xref: /openbmc/linux/fs/super.c (revision fd589a8f)
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/init.h>
26 #include <linux/smp_lock.h>
27 #include <linux/acct.h>
28 #include <linux/blkdev.h>
29 #include <linux/quotaops.h>
30 #include <linux/namei.h>
31 #include <linux/mount.h>
32 #include <linux/security.h>
33 #include <linux/syscalls.h>
34 #include <linux/vfs.h>
35 #include <linux/writeback.h>		/* for the emergency remount stuff */
36 #include <linux/idr.h>
37 #include <linux/kobject.h>
38 #include <linux/mutex.h>
39 #include <linux/file.h>
40 #include <asm/uaccess.h>
41 #include "internal.h"
42 
43 
44 LIST_HEAD(super_blocks);
45 DEFINE_SPINLOCK(sb_lock);
46 
47 /**
48  *	alloc_super	-	create new superblock
49  *	@type:	filesystem type superblock should belong to
50  *
51  *	Allocates and initializes a new &struct super_block.  alloc_super()
52  *	returns a pointer new superblock or %NULL if allocation had failed.
53  */
54 static struct super_block *alloc_super(struct file_system_type *type)
55 {
56 	struct super_block *s = kzalloc(sizeof(struct super_block),  GFP_USER);
57 	static struct super_operations default_op;
58 
59 	if (s) {
60 		if (security_sb_alloc(s)) {
61 			kfree(s);
62 			s = NULL;
63 			goto out;
64 		}
65 		INIT_LIST_HEAD(&s->s_files);
66 		INIT_LIST_HEAD(&s->s_instances);
67 		INIT_HLIST_HEAD(&s->s_anon);
68 		INIT_LIST_HEAD(&s->s_inodes);
69 		INIT_LIST_HEAD(&s->s_dentry_lru);
70 		init_rwsem(&s->s_umount);
71 		mutex_init(&s->s_lock);
72 		lockdep_set_class(&s->s_umount, &type->s_umount_key);
73 		/*
74 		 * The locking rules for s_lock are up to the
75 		 * filesystem. For example ext3fs has different
76 		 * lock ordering than usbfs:
77 		 */
78 		lockdep_set_class(&s->s_lock, &type->s_lock_key);
79 		/*
80 		 * sget() can have s_umount recursion.
81 		 *
82 		 * When it cannot find a suitable sb, it allocates a new
83 		 * one (this one), and tries again to find a suitable old
84 		 * one.
85 		 *
86 		 * In case that succeeds, it will acquire the s_umount
87 		 * lock of the old one. Since these are clearly distrinct
88 		 * locks, and this object isn't exposed yet, there's no
89 		 * risk of deadlocks.
90 		 *
91 		 * Annotate this by putting this lock in a different
92 		 * subclass.
93 		 */
94 		down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
95 		s->s_count = S_BIAS;
96 		atomic_set(&s->s_active, 1);
97 		mutex_init(&s->s_vfs_rename_mutex);
98 		mutex_init(&s->s_dquot.dqio_mutex);
99 		mutex_init(&s->s_dquot.dqonoff_mutex);
100 		init_rwsem(&s->s_dquot.dqptr_sem);
101 		init_waitqueue_head(&s->s_wait_unfrozen);
102 		s->s_maxbytes = MAX_NON_LFS;
103 		s->dq_op = sb_dquot_ops;
104 		s->s_qcop = sb_quotactl_ops;
105 		s->s_op = &default_op;
106 		s->s_time_gran = 1000000000;
107 	}
108 out:
109 	return s;
110 }
111 
112 /**
113  *	destroy_super	-	frees a superblock
114  *	@s: superblock to free
115  *
116  *	Frees a superblock.
117  */
118 static inline void destroy_super(struct super_block *s)
119 {
120 	security_sb_free(s);
121 	kfree(s->s_subtype);
122 	kfree(s->s_options);
123 	kfree(s);
124 }
125 
126 /* Superblock refcounting  */
127 
128 /*
129  * Drop a superblock's refcount.  Returns non-zero if the superblock was
130  * destroyed.  The caller must hold sb_lock.
131  */
132 static int __put_super(struct super_block *sb)
133 {
134 	int ret = 0;
135 
136 	if (!--sb->s_count) {
137 		destroy_super(sb);
138 		ret = 1;
139 	}
140 	return ret;
141 }
142 
143 /*
144  * Drop a superblock's refcount.
