4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
11 #include <linux/syscalls.h>
12 #include <linux/export.h>
13 #include <linux/capability.h>
14 #include <linux/mnt_namespace.h>
15 #include <linux/user_namespace.h>
16 #include <linux/namei.h>
17 #include <linux/security.h>
18 #include <linux/idr.h>
19 #include <linux/acct.h> /* acct_auto_close_mnt */
20 #include <linux/ramfs.h> /* init_rootfs */
21 #include <linux/fs_struct.h> /* get_fs_root et.al. */
22 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
23 #include <linux/uaccess.h>
24 #include <linux/proc_fs.h>
28 #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
29 #define HASH_SIZE (1UL << HASH_SHIFT)
32 static DEFINE_IDA(mnt_id_ida);
33 static DEFINE_IDA(mnt_group_ida);
34 static DEFINE_SPINLOCK(mnt_id_lock);
35 static int mnt_id_start = 0;
36 static int mnt_group_start = 1;
38 static struct list_head *mount_hashtable __read_mostly;
39 static struct list_head *mountpoint_hashtable __read_mostly;
40 static struct kmem_cache *mnt_cache __read_mostly;
41 static struct rw_semaphore namespace_sem;
44 struct kobject *fs_kobj;
45 EXPORT_SYMBOL_GPL(fs_kobj);
48 * vfsmount lock may be taken for read to prevent changes to the
49 * vfsmount hash, ie. during mountpoint lookups or walking back
52 * It should be taken for write in all cases where the vfsmount
53 * tree or hash is modified or when a vfsmount structure is modified.
55 DEFINE_BRLOCK(vfsmount_lock);
57 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
59 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
60 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
61 tmp = tmp + (tmp >> HASH_SHIFT);
62 return tmp & (HASH_SIZE - 1);
65 #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
68 * allocation is serialized by namespace_sem, but we need the spinlock to
69 * serialize with freeing.
71 static int mnt_alloc_id(struct mount *mnt)
76 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
77 spin_lock(&mnt_id_lock);
78 res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
80 mnt_id_start = mnt->mnt_id + 1;
81 spin_unlock(&mnt_id_lock);
88 static void mnt_free_id(struct mount *mnt)
91 spin_lock(&mnt_id_lock);
92 ida_remove(&mnt_id_ida, id);
93 if (mnt_id_start > id)
95 spin_unlock(&mnt_id_lock);
99 * Allocate a new peer group ID
101 * mnt_group_ida is protected by namespace_sem
103 static int mnt_alloc_group_id(struct mount *mnt)
107 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
110 res = ida_get_new_above(&mnt_group_ida,
114 mnt_group_start = mnt->mnt_group_id + 1;
120 * Release a peer group ID
122 void mnt_release_group_id(struct mount *mnt)
124 int id = mnt->mnt_group_id;
125 ida_remove(&mnt_group_ida, id);
126 if (mnt_group_start > id)
127 mnt_group_start = id;
128 mnt->mnt_group_id = 0;
132 * vfsmount lock must be held for read
134 static inline void mnt_add_count(struct mount *mnt, int n)
137 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
146 * vfsmount lock must be held for write
148 unsigned int mnt_get_count(struct mount *mnt)
151 unsigned int count = 0;
154 for_each_possible_cpu(cpu) {
155 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
160 return mnt->mnt_count;
164 static struct mount *alloc_vfsmnt(const char *name)
166 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
170 err = mnt_alloc_id(mnt);
175 mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
176 if (!mnt->mnt_devname)
181 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
183 goto out_free_devname;
185 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
188 mnt->mnt_writers = 0;
191 INIT_LIST_HEAD(&mnt->mnt_hash);
192 INIT_LIST_HEAD(&mnt->mnt_child);
193 INIT_LIST_HEAD(&mnt->mnt_mounts);
194 INIT_LIST_HEAD(&mnt->mnt_list);
195 INIT_LIST_HEAD(&mnt->mnt_expire);
196 INIT_LIST_HEAD(&mnt->mnt_share);
197 INIT_LIST_HEAD(&mnt->mnt_slave_list);
198 INIT_LIST_HEAD(&mnt->mnt_slave);
199 #ifdef CONFIG_FSNOTIFY
200 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
207 kfree(mnt->mnt_devname);
212 kmem_cache_free(mnt_cache, mnt);
217 * Most r/o checks on a fs are for operations that take
218 * discrete amounts of time, like a write() or unlink().
219 * We must keep track of when those operations start
220 * (for permission checks) and when they end, so that
221 * we can determine when writes are able to occur to
225 * __mnt_is_readonly: check whether a mount is read-only
226 * @mnt: the mount to check for its write status
228 * This shouldn't be used directly ouside of the VFS.
229 * It does not guarantee that the filesystem will stay
230 * r/w, just that it is right *now*. This can not and
231 * should not be used in place of IS_RDONLY(inode).
232 * mnt_want/drop_write() will _keep_ the filesystem
235 int __mnt_is_readonly(struct vfsmount *mnt)
237 if (mnt->mnt_flags & MNT_READONLY)
239 if (mnt->mnt_sb->s_flags & MS_RDONLY)
243 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
245 static inline void mnt_inc_writers(struct mount *mnt)
248 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
254 static inline void mnt_dec_writers(struct mount *mnt)
257 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
263 static unsigned int mnt_get_writers(struct mount *mnt)
266 unsigned int count = 0;
269 for_each_possible_cpu(cpu) {
270 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
275 return mnt->mnt_writers;
279 static int mnt_is_readonly(struct vfsmount *mnt)
281 if (mnt->mnt_sb->s_readonly_remount)
283 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
285 return __mnt_is_readonly(mnt);
289 * Most r/o & frozen checks on a fs are for operations that take discrete
290 * amounts of time, like a write() or unlink(). We must keep track of when
291 * those operations start (for permission checks) and when they end, so that we
292 * can determine when writes are able to occur to a filesystem.
295 * __mnt_want_write - get write access to a mount without freeze protection
296 * @m: the mount on which to take a write
298 * This tells the low-level filesystem that a write is about to be performed to
299 * it, and makes sure that writes are allowed (mnt it read-write) before
300 * returning success. This operation does not protect against filesystem being
301 * frozen. When the write operation is finished, __mnt_drop_write() must be
302 * called. This is effectively a refcount.
304 int __mnt_want_write(struct vfsmount *m)
306 struct mount *mnt = real_mount(m);
310 mnt_inc_writers(mnt);
312 * The store to mnt_inc_writers must be visible before we pass
313 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
314 * incremented count after it has set MNT_WRITE_HOLD.
317 while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
320 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
321 * be set to match its requirements. So we must not load that until
322 * MNT_WRITE_HOLD is cleared.
325 if (mnt_is_readonly(m)) {
326 mnt_dec_writers(mnt);
335 * mnt_want_write - get write access to a mount
336 * @m: the mount on which to take a write
338 * This tells the low-level filesystem that a write is about to be performed to
339 * it, and makes sure that writes are allowed (mount is read-write, filesystem
340 * is not frozen) before returning success. When the write operation is
341 * finished, mnt_drop_write() must be called. This is effectively a refcount.
343 int mnt_want_write(struct vfsmount *m)
347 sb_start_write(m->mnt_sb);
348 ret = __mnt_want_write(m);
350 sb_end_write(m->mnt_sb);
353 EXPORT_SYMBOL_GPL(mnt_want_write);
356 * mnt_clone_write - get write access to a mount
357 * @mnt: the mount on which to take a write
359 * This is effectively like mnt_want_write, except
360 * it must only be used to take an extra write reference
361 * on a mountpoint that we already know has a write reference
362 * on it. This allows some optimisation.
364 * After finished, mnt_drop_write must be called as usual to
365 * drop the reference.
