xref: /openbmc/linux/fs/namespace.c (revision 565d76cb)
1 /*
2  *  linux/fs/namespace.c
3  *
4  * (C) Copyright Al Viro 2000, 2001
5  *	Released under GPL v2.
6  *
7  * Based on code from fs/super.c, copyright Linus Torvalds and others.
8  * Heavily rewritten.
9  */
10 
11 #include <linux/syscalls.h>
12 #include <linux/slab.h>
13 #include <linux/sched.h>
14 #include <linux/spinlock.h>
15 #include <linux/percpu.h>
16 #include <linux/init.h>
17 #include <linux/kernel.h>
18 #include <linux/acct.h>
19 #include <linux/capability.h>
20 #include <linux/cpumask.h>
21 #include <linux/module.h>
22 #include <linux/sysfs.h>
23 #include <linux/seq_file.h>
24 #include <linux/mnt_namespace.h>
25 #include <linux/namei.h>
26 #include <linux/nsproxy.h>
27 #include <linux/security.h>
28 #include <linux/mount.h>
29 #include <linux/ramfs.h>
30 #include <linux/log2.h>
31 #include <linux/idr.h>
32 #include <linux/fs_struct.h>
33 #include <linux/fsnotify.h>
34 #include <asm/uaccess.h>
35 #include <asm/unistd.h>
36 #include "pnode.h"
37 #include "internal.h"
38 
39 #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
40 #define HASH_SIZE (1UL << HASH_SHIFT)
41 
42 static int event;
43 static DEFINE_IDA(mnt_id_ida);
44 static DEFINE_IDA(mnt_group_ida);
45 static DEFINE_SPINLOCK(mnt_id_lock);
46 static int mnt_id_start = 0;
47 static int mnt_group_start = 1;
48 
49 static struct list_head *mount_hashtable __read_mostly;
50 static struct kmem_cache *mnt_cache __read_mostly;
51 static struct rw_semaphore namespace_sem;
52 
53 /* /sys/fs */
54 struct kobject *fs_kobj;
55 EXPORT_SYMBOL_GPL(fs_kobj);
56 
57 /*
58  * vfsmount lock may be taken for read to prevent changes to the
59  * vfsmount hash, ie. during mountpoint lookups or walking back
60  * up the tree.
61  *
62  * It should be taken for write in all cases where the vfsmount
63  * tree or hash is modified or when a vfsmount structure is modified.
64  */
65 DEFINE_BRLOCK(vfsmount_lock);
66 
67 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
68 {
69 	unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
70 	tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
71 	tmp = tmp + (tmp >> HASH_SHIFT);
72 	return tmp & (HASH_SIZE - 1);
73 }
74 
75 #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
76 
77 /*
78  * allocation is serialized by namespace_sem, but we need the spinlock to
79  * serialize with freeing.
80  */
81 static int mnt_alloc_id(struct vfsmount *mnt)
82 {
83 	int res;
84 
85 retry:
86 	ida_pre_get(&mnt_id_ida, GFP_KERNEL);
87 	spin_lock(&mnt_id_lock);
88 	res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
89 	if (!res)
90 		mnt_id_start = mnt->mnt_id + 1;
91 	spin_unlock(&mnt_id_lock);
92 	if (res == -EAGAIN)
93 		goto retry;
94 
95 	return res;
96 }
97 
98 static void mnt_free_id(struct vfsmount *mnt)
99 {
100 	int id = mnt->mnt_id;
101 	spin_lock(&mnt_id_lock);
102 	ida_remove(&mnt_id_ida, id);
103 	if (mnt_id_start > id)
104 		mnt_id_start = id;
105 	spin_unlock(&mnt_id_lock);
106 }
107 
108 /*
109  * Allocate a new peer group ID
110  *
111  * mnt_group_ida is protected by namespace_sem
112  */
113 static int mnt_alloc_group_id(struct vfsmount *mnt)
114 {
115 	int res;
116 
117 	if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
118 		return -ENOMEM;
119 
120 	res = ida_get_new_above(&mnt_group_ida,
121 				mnt_group_start,
122 				&mnt->mnt_group_id);
123 	if (!res)
124 		mnt_group_start = mnt->mnt_group_id + 1;
125 
126 	return res;
127 }
128 
129 /*
130  * Release a peer group ID
131  */
132 void mnt_release_group_id(struct vfsmount *mnt)
133 {
134 	int id = mnt->mnt_group_id;
135 	ida_remove(&mnt_group_ida, id);
136 	if (mnt_group_start > id)
137 		mnt_group_start = id;
138 	mnt->mnt_group_id = 0;
139 }
140 
141 /*
142  * vfsmount lock must be held for read
143  */
144 static inline void mnt_add_count(struct vfsmount *mnt, int n)
145 {
146 #ifdef CONFIG_SMP
147 	this_cpu_add(mnt->mnt_pcp->mnt_count, n);
148 #else
149 	preempt_disable();
150 	mnt->mnt_count += n;
151 	preempt_enable();
152 #endif
153 }
154 
155 static inline void mnt_set_count(struct vfsmount *mnt, int n)
156 {
157 #ifdef CONFIG_SMP
158 	this_cpu_write(mnt->mnt_pcp->mnt_count, n);
159 #else
160 	mnt->mnt_count = n;
161 #endif
162 }
163 
164 /*
165  * vfsmount lock must be held for read
166  */
167 static inline void mnt_inc_count(struct vfsmount *mnt)
168 {
169 	mnt_add_count(mnt, 1);
170 }
171 
172 /*
173  * vfsmount lock must be held for read
174  */
175 static inline void mnt_dec_count(struct vfsmount *mnt)
176 {
177 	mnt_add_count(mnt, -1);
178 }
179 
180 /*
181  * vfsmount lock must be held for write
182  */
183 unsigned int mnt_get_count(struct vfsmount *mnt)
184 {
185 #ifdef CONFIG_SMP
186 	unsigned int count = 0;
187 	int cpu;
188 
189 	for_each_possible_cpu(cpu) {
190 		count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
191 	}
192 
193 	return count;
194 #else
195 	return mnt->mnt_count;
196 #endif
197 }
198 
199 static struct vfsmount *alloc_vfsmnt(const char *name)
200 {
201 	struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
202 	if (mnt) {
203 		int err;
204 
205 		err = mnt_alloc_id(mnt);
206 		if (err)
207 			goto out_free_cache;
208 
209 		if (name) {
210 			mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
211 			if (!mnt->mnt_devname)
212 				goto out_free_id;
213 		}
214 
215 #ifdef CONFIG_SMP
216 		mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
217 		if (!mnt->mnt_pcp)
218 			goto out_free_devname;
219 
220 		this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
221 #else
222 		mnt->mnt_count = 1;
223 		mnt->mnt_writers = 0;
224 #endif
225 
226 		INIT_LIST_HEAD(&mnt->mnt_hash);
227 		INIT_LIST_HEAD(&mnt->mnt_child);
228 		INIT_LIST_HEAD(&mnt->mnt_mounts);
229 		INIT_LIST_HEAD(&mnt->mnt_list);
230 		INIT_LIST_HEAD(&mnt->mnt_expire);
231 		INIT_LIST_HEAD(&mnt->mnt_share);
232 		INIT_LIST_HEAD(&mnt->mnt_slave_list);
233 		INIT_LIST_HEAD(&mnt->mnt_slave);
234 #ifdef CONFIG_FSNOTIFY
235 		INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
236 #endif
237 	}
238 	return mnt;
239 
240 #ifdef CONFIG_SMP
241 out_free_devname:
242 	kfree(mnt->mnt_devname);
243 #endif
244 out_free_id:
245 	mnt_free_id(mnt);
246 out_free_cache:
247 	kmem_cache_free(mnt_cache, mnt);
248 	return NULL;
249 }
250 
251 /*
252  * Most r/o checks on a fs are for operations that take
253  * discrete amounts of time, like a write() or unlink().
254  * We must keep track of when those operations start
255  * (for permission checks) and when they end, so that
256  * we can determine when writes are able to occur to
257  * a filesystem.
258  */
259 /*
260  * __mnt_is_readonly: check whether a mount is read-only
261  * @mnt: the mount to check for its write status
262  *
263  * This shouldn't be used directly ouside of the VFS.
264  * It does not guarantee that the filesystem will stay
265  * r/w, just that it is right *now*.  This can not and
266  * should not be used in place of IS_RDONLY(inode).
267  * mnt_want/drop_write() will _keep_ the filesystem
268  * r/w.
269  */
270 int __mnt_is_readonly(struct vfsmount *mnt)
271 {
272 	if (mnt->mnt_flags & MNT_READONLY)
273 		return 1;
274 	if (mnt->mnt_sb->s_flags & MS_RDONLY)
275 		return 1;
276 	return 0;
277 }
278 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
279 
280 static inline void mnt_inc_writers(struct vfsmount *mnt)
281 {
282 #ifdef CONFIG_SMP
283 	this_cpu_inc(mnt->mnt_pcp->mnt_writers);
284 #else
285 	mnt->mnt_writers++;
286 #endif
287 }
288 
289 static inline void mnt_dec_writers(struct vfsmount *mnt)
290 {
291 #ifdef CONFIG_SMP
292 	this_cpu_dec(mnt->mnt_pcp->mnt_writers);
293 #else
294 	mnt->mnt_writers--;
295 #endif
296 }
297 
298 static unsigned int mnt_get_writers(struct vfsmount *mnt)
299 {
300 #ifdef CONFIG_SMP
301 	unsigned int count = 0;
302 	int cpu;
303 
304 	for_each_possible_cpu(cpu) {
305 		count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
306 	}
307 
308 	return count;
309 #else
310 	return mnt->mnt_writers;
311 #endif
312 }
313 
314 /*
315  * Most r/o checks on a fs are for operations that take
316  * discrete amounts of time, like a write() or unlink().
317  * We must keep track of when those operations start
318  * (for permission checks) and when they end, so that
319  * we can determine when writes are able to occur to
320  * a filesystem.
321  */
322 /**
323  * mnt_want_write - get write access to a mount
324  * @mnt: the mount on which to take a write
325  *
326  * This tells the low-level filesystem that a write is
327  * about to be performed to it, and makes sure that
328  * writes are allowed before returning success.  When
329  * the write operation is finished, mnt_drop_write()
330  * must be called.  This is effectively a refcount.
331  */
332 int mnt_want_write(struct vfsmount *mnt)
333 {
334 	int ret = 0;
335 
336 	preempt_disable();
337 	mnt_inc_writers(mnt);
338 	/*
339 	 * The store to mnt_inc_writers must be visible before we pass
340 	 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
341 	 * incremented count after it has set MNT_WRITE_HOLD.
342 	 */
343 	smp_mb();
344 	while (mnt->mnt_flags & MNT_WRITE_HOLD)
345 		cpu_relax();
346 	/*
347 	 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
348 	 * be set to match its requirements. So we must not load that until
349 	 * MNT_WRITE_HOLD is cleared.
350 	 */
351 	smp_rmb();
352 	if (__mnt_is_readonly(mnt)) {
353 		mnt_dec_writers(mnt);
354 		ret = -EROFS;
355 		goto out;
356 	}
357 out:
358 	preempt_enable();
359 	return ret;
360 }
361 EXPORT_SYMBOL_GPL(mnt_want_write);
362 
363 /**
364  * mnt_clone_write - get write access to a mount
365  * @mnt: the mount on which to take a write
366  *
367  * This is effectively like mnt_want_write, except
368  * it must only be used to take an extra write reference
369  * on a mountpoint that we already know has a write reference
370  * on it. This allows some optimisation.
