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/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 :
42 : static int thaw_super_locked(struct super_block *sb);
43 :
44 : static LIST_HEAD(super_blocks);
45 : static DEFINE_SPINLOCK(sb_lock);
46 :
47 : static 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_mutex. Hence we
58 : * take a passive reference to the superblock to avoid this from occurring.
59 : */
60 0 : static unsigned long super_cache_scan(struct shrinker *shrink,
61 : struct shrink_control *sc)
62 : {
63 : struct super_block *sb;
64 0 : long fs_objects = 0;
65 : long total_objects;
66 0 : long freed = 0;
67 : long dentries;
68 : long inodes;
69 :
70 0 : 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 0 : if (!(sc->gfp_mask & __GFP_FS))
77 : return SHRINK_STOP;
78 :
79 0 : if (!trylock_super(sb))
80 : return SHRINK_STOP;
81 :
82 0 : if (sb->s_op->nr_cached_objects)
83 0 : fs_objects = sb->s_op->nr_cached_objects(sb, sc);
84 :
85 0 : inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
86 0 : dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
87 0 : total_objects = dentries + inodes + fs_objects + 1;
88 0 : if (!total_objects)
89 0 : total_objects = 1;
90 :
91 : /* proportion the scan between the caches */
92 0 : dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
93 0 : inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
94 0 : 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 0 : sc->nr_to_scan = dentries + 1;
104 0 : freed = prune_dcache_sb(sb, sc);
105 0 : sc->nr_to_scan = inodes + 1;
106 0 : freed += prune_icache_sb(sb, sc);
107 :
108 0 : if (fs_objects) {
109 0 : sc->nr_to_scan = fs_objects + 1;
110 0 : freed += sb->s_op->free_cached_objects(sb, sc);
111 : }
112 :
113 0 : up_read(&sb->s_umount);
114 0 : return freed;
115 : }
116 :
117 0 : static unsigned long super_cache_count(struct shrinker *shrink,
118 : struct shrink_control *sc)
119 : {
120 : struct super_block *sb;
121 0 : long total_objects = 0;
122 :
123 0 : 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 0 : if (!(sb->s_flags & SB_BORN))
140 : return 0;
141 0 : smp_rmb();
142 :
143 0 : if (sb->s_op && sb->s_op->nr_cached_objects)
144 0 : total_objects = sb->s_op->nr_cached_objects(sb, sc);
145 :
146 0 : total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
147 0 : total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
148 :
149 0 : if (!total_objects)
150 : return SHRINK_EMPTY;
151 :
152 0 : total_objects = vfs_pressure_ratio(total_objects);
153 0 : return total_objects;
154 : }
155 :
156 22 : static void destroy_super_work(struct work_struct *work)
157 : {
158 22 : struct super_block *s = container_of(work, struct super_block,
159 : destroy_work);
160 : int i;
161 :
162 88 : for (i = 0; i < SB_FREEZE_LEVELS; i++)
163 66 : percpu_free_rwsem(&s->s_writers.rw_sem[i]);
164 22 : kfree(s);
165 22 : }
166 :
167 22 : static void destroy_super_rcu(struct rcu_head *head)
168 : {
169 22 : struct super_block *s = container_of(head, struct super_block, rcu);
170 44 : INIT_WORK(&s->destroy_work, destroy_super_work);
171 44 : schedule_work(&s->destroy_work);
172 22 : }
173 :
174 : /* Free a superblock that has never been seen by anyone */
175 0 : static void destroy_unused_super(struct super_block *s)
176 : {
177 0 : if (!s)
178 : return;
179 0 : up_write(&s->s_umount);
180 0 : list_lru_destroy(&s->s_dentry_lru);
181 0 : list_lru_destroy(&s->s_inode_lru);
182 0 : security_sb_free(s);
183 0 : put_user_ns(s->s_user_ns);
184 0 : kfree(s->s_subtype);
185 0 : free_prealloced_shrinker(&s->s_shrink);
186 : /* no delays needed */
187 0 : 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 : */
199 32 : static struct super_block *alloc_super(struct file_system_type *type, int flags,
200 : struct user_namespace *user_ns)
201 : {
202 32 : struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
203 : static const struct super_operations default_op;
204 : int i;
205 :
206 32 : if (!s)
207 : return NULL;
208 :
209 64 : INIT_LIST_HEAD(&s->s_mounts);
210 32 : s->s_user_ns = get_user_ns(user_ns);
211 32 : 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 32 : down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
229 :
230 32 : if (security_sb_alloc(s))
231 : goto fail;
232 :
233 128 : for (i = 0; i < SB_FREEZE_LEVELS; i++) {
234 192 : if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
235 96 : sb_writers_name[i],
236 : &type->s_writers_key[i]))
237 : goto fail;
238 : }
239 32 : init_waitqueue_head(&s->s_writers.wait_unfrozen);
240 32 : s->s_bdi = &noop_backing_dev_info;
241 32 : s->s_flags = flags;
242 32 : if (s->s_user_ns != &init_user_ns)
243 0 : s->s_iflags |= SB_I_NODEV;
244 64 : INIT_HLIST_NODE(&s->s_instances);
245 32 : INIT_HLIST_BL_HEAD(&s->s_roots);
246 32 : mutex_init(&s->s_sync_lock);
247 64 : INIT_LIST_HEAD(&s->s_inodes);
248 32 : spin_lock_init(&s->s_inode_list_lock);
249 64 : INIT_LIST_HEAD(&s->s_inodes_wb);
250 32 : spin_lock_init(&s->s_inode_wblist_lock);
251 :
252 32 : s->s_count = 1;
253 64 : atomic_set(&s->s_active, 1);
254 32 : mutex_init(&s->s_vfs_rename_mutex);
255 : lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
256 32 : init_rwsem(&s->s_dquot.dqio_sem);
257 32 : s->s_maxbytes = MAX_NON_LFS;
258 32 : s->s_op = &default_op;
259 32 : s->s_time_gran = 1000000000;
260 32 : s->s_time_min = TIME64_MIN;
261 32 : s->s_time_max = TIME64_MAX;
262 :
263 32 : s->s_shrink.seeks = DEFAULT_SEEKS;
264 32 : s->s_shrink.scan_objects = super_cache_scan;
265 32 : s->s_shrink.count_objects = super_cache_count;
266 32 : s->s_shrink.batch = 1024;
267 32 : s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
268 32 : if (prealloc_shrinker(&s->s_shrink, "sb-%s", type->name))
269 : goto fail;
270 32 : if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink))
271 : goto fail;
272 32 : if (list_lru_init_memcg(&s->s_inode_lru, &s->s_shrink))
273 : goto fail;
274 : return s;
275 :
276 : fail:
277 0 : 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 : */
286 22 : static void __put_super(struct super_block *s)
287 : {
288 22 : if (!--s->s_count) {
289 44 : list_del_init(&s->s_list);
290 22 : WARN_ON(s->s_dentry_lru.node);
291 22 : WARN_ON(s->s_inode_lru.node);
292 22 : WARN_ON(!list_empty(&s->s_mounts));
293 22 : security_sb_free(s);
294 22 : put_user_ns(s->s_user_ns);
295 22 : kfree(s->s_subtype);
296 22 : call_rcu(&s->rcu, destroy_super_rcu);
297 : }
298 22 : }
299 :
300 : /**
301 : * put_super - drop a temporary reference to superblock
302 : * @sb: superblock in question
303 : *
304 : * Drops a temporary reference, frees superblock if there's no
305 : * references left.
306 : */
307 0 : void put_super(struct super_block *sb)
308 : {
309 22 : spin_lock(&sb_lock);
310 22 : __put_super(sb);
311 22 : spin_unlock(&sb_lock);
312 0 : }
313 :
314 :
315 : /**
316 : * deactivate_locked_super - drop an active reference to superblock
317 : * @s: superblock to deactivate
318 : *
319 : * Drops an active reference to superblock, converting it into a temporary
320 : * one if there is no other active references left. In that case we
321 : * tell fs driver to shut it down and drop the temporary reference we
322 : * had just acquired.
323 : *
324 : * Caller holds exclusive lock on superblock; that lock is released.
