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 kmem_cache *mnt_cache __read_mostly;
40 static struct rw_semaphore namespace_sem;
43 struct kobject *fs_kobj;
44 EXPORT_SYMBOL_GPL(fs_kobj);
47 * vfsmount lock may be taken for read to prevent changes to the
48 * vfsmount hash, ie. during mountpoint lookups or walking back
51 * It should be taken for write in all cases where the vfsmount
52 * tree or hash is modified or when a vfsmount structure is modified.
54 DEFINE_BRLOCK(vfsmount_lock);
56 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
58 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
59 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
60 tmp = tmp + (tmp >> HASH_SHIFT);
61 return tmp & (HASH_SIZE - 1);
64 #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
67 * allocation is serialized by namespace_sem, but we need the spinlock to
68 * serialize with freeing.
70 static int mnt_alloc_id(struct mount *mnt)
75 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
76 spin_lock(&mnt_id_lock);
77 res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
79 mnt_id_start = mnt->mnt_id + 1;
80 spin_unlock(&mnt_id_lock);
87 static void mnt_free_id(struct mount *mnt)
90 spin_lock(&mnt_id_lock);
91 ida_remove(&mnt_id_ida, id);
92 if (mnt_id_start > id)
94 spin_unlock(&mnt_id_lock);
98 * Allocate a new peer group ID
100 * mnt_group_ida is protected by namespace_sem
102 static int mnt_alloc_group_id(struct mount *mnt)
106 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
109 res = ida_get_new_above(&mnt_group_ida,
113 mnt_group_start = mnt->mnt_group_id + 1;
119 * Release a peer group ID
121 void mnt_release_group_id(struct mount *mnt)
123 int id = mnt->mnt_group_id;
124 ida_remove(&mnt_group_ida, id);
125 if (mnt_group_start > id)
126 mnt_group_start = id;
127 mnt->mnt_group_id = 0;
131 * vfsmount lock must be held for read
133 static inline void mnt_add_count(struct mount *mnt, int n)
136 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
145 * vfsmount lock must be held for write
147 unsigned int mnt_get_count(struct mount *mnt)
150 unsigned int count = 0;
153 for_each_possible_cpu(cpu) {
154 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
159 return mnt->mnt_count;
163 static struct mount *alloc_vfsmnt(const char *name)
165 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
169 err = mnt_alloc_id(mnt);
174 mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
175 if (!mnt->mnt_devname)
180 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
182 goto out_free_devname;
184 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
187 mnt->mnt_writers = 0;
190 INIT_LIST_HEAD(&mnt->mnt_hash);
191 INIT_LIST_HEAD(&mnt->mnt_child);
192 INIT_LIST_HEAD(&mnt->mnt_mounts);
193 INIT_LIST_HEAD(&mnt->mnt_list);
194 INIT_LIST_HEAD(&mnt->mnt_expire);
195 INIT_LIST_HEAD(&mnt->mnt_share);
196 INIT_LIST_HEAD(&mnt->mnt_slave_list);
197 INIT_LIST_HEAD(&mnt->mnt_slave);
198 #ifdef CONFIG_FSNOTIFY
199 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
206 kfree(mnt->mnt_devname);
211 kmem_cache_free(mnt_cache, mnt);
216 * Most r/o checks on a fs are for operations that take
217 * discrete amounts of time, like a write() or unlink().
218 * We must keep track of when those operations start
219 * (for permission checks) and when they end, so that
220 * we can determine when writes are able to occur to
224 * __mnt_is_readonly: check whether a mount is read-only
225 * @mnt: the mount to check for its write status
227 * This shouldn't be used directly ouside of the VFS.
228 * It does not guarantee that the filesystem will stay
229 * r/w, just that it is right *now*. This can not and
230 * should not be used in place of IS_RDONLY(inode).
231 * mnt_want/drop_write() will _keep_ the filesystem
234 int __mnt_is_readonly(struct vfsmount *mnt)
236 if (mnt->mnt_flags & MNT_READONLY)
238 if (mnt->mnt_sb->s_flags & MS_RDONLY)
242 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
244 static inline void mnt_inc_writers(struct mount *mnt)
247 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
253 static inline void mnt_dec_writers(struct mount *mnt)
256 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
262 static unsigned int mnt_get_writers(struct mount *mnt)
265 unsigned int count = 0;
268 for_each_possible_cpu(cpu) {
269 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
274 return mnt->mnt_writers;
278 static int mnt_is_readonly(struct vfsmount *mnt)
280 if (mnt->mnt_sb->s_readonly_remount)
282 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
284 return __mnt_is_readonly(mnt);
288 * Most r/o & frozen checks on a fs are for operations that take discrete
289 * amounts of time, like a write() or unlink(). We must keep track of when
290 * those operations start (for permission checks) and when they end, so that we
291 * can determine when writes are able to occur to a filesystem.
294 * __mnt_want_write - get write access to a mount without freeze protection
295 * @m: the mount on which to take a write
297 * This tells the low-level filesystem that a write is about to be performed to
298 * it, and makes sure that writes are allowed (mnt it read-write) before
299 * returning success. This operation does not protect against filesystem being
300 * frozen. When the write operation is finished, __mnt_drop_write() must be
301 * called. This is effectively a refcount.
303 int __mnt_want_write(struct vfsmount *m)
305 struct mount *mnt = real_mount(m);
309 mnt_inc_writers(mnt);
311 * The store to mnt_inc_writers must be visible before we pass
312 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
313 * incremented count after it has set MNT_WRITE_HOLD.
316 while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
319 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
320 * be set to match its requirements. So we must not load that until
321 * MNT_WRITE_HOLD is cleared.
324 if (mnt_is_readonly(m)) {
325 mnt_dec_writers(mnt);
334 * mnt_want_write - get write access to a mount
335 * @m: the mount on which to take a write
337 * This tells the low-level filesystem that a write is about to be performed to
338 * it, and makes sure that writes are allowed (mount is read-write, filesystem
339 * is not frozen) before returning success. When the write operation is
340 * finished, mnt_drop_write() must be called. This is effectively a refcount.
342 int mnt_want_write(struct vfsmount *m)
346 sb_start_write(m->mnt_sb);
347 ret = __mnt_want_write(m);
349 sb_end_write(m->mnt_sb);
352 EXPORT_SYMBOL_GPL(mnt_want_write);
355 * mnt_clone_write - get write access to a mount
356 * @mnt: the mount on which to take a write
358 * This is effectively like mnt_want_write, except
359 * it must only be used to take an extra write reference
360 * on a mountpoint that we already know has a write reference
361 * on it. This allows some optimisation.
363 * After finished, mnt_drop_write must be called as usual to
364 * drop the reference.
366 int mnt_clone_write(struct vfsmount *mnt)
368 /* superblock may be r/o */
369 if (__mnt_is_readonly(mnt))
372 mnt_inc_writers(real_mount(mnt));
376 EXPORT_SYMBOL_GPL(mnt_clone_write);
379 * __mnt_want_write_file - get write access to a file's mount
380 * @file: the file who's mount on which to take a write
382 * This is like __mnt_want_write, but it takes a file and can
383 * do some optimisations if the file is open for write already
385 int __mnt_want_write_file(struct file *file)
387 struct inode *inode = file_inode(file);
389 if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
390 return __mnt_want_write(file->f_path.mnt);
392 return mnt_clone_write(file->f_path.mnt);
396 * mnt_want_write_file - get write access to a file's mount
397 * @file: the file who's mount on which to take a write
399 * This is like mnt_want_write, but it takes a file and can
400 * do some optimisations if the file is open for write already
402 int mnt_want_write_file(struct file *file)
406 sb_start_write(file->f_path.mnt->mnt_sb);
407 ret = __mnt_want_write_file(file);
409 sb_end_write(file->f_path.mnt->mnt_sb);
412 EXPORT_SYMBOL_GPL(mnt_want_write_file);
415 * __mnt_drop_write - give up write access to a mount
416 * @mnt: the mount on which to give up write access
418 * Tells the low-level filesystem that we are done
419 * performing writes to it. Must be matched with
420 * __mnt_want_write() call above.