371  *
372  * After finished, mnt_drop_write must be called as usual to
373  * drop the reference.
374  */
375 int mnt_clone_write(struct vfsmount *mnt)
376 {
377 	/* superblock may be r/o */
378 	if (__mnt_is_readonly(mnt))
379 		return -EROFS;
380 	preempt_disable();
381 	mnt_inc_writers(mnt);
382 	preempt_enable();
383 	return 0;
384 }
385 EXPORT_SYMBOL_GPL(mnt_clone_write);
386 
387 /**
388  * mnt_want_write_file - get write access to a file's mount
389  * @file: the file who's mount on which to take a write
390  *
391  * This is like mnt_want_write, but it takes a file and can
392  * do some optimisations if the file is open for write already
393  */
394 int mnt_want_write_file(struct file *file)
395 {
396 	struct inode *inode = file->f_dentry->d_inode;
397 	if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
398 		return mnt_want_write(file->f_path.mnt);
399 	else
400 		return mnt_clone_write(file->f_path.mnt);
401 }
402 EXPORT_SYMBOL_GPL(mnt_want_write_file);
403 
404 /**
405  * mnt_drop_write - give up write access to a mount
406  * @mnt: the mount on which to give up write access
407  *
408  * Tells the low-level filesystem that we are done
409  * performing writes to it.  Must be matched with
410  * mnt_want_write() call above.
411  */
412 void mnt_drop_write(struct vfsmount *mnt)
413 {
414 	preempt_disable();
415 	mnt_dec_writers(mnt);
416 	preempt_enable();
417 }
418 EXPORT_SYMBOL_GPL(mnt_drop_write);
419 
420 static int mnt_make_readonly(struct vfsmount *mnt)
421 {
422 	int ret = 0;
423 
424 	br_write_lock(vfsmount_lock);
425 	mnt->mnt_flags |= MNT_WRITE_HOLD;
426 	/*
427 	 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
428 	 * should be visible before we do.
429 	 */
430 	smp_mb();
431 
432 	/*
433 	 * With writers on hold, if this value is zero, then there are
434 	 * definitely no active writers (although held writers may subsequently
435 	 * increment the count, they'll have to wait, and decrement it after
436 	 * seeing MNT_READONLY).
437 	 *
438 	 * It is OK to have counter incremented on one CPU and decremented on
439 	 * another: the sum will add up correctly. The danger would be when we
440 	 * sum up each counter, if we read a counter before it is incremented,
441 	 * but then read another CPU's count which it has been subsequently
442 	 * decremented from -- we would see more decrements than we should.
443 	 * MNT_WRITE_HOLD protects against this scenario, because
444 	 * mnt_want_write first increments count, then smp_mb, then spins on
445 	 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
446 	 * we're counting up here.
447 	 */
448 	if (mnt_get_writers(mnt) > 0)
449 		ret = -EBUSY;
450 	else
451 		mnt->mnt_flags |= MNT_READONLY;
452 	/*
453 	 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
454 	 * that become unheld will see MNT_READONLY.
455 	 */
456 	smp_wmb();
457 	mnt->mnt_flags &= ~MNT_WRITE_HOLD;
458 	br_write_unlock(vfsmount_lock);
459 	return ret;
460 }
461 
462 static void __mnt_unmake_readonly(struct vfsmount *mnt)
463 {
464 	br_write_lock(vfsmount_lock);
465 	mnt->mnt_flags &= ~MNT_READONLY;
466 	br_write_unlock(vfsmount_lock);
467 }
468 
469 static void free_vfsmnt(struct vfsmount *mnt)
470 {
471 	kfree(mnt->mnt_devname);
472 	mnt_free_id(mnt);
473 #ifdef CONFIG_SMP
474 	free_percpu(mnt->mnt_pcp);
475 #endif
476 	kmem_cache_free(mnt_cache, mnt);
477 }
478 
479 /*
480  * find the first or last mount at @dentry on vfsmount @mnt depending on
481  * @dir. If @dir is set return the first mount else return the last mount.
482  * vfsmount_lock must be held for read or write.
483  */
484 struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
485 			      int dir)
486 {
487 	struct list_head *head = mount_hashtable + hash(mnt, dentry);
488 	struct list_head *tmp = head;
489 	struct vfsmount *p, *found = NULL;
490 
491 	for (;;) {
492 		tmp = dir ? tmp->next : tmp->prev;
493 		p = NULL;
494 		if (tmp == head)
495 			break;
496 		p = list_entry(tmp, struct vfsmount, mnt_hash);
497 		if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
498 			found = p;
499 			break;
500 		}
501 	}
502 	return found;
503 }
504 
505 /*
506  * lookup_mnt increments the ref count before returning
507  * the vfsmount struct.
508  */
509 struct vfsmount *lookup_mnt(struct path *path)
510 {
511 	struct vfsmount *child_mnt;
512 
513 	br_read_lock(vfsmount_lock);
514 	if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1)))
515 		mntget(child_mnt);
516 	br_read_unlock(vfsmount_lock);
517 	return child_mnt;
518 }
519 
520 static inline int check_mnt(struct vfsmount *mnt)
521 {
522 	return mnt->mnt_ns == current->nsproxy->mnt_ns;
523 }
524 
525 /*
526  * vfsmount lock must be held for write
527  */
528 static void touch_mnt_namespace(struct mnt_namespace *ns)
529 {
530 	if (ns) {
531 		ns->event = ++event;
532 		wake_up_interruptible(&ns->poll);
533 	}
534 }
535 
536 /*
537  * vfsmount lock must be held for write
538  */
539 static void __touch_mnt_namespace(struct mnt_namespace *ns)
540 {
541 	if (ns && ns->event != event) {
542 		ns->event = event;
543 		wake_up_interruptible(&ns->poll);
544 	}
545 }
546 
547 /*
548  * Clear dentry's mounted state if it has no remaining mounts.
549  * vfsmount_lock must be held for write.
550  */
551 static void dentry_reset_mounted(struct vfsmount *mnt, struct dentry *dentry)
552 {
553 	unsigned u;
554 
555 	for (u = 0; u < HASH_SIZE; u++) {
556 		struct vfsmount *p;
557 
558 		list_for_each_entry(p, &mount_hashtable[u], mnt_hash) {
559 			if (p->mnt_mountpoint == dentry)
560 				return;
561 		}
562 	}
563 	spin_lock(&dentry->d_lock);
564 	dentry->d_flags &= ~DCACHE_MOUNTED;
565 	spin_unlock(&dentry->d_lock);
566 }
567 
568 /*
569  * vfsmount lock must be held for write
570  */
571 static void detach_mnt(struct vfsmount *mnt, struct path *old_path)
572 {
573 	old_path->dentry = mnt->mnt_mountpoint;
574 	old_path->mnt = mnt->mnt_parent;
575 	mnt->mnt_parent = mnt;
576 	mnt->mnt_mountpoint = mnt->mnt_root;
577 	list_del_init(&mnt->mnt_child);
578 	list_del_init(&mnt->mnt_hash);
579 	dentry_reset_mounted(old_path->mnt, old_path->dentry);
580 }
581 
582 /*
583  * vfsmount lock must be held for write
584  */
585 void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
586 			struct vfsmount *child_mnt)
587 {
588 	child_mnt->mnt_parent = mntget(mnt);
589 	child_mnt->mnt_mountpoint = dget(dentry);
590 	spin_lock(&dentry->d_lock);
591 	dentry->d_flags |= DCACHE_MOUNTED;
592 	spin_unlock(&dentry->d_lock);
593 }
594 
595 /*
596  * vfsmount lock must be held for write
597  */
598 static void attach_mnt(struct vfsmount *mnt, struct path *path)
599 {
600 	mnt_set_mountpoint(path->mnt, path->dentry, mnt);
601 	list_add_tail(&mnt->mnt_hash, mount_hashtable +
602 			hash(path->mnt, path->dentry));
603 	list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts);
604 }
605 
606 static inline void __mnt_make_longterm(struct vfsmount *mnt)
607 {
608 #ifdef CONFIG_SMP
609 	atomic_inc(&mnt->mnt_longterm);
610 #endif
611 }
612 
613 /* needs vfsmount lock for write */
614 static inline void __mnt_make_shortterm(struct vfsmount *mnt)
615 {
616 #ifdef CONFIG_SMP
617 	atomic_dec(&mnt->mnt_longterm);
618 #endif
619 }
620 
621 /*
622  * vfsmount lock must be held for write
623  */
624 static void commit_tree(struct vfsmount *mnt)
625 {
626 	struct vfsmount *parent = mnt->mnt_parent;
627 	struct vfsmount *m;
628 	LIST_HEAD(head);
629 	struct mnt_namespace *n = parent->mnt_ns;
630 
631 	BUG_ON(parent == mnt);
632 
633 	list_add_tail(&head, &mnt->mnt_list);
634 	list_for_each_entry(m, &head, mnt_list) {
635 		m->mnt_ns = n;
636 		__mnt_make_longterm(m);
637 	}
638 
639 	list_splice(&head, n->list.prev);
640 
641 	list_add_tail(&mnt->mnt_hash, mount_hashtable +
642 				hash(parent, mnt->mnt_mountpoint));
643 	list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
644 	touch_mnt_namespace(n);
645 }
646 
647 static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
648 {
649 	struct list_head *next = p->mnt_mounts.next;
650 	if (next == &p->mnt_mounts) {
651 		while (1) {
652 			if (p == root)
653 				return NULL;
654 			next = p->mnt_child.next;
655 			if (next != &p->mnt_parent->mnt_mounts)
656 				break;
657 			p = p->mnt_parent;
658 		}
659 	}
660 	return list_entry(next, struct vfsmount, mnt_child);
661 }
662 
663 static struct vfsmount *skip_mnt_tree(struct vfsmount *p)
664 {
665 	struct list_head *prev = p->mnt_mounts.prev;
666 	while (prev != &p->mnt_mounts) {
667 		p = list_entry(prev, struct vfsmount, mnt_child);
668 		prev = p->mnt_mounts.prev;
669 	}
670 	return p;
671 }
672 
673 struct vfsmount *
674 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
675 {
676 	struct vfsmount *mnt;
677 	struct dentry *root;
678 
679 	if (!type)
680 		return ERR_PTR(-ENODEV);
681 
682 	mnt = alloc_vfsmnt(name);
683 	if (!mnt)
684 		return ERR_PTR(-ENOMEM);
685 
686 	if (flags & MS_KERNMOUNT)
687 		mnt->mnt_flags = MNT_INTERNAL;
688 
689 	root = mount_fs(type, flags, name, data);
690 	if (IS_ERR(root)) {
691 		free_vfsmnt(mnt);
692 		return ERR_CAST(root);
693 	}
694 
695 	mnt->mnt_root = root;
696 	mnt->mnt_sb = root->d_sb;
697 	mnt->mnt_mountpoint = mnt->mnt_root;
698 	mnt->mnt_parent = mnt;
699 	return mnt;
700 }
701 EXPORT_SYMBOL_GPL(vfs_kern_mount);
702 
703 static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
704 					int flag)
705 {
706 	struct super_block *sb = old->mnt_sb;
707 	struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
708 
709 	if (mnt) {
710 		if (flag & (CL_SLAVE | CL_PRIVATE))
711 			mnt->mnt_group_id = 0; /* not a peer of original */
712 		else
713 			mnt->mnt_group_id = old->mnt_group_id;
714 
715 		if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
716 			int err = mnt_alloc_group_id(mnt);
717 			if (err)
718 				goto out_free;
719 		}
720 
721 		mnt->mnt_flags = old->mnt_flags & ~MNT_WRITE_HOLD;
722 		atomic_inc(&sb->s_active);
723 		mnt->mnt_sb = sb;
724 		mnt->mnt_root = dget(root);
725 		mnt->mnt_mountpoint = mnt->mnt_root;
726 		mnt->mnt_parent = mnt;
727 
728 		if (flag & CL_SLAVE) {
729 			list_add(&mnt->mnt_slave, &old->mnt_slave_list);
730 			mnt->mnt_master = old;
731 			CLEAR_MNT_SHARED(mnt);
732 		} else if (!(flag & CL_PRIVATE)) {
733 			if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
734 				list_add(&mnt->mnt_share, &old->mnt_share);
735 			if (IS_MNT_SLAVE(old))
736 				list_add(&mnt->mnt_slave, &old->mnt_slave);
737 			mnt->mnt_master = old->mnt_master;
738 		}
739 		if (flag & CL_MAKE_SHARED)
740 			set_mnt_shared(mnt);
741 
742 		/* stick the duplicate mount on the same expiry list
743 		 * as the original if that was on one */
744 		if (flag & CL_EXPIRE) {
745 			if (!list_empty(&old->mnt_expire))
746 				list_add(&mnt->mnt_expire, &old->mnt_expire);
747 		}
748 	}
749 	return mnt;
750 
751  out_free:
752 	free_vfsmnt(mnt);
753 	return NULL;
754 }
755 
756 static inline void mntfree(struct vfsmount *mnt)
757 {
758 	struct super_block *sb = mnt->mnt_sb;
759 
760 	/*
761 	 * This probably indicates that somebody messed
762 	 * up a mnt_want/drop_write() pair.  If this
763 	 * happens, the filesystem was probably unable
764 	 * to make r/w->r/o transitions.