145  * Returns non-zero if the superblock is about to be destroyed and
146  * at least is already removed from super_blocks list, so if we are
147  * making a loop through super blocks then we need to restart.
148  * The caller must hold sb_lock.
149  */
150 int __put_super_and_need_restart(struct super_block *sb)
151 {
152 	/* check for race with generic_shutdown_super() */
153 	if (list_empty(&sb->s_list)) {
154 		/* super block is removed, need to restart... */
155 		__put_super(sb);
156 		return 1;
157 	}
158 	/* can't be the last, since s_list is still in use */
159 	sb->s_count--;
160 	BUG_ON(sb->s_count == 0);
161 	return 0;
162 }
163 
164 /**
165  *	put_super	-	drop a temporary reference to superblock
166  *	@sb: superblock in question
167  *
168  *	Drops a temporary reference, frees superblock if there's no
169  *	references left.
170  */
171 void put_super(struct super_block *sb)
172 {
173 	spin_lock(&sb_lock);
174 	__put_super(sb);
175 	spin_unlock(&sb_lock);
176 }
177 
178 
179 /**
180  *	deactivate_super	-	drop an active reference to superblock
181  *	@s: superblock to deactivate
182  *
183  *	Drops an active reference to superblock, acquiring a temprory one if
184  *	there is no active references left.  In that case we lock superblock,
185  *	tell fs driver to shut it down and drop the temporary reference we
186  *	had just acquired.
187  */
188 void deactivate_super(struct super_block *s)
189 {
190 	struct file_system_type *fs = s->s_type;
191 	if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
192 		s->s_count -= S_BIAS-1;
193 		spin_unlock(&sb_lock);
194 		vfs_dq_off(s, 0);
195 		down_write(&s->s_umount);
196 		fs->kill_sb(s);
197 		put_filesystem(fs);
198 		put_super(s);
199 	}
200 }
201 
202 EXPORT_SYMBOL(deactivate_super);
203 
204 /**
205  *	deactivate_locked_super	-	drop an active reference to superblock
206  *	@s: superblock to deactivate
207  *
208  *	Equivalent of up_write(&s->s_umount); deactivate_super(s);, except that
209  *	it does not unlock it until it's all over.  As the result, it's safe to
210  *	use to dispose of new superblock on ->get_sb() failure exits - nobody
211  *	will see the sucker until it's all over.  Equivalent using up_write +
212  *	deactivate_super is safe for that purpose only if superblock is either
213  *	safe to use or has NULL ->s_root when we unlock.
214  */
215 void deactivate_locked_super(struct super_block *s)
216 {
217 	struct file_system_type *fs = s->s_type;
218 	if (atomic_dec_and_lock(&s->s_active, &sb_lock)) {
219 		s->s_count -= S_BIAS-1;
220 		spin_unlock(&sb_lock);
221 		vfs_dq_off(s, 0);
222 		fs->kill_sb(s);
223 		put_filesystem(fs);
224 		put_super(s);
225 	} else {
226 		up_write(&s->s_umount);
227 	}
228 }
229 
230 EXPORT_SYMBOL(deactivate_locked_super);
231 
232 /**
233  *	grab_super - acquire an active reference
234  *	@s: reference we are trying to make active
235  *
236  *	Tries to acquire an active reference.  grab_super() is used when we
237  * 	had just found a superblock in super_blocks or fs_type->fs_supers
238  *	and want to turn it into a full-blown active reference.  grab_super()
239  *	is called with sb_lock held and drops it.  Returns 1 in case of
240  *	success, 0 if we had failed (superblock contents was already dead or
241  *	dying when grab_super() had been called).
242  */
243 static int grab_super(struct super_block *s) __releases(sb_lock)
244 {
245 	s->s_count++;
246 	spin_unlock(&sb_lock);
247 	down_write(&s->s_umount);
248 	if (s->s_root) {
249 		spin_lock(&sb_lock);
250 		if (s->s_count > S_BIAS) {
251 			atomic_inc(&s->s_active);
252 			s->s_count--;
253 			spin_unlock(&sb_lock);
254 			return 1;
255 		}
256 		spin_unlock(&sb_lock);
257 	}
258 	up_write(&s->s_umount);
259 	put_super(s);
260 	yield();
261 	return 0;
262 }
263 
264 /*
265  * Superblock locking.  We really ought to get rid of these two.
