Kernel

Kernel Git Source Tree

Root/fs/super.c

Source at commit 9845c1745d3d531a5b9544f5322c62bfb4d4e9bc created 1 year 2 months ago. By Xiangfu, rtc: jz4740 fix hwclock give time out
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/module.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 "internal.h"
36
37
38	LIST_HEAD(super_blocks);
39	DEFINE_SPINLOCK(sb_lock);
40
41	/*
42	* One thing we have to be careful of with a per-sb shrinker is that we don't
43	* drop the last active reference to the superblock from within the shrinker.
44	* If that happens we could trigger unregistering the shrinker from within the
45	* shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
46	* take a passive reference to the superblock to avoid this from occurring.
47	*/
48	static int prune_super(struct shrinker shrink, struct shrink_control sc)
49	{
50	struct super_block *sb;
51	int fs_objects = 0;
52	int total_objects;
53
54	sb = container_of(shrink, struct super_block, s_shrink);
55
56	/*
57	* Deadlock avoidance. We may hold various FS locks, and we don't want
58	* to recurse into the FS that called us in clear_inode() and friends..
59	*/
60	if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS))
61	return -1;
62
63	if (!grab_super_passive(sb))
64	return !sc->nr_to_scan ? 0 : -1;
65
66	if (sb->s_op && sb->s_op->nr_cached_objects)
67	fs_objects = sb->s_op->nr_cached_objects(sb);
68
69	total_objects = sb->s_nr_dentry_unused +
70	sb->s_nr_inodes_unused + fs_objects + 1;
71
72	if (sc->nr_to_scan) {
73	int dentries;
74	int inodes;
75
76	/* proportion the scan between the caches */
77	dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) /
78	total_objects;
79	inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) /
80	total_objects;
81	if (fs_objects)
82	fs_objects = (sc->nr_to_scan * fs_objects) /
83	total_objects;
84	/*
85	* prune the dcache first as the icache is pinned by it, then
86	* prune the icache, followed by the filesystem specific caches
87	*/
88	prune_dcache_sb(sb, dentries);
89	prune_icache_sb(sb, inodes);
90
91	if (fs_objects && sb->s_op->free_cached_objects) {
92	sb->s_op->free_cached_objects(sb, fs_objects);
93	fs_objects = sb->s_op->nr_cached_objects(sb);
94	}
95	total_objects = sb->s_nr_dentry_unused +
96	sb->s_nr_inodes_unused + fs_objects;
97	}
98
99	total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure;
100	drop_super(sb);
101	return total_objects;
102	}
103
104	/**
105	* alloc_super - create new superblock
106	* @type: filesystem type superblock should belong to
107	*
108	* Allocates and initializes a new &struct super_block. alloc_super()
109	* returns a pointer new superblock or %NULL if allocation had failed.
110	*/
111	static struct super_block alloc_super(struct file_system_type type)
112	{
113	struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
114	static const struct super_operations default_op;
115
116	if (s) {
117	if (security_sb_alloc(s)) {
118	kfree(s);
119	s = NULL;
120	goto out;
121	}
122	#ifdef CONFIG_SMP
123	s->s_files = alloc_percpu(struct list_head);
124	if (!s->s_files) {
125	security_sb_free(s);
126	kfree(s);
127	s = NULL;
128	goto out;
129	} else {
130	int i;
131
132	for_each_possible_cpu(i)
133	INIT_LIST_HEAD(per_cpu_ptr(s->s_files, i));
134	}
135	#else
136	INIT_LIST_HEAD(&s->s_files);
137	#endif
138	s->s_bdi = &default_backing_dev_info;
139	INIT_LIST_HEAD(&s->s_instances);
140	INIT_HLIST_BL_HEAD(&s->s_anon);
141	INIT_LIST_HEAD(&s->s_inodes);
142	INIT_LIST_HEAD(&s->s_dentry_lru);
143	INIT_LIST_HEAD(&s->s_inode_lru);
144	spin_lock_init(&s->s_inode_lru_lock);
145	init_rwsem(&s->s_umount);
146	mutex_init(&s->s_lock);
147	lockdep_set_class(&s->s_umount, &type->s_umount_key);
148	/*
149	* The locking rules for s_lock are up to the
150	* filesystem. For example ext3fs has different
151	* lock ordering than usbfs:
152	*/
153	lockdep_set_class(&s->s_lock, &type->s_lock_key);
154	/*
155	* sget() can have s_umount recursion.
156	*
157	* When it cannot find a suitable sb, it allocates a new
158	* one (this one), and tries again to find a suitable old
159	* one.