367 int mnt_clone_write(struct vfsmount *mnt)
369 /* superblock may be r/o */
370 if (__mnt_is_readonly(mnt))
373 mnt_inc_writers(real_mount(mnt));
377 EXPORT_SYMBOL_GPL(mnt_clone_write);
380 * __mnt_want_write_file - get write access to a file's mount
381 * @file: the file who's mount on which to take a write
383 * This is like __mnt_want_write, but it takes a file and can
384 * do some optimisations if the file is open for write already
386 int __mnt_want_write_file(struct file *file)
388 struct inode *inode = file_inode(file);
390 if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
391 return __mnt_want_write(file->f_path.mnt);
393 return mnt_clone_write(file->f_path.mnt);
397 * mnt_want_write_file - get write access to a file's mount
398 * @file: the file who's mount on which to take a write
400 * This is like mnt_want_write, but it takes a file and can
401 * do some optimisations if the file is open for write already
403 int mnt_want_write_file(struct file *file)
407 sb_start_write(file->f_path.mnt->mnt_sb);
408 ret = __mnt_want_write_file(file);
410 sb_end_write(file->f_path.mnt->mnt_sb);
413 EXPORT_SYMBOL_GPL(mnt_want_write_file);
416 * __mnt_drop_write - give up write access to a mount
417 * @mnt: the mount on which to give up write access
419 * Tells the low-level filesystem that we are done
420 * performing writes to it. Must be matched with
421 * __mnt_want_write() call above.
423 void __mnt_drop_write(struct vfsmount *mnt)
426 mnt_dec_writers(real_mount(mnt));
431 * mnt_drop_write - give up write access to a mount
432 * @mnt: the mount on which to give up write access
434 * Tells the low-level filesystem that we are done performing writes to it and
435 * also allows filesystem to be frozen again. Must be matched with
436 * mnt_want_write() call above.
438 void mnt_drop_write(struct vfsmount *mnt)
440 __mnt_drop_write(mnt);
441 sb_end_write(mnt->mnt_sb);
443 EXPORT_SYMBOL_GPL(mnt_drop_write);
445 void __mnt_drop_write_file(struct file *file)
447 __mnt_drop_write(file->f_path.mnt);
450 void mnt_drop_write_file(struct file *file)
452 mnt_drop_write(file->f_path.mnt);
454 EXPORT_SYMBOL(mnt_drop_write_file);
456 static int mnt_make_readonly(struct mount *mnt)
460 br_write_lock(&vfsmount_lock);
461 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
463 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
464 * should be visible before we do.
469 * With writers on hold, if this value is zero, then there are
470 * definitely no active writers (although held writers may subsequently
471 * increment the count, they'll have to wait, and decrement it after
472 * seeing MNT_READONLY).
474 * It is OK to have counter incremented on one CPU and decremented on
475 * another: the sum will add up correctly. The danger would be when we
476 * sum up each counter, if we read a counter before it is incremented,
477 * but then read another CPU's count which it has been subsequently
478 * decremented from -- we would see more decrements than we should.
479 * MNT_WRITE_HOLD protects against this scenario, because
480 * mnt_want_write first increments count, then smp_mb, then spins on
481 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
482 * we're counting up here.
484 if (mnt_get_writers(mnt) > 0)
487 mnt->mnt.mnt_flags |= MNT_READONLY;
489 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
490 * that become unheld will see MNT_READONLY.
493 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
494 br_write_unlock(&vfsmount_lock);
498 static void __mnt_unmake_readonly(struct mount *mnt)
500 br_write_lock(&vfsmount_lock);
501 mnt->mnt.mnt_flags &= ~MNT_READONLY;
502 br_write_unlock(&vfsmount_lock);
505 int sb_prepare_remount_readonly(struct super_block *sb)
510 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
511 if (atomic_long_read(&sb->s_remove_count))
514 br_write_lock(&vfsmount_lock);
515 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
516 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
517 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
519 if (mnt_get_writers(mnt) > 0) {
525 if (!err && atomic_long_read(&sb->s_remove_count))
529 sb->s_readonly_remount = 1;
532 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
533 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
534 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
536 br_write_unlock(&vfsmount_lock);
541 static void free_vfsmnt(struct mount *mnt)
543 kfree(mnt->mnt_devname);
546 free_percpu(mnt->mnt_pcp);
548 kmem_cache_free(mnt_cache, mnt);
552 * find the first or last mount at @dentry on vfsmount @mnt depending on
553 * @dir. If @dir is set return the first mount else return the last mount.
554 * vfsmount_lock must be held for read or write.
556 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
559 struct list_head *head = mount_hashtable + hash(mnt, dentry);
560 struct list_head *tmp = head;
561 struct mount *p, *found = NULL;
564 tmp = dir ? tmp->next : tmp->prev;
568 p = list_entry(tmp, struct mount, mnt_hash);
569 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) {
578 * lookup_mnt - Return the first child mount mounted at path
580 * "First" means first mounted chronologically. If you create the
583 * mount /dev/sda1 /mnt
584 * mount /dev/sda2 /mnt
585 * mount /dev/sda3 /mnt
587 * Then lookup_mnt() on the base /mnt dentry in the root mount will
588 * return successively the root dentry and vfsmount of /dev/sda1, then
589 * /dev/sda2, then /dev/sda3, then NULL.
591 * lookup_mnt takes a reference to the found vfsmount.
593 struct vfsmount *lookup_mnt(struct path *path)
595 struct mount *child_mnt;
597 br_read_lock(&vfsmount_lock);
598 child_mnt = __lookup_mnt(path->mnt, path->dentry, 1);
600 mnt_add_count(child_mnt, 1);
601 br_read_unlock(&vfsmount_lock);
602 return &child_mnt->mnt;
604 br_read_unlock(&vfsmount_lock);
609 static struct mountpoint *new_mountpoint(struct dentry *dentry)
611 struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry);
612 struct mountpoint *mp;
614 list_for_each_entry(mp, chain, m_hash) {
615 if (mp->m_dentry == dentry) {
616 /* might be worth a WARN_ON() */
617 if (d_unlinked(dentry))
618 return ERR_PTR(-ENOENT);
624 mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
626 return ERR_PTR(-ENOMEM);
628 spin_lock(&dentry->d_lock);
629 if (d_unlinked(dentry)) {
630 spin_unlock(&dentry->d_lock);
632 return ERR_PTR(-ENOENT);
634 dentry->d_flags |= DCACHE_MOUNTED;
635 spin_unlock(&dentry->d_lock);
636 mp->m_dentry = dentry;
638 list_add(&mp->m_hash, chain);
642 static void put_mountpoint(struct mountpoint *mp)
644 if (!--mp->m_count) {
645 struct dentry *dentry = mp->m_dentry;
646 spin_lock(&dentry->d_lock);
647 dentry->d_flags &= ~DCACHE_MOUNTED;
648 spin_unlock(&dentry->d_lock);
649 list_del(&mp->m_hash);
654 static inline int check_mnt(struct mount *mnt)
656 return mnt->mnt_ns == current->nsproxy->mnt_ns;
660 * vfsmount lock must be held for write
662 static void touch_mnt_namespace(struct mnt_namespace *ns)
