xref: /openbmc/linux/fs/super.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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  *    Torbj�rn 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/config.h>
24 #include <linux/module.h>
25 #include <linux/slab.h>
26 #include <linux/init.h>
27 #include <linux/smp_lock.h>
28 #include <linux/acct.h>
29 #include <linux/blkdev.h>
30 #include <linux/quotaops.h>
31 #include <linux/namei.h>
32 #include <linux/buffer_head.h>		/* for fsync_super() */
33 #include <linux/mount.h>
34 #include <linux/security.h>
35 #include <linux/syscalls.h>
36 #include <linux/vfs.h>
37 #include <linux/writeback.h>		/* for the emergency remount stuff */
38 #include <linux/idr.h>
39 #include <linux/kobject.h>
40 #include <asm/uaccess.h>
41 
42 
43 void get_filesystem(struct file_system_type *fs);
44 void put_filesystem(struct file_system_type *fs);
45 struct file_system_type *get_fs_type(const char *name);
46 
47 LIST_HEAD(super_blocks);
48 DEFINE_SPINLOCK(sb_lock);
49 
50 /**
51  *	alloc_super	-	create new superblock
52  *
53  *	Allocates and initializes a new &struct super_block.  alloc_super()
54  *	returns a pointer new superblock or %NULL if allocation had failed.
55  */
56 static struct super_block *alloc_super(void)
57 {
58 	struct super_block *s = kmalloc(sizeof(struct super_block),  GFP_USER);
59 	static struct super_operations default_op;
60 
61 	if (s) {
62 		memset(s, 0, sizeof(struct super_block));
63 		if (security_sb_alloc(s)) {
64 			kfree(s);
65 			s = NULL;
66 			goto out;
67 		}
68 		INIT_LIST_HEAD(&s->s_dirty);
69 		INIT_LIST_HEAD(&s->s_io);
70 		INIT_LIST_HEAD(&s->s_files);
71 		INIT_LIST_HEAD(&s->s_instances);
72 		INIT_HLIST_HEAD(&s->s_anon);
73 		INIT_LIST_HEAD(&s->s_inodes);
74 		init_rwsem(&s->s_umount);
75 		sema_init(&s->s_lock, 1);
76 		down_write(&s->s_umount);
77 		s->s_count = S_BIAS;
78 		atomic_set(&s->s_active, 1);
79 		sema_init(&s->s_vfs_rename_sem,1);
80 		sema_init(&s->s_dquot.dqio_sem, 1);
81 		sema_init(&s->s_dquot.dqonoff_sem, 1);
82 		init_rwsem(&s->s_dquot.dqptr_sem);
83 		init_waitqueue_head(&s->s_wait_unfrozen);
84 		s->s_maxbytes = MAX_NON_LFS;
85 		s->dq_op = sb_dquot_ops;
86 		s->s_qcop = sb_quotactl_ops;
87 		s->s_op = &default_op;
88 		s->s_time_gran = 1000000000;
89 	}
90 out:
91 	return s;
92 }
93 
94 /**
95  *	destroy_super	-	frees a superblock
96  *	@s: superblock to free
97  *
98  *	Frees a superblock.
99  */
100 static inline void destroy_super(struct super_block *s)
101 {
102 	security_sb_free(s);
103 	kfree(s);
104 }
105 
106 /* Superblock refcounting  */
107 
108 /*
109  * Drop a superblock's refcount.  Returns non-zero if the superblock was
110  * destroyed.  The caller must hold sb_lock.
111  */
112 int __put_super(struct super_block *sb)
113 {
114 	int ret = 0;
115 
116 	if (!--sb->s_count) {
117 		destroy_super(sb);
118 		ret = 1;
119 	}
120 	return ret;
121 }
122 
123 /*
124  * Drop a superblock's refcount.
125  * Returns non-zero if the superblock is about to be destroyed and
126  * at least is already removed from super_blocks list, so if we are
127  * making a loop through super blocks then we need to restart.
128  * The caller must hold sb_lock.
