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/slab.h>
13 #include <linux/sched.h>
14 #include <linux/spinlock.h>
15 #include <linux/percpu.h>
16 #include <linux/init.h>
17 #include <linux/kernel.h>
18 #include <linux/acct.h>
19 #include <linux/capability.h>
20 #include <linux/cpumask.h>
21 #include <linux/module.h>
22 #include <linux/sysfs.h>
23 #include <linux/seq_file.h>
24 #include <linux/mnt_namespace.h>
25 #include <linux/namei.h>
26 #include <linux/nsproxy.h>
27 #include <linux/security.h>
28 #include <linux/mount.h>
29 #include <linux/ramfs.h>
30 #include <linux/log2.h>
31 #include <linux/idr.h>
32 #include <linux/fs_struct.h>
33 #include <linux/fsnotify.h>
34 #include <asm/uaccess.h>
35 #include <asm/unistd.h>
39 #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
40 #define HASH_SIZE (1UL << HASH_SHIFT)
43 static DEFINE_IDA(mnt_id_ida);
44 static DEFINE_IDA(mnt_group_ida);
45 static DEFINE_SPINLOCK(mnt_id_lock);
46 static int mnt_id_start = 0;
47 static int mnt_group_start = 1;
49 static struct list_head *mount_hashtable __read_mostly;
50 static struct kmem_cache *mnt_cache __read_mostly;
51 static struct rw_semaphore namespace_sem;
54 struct kobject *fs_kobj;
55 EXPORT_SYMBOL_GPL(fs_kobj);
58 * vfsmount lock may be taken for read to prevent changes to the
59 * vfsmount hash, ie. during mountpoint lookups or walking back
62 * It should be taken for write in all cases where the vfsmount
63 * tree or hash is modified or when a vfsmount structure is modified.
65 DEFINE_BRLOCK(vfsmount_lock);
67 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
69 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
70 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
71 tmp = tmp + (tmp >> HASH_SHIFT);
72 return tmp & (HASH_SIZE - 1);
75 #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
78 * allocation is serialized by namespace_sem, but we need the spinlock to
79 * serialize with freeing.
81 static int mnt_alloc_id(struct vfsmount *mnt)
86 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
87 spin_lock(&mnt_id_lock);
88 res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
90 mnt_id_start = mnt->mnt_id + 1;
91 spin_unlock(&mnt_id_lock);
98 static void mnt_free_id(struct vfsmount *mnt)
100 int id = mnt->mnt_id;
101 spin_lock(&mnt_id_lock);
102 ida_remove(&mnt_id_ida, id);
103 if (mnt_id_start > id)
105 spin_unlock(&mnt_id_lock);
109 * Allocate a new peer group ID
111 * mnt_group_ida is protected by namespace_sem
113 static int mnt_alloc_group_id(struct mount *mnt)
117 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
120 res = ida_get_new_above(&mnt_group_ida,
122 &mnt->mnt.mnt_group_id);
124 mnt_group_start = mnt->mnt.mnt_group_id + 1;
130 * Release a peer group ID
132 void mnt_release_group_id(struct mount *mnt)
134 int id = mnt->mnt.mnt_group_id;
135 ida_remove(&mnt_group_ida, id);
136 if (mnt_group_start > id)
137 mnt_group_start = id;
138 mnt->mnt.mnt_group_id = 0;
142 * vfsmount lock must be held for read
144 static inline void mnt_add_count(struct vfsmount *mnt, int n)
147 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
156 * vfsmount lock must be held for write
158 unsigned int mnt_get_count(struct vfsmount *mnt)
161 unsigned int count = 0;
164 for_each_possible_cpu(cpu) {
165 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
170 return mnt->mnt_count;
174 static struct vfsmount *alloc_vfsmnt(const char *name)
176 struct mount *p = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
178 struct vfsmount *mnt = &p->mnt;
181 err = mnt_alloc_id(mnt);
186 mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
187 if (!mnt->mnt_devname)
192 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
194 goto out_free_devname;
196 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
199 mnt->mnt_writers = 0;
202 INIT_LIST_HEAD(&mnt->mnt_hash);
203 INIT_LIST_HEAD(&mnt->mnt_child);
204 INIT_LIST_HEAD(&mnt->mnt_mounts);
205 INIT_LIST_HEAD(&mnt->mnt_list);
206 INIT_LIST_HEAD(&mnt->mnt_expire);
207 INIT_LIST_HEAD(&mnt->mnt_share);
208 INIT_LIST_HEAD(&mnt->mnt_slave_list);
209 INIT_LIST_HEAD(&mnt->mnt_slave);
210 #ifdef CONFIG_FSNOTIFY
211 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
218 kfree(p->mnt.mnt_devname);
221 mnt_free_id(&p->mnt);
223 kmem_cache_free(mnt_cache, p);
228 * Most r/o checks on a fs are for operations that take
229 * discrete amounts of time, like a write() or unlink().