765 	 */
766 	/*
767 	 * The locking used to deal with mnt_count decrement provides barriers,
768 	 * so mnt_get_writers() below is safe.
769 	 */
770 	WARN_ON(mnt_get_writers(mnt));
771 	fsnotify_vfsmount_delete(mnt);
772 	dput(mnt->mnt_root);
773 	free_vfsmnt(mnt);
774 	deactivate_super(sb);
775 }
776 
777 static void mntput_no_expire(struct vfsmount *mnt)
778 {
779 put_again:
780 #ifdef CONFIG_SMP
781 	br_read_lock(vfsmount_lock);
782 	if (likely(atomic_read(&mnt->mnt_longterm))) {
783 		mnt_dec_count(mnt);
784 		br_read_unlock(vfsmount_lock);
785 		return;
786 	}
787 	br_read_unlock(vfsmount_lock);
788 
789 	br_write_lock(vfsmount_lock);
790 	mnt_dec_count(mnt);
791 	if (mnt_get_count(mnt)) {
792 		br_write_unlock(vfsmount_lock);
793 		return;
794 	}
795 #else
796 	mnt_dec_count(mnt);
797 	if (likely(mnt_get_count(mnt)))
798 		return;
799 	br_write_lock(vfsmount_lock);
800 #endif
801 	if (unlikely(mnt->mnt_pinned)) {
802 		mnt_add_count(mnt, mnt->mnt_pinned + 1);
803 		mnt->mnt_pinned = 0;
804 		br_write_unlock(vfsmount_lock);
805 		acct_auto_close_mnt(mnt);
806 		goto put_again;
807 	}
808 	br_write_unlock(vfsmount_lock);
809 	mntfree(mnt);
810 }
811 
812 void mntput(struct vfsmount *mnt)
813 {
814 	if (mnt) {
815 		/* avoid cacheline pingpong, hope gcc doesn't get "smart" */
816 		if (unlikely(mnt->mnt_expiry_mark))
817 			mnt->mnt_expiry_mark = 0;
818 		mntput_no_expire(mnt);
819 	}
820 }
821 EXPORT_SYMBOL(mntput);
822 
823 struct vfsmount *mntget(struct vfsmount *mnt)
824 {
825 	if (mnt)
826 		mnt_inc_count(mnt);
827 	return mnt;
828 }
829 EXPORT_SYMBOL(mntget);
830 
831 void mnt_pin(struct vfsmount *mnt)
832 {
833 	br_write_lock(vfsmount_lock);
834 	mnt->mnt_pinned++;
835 	br_write_unlock(vfsmount_lock);
836 }
837 EXPORT_SYMBOL(mnt_pin);
838 
839 void mnt_unpin(struct vfsmount *mnt)
840 {
841 	br_write_lock(vfsmount_lock);
842 	if (mnt->mnt_pinned) {
843 		mnt_inc_count(mnt);
844 		mnt->mnt_pinned--;
845 	}
846 	br_write_unlock(vfsmount_lock);
847 }
848 EXPORT_SYMBOL(mnt_unpin);
849 
850 static inline void mangle(struct seq_file *m, const char *s)
851 {
852 	seq_escape(m, s, " \t\n\\");
853 }
854 
855 /*
856  * Simple .show_options callback for filesystems which don't want to
857  * implement more complex mount option showing.
858  *
859  * See also save_mount_options().
860  */
861 int generic_show_options(struct seq_file *m, struct vfsmount *mnt)
862 {
863 	const char *options;
864 
865 	rcu_read_lock();
866 	options = rcu_dereference(mnt->mnt_sb->s_options);
867 
868 	if (options != NULL && options[0]) {
869 		seq_putc(m, ',');
870 		mangle(m, options);
871 	}
872 	rcu_read_unlock();
873 
874 	return 0;
875 }
876 EXPORT_SYMBOL(generic_show_options);
877 
878 /*
879  * If filesystem uses generic_show_options(), this function should be
880  * called from the fill_super() callback.
881  *
882  * The .remount_fs callback usually needs to be handled in a special
883  * way, to make sure, that previous options are not overwritten if the
884  * remount fails.
885  *
886  * Also note, that if the filesystem's .remount_fs function doesn't
887  * reset all options to their default value, but changes only newly
888  * given options, then the displayed options will not reflect reality
889  * any more.
890  */
891 void save_mount_options(struct super_block *sb, char *options)
892 {
893 	BUG_ON(sb->s_options);
894 	rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
895 }
896 EXPORT_SYMBOL(save_mount_options);
897 
898 void replace_mount_options(struct super_block *sb, char *options)
899 {
900 	char *old = sb->s_options;
901 	rcu_assign_pointer(sb->s_options, options);
902 	if (old) {
903 		synchronize_rcu();
904 		kfree(old);
905 	}
906 }
907 EXPORT_SYMBOL(replace_mount_options);
908 
909 #ifdef CONFIG_PROC_FS
910 /* iterator */
911 static void *m_start(struct seq_file *m, loff_t *pos)
912 {
913 	struct proc_mounts *p = m->private;
914 
915 	down_read(&namespace_sem);
916 	return seq_list_start(&p->ns->list, *pos);
917 }
918 
919 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
920 {
921 	struct proc_mounts *p = m->private;
922 
923 	return seq_list_next(v, &p->ns->list, pos);
924 }
925 
926 static void m_stop(struct seq_file *m, void *v)
927 {
928 	up_read(&namespace_sem);
929 }
930 
931 int mnt_had_events(struct proc_mounts *p)
932 {
933 	struct mnt_namespace *ns = p->ns;
934 	int res = 0;
935 
936 	br_read_lock(vfsmount_lock);
937 	if (p->event != ns->event) {
938 		p->event = ns->event;
939 		res = 1;
940 	}
941 	br_read_unlock(vfsmount_lock);
942 
943 	return res;
944 }
945 
946 struct proc_fs_info {
947 	int flag;
948 	const char *str;
949 };
950 
951 static int show_sb_opts(struct seq_file *m, struct super_block *sb)
952 {
953 	static const struct proc_fs_info fs_info[] = {
954 		{ MS_SYNCHRONOUS, ",sync" },
955 		{ MS_DIRSYNC, ",dirsync" },
956 		{ MS_MANDLOCK, ",mand" },
957 		{ 0, NULL }
958 	};
959 	const struct proc_fs_info *fs_infop;
960 
961 	for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
962 		if (sb->s_flags & fs_infop->flag)
963 			seq_puts(m, fs_infop->str);
964 	}
965 
966 	return security_sb_show_options(m, sb);
967 }
968 
969 static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
970 {
971 	static const struct proc_fs_info mnt_info[] = {
972 		{ MNT_NOSUID, ",nosuid" },
973 		{ MNT_NODEV, ",nodev" },
974 		{ MNT_NOEXEC, ",noexec" },
975 		{ MNT_NOATIME, ",noatime" },
976 		{ MNT_NODIRATIME, ",nodiratime" },
977 		{ MNT_RELATIME, ",relatime" },
978 		{ 0, NULL }
979 	};
980 	const struct proc_fs_info *fs_infop;
981 
982 	for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
983 		if (mnt->mnt_flags & fs_infop->flag)
984 			seq_puts(m, fs_infop->str);
985 	}
986 }
987 
988 static void show_type(struct seq_file *m, struct super_block *sb)
989 {
990 	mangle(m, sb->s_type->name);
991 	if (sb->s_subtype && sb->s_subtype[0]) {
992 		seq_putc(m, '.');
993 		mangle(m, sb->s_subtype);
994 	}
995 }
996 
997 static int show_vfsmnt(struct seq_file *m, void *v)
998 {
999 	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
1000 	int err = 0;
1001 	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
1002 
1003 	if (mnt->mnt_sb->s_op->show_devname) {
1004 		err = mnt->mnt_sb->s_op->show_devname(m, mnt);
1005 		if (err)
1006 			goto out;
1007 	} else {
1008 		mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
1009 	}
1010 	seq_putc(m, ' ');
1011 	seq_path(m, &mnt_path, " \t\n\\");
1012 	seq_putc(m, ' ');
1013 	show_type(m, mnt->mnt_sb);
1014 	seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
1015 	err = show_sb_opts(m, mnt->mnt_sb);
1016 	if (err)
1017 		goto out;
1018 	show_mnt_opts(m, mnt);
1019 	if (mnt->mnt_sb->s_op->show_options)
1020 		err = mnt->mnt_sb->s_op->show_options(m, mnt);
1021 	seq_puts(m, " 0 0\n");
1022 out:
1023 	return err;
1024 }
1025 
1026 const struct seq_operations mounts_op = {
1027 	.start	= m_start,
1028 	.next	= m_next,
1029 	.stop	= m_stop,
1030 	.show	= show_vfsmnt
1031 };
1032 
1033 static int uuid_is_nil(u8 *uuid)
1034 {
1035 	int i;
1036 	u8  *cp = (u8 *)uuid;
1037 
1038 	for (i = 0; i < 16; i++) {
1039 		if (*cp++)
1040 			return 0;
1041 	}
1042 	return 1;
1043 }
1044 
1045 static int show_mountinfo(struct seq_file *m, void *v)
1046 {
1047 	struct proc_mounts *p = m->private;
1048 	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
1049 	struct super_block *sb = mnt->mnt_sb;
1050 	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
1051 	struct path root = p->root;
1052 	int err = 0;
1053 
1054 	seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id,
1055 		   MAJOR(sb->s_dev), MINOR(sb->s_dev));
1056 	if (sb->s_op->show_path)
1057 		err = sb->s_op->show_path(m, mnt);
1058 	else
1059 		seq_dentry(m, mnt->mnt_root, " \t\n\\");
1060 	if (err)
1061 		goto out;
1062 	seq_putc(m, ' ');
1063 	seq_path_root(m, &mnt_path, &root, " \t\n\\");
1064 	if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) {
1065 		/*
1066 		 * Mountpoint is outside root, discard that one.  Ugly,
1067 		 * but less so than trying to do that in iterator in a
1068 		 * race-free way (due to renames).