129  */
130 int __put_super_and_need_restart(struct super_block *sb)
131 {
132 	/* check for race with generic_shutdown_super() */
133 	if (list_empty(&sb->s_list)) {
134 		/* super block is removed, need to restart... */
135 		__put_super(sb);
136 		return 1;
137 	}
138 	/* can't be the last, since s_list is still in use */
139 	sb->s_count--;
140 	BUG_ON(sb->s_count == 0);
141 	return 0;
142 }
143 
144 /**
145  *	put_super	-	drop a temporary reference to superblock
146  *	@sb: superblock in question
147  *
148  *	Drops a temporary reference, frees superblock if there's no
149  *	references left.
150  */
151 static void put_super(struct super_block *sb)
152 {
153 	spin_lock(&sb_lock);
154 	__put_super(sb);
155 	spin_unlock(&sb_lock);
156 }
157 
158 
159 /**
160  *	deactivate_super	-	drop an active reference to superblock
161  *	@s: superblock to deactivate
162  *
163  *	Drops an active reference to superblock, acquiring a temprory one if
164  *	there is no active references left.  In that case we lock superblock,
165  *	tell fs driver to shut it down and drop the temporary reference we
166  *	had just acquired.
167  */
168 void deactivate_super(struct super_block *s)
169 {
170 	struct file_system_type *fs = s->s_type;
171 	if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
172 		s->s_count -= S_BIAS-1;
173 		spin_unlock(&sb_lock);
174 		down_write(&s->s_umount);
175 		fs->kill_sb(s);
176 		put_filesystem(fs);
177 		put_super(s);
178 	}
179 }
180 
181 EXPORT_SYMBOL(deactivate_super);
182 
183 /**
184  *	grab_super - acquire an active reference
185  *	@s: reference we are trying to make active
186  *
187  *	Tries to acquire an active reference.  grab_super() is used when we
188  * 	had just found a superblock in super_blocks or fs_type->fs_supers
189  *	and want to turn it into a full-blown active reference.  grab_super()
190  *	is called with sb_lock held and drops it.  Returns 1 in case of
191  *	success, 0 if we had failed (superblock contents was already dead or
192  *	dying when grab_super() had been called).
193  */
194 static int grab_super(struct super_block *s)
195 {
196 	s->s_count++;
197 	spin_unlock(&sb_lock);
198 	down_write(&s->s_umount);
199 	if (s->s_root) {
200 		spin_lock(&sb_lock);
201 		if (s->s_count > S_BIAS) {
202 			atomic_inc(&s->s_active);
203 			s->s_count--;
204 			spin_unlock(&sb_lock);
205 			return 1;
206 		}
207 		spin_unlock(&sb_lock);
208 	}
209 	up_write(&s->s_umount);
210 	put_super(s);
211 	yield();
212 	return 0;
213 }
214 
215 /**
216  *	generic_shutdown_super	-	common helper for ->kill_sb()
217  *	@sb: superblock to kill
218  *
219  *	generic_shutdown_super() does all fs-independent work on superblock
220  *	shutdown.  Typical ->kill_sb() should pick all fs-specific objects
221  *	that need destruction out of superblock, call generic_shutdown_super()
222  *	and release aforementioned objects.  Note: dentries and inodes _are_
223  *	taken care of and do not need specific handling.