325 : */
326 22 : void deactivate_locked_super(struct super_block *s)
327 : {
328 22 : struct file_system_type *fs = s->s_type;
329 44 : if (atomic_dec_and_test(&s->s_active)) {
330 22 : unregister_shrinker(&s->s_shrink);
331 22 : fs->kill_sb(s);
332 :
333 : /*
334 : * Since list_lru_destroy() may sleep, we cannot call it from
335 : * put_super(), where we hold the sb_lock. Therefore we destroy
336 : * the lru lists right now.
337 : */
338 22 : list_lru_destroy(&s->s_dentry_lru);
339 22 : list_lru_destroy(&s->s_inode_lru);
340 :
341 22 : put_filesystem(fs);
342 : put_super(s);
343 : } else {
344 0 : up_write(&s->s_umount);
345 : }
346 22 : }
347 :
348 : EXPORT_SYMBOL(deactivate_locked_super);
349 :
350 : /**
351 : * deactivate_super - drop an active reference to superblock
352 : * @s: superblock to deactivate
353 : *
354 : * Variant of deactivate_locked_super(), except that superblock is *not*
355 : * locked by caller. If we are going to drop the final active reference,
356 : * lock will be acquired prior to that.
357 : */
358 54 : void deactivate_super(struct super_block *s)
359 : {
360 108 : if (!atomic_add_unless(&s->s_active, -1, 1)) {
361 22 : down_write(&s->s_umount);
362 22 : deactivate_locked_super(s);
363 : }
364 54 : }
365 :
366 : EXPORT_SYMBOL(deactivate_super);
367 :
368 : /**
369 : * grab_super - acquire an active reference
370 : * @s: reference we are trying to make active
371 : *
372 : * Tries to acquire an active reference. grab_super() is used when we
373 : * had just found a superblock in super_blocks or fs_type->fs_supers
374 : * and want to turn it into a full-blown active reference. grab_super()
375 : * is called with sb_lock held and drops it. Returns 1 in case of
376 : * success, 0 if we had failed (superblock contents was already dead or
377 : * dying when grab_super() had been called). Note that this is only
378 : * called for superblocks not in rundown mode (== ones still on ->fs_supers
379 : * of their type), so increment of ->s_count is OK here.
380 : */
381 0 : static int grab_super(struct super_block *s) __releases(sb_lock)
382 : {
383 0 : s->s_count++;
384 0 : spin_unlock(&sb_lock);
385 0 : down_write(&s->s_umount);
386 0 : if ((s->s_flags & SB_BORN) && atomic_inc_not_zero(&s->s_active)) {
387 0 : put_super(s);
388 0 : return 1;
389 : }
390 0 : up_write(&s->s_umount);
391 0 : put_super(s);
392 0 : return 0;
393 : }
394 :
395 : /*
396 : * trylock_super - try to grab ->s_umount shared
397 : * @sb: reference we are trying to grab
398 : *
399 : * Try to prevent fs shutdown. This is used in places where we
400 : * cannot take an active reference but we need to ensure that the
401 : * filesystem is not shut down while we are working on it. It returns
402 : * false if we cannot acquire s_umount or if we lose the race and
403 : * filesystem already got into shutdown, and returns true with the s_umount
404 : * lock held in read mode in case of success. On successful return,
405 : * the caller must drop the s_umount lock when done.
406 : *
407 : * Note that unlike get_super() et.al. this one does *not* bump ->s_count.
408 : * The reason why it's safe is that we are OK with doing trylock instead
409 : * of down_read(). There's a couple of places that are OK with that, but
410 : * it's very much not a general-purpose interface.
411 : */
412 0 : bool trylock_super(struct super_block *sb)
413 : {
414 0 : if (down_read_trylock(&sb->s_umount)) {
415 0 : if (!hlist_unhashed(&sb->s_instances) &&
416 0 : sb->s_root && (sb->s_flags & SB_BORN))
417 : return true;
418 0 : up_read(&sb->s_umount);
419 : }
420 :
421 : return false;
422 : }
423 :
424 : /**
425 : * retire_super - prevents superblock from being reused
426 : * @sb: superblock to retire
427 : *
428 : * The function marks superblock to be ignored in superblock test, which
429 : * prevents it from being reused for any new mounts. If the superblock has
430 : * a private bdi, it also unregisters it, but doesn't reduce the refcount
431 : * of the superblock to prevent potential races. The refcount is reduced
432 : * by generic_shutdown_super(). The function can not be called
433 : * concurrently with generic_shutdown_super(). It is safe to call the
434 : * function multiple times, subsequent calls have no effect.
435 : *
436 : * The marker will affect the re-use only for block-device-based
437 : * superblocks. Other superblocks will still get marked if this function
438 : * is used, but that will not affect their reusability.
439 : */
440 0 : void retire_super(struct super_block *sb)
441 : {
442 0 : WARN_ON(!sb->s_bdev);
443 0 : down_write(&sb->s_umount);
444 0 : if (sb->s_iflags & SB_I_PERSB_BDI) {
445 0 : bdi_unregister(sb->s_bdi);
446 0 : sb->s_iflags &= ~SB_I_PERSB_BDI;
447 : }
448 0 : sb->s_iflags |= SB_I_RETIRED;
449 0 : up_write(&sb->s_umount);
450 0 : }
451 : EXPORT_SYMBOL(retire_super);
452 :
453 : /**
454 : * generic_shutdown_super - common helper for ->kill_sb()
455 : * @sb: superblock to kill
456 : *
457 : * generic_shutdown_super() does all fs-independent work on superblock
458 : * shutdown. Typical ->kill_sb() should pick all fs-specific objects
459 : * that need destruction out of superblock, call generic_shutdown_super()
460 : * and release aforementioned objects. Note: dentries and inodes _are_
461 : * taken care of and do not need specific handling.
462 : *
463 : * Upon calling this function, the filesystem may no longer alter or
464 : * rearrange the set of dentries belonging to this super_block, nor may it
465 : * change the attachments of dentries to inodes.
466 : */
467 22 : void generic_shutdown_super(struct super_block *sb)
468 : {
469 22 : const struct super_operations *sop = sb->s_op;
470 :
471 22 : if (sb->s_root) {
472 22 : shrink_dcache_for_umount(sb);
473 22 : sync_filesystem(sb);
474 22 : sb->s_flags &= ~SB_ACTIVE;
475 :
476 : cgroup_writeback_umount();
477 :
478 : /* Evict all inodes with zero refcount. */
479 22 : evict_inodes(sb);
480 :
481 : /*
482 : * Clean up and evict any inodes that still have references due
483 : * to fsnotify or the security policy.
484 : */
485 22 : fsnotify_sb_delete(sb);
486 22 : security_sb_delete(sb);
487 :
488 : /*
489 : * Now that all potentially-encrypted inodes have been evicted,
490 : * the fscrypt keyring can be destroyed.
491 : */
492 22 : fscrypt_destroy_keyring(sb);
493 :
494 22 : if (sb->s_dio_done_wq) {
495 0 : destroy_workqueue(sb->s_dio_done_wq);
496 0 : sb->s_dio_done_wq = NULL;
497 : }
498 :
499 22 : if (sop->put_super)
500 0 : sop->put_super(sb);
501 :
502 44 : if (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes),
503 : "VFS: Busy inodes after unmount of %s (%s)",
504 : sb->s_id, sb->s_type->name)) {
505 : /*
506 : * Adding a proper bailout path here would be hard, but
507 : * we can at least make it more likely that a later
508 : * iput_final() or such crashes cleanly.
