;
1720 : }
1721 : EXPORT_SYMBOL(freeze_super);
1722 :
1723 0 : static int thaw_super_locked(struct super_block *sb)
1724 : {
1725 0 : int error;
1726 :
1727 0 : if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
1728 0 : up_write(&sb->s_umount);
1729 0 : return -EINVAL;
1730 : }
1731 :
1732 0 : if (sb_rdonly(sb)) {
1733 0 : sb->s_writers.frozen = SB_UNFROZEN;
1734 0 : goto out;
1735 : }
1736 :
1737 0 : lockdep_sb_freeze_acquire(sb);
1738 :
1739 0 : if (sb->s_op->unfreeze_fs) {
1740 0 : error = sb->s_op->unfreeze_fs(sb);
1741 0 : if (error) {
1742 0 : printk(KERN_ERR
1743 : "VFS:Filesystem thaw failed\n");
1744 0 : lockdep_sb_freeze_release(sb);
1745 0 : up_write(&sb->s_umount);
1746 0 : return error;
1747 : }
1748 : }
1749 :
1750 0 : sb->s_writers.frozen = SB_UNFROZEN;
1751 0 : sb_freeze_unlock(sb);
1752 0 : out:
1753 0 : wake_up(&sb->s_writers.wait_unfrozen);
1754 0 : deactivate_locked_super(sb);
1755 0 : 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 : */
1764 0 : int thaw_super(struct super_block *sb)
1765 : {
1766 0 : down_write(&sb->s_umount);
1767 0 : return thaw_super_locked(sb);
1768 : }
1769 : EXPORT_SYMBOL(thaw_super);
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