422 void __mnt_drop_write(struct vfsmount *mnt)
425 mnt_dec_writers(real_mount(mnt));
430 * mnt_drop_write - give up write access to a mount
431 * @mnt: the mount on which to give up write access
433 * Tells the low-level filesystem that we are done performing writes to it and
434 * also allows filesystem to be frozen again. Must be matched with
435 * mnt_want_write() call above.
437 void mnt_drop_write(struct vfsmount *mnt)
439 __mnt_drop_write(mnt);
440 sb_end_write(mnt->mnt_sb);
442 EXPORT_SYMBOL_GPL(mnt_drop_write);
444 void __mnt_drop_write_file(struct file *file)
446 __mnt_drop_write(file->f_path.mnt);
449 void mnt_drop_write_file(struct file *file)
451 mnt_drop_write(file->f_path.mnt);
453 EXPORT_SYMBOL(mnt_drop_write_file);
455 static int mnt_make_readonly(struct mount *mnt)
459 br_write_lock(&vfsmount_lock);
460 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
462 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
463 * should be visible before we do.
468 * With writers on hold, if this value is zero, then there are
469 * definitely no active writers (although held writers may subsequently
470 * increment the count, they'll have to wait, and decrement it after
471 * seeing MNT_READONLY).
473 * It is OK to have counter incremented on one CPU and decremented on
474 * another: the sum will add up correctly. The danger would be when we
475 * sum up each counter, if we read a counter before it is incremented,
476 * but then read another CPU's count which it has been subsequently
477 * decremented from -- we would see more decrements than we should.
478 * MNT_WRITE_HOLD protects against this scenario, because
479 * mnt_want_write first increments count, then smp_mb, then spins on
480 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
481 * we're counting up here.
483 if (mnt_get_writers(mnt) > 0)
486 mnt->mnt.mnt_flags |= MNT_READONLY;
488 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
489 * that become unheld will see MNT_READONLY.
492 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
493 br_write_unlock(&vfsmount_lock);
497 static void __mnt_unmake_readonly(struct mount *mnt)
499 br_write_lock(&vfsmount_lock);
500 mnt->mnt.mnt_flags &= ~MNT_READONLY;
501 br_write_unlock(&vfsmount_lock);
504 int sb_prepare_remount_readonly(struct super_block *sb)
509 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
510 if (atomic_long_read(&sb->s_remove_count))
513 br_write_lock(&vfsmount_lock);
514 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
515 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
516 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
518 if (mnt_get_writers(mnt) > 0) {
524 if (!err && atomic_long_read(&sb->s_remove_count))
528 sb->s_readonly_remount = 1;
531 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
532 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
533 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
535 br_write_unlock(&vfsmount_lock);
540 static void free_vfsmnt(struct mount *mnt)
542 kfree(mnt->mnt_devname);
545 free_percpu(mnt->mnt_pcp);
547 kmem_cache_free(mnt_cache, mnt);
551 * find the first or last mount at @dentry on vfsmount @mnt depending on
552 * @dir. If @dir is set return the first mount else return the last mount.
553 * vfsmount_lock must be held for read or write.
555 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
558 struct list_head *head = mount_hashtable + hash(mnt, dentry);
559 struct list_head *tmp = head;
560 struct mount *p, *found = NULL;
563 tmp = dir ? tmp->next : tmp->prev;
567 p = list_entry(tmp, struct mount, mnt_hash);
568 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) {
577 * lookup_mnt - Return the first child mount mounted at path
579 * "First" means first mounted chronologically. If you create the
582 * mount /dev/sda1 /mnt
583 * mount /dev/sda2 /mnt
584 * mount /dev/sda3 /mnt
586 * Then lookup_mnt() on the base /mnt dentry in the root mount will
587 * return successively the root dentry and vfsmount of /dev/sda1, then
588 * /dev/sda2, then /dev/sda3, then NULL.
590 * lookup_mnt takes a reference to the found vfsmount.
592 struct vfsmount *lookup_mnt(struct path *path)
594 struct mount *child_mnt;
596 br_read_lock(&vfsmount_lock);
597 child_mnt = __lookup_mnt(path->mnt, path->dentry, 1);
599 mnt_add_count(child_mnt, 1);
600 br_read_unlock(&vfsmount_lock);
601 return &child_mnt->mnt;
603 br_read_unlock(&vfsmount_lock);
608 static inline int check_mnt(struct mount *mnt)
610 return mnt->mnt_ns == current->nsproxy->mnt_ns;
614 * vfsmount lock must be held for write
616 static void touch_mnt_namespace(struct mnt_namespace *ns)
620 wake_up_interruptible(&ns->poll);
625 * vfsmount lock must be held for write
627 static void __touch_mnt_namespace(struct mnt_namespace *ns)
629 if (ns && ns->event != event) {
631 wake_up_interruptible(&ns->poll);
636 * Clear dentry's mounted state if it has no remaining mounts.
637 * vfsmount_lock must be held for write.
639 static void dentry_reset_mounted(struct dentry *dentry)
643 for (u = 0; u < HASH_SIZE; u++) {
646 list_for_each_entry(p, &mount_hashtable[u], mnt_hash) {
647 if (p->mnt_mountpoint == dentry)
651 spin_lock(&dentry->d_lock);
652 dentry->d_flags &= ~DCACHE_MOUNTED;
653 spin_unlock(&dentry->d_lock);
657 * vfsmount lock must be held for write
659 static void detach_mnt(struct mount *mnt, struct path *old_path)
661 old_path->dentry = mnt->mnt_mountpoint;
662 old_path->mnt = &mnt->mnt_parent->mnt;
663 mnt->mnt_parent = mnt;
664 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
665 list_del_init(&mnt->mnt_child);
666 list_del_init(&mnt->mnt_hash);
667 dentry_reset_mounted(old_path->dentry);
671 * vfsmount lock must be held for write
673 void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry,
674 struct mount *child_mnt)
676 mnt_add_count(mnt, 1); /* essentially, that's mntget */
677 child_mnt->mnt_mountpoint = dget(dentry);
678 child_mnt->mnt_parent = mnt;
679 spin_lock(&dentry->d_lock);
680 dentry->d_flags |= DCACHE_MOUNTED;
681 spin_unlock(&dentry->d_lock);
685 * vfsmount lock must be held for write
687 static void attach_mnt(struct mount *mnt, struct path *path)
689 mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt);
690 list_add_tail(&mnt->mnt_hash, mount_hashtable +
691 hash(path->mnt, path->dentry));
692 list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts);
696 * vfsmount lock must be held for write
698 static void commit_tree(struct mount *mnt)
700 struct mount *parent = mnt->mnt_parent;
703 struct mnt_namespace *n = parent->mnt_ns;
705 BUG_ON(parent == mnt);
707 list_add_tail(&head, &mnt->mnt_list);
708 list_for_each_entry(m, &head, mnt_list)
711 list_splice(&head, n->list.prev);
713 list_add_tail(&mnt->mnt_hash, mount_hashtable +
714 hash(&parent->mnt, mnt->mnt_mountpoint));
715 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
716 touch_mnt_namespace(n);
719 static struct mount *next_mnt(struct mount *p, struct mount *root)
721 struct list_head *next = p->mnt_mounts.next;
722 if (next == &p->mnt_mounts) {
726 next = p->mnt_child.next;
727 if (next != &p->mnt_parent->mnt_mounts)
732 return list_entry(next, struct mount, mnt_child);
735 static struct mount *skip_mnt_tree(struct mount *p)
737 struct list_head *prev = p->mnt_mounts.prev;