509 : */
510 : struct inode *inode;
511 :
512 0 : spin_lock(&sb->s_inode_list_lock);
513 0 : list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
514 0 : inode->i_op = VFS_PTR_POISON;
515 0 : inode->i_sb = VFS_PTR_POISON;
516 0 : inode->i_mapping = VFS_PTR_POISON;
517 : }
518 0 : spin_unlock(&sb->s_inode_list_lock);
519 : }
520 : }
521 22 : spin_lock(&sb_lock);
522 : /* should be initialized for __put_super_and_need_restart() */
523 44 : hlist_del_init(&sb->s_instances);
524 22 : spin_unlock(&sb_lock);
525 22 : up_write(&sb->s_umount);
526 22 : if (sb->s_bdi != &noop_backing_dev_info) {
527 0 : if (sb->s_iflags & SB_I_PERSB_BDI)
528 0 : bdi_unregister(sb->s_bdi);
529 0 : bdi_put(sb->s_bdi);
530 0 : sb->s_bdi = &noop_backing_dev_info;
531 : }
532 22 : }
533 :
534 : EXPORT_SYMBOL(generic_shutdown_super);
535 :
536 0 : bool mount_capable(struct fs_context *fc)
537 : {
538 0 : if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT))
539 0 : return capable(CAP_SYS_ADMIN);
540 : else
541 0 : return ns_capable(fc->user_ns, CAP_SYS_ADMIN);
542 : }
543 :
544 : /**
545 : * sget_fc - Find or create a superblock
546 : * @fc: Filesystem context.
547 : * @test: Comparison callback
548 : * @set: Setup callback
549 : *
550 : * Find or create a superblock using the parameters stored in the filesystem
551 : * context and the two callback functions.
552 : *
553 : * If an extant superblock is matched, then that will be returned with an
554 : * elevated reference count that the caller must transfer or discard.
555 : *
556 : * If no match is made, a new superblock will be allocated and basic
557 : * initialisation will be performed (s_type, s_fs_info and s_id will be set and
558 : * the set() callback will be invoked), the superblock will be published and it
559 : * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
560 : * as yet unset.
561 : */
562 32 : struct super_block *sget_fc(struct fs_context *fc,
563 : int (*test)(struct super_block *, struct fs_context *),
564 : int (*set)(struct super_block *, struct fs_context *))
565 : {
566 32 : struct super_block *s = NULL;
567 : struct super_block *old;
568 32 : struct user_namespace *user_ns = fc->global ? &init_user_ns : fc->user_ns;
569 : int err;
570 :
571 : retry:
572 64 : spin_lock(&sb_lock);
573 64 : if (test) {
574 0 : hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
575 0 : if (test(old, fc))
576 : goto share_extant_sb;
577 : }
578 : }
579 64 : if (!s) {
580 32 : spin_unlock(&sb_lock);
581 32 : s = alloc_super(fc->fs_type, fc->sb_flags, user_ns);
582 32 : if (!s)
583 : return ERR_PTR(-ENOMEM);
584 : goto retry;
585 : }
586 :
587 32 : s->s_fs_info = fc->s_fs_info;
588 32 : err = set(s, fc);
589 32 : if (err) {
590 0 : s->s_fs_info = NULL;
591 0 : spin_unlock(&sb_lock);
592 0 : destroy_unused_super(s);
593 0 : return ERR_PTR(err);
594 : }
595 32 : fc->s_fs_info = NULL;
596 32 : s->s_type = fc->fs_type;
597 32 : s->s_iflags |= fc->s_iflags;
598 32 : strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
599 64 : list_add_tail(&s->s_list, &super_blocks);
600 64 : hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
601 32 : spin_unlock(&sb_lock);
602 32 : get_filesystem(s->s_type);
603 32 : register_shrinker_prepared(&s->s_shrink);
604 32 : return s;
605 :
606 : share_extant_sb:
607 0 : if (user_ns != old->s_user_ns) {
608 0 : spin_unlock(&sb_lock);
609 0 : destroy_unused_super(s);
610 0 : return ERR_PTR(-EBUSY);
611 : }
612 0 : if (!grab_super(old))
613 : goto retry;
614 0 : destroy_unused_super(s);
615 0 : return old;
616 : }
617 : EXPORT_SYMBOL(sget_fc);
618 :
619 : /**
620 : * sget - find or create a superblock
621 : * @type: filesystem type superblock should belong to
622 : * @test: comparison callback
623 : * @set: setup callback
624 : * @flags: mount flags
625 : * @data: argument to each of them
626 : */
627 0 : struct super_block *sget(struct file_system_type *type,
628 : int (*test)(struct super_block *,void *),
629 : int (*set)(struct super_block *,void *),
630 : int flags,
631 : void *data)
632 : {
633 0 : struct user_namespace *user_ns = current_user_ns();
634 0 : struct super_block *s = NULL;
635 : struct super_block *old;
636 : int err;
637 :
638 : /* We don't yet pass the user namespace of the parent
639 : * mount through to here so always use &init_user_ns
640 : * until that changes.
641 : */
642 : if (flags & SB_SUBMOUNT)
643 : user_ns = &init_user_ns;
644 :
645 : retry:
646 0 : spin_lock(&sb_lock);
647 0 : if (test) {
648 0 : hlist_for_each_entry(old, &type->fs_supers, s_instances) {
649 0 : if (!test(old, data))
650 0 : continue;
651 0 : if (user_ns != old->s_user_ns) {
652 0 : spin_unlock(&sb_lock);
653 0 : destroy_unused_super(s);
654 0 : return ERR_PTR(-EBUSY);
655 : }
656 0 : if (!grab_super(old))
657 : goto retry;
658 0 : destroy_unused_super(s);
659 0 : return old;
660 : }
661 : }
662 0 : if (!s) {
663 0 : spin_unlock(&sb_lock);
664 0 : s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
665 0 : if (!s)
666 : return ERR_PTR(-ENOMEM);
667 : goto retry;
668 : }
669 :
670 0 : err = set(s, data);
671 0 : if (err) {
672 0 : spin_unlock(&sb_lock);
673 0 : destroy_unused_super(s);
674 0 : return ERR_PTR(err);
675 : }
676 0 : s->s_type = type;
677 0 : strlcpy(s->s_id, type->name, sizeof(s->s_id));
678 0 : list_add_tail(&s->s_list, &super_blocks);
679 0 : hlist_add_head(&s->s_instances, &type->fs_supers);
680 0 : spin_unlock(&sb_lock);
681 0 : get_filesystem(type);
682 0 : register_shrinker_prepared(&s->s_shrink);
683 0 : return s;
684 : }
685 : EXPORT_SYMBOL(sget);
686 :
687 0 : void drop_super(struct super_block *sb)
688 : {
689 0 : up_read(&sb->s_umount);
690 0 : put_super(sb);
691 0 : }
692 :
693 : EXPORT_SYMBOL(drop_super);
694 :
695 0 : void drop_super_exclusive(struct super_block *sb)
696 : {
697 0 : up_write(&sb->s_umount);
698 0 : put_super(sb);
699 0 : }
700 : EXPORT_SYMBOL(drop_super_exclusive);
701 :
702 0 : static void __iterate_supers(void (*f)(struct super_block *))
703 : {
704 0 : struct super_block *sb, *p = NULL;
705 :
706 0 : spin_lock(&sb_lock);
707 0 : list_for_each_entry(sb, &super_blocks, s_list) {
708 0 : if (hlist_unhashed(&sb->s_instances))
709 0 : continue;
710 0 : sb->s_count++;
711 0 : spin_unlock(&sb_lock);
712 :
713 0 : f(sb);
714 :
715 0 : spin_lock(&sb_lock);
716 0 : if (p)
717 0 : __put_super(p);
718 : p = sb;
719 : }
720 0 : if (p)
721 0 : __put_super(p);
722 0 : spin_unlock(&sb_lock);
723 0 : }
724 : /**
725 : * iterate_supers - call function for all active superblocks
726 : * @f: function to call
727 : * @arg: argument to pass to it
728 : *
729 : * Scans the superblock list and calls given function, passing it
730 : * locked superblock and given argument.
731 : */
732 0 : void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
733 : {
734 0 : struct super_block *sb, *p = NULL;
735 :
736 0 : spin_lock(&sb_lock);
737 0 : list_for_each_entry(sb, &super_blocks, s_list) {
738 0 : if (hlist_unhashed(&sb->s_instances))
739 0 : continue;
740 0 : sb->s_count++;
741 0 : spin_unlock(&sb_lock);
742 :
743 0 : down_read(&sb->s_umount);
744 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
745 0 : f(sb, arg);
746 0 : up_read(&sb->s_umount);
747 :
748 0 : spin_lock(&sb_lock);
749 0 : if (p)
750 0 : __put_super(p);
751 : p = sb;
752 : }
753 0 : if (p)
754 0 : __put_super(p);
755 0 : spin_unlock(&sb_lock);
756 0 : }
757 :
758 : /**
759 : * iterate_supers_type - call function for superblocks of given type
760 : * @type: fs type
761 : * @f: function to call
762 : * @arg: argument to pass to it
763 : *
764 : * Scans the superblock list and calls given function, passing it
765 : * locked superblock and given argument.
