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1 | /* | |
2 | * linux/fs/super.c | |
3 | * | |
4 | * Copyright (C) 1991, 1992 Linus Torvalds | |
5 | * | |
6 | * super.c contains code to handle: - mount structures | |
7 | * - super-block tables | |
8 | * - filesystem drivers list | |
9 | * - mount system call | |
10 | * - umount system call | |
11 | * - ustat system call | |
12 | * | |
13 | * GK 2/5/95 - Changed to support mounting the root fs via NFS | |
14 | * | |
15 | * Added kerneld support: Jacques Gelinas and Bjorn Ekwall | |
16 | * Added change_root: Werner Almesberger & Hans Lermen, Feb '96 | |
17 | * Added options to /proc/mounts: | |
18 | * Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996. | |
19 | * Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998 | |
20 | * Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000 | |
21 | */ | |
22 | ||
23 | #include <linux/export.h> | |
24 | #include <linux/slab.h> | |
25 | #include <linux/acct.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/fsnotify.h> | |
36 | #include <linux/lockdep.h> | |
37 | #include "internal.h" | |
38 | ||
39 | ||
40 | LIST_HEAD(super_blocks); | |
41 | DEFINE_SPINLOCK(sb_lock); | |
42 | ||
43 | static char *sb_writers_name[SB_FREEZE_LEVELS] = { | |
44 | "sb_writers", | |
45 | "sb_pagefaults", | |
46 | "sb_internal", | |
47 | }; | |
48 | ||
49 | /* | |
50 | * One thing we have to be careful of with a per-sb shrinker is that we don't | |
51 | * drop the last active reference to the superblock from within the shrinker. | |
52 | * If that happens we could trigger unregistering the shrinker from within the | |
53 | * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we | |
54 | * take a passive reference to the superblock to avoid this from occurring. | |
55 | */ | |
56 | static int prune_super(struct shrinker *shrink, struct shrink_control *sc) | |
57 | { | |
58 | struct super_block *sb; | |
59 | int fs_objects = 0; | |
60 | int total_objects; | |
61 | ||
62 | sb = container_of(shrink, struct super_block, s_shrink); | |
63 | ||
64 | /* | |
65 | * Deadlock avoidance. We may hold various FS locks, and we don't want | |
66 | * to recurse into the FS that called us in clear_inode() and friends.. | |
67 | */ | |
68 | if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS)) | |
69 | return -1; | |
70 | ||
71 | if (!grab_super_passive(sb)) | |
72 | return -1; | |
73 | ||
74 | if (sb->s_op && sb->s_op->nr_cached_objects) | |
75 | fs_objects = sb->s_op->nr_cached_objects(sb); | |
76 | ||
77 | total_objects = sb->s_nr_dentry_unused + | |
78 | sb->s_nr_inodes_unused + fs_objects + 1; | |
79 | ||
80 | if (sc->nr_to_scan) { | |
81 | int dentries; | |
82 | int inodes; | |
83 | ||
84 | /* proportion the scan between the caches */ | |
85 | dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) / | |
86 | total_objects; | |
87 | inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) / | |
88 | total_objects; | |
89 | if (fs_objects) | |
90 | fs_objects = (sc->nr_to_scan * fs_objects) / | |
91 | total_objects; | |
92 | /* | |
93 | * prune the dcache first as the icache is pinned by it, then | |
94 | * prune the icache, followed by the filesystem specific caches | |
95 | */ | |
96 | prune_dcache_sb(sb, dentries); | |
97 | prune_icache_sb(sb, inodes); | |
98 | ||
99 | if (fs_objects && sb->s_op->free_cached_objects) { | |
100 | sb->s_op->free_cached_objects(sb, fs_objects); | |
101 | fs_objects = sb->s_op->nr_cached_objects(sb); | |
102 | } | |
103 | total_objects = sb->s_nr_dentry_unused + | |
104 | sb->s_nr_inodes_unused + fs_objects; | |
105 | } | |
106 | ||
107 | total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure; | |
108 | drop_super(sb); | |
109 | return total_objects; | |
110 | } | |
111 | ||
112 | static int init_sb_writers(struct super_block *s, struct file_system_type *type) | |
113 | { | |
114 | int err; | |
115 | int i; | |
116 | ||
117 | for (i = 0; i < SB_FREEZE_LEVELS; i++) { | |
118 | err = percpu_counter_init(&s->s_writers.counter[i], 0); | |
119 | if (err < 0) | |
120 | goto err_out; | |
121 | lockdep_init_map(&s->s_writers.lock_map[i], sb_writers_name[i], | |
122 | &type->s_writers_key[i], 0); | |
123 | } | |
124 | init_waitqueue_head(&s->s_writers.wait); | |
125 | init_waitqueue_head(&s->s_writers.wait_unfrozen); | |
126 | return 0; | |
127 | err_out: | |
128 | while (--i >= 0) | |
129 | percpu_counter_destroy(&s->s_writers.counter[i]); | |
130 | return err; | |
131 | } | |
132 | ||
133 | static void destroy_sb_writers(struct super_block *s) | |
134 | { | |
135 | int i; | |
136 | ||
137 | for (i = 0; i < SB_FREEZE_LEVELS; i++) | |
138 | percpu_counter_destroy(&s->s_writers.counter[i]); | |
139 | } | |
140 | ||
141 | /** | |
142 | * alloc_super - create new superblock | |
143 | * @type: filesystem type superblock should belong to | |
144 | * @flags: the mount flags | |
145 | * | |
146 | * Allocates and initializes a new &struct super_block. alloc_super() | |
147 | * returns a pointer new superblock or %NULL if allocation had failed. | |
148 | */ | |
149 | static struct super_block *alloc_super(struct file_system_type *type, int flags) | |
150 | { | |
151 | struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER); | |
152 | static const struct super_operations default_op; | |
153 | ||
154 | if (s) { | |
155 | if (security_sb_alloc(s)) { | |
156 | /* | |
157 | * We cannot call security_sb_free() without | |
158 | * security_sb_alloc() succeeding. So bail out manually | |
159 | */ | |
160 | kfree(s); | |
161 | s = NULL; | |
162 | goto out; | |
163 | } | |
164 | #ifdef CONFIG_SMP | |
165 | s->s_files = alloc_percpu(struct list_head); | |
166 | if (!s->s_files) | |
167 | goto err_out; | |
168 | else { | |
169 | int i; | |
170 | ||
171 | for_each_possible_cpu(i) | |
172 | INIT_LIST_HEAD(per_cpu_ptr(s->s_files, i)); | |
173 | } | |
174 | #else | |
175 | INIT_LIST_HEAD(&s->s_files); | |
176 | #endif | |
177 | if (init_sb_writers(s, type)) | |
178 | goto err_out; | |
179 | s->s_flags = flags; | |