666 wake_up_interruptible(&ns->poll);
671 * vfsmount lock must be held for write
673 static void __touch_mnt_namespace(struct mnt_namespace *ns)
675 if (ns && ns->event != event) {
677 wake_up_interruptible(&ns->poll);
682 * vfsmount lock must be held for write
684 static void detach_mnt(struct mount *mnt, struct path *old_path)
686 old_path->dentry = mnt->mnt_mountpoint;
687 old_path->mnt = &mnt->mnt_parent->mnt;
688 mnt->mnt_parent = mnt;
689 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
690 list_del_init(&mnt->mnt_child);
691 list_del_init(&mnt->mnt_hash);
692 put_mountpoint(mnt->mnt_mp);
697 * vfsmount lock must be held for write
699 void mnt_set_mountpoint(struct mount *mnt,
700 struct mountpoint *mp,
701 struct mount *child_mnt)
704 mnt_add_count(mnt, 1); /* essentially, that's mntget */
705 child_mnt->mnt_mountpoint = dget(mp->m_dentry);
706 child_mnt->mnt_parent = mnt;
707 child_mnt->mnt_mp = mp;
711 * vfsmount lock must be held for write
713 static void attach_mnt(struct mount *mnt,
714 struct mount *parent,
715 struct mountpoint *mp)
717 mnt_set_mountpoint(parent, mp, mnt);
718 list_add_tail(&mnt->mnt_hash, mount_hashtable +
719 hash(&parent->mnt, mp->m_dentry));
720 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
724 * vfsmount lock must be held for write
726 static void commit_tree(struct mount *mnt)
728 struct mount *parent = mnt->mnt_parent;
731 struct mnt_namespace *n = parent->mnt_ns;
733 BUG_ON(parent == mnt);
735 list_add_tail(&head, &mnt->mnt_list);
736 list_for_each_entry(m, &head, mnt_list)
739 list_splice(&head, n->list.prev);
741 list_add_tail(&mnt->mnt_hash, mount_hashtable +
742 hash(&parent->mnt, mnt->mnt_mountpoint));
743 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
744 touch_mnt_namespace(n);
747 static struct mount *next_mnt(struct mount *p, struct mount *root)
749 struct list_head *next = p->mnt_mounts.next;
750 if (next == &p->mnt_mounts) {
754 next = p->mnt_child.next;
755 if (next != &p->mnt_parent->mnt_mounts)
760 return list_entry(next, struct mount, mnt_child);
763 static struct mount *skip_mnt_tree(struct mount *p)
765 struct list_head *prev = p->mnt_mounts.prev;
766 while (prev != &p->mnt_mounts) {
767 p = list_entry(prev, struct mount, mnt_child);
768 prev = p->mnt_mounts.prev;
774 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
780 return ERR_PTR(-ENODEV);
782 mnt = alloc_vfsmnt(name);
784 return ERR_PTR(-ENOMEM);
786 if (flags & MS_KERNMOUNT)
787 mnt->mnt.mnt_flags = MNT_INTERNAL;
789 root = mount_fs(type, flags, name, data);
792 return ERR_CAST(root);
795 mnt->mnt.mnt_root = root;
796 mnt->mnt.mnt_sb = root->d_sb;
797 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
798 mnt->mnt_parent = mnt;
799 br_write_lock(&vfsmount_lock);
800 list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
801 br_write_unlock(&vfsmount_lock);
804 EXPORT_SYMBOL_GPL(vfs_kern_mount);
806 static struct mount *clone_mnt(struct mount *old, struct dentry *root,
809 struct super_block *sb = old->mnt.mnt_sb;
813 mnt = alloc_vfsmnt(old->mnt_devname);
815 return ERR_PTR(-ENOMEM);
817 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
818 mnt->mnt_group_id = 0; /* not a peer of original */
820 mnt->mnt_group_id = old->mnt_group_id;
822 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
823 err = mnt_alloc_group_id(mnt);
828 mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
829 atomic_inc(&sb->s_active);
830 mnt->mnt.mnt_sb = sb;
831 mnt->mnt.mnt_root = dget(root);
832 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
833 mnt->mnt_parent = mnt;
834 br_write_lock(&vfsmount_lock);
835 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
836 br_write_unlock(&vfsmount_lock);
838 if ((flag & CL_SLAVE) ||
839 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
840 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
841 mnt->mnt_master = old;
842 CLEAR_MNT_SHARED(mnt);
843 } else if (!(flag & CL_PRIVATE)) {
844 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
845 list_add(&mnt->mnt_share, &old->mnt_share);
846 if (IS_MNT_SLAVE(old))
847 list_add(&mnt->mnt_slave, &old->mnt_slave);
848 mnt->mnt_master = old->mnt_master;
850 if (flag & CL_MAKE_SHARED)
853 /* stick the duplicate mount on the same expiry list
854 * as the original if that was on one */
855 if (flag & CL_EXPIRE) {
856 if (!list_empty(&old->mnt_expire))
857 list_add(&mnt->mnt_expire, &old->mnt_expire);
867 static inline void mntfree(struct mount *mnt)
869 struct vfsmount *m = &mnt->mnt;
870 struct super_block *sb = m->mnt_sb;
873 * This probably indicates that somebody messed
874 * up a mnt_want/drop_write() pair. If this
875 * happens, the filesystem was probably unable
876 * to make r/w->r/o transitions.
879 * The locking used to deal with mnt_count decrement provides barriers,
880 * so mnt_get_writers() below is safe.
882 WARN_ON(mnt_get_writers(mnt));
883 fsnotify_vfsmount_delete(m);
886 deactivate_super(sb);
889 static void mntput_no_expire(struct mount *mnt)
893 br_read_lock(&vfsmount_lock);
894 if (likely(mnt->mnt_ns)) {
895 /* shouldn't be the last one */
896 mnt_add_count(mnt, -1);
897 br_read_unlock(&vfsmount_lock);
900 br_read_unlock(&vfsmount_lock);
902 br_write_lock(&vfsmount_lock);
903 mnt_add_count(mnt, -1);
904 if (mnt_get_count(mnt)) {
905 br_write_unlock(&vfsmount_lock);
909 mnt_add_count(mnt, -1);
910 if (likely(mnt_get_count(mnt)))
912 br_write_lock(&vfsmount_lock);
914 if (unlikely(mnt->mnt_pinned)) {
915 mnt_add_count(mnt, mnt->mnt_pinned + 1);
917 br_write_unlock(&vfsmount_lock);
918 acct_auto_close_mnt(&mnt->mnt);
922 list_del(&mnt->mnt_instance);
923 br_write_unlock(&vfsmount_lock);
927 void mntput(struct vfsmount *mnt)
930 struct mount *m = real_mount(mnt);
931 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
932 if (unlikely(m->mnt_expiry_mark))
933 m->mnt_expiry_mark = 0;
937 EXPORT_SYMBOL(mntput);
939 struct vfsmount *mntget(struct vfsmount *mnt)
942 mnt_add_count(real_mount(mnt), 1);
945 EXPORT_SYMBOL(mntget);
947 void mnt_pin(struct vfsmount *mnt)
949 br_write_lock(&vfsmount_lock);
950 real_mount(mnt)->mnt_pinned++;
951 br_write_unlock(&vfsmount_lock);
953 EXPORT_SYMBOL(mnt_pin);
955 void mnt_unpin(struct vfsmount *m)
957 struct mount *mnt = real_mount(m);
958 br_write_lock(&vfsmount_lock);
959 if (mnt->mnt_pinned) {
960 mnt_add_count(mnt, 1);
963 br_write_unlock(&vfsmount_lock);
965 EXPORT_SYMBOL(mnt_unpin);
967 static inline void mangle(struct seq_file *m, const char *s)
969 seq_escape(m, s, " \t\n\\");
973 * Simple .show_options callback for filesystems which don't want to
974 * implement more complex mount option showing.
976 * See also save_mount_options().
978 int generic_show_options(struct seq_file *m, struct dentry *root)
983 options = rcu_dereference(root->d_sb->s_options);
985 if (options != NULL && options[0]) {
993 EXPORT_SYMBOL(generic_show_options);
996 * If filesystem uses generic_show_options(), this function should be
997 * called from the fill_super() callback.