160	*
161	* In case that succeeds, it will acquire the s_umount
162	* lock of the old one. Since these are clearly distrinct
163	* locks, and this object isn't exposed yet, there's no
164	* risk of deadlocks.
165	*
166	* Annotate this by putting this lock in a different
167	* subclass.
168	*/
169	down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
170	s->s_count = 1;
171	atomic_set(&s->s_active, 1);
172	mutex_init(&s->s_vfs_rename_mutex);
173	lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
174	mutex_init(&s->s_dquot.dqio_mutex);
175	mutex_init(&s->s_dquot.dqonoff_mutex);
176	init_rwsem(&s->s_dquot.dqptr_sem);
177	init_waitqueue_head(&s->s_wait_unfrozen);
178	s->s_maxbytes = MAX_NON_LFS;
179	s->s_op = &default_op;
180	s->s_time_gran = 1000000000;
181	s->cleancache_poolid = -1;
182
183	s->s_shrink.seeks = DEFAULT_SEEKS;
184	s->s_shrink.shrink = prune_super;
185	s->s_shrink.batch = 1024;
186	}
187	out:
188	return s;
189	}
190
191	/**
192	* destroy_super - frees a superblock
193	* @s: superblock to free
194	*
195	* Frees a superblock.
196	*/
197	static inline void destroy_super(struct super_block *s)
198	{
199	#ifdef CONFIG_SMP
200	free_percpu(s->s_files);
201	#endif
202	security_sb_free(s);
203	kfree(s->s_subtype);
204	kfree(s->s_options);
205	kfree(s);
206	}
207
208	/* Superblock refcounting */
209
210	/*
211	* Drop a superblock's refcount. The caller must hold sb_lock.
212	*/
213	void __put_super(struct super_block *sb)
214	{
215	if (!--sb->s_count) {
216	list_del_init(&sb->s_list);
217	destroy_super(sb);
218	}
219	}
220
221	/**
222	* put_super - drop a temporary reference to superblock
223	* @sb: superblock in question
224	*
225	* Drops a temporary reference, frees superblock if there's no
226	* references left.
227	*/
228	void put_super(struct super_block *sb)
229	{
230	spin_lock(&sb_lock);
231	__put_super(sb);
232	spin_unlock(&sb_lock);
233	}
234
235
236	/**
237	* deactivate_locked_super - drop an active reference to superblock
238	* @s: superblock to deactivate
239	*
240	* Drops an active reference to superblock, converting it into a temprory
241	* one if there is no other active references left. In that case we
242	* tell fs driver to shut it down and drop the temporary reference we
243	* had just acquired.
244	*
245	* Caller holds exclusive lock on superblock; that lock is released.
246	*/
247	void deactivate_locked_super(struct super_block *s)
248	{
249	struct file_system_type *fs = s->s_type;
250	if (atomic_dec_and_test(&s->s_active)) {
251	cleancache_flush_fs(s);
252	fs->kill_sb(s);
253
254	/* caches are now gone, we can safely kill the shrinker now */
255	unregister_shrinker(&s->s_shrink);
256
257	/*
258	* We need to call rcu_barrier so all the delayed rcu free
259	* inodes are flushed before we release the fs module.
260	*/
261	rcu_barrier();
262	put_filesystem(fs);
263	put_super(s);
264	} else {
265	up_write(&s->s_umount);
266	}
267	}
268
269	EXPORT_SYMBOL(deactivate_locked_super);
270
271	/**
272	* deactivate_super - drop an active reference to superblock
273	* @s: superblock to deactivate
274	*
275	* Variant of deactivate_locked_super(), except that superblock is not
276	* locked by caller. If we are going to drop the final active reference,
277	* lock will be acquired prior to that.
278	*/
279	void deactivate_super(struct super_block *s)
280	{
281	if (!atomic_add_unless(&s->s_active, -1, 1)) {
282	down_write(&s->s_umount);
283	deactivate_locked_super(s);
284	}
285	}
286
287	EXPORT_SYMBOL(deactivate_super);
288
289	/**
290	* grab_super - acquire an active reference
291	* @s: reference we are trying to make active
292	*
293	* Tries to acquire an active reference. grab_super() is used when we
294	* had just found a superblock in super_blocks or fs_type->fs_supers
295	* and want to turn it into a full-blown active reference. grab_super()
296	* is called with sb_lock held and drops it. Returns 1 in case of
297	* success, 0 if we had failed (superblock contents was already dead or
298	* dying when grab_super() had been called).