266  */
267 void lock_super(struct super_block * sb)
268 {
269 	get_fs_excl();
270 	mutex_lock(&sb->s_lock);
271 }
272 
273 void unlock_super(struct super_block * sb)
274 {
275 	put_fs_excl();
276 	mutex_unlock(&sb->s_lock);
277 }
278 
279 EXPORT_SYMBOL(lock_super);
280 EXPORT_SYMBOL(unlock_super);
281 
282 /**
283  *	generic_shutdown_super	-	common helper for ->kill_sb()
284  *	@sb: superblock to kill
285  *
286  *	generic_shutdown_super() does all fs-independent work on superblock
287  *	shutdown.  Typical ->kill_sb() should pick all fs-specific objects
288  *	that need destruction out of superblock, call generic_shutdown_super()
289  *	and release aforementioned objects.  Note: dentries and inodes _are_
290  *	taken care of and do not need specific handling.
291  *
292  *	Upon calling this function, the filesystem may no longer alter or
293  *	rearrange the set of dentries belonging to this super_block, nor may it
294  *	change the attachments of dentries to inodes.
295  */
296 void generic_shutdown_super(struct super_block *sb)
297 {
298 	const struct super_operations *sop = sb->s_op;
299 
300 
301 	if (sb->s_root) {
302 		shrink_dcache_for_umount(sb);
303 		sync_filesystem(sb);
304 		get_fs_excl();
305 		sb->s_flags &= ~MS_ACTIVE;
306 
307 		/* bad name - it should be evict_inodes() */
308 		invalidate_inodes(sb);
309 
310 		if (sop->put_super)
311 			sop->put_super(sb);
312 
313 		/* Forget any remaining inodes */
314 		if (invalidate_inodes(sb)) {
315 			printk("VFS: Busy inodes after unmount of %s. "
316 			   "Self-destruct in 5 seconds.  Have a nice day...\n",
317 			   sb->s_id);
318 		}
319 		put_fs_excl();
320 	}
321 	spin_lock(&sb_lock);
322 	/* should be initialized for __put_super_and_need_restart() */
323 	list_del_init(&sb->s_list);
324 	list_del(&sb->s_instances);
325 	spin_unlock(&sb_lock);
326 	up_write(&sb->s_umount);
327 }
328 
329 EXPORT_SYMBOL(generic_shutdown_super);
330 
331 /**
332  *	sget	-	find or create a superblock
333  *	@type:	filesystem type superblock should belong to
334  *	@test:	comparison callback
335  *	@set:	setup callback
336  *	@data:	argument to each of them
337  */
338 struct super_block *sget(struct file_system_type *type,
339 			int (*test)(struct super_block *,void *),
340 			int (*set)(struct super_block *,void *),
341 			void *data)
342 {
343 	struct super_block *s = NULL;
344 	struct super_block *old;
345 	int err;
346 
347 retry:
348 	spin_lock(&sb_lock);
349 	if (test) {
350 		list_for_each_entry(old, &type->fs_supers, s_instances) {
351 			if (!test(old, data))
352 				continue;
353 			if (!grab_super(old))
354 				goto retry;
355 			if (s) {
356 				up_write(&s->s_umount);
357 				destroy_super(s);
358 			}
359 			return old;
360 		}
361 	}
362 	if (!s) {
363 		spin_unlock(&sb_lock);
364 		s = alloc_super(type);
365 		if (!s)
366 			return ERR_PTR(-ENOMEM);
367 		goto retry;
368 	}
369 
370 	err = set(s, data);
371 	if (err) {
372 		spin_unlock(&sb_lock);
373 		up_write(&s->s_umount);
374 		destroy_super(s);
375 		return ERR_PTR(err);
376 	}
377 	s->s_type = type;
378 	strlcpy(s->s_id, type->name, sizeof(s->s_id));
379 	list_add_tail(&s->s_list, &super_blocks);
380 	list_add(&s->s_instances, &type->fs_supers);
381 	spin_unlock(&sb_lock);
382 	get_filesystem(type);
383 	return s;
384 }
385 
386 EXPORT_SYMBOL(sget);
387 
388 void drop_super(struct super_block *sb)
389 {
390 	up_read(&sb->s_umount);
391 	put_super(sb);
392 }
393 
394 EXPORT_SYMBOL(drop_super);
395 
396 /**
397  * sync_supers - helper for periodic superblock writeback
398  *
399  * Call the write_super method if present on all dirty superblocks in
400  * the system.  This is for the periodic writeback used by most older
401  * filesystems.  For data integrity superblock writeback use
402  * sync_filesystems() instead.