180 | s->s_bdi = &default_backing_dev_info; | |
181 | INIT_HLIST_NODE(&s->s_instances); | |
182 | INIT_HLIST_BL_HEAD(&s->s_anon); | |
183 | INIT_LIST_HEAD(&s->s_inodes); | |
184 | INIT_LIST_HEAD(&s->s_dentry_lru); | |
185 | INIT_LIST_HEAD(&s->s_inode_lru); | |
186 | spin_lock_init(&s->s_inode_lru_lock); | |
187 | INIT_LIST_HEAD(&s->s_mounts); | |
188 | init_rwsem(&s->s_umount); | |
189 | mutex_init(&s->s_lock); | |
190 | lockdep_set_class(&s->s_umount, &type->s_umount_key); | |
191 | /* | |
192 | * The locking rules for s_lock are up to the | |
193 | * filesystem. For example ext3fs has different | |
194 | * lock ordering than usbfs: | |
195 | */ | |
196 | lockdep_set_class(&s->s_lock, &type->s_lock_key); | |
197 | /* | |
198 | * sget() can have s_umount recursion. | |
199 | * | |
200 | * When it cannot find a suitable sb, it allocates a new | |
201 | * one (this one), and tries again to find a suitable old | |
202 | * one. | |
203 | * | |
204 | * In case that succeeds, it will acquire the s_umount | |
205 | * lock of the old one. Since these are clearly distrinct | |
206 | * locks, and this object isn't exposed yet, there's no | |
207 | * risk of deadlocks. | |
208 | * | |
209 | * Annotate this by putting this lock in a different | |
210 | * subclass. | |
211 | */ | |
212 | down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); | |
213 | s->s_count = 1; | |
214 | atomic_set(&s->s_active, 1); | |
215 | mutex_init(&s->s_vfs_rename_mutex); | |
216 | lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key); | |
217 | mutex_init(&s->s_dquot.dqio_mutex); | |
218 | mutex_init(&s->s_dquot.dqonoff_mutex); | |
219 | init_rwsem(&s->s_dquot.dqptr_sem); | |
220 | s->s_maxbytes = MAX_NON_LFS; | |
221 | s->s_op = &default_op; | |
222 | s->s_time_gran = 1000000000; | |
223 | s->cleancache_poolid = -1; | |
224 | ||
225 | s->s_shrink.seeks = DEFAULT_SEEKS; | |
226 | s->s_shrink.shrink = prune_super; | |
227 | s->s_shrink.batch = 1024; | |
228 | } | |
229 | out: | |
230 | return s; | |
231 | err_out: | |
232 | security_sb_free(s); | |
233 | #ifdef CONFIG_SMP | |
234 | if (s->s_files) | |
235 | free_percpu(s->s_files); | |
236 | #endif | |
237 | destroy_sb_writers(s); | |
238 | kfree(s); | |
239 | s = NULL; | |
240 | goto out; | |
241 | } | |
242 | ||
243 | /** | |
244 | * destroy_super - frees a superblock | |
245 | * @s: superblock to free | |
246 | * | |
247 | * Frees a superblock. | |
248 | */ | |
249 | static inline void destroy_super(struct super_block *s) | |
250 | { | |
251 | #ifdef CONFIG_SMP | |
252 | free_percpu(s->s_files); | |
253 | #endif | |
254 | destroy_sb_writers(s); | |
255 | security_sb_free(s); | |
256 | WARN_ON(!list_empty(&s->s_mounts)); | |
257 | kfree(s->s_subtype); | |
258 | kfree(s->s_options); | |
259 | kfree(s); | |
260 | } | |
261 | ||
262 | /* Superblock refcounting */ | |
263 | ||
264 | /* | |
265 | * Drop a superblock's refcount. The caller must hold sb_lock. | |
266 | */ | |
267 | static void __put_super(struct super_block *sb) | |
268 | { | |
269 | if (!--sb->s_count) { | |
270 | list_del_init(&sb->s_list); | |
271 | destroy_super(sb); | |
272 | } | |
273 | } | |
274 | ||
275 | /** | |
276 | * put_super - drop a temporary reference to superblock | |
277 | * @sb: superblock in question | |
278 | * | |
279 | * Drops a temporary reference, frees superblock if there's no | |
280 | * references left. | |
281 | */ | |
282 | static void put_super(struct super_block *sb) | |
283 | { | |
284 | spin_lock(&sb_lock); | |
285 | __put_super(sb); | |
286 | spin_unlock(&sb_lock); | |
287 | } | |
288 | ||
289 | ||
290 | /** | |
291 | * deactivate_locked_super - drop an active reference to superblock | |
292 | * @s: superblock to deactivate | |
293 | * | |
294 | * Drops an active reference to superblock, converting it into a temprory | |
295 | * one if there is no other active references left. In that case we | |
296 | * tell fs driver to shut it down and drop the temporary reference we | |
297 | * had just acquired. | |
298 | * | |
299 | * Caller holds exclusive lock on superblock; that lock is released. | |
300 | */ | |
301 | void deactivate_locked_super(struct super_block *s) | |
302 | { | |
303 | struct file_system_type *fs = s->s_type; | |
304 | if (atomic_dec_and_test(&s->s_active)) { | |
305 | cleancache_invalidate_fs(s); | |
306 | fs->kill_sb(s); | |
307 | ||
308 | /* caches are now gone, we can safely kill the shrinker now */ | |
309 | unregister_shrinker(&s->s_shrink); | |
310 | ||
311 | /* | |
312 | * We need to call rcu_barrier so all the delayed rcu free | |
313 | * inodes are flushed before we release the fs module. | |
314 | */ | |
315 | rcu_barrier(); | |
316 | put_filesystem(fs); | |
317 | put_super(s); | |
318 | } else { | |
319 | up_write(&s->s_umount); | |
320 | } | |
321 | } | |
322 | ||
323 | EXPORT_SYMBOL(deactivate_locked_super); | |
324 | ||
325 | /** | |
326 | * deactivate_super - drop an active reference to superblock | |
327 | * @s: superblock to deactivate | |
328 | * | |
329 | * Variant of deactivate_locked_super(), except that superblock is *not* | |
330 | * locked by caller. If we are going to drop the final active reference, | |
331 | * lock will be acquired prior to that. | |
332 | */ | |
333 | void deactivate_super(struct super_block *s) | |
334 | { | |
335 | if (!atomic_add_unless(&s->s_active, -1, 1)) { | |
336 | down_write(&s->s_umount); | |
337 | deactivate_locked_super(s); | |
338 | } | |
339 | } | |
340 | ||
341 | EXPORT_SYMBOL(deactivate_super); | |
342 | ||
343 | /** | |
344 | * grab_super - acquire an active reference | |
345 | * @s: reference we are trying to make active | |
346 | * | |
347 | * Tries to acquire an active reference. grab_super() is used when we | |
348 | * had just found a superblock in super_blocks or fs_type->fs_supers | |
349 | * and want to turn it into a full-blown active reference. grab_super() | |
350 | * is called with sb_lock held and drops it. Returns 1 in case of | |
351 | * success, 0 if we had failed (superblock contents was already dead or | |