738 while (prev != &p->mnt_mounts) {
739 p = list_entry(prev, struct mount, mnt_child);
740 prev = p->mnt_mounts.prev;
746 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
752 return ERR_PTR(-ENODEV);
754 mnt = alloc_vfsmnt(name);
756 return ERR_PTR(-ENOMEM);
758 if (flags & MS_KERNMOUNT)
759 mnt->mnt.mnt_flags = MNT_INTERNAL;
761 root = mount_fs(type, flags, name, data);
764 return ERR_CAST(root);
767 mnt->mnt.mnt_root = root;
768 mnt->mnt.mnt_sb = root->d_sb;
769 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
770 mnt->mnt_parent = mnt;
771 br_write_lock(&vfsmount_lock);
772 list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
773 br_write_unlock(&vfsmount_lock);
776 EXPORT_SYMBOL_GPL(vfs_kern_mount);
778 static struct mount *clone_mnt(struct mount *old, struct dentry *root,
781 struct super_block *sb = old->mnt.mnt_sb;
785 mnt = alloc_vfsmnt(old->mnt_devname);
787 return ERR_PTR(-ENOMEM);
789 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
790 mnt->mnt_group_id = 0; /* not a peer of original */
792 mnt->mnt_group_id = old->mnt_group_id;
794 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
795 err = mnt_alloc_group_id(mnt);
800 mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
801 atomic_inc(&sb->s_active);
802 mnt->mnt.mnt_sb = sb;
803 mnt->mnt.mnt_root = dget(root);
804 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
805 mnt->mnt_parent = mnt;
806 br_write_lock(&vfsmount_lock);
807 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
808 br_write_unlock(&vfsmount_lock);
810 if ((flag & CL_SLAVE) ||
811 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
812 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
813 mnt->mnt_master = old;
814 CLEAR_MNT_SHARED(mnt);
815 } else if (!(flag & CL_PRIVATE)) {
816 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
817 list_add(&mnt->mnt_share, &old->mnt_share);
818 if (IS_MNT_SLAVE(old))
819 list_add(&mnt->mnt_slave, &old->mnt_slave);
820 mnt->mnt_master = old->mnt_master;
822 if (flag & CL_MAKE_SHARED)
825 /* stick the duplicate mount on the same expiry list
826 * as the original if that was on one */
827 if (flag & CL_EXPIRE) {
828 if (!list_empty(&old->mnt_expire))
829 list_add(&mnt->mnt_expire, &old->mnt_expire);
839 static inline void mntfree(struct mount *mnt)
841 struct vfsmount *m = &mnt->mnt;
842 struct super_block *sb = m->mnt_sb;
845 * This probably indicates that somebody messed
846 * up a mnt_want/drop_write() pair. If this
847 * happens, the filesystem was probably unable
848 * to make r/w->r/o transitions.
851 * The locking used to deal with mnt_count decrement provides barriers,
852 * so mnt_get_writers() below is safe.
854 WARN_ON(mnt_get_writers(mnt));
855 fsnotify_vfsmount_delete(m);
858 deactivate_super(sb);
861 static void mntput_no_expire(struct mount *mnt)
865 br_read_lock(&vfsmount_lock);
866 if (likely(mnt->mnt_ns)) {
867 /* shouldn't be the last one */
868 mnt_add_count(mnt, -1);
869 br_read_unlock(&vfsmount_lock);
872 br_read_unlock(&vfsmount_lock);
874 br_write_lock(&vfsmount_lock);
875 mnt_add_count(mnt, -1);
876 if (mnt_get_count(mnt)) {
877 br_write_unlock(&vfsmount_lock);
881 mnt_add_count(mnt, -1);
882 if (likely(mnt_get_count(mnt)))
884 br_write_lock(&vfsmount_lock);
886 if (unlikely(mnt->mnt_pinned)) {
887 mnt_add_count(mnt, mnt->mnt_pinned + 1);
889 br_write_unlock(&vfsmount_lock);
890 acct_auto_close_mnt(&mnt->mnt);
894 list_del(&mnt->mnt_instance);
895 br_write_unlock(&vfsmount_lock);
899 void mntput(struct vfsmount *mnt)
902 struct mount *m = real_mount(mnt);
903 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
904 if (unlikely(m->mnt_expiry_mark))
905 m->mnt_expiry_mark = 0;
909 EXPORT_SYMBOL(mntput);
911 struct vfsmount *mntget(struct vfsmount *mnt)
914 mnt_add_count(real_mount(mnt), 1);
917 EXPORT_SYMBOL(mntget);
919 void mnt_pin(struct vfsmount *mnt)
921 br_write_lock(&vfsmount_lock);
922 real_mount(mnt)->mnt_pinned++;
923 br_write_unlock(&vfsmount_lock);
925 EXPORT_SYMBOL(mnt_pin);
927 void mnt_unpin(struct vfsmount *m)
929 struct mount *mnt = real_mount(m);
930 br_write_lock(&vfsmount_lock);
931 if (mnt->mnt_pinned) {
932 mnt_add_count(mnt, 1);
935 br_write_unlock(&vfsmount_lock);
937 EXPORT_SYMBOL(mnt_unpin);
939 static inline void mangle(struct seq_file *m, const char *s)
941 seq_escape(m, s, " \t\n\\");
945 * Simple .show_options callback for filesystems which don't want to
946 * implement more complex mount option showing.
948 * See also save_mount_options().
950 int generic_show_options(struct seq_file *m, struct dentry *root)
955 options = rcu_dereference(root->d_sb->s_options);
957 if (options != NULL && options[0]) {
965 EXPORT_SYMBOL(generic_show_options);
968 * If filesystem uses generic_show_options(), this function should be
969 * called from the fill_super() callback.
971 * The .remount_fs callback usually needs to be handled in a special
972 * way, to make sure, that previous options are not overwritten if the
975 * Also note, that if the filesystem's .remount_fs function doesn't
976 * reset all options to their default value, but changes only newly
977 * given options, then the displayed options will not reflect reality
980 void save_mount_options(struct super_block *sb, char *options)
982 BUG_ON(sb->s_options);
983 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
985 EXPORT_SYMBOL(save_mount_options);
987 void replace_mount_options(struct super_block *sb, char *options)
989 char *old = sb->s_options;
990 rcu_assign_pointer(sb->s_options, options);
996 EXPORT_SYMBOL(replace_mount_options);
998 #ifdef CONFIG_PROC_FS
999 /* iterator; we want it to have access to namespace_sem, thus here... */
1000 static void *m_start(struct seq_file *m, loff_t *pos)
1002 struct proc_mounts *p = proc_mounts(m);
1004 down_read(&namespace_sem);
1005 return seq_list_start(&p->ns->list, *pos);
1008 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1010 struct proc_mounts *p = proc_mounts(m);
1012 return seq_list_next(v, &p->ns->list, pos);
1015 static void m_stop(struct seq_file *m, void *v)
1017 up_read(&namespace_sem);
1020 static int m_show(struct seq_file *m, void *v)
1022 struct proc_mounts *p = proc_mounts(m);
1023 struct mount *r = list_entry(v, struct mount, mnt_list);
1024 return p->show(m, &r->mnt);
1027 const struct seq_operations mounts_op = {
1033 #endif /* CONFIG_PROC_FS */
1036 * may_umount_tree - check if a mount tree is busy
1037 * @mnt: root of mount tree
1039 * This is called to check if a tree of mounts has any
1040 * open files, pwds, chroots or sub mounts that are
1043 int may_umount_tree(struct vfsmount *m)
1045 struct mount *mnt = real_mount(m);
1046 int actual_refs = 0;
1047 int minimum_refs = 0;
1051 /* write lock needed for mnt_get_count */
1052 br_write_lock(&vfsmount_lock);
1053 for (p = mnt; p; p = next_mnt(p, mnt)) {
1054 actual_refs += mnt_get_count(p);
1057 br_write_unlock(&vfsmount_lock);
1059 if (actual_refs > minimum_refs)
1065 EXPORT_SYMBOL(may_umount_tree);
1068 * may_umount - check if a mount point is busy
1069 * @mnt: root of mount
1071 * This is called to check if a mount point has any
1072 * open files, pwds, chroots or sub mounts. If the
1073 * mount has sub mounts this will return busy
1074 * regardless of whether the sub mounts are busy.