403  *
404  * Note: check the dirty flag before waiting, so we don't
405  * hold up the sync while mounting a device. (The newly
406  * mounted device won't need syncing.)
407  */
408 void sync_supers(void)
409 {
410 	struct super_block *sb;
411 
412 	spin_lock(&sb_lock);
413 restart:
414 	list_for_each_entry(sb, &super_blocks, s_list) {
415 		if (sb->s_op->write_super && sb->s_dirt) {
416 			sb->s_count++;
417 			spin_unlock(&sb_lock);
418 
419 			down_read(&sb->s_umount);
420 			if (sb->s_root && sb->s_dirt)
421 				sb->s_op->write_super(sb);
422 			up_read(&sb->s_umount);
423 
424 			spin_lock(&sb_lock);
425 			if (__put_super_and_need_restart(sb))
426 				goto restart;
427 		}
428 	}
429 	spin_unlock(&sb_lock);
430 }
431 
432 /**
433  *	get_super - get the superblock of a device
434  *	@bdev: device to get the superblock for
435  *
436  *	Scans the superblock list and finds the superblock of the file system
437  *	mounted on the device given. %NULL is returned if no match is found.
438  */
439 
440 struct super_block * get_super(struct block_device *bdev)
441 {
442 	struct super_block *sb;
443 
444 	if (!bdev)
445 		return NULL;
446 
447 	spin_lock(&sb_lock);
448 rescan:
449 	list_for_each_entry(sb, &super_blocks, s_list) {
450 		if (sb->s_bdev == bdev) {
451 			sb->s_count++;
452 			spin_unlock(&sb_lock);
453 			down_read(&sb->s_umount);
454 			if (sb->s_root)
455 				return sb;
456 			up_read(&sb->s_umount);
457 			/* restart only when sb is no longer on the list */
458 			spin_lock(&sb_lock);
459 			if (__put_super_and_need_restart(sb))
460 				goto rescan;
461 		}
462 	}
463 	spin_unlock(&sb_lock);
464 	return NULL;
465 }
466 
467 EXPORT_SYMBOL(get_super);
468 
469 struct super_block * user_get_super(dev_t dev)
470 {
471 	struct super_block *sb;
472 
473 	spin_lock(&sb_lock);
474 rescan:
475 	list_for_each_entry(sb, &super_blocks, s_list) {
476 		if (sb->s_dev ==  dev) {
477 			sb->s_count++;
478 			spin_unlock(&sb_lock);
479 			down_read(&sb->s_umount);
480 			if (sb->s_root)
481 				return sb;
482 			up_read(&sb->s_umount);
483 			/* restart only when sb is no longer on the list */
484 			spin_lock(&sb_lock);
485 			if (__put_super_and_need_restart(sb))
486 				goto rescan;
487 		}
488 	}
489 	spin_unlock(&sb_lock);
490 	return NULL;
491 }
492 
493 SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf)
494 {
495         struct super_block *s;
496         struct ustat tmp;
497         struct kstatfs sbuf;
498 	int err = -EINVAL;
499 
500         s = user_get_super(new_decode_dev(dev));
501         if (s == NULL)
502                 goto out;
503 	err = vfs_statfs(s->s_root, &sbuf);
504 	drop_super(s);
505 	if (err)
506 		goto out;
507 
508         memset(&tmp,0,sizeof(struct ustat));
509         tmp.f_tfree = sbuf.f_bfree;
510         tmp.f_tinode = sbuf.f_ffree;
511 
512         err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0;
513 out:
514 	return err;
515 }
516 
517 /**
518  *	do_remount_sb - asks filesystem to change mount options.
519  *	@sb:	superblock in question
520  *	@flags:	numeric part of options
521  *	@data:	the rest of options
522  *      @force: whether or not to force the change
523  *
524  *	Alters the mount options of a mounted file system.