299	*/
300	static int grab_super(struct super_block *s) __releases(sb_lock)
301	{
302	if (atomic_inc_not_zero(&s->s_active)) {
303	spin_unlock(&sb_lock);
304	return 1;
305	}
306	/* it's going away */
307	s->s_count++;
308	spin_unlock(&sb_lock);
309	/* wait for it to die */
310	down_write(&s->s_umount);
311	up_write(&s->s_umount);
312	put_super(s);
313	return 0;
314	}
315
316	/*
317	* grab_super_passive - acquire a passive reference
318	* @s: reference we are trying to grab
319	*
320	* Tries to acquire a passive reference. This is used in places where we
321	* cannot take an active reference but we need to ensure that the
322	* superblock does not go away while we are working on it. It returns
323	* false if a reference was not gained, and returns true with the s_umount
324	* lock held in read mode if a reference is gained. On successful return,
325	* the caller must drop the s_umount lock and the passive reference when
326	* done.
327	*/
328	bool grab_super_passive(struct super_block *sb)
329	{
330	spin_lock(&sb_lock);
331	if (list_empty(&sb->s_instances)) {
332	spin_unlock(&sb_lock);
333	return false;
334	}
335
336	sb->s_count++;
337	spin_unlock(&sb_lock);
338
339	if (down_read_trylock(&sb->s_umount)) {
340	if (sb->s_root)
341	return true;
342	up_read(&sb->s_umount);
343	}
344
345	put_super(sb);
346	return false;
347	}
348
349	/*
350	* Superblock locking. We really ought to get rid of these two.
351	*/
352	void lock_super(struct super_block * sb)
353	{
354	mutex_lock(&sb->s_lock);
355	}
356
357	void unlock_super(struct super_block * sb)
358	{
359	mutex_unlock(&sb->s_lock);
360	}
361
362	EXPORT_SYMBOL(lock_super);
363	EXPORT_SYMBOL(unlock_super);
364
365	/**
366	* generic_shutdown_super - common helper for ->kill_sb()
367	* @sb: superblock to kill
368	*
369	* generic_shutdown_super() does all fs-independent work on superblock
370	* shutdown. Typical ->kill_sb() should pick all fs-specific objects
371	* that need destruction out of superblock, call generic_shutdown_super()
372	* and release aforementioned objects. Note: dentries and inodes _are_
373	* taken care of and do not need specific handling.
374	*
375	* Upon calling this function, the filesystem may no longer alter or
376	* rearrange the set of dentries belonging to this super_block, nor may it
377	* change the attachments of dentries to inodes.
378	*/
379	void generic_shutdown_super(struct super_block *sb)
380	{
381	const struct super_operations *sop = sb->s_op;
382
383	if (sb->s_root) {
384	shrink_dcache_for_umount(sb);
385	sync_filesystem(sb);
386	sb->s_flags &= ~MS_ACTIVE;
387
388	fsnotify_unmount_inodes(&sb->s_inodes);
389
390	evict_inodes(sb);
391
392	if (sop->put_super)
393	sop->put_super(sb);
394
395	if (!list_empty(&sb->s_inodes)) {
396	printk("VFS: Busy inodes after unmount of %s. "
397	"Self-destruct in 5 seconds. Have a nice day...\n",
398	sb->s_id);
399	}
400	}
401	spin_lock(&sb_lock);
402	/* should be initialized for __put_super_and_need_restart() */
403	list_del_init(&sb->s_instances);
404	spin_unlock(&sb_lock);
405	up_write(&sb->s_umount);
406	}
407
408	EXPORT_SYMBOL(generic_shutdown_super);
409
410	/**
411	* sget - find or create a superblock
412	* @type: filesystem type superblock should belong to
413	* @test: comparison callback
414	* @set: setup callback
415	* @data: argument to each of them
416	*/
417	struct super_block sget(struct file_system_type type,
418	int (test)(struct super_block ,void *),
419	int (set)(struct super_block ,void *),
420	void *data)
421	{
422	struct super_block *s = NULL;
423	struct super_block *old;
424	int err;
425
426	retry:
427	spin_lock(&sb_lock);
428	if (test) {
429	list_for_each_entry(old, &type->fs_supers, s_instances) {
430	if (!test(old, data))
431	continue;
432	if (!grab_super(old))
433	goto retry;
434	if (s) {
435	up_write(&s->s_umount);
436	destroy_super(s);
437	s = NULL;
438	}
439	down_write(&old->s_umount);
440	if (unlikely(!(old->s_flags & MS_BORN))) {
441	deactivate_locked_super(old);
442	goto retry;
443	}
444	return old;
445	}
446	}
447	if (!s) {
448	spin_unlock(&sb_lock);
449	s = alloc_super(type);
450	if (!s)
451	return ERR_PTR(-ENOMEM);
452	goto retry;
453	}
454
455	err = set(s, data);
456	if (err) {
457	spin_unlock(&sb_lock);
458	up_write(&s->s_umount);
459	destroy_super(s);
460	return ERR_PTR(err);
461	}
462	s->s_type = type;
463	strlcpy(s->s_id, type->name, sizeof(s->s_id));
464	list_add_tail(&s->s_list, &super_blocks);
465	list_add(&s->s_instances, &type->fs_supers);
466	spin_unlock(&sb_lock);
467	get_filesystem(type);
468	register_shrinker(&s->s_shrink);
469	return s;
470	}
471
472	EXPORT_SYMBOL(sget);
473
474	void drop_super(struct super_block *sb)
475	{
476	up_read(&sb->s_umount);
477	put_super(sb);
478	}
479
480	EXPORT_SYMBOL(drop_super);
481
482	/**
483	* sync_supers - helper for periodic superblock writeback
484	*
485	* Call the write_super method if present on all dirty superblocks in
486	* the system. This is for the periodic writeback used by most older
487	* filesystems. For data integrity superblock writeback use
488	* sync_filesystems() instead.