224  */
225 void generic_shutdown_super(struct super_block *sb)
226 {
227 	struct dentry *root = sb->s_root;
228 	struct super_operations *sop = sb->s_op;
229 
230 	if (root) {
231 		sb->s_root = NULL;
232 		shrink_dcache_parent(root);
233 		shrink_dcache_anon(&sb->s_anon);
234 		dput(root);
235 		fsync_super(sb);
236 		lock_super(sb);
237 		sb->s_flags &= ~MS_ACTIVE;
238 		/* bad name - it should be evict_inodes() */
239 		invalidate_inodes(sb);
240 		lock_kernel();
241 
242 		if (sop->write_super && sb->s_dirt)
243 			sop->write_super(sb);
244 		if (sop->put_super)
245 			sop->put_super(sb);
246 
247 		/* Forget any remaining inodes */
248 		if (invalidate_inodes(sb)) {
249 			printk("VFS: Busy inodes after unmount. "
250 			   "Self-destruct in 5 seconds.  Have a nice day...\n");
251 		}
252 
253 		unlock_kernel();
254 		unlock_super(sb);
255 	}
256 	spin_lock(&sb_lock);
257 	/* should be initialized for __put_super_and_need_restart() */
258 	list_del_init(&sb->s_list);
259 	list_del(&sb->s_instances);
260 	spin_unlock(&sb_lock);
261 	up_write(&sb->s_umount);
262 }
263 
264 EXPORT_SYMBOL(generic_shutdown_super);
265 
266 /**
267  *	sget	-	find or create a superblock
268  *	@type:	filesystem type superblock should belong to
269  *	@test:	comparison callback
270  *	@set:	setup callback
271  *	@data:	argument to each of them
272  */
273 struct super_block *sget(struct file_system_type *type,
274 			int (*test)(struct super_block *,void *),
275 			int (*set)(struct super_block *,void *),
276 			void *data)
277 {
278 	struct super_block *s = NULL;
279 	struct list_head *p;
280 	int err;
281 
282 retry:
283 	spin_lock(&sb_lock);
284 	if (test) list_for_each(p, &type->fs_supers) {
285 		struct super_block *old;
286 		old = list_entry(p, struct super_block, s_instances);
287 		if (!test(old, data))
288 			continue;
289 		if (!grab_super(old))
290 			goto retry;
291 		if (s)
292 			destroy_super(s);
293 		return old;
294 	}
295 	if (!s) {
296 		spin_unlock(&sb_lock);
297 		s = alloc_super();
298 		if (!s)
299 			return ERR_PTR(-ENOMEM);
300 		goto retry;
301 	}
302 
303 	err = set(s, data);
304 	if (err) {
305 		spin_unlock(&sb_lock);
306 		destroy_super(s);
307 		return ERR_PTR(err);
308 	}
309 	s->s_type = type;
310 	strlcpy(s->s_id, type->name, sizeof(s->s_id));
311 	list_add_tail(&s->s_list, &super_blocks);
312 	list_add(&s->s_instances, &type->fs_supers);
313 	spin_unlock(&sb_lock);
314 	get_filesystem(type);
315 	return s;
316 }
317 
318 EXPORT_SYMBOL(sget);
319 
320 void drop_super(struct super_block *sb)
321 {
322 	up_read(&sb->s_umount);
323 	put_super(sb);
324 }
325 
326 EXPORT_SYMBOL(drop_super);
327 
328 static inline void write_super(struct super_block *sb)
329 {
330 	lock_super(sb);
331 	if (sb->s_root && sb->s_dirt)
332 		if (sb->s_op->write_super)
333 			sb->s_op->write_super(sb);
334 	unlock_super(sb);
335 }
336 
337 /*
338  * Note: check the dirty flag before waiting, so we don't
339  * hold up the sync while mounting a device. (The newly
340  * mounted device won't need syncing.)
341  */
342 void sync_supers(void)
343 {
344 	struct super_block *sb;
345 
346 	spin_lock(&sb_lock);
347 restart:
348 	list_for_each_entry(sb, &super_blocks, s_list) {
349 		if (sb->s_dirt) {
350 			sb->s_count++;
351 			spin_unlock(&sb_lock);
352 			down_read(&sb->s_umount);
353 			write_super(sb);
354 			up_read(&sb->s_umount);
355 			spin_lock(&sb_lock);
356 			if (__put_super_and_need_restart(sb))
357 				goto restart;
358 		}
359 	}
360 	spin_unlock(&sb_lock);
361 }
362 
363 /*
364  * Call the ->sync_fs super_op against all filesytems which are r/w and
365  * which implement it.
366  *
367  * This operation is careful to avoid the livelock which could easily happen
368  * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
369  * is used only here.  We set it against all filesystems and then clear it as
370  * we sync them.  So redirtied filesystems are skipped.