999 * The .remount_fs callback usually needs to be handled in a special
1000 * way, to make sure, that previous options are not overwritten if the
1003 * Also note, that if the filesystem's .remount_fs function doesn't
1004 * reset all options to their default value, but changes only newly
1005 * given options, then the displayed options will not reflect reality
1008 void save_mount_options(struct super_block *sb, char *options)
1010 BUG_ON(sb->s_options);
1011 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
1013 EXPORT_SYMBOL(save_mount_options);
1015 void replace_mount_options(struct super_block *sb, char *options)
1017 char *old = sb->s_options;
1018 rcu_assign_pointer(sb->s_options, options);
1024 EXPORT_SYMBOL(replace_mount_options);
1026 #ifdef CONFIG_PROC_FS
1027 /* iterator; we want it to have access to namespace_sem, thus here... */
1028 static void *m_start(struct seq_file *m, loff_t *pos)
1030 struct proc_mounts *p = proc_mounts(m);
1032 down_read(&namespace_sem);
1033 return seq_list_start(&p->ns->list, *pos);
1036 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1038 struct proc_mounts *p = proc_mounts(m);
1040 return seq_list_next(v, &p->ns->list, pos);
1043 static void m_stop(struct seq_file *m, void *v)
1045 up_read(&namespace_sem);
1048 static int m_show(struct seq_file *m, void *v)
1050 struct proc_mounts *p = proc_mounts(m);
1051 struct mount *r = list_entry(v, struct mount, mnt_list);
1052 return p->show(m, &r->mnt);
1055 const struct seq_operations mounts_op = {
1061 #endif /* CONFIG_PROC_FS */
1064 * may_umount_tree - check if a mount tree is busy
1065 * @mnt: root of mount tree
1067 * This is called to check if a tree of mounts has any
1068 * open files, pwds, chroots or sub mounts that are
1071 int may_umount_tree(struct vfsmount *m)
1073 struct mount *mnt = real_mount(m);
1074 int actual_refs = 0;
1075 int minimum_refs = 0;
1079 /* write lock needed for mnt_get_count */
1080 br_write_lock(&vfsmount_lock);
1081 for (p = mnt; p; p = next_mnt(p, mnt)) {
1082 actual_refs += mnt_get_count(p);
1085 br_write_unlock(&vfsmount_lock);
1087 if (actual_refs > minimum_refs)
1093 EXPORT_SYMBOL(may_umount_tree);
1096 * may_umount - check if a mount point is busy
1097 * @mnt: root of mount
1099 * This is called to check if a mount point has any
1100 * open files, pwds, chroots or sub mounts. If the
1101 * mount has sub mounts this will return busy
1102 * regardless of whether the sub mounts are busy.
1104 * Doesn't take quota and stuff into account. IOW, in some cases it will
1105 * give false negatives. The main reason why it's here is that we need
1106 * a non-destructive way to look for easily umountable filesystems.
1108 int may_umount(struct vfsmount *mnt)
1111 down_read(&namespace_sem);
1112 br_write_lock(&vfsmount_lock);
1113 if (propagate_mount_busy(real_mount(mnt), 2))
1115 br_write_unlock(&vfsmount_lock);
1116 up_read(&namespace_sem);
1120 EXPORT_SYMBOL(may_umount);
1122 static LIST_HEAD(unmounted); /* protected by namespace_sem */
1124 static void release_mounts(struct list_head *head)
1127 while (!list_empty(head)) {
1128 mnt = list_first_entry(head, struct mount, mnt_hash);
1129 list_del_init(&mnt->mnt_hash);
1130 if (mnt_has_parent(mnt)) {
1131 struct dentry *dentry;
1134 br_write_lock(&vfsmount_lock);
1135 dentry = mnt->mnt_mountpoint;
1136 m = mnt->mnt_parent;
1137 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1138 mnt->mnt_parent = mnt;
1140 br_write_unlock(&vfsmount_lock);
1148 static void namespace_unlock(void)
1151 list_splice_init(&unmounted, &head);
1152 up_write(&namespace_sem);
1153 release_mounts(&head);
1157 * vfsmount lock must be held for write
1158 * namespace_sem must be held for write
1160 void umount_tree(struct mount *mnt, int propagate)
1162 LIST_HEAD(tmp_list);
1165 for (p = mnt; p; p = next_mnt(p, mnt))
1166 list_move(&p->mnt_hash, &tmp_list);
1169 propagate_umount(&tmp_list);
1171 list_for_each_entry(p, &tmp_list, mnt_hash) {
1172 list_del_init(&p->mnt_expire);
1173 list_del_init(&p->mnt_list);
1174 __touch_mnt_namespace(p->mnt_ns);
1176 list_del_init(&p->mnt_child);
1177 if (mnt_has_parent(p)) {
1178 p->mnt_parent->mnt_ghosts++;
1179 put_mountpoint(p->mnt_mp);
1182 change_mnt_propagation(p, MS_PRIVATE);
1184 list_splice(&tmp_list, &unmounted);
1187 static void shrink_submounts(struct mount *mnt);
1189 static int do_umount(struct mount *mnt, int flags)
1191 struct super_block *sb = mnt->mnt.mnt_sb;
1194 retval = security_sb_umount(&mnt->mnt, flags);
1199 * Allow userspace to request a mountpoint be expired rather than
1200 * unmounting unconditionally. Unmount only happens if:
1201 * (1) the mark is already set (the mark is cleared by mntput())
1202 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1204 if (flags & MNT_EXPIRE) {
1205 if (&mnt->mnt == current->fs->root.mnt ||
1206 flags & (MNT_FORCE | MNT_DETACH))
1210 * probably don't strictly need the lock here if we examined
1211 * all race cases, but it's a slowpath.
1213 br_write_lock(&vfsmount_lock);
1214 if (mnt_get_count(mnt) != 2) {
1215 br_write_unlock(&vfsmount_lock);
1218 br_write_unlock(&vfsmount_lock);
1220 if (!xchg(&mnt->mnt_expiry_mark, 1))
1225 * If we may have to abort operations to get out of this
1226 * mount, and they will themselves hold resources we must
1227 * allow the fs to do things. In the Unix tradition of
1228 * 'Gee thats tricky lets do it in userspace' the umount_begin
1229 * might fail to complete on the first run through as other tasks
1230 * must return, and the like. Thats for the mount program to worry
1231 * about for the moment.
1234 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1235 sb->s_op->umount_begin(sb);
1239 * No sense to grab the lock for this test, but test itself looks
1240 * somewhat bogus. Suggestions for better replacement?
1241 * Ho-hum... In principle, we might treat that as umount + switch
1242 * to rootfs. GC would eventually take care of the old vfsmount.
1243 * Actually it makes sense, especially if rootfs would contain a
1244 * /reboot - static binary that would close all descriptors and
1245 * call reboot(9). Then init(8) could umount root and exec /reboot.
1247 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1249 * Special case for "unmounting" root ...
1250 * we just try to remount it readonly.
1252 down_write(&sb->s_umount);
1253 if (!(sb->s_flags & MS_RDONLY))
1254 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1255 up_write(&sb->s_umount);
1259 down_write(&namespace_sem);
1260 br_write_lock(&vfsmount_lock);
1263 if (!(flags & MNT_DETACH))
1264 shrink_submounts(mnt);
1267 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
1268 if (!list_empty(&mnt->mnt_list))
1269 umount_tree(mnt, 1);
1272 br_write_unlock(&vfsmount_lock);
1278 * Is the caller allowed to modify his namespace?
1280 static inline bool may_mount(void)
1282 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1286 * Now umount can handle mount points as well as block devices.
1287 * This is important for filesystems which use unnamed block devices.
1289 * We now support a flag for forced unmount like the other 'big iron'
1290 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1293 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1298 int lookup_flags = 0;
1300 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1306 if (!(flags & UMOUNT_NOFOLLOW))
1307 lookup_flags |= LOOKUP_FOLLOW;
1309 retval = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1312 mnt = real_mount(path.mnt);
1314 if (path.dentry != path.mnt->mnt_root)
1316 if (!check_mnt(mnt))
1319 retval = do_umount(mnt, flags);
1321 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1323 mntput_no_expire(mnt);
1328 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1331 * The 2.0 compatible umount. No flags.
1333 SYSCALL_DEFINE1(oldumount, char __user *, name)
1335 return sys_umount(name, 0);
1340 static bool mnt_ns_loop(struct path *path)
1342 /* Could bind mounting the mount namespace inode cause a
1343 * mount namespace loop?