352 | * dying when grab_super() had been called). | |
353 | */ | |
354 | static int grab_super(struct super_block *s) __releases(sb_lock) | |
355 | { | |
356 | if (atomic_inc_not_zero(&s->s_active)) { | |
357 | spin_unlock(&sb_lock); | |
358 | return 1; | |
359 | } | |
360 | /* it's going away */ | |
361 | s->s_count++; | |
362 | spin_unlock(&sb_lock); | |
363 | /* wait for it to die */ | |
364 | down_write(&s->s_umount); | |
365 | up_write(&s->s_umount); | |
366 | put_super(s); | |
367 | return 0; | |
368 | } | |
369 | ||
370 | /* | |
371 | * grab_super_passive - acquire a passive reference | |
372 | * @sb: reference we are trying to grab | |
373 | * | |
374 | * Tries to acquire a passive reference. This is used in places where we | |
375 | * cannot take an active reference but we need to ensure that the | |
376 | * superblock does not go away while we are working on it. It returns | |
377 | * false if a reference was not gained, and returns true with the s_umount | |
378 | * lock held in read mode if a reference is gained. On successful return, | |
379 | * the caller must drop the s_umount lock and the passive reference when | |
380 | * done. | |
381 | */ | |
382 | bool grab_super_passive(struct super_block *sb) | |
383 | { | |
384 | spin_lock(&sb_lock); | |
385 | if (hlist_unhashed(&sb->s_instances)) { | |
386 | spin_unlock(&sb_lock); | |
387 | return false; | |
388 | } | |
389 | ||
390 | sb->s_count++; | |
391 | spin_unlock(&sb_lock); | |
392 | ||
393 | if (down_read_trylock(&sb->s_umount)) { | |
394 | if (sb->s_root && (sb->s_flags & MS_BORN)) | |
395 | return true; | |
396 | up_read(&sb->s_umount); | |
397 | } | |
398 | ||
399 | put_super(sb); | |
400 | return false; | |
401 | } | |
402 | ||
403 | /* | |
404 | * Superblock locking. We really ought to get rid of these two. | |
405 | */ | |
406 | void lock_super(struct super_block * sb) | |
407 | { | |
408 | mutex_lock(&sb->s_lock); | |
409 | } | |
410 | ||
411 | void unlock_super(struct super_block * sb) | |
412 | { | |
413 | mutex_unlock(&sb->s_lock); | |
414 | } | |
415 | ||
416 | EXPORT_SYMBOL(lock_super); | |
417 | EXPORT_SYMBOL(unlock_super); | |
418 | ||
419 | /** | |
420 | * generic_shutdown_super - common helper for ->kill_sb() | |
421 | * @sb: superblock to kill | |
422 | * | |
423 | * generic_shutdown_super() does all fs-independent work on superblock | |
424 | * shutdown. Typical ->kill_sb() should pick all fs-specific objects | |
425 | * that need destruction out of superblock, call generic_shutdown_super() | |
426 | * and release aforementioned objects. Note: dentries and inodes _are_ | |
427 | * taken care of and do not need specific handling. | |
428 | * | |
429 | * Upon calling this function, the filesystem may no longer alter or | |
430 | * rearrange the set of dentries belonging to this super_block, nor may it | |
431 | * change the attachments of dentries to inodes. | |
432 | */ | |
433 | void generic_shutdown_super(struct super_block *sb) | |
434 | { | |
435 | const struct super_operations *sop = sb->s_op; | |
436 | ||
437 | if (sb->s_root) { | |
438 | shrink_dcache_for_umount(sb); | |
439 | sync_filesystem(sb); | |
440 | sb->s_flags &= ~MS_ACTIVE; | |
441 | ||
442 | fsnotify_unmount_inodes(&sb->s_inodes); | |
443 | ||
444 | evict_inodes(sb); | |
445 | ||
446 | if (sop->put_super) | |
447 | sop->put_super(sb); | |
448 | ||
449 | if (!list_empty(&sb->s_inodes)) { | |
450 | printk("VFS: Busy inodes after unmount of %s. " | |
451 | "Self-destruct in 5 seconds. Have a nice day...\n", | |
452 | sb->s_id); | |
453 | } | |
454 | } | |
455 | spin_lock(&sb_lock); | |
456 | /* should be initialized for __put_super_and_need_restart() */ | |
457 | hlist_del_init(&sb->s_instances); | |
458 | spin_unlock(&sb_lock); | |
459 | up_write(&sb->s_umount); | |
460 | } | |
461 | ||
462 | EXPORT_SYMBOL(generic_shutdown_super); | |
463 | ||
464 | /** | |
465 | * sget - find or create a superblock | |
466 | * @type: filesystem type superblock should belong to | |
467 | * @test: comparison callback | |
468 | * @set: setup callback | |
469 | * @flags: mount flags | |
470 | * @data: argument to each of them | |
471 | */ | |
472 | struct super_block *sget(struct file_system_type *type, | |
473 | int (*test)(struct super_block *,void *), | |
474 | int (*set)(struct super_block *,void *), | |
475 | int flags, | |
476 | void *data) | |
477 | { | |
478 | struct super_block *s = NULL; | |
479 | struct hlist_node *node; | |
480 | struct super_block *old; | |
481 | int err; | |
482 | ||
483 | retry: | |
484 | spin_lock(&sb_lock); | |
485 | if (test) { | |
486 | hlist_for_each_entry(old, node, &type->fs_supers, s_instances) { | |
487 | if (!test(old, data)) | |
488 | continue; | |
489 | if (!grab_super(old)) | |
490 | goto retry; | |
491 | if (s) { | |
492 | up_write(&s->s_umount); | |
493 | destroy_super(s); | |
494 | s = NULL; | |
495 | } | |
496 | down_write(&old->s_umount); | |
497 | if (unlikely(!(old->s_flags & MS_BORN))) { | |
498 | deactivate_locked_super(old); | |
499 | goto retry; | |
500 | } | |
501 | return old; | |
502 | } | |
503 | } | |
504 | if (!s) { | |
505 | spin_unlock(&sb_lock); | |
506 | s = alloc_super(type, flags); | |
507 | if (!s) | |
508 | return ERR_PTR(-ENOMEM); | |
509 | goto retry; | |
510 | } | |
511 | ||
512 | err = set(s, data); | |
513 | if (err) { | |
514 | spin_unlock(&sb_lock); | |
515 | up_write(&s->s_umount); | |
516 | destroy_super(s); | |
517 | return ERR_PTR(err); | |
518 | } | |
519 | s->s_type = type; | |
520 | strlcpy(s->s_id, type->name, sizeof(s->s_id)); | |
521 | list_add_tail(&s->s_list, &super_blocks); | |
522 | hlist_add_head(&s->s_instances, &type->fs_supers); | |
523 | spin_unlock(&sb_lock); | |
524 | get_filesystem(type); | |
525 | register_shrinker(&s->s_shrink); | |
526 | return s; | |
527 | } | |
528 | ||
529 | EXPORT_SYMBOL(sget); | |
530 | ||
531 | void drop_super(struct super_block *sb) | |
532 | { | |
533 | up_read(&sb->s_umount); | |
534 | put_super(sb); | |
535 | } | |