766 : */
767 0 : void iterate_supers_type(struct file_system_type *type,
768 : void (*f)(struct super_block *, void *), void *arg)
769 : {
770 0 : struct super_block *sb, *p = NULL;
771 :
772 0 : spin_lock(&sb_lock);
773 0 : hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
774 0 : sb->s_count++;
775 0 : spin_unlock(&sb_lock);
776 :
777 0 : down_read(&sb->s_umount);
778 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
779 0 : f(sb, arg);
780 0 : up_read(&sb->s_umount);
781 :
782 0 : spin_lock(&sb_lock);
783 0 : if (p)
784 0 : __put_super(p);
785 0 : p = sb;
786 : }
787 0 : if (p)
788 0 : __put_super(p);
789 0 : spin_unlock(&sb_lock);
790 0 : }
791 :
792 : EXPORT_SYMBOL(iterate_supers_type);
793 :
794 : /**
795 : * get_super - get the superblock of a device
796 : * @bdev: device to get the superblock for
797 : *
798 : * Scans the superblock list and finds the superblock of the file system
799 : * mounted on the device given. %NULL is returned if no match is found.
800 : */
801 0 : struct super_block *get_super(struct block_device *bdev)
802 : {
803 : struct super_block *sb;
804 :
805 0 : if (!bdev)
806 : return NULL;
807 :
808 : spin_lock(&sb_lock);
809 : rescan:
810 0 : list_for_each_entry(sb, &super_blocks, s_list) {
811 0 : if (hlist_unhashed(&sb->s_instances))
812 0 : continue;
813 0 : if (sb->s_bdev == bdev) {
814 0 : sb->s_count++;
815 0 : spin_unlock(&sb_lock);
816 0 : down_read(&sb->s_umount);
817 : /* still alive? */
818 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
819 : return sb;
820 0 : up_read(&sb->s_umount);
821 : /* nope, got unmounted */
822 0 : spin_lock(&sb_lock);
823 0 : __put_super(sb);
824 0 : goto rescan;
825 : }
826 : }
827 0 : spin_unlock(&sb_lock);
828 0 : return NULL;
829 : }
830 :
831 : /**
832 : * get_active_super - get an active reference to the superblock of a device
833 : * @bdev: device to get the superblock for
834 : *
835 : * Scans the superblock list and finds the superblock of the file system
836 : * mounted on the device given. Returns the superblock with an active
837 : * reference or %NULL if none was found.
838 : */
839 0 : struct super_block *get_active_super(struct block_device *bdev)
840 : {
841 : struct super_block *sb;
842 :
843 0 : if (!bdev)
844 : return NULL;
845 :
846 : restart:
847 0 : spin_lock(&sb_lock);
848 0 : list_for_each_entry(sb, &super_blocks, s_list) {
849 0 : if (hlist_unhashed(&sb->s_instances))
850 0 : continue;
851 0 : if (sb->s_bdev == bdev) {
852 0 : if (!grab_super(sb))
853 : goto restart;
854 0 : up_write(&sb->s_umount);
855 0 : return sb;
856 : }
857 : }
858 0 : spin_unlock(&sb_lock);
859 0 : return NULL;
860 : }
861 :
862 0 : struct super_block *user_get_super(dev_t dev, bool excl)
863 : {
864 : struct super_block *sb;
865 :
866 : spin_lock(&sb_lock);
867 : rescan:
868 0 : list_for_each_entry(sb, &super_blocks, s_list) {
869 0 : if (hlist_unhashed(&sb->s_instances))
870 0 : continue;
871 0 : if (sb->s_dev == dev) {
872 0 : sb->s_count++;
873 0 : spin_unlock(&sb_lock);
874 0 : if (excl)
875 0 : down_write(&sb->s_umount);
876 : else
877 0 : down_read(&sb->s_umount);
878 : /* still alive? */
879 0 : if (sb->s_root && (sb->s_flags & SB_BORN))
880 : return sb;
881 0 : if (excl)
882 0 : up_write(&sb->s_umount);
883 : else
884 0 : up_read(&sb->s_umount);
885 : /* nope, got unmounted */
886 0 : spin_lock(&sb_lock);
887 0 : __put_super(sb);
888 0 : goto rescan;
889 : }
890 : }
891 0 : spin_unlock(&sb_lock);
892 0 : return NULL;
893 : }
894 :
895 : /**
896 : * reconfigure_super - asks filesystem to change superblock parameters
897 : * @fc: The superblock and configuration
898 : *
899 : * Alters the configuration parameters of a live superblock.
900 : */
901 0 : int reconfigure_super(struct fs_context *fc)
902 : {
903 0 : struct super_block *sb = fc->root->d_sb;
904 : int retval;
905 0 : bool remount_ro = false;
906 0 : bool force = fc->sb_flags & SB_FORCE;
907 :
908 0 : if (fc->sb_flags_mask & ~MS_RMT_MASK)
909 : return -EINVAL;
910 0 : if (sb->s_writers.frozen != SB_UNFROZEN)
911 : return -EBUSY;
912 :
913 0 : retval = security_sb_remount(sb, fc->security);
914 : if (retval)
915 : return retval;
916 :
917 0 : if (fc->sb_flags_mask & SB_RDONLY) {
918 : #ifdef CONFIG_BLOCK
919 0 : if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&
920 0 : bdev_read_only(sb->s_bdev))
921 : return -EACCES;
922 : #endif
923 :
924 0 : remount_ro = (fc->sb_flags & SB_RDONLY) && !sb_rdonly(sb);
925 : }
926 :
927 0 : if (remount_ro) {
928 0 : if (!hlist_empty(&sb->s_pins)) {
929 0 : up_write(&sb->s_umount);
930 0 : group_pin_kill(&sb->s_pins);
931 0 : down_write(&sb->s_umount);
932 0 : if (!sb->s_root)
933 : return 0;
934 0 : if (sb->s_writers.frozen != SB_UNFROZEN)
935 : return -EBUSY;
936 0 : remount_ro = !sb_rdonly(sb);
937 : }
938 : }
939 0 : shrink_dcache_sb(sb);
940 :
941 : /* If we are reconfiguring to RDONLY and current sb is read/write,
942 : * make sure there are no files open for writing.
943 : */
944 0 : if (remount_ro) {
945 0 : if (force) {
946 0 : sb->s_readonly_remount = 1;
947 0 : smp_wmb();
948 : } else {
949 0 : retval = sb_prepare_remount_readonly(sb);
950 0 : if (retval)
951 : return retval;
952 : }
953 : }
954 :
955 0 : if (fc->ops->reconfigure) {
956 0 : retval = fc->ops->reconfigure(fc);
957 0 : if (retval) {
958 0 : if (!force)
959 : goto cancel_readonly;
960 : /* If forced remount, go ahead despite any errors */
961 0 : WARN(1, "forced remount of a %s fs returned %i\n",
962 : sb->s_type->name, retval);
963 : }
964 : }
965 :
966 0 : WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) |
967 : (fc->sb_flags & fc->sb_flags_mask)));
968 : /* Needs to be ordered wrt mnt_is_readonly() */
969 0 : smp_wmb();
970 0 : sb->s_readonly_remount = 0;
971 :
972 : /*
973 : * Some filesystems modify their metadata via some other path than the
974 : * bdev buffer cache (eg. use a private mapping, or directories in
975 : * pagecache, etc). Also file data modifications go via their own
976 : * mappings. So If we try to mount readonly then copy the filesystem
977 : * from bdev, we could get stale data, so invalidate it to give a best
978 : * effort at coherency.