1345 struct inode *inode = path->dentry->d_inode;
1346 struct proc_inode *ei;
1347 struct mnt_namespace *mnt_ns;
1349 if (!proc_ns_inode(inode))
1353 if (ei->ns_ops != &mntns_operations)
1357 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1360 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1363 struct mount *res, *p, *q, *r, *parent;
1365 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
1366 return ERR_PTR(-EINVAL);
1368 res = q = clone_mnt(mnt, dentry, flag);
1372 q->mnt_mountpoint = mnt->mnt_mountpoint;
1375 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1377 if (!is_subdir(r->mnt_mountpoint, dentry))
1380 for (s = r; s; s = next_mnt(s, r)) {
1381 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
1382 s = skip_mnt_tree(s);
1385 while (p != s->mnt_parent) {
1391 q = clone_mnt(p, p->mnt.mnt_root, flag);
1394 br_write_lock(&vfsmount_lock);
1395 list_add_tail(&q->mnt_list, &res->mnt_list);
1396 attach_mnt(q, parent, p->mnt_mp);
1397 br_write_unlock(&vfsmount_lock);
1403 br_write_lock(&vfsmount_lock);
1404 umount_tree(res, 0);
1405 br_write_unlock(&vfsmount_lock);
1410 /* Caller should check returned pointer for errors */
1412 struct vfsmount *collect_mounts(struct path *path)
1415 down_write(&namespace_sem);
1416 tree = copy_tree(real_mount(path->mnt), path->dentry,
1417 CL_COPY_ALL | CL_PRIVATE);
1424 void drop_collected_mounts(struct vfsmount *mnt)
1426 down_write(&namespace_sem);
1427 br_write_lock(&vfsmount_lock);
1428 umount_tree(real_mount(mnt), 0);
1429 br_write_unlock(&vfsmount_lock);
1433 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1434 struct vfsmount *root)
1437 int res = f(root, arg);
1440 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1441 res = f(&mnt->mnt, arg);
1448 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1452 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1453 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1454 mnt_release_group_id(p);
1458 static int invent_group_ids(struct mount *mnt, bool recurse)
1462 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1463 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1464 int err = mnt_alloc_group_id(p);
1466 cleanup_group_ids(mnt, p);
1476 * @source_mnt : mount tree to be attached
1477 * @nd : place the mount tree @source_mnt is attached
1478 * @parent_nd : if non-null, detach the source_mnt from its parent and
1479 * store the parent mount and mountpoint dentry.
1480 * (done when source_mnt is moved)
1482 * NOTE: in the table below explains the semantics when a source mount
1483 * of a given type is attached to a destination mount of a given type.
1484 * ---------------------------------------------------------------------------
1485 * | BIND MOUNT OPERATION |
1486 * |**************************************************************************
1487 * | source-->| shared | private | slave | unbindable |
1491 * |**************************************************************************
1492 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1494 * |non-shared| shared (+) | private | slave (*) | invalid |
1495 * ***************************************************************************
1496 * A bind operation clones the source mount and mounts the clone on the
1497 * destination mount.
1499 * (++) the cloned mount is propagated to all the mounts in the propagation
1500 * tree of the destination mount and the cloned mount is added to
1501 * the peer group of the source mount.
1502 * (+) the cloned mount is created under the destination mount and is marked
1503 * as shared. The cloned mount is added to the peer group of the source
1505 * (+++) the mount is propagated to all the mounts in the propagation tree
1506 * of the destination mount and the cloned mount is made slave
1507 * of the same master as that of the source mount. The cloned mount
1508 * is marked as 'shared and slave'.
1509 * (*) the cloned mount is made a slave of the same master as that of the
1512 * ---------------------------------------------------------------------------
1513 * | MOVE MOUNT OPERATION |
1514 * |**************************************************************************
1515 * | source-->| shared | private | slave | unbindable |
1519 * |**************************************************************************
1520 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1522 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1523 * ***************************************************************************
1525 * (+) the mount is moved to the destination. And is then propagated to
1526 * all the mounts in the propagation tree of the destination mount.
1527 * (+*) the mount is moved to the destination.
1528 * (+++) the mount is moved to the destination and is then propagated to
1529 * all the mounts belonging to the destination mount's propagation tree.
1530 * the mount is marked as 'shared and slave'.
1531 * (*) the mount continues to be a slave at the new location.
1533 * if the source mount is a tree, the operations explained above is
1534 * applied to each mount in the tree.
1535 * Must be called without spinlocks held, since this function can sleep
1538 static int attach_recursive_mnt(struct mount *source_mnt,
1539 struct mount *dest_mnt,
1540 struct mountpoint *dest_mp,
1541 struct path *parent_path)
1543 LIST_HEAD(tree_list);
1544 struct mount *child, *p;
1547 if (IS_MNT_SHARED(dest_mnt)) {
1548 err = invent_group_ids(source_mnt, true);
1552 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
1554 goto out_cleanup_ids;
1556 br_write_lock(&vfsmount_lock);
1558 if (IS_MNT_SHARED(dest_mnt)) {
1559 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1563 detach_mnt(source_mnt, parent_path);
1564 attach_mnt(source_mnt, dest_mnt, dest_mp);
1565 touch_mnt_namespace(source_mnt->mnt_ns);
1567 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
1568 commit_tree(source_mnt);
1571 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
1572 list_del_init(&child->mnt_hash);
1575 br_write_unlock(&vfsmount_lock);
1580 if (IS_MNT_SHARED(dest_mnt))
1581 cleanup_group_ids(source_mnt, NULL);
1586 static struct mountpoint *lock_mount(struct path *path)
1588 struct vfsmount *mnt;
1589 struct dentry *dentry = path->dentry;
1591 mutex_lock(&dentry->d_inode->i_mutex);
1592 if (unlikely(cant_mount(dentry))) {
1593 mutex_unlock(&dentry->d_inode->i_mutex);
1594 return ERR_PTR(-ENOENT);
1596 down_write(&namespace_sem);
1597 mnt = lookup_mnt(path);
1599 struct mountpoint *mp = new_mountpoint(dentry);
1601 up_write(&namespace_sem);
1602 mutex_unlock(&dentry->d_inode->i_mutex);
1607 up_write(&namespace_sem);
1608 mutex_unlock(&path->dentry->d_inode->i_mutex);
1611 dentry = path->dentry = dget(mnt->mnt_root);
1615 static void unlock_mount(struct mountpoint *where)
1617 struct dentry *dentry = where->m_dentry;
1618 put_mountpoint(where);
1620 mutex_unlock(&dentry->d_inode->i_mutex);
1623 static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
1625 if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
1628 if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
1629 S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
1632 return attach_recursive_mnt(mnt, p, mp, NULL);
1636 * Sanity check the flags to change_mnt_propagation.
1639 static int flags_to_propagation_type(int flags)
1641 int type = flags & ~(MS_REC | MS_SILENT);
1643 /* Fail if any non-propagation flags are set */
1644 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1646 /* Only one propagation flag should be set */
1647 if (!is_power_of_2(type))
1653 * recursively change the type of the mountpoint.
1655 static int do_change_type(struct path *path, int flag)
1658 struct mount *mnt = real_mount(path->mnt);
1659 int recurse = flag & MS_REC;
1663 if (path->dentry != path->mnt->mnt_root)
1666 type = flags_to_propagation_type(flag);
1670 down_write(&namespace_sem);
1671 if (type == MS_SHARED) {
1672 err = invent_group_ids(mnt, recurse);
1677 br_write_lock(&vfsmount_lock);
1678 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1679 change_mnt_propagation(m, type);
1680 br_write_unlock(&vfsmount_lock);
1683 up_write(&namespace_sem);
1688 * do loopback mount.