489	*
490	* Note: check the dirty flag before waiting, so we don't
491	* hold up the sync while mounting a device. (The newly
492	* mounted device won't need syncing.)
493	*/
494	void sync_supers(void)
495	{
496	struct super_block sb, p = NULL;
497
498	spin_lock(&sb_lock);
499	list_for_each_entry(sb, &super_blocks, s_list) {
500	if (list_empty(&sb->s_instances))
501	continue;
502	if (sb->s_op->write_super && sb->s_dirt) {
503	sb->s_count++;
504	spin_unlock(&sb_lock);
505
506	down_read(&sb->s_umount);
507	if (sb->s_root && sb->s_dirt)
508	sb->s_op->write_super(sb);
509	up_read(&sb->s_umount);
510
511	spin_lock(&sb_lock);
512	if (p)
513	__put_super(p);
514	p = sb;
515	}
516	}
517	if (p)
518	__put_super(p);
519	spin_unlock(&sb_lock);
520	}
521
522	/**
523	* iterate_supers - call function for all active superblocks
524	* @f: function to call
525	* @arg: argument to pass to it
526	*
527	* Scans the superblock list and calls given function, passing it
528	* locked superblock and given argument.
529	*/
530	void iterate_supers(void (f)(struct super_block , void ), void arg)
531	{
532	struct super_block sb, p = NULL;
533
534	spin_lock(&sb_lock);
535	list_for_each_entry(sb, &super_blocks, s_list) {
536	if (list_empty(&sb->s_instances))
537	continue;
538	sb->s_count++;
539	spin_unlock(&sb_lock);
540
541	down_read(&sb->s_umount);
542	if (sb->s_root)
543	f(sb, arg);
544	up_read(&sb->s_umount);
545
546	spin_lock(&sb_lock);
547	if (p)
548	__put_super(p);
549	p = sb;
550	}
551	if (p)
552	__put_super(p);
553	spin_unlock(&sb_lock);
554	}
555
556	/**
557	* iterate_supers_type - call function for superblocks of given type
558	* @type: fs type
559	* @f: function to call
560	* @arg: argument to pass to it
561	*
562	* Scans the superblock list and calls given function, passing it
563	* locked superblock and given argument.
564	*/
565	void iterate_supers_type(struct file_system_type *type,
566	void (f)(struct super_block , void ), void arg)
567	{
568	struct super_block sb, p = NULL;
569
570	spin_lock(&sb_lock);
571	list_for_each_entry(sb, &type->fs_supers, s_instances) {
572	sb->s_count++;
573	spin_unlock(&sb_lock);
574
575	down_read(&sb->s_umount);
576	if (sb->s_root)
577	f(sb, arg);
578	up_read(&sb->s_umount);
579
580	spin_lock(&sb_lock);
581	if (p)
582	__put_super(p);
583	p = sb;
584	}
585	if (p)
586	__put_super(p);
587	spin_unlock(&sb_lock);
588	}
589
590	EXPORT_SYMBOL(iterate_supers_type);
591
592	/**
593	* get_super - get the superblock of a device
594	* @bdev: device to get the superblock for
595	*
596	* Scans the superblock list and finds the superblock of the file system
597	* mounted on the device given. %NULL is returned if no match is found.