536 | ||
537 | EXPORT_SYMBOL(drop_super); | |
538 | ||
539 | /** | |
540 | * iterate_supers - call function for all active superblocks | |
541 | * @f: function to call | |
542 | * @arg: argument to pass to it | |
543 | * | |
544 | * Scans the superblock list and calls given function, passing it | |
545 | * locked superblock and given argument. | |
546 | */ | |
547 | void iterate_supers(void (*f)(struct super_block *, void *), void *arg) | |
548 | { | |
549 | struct super_block *sb, *p = NULL; | |
550 | ||
551 | spin_lock(&sb_lock); | |
552 | list_for_each_entry(sb, &super_blocks, s_list) { | |
553 | if (hlist_unhashed(&sb->s_instances)) | |
554 | continue; | |
555 | sb->s_count++; | |
556 | spin_unlock(&sb_lock); | |
557 | ||
558 | down_read(&sb->s_umount); | |
559 | if (sb->s_root && (sb->s_flags & MS_BORN)) | |
560 | f(sb, arg); | |
561 | up_read(&sb->s_umount); | |
562 | ||
563 | spin_lock(&sb_lock); | |
564 | if (p) | |
565 | __put_super(p); | |
566 | p = sb; | |
567 | } | |
568 | if (p) | |
569 | __put_super(p); | |
570 | spin_unlock(&sb_lock); | |
571 | } | |
572 | ||
573 | /** | |
574 | * iterate_supers_type - call function for superblocks of given type | |
575 | * @type: fs type | |
576 | * @f: function to call | |
577 | * @arg: argument to pass to it | |
578 | * | |
579 | * Scans the superblock list and calls given function, passing it | |
580 | * locked superblock and given argument. | |
581 | */ | |
582 | void iterate_supers_type(struct file_system_type *type, | |
583 | void (*f)(struct super_block *, void *), void *arg) | |
584 | { | |
585 | struct super_block *sb, *p = NULL; | |
586 | struct hlist_node *node; | |
587 | ||
588 | spin_lock(&sb_lock); | |
589 | hlist_for_each_entry(sb, node, &type->fs_supers, s_instances) { | |
590 | sb->s_count++; | |
591 | spin_unlock(&sb_lock); | |
592 | ||
593 | down_read(&sb->s_umount); | |
594 | if (sb->s_root && (sb->s_flags & MS_BORN)) | |
595 | f(sb, arg); | |
596 | up_read(&sb->s_umount); | |
597 | ||
598 | spin_lock(&sb_lock); | |
599 | if (p) | |
600 | __put_super(p); | |
601 | p = sb; | |
602 | } | |
603 | if (p) | |
604 | __put_super(p); | |
605 | spin_unlock(&sb_lock); | |
606 | } | |
607 | ||
608 | EXPORT_SYMBOL(iterate_supers_type); | |
609 | ||
610 | /** | |
611 | * get_super - get the superblock of a device | |
612 | * @bdev: device to get the superblock for | |
613 | * | |
614 | * Scans the superblock list and finds the superblock of the file system | |
615 | * mounted on the device given. %NULL is returned if no match is found. | |
616 | */ | |
617 | ||
618 | struct super_block *get_super(struct block_device *bdev) | |
619 | { | |
620 | struct super_block *sb; | |
621 | ||
622 | if (!bdev) | |
623 | return NULL; | |
624 | ||
625 | spin_lock(&sb_lock); | |
626 | rescan: | |
627 | list_for_each_entry(sb, &super_blocks, s_list) { | |
628 | if (hlist_unhashed(&sb->s_instances)) | |
629 | continue; | |
630 | if (sb->s_bdev == bdev) { | |
631 | sb->s_count++; | |
632 | spin_unlock(&sb_lock); | |
633 | down_read(&sb->s_umount); | |
634 | /* still alive? */ | |
635 | if (sb->s_root && (sb->s_flags & MS_BORN)) | |
636 | return sb; | |
637 | up_read(&sb->s_umount); | |
638 | /* nope, got unmounted */ | |
639 | spin_lock(&sb_lock); | |
640 | __put_super(sb); | |
641 | goto rescan; | |
642 | } | |
643 | } | |
644 | spin_unlock(&sb_lock); | |
645 | return NULL; | |
646 | } | |
647 | ||
648 | EXPORT_SYMBOL(get_super); | |
649 | ||
650 | /** | |
651 | * get_super_thawed - get thawed superblock of a device | |
652 | * @bdev: device to get the superblock for | |
653 | * | |
654 | * Scans the superblock list and finds the superblock of the file system | |
655 | * mounted on the device. The superblock is returned once it is thawed | |
656 | * (or immediately if it was not frozen). %NULL is returned if no match | |
657 | * is found. | |
658 | */ | |
659 | struct super_block *get_super_thawed(struct block_device *bdev) | |
660 | { | |
661 | while (1) { | |
662 | struct super_block *s = get_super(bdev); | |
663 | if (!s || s->s_writers.frozen == SB_UNFROZEN) | |
664 | return s; | |
665 | up_read(&s->s_umount); | |
666 | wait_event(s->s_writers.wait_unfrozen, | |
667 | s->s_writers.frozen == SB_UNFROZEN); | |
668 | put_super(s); | |
669 | } | |
670 | } | |
671 | EXPORT_SYMBOL(get_super_thawed); | |
672 | ||
673 | /** | |
674 | * get_active_super - get an active reference to the superblock of a device | |
675 | * @bdev: device to get the superblock for | |
676 | * | |
677 | * Scans the superblock list and finds the superblock of the file system | |
678 | * mounted on the device given. Returns the superblock with an active | |
679 | * reference or %NULL if none was found. | |
680 | */ | |
681 | struct super_block *get_active_super(struct block_device *bdev) | |
682 | { | |
683 | struct super_block *sb; | |
684 | ||
685 | if (!bdev) | |
686 | return NULL; | |
687 | ||
688 | restart: | |
689 | spin_lock(&sb_lock); | |
690 | list_for_each_entry(sb, &super_blocks, s_list) { | |
691 | if (hlist_unhashed(&sb->s_instances)) | |
692 | continue; | |
693 | if (sb->s_bdev == bdev) { | |
694 | if (grab_super(sb)) /* drops sb_lock */ | |
695 | return sb; | |
696 | else | |
697 | goto restart; | |
698 | } | |
699 | } | |
700 | spin_unlock(&sb_lock); | |
701 | return NULL; | |
702 | } | |
703 | ||
704 | struct super_block *user_get_super(dev_t dev) | |
705 | { | |
706 | struct super_block *sb; | |
707 | ||
708 | spin_lock(&sb_lock); | |
709 | rescan: | |
710 | list_for_each_entry(sb, &super_blocks, s_list) { | |
711 | if (hlist_unhashed(&sb->s_instances)) | |
712 | continue; | |
713 | if (sb->s_dev == dev) { | |
714 | sb->s_count++; | |
715 | spin_unlock(&sb_lock); | |
716 | down_read(&sb->s_umount); | |
717 | /* still alive? */ | |
718 | if (sb->s_root && (sb->s_flags & MS_BORN)) | |
719 | return sb; | |
720 | up_read(&sb->s_umount); | |
721 | /* nope, got unmounted */ | |
722 | spin_lock(&sb_lock); | |
723 | __put_super(sb); | |
724 | goto rescan; | |
725 | } | |