371  *
372  * But if process A is currently running sync_filesytems and then process B
373  * calls sync_filesystems as well, process B will set all the s_need_sync_fs
374  * flags again, which will cause process A to resync everything.  Fix that with
375  * a local mutex.
376  *
377  * (Fabian) Avoid sync_fs with clean fs & wait mode 0
378  */
379 void sync_filesystems(int wait)
380 {
381 	struct super_block *sb;
382 	static DECLARE_MUTEX(mutex);
383 
384 	down(&mutex);		/* Could be down_interruptible */
385 	spin_lock(&sb_lock);
386 	list_for_each_entry(sb, &super_blocks, s_list) {
387 		if (!sb->s_op->sync_fs)
388 			continue;
389 		if (sb->s_flags & MS_RDONLY)
390 			continue;
391 		sb->s_need_sync_fs = 1;
392 	}
393 
394 restart:
395 	list_for_each_entry(sb, &super_blocks, s_list) {
396 		if (!sb->s_need_sync_fs)
397 			continue;
398 		sb->s_need_sync_fs = 0;
399 		if (sb->s_flags & MS_RDONLY)
400 			continue;	/* hm.  Was remounted r/o meanwhile */
401 		sb->s_count++;
402 		spin_unlock(&sb_lock);
403 		down_read(&sb->s_umount);
404 		if (sb->s_root && (wait || sb->s_dirt))
405 			sb->s_op->sync_fs(sb, wait);
406 		up_read(&sb->s_umount);
407 		/* restart only when sb is no longer on the list */
408 		spin_lock(&sb_lock);
409 		if (__put_super_and_need_restart(sb))
410 			goto restart;
411 	}
412 	spin_unlock(&sb_lock);
413 	up(&mutex);
414 }
415 
416 /**
417  *	get_super - get the superblock of a device
418  *	@bdev: device to get the superblock for
419  *
420  *	Scans the superblock list and finds the superblock of the file system
421  *	mounted on the device given. %NULL is returned if no match is found.
422  */
423 
424 struct super_block * get_super(struct block_device *bdev)
425 {
426 	struct super_block *sb;
427 
428 	if (!bdev)
429 		return NULL;
430 
431 	spin_lock(&sb_lock);
432 rescan:
433 	list_for_each_entry(sb, &super_blocks, s_list) {
434 		if (sb->s_bdev == bdev) {
435 			sb->s_count++;
436 			spin_unlock(&sb_lock);
437 			down_read(&sb->s_umount);
438 			if (sb->s_root)
439 				return sb;
440 			up_read(&sb->s_umount);
441 			/* restart only when sb is no longer on the list */
442 			spin_lock(&sb_lock);
443 			if (__put_super_and_need_restart(sb))
444 				goto rescan;
445 		}
446 	}
447 	spin_unlock(&sb_lock);
448 	return NULL;
449 }
450 
451 EXPORT_SYMBOL(get_super);
452 
453 struct super_block * user_get_super(dev_t dev)
454 {
455 	struct super_block *sb;
456 
457 	spin_lock(&sb_lock);
458 rescan:
459 	list_for_each_entry(sb, &super_blocks, s_list) {
460 		if (sb->s_dev ==  dev) {
461 			sb->s_count++;
462 			spin_unlock(&sb_lock);
463 			down_read(&sb->s_umount);
464 			if (sb->s_root)
465 				return sb;
466 			up_read(&sb->s_umount);
467 			/* restart only when sb is no longer on the list */
468 			spin_lock(&sb_lock);
469 			if (__put_super_and_need_restart(sb))
470 				goto rescan;
471 		}
472 	}
473 	spin_unlock(&sb_lock);
474 	return NULL;
475 }
476 
477 EXPORT_SYMBOL(user_get_super);
478 
479 asmlinkage long sys_ustat(unsigned dev, struct ustat __user * ubuf)
480 {
481         struct super_block *s;
482         struct ustat tmp;
483         struct kstatfs sbuf;
484 	int err = -EINVAL;
485 
486         s = user_get_super(new_decode_dev(dev));
487         if (s == NULL)
488                 goto out;
489 	err = vfs_statfs(s, &sbuf);
490 	drop_super(s);
491 	if (err)
492 		goto out;
493 
494         memset(&tmp,0,sizeof(struct ustat));
495         tmp.f_tfree = sbuf.f_bfree;
496         tmp.f_tinode = sbuf.f_ffree;
497 
498         err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
499 out:
500 	return err;
501 }
502 
503 /**
504  *	mark_files_ro
505  *	@sb: superblock in question
506  *
507  *	All files are marked read/only.  We don't care about pending
508  *	delete files so this should be used in 'force' mode only
509  */
510 
511 static void mark_files_ro(struct super_block *sb)
512 {
513 	struct file *f;
514 
515 	file_list_lock();
516 	list_for_each_entry(f, &sb->s_files, f_u.fu_list) {
517 		if (S_ISREG(f->f_dentry->d_inode->i_mode) && file_count(f))
518 			f->f_mode &= ~FMODE_WRITE;
519 	}
520 	file_list_unlock();
521 }
522 
523 /**
524  *	do_remount_sb - asks filesystem to change mount options.