1069 		 */
1070 		return SEQ_SKIP;
1071 	}
1072 	seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
1073 	show_mnt_opts(m, mnt);
1074 
1075 	/* Tagged fields ("foo:X" or "bar") */
1076 	if (IS_MNT_SHARED(mnt))
1077 		seq_printf(m, " shared:%i", mnt->mnt_group_id);
1078 	if (IS_MNT_SLAVE(mnt)) {
1079 		int master = mnt->mnt_master->mnt_group_id;
1080 		int dom = get_dominating_id(mnt, &p->root);
1081 		seq_printf(m, " master:%i", master);
1082 		if (dom && dom != master)
1083 			seq_printf(m, " propagate_from:%i", dom);
1084 	}
1085 	if (IS_MNT_UNBINDABLE(mnt))
1086 		seq_puts(m, " unbindable");
1087 
1088 	if (!uuid_is_nil(mnt->mnt_sb->s_uuid))
1089 		/* print the uuid */
1090 		seq_printf(m, " uuid:%pU", mnt->mnt_sb->s_uuid);
1091 
1092 	/* Filesystem specific data */
1093 	seq_puts(m, " - ");
1094 	show_type(m, sb);
1095 	seq_putc(m, ' ');
1096 	if (sb->s_op->show_devname)
1097 		err = sb->s_op->show_devname(m, mnt);
1098 	else
1099 		mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
1100 	if (err)
1101 		goto out;
1102 	seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
1103 	err = show_sb_opts(m, sb);
1104 	if (err)
1105 		goto out;
1106 	if (sb->s_op->show_options)
1107 		err = sb->s_op->show_options(m, mnt);
1108 	seq_putc(m, '\n');
1109 out:
1110 	return err;
1111 }
1112 
1113 const struct seq_operations mountinfo_op = {
1114 	.start	= m_start,
1115 	.next	= m_next,
1116 	.stop	= m_stop,
1117 	.show	= show_mountinfo,
1118 };
1119 
1120 static int show_vfsstat(struct seq_file *m, void *v)
1121 {
1122 	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
1123 	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
1124 	int err = 0;
1125 
1126 	/* device */
1127 	if (mnt->mnt_sb->s_op->show_devname) {
1128 		err = mnt->mnt_sb->s_op->show_devname(m, mnt);
1129 	} else {
1130 		if (mnt->mnt_devname) {
1131 			seq_puts(m, "device ");
1132 			mangle(m, mnt->mnt_devname);
1133 		} else
1134 			seq_puts(m, "no device");
1135 	}
1136 
1137 	/* mount point */
1138 	seq_puts(m, " mounted on ");
1139 	seq_path(m, &mnt_path, " \t\n\\");
1140 	seq_putc(m, ' ');
1141 
1142 	/* file system type */
1143 	seq_puts(m, "with fstype ");
1144 	show_type(m, mnt->mnt_sb);
1145 
1146 	/* optional statistics */
1147 	if (mnt->mnt_sb->s_op->show_stats) {
1148 		seq_putc(m, ' ');
1149 		if (!err)
1150 			err = mnt->mnt_sb->s_op->show_stats(m, mnt);
1151 	}
1152 
1153 	seq_putc(m, '\n');
1154 	return err;
1155 }
1156 
1157 const struct seq_operations mountstats_op = {
1158 	.start	= m_start,
1159 	.next	= m_next,
1160 	.stop	= m_stop,
1161 	.show	= show_vfsstat,
1162 };
1163 #endif  /* CONFIG_PROC_FS */
1164 
1165 /**
1166  * may_umount_tree - check if a mount tree is busy
1167  * @mnt: root of mount tree
1168  *
1169  * This is called to check if a tree of mounts has any
1170  * open files, pwds, chroots or sub mounts that are
1171  * busy.
1172  */
1173 int may_umount_tree(struct vfsmount *mnt)
1174 {
1175 	int actual_refs = 0;
1176 	int minimum_refs = 0;
1177 	struct vfsmount *p;
1178 
1179 	/* write lock needed for mnt_get_count */
1180 	br_write_lock(vfsmount_lock);
1181 	for (p = mnt; p; p = next_mnt(p, mnt)) {
1182 		actual_refs += mnt_get_count(p);
1183 		minimum_refs += 2;
1184 	}
1185 	br_write_unlock(vfsmount_lock);
1186 
1187 	if (actual_refs > minimum_refs)
1188 		return 0;
1189 
1190 	return 1;
1191 }
1192 
1193 EXPORT_SYMBOL(may_umount_tree);
1194 
1195 /**
1196  * may_umount - check if a mount point is busy
1197  * @mnt: root of mount
1198  *
1199  * This is called to check if a mount point has any
1200  * open files, pwds, chroots or sub mounts. If the
1201  * mount has sub mounts this will return busy
1202  * regardless of whether the sub mounts are busy.
1203  *
1204  * Doesn't take quota and stuff into account. IOW, in some cases it will
1205  * give false negatives. The main reason why it's here is that we need
1206  * a non-destructive way to look for easily umountable filesystems.
1207  */
1208 int may_umount(struct vfsmount *mnt)
1209 {
1210 	int ret = 1;
1211 	down_read(&namespace_sem);
1212 	br_write_lock(vfsmount_lock);
1213 	if (propagate_mount_busy(mnt, 2))
1214 		ret = 0;
1215 	br_write_unlock(vfsmount_lock);
1216 	up_read(&namespace_sem);
1217 	return ret;
1218 }
1219 
1220 EXPORT_SYMBOL(may_umount);
1221 
1222 void release_mounts(struct list_head *head)
1223 {
1224 	struct vfsmount *mnt;
1225 	while (!list_empty(head)) {
1226 		mnt = list_first_entry(head, struct vfsmount, mnt_hash);
1227 		list_del_init(&mnt->mnt_hash);
1228 		if (mnt->mnt_parent != mnt) {
1229 			struct dentry *dentry;
1230 			struct vfsmount *m;
1231 
1232 			br_write_lock(vfsmount_lock);
1233 			dentry = mnt->mnt_mountpoint;
1234 			m = mnt->mnt_parent;
1235 			mnt->mnt_mountpoint = mnt->mnt_root;
1236 			mnt->mnt_parent = mnt;
1237 			m->mnt_ghosts--;
1238 			br_write_unlock(vfsmount_lock);
1239 			dput(dentry);
1240 			mntput(m);
1241 		}
1242 		mntput(mnt);
1243 	}
1244 }
1245 
1246 /*
1247  * vfsmount lock must be held for write
1248  * namespace_sem must be held for write
1249  */
1250 void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
1251 {
1252 	LIST_HEAD(tmp_list);
1253 	struct vfsmount *p;
1254 
1255 	for (p = mnt; p; p = next_mnt(p, mnt))
1256 		list_move(&p->mnt_hash, &tmp_list);
1257 
1258 	if (propagate)
1259 		propagate_umount(&tmp_list);
1260 
1261 	list_for_each_entry(p, &tmp_list, mnt_hash) {
1262 		list_del_init(&p->mnt_expire);
1263 		list_del_init(&p->mnt_list);
1264 		__touch_mnt_namespace(p->mnt_ns);
1265 		p->mnt_ns = NULL;
1266 		__mnt_make_shortterm(p);
1267 		list_del_init(&p->mnt_child);
1268 		if (p->mnt_parent != p) {
1269 			p->mnt_parent->mnt_ghosts++;
1270 			dentry_reset_mounted(p->mnt_parent, p->mnt_mountpoint);
1271 		}
1272 		change_mnt_propagation(p, MS_PRIVATE);
1273 	}
1274 	list_splice(&tmp_list, kill);
1275 }
1276 
1277 static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts);
1278 
1279 static int do_umount(struct vfsmount *mnt, int flags)
1280 {
1281 	struct super_block *sb = mnt->mnt_sb;
1282 	int retval;
1283 	LIST_HEAD(umount_list);
1284 
1285 	retval = security_sb_umount(mnt, flags);
1286 	if (retval)
1287 		return retval;
1288 
1289 	/*
1290 	 * Allow userspace to request a mountpoint be expired rather than
1291 	 * unmounting unconditionally. Unmount only happens if:
1292 	 *  (1) the mark is already set (the mark is cleared by mntput())
1293 	 *  (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1294 	 */
1295 	if (flags & MNT_EXPIRE) {
1296 		if (mnt == current->fs->root.mnt ||
1297 		    flags & (MNT_FORCE | MNT_DETACH))
1298 			return -EINVAL;
1299 
1300 		/*
1301 		 * probably don't strictly need the lock here if we examined
1302 		 * all race cases, but it's a slowpath.
1303 		 */
1304 		br_write_lock(vfsmount_lock);
1305 		if (mnt_get_count(mnt) != 2) {
1306 			br_write_unlock(vfsmount_lock);
1307 			return -EBUSY;
1308 		}
1309 		br_write_unlock(vfsmount_lock);
1310 
1311 		if (!xchg(&mnt->mnt_expiry_mark, 1))
1312 			return -EAGAIN;
1313 	}
1314 
1315 	/*
1316 	 * If we may have to abort operations to get out of this
1317 	 * mount, and they will themselves hold resources we must
1318 	 * allow the fs to do things. In the Unix tradition of
1319 	 * 'Gee thats tricky lets do it in userspace' the umount_begin
1320 	 * might fail to complete on the first run through as other tasks
1321 	 * must return, and the like. Thats for the mount program to worry
1322 	 * about for the moment.
1323 	 */
1324 
1325 	if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1326 		sb->s_op->umount_begin(sb);
1327 	}
1328 
1329 	/*
1330 	 * No sense to grab the lock for this test, but test itself looks
1331 	 * somewhat bogus. Suggestions for better replacement?
1332 	 * Ho-hum... In principle, we might treat that as umount + switch
1333 	 * to rootfs. GC would eventually take care of the old vfsmount.
1334 	 * Actually it makes sense, especially if rootfs would contain a
1335 	 * /reboot - static binary that would close all descriptors and
1336 	 * call reboot(9). Then init(8) could umount root and exec /reboot.
1337 	 */
1338 	if (mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1339 		/*
1340 		 * Special case for "unmounting" root ...
1341 		 * we just try to remount it readonly.
1342 		 */
1343 		down_write(&sb->s_umount);
1344 		if (!(sb->s_flags & MS_RDONLY))
1345 			retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1346 		up_write(&sb->s_umount);
1347 		return retval;
1348 	}
1349 
1350 	down_write(&namespace_sem);
1351 	br_write_lock(vfsmount_lock);
1352 	event++;
1353 
1354 	if (!(flags & MNT_DETACH))
1355 		shrink_submounts(mnt, &umount_list);
1356 
1357 	retval = -EBUSY;
1358 	if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
1359 		if (!list_empty(&mnt->mnt_list))
1360 			umount_tree(mnt, 1, &umount_list);
1361 		retval = 0;
1362 	}
1363 	br_write_unlock(vfsmount_lock);
1364 	up_write(&namespace_sem);
1365 	release_mounts(&umount_list);
1366 	return retval;
1367 }
1368 
1369 /*
1370  * Now umount can handle mount points as well as block devices.
1371  * This is important for filesystems which use unnamed block devices.