598	*/
599
600	struct super_block get_super(struct block_device bdev)
601	{
602	struct super_block *sb;
603
604	if (!bdev)
605	return NULL;
606
607	spin_lock(&sb_lock);
608	rescan:
609	list_for_each_entry(sb, &super_blocks, s_list) {
610	if (list_empty(&sb->s_instances))
611	continue;
612	if (sb->s_bdev == bdev) {
613	sb->s_count++;
614	spin_unlock(&sb_lock);
615	down_read(&sb->s_umount);
616	/* still alive? */
617	if (sb->s_root)
618	return sb;
619	up_read(&sb->s_umount);
620	/* nope, got unmounted */
621	spin_lock(&sb_lock);
622	__put_super(sb);
623	goto rescan;
624	}
625	}
626	spin_unlock(&sb_lock);
627	return NULL;
628	}
629
630	EXPORT_SYMBOL(get_super);
631
632	/**
633	* get_active_super - get an active reference to the superblock of a device
634	* @bdev: device to get the superblock for
635	*
636	* Scans the superblock list and finds the superblock of the file system
637	* mounted on the device given. Returns the superblock with an active
638	* reference or %NULL if none was found.
639	*/
640	struct super_block get_active_super(struct block_device bdev)
641	{
642	struct super_block *sb;
643
644	if (!bdev)
645	return NULL;
646
647	restart:
648	spin_lock(&sb_lock);
649	list_for_each_entry(sb, &super_blocks, s_list) {
650	if (list_empty(&sb->s_instances))
651	continue;
652	if (sb->s_bdev == bdev) {
653	if (grab_super(sb)) /* drops sb_lock */
654	return sb;
655	else
656	goto restart;
657	}
658	}
659	spin_unlock(&sb_lock);
660	return NULL;
661	}
662
663	struct super_block *user_get_super(dev_t dev)
664	{
665	struct super_block *sb;
666
667	spin_lock(&sb_lock);
668	rescan:
669	list_for_each_entry(sb, &super_blocks, s_list) {
670	if (list_empty(&sb->s_instances))
671	continue;
672	if (sb->s_dev == dev) {
673	sb->s_count++;
674	spin_unlock(&sb_lock);
675	down_read(&sb->s_umount);
676	/* still alive? */
677	if (sb->s_root)
678	return sb;
679	up_read(&sb->s_umount);
680	/* nope, got unmounted */
681	spin_lock(&sb_lock);
682	__put_super(sb);
683	goto rescan;
684	}
685	}
686	spin_unlock(&sb_lock);
687	return NULL;
688	}
689
690	/**
691	* do_remount_sb - asks filesystem to change mount options.
692	* @sb: superblock in question
693	* @flags: numeric part of options
694	* @data: the rest of options
695	* @force: whether or not to force the change
696	*
697	* Alters the mount options of a mounted file system.
698	*/
699	int do_remount_sb(struct super_block sb, int flags, void data, int force)
700	{
701	int retval;
702	int remount_ro;
703
704	if (sb->s_frozen != SB_UNFROZEN)
705	return -EBUSY;
706
707	#ifdef CONFIG_BLOCK
708	if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
709	return -EACCES;
710	#endif
711
712	if (flags & MS_RDONLY)
713	acct_auto_close(sb);
714	shrink_dcache_sb(sb);
715	sync_filesystem(sb);
716
717	remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
718
719	/* If we are remounting RDONLY and current sb is read/write,
720	make sure there are no rw files opened */
721	if (remount_ro) {
722	if (force)
723	mark_files_ro(sb);
724	else if (!fs_may_remount_ro(sb))
725	return -EBUSY;
726	}
727
728	if (sb->s_op->remount_fs) {
729	retval = sb->s_op->remount_fs(sb, &flags, data);
730	if (retval) {
731	if (!force)
732	return retval;
733	/* If forced remount, go ahead despite any errors */
734	WARN(1, "forced remount of a %s fs returned %i\n",
735	sb->s_type->name, retval);
736	}
737	}
738	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) \| (flags & MS_RMT_MASK);
739
740	/*
741	* Some filesystems modify their metadata via some other path than the
742	* bdev buffer cache (eg. use a private mapping, or directories in
743	* pagecache, etc). Also file data modifications go via their own
744	* mappings. So If we try to mount readonly then copy the filesystem
745	* from bdev, we could get stale data, so invalidate it to give a best
746	* effort at coherency.
747	*/
748	if (remount_ro && sb->s_bdev)
749	invalidate_bdev(sb->s_bdev);
750	return 0;
751	}
752
753	static void do_emergency_remount(struct work_struct *work)
754	{
755	struct super_block sb, p = NULL;
756
757	spin_lock(&sb_lock);
758	list_for_each_entry(sb, &super_blocks, s_list) {
759	if (list_empty(&sb->s_instances))
760	continue;
761	sb->s_count++;
762	spin_unlock(&sb_lock);
763	down_write(&sb->s_umount);
764	if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
765	/*
766	* What lock protects sb->s_flags??