726 | } | |
727 | spin_unlock(&sb_lock); | |
728 | return NULL; | |
729 | } | |
730 | ||
731 | /** | |
732 | * do_remount_sb - asks filesystem to change mount options. | |
733 | * @sb: superblock in question | |
734 | * @flags: numeric part of options | |
735 | * @data: the rest of options | |
736 | * @force: whether or not to force the change | |
737 | * | |
738 | * Alters the mount options of a mounted file system. | |
739 | */ | |
740 | int do_remount_sb(struct super_block *sb, int flags, void *data, int force) | |
741 | { | |
742 | int retval; | |
743 | int remount_ro; | |
744 | ||
745 | if (sb->s_writers.frozen != SB_UNFROZEN) | |
746 | return -EBUSY; | |
747 | ||
748 | #ifdef CONFIG_BLOCK | |
749 | if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev)) | |
750 | return -EACCES; | |
751 | #endif | |
752 | ||
753 | if (flags & MS_RDONLY) | |
754 | acct_auto_close(sb); | |
755 | shrink_dcache_sb(sb); | |
756 | sync_filesystem(sb); | |
757 | ||
758 | remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY); | |
759 | ||
760 | /* If we are remounting RDONLY and current sb is read/write, | |
761 | make sure there are no rw files opened */ | |
762 | if (remount_ro) { | |
763 | if (force) { | |
764 | mark_files_ro(sb); | |
765 | } else { | |
766 | retval = sb_prepare_remount_readonly(sb); | |
767 | if (retval) | |
768 | return retval; | |
769 | } | |
770 | } | |
771 | ||
772 | if (sb->s_op->remount_fs) { | |
773 | retval = sb->s_op->remount_fs(sb, &flags, data); | |
774 | if (retval) { | |
775 | if (!force) | |
776 | goto cancel_readonly; | |
777 | /* If forced remount, go ahead despite any errors */ | |
778 | WARN(1, "forced remount of a %s fs returned %i\n", | |
779 | sb->s_type->name, retval); | |
780 | } | |
781 | } | |
782 | sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK); | |
783 | /* Needs to be ordered wrt mnt_is_readonly() */ | |
784 | smp_wmb(); | |
785 | sb->s_readonly_remount = 0; | |
786 | ||
787 | /* | |
788 | * Some filesystems modify their metadata via some other path than the | |
789 | * bdev buffer cache (eg. use a private mapping, or directories in | |
790 | * pagecache, etc). Also file data modifications go via their own | |
791 | * mappings. So If we try to mount readonly then copy the filesystem | |
792 | * from bdev, we could get stale data, so invalidate it to give a best | |
793 | * effort at coherency. | |
794 | */ | |
795 | if (remount_ro && sb->s_bdev) | |
796 | invalidate_bdev(sb->s_bdev); | |
797 | return 0; | |
798 | ||
799 | cancel_readonly: | |
800 | sb->s_readonly_remount = 0; | |
801 | return retval; | |
802 | } | |
803 | ||
804 | static void do_emergency_remount(struct work_struct *work) | |
805 | { | |
806 | struct super_block *sb, *p = NULL; | |
807 | ||
808 | spin_lock(&sb_lock); | |
809 | list_for_each_entry(sb, &super_blocks, s_list) { | |
810 | if (hlist_unhashed(&sb->s_instances)) | |
811 | continue; | |
812 | sb->s_count++; | |
813 | spin_unlock(&sb_lock); | |
814 | down_write(&sb->s_umount); | |
815 | if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) && | |
816 | !(sb->s_flags & MS_RDONLY)) { | |
817 | /* | |
818 | * What lock protects sb->s_flags?? | |
819 | */ | |
820 | do_remount_sb(sb, MS_RDONLY, NULL, 1); | |
821 | } | |
822 | up_write(&sb->s_umount); | |
823 | spin_lock(&sb_lock); | |
824 | if (p) | |
825 | __put_super(p); | |
826 | p = sb; | |
827 | } | |
828 | if (p) | |
829 | __put_super(p); | |
830 | spin_unlock(&sb_lock); | |
831 | kfree(work); | |
832 | printk("Emergency Remount complete\n"); | |
833 | } | |
834 | ||
835 | void emergency_remount(void) | |
836 | { | |
837 | struct work_struct *work; | |
838 | ||
839 | work = kmalloc(sizeof(*work), GFP_ATOMIC); | |
840 | if (work) { | |
841 | INIT_WORK(work, do_emergency_remount); | |
842 | schedule_work(work); | |
843 | } | |
844 | } | |
845 | ||
846 | /* | |
847 | * Unnamed block devices are dummy devices used by virtual | |
848 | * filesystems which don't use real block-devices. -- jrs | |
849 | */ | |
850 | ||
851 | static DEFINE_IDA(unnamed_dev_ida); | |
852 | static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */ | |
853 | static int unnamed_dev_start = 0; /* don't bother trying below it */ | |
854 | ||
855 | int get_anon_bdev(dev_t *p) | |
856 | { | |
857 | int dev; | |
858 | int error; | |
859 | ||
860 | retry: | |
861 | if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0) | |
862 | return -ENOMEM; | |
863 | spin_lock(&unnamed_dev_lock); | |
864 | error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev); | |
865 | if (!error) | |
866 | unnamed_dev_start = dev + 1; | |
867 | spin_unlock(&unnamed_dev_lock); | |
868 | if (error == -EAGAIN) | |
869 | /* We raced and lost with another CPU. */ | |
870 | goto retry; | |
871 | else if (error) | |
872 | return -EAGAIN; | |
873 | ||
874 | if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) { | |
875 | spin_lock(&unnamed_dev_lock); | |
876 | ida_remove(&unnamed_dev_ida, dev); | |
877 | if (unnamed_dev_start > dev) | |
878 | unnamed_dev_start = dev; | |
879 | spin_unlock(&unnamed_dev_lock); | |
880 | return -EMFILE; | |
881 | } | |
882 | *p = MKDEV(0, dev & MINORMASK); | |
883 | return 0; | |
884 | } | |
885 | EXPORT_SYMBOL(get_anon_bdev); | |
886 | ||
887 | void free_anon_bdev(dev_t dev) | |
888 | { | |
889 | int slot = MINOR(dev); | |
890 | spin_lock(&unnamed_dev_lock); | |
891 | ida_remove(&unnamed_dev_ida, slot); | |
892 | if (slot < unnamed_dev_start) | |
893 | unnamed_dev_start = slot; | |
894 | spin_unlock(&unnamed_dev_lock); | |
895 | } | |
896 | EXPORT_SYMBOL(free_anon_bdev); | |
897 | ||
898 | int set_anon_super(struct super_block *s, void *data) | |
899 | { | |
900 | int error = get_anon_bdev(&s->s_dev); | |
901 | if (!error) | |
902 | s->s_bdi = &noop_backing_dev_info; | |
903 | return error; | |
904 | } | |
905 | ||
906 | EXPORT_SYMBOL(set_anon_super); | |
907 | ||
908 | void kill_anon_super(struct super_block *sb) | |
909 | { | |
910 | dev_t dev = sb->s_dev; | |
911 | generic_shutdown_super(sb); | |