1372  *
1373  * We now support a flag for forced unmount like the other 'big iron'
1374  * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1375  */
1376 
1377 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1378 {
1379 	struct path path;
1380 	int retval;
1381 	int lookup_flags = 0;
1382 
1383 	if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1384 		return -EINVAL;
1385 
1386 	if (!(flags & UMOUNT_NOFOLLOW))
1387 		lookup_flags |= LOOKUP_FOLLOW;
1388 
1389 	retval = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1390 	if (retval)
1391 		goto out;
1392 	retval = -EINVAL;
1393 	if (path.dentry != path.mnt->mnt_root)
1394 		goto dput_and_out;
1395 	if (!check_mnt(path.mnt))
1396 		goto dput_and_out;
1397 
1398 	retval = -EPERM;
1399 	if (!capable(CAP_SYS_ADMIN))
1400 		goto dput_and_out;
1401 
1402 	retval = do_umount(path.mnt, flags);
1403 dput_and_out:
1404 	/* we mustn't call path_put() as that would clear mnt_expiry_mark */
1405 	dput(path.dentry);
1406 	mntput_no_expire(path.mnt);
1407 out:
1408 	return retval;
1409 }
1410 
1411 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1412 
1413 /*
1414  *	The 2.0 compatible umount. No flags.
1415  */
1416 SYSCALL_DEFINE1(oldumount, char __user *, name)
1417 {
1418 	return sys_umount(name, 0);
1419 }
1420 
1421 #endif
1422 
1423 static int mount_is_safe(struct path *path)
1424 {
1425 	if (capable(CAP_SYS_ADMIN))
1426 		return 0;
1427 	return -EPERM;
1428 #ifdef notyet
1429 	if (S_ISLNK(path->dentry->d_inode->i_mode))
1430 		return -EPERM;
1431 	if (path->dentry->d_inode->i_mode & S_ISVTX) {
1432 		if (current_uid() != path->dentry->d_inode->i_uid)
1433 			return -EPERM;
1434 	}
1435 	if (inode_permission(path->dentry->d_inode, MAY_WRITE))
1436 		return -EPERM;
1437 	return 0;
1438 #endif
1439 }
1440 
1441 struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
1442 					int flag)
1443 {
1444 	struct vfsmount *res, *p, *q, *r, *s;
1445 	struct path path;
1446 
1447 	if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
1448 		return NULL;
1449 
1450 	res = q = clone_mnt(mnt, dentry, flag);
1451 	if (!q)
1452 		goto Enomem;
1453 	q->mnt_mountpoint = mnt->mnt_mountpoint;
1454 
1455 	p = mnt;
1456 	list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1457 		if (!is_subdir(r->mnt_mountpoint, dentry))
1458 			continue;
1459 
1460 		for (s = r; s; s = next_mnt(s, r)) {
1461 			if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
1462 				s = skip_mnt_tree(s);
1463 				continue;
1464 			}
1465 			while (p != s->mnt_parent) {
1466 				p = p->mnt_parent;
1467 				q = q->mnt_parent;
1468 			}
1469 			p = s;
1470 			path.mnt = q;
1471 			path.dentry = p->mnt_mountpoint;
1472 			q = clone_mnt(p, p->mnt_root, flag);
1473 			if (!q)
1474 				goto Enomem;
1475 			br_write_lock(vfsmount_lock);
1476 			list_add_tail(&q->mnt_list, &res->mnt_list);
1477 			attach_mnt(q, &path);
1478 			br_write_unlock(vfsmount_lock);
1479 		}
1480 	}
1481 	return res;
1482 Enomem:
1483 	if (res) {
1484 		LIST_HEAD(umount_list);
1485 		br_write_lock(vfsmount_lock);
1486 		umount_tree(res, 0, &umount_list);
1487 		br_write_unlock(vfsmount_lock);
1488 		release_mounts(&umount_list);
1489 	}
1490 	return NULL;
1491 }
1492 
1493 struct vfsmount *collect_mounts(struct path *path)
1494 {
1495 	struct vfsmount *tree;
1496 	down_write(&namespace_sem);
1497 	tree = copy_tree(path->mnt, path->dentry, CL_COPY_ALL | CL_PRIVATE);
1498 	up_write(&namespace_sem);
1499 	return tree;
1500 }
1501 
1502 void drop_collected_mounts(struct vfsmount *mnt)
1503 {
1504 	LIST_HEAD(umount_list);
1505 	down_write(&namespace_sem);
1506 	br_write_lock(vfsmount_lock);
1507 	umount_tree(mnt, 0, &umount_list);
1508 	br_write_unlock(vfsmount_lock);
1509 	up_write(&namespace_sem);
1510 	release_mounts(&umount_list);
1511 }
1512 
1513 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1514 		   struct vfsmount *root)
1515 {
1516 	struct vfsmount *mnt;
1517 	int res = f(root, arg);
1518 	if (res)
1519 		return res;
1520 	list_for_each_entry(mnt, &root->mnt_list, mnt_list) {
1521 		res = f(mnt, arg);
1522 		if (res)
1523 			return res;
1524 	}
1525 	return 0;
1526 }
1527 
1528 static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end)
1529 {
1530 	struct vfsmount *p;
1531 
1532 	for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1533 		if (p->mnt_group_id && !IS_MNT_SHARED(p))
1534 			mnt_release_group_id(p);
1535 	}
1536 }
1537 
1538 static int invent_group_ids(struct vfsmount *mnt, bool recurse)
1539 {
1540 	struct vfsmount *p;
1541 
1542 	for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1543 		if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1544 			int err = mnt_alloc_group_id(p);
1545 			if (err) {
1546 				cleanup_group_ids(mnt, p);
1547 				return err;
1548 			}
1549 		}
1550 	}
1551 
1552 	return 0;
1553 }
1554 
1555 /*
1556  *  @source_mnt : mount tree to be attached
1557  *  @nd         : place the mount tree @source_mnt is attached
1558  *  @parent_nd  : if non-null, detach the source_mnt from its parent and
1559  *  		   store the parent mount and mountpoint dentry.
1560  *  		   (done when source_mnt is moved)
1561  *
1562  *  NOTE: in the table below explains the semantics when a source mount
1563  *  of a given type is attached to a destination mount of a given type.
1564  * ---------------------------------------------------------------------------
1565  * |         BIND MOUNT OPERATION                                            |
1566  * |**************************************************************************
1567  * | source-->| shared        |       private  |       slave    | unbindable |
1568  * | dest     |               |                |                |            |
1569  * |   |      |               |                |                |            |
1570  * |   v      |               |                |                |            |
1571  * |**************************************************************************
1572  * |  shared  | shared (++)   |     shared (+) |     shared(+++)|  invalid   |
1573  * |          |               |                |                |            |
1574  * |non-shared| shared (+)    |      private   |      slave (*) |  invalid   |
1575  * ***************************************************************************
1576  * A bind operation clones the source mount and mounts the clone on the
1577  * destination mount.
1578  *
1579  * (++)  the cloned mount is propagated to all the mounts in the propagation
1580  * 	 tree of the destination mount and the cloned mount is added to
1581  * 	 the peer group of the source mount.
1582  * (+)   the cloned mount is created under the destination mount and is marked
1583  *       as shared. The cloned mount is added to the peer group of the source
1584  *       mount.
1585  * (+++) the mount is propagated to all the mounts in the propagation tree
1586  *       of the destination mount and the cloned mount is made slave
1587  *       of the same master as that of the source mount. The cloned mount
1588  *       is marked as 'shared and slave'.
1589  * (*)   the cloned mount is made a slave of the same master as that of the
1590  * 	 source mount.
1591  *
1592  * ---------------------------------------------------------------------------
1593  * |         		MOVE MOUNT OPERATION                                 |
1594  * |**************************************************************************
1595  * | source-->| shared        |       private  |       slave    | unbindable |
1596  * | dest     |               |                |                |            |
1597  * |   |      |               |                |                |            |
1598  * |   v      |               |                |                |            |
1599  * |**************************************************************************
1600  * |  shared  | shared (+)    |     shared (+) |    shared(+++) |  invalid   |
1601  * |          |               |                |                |            |
1602  * |non-shared| shared (+*)   |      private   |    slave (*)   | unbindable |
1603  * ***************************************************************************
1604  *
1605  * (+)  the mount is moved to the destination. And is then propagated to
1606  * 	all the mounts in the propagation tree of the destination mount.
1607  * (+*)  the mount is moved to the destination.
1608  * (+++)  the mount is moved to the destination and is then propagated to
1609  * 	all the mounts belonging to the destination mount's propagation tree.
1610  * 	the mount is marked as 'shared and slave'.
1611  * (*)	the mount continues to be a slave at the new location.
1612  *
1613  * if the source mount is a tree, the operations explained above is
1614  * applied to each mount in the tree.
1615  * Must be called without spinlocks held, since this function can sleep
1616  * in allocations.
1617  */
1618 static int attach_recursive_mnt(struct vfsmount *source_mnt,
1619 			struct path *path, struct path *parent_path)
1620 {
1621 	LIST_HEAD(tree_list);
1622 	struct vfsmount *dest_mnt = path->mnt;
1623 	struct dentry *dest_dentry = path->dentry;
1624 	struct vfsmount *child, *p;
1625 	int err;
1626 
1627 	if (IS_MNT_SHARED(dest_mnt)) {
1628 		err = invent_group_ids(source_mnt, true);
1629 		if (err)
1630 			goto out;
1631 	}
1632 	err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
1633 	if (err)
1634 		goto out_cleanup_ids;
1635 
1636 	br_write_lock(vfsmount_lock);
1637 
1638 	if (IS_MNT_SHARED(dest_mnt)) {
1639 		for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1640 			set_mnt_shared(p);
1641 	}
1642 	if (parent_path) {
1643 		detach_mnt(source_mnt, parent_path);
1644 		attach_mnt(source_mnt, path);
1645 		touch_mnt_namespace(parent_path->mnt->mnt_ns);
1646 	} else {
1647 		mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
1648 		commit_tree(source_mnt);
1649 	}
1650 
1651 	list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
1652 		list_del_init(&child->mnt_hash);
1653 		commit_tree(child);
1654 	}
1655 	br_write_unlock(vfsmount_lock);
1656 
1657 	return 0;
1658 
1659  out_cleanup_ids:
1660 	if (IS_MNT_SHARED(dest_mnt))
1661 		cleanup_group_ids(source_mnt, NULL);
1662  out:
1663 	return err;
1664 }
1665 
1666 static int lock_mount(struct path *path)
1667 {
1668 	struct vfsmount *mnt;
1669 retry:
1670 	mutex_lock(&path->dentry->d_inode->i_mutex);
1671 	if (unlikely(cant_mount(path->dentry))) {
1672 		mutex_unlock(&path->dentry->d_inode->i_mutex);
1673 		return -ENOENT;
1674 	}
1675 	down_write(&namespace_sem);
1676 	mnt = lookup_mnt(path);
1677 	if (likely(!mnt))
1678 		return 0;
1679 	up_write(&namespace_sem);
1680 	mutex_unlock(&path->dentry->d_inode->i_mutex);
1681 	path_put(path);
1682 	path->mnt = mnt;
1683 	path->dentry = dget(mnt->mnt_root);
1684 	goto retry;
1685 }
1686 
1687 static void unlock_mount(struct path *path)
1688 {
1689 	up_write(&namespace_sem);
1690 	mutex_unlock(&path->dentry->d_inode->i_mutex);
1691 }
1692 
1693 static int graft_tree(struct vfsmount *mnt, struct path *path)
1694 {
1695 	if (mnt->mnt_sb->s_flags & MS_NOUSER)
1696 		return -EINVAL;
1697 
1698 	if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1699 	      S_ISDIR(mnt->mnt_root->d_inode->i_mode))
1700 		return -ENOTDIR;
1701 
1702 	if (d_unlinked(path->dentry))
1703 		return -ENOENT;
1704 
1705 	return attach_recursive_mnt(mnt, path, NULL);
1706 }
1707 
1708 /*
1709  * Sanity check the flags to change_mnt_propagation.