979 : */
980 0 : if (remount_ro && sb->s_bdev)
981 0 : invalidate_bdev(sb->s_bdev);
982 : return 0;
983 :
984 : cancel_readonly:
985 0 : sb->s_readonly_remount = 0;
986 0 : return retval;
987 : }
988 :
989 0 : static void do_emergency_remount_callback(struct super_block *sb)
990 : {
991 0 : down_write(&sb->s_umount);
992 0 : if (sb->s_root && sb->s_bdev && (sb->s_flags & SB_BORN) &&
993 0 : !sb_rdonly(sb)) {
994 : struct fs_context *fc;
995 :
996 0 : fc = fs_context_for_reconfigure(sb->s_root,
997 : SB_RDONLY | SB_FORCE, SB_RDONLY);
998 0 : if (!IS_ERR(fc)) {
999 0 : if (parse_monolithic_mount_data(fc, NULL) == 0)
1000 0 : (void)reconfigure_super(fc);
1001 0 : put_fs_context(fc);
1002 : }
1003 : }
1004 0 : up_write(&sb->s_umount);
1005 0 : }
1006 :
1007 0 : static void do_emergency_remount(struct work_struct *work)
1008 : {
1009 0 : __iterate_supers(do_emergency_remount_callback);
1010 0 : kfree(work);
1011 0 : printk("Emergency Remount complete\n");
1012 0 : }
1013 :
1014 0 : void emergency_remount(void)
1015 : {
1016 : struct work_struct *work;
1017 :
1018 0 : work = kmalloc(sizeof(*work), GFP_ATOMIC);
1019 0 : if (work) {
1020 0 : INIT_WORK(work, do_emergency_remount);
1021 : schedule_work(work);
1022 : }
1023 0 : }
1024 :
1025 0 : static void do_thaw_all_callback(struct super_block *sb)
1026 : {
1027 0 : down_write(&sb->s_umount);
1028 0 : if (sb->s_root && sb->s_flags & SB_BORN) {
1029 0 : emergency_thaw_bdev(sb);
1030 0 : thaw_super_locked(sb);
1031 : } else {
1032 0 : up_write(&sb->s_umount);
1033 : }
1034 0 : }
1035 :
1036 0 : static void do_thaw_all(struct work_struct *work)
1037 : {
1038 0 : __iterate_supers(do_thaw_all_callback);
1039 0 : kfree(work);
1040 0 : printk(KERN_WARNING "Emergency Thaw complete\n");
1041 0 : }
1042 :
1043 : /**
1044 : * emergency_thaw_all -- forcibly thaw every frozen filesystem
1045 : *
1046 : * Used for emergency unfreeze of all filesystems via SysRq
1047 : */
1048 0 : void emergency_thaw_all(void)
1049 : {
1050 : struct work_struct *work;
1051 :
1052 0 : work = kmalloc(sizeof(*work), GFP_ATOMIC);
1053 0 : if (work) {
1054 0 : INIT_WORK(work, do_thaw_all);
1055 : schedule_work(work);
1056 : }
1057 0 : }
1058 :
1059 : static DEFINE_IDA(unnamed_dev_ida);
1060 :
1061 : /**
1062 : * get_anon_bdev - Allocate a block device for filesystems which don't have one.
1063 : * @p: Pointer to a dev_t.
1064 : *
1065 : * Filesystems which don't use real block devices can call this function
1066 : * to allocate a virtual block device.
1067 : *
1068 : * Context: Any context. Frequently called while holding sb_lock.
1069 : * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
1070 : * or -ENOMEM if memory allocation failed.
1071 : */
1072 32 : int get_anon_bdev(dev_t *p)
1073 : {
1074 : int dev;
1075 :
1076 : /*
1077 : * Many userspace utilities consider an FSID of 0 invalid.
1078 : * Always return at least 1 from get_anon_bdev.
1079 : */
1080 32 : dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
1081 : GFP_ATOMIC);
1082 32 : if (dev == -ENOSPC)
1083 0 : dev = -EMFILE;
1084 32 : if (dev < 0)
1085 : return dev;
1086 :
1087 32 : *p = MKDEV(0, dev);
1088 32 : return 0;
1089 : }
1090 : EXPORT_SYMBOL(get_anon_bdev);
1091 :
1092 0 : void free_anon_bdev(dev_t dev)
1093 : {
1094 22 : ida_free(&unnamed_dev_ida, MINOR(dev));
1095 0 : }
1096 : EXPORT_SYMBOL(free_anon_bdev);
1097 :
1098 0 : int set_anon_super(struct super_block *s, void *data)
1099 : {
1100 32 : return get_anon_bdev(&s->s_dev);
1101 : }
1102 : EXPORT_SYMBOL(set_anon_super);
1103 :
1104 22 : void kill_anon_super(struct super_block *sb)
1105 : {
1106 22 : dev_t dev = sb->s_dev;
1107 22 : generic_shutdown_super(sb);
1108 22 : free_anon_bdev(dev);
1109 22 : }
1110 : EXPORT_SYMBOL(kill_anon_super);
1111 :
1112 0 : void kill_litter_super(struct super_block *sb)
1113 : {
1114 0 : if (sb->s_root)
1115 0 : d_genocide(sb->s_root);
1116 0 : kill_anon_super(sb);
1117 0 : }
1118 : EXPORT_SYMBOL(kill_litter_super);
1119 :
1120 32 : int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
1121 : {
1122 32 : return set_anon_super(sb, NULL);
1123 : }
1124 : EXPORT_SYMBOL(set_anon_super_fc);
1125 :
1126 0 : static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
1127 : {
1128 0 : return sb->s_fs_info == fc->s_fs_info;
1129 : }
1130 :
1131 0 : static int test_single_super(struct super_block *s, struct fs_context *fc)
1132 : {
1133 0 : return 1;
1134 : }
1135 :
1136 32 : static int vfs_get_super(struct fs_context *fc, bool reconf,
1137 : int (*test)(struct super_block *, struct fs_context *),
1138 : int (*fill_super)(struct super_block *sb,
1139 : struct fs_context *fc))
1140 : {
1141 : struct super_block *sb;
1142 : int err;
1143 :
1144 32 : sb = sget_fc(fc, test, set_anon_super_fc);
1145 32 : if (IS_ERR(sb))
1146 0 : return PTR_ERR(sb);
1147 :
1148 32 : if (!sb->s_root) {
1149 32 : err = fill_super(sb, fc);
1150 32 : if (err)
1151 : goto error;
1152 :
1153 32 : sb->s_flags |= SB_ACTIVE;
1154 64 : fc->root = dget(sb->s_root);
1155 : } else {
1156 0 : fc->root = dget(sb->s_root);
1157 0 : if (reconf) {
1158 0 : err = reconfigure_super(fc);
1159 0 : if (err < 0) {
1160 0 : dput(fc->root);
1161 0 : fc->root = NULL;
1162 0 : goto error;
1163 : }
1164 : }
1165 : }
1166 :
1167 : return 0;
1168 :
1169 : error:
1170 0 : deactivate_locked_super(sb);
1171 0 : return err;
1172 : }
1173 :
1174 32 : int get_tree_nodev(struct fs_context *fc,
1175 : int (*fill_super)(struct super_block *sb,
1176 : struct fs_context *fc))
1177 : {
1178 32 : return vfs_get_super(fc, false, NULL, fill_super);
1179 : }
1180 : EXPORT_SYMBOL(get_tree_nodev);
1181 :
1182 0 : int get_tree_single(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, false, test_single_super, fill_super);
1187 : }
1188 : EXPORT_SYMBOL(get_tree_single);
1189 :
1190 0 : int get_tree_single_reconf(struct fs_context *fc,
1191 : int (*fill_super)(struct super_block *sb,