525  */
526 int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
527 {
528 	int retval;
529 	int remount_rw;
530 
531 #ifdef CONFIG_BLOCK
532 	if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
533 		return -EACCES;
534 #endif
535 	if (flags & MS_RDONLY)
536 		acct_auto_close(sb);
537 	shrink_dcache_sb(sb);
538 	sync_filesystem(sb);
539 
540 	/* If we are remounting RDONLY and current sb is read/write,
541 	   make sure there are no rw files opened */
542 	if ((flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY)) {
543 		if (force)
544 			mark_files_ro(sb);
545 		else if (!fs_may_remount_ro(sb))
546 			return -EBUSY;
547 		retval = vfs_dq_off(sb, 1);
548 		if (retval < 0 && retval != -ENOSYS)
549 			return -EBUSY;
550 	}
551 	remount_rw = !(flags & MS_RDONLY) && (sb->s_flags & MS_RDONLY);
552 
553 	if (sb->s_op->remount_fs) {
554 		retval = sb->s_op->remount_fs(sb, &flags, data);
555 		if (retval)
556 			return retval;
557 	}
558 	sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
559 	if (remount_rw)
560 		vfs_dq_quota_on_remount(sb);
561 	return 0;
562 }
563 
564 static void do_emergency_remount(struct work_struct *work)
565 {
566 	struct super_block *sb;
567 
568 	spin_lock(&sb_lock);
569 	list_for_each_entry(sb, &super_blocks, s_list) {
570 		sb->s_count++;
571 		spin_unlock(&sb_lock);
572 		down_write(&sb->s_umount);
573 		if (sb->s_root && sb->s_bdev && !(sb->s_flags & MS_RDONLY)) {
574 			/*
575 			 * ->remount_fs needs lock_kernel().
576 			 *
577 			 * What lock protects sb->s_flags??
578 			 */
579 			do_remount_sb(sb, MS_RDONLY, NULL, 1);
580 		}
581 		up_write(&sb->s_umount);
582 		put_super(sb);
583 		spin_lock(&sb_lock);
584 	}
585 	spin_unlock(&sb_lock);
586 	kfree(work);
587 	printk("Emergency Remount complete\n");
588 }
589 
590 void emergency_remount(void)
591 {
592 	struct work_struct *work;
593 
594 	work = kmalloc(sizeof(*work), GFP_ATOMIC);
595 	if (work) {
596 		INIT_WORK(work, do_emergency_remount);
597 		schedule_work(work);
598 	}
599 }
600 
601 /*
602  * Unnamed block devices are dummy devices used by virtual
603  * filesystems which don't use real block-devices.  -- jrs
604  */
605 
606 static DEFINE_IDA(unnamed_dev_ida);
607 static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
608 static int unnamed_dev_start = 0; /* don't bother trying below it */
609 
610 int set_anon_super(struct super_block *s, void *data)
611 {
612 	int dev;
613 	int error;
614 
615  retry:
616 	if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
617 		return -ENOMEM;
618 	spin_lock(&unnamed_dev_lock);
619 	error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
620 	if (!error)
621 		unnamed_dev_start = dev + 1;
622 	spin_unlock(&unnamed_dev_lock);
623 	if (error == -EAGAIN)
624 		/* We raced and lost with another CPU. */
625 		goto retry;
626 	else if (error)
627 		return -EAGAIN;
628 
629 	if ((dev & MAX_ID_MASK) == (1 << MINORBITS)) {
630 		spin_lock(&unnamed_dev_lock);
631 		ida_remove(&unnamed_dev_ida, dev);
632 		if (unnamed_dev_start > dev)
633 			unnamed_dev_start = dev;
634 		spin_unlock(&unnamed_dev_lock);
635 		return -EMFILE;
636 	}
637 	s->s_dev = MKDEV(0, dev & MINORMASK);
638 	return 0;
639 }
640 
641 EXPORT_SYMBOL(set_anon_super);
642 
643 void kill_anon_super(struct super_block *sb)
644 {
645 	int slot = MINOR(sb->s_dev);
646 
647 	generic_shutdown_super(sb);
648 	spin_lock(&unnamed_dev_lock);
649 	ida_remove(&unnamed_dev_ida, slot);
650 	if (slot < unnamed_dev_start)
651 		unnamed_dev_start = slot;
652 	spin_unlock(&unnamed_dev_lock);
653 }
654 
655 EXPORT_SYMBOL(kill_anon_super);
656 
657 void kill_litter_super(struct super_block *sb)
658 {