1076 * Doesn't take quota and stuff into account. IOW, in some cases it will
1077 * give false negatives. The main reason why it's here is that we need
1078 * a non-destructive way to look for easily umountable filesystems.
1080 int may_umount(struct vfsmount *mnt)
1083 down_read(&namespace_sem);
1084 br_write_lock(&vfsmount_lock);
1085 if (propagate_mount_busy(real_mount(mnt), 2))
1087 br_write_unlock(&vfsmount_lock);
1088 up_read(&namespace_sem);
1092 EXPORT_SYMBOL(may_umount);
1094 void release_mounts(struct list_head *head)
1097 while (!list_empty(head)) {
1098 mnt = list_first_entry(head, struct mount, mnt_hash);
1099 list_del_init(&mnt->mnt_hash);
1100 if (mnt_has_parent(mnt)) {
1101 struct dentry *dentry;
1104 br_write_lock(&vfsmount_lock);
1105 dentry = mnt->mnt_mountpoint;
1106 m = mnt->mnt_parent;
1107 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1108 mnt->mnt_parent = mnt;
1110 br_write_unlock(&vfsmount_lock);
1119 * vfsmount lock must be held for write
1120 * namespace_sem must be held for write
1122 void umount_tree(struct mount *mnt, int propagate, struct list_head *kill)
1124 LIST_HEAD(tmp_list);
1127 for (p = mnt; p; p = next_mnt(p, mnt))
1128 list_move(&p->mnt_hash, &tmp_list);
1131 propagate_umount(&tmp_list);
1133 list_for_each_entry(p, &tmp_list, mnt_hash) {
1134 list_del_init(&p->mnt_expire);
1135 list_del_init(&p->mnt_list);
1136 __touch_mnt_namespace(p->mnt_ns);
1138 list_del_init(&p->mnt_child);
1139 if (mnt_has_parent(p)) {
1140 p->mnt_parent->mnt_ghosts++;
1141 dentry_reset_mounted(p->mnt_mountpoint);
1143 change_mnt_propagation(p, MS_PRIVATE);
1145 list_splice(&tmp_list, kill);
1148 static void shrink_submounts(struct mount *mnt, struct list_head *umounts);
1150 static int do_umount(struct mount *mnt, int flags)
1152 struct super_block *sb = mnt->mnt.mnt_sb;
1154 LIST_HEAD(umount_list);
1156 retval = security_sb_umount(&mnt->mnt, flags);
1161 * Allow userspace to request a mountpoint be expired rather than
1162 * unmounting unconditionally. Unmount only happens if:
1163 * (1) the mark is already set (the mark is cleared by mntput())
1164 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1166 if (flags & MNT_EXPIRE) {
1167 if (&mnt->mnt == current->fs->root.mnt ||
1168 flags & (MNT_FORCE | MNT_DETACH))
1172 * probably don't strictly need the lock here if we examined
1173 * all race cases, but it's a slowpath.
1175 br_write_lock(&vfsmount_lock);
1176 if (mnt_get_count(mnt) != 2) {
1177 br_write_unlock(&vfsmount_lock);
1180 br_write_unlock(&vfsmount_lock);
1182 if (!xchg(&mnt->mnt_expiry_mark, 1))
1187 * If we may have to abort operations to get out of this
1188 * mount, and they will themselves hold resources we must
1189 * allow the fs to do things. In the Unix tradition of
1190 * 'Gee thats tricky lets do it in userspace' the umount_begin
1191 * might fail to complete on the first run through as other tasks
1192 * must return, and the like. Thats for the mount program to worry
1193 * about for the moment.
1196 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1197 sb->s_op->umount_begin(sb);
1201 * No sense to grab the lock for this test, but test itself looks
1202 * somewhat bogus. Suggestions for better replacement?
1203 * Ho-hum... In principle, we might treat that as umount + switch
1204 * to rootfs. GC would eventually take care of the old vfsmount.
1205 * Actually it makes sense, especially if rootfs would contain a
1206 * /reboot - static binary that would close all descriptors and
1207 * call reboot(9). Then init(8) could umount root and exec /reboot.
1209 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1211 * Special case for "unmounting" root ...
1212 * we just try to remount it readonly.
1214 down_write(&sb->s_umount);
1215 if (!(sb->s_flags & MS_RDONLY))
1216 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1217 up_write(&sb->s_umount);
1221 down_write(&namespace_sem);
1222 br_write_lock(&vfsmount_lock);
1225 if (!(flags & MNT_DETACH))
1226 shrink_submounts(mnt, &umount_list);
1229 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
1230 if (!list_empty(&mnt->mnt_list))
1231 umount_tree(mnt, 1, &umount_list);
1234 br_write_unlock(&vfsmount_lock);
1235 up_write(&namespace_sem);
1236 release_mounts(&umount_list);
1241 * Is the caller allowed to modify his namespace?
1243 static inline bool may_mount(void)
1245 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1249 * Now umount can handle mount points as well as block devices.
1250 * This is important for filesystems which use unnamed block devices.
1252 * We now support a flag for forced unmount like the other 'big iron'
1253 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1256 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1261 int lookup_flags = 0;
1263 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1269 if (!(flags & UMOUNT_NOFOLLOW))
1270 lookup_flags |= LOOKUP_FOLLOW;
1272 retval = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1275 mnt = real_mount(path.mnt);
1277 if (path.dentry != path.mnt->mnt_root)
1279 if (!check_mnt(mnt))
1282 retval = do_umount(mnt, flags);
1284 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1286 mntput_no_expire(mnt);
1291 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1294 * The 2.0 compatible umount. No flags.
1296 SYSCALL_DEFINE1(oldumount, char __user *, name)
1298 return sys_umount(name, 0);
1303 static bool mnt_ns_loop(struct path *path)
1305 /* Could bind mounting the mount namespace inode cause a
1306 * mount namespace loop?