1690 static int do_loopback(struct path *path, const char *old_name,
1693 struct path old_path;
1694 struct mount *mnt = NULL, *old, *parent;
1695 struct mountpoint *mp;
1697 if (!old_name || !*old_name)
1699 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1704 if (mnt_ns_loop(&old_path))
1707 mp = lock_mount(path);
1712 old = real_mount(old_path.mnt);
1713 parent = real_mount(path->mnt);
1716 if (IS_MNT_UNBINDABLE(old))
1719 if (!check_mnt(parent) || !check_mnt(old))
1723 mnt = copy_tree(old, old_path.dentry, 0);
1725 mnt = clone_mnt(old, old_path.dentry, 0);
1732 err = graft_tree(mnt, parent, mp);
1734 br_write_lock(&vfsmount_lock);
1735 umount_tree(mnt, 0);
1736 br_write_unlock(&vfsmount_lock);
1741 path_put(&old_path);
1745 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1748 int readonly_request = 0;
1750 if (ms_flags & MS_RDONLY)
1751 readonly_request = 1;
1752 if (readonly_request == __mnt_is_readonly(mnt))
1755 if (readonly_request)
1756 error = mnt_make_readonly(real_mount(mnt));
1758 __mnt_unmake_readonly(real_mount(mnt));
1763 * change filesystem flags. dir should be a physical root of filesystem.
1764 * If you've mounted a non-root directory somewhere and want to do remount
1765 * on it - tough luck.
1767 static int do_remount(struct path *path, int flags, int mnt_flags,
1771 struct super_block *sb = path->mnt->mnt_sb;
1772 struct mount *mnt = real_mount(path->mnt);
1774 if (!check_mnt(mnt))
1777 if (path->dentry != path->mnt->mnt_root)
1780 err = security_sb_remount(sb, data);
1784 down_write(&sb->s_umount);
1785 if (flags & MS_BIND)
1786 err = change_mount_flags(path->mnt, flags);
1787 else if (!capable(CAP_SYS_ADMIN))
1790 err = do_remount_sb(sb, flags, data, 0);
1792 br_write_lock(&vfsmount_lock);
1793 mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
1794 mnt->mnt.mnt_flags = mnt_flags;
1795 br_write_unlock(&vfsmount_lock);
1797 up_write(&sb->s_umount);
1799 br_write_lock(&vfsmount_lock);
1800 touch_mnt_namespace(mnt->mnt_ns);
1801 br_write_unlock(&vfsmount_lock);
1806 static inline int tree_contains_unbindable(struct mount *mnt)
1809 for (p = mnt; p; p = next_mnt(p, mnt)) {
1810 if (IS_MNT_UNBINDABLE(p))
1816 static int do_move_mount(struct path *path, const char *old_name)
1818 struct path old_path, parent_path;
1821 struct mountpoint *mp;
1823 if (!old_name || !*old_name)
1825 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1829 mp = lock_mount(path);
1834 old = real_mount(old_path.mnt);
1835 p = real_mount(path->mnt);
1838 if (!check_mnt(p) || !check_mnt(old))
1842 if (old_path.dentry != old_path.mnt->mnt_root)
1845 if (!mnt_has_parent(old))
1848 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1849 S_ISDIR(old_path.dentry->d_inode->i_mode))
1852 * Don't move a mount residing in a shared parent.
1854 if (IS_MNT_SHARED(old->mnt_parent))
1857 * Don't move a mount tree containing unbindable mounts to a destination
1858 * mount which is shared.
1860 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
1863 for (; mnt_has_parent(p); p = p->mnt_parent)
1867 err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
1871 /* if the mount is moved, it should no longer be expire
1873 list_del_init(&old->mnt_expire);
1878 path_put(&parent_path);
1879 path_put(&old_path);
1883 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
1886 const char *subtype = strchr(fstype, '.');
1895 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
1897 if (!mnt->mnt_sb->s_subtype)
1903 return ERR_PTR(err);
1907 * add a mount into a namespace's mount tree
1909 static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
1911 struct mountpoint *mp;
1912 struct mount *parent;
1915 mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
1917 mp = lock_mount(path);
1921 parent = real_mount(path->mnt);
1923 if (unlikely(!check_mnt(parent))) {
1924 /* that's acceptable only for automounts done in private ns */
1925 if (!(mnt_flags & MNT_SHRINKABLE))
1927 /* ... and for those we'd better have mountpoint still alive */
1928 if (!parent->mnt_ns)
1932 /* Refuse the same filesystem on the same mount point */
1934 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
1935 path->mnt->mnt_root == path->dentry)
1939 if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
1942 newmnt->mnt.mnt_flags = mnt_flags;
1943 err = graft_tree(newmnt, parent, mp);
1951 * create a new mount for userspace and request it to be added into the
1954 static int do_new_mount(struct path *path, const char *fstype, int flags,
1955 int mnt_flags, const char *name, void *data)
1957 struct file_system_type *type;
1958 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
1959 struct vfsmount *mnt;
1965 type = get_fs_type(fstype);
1969 if (user_ns != &init_user_ns) {
1970 if (!(type->fs_flags & FS_USERNS_MOUNT)) {
1971 put_filesystem(type);
1974 /* Only in special cases allow devices from mounts
1975 * created outside the initial user namespace.
1977 if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
1979 mnt_flags |= MNT_NODEV;
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);
1988 put_filesystem(type);
1990 return PTR_ERR(mnt);
1992 err = do_add_mount(real_mount(mnt), path, mnt_flags);
1998 int finish_automount(struct vfsmount *m, struct path *path)
2000 struct mount *mnt = real_mount(m);
2002 /* The new mount record should have at least 2 refs to prevent it being
2003 * expired before we get a chance to add it
2005 BUG_ON(mnt_get_count(mnt) < 2);
2007 if (m->mnt_sb == path->mnt->mnt_sb &&
2008 m->mnt_root == path->dentry) {
2013 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2017 /* remove m from any expiration list it may be on */
2018 if (!list_empty(&mnt->mnt_expire)) {
2019 down_write(&namespace_sem);
2020 br_write_lock(&vfsmount_lock);
2021 list_del_init(&mnt->mnt_expire);
2022 br_write_unlock(&vfsmount_lock);
2023 up_write(&namespace_sem);
2031 * mnt_set_expiry - Put a mount on an expiration list
2032 * @mnt: The mount to list.
2033 * @expiry_list: The list to add the mount to.
2035 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2037 down_write(&namespace_sem);
2038 br_write_lock(&vfsmount_lock);
2040 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2042 br_write_unlock(&vfsmount_lock);
2043 up_write(&namespace_sem);
2045 EXPORT_SYMBOL(mnt_set_expiry);
2048 * process a list of expirable mountpoints with the intent of discarding any
2049 * mountpoints that aren't in use and haven't been touched since last we came
2052 void mark_mounts_for_expiry(struct list_head *mounts)
2054 struct mount *mnt, *next;
2055 LIST_HEAD(graveyard);
2057 if (list_empty(mounts))
2060 down_write(&namespace_sem);
2061 br_write_lock(&vfsmount_lock);
2063 /* extract from the expiration list every vfsmount that matches the
2064 * following criteria:
2065 * - only referenced by its parent vfsmount
2066 * - still marked for expiry (marked on the last call here; marks are
2067 * cleared by mntput())
2069 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2070 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2071 propagate_mount_busy(mnt, 1))
2073 list_move(&mnt->mnt_expire, &graveyard);
2075 while (!list_empty(&graveyard)) {
2076 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2077 touch_mnt_namespace(mnt->mnt_ns);
2078 umount_tree(mnt, 1);
2080 br_write_unlock(&vfsmount_lock);
2084 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2087 * Ripoff of 'select_parent()'
2089 * search the list of submounts for a given mountpoint, and move any
2090 * shrinkable submounts to the 'graveyard' list.
2092 static int select_submounts(struct mount *parent, struct list_head *graveyard)
2094 struct mount *this_parent = parent;
2095 struct list_head *next;
2099 next = this_parent->mnt_mounts.next;
2101 while (next != &this_parent->mnt_mounts) {
2102 struct list_head *tmp = next;
2103 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2106 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2109 * Descend a level if the d_mounts list is non-empty.