1192 : struct fs_context *fc))
1193 : {
1194 0 : return vfs_get_super(fc, true, test_single_super, fill_super);
1195 : }
1196 : EXPORT_SYMBOL(get_tree_single_reconf);
1197 :
1198 0 : int get_tree_keyed(struct fs_context *fc,
1199 : int (*fill_super)(struct super_block *sb,
1200 : struct fs_context *fc),
1201 : void *key)
1202 : {
1203 0 : fc->s_fs_info = key;
1204 0 : return vfs_get_super(fc, false, test_keyed_super, fill_super);
1205 : }
1206 : EXPORT_SYMBOL(get_tree_keyed);
1207 :
1208 : #ifdef CONFIG_BLOCK
1209 :
1210 0 : static int set_bdev_super(struct super_block *s, void *data)
1211 : {
1212 0 : s->s_bdev = data;
1213 0 : s->s_dev = s->s_bdev->bd_dev;
1214 0 : s->s_bdi = bdi_get(s->s_bdev->bd_disk->bdi);
1215 :
1216 0 : if (bdev_stable_writes(s->s_bdev))
1217 0 : s->s_iflags |= SB_I_STABLE_WRITES;
1218 0 : return 0;
1219 : }
1220 :
1221 0 : static int set_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1222 : {
1223 0 : return set_bdev_super(s, fc->sget_key);
1224 : }
1225 :
1226 0 : static int test_bdev_super_fc(struct super_block *s, struct fs_context *fc)
1227 : {
1228 0 : return !(s->s_iflags & SB_I_RETIRED) && s->s_bdev == fc->sget_key;
1229 : }
1230 :
1231 : /**
1232 : * get_tree_bdev - Get a superblock based on a single block device
1233 : * @fc: The filesystem context holding the parameters
1234 : * @fill_super: Helper to initialise a new superblock
1235 : */
1236 0 : int get_tree_bdev(struct fs_context *fc,
1237 : int (*fill_super)(struct super_block *,
1238 : struct fs_context *))
1239 : {
1240 : struct block_device *bdev;
1241 : struct super_block *s;
1242 0 : fmode_t mode = FMODE_READ | FMODE_EXCL;
1243 0 : int error = 0;
1244 :
1245 0 : if (!(fc->sb_flags & SB_RDONLY))
1246 0 : mode |= FMODE_WRITE;
1247 :
1248 0 : if (!fc->source)
1249 0 : return invalf(fc, "No source specified");
1250 :
1251 0 : bdev = blkdev_get_by_path(fc->source, mode, fc->fs_type);
1252 0 : if (IS_ERR(bdev)) {
1253 0 : errorf(fc, "%s: Can't open blockdev", fc->source);
1254 0 : return PTR_ERR(bdev);
1255 : }
1256 :
1257 : /* Once the superblock is inserted into the list by sget_fc(), s_umount
1258 : * will protect the lockfs code from trying to start a snapshot while
1259 : * we are mounting
1260 : */
1261 0 : mutex_lock(&bdev->bd_fsfreeze_mutex);
1262 0 : if (bdev->bd_fsfreeze_count > 0) {
1263 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1264 0 : warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
1265 0 : blkdev_put(bdev, mode);
1266 0 : return -EBUSY;
1267 : }
1268 :
1269 0 : fc->sb_flags |= SB_NOSEC;
1270 0 : fc->sget_key = bdev;
1271 0 : s = sget_fc(fc, test_bdev_super_fc, set_bdev_super_fc);
1272 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1273 0 : if (IS_ERR(s)) {
1274 0 : blkdev_put(bdev, mode);
1275 0 : return PTR_ERR(s);
1276 : }
1277 :
1278 0 : if (s->s_root) {
1279 : /* Don't summarily change the RO/RW state. */
1280 0 : if ((fc->sb_flags ^ s->s_flags) & SB_RDONLY) {
1281 0 : warnf(fc, "%pg: Can't mount, would change RO state", bdev);
1282 0 : deactivate_locked_super(s);
1283 0 : blkdev_put(bdev, mode);
1284 0 : return -EBUSY;
1285 : }
1286 :
1287 : /*
1288 : * s_umount nests inside open_mutex during
1289 : * __invalidate_device(). blkdev_put() acquires
1290 : * open_mutex and can't be called under s_umount. Drop
1291 : * s_umount temporarily. This is safe as we're
1292 : * holding an active reference.
1293 : */
1294 0 : up_write(&s->s_umount);
1295 0 : blkdev_put(bdev, mode);
1296 0 : down_write(&s->s_umount);
1297 : } else {
1298 0 : s->s_mode = mode;
1299 0 : snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1300 0 : shrinker_debugfs_rename(&s->s_shrink, "sb-%s:%s",
1301 : fc->fs_type->name, s->s_id);
1302 0 : sb_set_blocksize(s, block_size(bdev));
1303 0 : error = fill_super(s, fc);
1304 0 : if (error) {
1305 0 : deactivate_locked_super(s);
1306 0 : return error;
1307 : }
1308 :
1309 0 : s->s_flags |= SB_ACTIVE;
1310 0 : bdev->bd_super = s;
1311 : }
1312 :
1313 0 : BUG_ON(fc->root);
1314 0 : fc->root = dget(s->s_root);
1315 0 : return 0;
1316 : }
1317 : EXPORT_SYMBOL(get_tree_bdev);
1318 :
1319 0 : static int test_bdev_super(struct super_block *s, void *data)
1320 : {
1321 0 : return !(s->s_iflags & SB_I_RETIRED) && (void *)s->s_bdev == data;
1322 : }
1323 :
1324 0 : struct dentry *mount_bdev(struct file_system_type *fs_type,
1325 : int flags, const char *dev_name, void *data,
1326 : int (*fill_super)(struct super_block *, void *, int))
1327 : {
1328 : struct block_device *bdev;
1329 : struct super_block *s;
1330 0 : fmode_t mode = FMODE_READ | FMODE_EXCL;
1331 0 : int error = 0;
1332 :
1333 0 : if (!(flags & SB_RDONLY))
1334 0 : mode |= FMODE_WRITE;
1335 :
1336 0 : bdev = blkdev_get_by_path(dev_name, mode, fs_type);
1337 0 : if (IS_ERR(bdev))
1338 : return ERR_CAST(bdev);
1339 :
1340 : /*
1341 : * once the super is inserted into the list by sget, s_umount
1342 : * will protect the lockfs code from trying to start a snapshot
1343 : * while we are mounting
1344 : */
1345 0 : mutex_lock(&bdev->bd_fsfreeze_mutex);
1346 0 : if (bdev->bd_fsfreeze_count > 0) {
1347 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1348 0 : error = -EBUSY;
1349 0 : goto error_bdev;
1350 : }
1351 0 : s = sget(fs_type, test_bdev_super, set_bdev_super, flags | SB_NOSEC,
1352 : bdev);
1353 0 : mutex_unlock(&bdev->bd_fsfreeze_mutex);
1354 0 : if (IS_ERR(s))
1355 : goto error_s;
1356 :
1357 0 : if (s->s_root) {
1358 0 : if ((flags ^ s->s_flags) & SB_RDONLY) {
1359 0 : deactivate_locked_super(s);
1360 0 : error = -EBUSY;
1361 0 : goto error_bdev;
1362 : }
1363 :
1364 : /*
1365 : * s_umount nests inside open_mutex during
1366 : * __invalidate_device(). blkdev_put() acquires
1367 : * open_mutex and can't be called under s_umount. Drop
1368 : * s_umount temporarily. This is safe as we're
1369 : * holding an active reference.