1710  */
1711 
1712 static int flags_to_propagation_type(int flags)
1713 {
1714 	int type = flags & ~MS_REC;
1715 
1716 	/* Fail if any non-propagation flags are set */
1717 	if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1718 		return 0;
1719 	/* Only one propagation flag should be set */
1720 	if (!is_power_of_2(type))
1721 		return 0;
1722 	return type;
1723 }
1724 
1725 /*
1726  * recursively change the type of the mountpoint.
1727  */
1728 static int do_change_type(struct path *path, int flag)
1729 {
1730 	struct vfsmount *m, *mnt = path->mnt;
1731 	int recurse = flag & MS_REC;
1732 	int type;
1733 	int err = 0;
1734 
1735 	if (!capable(CAP_SYS_ADMIN))
1736 		return -EPERM;
1737 
1738 	if (path->dentry != path->mnt->mnt_root)
1739 		return -EINVAL;
1740 
1741 	type = flags_to_propagation_type(flag);
1742 	if (!type)
1743 		return -EINVAL;
1744 
1745 	down_write(&namespace_sem);
1746 	if (type == MS_SHARED) {
1747 		err = invent_group_ids(mnt, recurse);
1748 		if (err)
1749 			goto out_unlock;
1750 	}
1751 
1752 	br_write_lock(vfsmount_lock);
1753 	for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1754 		change_mnt_propagation(m, type);
1755 	br_write_unlock(vfsmount_lock);
1756 
1757  out_unlock:
1758 	up_write(&namespace_sem);
1759 	return err;
1760 }
1761 
1762 /*
1763  * do loopback mount.
1764  */
1765 static int do_loopback(struct path *path, char *old_name,
1766 				int recurse)
1767 {
1768 	LIST_HEAD(umount_list);
1769 	struct path old_path;
1770 	struct vfsmount *mnt = NULL;
1771 	int err = mount_is_safe(path);
1772 	if (err)
1773 		return err;
1774 	if (!old_name || !*old_name)
1775 		return -EINVAL;
1776 	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1777 	if (err)
1778 		return err;
1779 
1780 	err = lock_mount(path);
1781 	if (err)
1782 		goto out;
1783 
1784 	err = -EINVAL;
1785 	if (IS_MNT_UNBINDABLE(old_path.mnt))
1786 		goto out2;
1787 
1788 	if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
1789 		goto out2;
1790 
1791 	err = -ENOMEM;
1792 	if (recurse)
1793 		mnt = copy_tree(old_path.mnt, old_path.dentry, 0);
1794 	else
1795 		mnt = clone_mnt(old_path.mnt, old_path.dentry, 0);
1796 
1797 	if (!mnt)
1798 		goto out2;
1799 
1800 	err = graft_tree(mnt, path);
1801 	if (err) {
1802 		br_write_lock(vfsmount_lock);
1803 		umount_tree(mnt, 0, &umount_list);
1804 		br_write_unlock(vfsmount_lock);
1805 	}
1806 out2:
1807 	unlock_mount(path);
1808 	release_mounts(&umount_list);
1809 out:
1810 	path_put(&old_path);
1811 	return err;
1812 }
1813 
1814 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1815 {
1816 	int error = 0;
1817 	int readonly_request = 0;
1818 
1819 	if (ms_flags & MS_RDONLY)
1820 		readonly_request = 1;
1821 	if (readonly_request == __mnt_is_readonly(mnt))
1822 		return 0;
1823 
1824 	if (readonly_request)
1825 		error = mnt_make_readonly(mnt);
1826 	else
1827 		__mnt_unmake_readonly(mnt);
1828 	return error;
1829 }
1830 
1831 /*
1832  * change filesystem flags. dir should be a physical root of filesystem.
1833  * If you've mounted a non-root directory somewhere and want to do remount
1834  * on it - tough luck.
1835  */
1836 static int do_remount(struct path *path, int flags, int mnt_flags,
1837 		      void *data)
1838 {
1839 	int err;
1840 	struct super_block *sb = path->mnt->mnt_sb;
1841 
1842 	if (!capable(CAP_SYS_ADMIN))
1843 		return -EPERM;
1844 
1845 	if (!check_mnt(path->mnt))
1846 		return -EINVAL;
1847 
1848 	if (path->dentry != path->mnt->mnt_root)
1849 		return -EINVAL;
1850 
1851 	err = security_sb_remount(sb, data);
1852 	if (err)
1853 		return err;
1854 
1855 	down_write(&sb->s_umount);
1856 	if (flags & MS_BIND)
1857 		err = change_mount_flags(path->mnt, flags);
1858 	else
1859 		err = do_remount_sb(sb, flags, data, 0);
1860 	if (!err) {
1861 		br_write_lock(vfsmount_lock);
1862 		mnt_flags |= path->mnt->mnt_flags & MNT_PROPAGATION_MASK;
1863 		path->mnt->mnt_flags = mnt_flags;
1864 		br_write_unlock(vfsmount_lock);
1865 	}
1866 	up_write(&sb->s_umount);
1867 	if (!err) {
1868 		br_write_lock(vfsmount_lock);
1869 		touch_mnt_namespace(path->mnt->mnt_ns);
1870 		br_write_unlock(vfsmount_lock);
1871 	}
1872 	return err;
1873 }
1874 
1875 static inline int tree_contains_unbindable(struct vfsmount *mnt)
1876 {
1877 	struct vfsmount *p;
1878 	for (p = mnt; p; p = next_mnt(p, mnt)) {
1879 		if (IS_MNT_UNBINDABLE(p))
1880 			return 1;
1881 	}
1882 	return 0;
1883 }
1884 
1885 static int do_move_mount(struct path *path, char *old_name)
1886 {
1887 	struct path old_path, parent_path;
1888 	struct vfsmount *p;
1889 	int err = 0;
1890 	if (!capable(CAP_SYS_ADMIN))
1891 		return -EPERM;
1892 	if (!old_name || !*old_name)
1893 		return -EINVAL;
1894 	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1895 	if (err)
1896 		return err;
1897 
1898 	err = lock_mount(path);
1899 	if (err < 0)
1900 		goto out;
1901 
1902 	err = -EINVAL;
1903 	if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
1904 		goto out1;
1905 
1906 	if (d_unlinked(path->dentry))
1907 		goto out1;
1908 
1909 	err = -EINVAL;
1910 	if (old_path.dentry != old_path.mnt->mnt_root)
1911 		goto out1;
1912 
1913 	if (old_path.mnt == old_path.mnt->mnt_parent)
1914 		goto out1;
1915 
1916 	if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1917 	      S_ISDIR(old_path.dentry->d_inode->i_mode))
1918 		goto out1;
1919 	/*
1920 	 * Don't move a mount residing in a shared parent.
1921 	 */
1922 	if (old_path.mnt->mnt_parent &&
1923 	    IS_MNT_SHARED(old_path.mnt->mnt_parent))
1924 		goto out1;
1925 	/*
1926 	 * Don't move a mount tree containing unbindable mounts to a destination
1927 	 * mount which is shared.
1928 	 */
1929 	if (IS_MNT_SHARED(path->mnt) &&
1930 	    tree_contains_unbindable(old_path.mnt))
1931 		goto out1;
1932 	err = -ELOOP;
1933 	for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent)
1934 		if (p == old_path.mnt)
1935 			goto out1;
1936 
1937 	err = attach_recursive_mnt(old_path.mnt, path, &parent_path);
1938 	if (err)
1939 		goto out1;
1940 
1941 	/* if the mount is moved, it should no longer be expire
1942 	 * automatically */
1943 	list_del_init(&old_path.mnt->mnt_expire);
1944 out1:
1945 	unlock_mount(path);
1946 out:
1947 	if (!err)
1948 		path_put(&parent_path);
1949 	path_put(&old_path);
1950 	return err;
1951 }
1952 
1953 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
1954 {
1955 	int err;
1956 	const char *subtype = strchr(fstype, '.');
1957 	if (subtype) {
1958 		subtype++;
1959 		err = -EINVAL;
1960 		if (!subtype[0])
1961 			goto err;
1962 	} else
1963 		subtype = "";
1964 
1965 	mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
1966 	err = -ENOMEM;
1967 	if (!mnt->mnt_sb->s_subtype)
1968 		goto err;
1969 	return mnt;
1970 
1971  err:
1972 	mntput(mnt);
1973 	return ERR_PTR(err);
1974 }
1975 
1976 struct vfsmount *
1977 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
1978 {
1979 	struct file_system_type *type = get_fs_type(fstype);
1980 	struct vfsmount *mnt;
1981 	if (!type)
1982 		return ERR_PTR(-ENODEV);
1983 	mnt = vfs_kern_mount(type, flags, name, data);
1984 	if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
1985 	    !mnt->mnt_sb->s_subtype)
1986 		mnt = fs_set_subtype(mnt, fstype);
1987 	put_filesystem(type);
1988 	return mnt;
1989 }
1990 EXPORT_SYMBOL_GPL(do_kern_mount);
1991 
1992 /*
1993  * add a mount into a namespace's mount tree
1994  */
1995 static int do_add_mount(struct vfsmount *newmnt, struct path *path, int mnt_flags)
1996 {
1997 	int err;
1998 
1999 	mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
2000 
2001 	err = lock_mount(path);
2002 	if (err)
2003 		return err;
2004 
2005 	err = -EINVAL;
2006 	if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt))
2007 		goto unlock;
2008 
2009 	/* Refuse the same filesystem on the same mount point */
2010 	err = -EBUSY;
2011 	if (path->mnt->mnt_sb == newmnt->mnt_sb &&
2012 	    path->mnt->mnt_root == path->dentry)
2013 		goto unlock;
2014 
2015 	err = -EINVAL;
2016 	if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
2017 		goto unlock;
2018 
2019 	newmnt->mnt_flags = mnt_flags;
2020 	err = graft_tree(newmnt, path);
2021 
2022 unlock:
2023 	unlock_mount(path);
2024 	return err;
2025 }
2026 
2027 /*
2028  * create a new mount for userspace and request it to be added into the
2029  * namespace's tree
2030  */
2031 static int do_new_mount(struct path *path, char *type, int flags,
2032 			int mnt_flags, char *name, void *data)
2033 {
2034 	struct vfsmount *mnt;
2035 	int err;
2036 
2037 	if (!type)
2038 		return -EINVAL;
2039 
2040 	/* we need capabilities... */
2041 	if (!capable(CAP_SYS_ADMIN))
2042 		return -EPERM;
2043 
2044 	mnt = do_kern_mount(type, flags, name, data);
2045 	if (IS_ERR(mnt))
2046 		return PTR_ERR(mnt);
2047 
2048 	err = do_add_mount(mnt, path, mnt_flags);
2049 	if (err)
2050 		mntput(mnt);
2051 	return err;
2052 }
2053 
2054 int finish_automount(struct vfsmount *m, struct path *path)
2055 {
2056 	int err;
2057 	/* The new mount record should have at least 2 refs to prevent it being
2058 	 * expired before we get a chance to add it
2059 	 */
2060 	BUG_ON(mnt_get_count(m) < 2);
2061 
2062 	if (m->mnt_sb == path->mnt->mnt_sb &&
2063 	    m->mnt_root == path->dentry) {
2064 		err = -ELOOP;
2065 		goto fail;
2066 	}
2067 
2068 	err = do_add_mount(m, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2069 	if (!err)
2070 		return 0;
2071 fail:
2072 	/* remove m from any expiration list it may be on */
2073 	if (!list_empty(&m->mnt_expire)) {
2074 		down_write(&namespace_sem);
2075 		br_write_lock(vfsmount_lock);
2076 		list_del_init(&m->mnt_expire);
2077 		br_write_unlock(vfsmount_lock);
2078 		up_write(&namespace_sem);
2079 	}
2080 	mntput(m);
2081 	mntput(m);
2082 	return err;
2083 }
2084 
2085 /**
2086  * mnt_set_expiry - Put a mount on an expiration list
2087  * @mnt: The mount to list.