2111 if (!list_empty(&mnt->mnt_mounts)) {
2116 if (!propagate_mount_busy(mnt, 1)) {
2117 list_move_tail(&mnt->mnt_expire, graveyard);
2122 * All done at this level ... ascend and resume the search
2124 if (this_parent != parent) {
2125 next = this_parent->mnt_child.next;
2126 this_parent = this_parent->mnt_parent;
2133 * process a list of expirable mountpoints with the intent of discarding any
2134 * submounts of a specific parent mountpoint
2136 * vfsmount_lock must be held for write
2138 static void shrink_submounts(struct mount *mnt)
2140 LIST_HEAD(graveyard);
2143 /* extract submounts of 'mountpoint' from the expiration list */
2144 while (select_submounts(mnt, &graveyard)) {
2145 while (!list_empty(&graveyard)) {
2146 m = list_first_entry(&graveyard, struct mount,
2148 touch_mnt_namespace(m->mnt_ns);
2155 * Some copy_from_user() implementations do not return the exact number of
2156 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2157 * Note that this function differs from copy_from_user() in that it will oops
2158 * on bad values of `to', rather than returning a short copy.
2160 static long exact_copy_from_user(void *to, const void __user * from,
2164 const char __user *f = from;
2167 if (!access_ok(VERIFY_READ, from, n))
2171 if (__get_user(c, f)) {
2182 int copy_mount_options(const void __user * data, unsigned long *where)
2192 if (!(page = __get_free_page(GFP_KERNEL)))
2195 /* We only care that *some* data at the address the user
2196 * gave us is valid. Just in case, we'll zero
2197 * the remainder of the page.
2199 /* copy_from_user cannot cross TASK_SIZE ! */
2200 size = TASK_SIZE - (unsigned long)data;
2201 if (size > PAGE_SIZE)
2204 i = size - exact_copy_from_user((void *)page, data, size);
2210 memset((char *)page + i, 0, PAGE_SIZE - i);
2215 int copy_mount_string(const void __user *data, char **where)
2224 tmp = strndup_user(data, PAGE_SIZE);
2226 return PTR_ERR(tmp);
2233 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2234 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2236 * data is a (void *) that can point to any structure up to
2237 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2238 * information (or be NULL).
2240 * Pre-0.97 versions of mount() didn't have a flags word.
2241 * When the flags word was introduced its top half was required
2242 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2243 * Therefore, if this magic number is present, it carries no information
2244 * and must be discarded.
2246 long do_mount(const char *dev_name, const char *dir_name,
2247 const char *type_page, unsigned long flags, void *data_page)
2254 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2255 flags &= ~MS_MGC_MSK;
2257 /* Basic sanity checks */
2259 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2263 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2265 /* ... and get the mountpoint */
2266 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2270 retval = security_sb_mount(dev_name, &path,
2271 type_page, flags, data_page);
2278 /* Default to relatime unless overriden */
2279 if (!(flags & MS_NOATIME))
2280 mnt_flags |= MNT_RELATIME;
2282 /* Separate the per-mountpoint flags */
2283 if (flags & MS_NOSUID)
2284 mnt_flags |= MNT_NOSUID;
2285 if (flags & MS_NODEV)
2286 mnt_flags |= MNT_NODEV;
2287 if (flags & MS_NOEXEC)
2288 mnt_flags |= MNT_NOEXEC;
2289 if (flags & MS_NOATIME)
2290 mnt_flags |= MNT_NOATIME;
2291 if (flags & MS_NODIRATIME)
2292 mnt_flags |= MNT_NODIRATIME;
2293 if (flags & MS_STRICTATIME)
2294 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2295 if (flags & MS_RDONLY)
2296 mnt_flags |= MNT_READONLY;
2298 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2299 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2302 if (flags & MS_REMOUNT)
2303 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2305 else if (flags & MS_BIND)
2306 retval = do_loopback(&path, dev_name, flags & MS_REC);
2307 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2308 retval = do_change_type(&path, flags);
2309 else if (flags & MS_MOVE)
2310 retval = do_move_mount(&path, dev_name);
2312 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2313 dev_name, data_page);
2319 static void free_mnt_ns(struct mnt_namespace *ns)
2321 proc_free_inum(ns->proc_inum);
2322 put_user_ns(ns->user_ns);
2327 * Assign a sequence number so we can detect when we attempt to bind
2328 * mount a reference to an older mount namespace into the current
2329 * mount namespace, preventing reference counting loops. A 64bit
2330 * number incrementing at 10Ghz will take 12,427 years to wrap which
2331 * is effectively never, so we can ignore the possibility.
2333 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
2335 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
2337 struct mnt_namespace *new_ns;
2340 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2342 return ERR_PTR(-ENOMEM);
2343 ret = proc_alloc_inum(&new_ns->proc_inum);
2346 return ERR_PTR(ret);
2348 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
2349 atomic_set(&new_ns->count, 1);
2350 new_ns->root = NULL;
2351 INIT_LIST_HEAD(&new_ns->list);
2352 init_waitqueue_head(&new_ns->poll);
2354 new_ns->user_ns = get_user_ns(user_ns);
2359 * Allocate a new namespace structure and populate it with contents
2360 * copied from the namespace of the passed in task structure.
2362 static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
2363 struct user_namespace *user_ns, struct fs_struct *fs)
2365 struct mnt_namespace *new_ns;
2366 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2367 struct mount *p, *q;
2368 struct mount *old = mnt_ns->root;
2372 new_ns = alloc_mnt_ns(user_ns);
2376 down_write(&namespace_sem);
2377 /* First pass: copy the tree topology */
2378 copy_flags = CL_COPY_ALL | CL_EXPIRE;
2379 if (user_ns != mnt_ns->user_ns)
2380 copy_flags |= CL_SHARED_TO_SLAVE;
2381 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
2384 free_mnt_ns(new_ns);
2385 return ERR_CAST(new);
2388 br_write_lock(&vfsmount_lock);
2389 list_add_tail(&new_ns->list, &new->mnt_list);
2390 br_write_unlock(&vfsmount_lock);
2393 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2394 * as belonging to new namespace. We have already acquired a private
2395 * fs_struct, so tsk->fs->lock is not needed.
2402 if (&p->mnt == fs->root.mnt) {
2403 fs->root.mnt = mntget(&q->mnt);
2406 if (&p->mnt == fs->pwd.mnt) {
2407 fs->pwd.mnt = mntget(&q->mnt);
2411 p = next_mnt(p, old);
2412 q = next_mnt(q, new);
2424 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2425 struct user_namespace *user_ns, struct fs_struct *new_fs)
2427 struct mnt_namespace *new_ns;
2432 if (!(flags & CLONE_NEWNS))
2435 new_ns = dup_mnt_ns(ns, user_ns, new_fs);
2442 * create_mnt_ns - creates a private namespace and adds a root filesystem
2443 * @mnt: pointer to the new root filesystem mountpoint
2445 static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
2447 struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
2448 if (!IS_ERR(new_ns)) {
2449 struct mount *mnt = real_mount(m);
2450 mnt->mnt_ns = new_ns;
2452 list_add(&new_ns->list, &mnt->mnt_list);
2459 struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
2461 struct mnt_namespace *ns;
2462 struct super_block *s;
2466 ns = create_mnt_ns(mnt);
2468 return ERR_CAST(ns);
2470 err = vfs_path_lookup(mnt->mnt_root, mnt,
2471 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
2476 return ERR_PTR(err);
2478 /* trade a vfsmount reference for active sb one */
2479 s = path.mnt->mnt_sb;
2480 atomic_inc(&s->s_active);
2482 /* lock the sucker */
2483 down_write(&s->s_umount);
2484 /* ... and return the root of (sub)tree on it */
2487 EXPORT_SYMBOL(mount_subtree);
2489 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2490 char __user *, type, unsigned long, flags, void __user *, data)
2494 struct filename *kernel_dir;
2496 unsigned long data_page;
2498 ret = copy_mount_string(type, &kernel_type);
2502 kernel_dir = getname(dir_name);
2503 if (IS_ERR(kernel_dir)) {
2504 ret = PTR_ERR(kernel_dir);
2508 ret = copy_mount_string(dev_name, &kernel_dev);
2512 ret = copy_mount_options(data, &data_page);
2516 ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
2517 (void *) data_page);
2519 free_page(data_page);
2523 putname(kernel_dir);
2531 * Return true if path is reachable from root
2533 * namespace_sem or vfsmount_lock is held
2535 bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
2536 const struct path *root)
2538 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
2539 dentry = mnt->mnt_mountpoint;
2540 mnt = mnt->mnt_parent;
2542 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
2545 int path_is_under(struct path *path1, struct path *path2)
2548 br_read_lock(&vfsmount_lock);
2549 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
2550 br_read_unlock(&vfsmount_lock);
2553 EXPORT_SYMBOL(path_is_under);
2556 * pivot_root Semantics:
2557 * Moves the root file system of the current process to the directory put_old,
2558 * makes new_root as the new root file system of the current process, and sets
2559 * root/cwd of all processes which had them on the current root to new_root.