767	*/
768	do_remount_sb(sb, MS_RDONLY, NULL, 1);
769	}
770	up_write(&sb->s_umount);
771	spin_lock(&sb_lock);
772	if (p)
773	__put_super(p);
774	p = sb;
775	}
776	if (p)
777	__put_super(p);
778	spin_unlock(&sb_lock);
779	kfree(work);
780	printk("Emergency Remount complete\n");
781	}
782
783	void emergency_remount(void)
784	{
785	struct work_struct *work;
786
787	work = kmalloc(sizeof(*work), GFP_ATOMIC);
788	if (work) {
789	INIT_WORK(work, do_emergency_remount);
790	schedule_work(work);
791	}
792	}
793
794	/*
795	* Unnamed block devices are dummy devices used by virtual
796	* filesystems which don't use real block-devices. -- jrs
797	*/
798
799	static DEFINE_IDA(unnamed_dev_ida);
800	static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
801	static int unnamed_dev_start = 0; /* don't bother trying below it */
802
803	int get_anon_bdev(dev_t *p)
804	{
805	int dev;
806	int error;
807
808	retry:
809	if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
810	return -ENOMEM;
811	spin_lock(&unnamed_dev_lock);
812	error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
813	if (!error)
814	unnamed_dev_start = dev + 1;
815	spin_unlock(&unnamed_dev_lock);
816	if (error == -EAGAIN)
817	/* We raced and lost with another CPU. */
818	goto retry;
819	else if (error)
820	return -EAGAIN;
821
822	if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
823	spin_lock(&unnamed_dev_lock);
824	ida_remove(&unnamed_dev_ida, dev);
825	if (unnamed_dev_start > dev)
826	unnamed_dev_start = dev;
827	spin_unlock(&unnamed_dev_lock);
828	return -EMFILE;
829	}
830	*p = MKDEV(0, dev & MINORMASK);
831	return 0;
832	}
833	EXPORT_SYMBOL(get_anon_bdev);
834
835	void free_anon_bdev(dev_t dev)
836	{
837	int slot = MINOR(dev);
838	spin_lock(&unnamed_dev_lock);
839	ida_remove(&unnamed_dev_ida, slot);
840	if (slot < unnamed_dev_start)
841	unnamed_dev_start = slot;
842	spin_unlock(&unnamed_dev_lock);
843	}
844	EXPORT_SYMBOL(free_anon_bdev);
845
846	int set_anon_super(struct super_block s, void data)
847	{
848	int error = get_anon_bdev(&s->s_dev);
849	if (!error)
850	s->s_bdi = &noop_backing_dev_info;
851	return error;
852	}
853
854	EXPORT_SYMBOL(set_anon_super);
855
856	void kill_anon_super(struct super_block *sb)
857	{
858	dev_t dev = sb->s_dev;
859	generic_shutdown_super(sb);
860	free_anon_bdev(dev);
861	}
862
863	EXPORT_SYMBOL(kill_anon_super);
864
865	void kill_litter_super(struct super_block *sb)
866	{
867	if (sb->s_root)
868	d_genocide(sb->s_root);
869	kill_anon_super(sb);
870	}
871
872	EXPORT_SYMBOL(kill_litter_super);
873
874	static int ns_test_super(struct super_block sb, void data)
875	{
876	return sb->s_fs_info == data;
877	}
878
879	static int ns_set_super(struct super_block sb, void data)
880	{
881	sb->s_fs_info = data;
882	return set_anon_super(sb, NULL);
883	}
884
885	struct dentry mount_ns(struct file_system_type fs_type, int flags,
886	void data, int (fill_super)(struct super_block , void , int))
887	{
888	struct super_block *sb;
889
890	sb = sget(fs_type, ns_test_super, ns_set_super, data);
891	if (IS_ERR(sb))
892	return ERR_CAST(sb);
893
894	if (!sb->s_root) {
895	int err;
896	sb->s_flags = flags;
897	err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
898	if (err) {
899	deactivate_locked_super(sb);
900	return ERR_PTR(err);
901	}
902
903	sb->s_flags \|= MS_ACTIVE;
904	}
905
906	return dget(sb->s_root);
907	}
908
909	EXPORT_SYMBOL(mount_ns);
910
911	#ifdef CONFIG_BLOCK
912	static int set_bdev_super(struct super_block s, void data)
913	{
914	s->s_bdev = data;
915	s->s_dev = s->s_bdev->bd_dev;
916
917	/*
918	* We set the bdi here to the queue backing, file systems can
919	* overwrite this in ->fill_super()
920	*/
921	s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;
922	return 0;
923	}
924
925	static int test_bdev_super(struct super_block s, void data)
926	{
927	return (void *)s->s_bdev == data;
928	}
929
930	struct dentry mount_bdev(struct file_system_type fs_type,
931	int flags, const char dev_name, void data,
932	int (fill_super)(struct super_block , void *, int))
933	{
934	struct block_device *bdev;
935	struct super_block *s;
936	fmode_t mode = FMODE_READ \| FMODE_EXCL;
937	int error = 0;
938
939	if (!(flags & MS_RDONLY))
940	mode \|= FMODE_WRITE;
941
942	bdev = blkdev_get_by_path(dev_name, mode, fs_type);
943	if (IS_ERR(bdev))
944	return ERR_CAST(bdev);
945
946	/*