2088  * @expiry_list: The list to add the mount to.
2089  */
2090 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2091 {
2092 	down_write(&namespace_sem);
2093 	br_write_lock(vfsmount_lock);
2094 
2095 	list_add_tail(&mnt->mnt_expire, expiry_list);
2096 
2097 	br_write_unlock(vfsmount_lock);
2098 	up_write(&namespace_sem);
2099 }
2100 EXPORT_SYMBOL(mnt_set_expiry);
2101 
2102 /*
2103  * process a list of expirable mountpoints with the intent of discarding any
2104  * mountpoints that aren't in use and haven't been touched since last we came
2105  * here
2106  */
2107 void mark_mounts_for_expiry(struct list_head *mounts)
2108 {
2109 	struct vfsmount *mnt, *next;
2110 	LIST_HEAD(graveyard);
2111 	LIST_HEAD(umounts);
2112 
2113 	if (list_empty(mounts))
2114 		return;
2115 
2116 	down_write(&namespace_sem);
2117 	br_write_lock(vfsmount_lock);
2118 
2119 	/* extract from the expiration list every vfsmount that matches the
2120 	 * following criteria:
2121 	 * - only referenced by its parent vfsmount
2122 	 * - still marked for expiry (marked on the last call here; marks are
2123 	 *   cleared by mntput())
2124 	 */
2125 	list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2126 		if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2127 			propagate_mount_busy(mnt, 1))
2128 			continue;
2129 		list_move(&mnt->mnt_expire, &graveyard);
2130 	}
2131 	while (!list_empty(&graveyard)) {
2132 		mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire);
2133 		touch_mnt_namespace(mnt->mnt_ns);
2134 		umount_tree(mnt, 1, &umounts);
2135 	}
2136 	br_write_unlock(vfsmount_lock);
2137 	up_write(&namespace_sem);
2138 
2139 	release_mounts(&umounts);
2140 }
2141 
2142 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2143 
2144 /*
2145  * Ripoff of 'select_parent()'
2146  *
2147  * search the list of submounts for a given mountpoint, and move any
2148  * shrinkable submounts to the 'graveyard' list.
2149  */
2150 static int select_submounts(struct vfsmount *parent, struct list_head *graveyard)
2151 {
2152 	struct vfsmount *this_parent = parent;
2153 	struct list_head *next;
2154 	int found = 0;
2155 
2156 repeat:
2157 	next = this_parent->mnt_mounts.next;
2158 resume:
2159 	while (next != &this_parent->mnt_mounts) {
2160 		struct list_head *tmp = next;
2161 		struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child);
2162 
2163 		next = tmp->next;
2164 		if (!(mnt->mnt_flags & MNT_SHRINKABLE))
2165 			continue;
2166 		/*
2167 		 * Descend a level if the d_mounts list is non-empty.
2168 		 */
2169 		if (!list_empty(&mnt->mnt_mounts)) {
2170 			this_parent = mnt;
2171 			goto repeat;
2172 		}
2173 
2174 		if (!propagate_mount_busy(mnt, 1)) {
2175 			list_move_tail(&mnt->mnt_expire, graveyard);
2176 			found++;
2177 		}
2178 	}
2179 	/*
2180 	 * All done at this level ... ascend and resume the search
2181 	 */
2182 	if (this_parent != parent) {
2183 		next = this_parent->mnt_child.next;
2184 		this_parent = this_parent->mnt_parent;
2185 		goto resume;
2186 	}
2187 	return found;
2188 }
2189 
2190 /*
2191  * process a list of expirable mountpoints with the intent of discarding any
2192  * submounts of a specific parent mountpoint
2193  *
2194  * vfsmount_lock must be held for write
2195  */
2196 static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts)
2197 {
2198 	LIST_HEAD(graveyard);
2199 	struct vfsmount *m;
2200 
2201 	/* extract submounts of 'mountpoint' from the expiration list */
2202 	while (select_submounts(mnt, &graveyard)) {
2203 		while (!list_empty(&graveyard)) {
2204 			m = list_first_entry(&graveyard, struct vfsmount,
2205 						mnt_expire);
2206 			touch_mnt_namespace(m->mnt_ns);
2207 			umount_tree(m, 1, umounts);
2208 		}
2209 	}
2210 }
2211 
2212 /*
2213  * Some copy_from_user() implementations do not return the exact number of
2214  * bytes remaining to copy on a fault.  But copy_mount_options() requires that.
2215  * Note that this function differs from copy_from_user() in that it will oops
2216  * on bad values of `to', rather than returning a short copy.
2217  */
2218 static long exact_copy_from_user(void *to, const void __user * from,
2219 				 unsigned long n)
2220 {
2221 	char *t = to;
2222 	const char __user *f = from;
2223 	char c;
2224 
2225 	if (!access_ok(VERIFY_READ, from, n))
2226 		return n;
2227 
2228 	while (n) {
2229 		if (__get_user(c, f)) {
2230 			memset(t, 0, n);
2231 			break;
2232 		}
2233 		*t++ = c;
2234 		f++;
2235 		n--;
2236 	}
2237 	return n;
2238 }
2239 
2240 int copy_mount_options(const void __user * data, unsigned long *where)
2241 {
2242 	int i;
2243 	unsigned long page;
2244 	unsigned long size;
2245 
2246 	*where = 0;
2247 	if (!data)
2248 		return 0;
2249 
2250 	if (!(page = __get_free_page(GFP_KERNEL)))
2251 		return -ENOMEM;
2252 
2253 	/* We only care that *some* data at the address the user
2254 	 * gave us is valid.  Just in case, we'll zero
2255 	 * the remainder of the page.
2256 	 */
2257 	/* copy_from_user cannot cross TASK_SIZE ! */
2258 	size = TASK_SIZE - (unsigned long)data;
2259 	if (size > PAGE_SIZE)
2260 		size = PAGE_SIZE;
2261 
2262 	i = size - exact_copy_from_user((void *)page, data, size);
2263 	if (!i) {
2264 		free_page(page);
2265 		return -EFAULT;
2266 	}
2267 	if (i != PAGE_SIZE)
2268 		memset((char *)page + i, 0, PAGE_SIZE - i);
2269 	*where = page;
2270 	return 0;
2271 }
2272 
2273 int copy_mount_string(const void __user *data, char **where)
2274 {
2275 	char *tmp;
2276 
2277 	if (!data) {
2278 		*where = NULL;
2279 		return 0;
2280 	}
2281 
2282 	tmp = strndup_user(data, PAGE_SIZE);
2283 	if (IS_ERR(tmp))
2284 		return PTR_ERR(tmp);
2285 
2286 	*where = tmp;
2287 	return 0;
2288 }
2289 
2290 /*
2291  * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2292  * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2293  *
2294  * data is a (void *) that can point to any structure up to
2295  * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2296  * information (or be NULL).
2297  *
2298  * Pre-0.97 versions of mount() didn't have a flags word.
2299  * When the flags word was introduced its top half was required
2300  * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2301  * Therefore, if this magic number is present, it carries no information
2302  * and must be discarded.
2303  */
2304 long do_mount(char *dev_name, char *dir_name, char *type_page,
2305 		  unsigned long flags, void *data_page)
2306 {
2307 	struct path path;
2308 	int retval = 0;
2309 	int mnt_flags = 0;
2310 
2311 	/* Discard magic */
2312 	if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2313 		flags &= ~MS_MGC_MSK;
2314 
2315 	/* Basic sanity checks */
2316 
2317 	if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2318 		return -EINVAL;
2319 
2320 	if (data_page)
2321 		((char *)data_page)[PAGE_SIZE - 1] = 0;
2322 
2323 	/* ... and get the mountpoint */
2324 	retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2325 	if (retval)
2326 		return retval;
2327 
2328 	retval = security_sb_mount(dev_name, &path,
2329 				   type_page, flags, data_page);
2330 	if (retval)
2331 		goto dput_out;
2332 
2333 	/* Default to relatime unless overriden */
2334 	if (!(flags & MS_NOATIME))
2335 		mnt_flags |= MNT_RELATIME;
2336 
2337 	/* Separate the per-mountpoint flags */
2338 	if (flags & MS_NOSUID)
2339 		mnt_flags |= MNT_NOSUID;
2340 	if (flags & MS_NODEV)
2341 		mnt_flags |= MNT_NODEV;
2342 	if (flags & MS_NOEXEC)
2343 		mnt_flags |= MNT_NOEXEC;
2344 	if (flags & MS_NOATIME)
2345 		mnt_flags |= MNT_NOATIME;
2346 	if (flags & MS_NODIRATIME)
2347 		mnt_flags |= MNT_NODIRATIME;
2348 	if (flags & MS_STRICTATIME)
2349 		mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2350 	if (flags & MS_RDONLY)
2351 		mnt_flags |= MNT_READONLY;
2352 
2353 	flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2354 		   MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2355 		   MS_STRICTATIME);
2356 
2357 	if (flags & MS_REMOUNT)
2358 		retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2359 				    data_page);
2360 	else if (flags & MS_BIND)
2361 		retval = do_loopback(&path, dev_name, flags & MS_REC);
2362 	else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2363 		retval = do_change_type(&path, flags);
2364 	else if (flags & MS_MOVE)
2365 		retval = do_move_mount(&path, dev_name);
2366 	else
2367 		retval = do_new_mount(&path, type_page, flags, mnt_flags,
2368 				      dev_name, data_page);
2369 dput_out:
2370 	path_put(&path);
2371 	return retval;
2372 }
2373 
2374 static struct mnt_namespace *alloc_mnt_ns(void)
2375 {
2376 	struct mnt_namespace *new_ns;
2377 
2378 	new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2379 	if (!new_ns)
2380 		return ERR_PTR(-ENOMEM);
2381 	atomic_set(&new_ns->count, 1);
2382 	new_ns->root = NULL;
2383 	INIT_LIST_HEAD(&new_ns->list);
2384 	init_waitqueue_head(&new_ns->poll);
2385 	new_ns->event = 0;
2386 	return new_ns;
2387 }
2388 
2389 void mnt_make_longterm(struct vfsmount *mnt)
2390 {
2391 	__mnt_make_longterm(mnt);
2392 }
2393 
2394 void mnt_make_shortterm(struct vfsmount *mnt)
2395 {
2396 #ifdef CONFIG_SMP
2397 	if (atomic_add_unless(&mnt->mnt_longterm, -1, 1))
2398 		return;
2399 	br_write_lock(vfsmount_lock);
2400 	atomic_dec(&mnt->mnt_longterm);
2401 	br_write_unlock(vfsmount_lock);
2402 #endif
2403 }
2404 
2405 /*
2406  * Allocate a new namespace structure and populate it with contents
2407  * copied from the namespace of the passed in task structure.