659 	if (sb->s_root)
660 		d_genocide(sb->s_root);
661 	kill_anon_super(sb);
662 }
663 
664 EXPORT_SYMBOL(kill_litter_super);
665 
666 static int ns_test_super(struct super_block *sb, void *data)
667 {
668 	return sb->s_fs_info == data;
669 }
670 
671 static int ns_set_super(struct super_block *sb, void *data)
672 {
673 	sb->s_fs_info = data;
674 	return set_anon_super(sb, NULL);
675 }
676 
677 int get_sb_ns(struct file_system_type *fs_type, int flags, void *data,
678 	int (*fill_super)(struct super_block *, void *, int),
679 	struct vfsmount *mnt)
680 {
681 	struct super_block *sb;
682 
683 	sb = sget(fs_type, ns_test_super, ns_set_super, data);
684 	if (IS_ERR(sb))
685 		return PTR_ERR(sb);
686 
687 	if (!sb->s_root) {
688 		int err;
689 		sb->s_flags = flags;
690 		err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
691 		if (err) {
692 			deactivate_locked_super(sb);
693 			return err;
694 		}
695 
696 		sb->s_flags |= MS_ACTIVE;
697 	}
698 
699 	simple_set_mnt(mnt, sb);
700 	return 0;
701 }
702 
703 EXPORT_SYMBOL(get_sb_ns);
704 
705 #ifdef CONFIG_BLOCK
706 static int set_bdev_super(struct super_block *s, void *data)
707 {
708 	s->s_bdev = data;
709 	s->s_dev = s->s_bdev->bd_dev;
710 
711 	/*
712 	 * We set the bdi here to the queue backing, file systems can
713 	 * overwrite this in ->fill_super()
714 	 */
715 	s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;
716 	return 0;
717 }
718 
719 static int test_bdev_super(struct super_block *s, void *data)
720 {
721 	return (void *)s->s_bdev == data;
722 }
723 
724 int get_sb_bdev(struct file_system_type *fs_type,
725 	int flags, const char *dev_name, void *data,
726 	int (*fill_super)(struct super_block *, void *, int),
727 	struct vfsmount *mnt)
728 {
729 	struct block_device *bdev;
730 	struct super_block *s;
731 	fmode_t mode = FMODE_READ;
732 	int error = 0;
733 
734 	if (!(flags & MS_RDONLY))
735 		mode |= FMODE_WRITE;
736 
737 	bdev = open_bdev_exclusive(dev_name, mode, fs_type);
738 	if (IS_ERR(bdev))
739 		return PTR_ERR(bdev);
740 
741 	/*
742 	 * once the super is inserted into the list by sget, s_umount
743 	 * will protect the lockfs code from trying to start a snapshot
744 	 * while we are mounting
745 	 */
746 	down(&bdev->bd_mount_sem);
747 	s = sget(fs_type, test_bdev_super, set_bdev_super, bdev);
748 	up(&bdev->bd_mount_sem);
749 	if (IS_ERR(s))
750 		goto error_s;
751 
752 	if (s->s_root) {
753 		if ((flags ^ s->s_flags) & MS_RDONLY) {
754 			deactivate_locked_super(s);
755 			error = -EBUSY;
756 			goto error_bdev;
757 		}
758 
759 		close_bdev_exclusive(bdev, mode);
760 	} else {
761 		char b[BDEVNAME_SIZE];
762 
763 		s->s_flags = flags;
764 		s->s_mode = mode;
765 		strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
766 		sb_set_blocksize(s, block_size(bdev));
767 		error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
768 		if (error) {
769 			deactivate_locked_super(s);
770 			goto error;
771 		}
772 
773 		s->s_flags |= MS_ACTIVE;
774 		bdev->bd_super = s;
775 	}
776 
777 	simple_set_mnt(mnt, s);
778 	return 0;
779 
780 error_s:
781 	error = PTR_ERR(s);
782 error_bdev:
783 	close_bdev_exclusive(bdev, mode);
784 error:
785 	return error;
786 }
787 
788 EXPORT_SYMBOL(get_sb_bdev);
789 
790 void kill_block_super(struct super_block *sb)
791 {
792 	struct block_device *bdev = sb->s_bdev;
793 	fmode_t mode = sb->s_mode;
794 
795 	bdev->bd_super = NULL;
796 	generic_shutdown_super(sb);
797 	sync_blockdev(bdev);
798 	close_bdev_exclusive(bdev, mode);
799 }
800 
801 EXPORT_SYMBOL(kill_block_super);
802 #endif
803 
804 int get_sb_nodev(struct file_system_type *fs_type,
805 	int flags, void *data,