912 | free_anon_bdev(dev); | |
913 | } | |
914 | ||
915 | EXPORT_SYMBOL(kill_anon_super); | |
916 | ||
917 | void kill_litter_super(struct super_block *sb) | |
918 | { | |
919 | if (sb->s_root) | |
920 | d_genocide(sb->s_root); | |
921 | kill_anon_super(sb); | |
922 | } | |
923 | ||
924 | EXPORT_SYMBOL(kill_litter_super); | |
925 | ||
926 | static int ns_test_super(struct super_block *sb, void *data) | |
927 | { | |
928 | return sb->s_fs_info == data; | |
929 | } | |
930 | ||
931 | static int ns_set_super(struct super_block *sb, void *data) | |
932 | { | |
933 | sb->s_fs_info = data; | |
934 | return set_anon_super(sb, NULL); | |
935 | } | |
936 | ||
937 | struct dentry *mount_ns(struct file_system_type *fs_type, int flags, | |
938 | void *data, int (*fill_super)(struct super_block *, void *, int)) | |
939 | { | |
940 | struct super_block *sb; | |
941 | ||
942 | sb = sget(fs_type, ns_test_super, ns_set_super, flags, data); | |
943 | if (IS_ERR(sb)) | |
944 | return ERR_CAST(sb); | |
945 | ||
946 | if (!sb->s_root) { | |
947 | int err; | |
948 | err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0); | |
949 | if (err) { | |
950 | deactivate_locked_super(sb); | |
951 | return ERR_PTR(err); | |
952 | } | |
953 | ||
954 | sb->s_flags |= MS_ACTIVE; | |
955 | } | |
956 | ||
957 | return dget(sb->s_root); | |
958 | } | |
959 | ||
960 | EXPORT_SYMBOL(mount_ns); | |
961 | ||
962 | #ifdef CONFIG_BLOCK | |
963 | static int set_bdev_super(struct super_block *s, void *data) | |
964 | { | |
965 | s->s_bdev = data; | |
966 | s->s_dev = s->s_bdev->bd_dev; | |
967 | ||
968 | /* | |
969 | * We set the bdi here to the queue backing, file systems can | |
970 | * overwrite this in ->fill_super() | |
971 | */ | |
972 | s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info; | |
973 | return 0; | |
974 | } | |
975 | ||
976 | static int test_bdev_super(struct super_block *s, void *data) | |
977 | { | |
978 | return (void *)s->s_bdev == data; | |
979 | } | |
980 | ||
981 | struct dentry *mount_bdev(struct file_system_type *fs_type, | |
982 | int flags, const char *dev_name, void *data, | |
983 | int (*fill_super)(struct super_block *, void *, int)) | |
984 | { | |
985 | struct block_device *bdev; | |
986 | struct super_block *s; | |
987 | fmode_t mode = FMODE_READ | FMODE_EXCL; | |
988 | int error = 0; | |
989 | ||
990 | if (!(flags & MS_RDONLY)) | |
991 | mode |= FMODE_WRITE; | |
992 | ||
993 | bdev = blkdev_get_by_path(dev_name, mode, fs_type); | |
994 | if (IS_ERR(bdev)) | |
995 | return ERR_CAST(bdev); | |
996 | ||
997 | /* | |
998 | * once the super is inserted into the list by sget, s_umount | |
999 | * will protect the lockfs code from trying to start a snapshot | |
1000 | * while we are mounting | |
1001 | */ | |
1002 | mutex_lock(&bdev->bd_fsfreeze_mutex); | |
1003 | if (bdev->bd_fsfreeze_count > 0) { | |
1004 | mutex_unlock(&bdev->bd_fsfreeze_mutex); | |
1005 | error = -EBUSY; | |
1006 | goto error_bdev; | |
1007 | } | |
1008 | s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC, | |
1009 | bdev); | |
1010 | mutex_unlock(&bdev->bd_fsfreeze_mutex); | |
1011 | if (IS_ERR(s)) | |
1012 | goto error_s; | |
1013 | ||
1014 | if (s->s_root) { | |
1015 | if ((flags ^ s->s_flags) & MS_RDONLY) { | |
1016 | deactivate_locked_super(s); | |
1017 | error = -EBUSY; | |
1018 | goto error_bdev; | |
1019 | } | |
1020 | ||
1021 | /* | |
1022 | * s_umount nests inside bd_mutex during | |
1023 | * __invalidate_device(). blkdev_put() acquires | |
1024 | * bd_mutex and can't be called under s_umount. Drop | |
1025 | * s_umount temporarily. This is safe as we're | |
1026 | * holding an active reference. | |
1027 | */ | |
1028 | up_write(&s->s_umount); | |
1029 | blkdev_put(bdev, mode); | |
1030 | down_write(&s->s_umount); | |
1031 | } else { | |
1032 | char b[BDEVNAME_SIZE]; | |
1033 | ||
1034 | s->s_mode = mode; | |
1035 | strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id)); | |
1036 | sb_set_blocksize(s, block_size(bdev)); | |
1037 | error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); | |
1038 | if (error) { | |
1039 | deactivate_locked_super(s); | |
1040 | goto error; | |
1041 | } | |
1042 | ||
1043 | s->s_flags |= MS_ACTIVE; | |
1044 | bdev->bd_super = s; | |
1045 | } | |
1046 | ||
1047 | return dget(s->s_root); | |
1048 | ||
1049 | error_s: | |
1050 | error = PTR_ERR(s); | |
1051 | error_bdev: | |
1052 | blkdev_put(bdev, mode); | |
1053 | error: | |
1054 | return ERR_PTR(error); | |
1055 | } | |
1056 | EXPORT_SYMBOL(mount_bdev); | |
1057 | ||
1058 | void kill_block_super(struct super_block *sb) | |
1059 | { | |
1060 | struct block_device *bdev = sb->s_bdev; | |
1061 | fmode_t mode = sb->s_mode; | |
1062 | ||
1063 | bdev->bd_super = NULL; | |
1064 | generic_shutdown_super(sb); | |
1065 | sync_blockdev(bdev); | |
1066 | WARN_ON_ONCE(!(mode & FMODE_EXCL)); | |
1067 | blkdev_put(bdev, mode | FMODE_EXCL); | |
1068 | } | |
1069 | ||
1070 | EXPORT_SYMBOL(kill_block_super); | |
1071 | #endif | |
1072 | ||
1073 | struct dentry *mount_nodev(struct file_system_type *fs_type, | |
1074 | int flags, void *data, | |
1075 | int (*fill_super)(struct super_block *, void *, int)) | |
1076 | { | |
1077 | int error; | |
1078 | struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL); | |
1079 | ||
1080 | if (IS_ERR(s)) | |
1081 | return ERR_CAST(s); | |
1082 | ||
1083 | error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); | |
1084 | if (error) { | |
1085 | deactivate_locked_super(s); | |
1086 | return ERR_PTR(error); | |
1087 | } | |
1088 | s->s_flags |= MS_ACTIVE; | |
1089 | return dget(s->s_root); | |
1090 | } | |
1091 | EXPORT_SYMBOL(mount_nodev); | |
1092 | ||
1093 | static int compare_single(struct super_block *s, void *p) | |
1094 | { | |
1095 | return 1; | |
1096 | } | |
1097 | ||
1098 | struct dentry *mount_single(struct file_system_type *fs_type, | |
1099 | int flags, void *data, | |
1100 | int (*fill_super)(struct super_block *, void *, int)) | |
1101 | { | |
1102 | struct super_block *s; | |