2562 * The new_root and put_old must be directories, and must not be on the
2563 * same file system as the current process root. The put_old must be
2564 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2565 * pointed to by put_old must yield the same directory as new_root. No other
2566 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2568 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2569 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2570 * in this situation.
2573 * - we don't move root/cwd if they are not at the root (reason: if something
2574 * cared enough to change them, it's probably wrong to force them elsewhere)
2575 * - it's okay to pick a root that isn't the root of a file system, e.g.
2576 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2577 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2580 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2581 const char __user *, put_old)
2583 struct path new, old, parent_path, root_parent, root;
2584 struct mount *new_mnt, *root_mnt, *old_mnt;
2585 struct mountpoint *old_mp, *root_mp;
2591 error = user_path_dir(new_root, &new);
2595 error = user_path_dir(put_old, &old);
2599 error = security_sb_pivotroot(&old, &new);
2603 get_fs_root(current->fs, &root);
2604 old_mp = lock_mount(&old);
2605 error = PTR_ERR(old_mp);
2610 new_mnt = real_mount(new.mnt);
2611 root_mnt = real_mount(root.mnt);
2612 old_mnt = real_mount(old.mnt);
2613 if (IS_MNT_SHARED(old_mnt) ||
2614 IS_MNT_SHARED(new_mnt->mnt_parent) ||
2615 IS_MNT_SHARED(root_mnt->mnt_parent))
2617 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
2620 if (d_unlinked(new.dentry))
2623 if (new_mnt == root_mnt || old_mnt == root_mnt)
2624 goto out4; /* loop, on the same file system */
2626 if (root.mnt->mnt_root != root.dentry)
2627 goto out4; /* not a mountpoint */
2628 if (!mnt_has_parent(root_mnt))
2629 goto out4; /* not attached */
2630 root_mp = root_mnt->mnt_mp;
2631 if (new.mnt->mnt_root != new.dentry)
2632 goto out4; /* not a mountpoint */
2633 if (!mnt_has_parent(new_mnt))
2634 goto out4; /* not attached */
2635 /* make sure we can reach put_old from new_root */
2636 if (!is_path_reachable(old_mnt, old.dentry, &new))
2638 root_mp->m_count++; /* pin it so it won't go away */
2639 br_write_lock(&vfsmount_lock);
2640 detach_mnt(new_mnt, &parent_path);
2641 detach_mnt(root_mnt, &root_parent);
2642 /* mount old root on put_old */
2643 attach_mnt(root_mnt, old_mnt, old_mp);
2644 /* mount new_root on / */
2645 attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
2646 touch_mnt_namespace(current->nsproxy->mnt_ns);
2647 br_write_unlock(&vfsmount_lock);
2648 chroot_fs_refs(&root, &new);
2649 put_mountpoint(root_mp);
2652 unlock_mount(old_mp);
2654 path_put(&root_parent);
2655 path_put(&parent_path);
2667 static void __init init_mount_tree(void)
2669 struct vfsmount *mnt;
2670 struct mnt_namespace *ns;
2672 struct file_system_type *type;
2674 type = get_fs_type("rootfs");
2676 panic("Can't find rootfs type");
2677 mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
2678 put_filesystem(type);
2680 panic("Can't create rootfs");
2682 ns = create_mnt_ns(mnt);
2684 panic("Can't allocate initial namespace");
2686 init_task.nsproxy->mnt_ns = ns;
2690 root.dentry = mnt->mnt_root;
2692 set_fs_pwd(current->fs, &root);
2693 set_fs_root(current->fs, &root);
2696 void __init mnt_init(void)
2701 init_rwsem(&namespace_sem);
2703 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
2704 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2706 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2707 mountpoint_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2709 if (!mount_hashtable || !mountpoint_hashtable)
2710 panic("Failed to allocate mount hash table\n");
2712 printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);
2714 for (u = 0; u < HASH_SIZE; u++)
2715 INIT_LIST_HEAD(&mount_hashtable[u]);
2716 for (u = 0; u < HASH_SIZE; u++)
2717 INIT_LIST_HEAD(&mountpoint_hashtable[u]);
2719 br_lock_init(&vfsmount_lock);
2723 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2725 fs_kobj = kobject_create_and_add("fs", NULL);
2727 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2732 void put_mnt_ns(struct mnt_namespace *ns)
2734 if (!atomic_dec_and_test(&ns->count))
2736 down_write(&namespace_sem);
2737 br_write_lock(&vfsmount_lock);
2738 umount_tree(ns->root, 0);
2739 br_write_unlock(&vfsmount_lock);
2744 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2746 struct vfsmount *mnt;
2747 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2750 * it is a longterm mount, don't release mnt until
2751 * we unmount before file sys is unregistered
2753 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
2757 EXPORT_SYMBOL_GPL(kern_mount_data);
2759 void kern_unmount(struct vfsmount *mnt)
2761 /* release long term mount so mount point can be released */
2762 if (!IS_ERR_OR_NULL(mnt)) {
2763 br_write_lock(&vfsmount_lock);
2764 real_mount(mnt)->mnt_ns = NULL;
2765 br_write_unlock(&vfsmount_lock);
2769 EXPORT_SYMBOL(kern_unmount);
2771 bool our_mnt(struct vfsmount *mnt)
2773 return check_mnt(real_mount(mnt));
2776 static void *mntns_get(struct task_struct *task)
2778 struct mnt_namespace *ns = NULL;
2779 struct nsproxy *nsproxy;
2782 nsproxy = task_nsproxy(task);
2784 ns = nsproxy->mnt_ns;
2792 static void mntns_put(void *ns)
2797 static int mntns_install(struct nsproxy *nsproxy, void *ns)
2799 struct fs_struct *fs = current->fs;
2800 struct mnt_namespace *mnt_ns = ns;
2803 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
2804 !nsown_capable(CAP_SYS_CHROOT) ||
2805 !nsown_capable(CAP_SYS_ADMIN))
2812 put_mnt_ns(nsproxy->mnt_ns);
2813 nsproxy->mnt_ns = mnt_ns;
2816 root.mnt = &mnt_ns->root->mnt;
2817 root.dentry = mnt_ns->root->mnt.mnt_root;
2819 while(d_mountpoint(root.dentry) && follow_down_one(&root))
2822 /* Update the pwd and root */
2823 set_fs_pwd(fs, &root);
2824 set_fs_root(fs, &root);
2830 static unsigned int mntns_inum(void *ns)
2832 struct mnt_namespace *mnt_ns = ns;
2833 return mnt_ns->proc_inum;
2836 const struct proc_ns_operations mntns_operations = {
2838 .type = CLONE_NEWNS,
2841 .install = mntns_install,