1308 struct inode *inode = path->dentry->d_inode;
1309 struct proc_inode *ei;
1310 struct mnt_namespace *mnt_ns;
1312 if (!proc_ns_inode(inode))
1316 if (ei->ns_ops != &mntns_operations)
1320 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1323 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1326 struct mount *res, *p, *q, *r;
1329 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
1330 return ERR_PTR(-EINVAL);
1332 res = q = clone_mnt(mnt, dentry, flag);
1336 q->mnt_mountpoint = mnt->mnt_mountpoint;
1339 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1341 if (!is_subdir(r->mnt_mountpoint, dentry))
1344 for (s = r; s; s = next_mnt(s, r)) {
1345 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
1346 s = skip_mnt_tree(s);
1349 while (p != s->mnt_parent) {
1355 path.dentry = p->mnt_mountpoint;
1356 q = clone_mnt(p, p->mnt.mnt_root, flag);
1359 br_write_lock(&vfsmount_lock);
1360 list_add_tail(&q->mnt_list, &res->mnt_list);
1361 attach_mnt(q, &path);
1362 br_write_unlock(&vfsmount_lock);
1368 LIST_HEAD(umount_list);
1369 br_write_lock(&vfsmount_lock);
1370 umount_tree(res, 0, &umount_list);
1371 br_write_unlock(&vfsmount_lock);
1372 release_mounts(&umount_list);
1377 /* Caller should check returned pointer for errors */
1379 struct vfsmount *collect_mounts(struct path *path)
1382 down_write(&namespace_sem);
1383 tree = copy_tree(real_mount(path->mnt), path->dentry,
1384 CL_COPY_ALL | CL_PRIVATE);
1385 up_write(&namespace_sem);
1391 void drop_collected_mounts(struct vfsmount *mnt)
1393 LIST_HEAD(umount_list);
1394 down_write(&namespace_sem);
1395 br_write_lock(&vfsmount_lock);
1396 umount_tree(real_mount(mnt), 0, &umount_list);
1397 br_write_unlock(&vfsmount_lock);
1398 up_write(&namespace_sem);
1399 release_mounts(&umount_list);
1402 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1403 struct vfsmount *root)
1406 int res = f(root, arg);
1409 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1410 res = f(&mnt->mnt, arg);
1417 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1421 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1422 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1423 mnt_release_group_id(p);
1427 static int invent_group_ids(struct mount *mnt, bool recurse)
1431 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1432 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1433 int err = mnt_alloc_group_id(p);
1435 cleanup_group_ids(mnt, p);
1445 * @source_mnt : mount tree to be attached
1446 * @nd : place the mount tree @source_mnt is attached
1447 * @parent_nd : if non-null, detach the source_mnt from its parent and
1448 * store the parent mount and mountpoint dentry.
1449 * (done when source_mnt is moved)
1451 * NOTE: in the table below explains the semantics when a source mount
1452 * of a given type is attached to a destination mount of a given type.
1453 * ---------------------------------------------------------------------------
1454 * | BIND MOUNT OPERATION |
1455 * |**************************************************************************
1456 * | source-->| shared | private | slave | unbindable |
1460 * |**************************************************************************
1461 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1463 * |non-shared| shared (+) | private | slave (*) | invalid |
1464 * ***************************************************************************
1465 * A bind operation clones the source mount and mounts the clone on the
1466 * destination mount.
1468 * (++) the cloned mount is propagated to all the mounts in the propagation
1469 * tree of the destination mount and the cloned mount is added to
1470 * the peer group of the source mount.
1471 * (+) the cloned mount is created under the destination mount and is marked
1472 * as shared. The cloned mount is added to the peer group of the source
1474 * (+++) the mount is propagated to all the mounts in the propagation tree
1475 * of the destination mount and the cloned mount is made slave
1476 * of the same master as that of the source mount. The cloned mount
1477 * is marked as 'shared and slave'.
1478 * (*) the cloned mount is made a slave of the same master as that of the
1481 * ---------------------------------------------------------------------------
1482 * | MOVE MOUNT OPERATION |
1483 * |**************************************************************************
1484 * | source-->| shared | private | slave | unbindable |
1488 * |**************************************************************************
1489 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1491 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1492 * ***************************************************************************
1494 * (+) the mount is moved to the destination. And is then propagated to
1495 * all the mounts in the propagation tree of the destination mount.
1496 * (+*) the mount is moved to the destination.
1497 * (+++) the mount is moved to the destination and is then propagated to
1498 * all the mounts belonging to the destination mount's propagation tree.
1499 * the mount is marked as 'shared and slave'.
1500 * (*) the mount continues to be a slave at the new location.
1502 * if the source mount is a tree, the operations explained above is
1503 * applied to each mount in the tree.
1504 * Must be called without spinlocks held, since this function can sleep
1507 static int attach_recursive_mnt(struct mount *source_mnt,
1508 struct path *path, struct path *parent_path)
1510 LIST_HEAD(tree_list);
1511 struct mount *dest_mnt = real_mount(path->mnt);
1512 struct dentry *dest_dentry = path->dentry;
1513 struct mount *child, *p;
1516 if (IS_MNT_SHARED(dest_mnt)) {
1517 err = invent_group_ids(source_mnt, true);
1521 err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
1523 goto out_cleanup_ids;
1525 br_write_lock(&vfsmount_lock);
1527 if (IS_MNT_SHARED(dest_mnt)) {
1528 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1532 detach_mnt(source_mnt, parent_path);
1533 attach_mnt(source_mnt, path);
1534 touch_mnt_namespace(source_mnt->mnt_ns);
1536 mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
1537 commit_tree(source_mnt);
1540 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
1541 list_del_init(&child->mnt_hash);
1544 br_write_unlock(&vfsmount_lock);
1549 if (IS_MNT_SHARED(dest_mnt))
1550 cleanup_group_ids(source_mnt, NULL);
1555 static int lock_mount(struct path *path)
1557 struct vfsmount *mnt;
1559 mutex_lock(&path->dentry->d_inode->i_mutex);
1560 if (unlikely(cant_mount(path->dentry))) {
1561 mutex_unlock(&path->dentry->d_inode->i_mutex);
1564 down_write(&namespace_sem);
1565 mnt = lookup_mnt(path);
1568 up_write(&namespace_sem);
1569 mutex_unlock(&path->dentry->d_inode->i_mutex);
1572 path->dentry = dget(mnt->mnt_root);
1576 static void unlock_mount(struct path *path)
1578 up_write(&namespace_sem);
1579 mutex_unlock(&path->dentry->d_inode->i_mutex);
1582 static int graft_tree(struct mount *mnt, struct path *path)
1584 if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
1587 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1588 S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
1591 if (d_unlinked(path->dentry))
1594 return attach_recursive_mnt(mnt, path, NULL);
1598 * Sanity check the flags to change_mnt_propagation.
1601 static int flags_to_propagation_type(int flags)
1603 int type = flags & ~(MS_REC | MS_SILENT);
1605 /* Fail if any non-propagation flags are set */
1606 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1608 /* Only one propagation flag should be set */
1609 if (!is_power_of_2(type))
1615 * recursively change the type of the mountpoint.
1617 static int do_change_type(struct path *path, int flag)
1620 struct mount *mnt = real_mount(path->mnt);
1621 int recurse = flag & MS_REC;
1625 if (path->dentry != path->mnt->mnt_root)
1628 type = flags_to_propagation_type(flag);
1632 down_write(&namespace_sem);
1633 if (type == MS_SHARED) {
1634 err = invent_group_ids(mnt, recurse);
1639 br_write_lock(&vfsmount_lock);
1640 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1641 change_mnt_propagation(m, type);
1642 br_write_unlock(&vfsmount_lock);
1645 up_write(&namespace_sem);
1650 * do loopback mount.
1652 static int do_loopback(struct path *path, const char *old_name,
1655 LIST_HEAD(umount_list);
1656 struct path old_path;
1657 struct mount *mnt = NULL, *old;
1659 if (!old_name || !*old_name)
1661 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1666 if (mnt_ns_loop(&old_path))
1669 err = lock_mount(path);
1673 old = real_mount(old_path.mnt);
1676 if (IS_MNT_UNBINDABLE(old))
1679 if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old))
1683 mnt = copy_tree(old, old_path.dentry, 0);
1685 mnt = clone_mnt(old, old_path.dentry, 0);
1692 err = graft_tree(mnt, path);
1694 br_write_lock(&vfsmount_lock);
1695 umount_tree(mnt, 0, &umount_list);
1696 br_write_unlock(&vfsmount_lock);
1700 release_mounts(&umount_list);
1702 path_put(&old_path);
1706 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1709 int readonly_request = 0;
1711 if (ms_flags & MS_RDONLY)
1712 readonly_request = 1;
1713 if (readonly_request == __mnt_is_readonly(mnt))
1716 if (mnt->mnt_flags & MNT_LOCK_READONLY)
1719 if (readonly_request)
1720 error = mnt_make_readonly(real_mount(mnt));
1722 __mnt_unmake_readonly(real_mount(mnt));
1727 * change filesystem flags. dir should be a physical root of filesystem.