2408  */
2409 static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
2410 		struct fs_struct *fs)
2411 {
2412 	struct mnt_namespace *new_ns;
2413 	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2414 	struct vfsmount *p, *q;
2415 
2416 	new_ns = alloc_mnt_ns();
2417 	if (IS_ERR(new_ns))
2418 		return new_ns;
2419 
2420 	down_write(&namespace_sem);
2421 	/* First pass: copy the tree topology */
2422 	new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root,
2423 					CL_COPY_ALL | CL_EXPIRE);
2424 	if (!new_ns->root) {
2425 		up_write(&namespace_sem);
2426 		kfree(new_ns);
2427 		return ERR_PTR(-ENOMEM);
2428 	}
2429 	br_write_lock(vfsmount_lock);
2430 	list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
2431 	br_write_unlock(vfsmount_lock);
2432 
2433 	/*
2434 	 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2435 	 * as belonging to new namespace.  We have already acquired a private
2436 	 * fs_struct, so tsk->fs->lock is not needed.
2437 	 */
2438 	p = mnt_ns->root;
2439 	q = new_ns->root;
2440 	while (p) {
2441 		q->mnt_ns = new_ns;
2442 		__mnt_make_longterm(q);
2443 		if (fs) {
2444 			if (p == fs->root.mnt) {
2445 				fs->root.mnt = mntget(q);
2446 				__mnt_make_longterm(q);
2447 				mnt_make_shortterm(p);
2448 				rootmnt = p;
2449 			}
2450 			if (p == fs->pwd.mnt) {
2451 				fs->pwd.mnt = mntget(q);
2452 				__mnt_make_longterm(q);
2453 				mnt_make_shortterm(p);
2454 				pwdmnt = p;
2455 			}
2456 		}
2457 		p = next_mnt(p, mnt_ns->root);
2458 		q = next_mnt(q, new_ns->root);
2459 	}
2460 	up_write(&namespace_sem);
2461 
2462 	if (rootmnt)
2463 		mntput(rootmnt);
2464 	if (pwdmnt)
2465 		mntput(pwdmnt);
2466 
2467 	return new_ns;
2468 }
2469 
2470 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2471 		struct fs_struct *new_fs)
2472 {
2473 	struct mnt_namespace *new_ns;
2474 
2475 	BUG_ON(!ns);
2476 	get_mnt_ns(ns);
2477 
2478 	if (!(flags & CLONE_NEWNS))
2479 		return ns;
2480 
2481 	new_ns = dup_mnt_ns(ns, new_fs);
2482 
2483 	put_mnt_ns(ns);
2484 	return new_ns;
2485 }
2486 
2487 /**
2488  * create_mnt_ns - creates a private namespace and adds a root filesystem
2489  * @mnt: pointer to the new root filesystem mountpoint
2490  */
2491 struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
2492 {
2493 	struct mnt_namespace *new_ns;
2494 
2495 	new_ns = alloc_mnt_ns();
2496 	if (!IS_ERR(new_ns)) {
2497 		mnt->mnt_ns = new_ns;
2498 		__mnt_make_longterm(mnt);
2499 		new_ns->root = mnt;
2500 		list_add(&new_ns->list, &new_ns->root->mnt_list);
2501 	}
2502 	return new_ns;
2503 }
2504 EXPORT_SYMBOL(create_mnt_ns);
2505 
2506 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2507 		char __user *, type, unsigned long, flags, void __user *, data)
2508 {
2509 	int ret;
2510 	char *kernel_type;
2511 	char *kernel_dir;
2512 	char *kernel_dev;
2513 	unsigned long data_page;
2514 
2515 	ret = copy_mount_string(type, &kernel_type);
2516 	if (ret < 0)
2517 		goto out_type;
2518 
2519 	kernel_dir = getname(dir_name);
2520 	if (IS_ERR(kernel_dir)) {
2521 		ret = PTR_ERR(kernel_dir);
2522 		goto out_dir;
2523 	}
2524 
2525 	ret = copy_mount_string(dev_name, &kernel_dev);
2526 	if (ret < 0)
2527 		goto out_dev;
2528 
2529 	ret = copy_mount_options(data, &data_page);
2530 	if (ret < 0)
2531 		goto out_data;
2532 
2533 	ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags,
2534 		(void *) data_page);
2535 
2536 	free_page(data_page);
2537 out_data:
2538 	kfree(kernel_dev);
2539 out_dev:
2540 	putname(kernel_dir);
2541 out_dir:
2542 	kfree(kernel_type);
2543 out_type:
2544 	return ret;
2545 }
2546 
2547 /*
2548  * pivot_root Semantics:
2549  * Moves the root file system of the current process to the directory put_old,
2550  * makes new_root as the new root file system of the current process, and sets
2551  * root/cwd of all processes which had them on the current root to new_root.
2552  *
2553  * Restrictions:
2554  * The new_root and put_old must be directories, and  must not be on the
2555  * same file  system as the current process root. The put_old  must  be
2556  * underneath new_root,  i.e. adding a non-zero number of /.. to the string
2557  * pointed to by put_old must yield the same directory as new_root. No other
2558  * file system may be mounted on put_old. After all, new_root is a mountpoint.
2559  *
2560  * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2561  * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2562  * in this situation.
2563  *
2564  * Notes:
2565  *  - we don't move root/cwd if they are not at the root (reason: if something
2566  *    cared enough to change them, it's probably wrong to force them elsewhere)
2567  *  - it's okay to pick a root that isn't the root of a file system, e.g.
2568  *    /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2569  *    though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2570  *    first.
2571  */
2572 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2573 		const char __user *, put_old)
2574 {
2575 	struct vfsmount *tmp;
2576 	struct path new, old, parent_path, root_parent, root;
2577 	int error;
2578 
2579 	if (!capable(CAP_SYS_ADMIN))
2580 		return -EPERM;
2581 
2582 	error = user_path_dir(new_root, &new);
2583 	if (error)
2584 		goto out0;
2585 
2586 	error = user_path_dir(put_old, &old);
2587 	if (error)
2588 		goto out1;
2589 
2590 	error = security_sb_pivotroot(&old, &new);
2591 	if (error)
2592 		goto out2;
2593 
2594 	get_fs_root(current->fs, &root);
2595 	error = lock_mount(&old);
2596 	if (error)
2597 		goto out3;
2598 
2599 	error = -EINVAL;
2600 	if (IS_MNT_SHARED(old.mnt) ||
2601 		IS_MNT_SHARED(new.mnt->mnt_parent) ||
2602 		IS_MNT_SHARED(root.mnt->mnt_parent))
2603 		goto out4;
2604 	if (!check_mnt(root.mnt) || !check_mnt(new.mnt))
2605 		goto out4;
2606 	error = -ENOENT;
2607 	if (d_unlinked(new.dentry))
2608 		goto out4;
2609 	if (d_unlinked(old.dentry))
2610 		goto out4;
2611 	error = -EBUSY;
2612 	if (new.mnt == root.mnt ||
2613 	    old.mnt == root.mnt)
2614 		goto out4; /* loop, on the same file system  */
2615 	error = -EINVAL;
2616 	if (root.mnt->mnt_root != root.dentry)
2617 		goto out4; /* not a mountpoint */
2618 	if (root.mnt->mnt_parent == root.mnt)
2619 		goto out4; /* not attached */
2620 	if (new.mnt->mnt_root != new.dentry)
2621 		goto out4; /* not a mountpoint */
2622 	if (new.mnt->mnt_parent == new.mnt)
2623 		goto out4; /* not attached */
2624 	/* make sure we can reach put_old from new_root */
2625 	tmp = old.mnt;
2626 	if (tmp != new.mnt) {
2627 		for (;;) {
2628 			if (tmp->mnt_parent == tmp)
2629 				goto out4; /* already mounted on put_old */
2630 			if (tmp->mnt_parent == new.mnt)
2631 				break;
2632 			tmp = tmp->mnt_parent;
2633 		}
2634 		if (!is_subdir(tmp->mnt_mountpoint, new.dentry))
2635 			goto out4;
2636 	} else if (!is_subdir(old.dentry, new.dentry))
2637 		goto out4;
2638 	br_write_lock(vfsmount_lock);
2639 	detach_mnt(new.mnt, &parent_path);
2640 	detach_mnt(root.mnt, &root_parent);
2641 	/* mount old root on put_old */
2642 	attach_mnt(root.mnt, &old);
2643 	/* mount new_root on / */
2644 	attach_mnt(new.mnt, &root_parent);
2645 	touch_mnt_namespace(current->nsproxy->mnt_ns);
2646 	br_write_unlock(vfsmount_lock);
2647 	chroot_fs_refs(&root, &new);
2648 	error = 0;
2649 out4:
2650 	unlock_mount(&old);
2651 	if (!error) {
2652 		path_put(&root_parent);
2653 		path_put(&parent_path);
2654 	}
2655 out3:
2656 	path_put(&root);
2657 out2:
2658 	path_put(&old);
2659 out1:
2660 	path_put(&new);
2661 out0:
2662 	return error;
2663 }
2664 
2665 static void __init init_mount_tree(void)
2666 {
2667 	struct vfsmount *mnt;
2668 	struct mnt_namespace *ns;
2669 	struct path root;
2670 
2671 	mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
2672 	if (IS_ERR(mnt))
2673 		panic("Can't create rootfs");
2674 
2675 	ns = create_mnt_ns(mnt);
2676 	if (IS_ERR(ns))
2677 		panic("Can't allocate initial namespace");
2678 
2679 	init_task.nsproxy->mnt_ns = ns;
2680 	get_mnt_ns(ns);
2681 
2682 	root.mnt = ns->root;
2683 	root.dentry = ns->root->mnt_root;
2684 
2685 	set_fs_pwd(current->fs, &root);
2686 	set_fs_root(current->fs, &root);
2687 }
2688 
2689 void __init mnt_init(void)
2690 {
2691 	unsigned u;
2692 	int err;
2693 
2694 	init_rwsem(&namespace_sem);
2695 
2696 	mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
2697 			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2698 
2699 	mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2700 
2701 	if (!mount_hashtable)
2702 		panic("Failed to allocate mount hash table\n");
2703 
2704 	printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);
2705 
2706 	for (u = 0; u < HASH_SIZE; u++)
2707 		INIT_LIST_HEAD(&mount_hashtable[u]);
2708 
2709 	br_lock_init(vfsmount_lock);
2710 
2711 	err = sysfs_init();
2712 	if (err)
2713 		printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2714 			__func__, err);
2715 	fs_kobj = kobject_create_and_add("fs", NULL);
2716 	if (!fs_kobj)
2717 		printk(KERN_WARNING "%s: kobj create error\n", __func__);
2718 	init_rootfs();
2719 	init_mount_tree();
2720 }
2721 
2722 void put_mnt_ns(struct mnt_namespace *ns)
2723 {
2724 	LIST_HEAD(umount_list);
2725 
2726 	if (!atomic_dec_and_test(&ns->count))
2727 		return;
2728 	down_write(&namespace_sem);
2729 	br_write_lock(vfsmount_lock);
2730 	umount_tree(ns->root, 0, &umount_list);
2731 	br_write_unlock(vfsmount_lock);
2732 	up_write(&namespace_sem);
2733 	release_mounts(&umount_list);
2734 	kfree(ns);
2735 }
2736 EXPORT_SYMBOL(put_mnt_ns);
2737 
2738 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2739 {
2740 	return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2741 }
2742 EXPORT_SYMBOL_GPL(kern_mount_data);
2743