947	* once the super is inserted into the list by sget, s_umount
948	* will protect the lockfs code from trying to start a snapshot
949	* while we are mounting
950	*/
951	mutex_lock(&bdev->bd_fsfreeze_mutex);
952	if (bdev->bd_fsfreeze_count > 0) {
953	mutex_unlock(&bdev->bd_fsfreeze_mutex);
954	error = -EBUSY;
955	goto error_bdev;
956	}
957	s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
958	mutex_unlock(&bdev->bd_fsfreeze_mutex);
959	if (IS_ERR(s))
960	goto error_s;
961
962	if (s->s_root) {
963	if ((flags ^ s->s_flags) & MS_RDONLY) {
964	deactivate_locked_super(s);
965	error = -EBUSY;
966	goto error_bdev;
967	}
968
969	/*
970	* s_umount nests inside bd_mutex during
971	* __invalidate_device(). blkdev_put() acquires
972	* bd_mutex and can't be called under s_umount. Drop
973	* s_umount temporarily. This is safe as we're
974	* holding an active reference.
975	*/
976	up_write(&s->s_umount);
977	blkdev_put(bdev, mode);
978	down_write(&s->s_umount);
979	} else {
980	char b[BDEVNAME_SIZE];
981
982	s->s_flags = flags \| MS_NOSEC;
983	s->s_mode = mode;
984	strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
985	sb_set_blocksize(s, block_size(bdev));
986	error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
987	if (error) {
988	deactivate_locked_super(s);
989	goto error;
990	}
991
992	s->s_flags \|= MS_ACTIVE;
993	bdev->bd_super = s;
994	}
995
996	return dget(s->s_root);
997
998	error_s:
999	error = PTR_ERR(s);
1000	error_bdev:
1001	blkdev_put(bdev, mode);
1002	error:
1003	return ERR_PTR(error);
1004	}
1005	EXPORT_SYMBOL(mount_bdev);
1006
1007	void kill_block_super(struct super_block *sb)
1008	{
1009	struct block_device *bdev = sb->s_bdev;
1010	fmode_t mode = sb->s_mode;
1011
1012	bdev->bd_super = NULL;
1013	generic_shutdown_super(sb);
1014	sync_blockdev(bdev);
1015	WARN_ON_ONCE(!(mode & FMODE_EXCL));
1016	blkdev_put(bdev, mode \| FMODE_EXCL);
1017	}
1018
1019	EXPORT_SYMBOL(kill_block_super);
1020	#endif
1021
1022	struct dentry mount_nodev(struct file_system_type fs_type,
1023	int flags, void *data,
1024	int (fill_super)(struct super_block , void *, int))
1025	{
1026	int error;
1027	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
1028
1029	if (IS_ERR(s))
1030	return ERR_CAST(s);
1031
1032	s->s_flags = flags;
1033
1034	error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1035	if (error) {
1036	deactivate_locked_super(s);
1037	return ERR_PTR(error);
1038	}
1039	s->s_flags \|= MS_ACTIVE;
1040	return dget(s->s_root);
1041	}
1042	EXPORT_SYMBOL(mount_nodev);
1043
1044	static int compare_single(struct super_block s, void p)
1045	{
1046	return 1;
1047	}
1048
1049	struct dentry mount_single(struct file_system_type fs_type,
1050	int flags, void *data,
1051	int (fill_super)(struct super_block , void *, int))
1052	{
1053	struct super_block *s;
1054	int error;
1055
1056	s = sget(fs_type, compare_single, set_anon_super, NULL);
1057	if (IS_ERR(s))
1058	return ERR_CAST(s);
1059	if (!s->s_root) {
1060	s->s_flags = flags;
1061	error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
1062	if (error) {
1063	deactivate_locked_super(s);
1064	return ERR_PTR(error);
1065	}
1066	s->s_flags \|= MS_ACTIVE;
1067	} else {
1068	do_remount_sb(s, flags, data, 0);
1069	}
1070	return dget(s->s_root);
1071	}
1072	EXPORT_SYMBOL(mount_single);
1073
1074	struct dentry *
1075	mount_fs(struct file_system_type type, int flags, const char name, void *data)
1076	{
1077	struct dentry *root;
1078	struct super_block *sb;
1079	char *secdata = NULL;
1080	int error = -ENOMEM;
1081
1082	if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
1083	secdata = alloc_secdata();
1084	if (!secdata)
1085	goto out;
1086
1087	error = security_sb_copy_data(data, secdata);
1088	if (error)
1089	goto out_free_secdata;
1090	}
1091
1092	root = type->mount(type, flags, name, data);
1093	if (IS_ERR(root)) {
1094	error = PTR_ERR(root);
1095	goto out_free_secdata;
1096	}
1097	sb = root->d_sb;
1098	BUG_ON(!sb);
1099	WARN_ON(!sb->s_bdi);
1100	WARN_ON(sb->s_bdi == &default_backing_dev_info);
1101	sb->s_flags \|= MS_BORN;
1102
1103	error = security_sb_kern_mount(sb, flags, secdata);
1104	if (error)
1105	goto out_sb;
1106
1107	/*
1108	* filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
1109	* but s_maxbytes was an unsigned long long for many releases. Throw
1110	* this warning for a little while to try and catch filesystems that
1111	* violate this rule.