525  *	@sb:	superblock in question
526  *	@flags:	numeric part of options
527  *	@data:	the rest of options
528  *      @force: whether or not to force the change
529  *
530  *	Alters the mount options of a mounted file system.
531  */
532 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
533 {
534 	int retval;
535 
536 	if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
537 		return -EACCES;
538 	if (flags & MS_RDONLY)
539 		acct_auto_close(sb);
540 	shrink_dcache_sb(sb);
541 	fsync_super(sb);
542 
543 	/* If we are remounting RDONLY and current sb is read/write,
544 	   make sure there are no rw files opened */
545 	if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
546 		if (force)
547 			mark_files_ro(sb);
548 		else if (!fs_may_remount_ro(sb))
549 			return -EBUSY;
550 	}
551 
552 	if (sb->s_op->remount_fs) {
553 		lock_super(sb);
554 		retval = sb->s_op->remount_fs(sb, &flags, data);
555 		unlock_super(sb);
556 		if (retval)
557 			return retval;
558 	}
559 	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
560 	return 0;
561 }
562 
563 static void do_emergency_remount(unsigned long foo)
564 {
565 	struct super_block *sb;
566 
567 	spin_lock(&sb_lock);
568 	list_for_each_entry(sb, &super_blocks, s_list) {
569 		sb->s_count++;
570 		spin_unlock(&sb_lock);
571 		down_read(&sb->s_umount);
572 		if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
573 			/*
574 			 * ->remount_fs needs lock_kernel().
575 			 *
576 			 * What lock protects sb->s_flags??
577 			 */
578 			lock_kernel();
579 			do_remount_sb(sb, MS_RDONLY, NULL, 1);
580 			unlock_kernel();
581 		}
582 		drop_super(sb);
583 		spin_lock(&sb_lock);
584 	}
585 	spin_unlock(&sb_lock);
586 	printk("Emergency Remount complete\n");
587 }
588 
589 void emergency_remount(void)
590 {
591 	pdflush_operation(do_emergency_remount, 0);
592 }
593 
594 /*
595  * Unnamed block devices are dummy devices used by virtual
596  * filesystems which don't use real block-devices.  -- jrs
597  */
598 
599 static struct idr unnamed_dev_idr;
600 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
601 
602 int set_anon_super(struct super_block *s, void *data)
603 {
604 	int dev;
605 	int error;
606 
607  retry:
608 	if (idr_pre_get(&unnamed_dev_idr, GFP_ATOMIC) == 0)
609 		return -ENOMEM;
610 	spin_lock(&unnamed_dev_lock);
611 	error = idr_get_new(&unnamed_dev_idr, NULL, &dev);
612 	spin_unlock(&unnamed_dev_lock);
613 	if (error == -EAGAIN)
614 		/* We raced and lost with another CPU. */
615 		goto retry;
616 	else if (error)
617 		return -EAGAIN;
618 
619 	if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
620 		spin_lock(&unnamed_dev_lock);
621 		idr_remove(&unnamed_dev_idr, dev);
622 		spin_unlock(&unnamed_dev_lock);
623 		return -EMFILE;
624 	}
625 	s->s_dev = MKDEV(0, dev & MINORMASK);
626 	return 0;
627 }
628 
629 EXPORT_SYMBOL(set_anon_super);
630 
631 void kill_anon_super(struct super_block *sb)