806 	int (*fill_super)(struct super_block *, void *, int),
807 	struct vfsmount *mnt)
808 {
809 	int error;
810 	struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL);
811 
812 	if (IS_ERR(s))
813 		return PTR_ERR(s);
814 
815 	s->s_flags = flags;
816 
817 	error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
818 	if (error) {
819 		deactivate_locked_super(s);
820 		return error;
821 	}
822 	s->s_flags |= MS_ACTIVE;
823 	simple_set_mnt(mnt, s);
824 	return 0;
825 }
826 
827 EXPORT_SYMBOL(get_sb_nodev);
828 
829 static int compare_single(struct super_block *s, void *p)
830 {
831 	return 1;
832 }
833 
834 int get_sb_single(struct file_system_type *fs_type,
835 	int flags, void *data,
836 	int (*fill_super)(struct super_block *, void *, int),
837 	struct vfsmount *mnt)
838 {
839 	struct super_block *s;
840 	int error;
841 
842 	s = sget(fs_type, compare_single, set_anon_super, NULL);
843 	if (IS_ERR(s))
844 		return PTR_ERR(s);
845 	if (!s->s_root) {
846 		s->s_flags = flags;
847 		error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
848 		if (error) {
849 			deactivate_locked_super(s);
850 			return error;
851 		}
852 		s->s_flags |= MS_ACTIVE;
853 	}
854 	do_remount_sb(s, flags, data, 0);
855 	simple_set_mnt(mnt, s);
856 	return 0;
857 }
858 
859 EXPORT_SYMBOL(get_sb_single);
860 
861 struct vfsmount *
862 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
863 {
864 	struct vfsmount *mnt;
865 	char *secdata = NULL;
866 	int error;
867 
868 	if (!type)
869 		return ERR_PTR(-ENODEV);
870 
871 	error = -ENOMEM;
872 	mnt = alloc_vfsmnt(name);
873 	if (!mnt)
874 		goto out;
875 
876 	if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
877 		secdata = alloc_secdata();
878 		if (!secdata)
879 			goto out_mnt;
880 
881 		error = security_sb_copy_data(data, secdata);
882 		if (error)
883 			goto out_free_secdata;
884 	}
885 
886 	error = type->get_sb(type, flags, name, data, mnt);
887 	if (error < 0)
888 		goto out_free_secdata;
889 	BUG_ON(!mnt->mnt_sb);
890 
891  	error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
892  	if (error)
893  		goto out_sb;
894 
895 	mnt->mnt_mountpoint = mnt->mnt_root;
896 	mnt->mnt_parent = mnt;
897 	up_write(&mnt->mnt_sb->s_umount);
898 	free_secdata(secdata);
899 	return mnt;
900 out_sb:
901 	dput(mnt->mnt_root);
902 	deactivate_locked_super(mnt->mnt_sb);
903 out_free_secdata:
904 	free_secdata(secdata);
905 out_mnt:
906 	free_vfsmnt(mnt);
907 out:
908 	return ERR_PTR(error);
909 }
910 
911 EXPORT_SYMBOL_GPL(vfs_kern_mount);
912 
913 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
914 {
915 	int err;
916 	const char *subtype = strchr(fstype, '.');
917 	if (subtype) {
918 		subtype++;
919 		err = -EINVAL;
920 		if (!subtype[0])
921 			goto err;
922 	} else
923 		subtype = "";
924 
925 	mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
926 	err = -ENOMEM;
927 	if (!mnt->mnt_sb->s_subtype)
928 		goto err;
929 	return mnt;
930 
931  err:
932 	mntput(mnt);
933 	return ERR_PTR(err);
934 }
935 
936 struct vfsmount *
937 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
938 {
939 	struct file_system_type *type = get_fs_type(fstype);
940 	struct vfsmount *mnt;
941 	if (!type)
942 		return ERR_PTR(-ENODEV);
943 	mnt = vfs_kern_mount(type, flags, name, data);
944 	if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
945 	    !mnt->mnt_sb->s_subtype)
946 		mnt = fs_set_subtype(mnt, fstype);
947 	put_filesystem(type);
948 	return mnt;
949 }
950 EXPORT_SYMBOL_GPL(do_kern_mount);
951 
952 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
953 {
954 	return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
955 }
956 
957 EXPORT_SYMBOL_GPL(kern_mount_data);
958