1728 * If you've mounted a non-root directory somewhere and want to do remount
1729 * on it - tough luck.
1731 static int do_remount(struct path *path, int flags, int mnt_flags,
1735 struct super_block *sb = path->mnt->mnt_sb;
1736 struct mount *mnt = real_mount(path->mnt);
1738 if (!check_mnt(mnt))
1741 if (path->dentry != path->mnt->mnt_root)
1744 err = security_sb_remount(sb, data);
1748 down_write(&sb->s_umount);
1749 if (flags & MS_BIND)
1750 err = change_mount_flags(path->mnt, flags);
1751 else if (!capable(CAP_SYS_ADMIN))
1754 err = do_remount_sb(sb, flags, data, 0);
1756 br_write_lock(&vfsmount_lock);
1757 mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
1758 mnt->mnt.mnt_flags = mnt_flags;
1759 br_write_unlock(&vfsmount_lock);
1761 up_write(&sb->s_umount);
1763 br_write_lock(&vfsmount_lock);
1764 touch_mnt_namespace(mnt->mnt_ns);
1765 br_write_unlock(&vfsmount_lock);
1770 static inline int tree_contains_unbindable(struct mount *mnt)
1773 for (p = mnt; p; p = next_mnt(p, mnt)) {
1774 if (IS_MNT_UNBINDABLE(p))
1780 static int do_move_mount(struct path *path, const char *old_name)
1782 struct path old_path, parent_path;
1786 if (!old_name || !*old_name)
1788 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1792 err = lock_mount(path);
1796 old = real_mount(old_path.mnt);
1797 p = real_mount(path->mnt);
1800 if (!check_mnt(p) || !check_mnt(old))
1803 if (d_unlinked(path->dentry))
1807 if (old_path.dentry != old_path.mnt->mnt_root)
1810 if (!mnt_has_parent(old))
1813 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1814 S_ISDIR(old_path.dentry->d_inode->i_mode))
1817 * Don't move a mount residing in a shared parent.
1819 if (IS_MNT_SHARED(old->mnt_parent))
1822 * Don't move a mount tree containing unbindable mounts to a destination
1823 * mount which is shared.
1825 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
1828 for (; mnt_has_parent(p); p = p->mnt_parent)
1832 err = attach_recursive_mnt(old, path, &parent_path);
1836 /* if the mount is moved, it should no longer be expire
1838 list_del_init(&old->mnt_expire);
1843 path_put(&parent_path);
1844 path_put(&old_path);
1848 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
1851 const char *subtype = strchr(fstype, '.');
1860 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
1862 if (!mnt->mnt_sb->s_subtype)
1868 return ERR_PTR(err);
1872 * add a mount into a namespace's mount tree
1874 static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
1878 mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
1880 err = lock_mount(path);
1885 if (unlikely(!check_mnt(real_mount(path->mnt)))) {
1886 /* that's acceptable only for automounts done in private ns */
1887 if (!(mnt_flags & MNT_SHRINKABLE))
1889 /* ... and for those we'd better have mountpoint still alive */
1890 if (!real_mount(path->mnt)->mnt_ns)
1894 /* Refuse the same filesystem on the same mount point */
1896 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
1897 path->mnt->mnt_root == path->dentry)
1901 if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
1904 newmnt->mnt.mnt_flags = mnt_flags;
1905 err = graft_tree(newmnt, path);
1913 * create a new mount for userspace and request it to be added into the
1916 static int do_new_mount(struct path *path, const char *fstype, int flags,
1917 int mnt_flags, const char *name, void *data)
1919 struct file_system_type *type;
1920 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
1921 struct vfsmount *mnt;
1927 type = get_fs_type(fstype);
1931 if (user_ns != &init_user_ns) {
1932 if (!(type->fs_flags & FS_USERNS_MOUNT)) {
1933 put_filesystem(type);
1936 /* Only in special cases allow devices from mounts
1937 * created outside the initial user namespace.
1939 if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
1941 mnt_flags |= MNT_NODEV;
1945 mnt = vfs_kern_mount(type, flags, name, data);
1946 if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
1947 !mnt->mnt_sb->s_subtype)
1948 mnt = fs_set_subtype(mnt, fstype);
1950 put_filesystem(type);
1952 return PTR_ERR(mnt);
1954 err = do_add_mount(real_mount(mnt), path, mnt_flags);
1960 int finish_automount(struct vfsmount *m, struct path *path)
1962 struct mount *mnt = real_mount(m);
1964 /* The new mount record should have at least 2 refs to prevent it being
1965 * expired before we get a chance to add it
1967 BUG_ON(mnt_get_count(mnt) < 2);
1969 if (m->mnt_sb == path->mnt->mnt_sb &&
1970 m->mnt_root == path->dentry) {
1975 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
1979 /* remove m from any expiration list it may be on */
1980 if (!list_empty(&mnt->mnt_expire)) {
1981 down_write(&namespace_sem);
1982 br_write_lock(&vfsmount_lock);
1983 list_del_init(&mnt->mnt_expire);
1984 br_write_unlock(&vfsmount_lock);
1985 up_write(&namespace_sem);
1993 * mnt_set_expiry - Put a mount on an expiration list
1994 * @mnt: The mount to list.
1995 * @expiry_list: The list to add the mount to.
1997 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
1999 down_write(&namespace_sem);
2000 br_write_lock(&vfsmount_lock);
2002 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2004 br_write_unlock(&vfsmount_lock);
2005 up_write(&namespace_sem);
2007 EXPORT_SYMBOL(mnt_set_expiry);
2010 * process a list of expirable mountpoints with the intent of discarding any
2011 * mountpoints that aren't in use and haven't been touched since last we came
2014 void mark_mounts_for_expiry(struct list_head *mounts)
2016 struct mount *mnt, *next;
2017 LIST_HEAD(graveyard);
2020 if (list_empty(mounts))
2023 down_write(&namespace_sem);
2024 br_write_lock(&vfsmount_lock);
2026 /* extract from the expiration list every vfsmount that matches the
2027 * following criteria:
2028 * - only referenced by its parent vfsmount
2029 * - still marked for expiry (marked on the last call here; marks are
2030 * cleared by mntput())
2032 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2033 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2034 propagate_mount_busy(mnt, 1))
2036 list_move(&mnt->mnt_expire, &graveyard);
2038 while (!list_empty(&graveyard)) {
2039 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2040 touch_mnt_namespace(mnt->mnt_ns);
2041 umount_tree(mnt, 1, &umounts);
2043 br_write_unlock(&vfsmount_lock);
2044 up_write(&namespace_sem);
2046 release_mounts(&umounts);
2049 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2052 * Ripoff of 'select_parent()'
2054 * search the list of submounts for a given mountpoint, and move any
2055 * shrinkable submounts to the 'graveyard' list.
2057 static int select_submounts(struct mount *parent, struct list_head *graveyard)
2059 struct mount *this_parent = parent;
2060 struct list_head *next;
2064 next = this_parent->mnt_mounts.next;
2066 while (next != &this_parent->mnt_mounts) {
2067 struct list_head *tmp = next;
2068 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2071 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2074 * Descend a level if the d_mounts list is non-empty.