1103 | int error; | |
1104 | ||
1105 | s = sget(fs_type, compare_single, set_anon_super, flags, NULL); | |
1106 | if (IS_ERR(s)) | |
1107 | return ERR_CAST(s); | |
1108 | if (!s->s_root) { | |
1109 | error = fill_super(s, data, flags & MS_SILENT ? 1 : 0); | |
1110 | if (error) { | |
1111 | deactivate_locked_super(s); | |
1112 | return ERR_PTR(error); | |
1113 | } | |
1114 | s->s_flags |= MS_ACTIVE; | |
1115 | } else { | |
1116 | do_remount_sb(s, flags, data, 0); | |
1117 | } | |
1118 | return dget(s->s_root); | |
1119 | } | |
1120 | EXPORT_SYMBOL(mount_single); | |
1121 | ||
1122 | struct dentry * | |
1123 | mount_fs(struct file_system_type *type, int flags, const char *name, void *data) | |
1124 | { | |
1125 | struct dentry *root; | |
1126 | struct super_block *sb; | |
1127 | char *secdata = NULL; | |
1128 | int error = -ENOMEM; | |
1129 | ||
1130 | if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) { | |
1131 | secdata = alloc_secdata(); | |
1132 | if (!secdata) | |
1133 | goto out; | |
1134 | ||
1135 | error = security_sb_copy_data(data, secdata); | |
1136 | if (error) | |
1137 | goto out_free_secdata; | |
1138 | } | |
1139 | ||
1140 | root = type->mount(type, flags, name, data); | |
1141 | if (IS_ERR(root)) { | |
1142 | error = PTR_ERR(root); | |
1143 | goto out_free_secdata; | |
1144 | } | |
1145 | sb = root->d_sb; | |
1146 | BUG_ON(!sb); | |
1147 | WARN_ON(!sb->s_bdi); | |
1148 | WARN_ON(sb->s_bdi == &default_backing_dev_info); | |
1149 | sb->s_flags |= MS_BORN; | |
1150 | ||
1151 | error = security_sb_kern_mount(sb, flags, secdata); | |
1152 | if (error) | |
1153 | goto out_sb; | |
1154 | ||
1155 | /* | |
1156 | * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE | |
1157 | * but s_maxbytes was an unsigned long long for many releases. Throw | |
1158 | * this warning for a little while to try and catch filesystems that | |
1159 | * violate this rule. | |
1160 | */ | |
1161 | WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to " | |
1162 | "negative value (%lld)\n", type->name, sb->s_maxbytes); | |
1163 | ||
1164 | up_write(&sb->s_umount); | |
1165 | free_secdata(secdata); | |
1166 | return root; | |
1167 | out_sb: | |
1168 | dput(root); | |
1169 | deactivate_locked_super(sb); | |
1170 | out_free_secdata: | |
1171 | free_secdata(secdata); | |
1172 | out: | |
1173 | return ERR_PTR(error); | |
1174 | } | |
1175 | ||
1176 | /* | |
1177 | * This is an internal function, please use sb_end_{write,pagefault,intwrite} | |
1178 | * instead. | |
1179 | */ | |
1180 | void __sb_end_write(struct super_block *sb, int level) | |
1181 | { | |
1182 | percpu_counter_dec(&sb->s_writers.counter[level-1]); | |
1183 | /* | |
1184 | * Make sure s_writers are updated before we wake up waiters in | |
1185 | * freeze_super(). | |
1186 | */ | |
1187 | smp_mb(); | |
1188 | if (waitqueue_active(&sb->s_writers.wait)) | |
1189 | wake_up(&sb->s_writers.wait); | |
1190 | rwsem_release(&sb->s_writers.lock_map[level-1], 1, _RET_IP_); | |
1191 | } | |
1192 | EXPORT_SYMBOL(__sb_end_write); | |
1193 | ||
1194 | #ifdef CONFIG_LOCKDEP | |
1195 | /* | |
1196 | * We want lockdep to tell us about possible deadlocks with freezing but | |
1197 | * it's it bit tricky to properly instrument it. Getting a freeze protection | |
1198 | * works as getting a read lock but there are subtle problems. XFS for example | |
1199 | * gets freeze protection on internal level twice in some cases, which is OK | |
1200 | * only because we already hold a freeze protection also on higher level. Due | |
1201 | * to these cases we have to tell lockdep we are doing trylock when we | |
1202 | * already hold a freeze protection for a higher freeze level. | |
1203 | */ | |
1204 | static void acquire_freeze_lock(struct super_block *sb, int level, bool trylock, | |
1205 | unsigned long ip) | |
1206 | { | |
1207 | int i; | |
1208 | ||
1209 | if (!trylock) { | |
1210 | for (i = 0; i < level - 1; i++) | |
1211 | if (lock_is_held(&sb->s_writers.lock_map[i])) { | |
1212 | trylock = true; | |
1213 | break; | |
1214 | } | |
1215 | } | |
1216 | rwsem_acquire_read(&sb->s_writers.lock_map[level-1], 0, trylock, ip); | |
1217 | } | |
1218 | #endif | |
1219 | ||
1220 | /* | |
1221 | * This is an internal function, please use sb_start_{write,pagefault,intwrite} | |
1222 | * instead. | |
1223 | */ | |
1224 | int __sb_start_write(struct super_block *sb, int level, bool wait) | |
1225 | { | |
1226 | retry: | |
1227 | if (unlikely(sb->s_writers.frozen >= level)) { | |
1228 | if (!wait) | |
1229 | return 0; | |
1230 | wait_event(sb->s_writers.wait_unfrozen, | |
1231 | sb->s_writers.frozen < level); | |
1232 | } | |
1233 | ||
1234 | #ifdef CONFIG_LOCKDEP | |
1235 | acquire_freeze_lock(sb, level, !wait, _RET_IP_); | |
1236 | #endif | |
1237 | percpu_counter_inc(&sb->s_writers.counter[level-1]); | |
1238 | /* | |
1239 | * Make sure counter is updated before we check for frozen. | |
1240 | * freeze_super() first sets frozen and then checks the counter. | |
1241 | */ | |
1242 | smp_mb(); | |
1243 | if (unlikely(sb->s_writers.frozen >= level)) { | |
1244 | __sb_end_write(sb, level); | |
1245 | goto retry; | |
1246 | } | |
1247 | return 1; | |
1248 | } | |
1249 | EXPORT_SYMBOL(__sb_start_write); | |
1250 | ||
1251 | /** | |
1252 | * sb_wait_write - wait until all writers to given file system finish | |
1253 | * @sb: the super for which we wait | |
1254 | * @level: type of writers we wait for (normal vs page fault) | |
1255 | * | |
1256 | * This function waits until there are no writers of given type to given file | |
1257 | * system. Caller of this function should make sure there can be no new writers | |
1258 | * of type @level before calling this function. Otherwise this function can | |
1259 | * livelock. | |
1260 | */ | |
1261 | static void sb_wait_write(struct super_block *sb, int level) | |
1262 | { | |
1263 | s64 writers; | |
1264 | ||
1265 | /* | |
1266 | * We just cycle-through lockdep here so that it does not complain | |
1267 | * about returning with lock to userspace | |