1112	*/
1113	WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
1114	"negative value (%lld)\n", type->name, sb->s_maxbytes);
1115
1116	up_write(&sb->s_umount);
1117	free_secdata(secdata);
1118	return root;
1119	out_sb:
1120	dput(root);
1121	deactivate_locked_super(sb);
1122	out_free_secdata:
1123	free_secdata(secdata);
1124	out:
1125	return ERR_PTR(error);
1126	}
1127
1128	/**
1129	* freeze_super - lock the filesystem and force it into a consistent state
1130	* @sb: the super to lock
1131	*
1132	* Syncs the super to make sure the filesystem is consistent and calls the fs's
1133	* freeze_fs. Subsequent calls to this without first thawing the fs will return
1134	* -EBUSY.
1135	*/
1136	int freeze_super(struct super_block *sb)
1137	{
1138	int ret;
1139
1140	atomic_inc(&sb->s_active);
1141	down_write(&sb->s_umount);
1142	if (sb->s_frozen) {
1143	deactivate_locked_super(sb);
1144	return -EBUSY;
1145	}
1146
1147	if (sb->s_flags & MS_RDONLY) {
1148	sb->s_frozen = SB_FREEZE_TRANS;
1149	smp_wmb();
1150	up_write(&sb->s_umount);
1151	return 0;
1152	}
1153
1154	sb->s_frozen = SB_FREEZE_WRITE;
1155	smp_wmb();
1156
1157	sync_filesystem(sb);
1158
1159	sb->s_frozen = SB_FREEZE_TRANS;
1160	smp_wmb();
1161
1162	sync_blockdev(sb->s_bdev);
1163	if (sb->s_op->freeze_fs) {
1164	ret = sb->s_op->freeze_fs(sb);
1165	if (ret) {
1166	printk(KERN_ERR
1167	"VFS:Filesystem freeze failed\n");
1168	sb->s_frozen = SB_UNFROZEN;
1169	deactivate_locked_super(sb);
1170	return ret;
1171	}
1172	}
1173	up_write(&sb->s_umount);
1174	return 0;
1175	}
1176	EXPORT_SYMBOL(freeze_super);
1177
1178	/**
1179	* thaw_super -- unlock filesystem
1180	* @sb: the super to thaw
1181	*
1182	* Unlocks the filesystem and marks it writeable again after freeze_super().
1183	*/
1184	int thaw_super(struct super_block *sb)
1185	{
1186	int error;
1187
1188	down_write(&sb->s_umount);
1189	if (sb->s_frozen == SB_UNFROZEN) {
1190	up_write(&sb->s_umount);
1191	return -EINVAL;
1192	}
1193
1194	if (sb->s_flags & MS_RDONLY)
1195	goto out;
1196
1197	if (sb->s_op->unfreeze_fs) {
1198	error = sb->s_op->unfreeze_fs(sb);
1199	if (error) {
1200	printk(KERN_ERR
1201	"VFS:Filesystem thaw failed\n");
1202	sb->s_frozen = SB_FREEZE_TRANS;
1203	up_write(&sb->s_umount);
1204	return error;
1205	}
1206	}
1207
1208	out:
1209	sb->s_frozen = SB_UNFROZEN;
1210	smp_wmb();
1211	wake_up(&sb->s_wait_unfrozen);
1212	deactivate_locked_super(sb);
1213
1214	return 0;
1215	}
1216	EXPORT_SYMBOL(thaw_super);
1217

Download this file

Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9

Kernel

Kernel Git Source Tree

Root/fs/super.c

interactive