2076 if (!list_empty(&mnt->mnt_mounts)) {
2081 if (!propagate_mount_busy(mnt, 1)) {
2082 list_move_tail(&mnt->mnt_expire, graveyard);
2087 * All done at this level ... ascend and resume the search
2089 if (this_parent != parent) {
2090 next = this_parent->mnt_child.next;
2091 this_parent = this_parent->mnt_parent;
2098 * process a list of expirable mountpoints with the intent of discarding any
2099 * submounts of a specific parent mountpoint
2101 * vfsmount_lock must be held for write
2103 static void shrink_submounts(struct mount *mnt, struct list_head *umounts)
2105 LIST_HEAD(graveyard);
2108 /* extract submounts of 'mountpoint' from the expiration list */
2109 while (select_submounts(mnt, &graveyard)) {
2110 while (!list_empty(&graveyard)) {
2111 m = list_first_entry(&graveyard, struct mount,
2113 touch_mnt_namespace(m->mnt_ns);
2114 umount_tree(m, 1, umounts);
2120 * Some copy_from_user() implementations do not return the exact number of
2121 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2122 * Note that this function differs from copy_from_user() in that it will oops
2123 * on bad values of `to', rather than returning a short copy.
2125 static long exact_copy_from_user(void *to, const void __user * from,
2129 const char __user *f = from;
2132 if (!access_ok(VERIFY_READ, from, n))
2136 if (__get_user(c, f)) {
2147 int copy_mount_options(const void __user * data, unsigned long *where)
2157 if (!(page = __get_free_page(GFP_KERNEL)))
2160 /* We only care that *some* data at the address the user
2161 * gave us is valid. Just in case, we'll zero
2162 * the remainder of the page.
2164 /* copy_from_user cannot cross TASK_SIZE ! */
2165 size = TASK_SIZE - (unsigned long)data;
2166 if (size > PAGE_SIZE)
2169 i = size - exact_copy_from_user((void *)page, data, size);
2175 memset((char *)page + i, 0, PAGE_SIZE - i);
2180 int copy_mount_string(const void __user *data, char **where)
2189 tmp = strndup_user(data, PAGE_SIZE);
2191 return PTR_ERR(tmp);
2198 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2199 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2201 * data is a (void *) that can point to any structure up to
2202 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2203 * information (or be NULL).
2205 * Pre-0.97 versions of mount() didn't have a flags word.
2206 * When the flags word was introduced its top half was required
2207 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2208 * Therefore, if this magic number is present, it carries no information
2209 * and must be discarded.
2211 long do_mount(const char *dev_name, const char *dir_name,
2212 const char *type_page, unsigned long flags, void *data_page)
2219 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2220 flags &= ~MS_MGC_MSK;
2222 /* Basic sanity checks */
2224 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2228 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2230 /* ... and get the mountpoint */
2231 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2235 retval = security_sb_mount(dev_name, &path,
2236 type_page, flags, data_page);
2243 /* Default to relatime unless overriden */
2244 if (!(flags & MS_NOATIME))
2245 mnt_flags |= MNT_RELATIME;
2247 /* Separate the per-mountpoint flags */
2248 if (flags & MS_NOSUID)
2249 mnt_flags |= MNT_NOSUID;
2250 if (flags & MS_NODEV)
2251 mnt_flags |= MNT_NODEV;
2252 if (flags & MS_NOEXEC)
2253 mnt_flags |= MNT_NOEXEC;
2254 if (flags & MS_NOATIME)
2255 mnt_flags |= MNT_NOATIME;
2256 if (flags & MS_NODIRATIME)
2257 mnt_flags |= MNT_NODIRATIME;
2258 if (flags & MS_STRICTATIME)
2259 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2260 if (flags & MS_RDONLY)
2261 mnt_flags |= MNT_READONLY;
2263 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2264 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2267 if (flags & MS_REMOUNT)
2268 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2270 else if (flags & MS_BIND)
2271 retval = do_loopback(&path, dev_name, flags & MS_REC);
2272 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2273 retval = do_change_type(&path, flags);
2274 else if (flags & MS_MOVE)
2275 retval = do_move_mount(&path, dev_name);
2277 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2278 dev_name, data_page);
2284 static void free_mnt_ns(struct mnt_namespace *ns)
2286 proc_free_inum(ns->proc_inum);
2287 put_user_ns(ns->user_ns);
2292 * Assign a sequence number so we can detect when we attempt to bind
2293 * mount a reference to an older mount namespace into the current
2294 * mount namespace, preventing reference counting loops. A 64bit
2295 * number incrementing at 10Ghz will take 12,427 years to wrap which
2296 * is effectively never, so we can ignore the possibility.
2298 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
2300 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
2302 struct mnt_namespace *new_ns;
2305 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2307 return ERR_PTR(-ENOMEM);
2308 ret = proc_alloc_inum(&new_ns->proc_inum);
2311 return ERR_PTR(ret);
2313 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
2314 atomic_set(&new_ns->count, 1);
2315 new_ns->root = NULL;
2316 INIT_LIST_HEAD(&new_ns->list);
2317 init_waitqueue_head(&new_ns->poll);
2319 new_ns->user_ns = get_user_ns(user_ns);
2324 * Allocate a new namespace structure and populate it with contents
2325 * copied from the namespace of the passed in task structure.
2327 static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
2328 struct user_namespace *user_ns, struct fs_struct *fs)
2330 struct mnt_namespace *new_ns;
2331 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2332 struct mount *p, *q;
2333 struct mount *old = mnt_ns->root;
2337 new_ns = alloc_mnt_ns(user_ns);
2341 down_write(&namespace_sem);
2342 /* First pass: copy the tree topology */
2343 copy_flags = CL_COPY_ALL | CL_EXPIRE;
2344 if (user_ns != mnt_ns->user_ns)
2345 copy_flags |= CL_SHARED_TO_SLAVE;
2346 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
2348 up_write(&namespace_sem);
2349 free_mnt_ns(new_ns);
2350 return ERR_CAST(new);
2353 br_write_lock(&vfsmount_lock);
2354 list_add_tail(&new_ns->list, &new->mnt_list);
2355 br_write_unlock(&vfsmount_lock);
2358 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2359 * as belonging to new namespace. We have already acquired a private
2360 * fs_struct, so tsk->fs->lock is not needed.
2367 if (&p->mnt == fs->root.mnt) {
2368 fs->root.mnt = mntget(&q->mnt);
2371 if (&p->mnt == fs->pwd.mnt) {
2372 fs->pwd.mnt = mntget(&q->mnt);
2376 p = next_mnt(p, old);
2377 q = next_mnt(q, new);
2379 up_write(&namespace_sem);
2389 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2390 struct user_namespace *user_ns, struct fs_struct *new_fs)
2392 struct mnt_namespace *new_ns;
2397 if (!(flags & CLONE_NEWNS))
2400 new_ns = dup_mnt_ns(ns, user_ns, new_fs);
2407 * create_mnt_ns - creates a private namespace and adds a root filesystem
2408 * @mnt: pointer to the new root filesystem mountpoint
2410 static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
2412 struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
2413 if (!IS_ERR(new_ns)) {
2414 struct mount *mnt = real_mount(m);
2415 mnt->mnt_ns = new_ns;
2417 list_add(&new_ns->list, &mnt->mnt_list);
2424 struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
2426 struct mnt_namespace *ns;
2427 struct super_block *s;
2431 ns = create_mnt_ns(mnt);
2433 return ERR_CAST(ns);
2435 err = vfs_path_lookup(mnt->mnt_root, mnt,
2436 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
2441 return ERR_PTR(err);
2443 /* trade a vfsmount reference for active sb one */
2444 s = path.mnt->mnt_sb;
2445 atomic_inc(&s->s_active);
2447 /* lock the sucker */
2448 down_write(&s->s_umount);
2449 /* ... and return the root of (sub)tree on it */
2452 EXPORT_SYMBOL(mount_subtree);
2454 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2455 char __user *, type, unsigned long, flags, void __user *, data)
2459 struct filename *kernel_dir;
2461 unsigned long data_page;
2463 ret = copy_mount_string(type, &kernel_type);
2467 kernel_dir = getname(dir_name);
2468 if (IS_ERR(kernel_dir)) {
2469 ret = PTR_ERR(kernel_dir);
2473 ret = copy_mount_string(dev_name, &kernel_dev);
2477 ret = copy_mount_options(data, &data_page);
2481 ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
2482 (void *) data_page);
2484 free_page(data_page);
2488 putname(kernel_dir);
2496 * Return true if path is reachable from root
2498 * namespace_sem or vfsmount_lock is held
2500 bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
2501 const struct path *root)
2503 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
2504 dentry = mnt->mnt_mountpoint;
2505 mnt = mnt->mnt_parent;
2507 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
2510 int path_is_under(struct path *path1, struct path *path2)
2513 br_read_lock(&vfsmount_lock);
2514 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
2515 br_read_unlock(&vfsmount_lock);
2518 EXPORT_SYMBOL(path_is_under);
2521 * pivot_root Semantics:
2522 * Moves the root file system of the current process to the directory put_old,
2523 * makes new_root as the new root file system of the current process, and sets
2524 * root/cwd of all processes which had them on the current root to new_root.