1268 | */ | |
1269 | rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_); | |
1270 | rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_); | |
1271 | ||
1272 | do { | |
1273 | DEFINE_WAIT(wait); | |
1274 | ||
1275 | /* | |
1276 | * We use a barrier in prepare_to_wait() to separate setting | |
1277 | * of frozen and checking of the counter | |
1278 | */ | |
1279 | prepare_to_wait(&sb->s_writers.wait, &wait, | |
1280 | TASK_UNINTERRUPTIBLE); | |
1281 | ||
1282 | writers = percpu_counter_sum(&sb->s_writers.counter[level-1]); | |
1283 | if (writers) | |
1284 | schedule(); | |
1285 | ||
1286 | finish_wait(&sb->s_writers.wait, &wait); | |
1287 | } while (writers); | |
1288 | } | |
1289 | ||
1290 | /** | |
1291 | * freeze_super - lock the filesystem and force it into a consistent state | |
1292 | * @sb: the super to lock | |
1293 | * | |
1294 | * Syncs the super to make sure the filesystem is consistent and calls the fs's | |
1295 | * freeze_fs. Subsequent calls to this without first thawing the fs will return | |
1296 | * -EBUSY. | |
1297 | * | |
1298 | * During this function, sb->s_writers.frozen goes through these values: | |
1299 | * | |
1300 | * SB_UNFROZEN: File system is normal, all writes progress as usual. | |
1301 | * | |
1302 | * SB_FREEZE_WRITE: The file system is in the process of being frozen. New | |
1303 | * writes should be blocked, though page faults are still allowed. We wait for | |
1304 | * all writes to complete and then proceed to the next stage. | |
1305 | * | |
1306 | * SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked | |
1307 | * but internal fs threads can still modify the filesystem (although they | |
1308 | * should not dirty new pages or inodes), writeback can run etc. After waiting | |
1309 | * for all running page faults we sync the filesystem which will clean all | |
1310 | * dirty pages and inodes (no new dirty pages or inodes can be created when | |
1311 | * sync is running). | |
1312 | * | |
1313 | * SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs | |
1314 | * modification are blocked (e.g. XFS preallocation truncation on inode | |
1315 | * reclaim). This is usually implemented by blocking new transactions for | |
1316 | * filesystems that have them and need this additional guard. After all | |
1317 | * internal writers are finished we call ->freeze_fs() to finish filesystem | |
1318 | * freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is | |
1319 | * mostly auxiliary for filesystems to verify they do not modify frozen fs. | |
1320 | * | |
1321 | * sb->s_writers.frozen is protected by sb->s_umount. | |
1322 | */ | |
1323 | int freeze_super(struct super_block *sb) | |
1324 | { | |
1325 | int ret; | |
1326 | ||
1327 | atomic_inc(&sb->s_active); | |
1328 | down_write(&sb->s_umount); | |
1329 | if (sb->s_writers.frozen != SB_UNFROZEN) { | |
1330 | deactivate_locked_super(sb); | |
1331 | return -EBUSY; | |
1332 | } | |
1333 | ||
1334 | if (!(sb->s_flags & MS_BORN)) { | |
1335 | up_write(&sb->s_umount); | |
1336 | return 0; /* sic - it's "nothing to do" */ | |
1337 | } | |
1338 | ||
1339 | if (sb->s_flags & MS_RDONLY) { | |
1340 | /* Nothing to do really... */ | |
1341 | sb->s_writers.frozen = SB_FREEZE_COMPLETE; | |
1342 | up_write(&sb->s_umount); | |
1343 | return 0; | |
1344 | } | |
1345 | ||
1346 | /* From now on, no new normal writers can start */ | |
1347 | sb->s_writers.frozen = SB_FREEZE_WRITE; | |
1348 | smp_wmb(); | |
1349 | ||
1350 | /* Release s_umount to preserve sb_start_write -> s_umount ordering */ | |
1351 | up_write(&sb->s_umount); | |
1352 | ||
1353 | sb_wait_write(sb, SB_FREEZE_WRITE); | |
1354 | ||
1355 | /* Now we go and block page faults... */ | |
1356 | down_write(&sb->s_umount); | |
1357 | sb->s_writers.frozen = SB_FREEZE_PAGEFAULT; | |
1358 | smp_wmb(); | |
1359 | ||
1360 | sb_wait_write(sb, SB_FREEZE_PAGEFAULT); | |
1361 | ||
1362 | /* All writers are done so after syncing there won't be dirty data */ | |
1363 | sync_filesystem(sb); | |
1364 | ||
1365 | /* Now wait for internal filesystem counter */ | |
1366 | sb->s_writers.frozen = SB_FREEZE_FS; | |
1367 | smp_wmb(); | |
1368 | sb_wait_write(sb, SB_FREEZE_FS); | |
1369 | ||
1370 | if (sb->s_op->freeze_fs) { | |
1371 | ret = sb->s_op->freeze_fs(sb); | |
1372 | if (ret) { | |
1373 | printk(KERN_ERR | |
1374 | "VFS:Filesystem freeze failed\n"); | |
1375 | sb->s_writers.frozen = SB_UNFROZEN; | |
1376 | smp_wmb(); | |
1377 | wake_up(&sb->s_writers.wait_unfrozen); | |
1378 | deactivate_locked_super(sb); | |
1379 | return ret; | |
1380 | } | |
1381 | } | |
1382 | /* | |
1383 | * This is just for debugging purposes so that fs can warn if it | |
1384 | * sees write activity when frozen is set to SB_FREEZE_COMPLETE. | |
1385 | */ | |
1386 | sb->s_writers.frozen = SB_FREEZE_COMPLETE; | |
1387 | up_write(&sb->s_umount); | |
1388 | return 0; | |
1389 | } | |
1390 | EXPORT_SYMBOL(freeze_super); | |
1391 | ||
1392 | /** | |
1393 | * thaw_super -- unlock filesystem | |
1394 | * @sb: the super to thaw | |
1395 | * | |
1396 | * Unlocks the filesystem and marks it writeable again after freeze_super(). | |
1397 | */ | |
1398 | int thaw_super(struct super_block *sb) | |
1399 | { | |
1400 | int error; | |
1401 | ||
1402 | down_write(&sb->s_umount); | |
1403 | if (sb->s_writers.frozen == SB_UNFROZEN) { | |
1404 | up_write(&sb->s_umount); | |
1405 | return -EINVAL; | |
1406 | } | |
1407 | ||
1408 | if (sb->s_flags & MS_RDONLY) | |
1409 | goto out; | |
1410 | ||
1411 | if (sb->s_op->unfreeze_fs) { | |
1412 | error = sb->s_op->unfreeze_fs(sb); | |
1413 | if (error) { | |
1414 | printk(KERN_ERR | |
1415 | "VFS:Filesystem thaw failed\n"); | |
1416 | up_write(&sb->s_umount); | |
1417 | return error; | |
1418 | } | |
1419 | } | |
1420 | ||
1421 | out: | |
1422 | sb->s_writers.frozen = SB_UNFROZEN; | |
1423 | smp_wmb(); | |
1424 | wake_up(&sb->s_writers.wait_unfrozen); | |
1425 | deactivate_locked_super(sb); | |
1426 | ||
1427 | return 0; | |
1428 | } | |
1429 | EXPORT_SYMBOL(thaw_super); |