1370 : */
1371 0 : up_write(&s->s_umount);
1372 0 : blkdev_put(bdev, mode);
1373 0 : down_write(&s->s_umount);
1374 : } else {
1375 0 : s->s_mode = mode;
1376 0 : snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
1377 0 : shrinker_debugfs_rename(&s->s_shrink, "sb-%s:%s",
1378 : fs_type->name, s->s_id);
1379 0 : sb_set_blocksize(s, block_size(bdev));
1380 0 : error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1381 0 : if (error) {
1382 0 : deactivate_locked_super(s);
1383 0 : goto error;
1384 : }
1385 :
1386 0 : s->s_flags |= SB_ACTIVE;
1387 0 : bdev->bd_super = s;
1388 : }
1389 :
1390 0 : return dget(s->s_root);
1391 :
1392 : error_s:
1393 0 : error = PTR_ERR(s);
1394 : error_bdev:
1395 0 : blkdev_put(bdev, mode);
1396 : error:
1397 0 : return ERR_PTR(error);
1398 : }
1399 : EXPORT_SYMBOL(mount_bdev);
1400 :
1401 0 : void kill_block_super(struct super_block *sb)
1402 : {
1403 0 : struct block_device *bdev = sb->s_bdev;
1404 0 : fmode_t mode = sb->s_mode;
1405 :
1406 0 : bdev->bd_super = NULL;
1407 0 : generic_shutdown_super(sb);
1408 0 : sync_blockdev(bdev);
1409 0 : WARN_ON_ONCE(!(mode & FMODE_EXCL));
1410 0 : blkdev_put(bdev, mode | FMODE_EXCL);
1411 0 : }
1412 :
1413 : EXPORT_SYMBOL(kill_block_super);
1414 : #endif
1415 :
1416 0 : struct dentry *mount_nodev(struct file_system_type *fs_type,
1417 : int flags, void *data,
1418 : int (*fill_super)(struct super_block *, void *, int))
1419 : {
1420 : int error;
1421 0 : struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
1422 :
1423 0 : if (IS_ERR(s))
1424 : return ERR_CAST(s);
1425 :
1426 0 : error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1427 0 : if (error) {
1428 0 : deactivate_locked_super(s);
1429 0 : return ERR_PTR(error);
1430 : }
1431 0 : s->s_flags |= SB_ACTIVE;
1432 0 : return dget(s->s_root);
1433 : }
1434 : EXPORT_SYMBOL(mount_nodev);
1435 :
1436 0 : int reconfigure_single(struct super_block *s,
1437 : int flags, void *data)
1438 : {
1439 : struct fs_context *fc;
1440 : int ret;
1441 :
1442 : /* The caller really need to be passing fc down into mount_single(),
1443 : * then a chunk of this can be removed. [Bollocks -- AV]
1444 : * Better yet, reconfiguration shouldn't happen, but rather the second
1445 : * mount should be rejected if the parameters are not compatible.
1446 : */
1447 0 : fc = fs_context_for_reconfigure(s->s_root, flags, MS_RMT_MASK);
1448 0 : if (IS_ERR(fc))
1449 0 : return PTR_ERR(fc);
1450 :
1451 0 : ret = parse_monolithic_mount_data(fc, data);
1452 0 : if (ret < 0)
1453 : goto out;
1454 :
1455 0 : ret = reconfigure_super(fc);
1456 : out:
1457 0 : put_fs_context(fc);
1458 0 : return ret;
1459 : }
1460 :
1461 0 : static int compare_single(struct super_block *s, void *p)
1462 : {
1463 0 : return 1;
1464 : }
1465 :
1466 0 : struct dentry *mount_single(struct file_system_type *fs_type,
1467 : int flags, void *data,
1468 : int (*fill_super)(struct super_block *, void *, int))
1469 : {
1470 : struct super_block *s;
1471 : int error;
1472 :
1473 0 : s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
1474 0 : if (IS_ERR(s))
1475 : return ERR_CAST(s);
1476 0 : if (!s->s_root) {
1477 0 : error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
1478 0 : if (!error)
1479 0 : s->s_flags |= SB_ACTIVE;
1480 : } else {
1481 0 : error = reconfigure_single(s, flags, data);
1482 : }
1483 0 : if (unlikely(error)) {
1484 0 : deactivate_locked_super(s);
1485 0 : return ERR_PTR(error);
1486 : }
1487 0 : return dget(s->s_root);
1488 : }
1489 : EXPORT_SYMBOL(mount_single);
1490 :
1491 : /**
1492 : * vfs_get_tree - Get the mountable root
1493 : * @fc: The superblock configuration context.
1494 : *
1495 : * The filesystem is invoked to get or create a superblock which can then later
1496 : * be used for mounting. The filesystem places a pointer to the root to be
1497 : * used for mounting in @fc->root.
1498 : */
1499 32 : int vfs_get_tree(struct fs_context *fc)
1500 : {
1501 : struct super_block *sb;
1502 : int error;
1503 :
1504 32 : if (fc->root)
1505 : return -EBUSY;
1506 :
1507 : /* Get the mountable root in fc->root, with a ref on the root and a ref
1508 : * on the superblock.
1509 : */
1510 32 : error = fc->ops->get_tree(fc);
1511 32 : if (error < 0)
1512 : return error;
1513 :
1514 32 : if (!fc->root) {
1515 0 : pr_err("Filesystem %s get_tree() didn't set fc->root\n",
1516 : fc->fs_type->name);
1517 : /* We don't know what the locking state of the superblock is -
1518 : * if there is a superblock.
1519 : */
1520 0 : BUG();
1521 : }
1522 :
1523 32 : sb = fc->root->d_sb;
1524 32 : WARN_ON(!sb->s_bdi);
1525 :
1526 : /*
1527 : * Write barrier is for super_cache_count(). We place it before setting
1528 : * SB_BORN as the data dependency between the two functions is the
1529 : * superblock structure contents that we just set up, not the SB_BORN
1530 : * flag.
1531 : */
1532 32 : smp_wmb();
1533 32 : sb->s_flags |= SB_BORN;
1534 :
1535 32 : error = security_sb_set_mnt_opts(sb, fc->security, 0, NULL);
1536 : if (unlikely(error)) {
1537 : fc_drop_locked(fc);
1538 : return error;
1539 : }
1540 :
1541 : /*
1542 : * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1543 : * but s_maxbytes was an unsigned long long for many releases. Throw
1544 : * this warning for a little while to try and catch filesystems that
1545 : * violate this rule.
1546 : */
1547 32 : WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1548 : "negative value (%lld)\n", fc->fs_type->name, sb->s_maxbytes);
1549 :
1550 : return 0;
1551 : }
1552 : EXPORT_SYMBOL(vfs_get_tree);
1553 :
1554 : /*
1555 : * Setup private BDI for given superblock. It gets automatically cleaned up
1556 : * in generic_shutdown_super().
1557 : */
1558 0 : int super_setup_bdi_name(struct super_block *sb, char *fmt, ...)
1559 : {
1560 : struct backing_dev_info *bdi;
1561 : int err;
1562 : va_list args;
1563 :
1564 0 : bdi = bdi_alloc(NUMA_NO_NODE);
1565 0 : if (!bdi)
1566 : return -ENOMEM;
1567 :
1568 0 : va_start(args, fmt);
1569 0 : err = bdi_register_va(bdi, fmt, args);
1570 0 : va_end(args);
1571 0 : if (err) {
1572 0 : bdi_put(bdi);
1573 0 : return err;
1574 : }
1575 0 : WARN_ON(sb->s_bdi != &noop_backing_dev_info);
1576 0 : sb->s_bdi = bdi;
1577 0 : sb->s_iflags |= SB_I_PERSB_BDI;
1578 :
1579 0 : return 0;
1580 : }
1581 : EXPORT_SYMBOL(super_setup_bdi_name);
1582 :
1583 : /*
1584 : * Setup private BDI for given superblock. I gets automatically cleaned up
1585 : * in generic_shutdown_super().
1586 : */
1587 0 : int super_setup_bdi(struct super_block *sb)
1588 : {
1589 : static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
1590 :
1591 0 : return super_setup_bdi_name(sb, "%.28s-%ld", sb->s_type->name,
1592 : atomic_long_inc_return(&bdi_seq));
1593 : }
1594 : EXPORT_SYMBOL(super_setup_bdi);
1595 :
1596 : /**
1597 : * sb_wait_write - wait until all writers to given file system finish
1598 : * @sb: the super for which we wait
1599 : * @level: type of writers we wait for (normal vs page fault)
1600 : *
1601 : * This function waits until there are no writers of given type to given file
1602 : * system.
1603 : */
1604 : static void sb_wait_write(struct super_block *sb, int level)
1605 : {
1606 0 : percpu_down_write(sb->s_writers.rw_sem + level-1);
1607 : }
1608 :
1609 : /*
1610 : * We are going to return to userspace and forget about these locks, the
1611 : * ownership goes to the caller of thaw_super() which does unlock().