632 {
633 	int slot = MINOR(sb->s_dev);
634 
635 	generic_shutdown_super(sb);
636 	spin_lock(&unnamed_dev_lock);
637 	idr_remove(&unnamed_dev_idr, slot);
638 	spin_unlock(&unnamed_dev_lock);
639 }
640 
641 EXPORT_SYMBOL(kill_anon_super);
642 
643 void __init unnamed_dev_init(void)
644 {
645 	idr_init(&unnamed_dev_idr);
646 }
647 
648 void kill_litter_super(struct super_block *sb)
649 {
650 	if (sb->s_root)
651 		d_genocide(sb->s_root);
652 	kill_anon_super(sb);
653 }
654 
655 EXPORT_SYMBOL(kill_litter_super);
656 
657 static int set_bdev_super(struct super_block *s, void *data)
658 {
659 	s->s_bdev = data;
660 	s->s_dev = s->s_bdev->bd_dev;
661 	return 0;
662 }
663 
664 static int test_bdev_super(struct super_block *s, void *data)
665 {
666 	return (void *)s->s_bdev == data;
667 }
668 
669 static void bdev_uevent(struct block_device *bdev, enum kobject_action action)
670 {
671 	if (bdev->bd_disk) {
672 		if (bdev->bd_part)
673 			kobject_uevent(&bdev->bd_part->kobj, action, NULL);
674 		else
675 			kobject_uevent(&bdev->bd_disk->kobj, action, NULL);
676 	}
677 }
678 
679 struct super_block *get_sb_bdev(struct file_system_type *fs_type,
680 	int flags, const char *dev_name, void *data,
681 	int (*fill_super)(struct super_block *, void *, int))
682 {
683 	struct block_device *bdev;
684 	struct super_block *s;
685 	int error = 0;
686 
687 	bdev = open_bdev_excl(dev_name, flags, fs_type);
688 	if (IS_ERR(bdev))
689 		return (struct super_block *)bdev;
690 
691 	/*
692 	 * once the super is inserted into the list by sget, s_umount
693 	 * will protect the lockfs code from trying to start a snapshot
694 	 * while we are mounting
695 	 */
696 	down(&bdev->bd_mount_sem);
697 	s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
698 	up(&bdev->bd_mount_sem);
699 	if (IS_ERR(s))
700 		goto out;
701 
702 	if (s->s_root) {
703 		if ((flags ^ s->s_flags) & MS_RDONLY) {
704 			up_write(&s->s_umount);
705 			deactivate_super(s);
706 			s = ERR_PTR(-EBUSY);
707 		}
708 		goto out;
709 	} else {
710 		char b[BDEVNAME_SIZE];
711 
712 		s->s_flags = flags;
713 		strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
714 		s->s_old_blocksize = block_size(bdev);
715 		sb_set_blocksize(s, s->s_old_blocksize);
716 		error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
717 		if (error) {
718 			up_write(&s->s_umount);
719 			deactivate_super(s);
720 			s = ERR_PTR(error);
721 		} else {
722 			s->s_flags |= MS_ACTIVE;
723 			bdev_uevent(bdev, KOBJ_MOUNT);
724 		}
725 	}
726 
727 	return s;
728 
729 out:
730 	close_bdev_excl(bdev);
731 	return s;
732 }
733 
734 EXPORT_SYMBOL(get_sb_bdev);
735 
736 void kill_block_super(struct super_block *sb)
737 {
738 	struct block_device *bdev = sb->s_bdev;
739 
740 	bdev_uevent(bdev, KOBJ_UMOUNT);
741 	generic_shutdown_super(sb);
742 	sync_blockdev(bdev);
743 	close_bdev_excl(bdev);
744 }
745 
746 EXPORT_SYMBOL(kill_block_super);
747 