2527 * The new_root and put_old must be directories, and must not be on the
2528 * same file system as the current process root. The put_old must be
2529 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2530 * pointed to by put_old must yield the same directory as new_root. No other
2531 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2533 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2534 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2535 * in this situation.
2538 * - we don't move root/cwd if they are not at the root (reason: if something
2539 * cared enough to change them, it's probably wrong to force them elsewhere)
2540 * - it's okay to pick a root that isn't the root of a file system, e.g.
2541 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2542 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2545 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2546 const char __user *, put_old)
2548 struct path new, old, parent_path, root_parent, root;
2549 struct mount *new_mnt, *root_mnt;
2555 error = user_path_dir(new_root, &new);
2559 error = user_path_dir(put_old, &old);
2563 error = security_sb_pivotroot(&old, &new);
2567 get_fs_root(current->fs, &root);
2568 error = lock_mount(&old);
2573 new_mnt = real_mount(new.mnt);
2574 root_mnt = real_mount(root.mnt);
2575 if (IS_MNT_SHARED(real_mount(old.mnt)) ||
2576 IS_MNT_SHARED(new_mnt->mnt_parent) ||
2577 IS_MNT_SHARED(root_mnt->mnt_parent))
2579 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
2582 if (d_unlinked(new.dentry))
2584 if (d_unlinked(old.dentry))
2587 if (new.mnt == root.mnt ||
2588 old.mnt == root.mnt)
2589 goto out4; /* loop, on the same file system */
2591 if (root.mnt->mnt_root != root.dentry)
2592 goto out4; /* not a mountpoint */
2593 if (!mnt_has_parent(root_mnt))
2594 goto out4; /* not attached */
2595 if (new.mnt->mnt_root != new.dentry)
2596 goto out4; /* not a mountpoint */
2597 if (!mnt_has_parent(new_mnt))
2598 goto out4; /* not attached */
2599 /* make sure we can reach put_old from new_root */
2600 if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new))
2602 br_write_lock(&vfsmount_lock);
2603 detach_mnt(new_mnt, &parent_path);
2604 detach_mnt(root_mnt, &root_parent);
2605 /* mount old root on put_old */
2606 attach_mnt(root_mnt, &old);
2607 /* mount new_root on / */
2608 attach_mnt(new_mnt, &root_parent);
2609 touch_mnt_namespace(current->nsproxy->mnt_ns);
2610 br_write_unlock(&vfsmount_lock);
2611 chroot_fs_refs(&root, &new);
2616 path_put(&root_parent);
2617 path_put(&parent_path);
2629 static void __init init_mount_tree(void)
2631 struct vfsmount *mnt;
2632 struct mnt_namespace *ns;
2634 struct file_system_type *type;
2636 type = get_fs_type("rootfs");
2638 panic("Can't find rootfs type");
2639 mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
2640 put_filesystem(type);
2642 panic("Can't create rootfs");
2644 ns = create_mnt_ns(mnt);
2646 panic("Can't allocate initial namespace");
2648 init_task.nsproxy->mnt_ns = ns;
2652 root.dentry = mnt->mnt_root;
2654 set_fs_pwd(current->fs, &root);
2655 set_fs_root(current->fs, &root);
2658 void __init mnt_init(void)
2663 init_rwsem(&namespace_sem);
2665 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
2666 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2668 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2670 if (!mount_hashtable)
2671 panic("Failed to allocate mount hash table\n");
2673 printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);
2675 for (u = 0; u < HASH_SIZE; u++)
2676 INIT_LIST_HEAD(&mount_hashtable[u]);
2678 br_lock_init(&vfsmount_lock);
2682 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2684 fs_kobj = kobject_create_and_add("fs", NULL);
2686 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2691 void put_mnt_ns(struct mnt_namespace *ns)
2693 LIST_HEAD(umount_list);
2695 if (!atomic_dec_and_test(&ns->count))
2697 down_write(&namespace_sem);
2698 br_write_lock(&vfsmount_lock);
2699 umount_tree(ns->root, 0, &umount_list);
2700 br_write_unlock(&vfsmount_lock);
2701 up_write(&namespace_sem);
2702 release_mounts(&umount_list);
2706 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2708 struct vfsmount *mnt;
2709 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2712 * it is a longterm mount, don't release mnt until
2713 * we unmount before file sys is unregistered
2715 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
2719 EXPORT_SYMBOL_GPL(kern_mount_data);
2721 void kern_unmount(struct vfsmount *mnt)
2723 /* release long term mount so mount point can be released */
2724 if (!IS_ERR_OR_NULL(mnt)) {
2725 br_write_lock(&vfsmount_lock);
2726 real_mount(mnt)->mnt_ns = NULL;
2727 br_write_unlock(&vfsmount_lock);
2731 EXPORT_SYMBOL(kern_unmount);
2733 bool our_mnt(struct vfsmount *mnt)
2735 return check_mnt(real_mount(mnt));
2738 bool current_chrooted(void)
2740 /* Does the current process have a non-standard root */
2741 struct path ns_root;
2742 struct path fs_root;
2745 /* Find the namespace root */
2746 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
2747 ns_root.dentry = ns_root.mnt->mnt_root;
2749 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
2752 get_fs_root(current->fs, &fs_root);
2754 chrooted = !path_equal(&fs_root, &ns_root);
2762 static void *mntns_get(struct task_struct *task)
2764 struct mnt_namespace *ns = NULL;
2765 struct nsproxy *nsproxy;
2768 nsproxy = task_nsproxy(task);
2770 ns = nsproxy->mnt_ns;
2778 static void mntns_put(void *ns)
2783 static int mntns_install(struct nsproxy *nsproxy, void *ns)
2785 struct fs_struct *fs = current->fs;
2786 struct mnt_namespace *mnt_ns = ns;
2789 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
2790 !nsown_capable(CAP_SYS_CHROOT) ||
2791 !nsown_capable(CAP_SYS_ADMIN))
2798 put_mnt_ns(nsproxy->mnt_ns);
2799 nsproxy->mnt_ns = mnt_ns;
2802 root.mnt = &mnt_ns->root->mnt;
2803 root.dentry = mnt_ns->root->mnt.mnt_root;
2805 while(d_mountpoint(root.dentry) && follow_down_one(&root))
2808 /* Update the pwd and root */
2809 set_fs_pwd(fs, &root);
2810 set_fs_root(fs, &root);
2816 static unsigned int mntns_inum(void *ns)
2818 struct mnt_namespace *mnt_ns = ns;
2819 return mnt_ns->proc_inum;
2822 const struct proc_ns_operations mntns_operations = {
2824 .type = CLONE_NEWNS,
2827 .install = mntns_install,