1612 : */
1613 : static void lockdep_sb_freeze_release(struct super_block *sb)
1614 : {
1615 : int level;
1616 :
1617 0 : for (level = SB_FREEZE_LEVELS - 1; level >= 0; level--)
1618 : percpu_rwsem_release(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1619 : }
1620 :
1621 : /*
1622 : * Tell lockdep we are holding these locks before we call ->unfreeze_fs(sb).
1623 : */
1624 : static void lockdep_sb_freeze_acquire(struct super_block *sb)
1625 : {
1626 : int level;
1627 :
1628 0 : for (level = 0; level < SB_FREEZE_LEVELS; ++level)
1629 : percpu_rwsem_acquire(sb->s_writers.rw_sem + level, 0, _THIS_IP_);
1630 : }
1631 :
1632 : static void sb_freeze_unlock(struct super_block *sb, int level)
1633 : {
1634 0 : for (level--; level >= 0; level--)
1635 0 : percpu_up_write(sb->s_writers.rw_sem + level);
1636 : }
1637 :
1638 : /**
1639 : * freeze_super - lock the filesystem and force it into a consistent state
1640 : * @sb: the super to lock
1641 : *
1642 : * Syncs the super to make sure the filesystem is consistent and calls the fs's
1643 : * freeze_fs. Subsequent calls to this without first thawing the fs will return
1644 : * -EBUSY.
1645 : *
1646 : * During this function, sb->s_writers.frozen goes through these values:
1647 : *
1648 : * SB_UNFROZEN: File system is normal, all writes progress as usual.
1649 : *
1650 : * SB_FREEZE_WRITE: The file system is in the process of being frozen. New
1651 : * writes should be blocked, though page faults are still allowed. We wait for
1652 : * all writes to complete and then proceed to the next stage.
1653 : *
1654 : * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
1655 : * but internal fs threads can still modify the filesystem (although they
1656 : * should not dirty new pages or inodes), writeback can run etc. After waiting
1657 : * for all running page faults we sync the filesystem which will clean all
1658 : * dirty pages and inodes (no new dirty pages or inodes can be created when
1659 : * sync is running).
1660 : *
1661 : * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
1662 : * modification are blocked (e.g. XFS preallocation truncation on inode
1663 : * reclaim). This is usually implemented by blocking new transactions for
1664 : * filesystems that have them and need this additional guard. After all
1665 : * internal writers are finished we call ->freeze_fs() to finish filesystem
1666 : * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
1667 : * mostly auxiliary for filesystems to verify they do not modify frozen fs.
1668 : *
1669 : * sb->s_writers.frozen is protected by sb->s_umount.
1670 : */
1671 0 : int freeze_super(struct super_block *sb)
1672 : {
1673 : int ret;
1674 :
1675 0 : atomic_inc(&sb->s_active);
1676 0 : down_write(&sb->s_umount);
1677 0 : if (sb->s_writers.frozen != SB_UNFROZEN) {
1678 0 : deactivate_locked_super(sb);
1679 0 : return -EBUSY;
1680 : }
1681 :
1682 0 : if (!(sb->s_flags & SB_BORN)) {
1683 0 : up_write(&sb->s_umount);
1684 0 : return 0; /* sic - it's "nothing to do" */
1685 : }
1686 :
1687 0 : if (sb_rdonly(sb)) {
1688 : /* Nothing to do really... */
1689 0 : sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1690 0 : up_write(&sb->s_umount);
1691 0 : return 0;
1692 : }
1693 :
1694 0 : sb->s_writers.frozen = SB_FREEZE_WRITE;
1695 : /* Release s_umount to preserve sb_start_write -> s_umount ordering */
1696 0 : up_write(&sb->s_umount);
1697 0 : sb_wait_write(sb, SB_FREEZE_WRITE);
1698 0 : down_write(&sb->s_umount);
1699 :
1700 : /* Now we go and block page faults... */
1701 0 : sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
1702 0 : sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
1703 :
1704 : /* All writers are done so after syncing there won't be dirty data */
1705 0 : ret = sync_filesystem(sb);
1706 0 : if (ret) {
1707 0 : sb->s_writers.frozen = SB_UNFROZEN;
1708 0 : sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT);
1709 0 : wake_up(&sb->s_writers.wait_unfrozen);
1710 0 : deactivate_locked_super(sb);
1711 0 : return ret;
1712 : }
1713 :
1714 : /* Now wait for internal filesystem counter */
1715 0 : sb->s_writers.frozen = SB_FREEZE_FS;
1716 0 : sb_wait_write(sb, SB_FREEZE_FS);
1717 :
1718 0 : if (sb->s_op->freeze_fs) {
1719 0 : ret = sb->s_op->freeze_fs(sb);
1720 0 : if (ret) {
1721 0 : printk(KERN_ERR
1722 : "VFS:Filesystem freeze failed\n");
1723 0 : sb->s_writers.frozen = SB_UNFROZEN;
1724 0 : sb_freeze_unlock(sb, SB_FREEZE_FS);
1725 0 : wake_up(&sb->s_writers.wait_unfrozen);
1726 0 : deactivate_locked_super(sb);
1727 0 : return ret;
1728 : }
1729 : }
1730 : /*
1731 : * For debugging purposes so that fs can warn if it sees write activity
1732 : * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super().
1733 : */
1734 0 : sb->s_writers.frozen = SB_FREEZE_COMPLETE;
1735 0 : lockdep_sb_freeze_release(sb);
1736 0 : up_write(&sb->s_umount);
1737 0 : return 0;
1738 : }
1739 : EXPORT_SYMBOL(freeze_super);
1740 :
1741 0 : static int thaw_super_locked(struct super_block *sb)
1742 : {
1743 : int error;
1744 :
1745 0 : if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) {
1746 0 : up_write(&sb->s_umount);
1747 0 : return -EINVAL;
1748 : }
1749 :
1750 0 : if (sb_rdonly(sb)) {
1751 0 : sb->s_writers.frozen = SB_UNFROZEN;
1752 0 : goto out;
1753 : }
1754 :
1755 0 : lockdep_sb_freeze_acquire(sb);
1756 :
1757 0 : if (sb->s_op->unfreeze_fs) {
1758 0 : error = sb->s_op->unfreeze_fs(sb);
1759 0 : if (error) {
1760 0 : printk(KERN_ERR
1761 : "VFS:Filesystem thaw failed\n");
1762 0 : lockdep_sb_freeze_release(sb);
1763 0 : up_write(&sb->s_umount);
1764 0 : return error;
1765 : }
1766 : }
1767 :
1768 0 : sb->s_writers.frozen = SB_UNFROZEN;
1769 : sb_freeze_unlock(sb, SB_FREEZE_FS);
1770 : out:
1771 0 : wake_up(&sb->s_writers.wait_unfrozen);
1772 0 : deactivate_locked_super(sb);
1773 0 : return 0;
1774 : }
1775 :
1776 : /**
1777 : * thaw_super -- unlock filesystem
1778 : * @sb: the super to thaw
1779 : *
1780 : * Unlocks the filesystem and marks it writeable again after freeze_super().
1781 : */
1782 0 : int thaw_super(struct super_block *sb)
1783 : {
1784 0 : down_write(&sb->s_umount);
1785 0 : return thaw_super_locked(sb);
1786 : }
1787 : EXPORT_SYMBOL(thaw_super);
1788 :
1789 : /*
1790 : * Create workqueue for deferred direct IO completions. We allocate the
1791 : * workqueue when it's first needed. This avoids creating workqueue for
1792 : * filesystems that don't need it and also allows us to create the workqueue
1793 : * late enough so the we can include s_id in the name of the workqueue.
1794 : */
1795 0 : int sb_init_dio_done_wq(struct super_block *sb)
1796 : {
1797 : struct workqueue_struct *old;
1798 0 : struct workqueue_struct *wq = alloc_workqueue("dio/%s",
1799 : WQ_MEM_RECLAIM, 0,
1800 0 : sb->s_id);
1801 0 : if (!wq)
1802 : return -ENOMEM;
1803 : /*
1804 : * This has to be atomic as more DIOs can race to create the workqueue
1805 : */
1806 0 : old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
1807 : /* Someone created workqueue before us? Free ours... */
1808 0 : if (old)
1809 0 : destroy_workqueue(wq);
1810 : return 0;
1811 : }
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