748 struct super_block *get_sb_nodev(struct file_system_type *fs_type,
749 	int flags, void *data,
750 	int (*fill_super)(struct super_block *, void *, int))
751 {
752 	int error;
753 	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
754 
755 	if (IS_ERR(s))
756 		return s;
757 
758 	s->s_flags = flags;
759 
760 	error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
761 	if (error) {
762 		up_write(&s->s_umount);
763 		deactivate_super(s);
764 		return ERR_PTR(error);
765 	}
766 	s->s_flags |= MS_ACTIVE;
767 	return s;
768 }
769 
770 EXPORT_SYMBOL(get_sb_nodev);
771 
772 static int compare_single(struct super_block *s, void *p)
773 {
774 	return 1;
775 }
776 
777 struct super_block *get_sb_single(struct file_system_type *fs_type,
778 	int flags, void *data,
779 	int (*fill_super)(struct super_block *, void *, int))
780 {
781 	struct super_block *s;
782 	int error;
783 
784 	s = sget(fs_type, compare_single, set_anon_super, NULL);
785 	if (IS_ERR(s))
786 		return s;
787 	if (!s->s_root) {
788 		s->s_flags = flags;
789 		error = fill_super(s, data, flags & MS_VERBOSE ? 1 : 0);
790 		if (error) {
791 			up_write(&s->s_umount);
792 			deactivate_super(s);
793 			return ERR_PTR(error);
794 		}
795 		s->s_flags |= MS_ACTIVE;
796 	}
797 	do_remount_sb(s, flags, data, 0);
798 	return s;
799 }
800 
801 EXPORT_SYMBOL(get_sb_single);
802 
803 struct vfsmount *
804 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
805 {
806 	struct file_system_type *type = get_fs_type(fstype);
807 	struct super_block *sb = ERR_PTR(-ENOMEM);
808 	struct vfsmount *mnt;
809 	int error;
810 	char *secdata = NULL;
811 
812 	if (!type)
813 		return ERR_PTR(-ENODEV);
814 
815 	mnt = alloc_vfsmnt(name);
816 	if (!mnt)
817 		goto out;
818 
819 	if (data) {
820 		secdata = alloc_secdata();
821 		if (!secdata) {
822 			sb = ERR_PTR(-ENOMEM);
823 			goto out_mnt;
824 		}
825 
826 		error = security_sb_copy_data(type, data, secdata);
827 		if (error) {
828 			sb = ERR_PTR(error);
829 			goto out_free_secdata;
830 		}
831 	}
832 
833 	sb = type->get_sb(type, flags, name, data);
834 	if (IS_ERR(sb))
835 		goto out_free_secdata;
836  	error = security_sb_kern_mount(sb, secdata);
837  	if (error)
838  		goto out_sb;
839 	mnt->mnt_sb = sb;
840 	mnt->mnt_root = dget(sb->s_root);
841 	mnt->mnt_mountpoint = sb->s_root;
842 	mnt->mnt_parent = mnt;
843 	up_write(&sb->s_umount);
844 	free_secdata(secdata);
845 	put_filesystem(type);
846 	return mnt;
847 out_sb:
848 	up_write(&sb->s_umount);
849 	deactivate_super(sb);
850 	sb = ERR_PTR(error);
851 out_free_secdata:
852 	free_secdata(secdata);
853 out_mnt:
854 	free_vfsmnt(mnt);
855 out:
856 	put_filesystem(type);
857 	return (struct vfsmount *)sb;
858 }
859 
860 EXPORT_SYMBOL_GPL(do_kern_mount);
861 
862 struct vfsmount *kern_mount(struct file_system_type *type)
863 {
864 	return do_kern_mount(type->name, 0, type->name, NULL);
865 }
866 
867 EXPORT_SYMBOL(kern_mount);
868