230 * We must keep track of when those operations start
231 * (for permission checks) and when they end, so that
232 * we can determine when writes are able to occur to
236 * __mnt_is_readonly: check whether a mount is read-only
237 * @mnt: the mount to check for its write status
239 * This shouldn't be used directly ouside of the VFS.
240 * It does not guarantee that the filesystem will stay
241 * r/w, just that it is right *now*. This can not and
242 * should not be used in place of IS_RDONLY(inode).
243 * mnt_want/drop_write() will _keep_ the filesystem
246 int __mnt_is_readonly(struct vfsmount *mnt)
248 if (mnt->mnt_flags & MNT_READONLY)
250 if (mnt->mnt_sb->s_flags & MS_RDONLY)
254 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
256 static inline void mnt_inc_writers(struct vfsmount *mnt)
259 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
265 static inline void mnt_dec_writers(struct vfsmount *mnt)
268 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
274 static unsigned int mnt_get_writers(struct vfsmount *mnt)
277 unsigned int count = 0;
280 for_each_possible_cpu(cpu) {
281 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
286 return mnt->mnt_writers;
291 * Most r/o checks on a fs are for operations that take
292 * discrete amounts of time, like a write() or unlink().
293 * We must keep track of when those operations start
294 * (for permission checks) and when they end, so that
295 * we can determine when writes are able to occur to
299 * mnt_want_write - get write access to a mount
300 * @mnt: the mount on which to take a write
302 * This tells the low-level filesystem that a write is
303 * about to be performed to it, and makes sure that
304 * writes are allowed before returning success. When
305 * the write operation is finished, mnt_drop_write()
306 * must be called. This is effectively a refcount.
308 int mnt_want_write(struct vfsmount *mnt)
313 mnt_inc_writers(mnt);
315 * The store to mnt_inc_writers must be visible before we pass
316 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
317 * incremented count after it has set MNT_WRITE_HOLD.
320 while (mnt->mnt_flags & MNT_WRITE_HOLD)
323 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
324 * be set to match its requirements. So we must not load that until
325 * MNT_WRITE_HOLD is cleared.
328 if (__mnt_is_readonly(mnt)) {
329 mnt_dec_writers(mnt);
337 EXPORT_SYMBOL_GPL(mnt_want_write);
340 * mnt_clone_write - get write access to a mount
341 * @mnt: the mount on which to take a write
343 * This is effectively like mnt_want_write, except
344 * it must only be used to take an extra write reference
345 * on a mountpoint that we already know has a write reference
346 * on it. This allows some optimisation.
348 * After finished, mnt_drop_write must be called as usual to
349 * drop the reference.
351 int mnt_clone_write(struct vfsmount *mnt)
353 /* superblock may be r/o */
354 if (__mnt_is_readonly(mnt))
357 mnt_inc_writers(mnt);
361 EXPORT_SYMBOL_GPL(mnt_clone_write);
364 * mnt_want_write_file - get write access to a file's mount
365 * @file: the file who's mount on which to take a write
367 * This is like mnt_want_write, but it takes a file and can
368 * do some optimisations if the file is open for write already
370 int mnt_want_write_file(struct file *file)
372 struct inode *inode = file->f_dentry->d_inode;
373 if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
374 return mnt_want_write(file->f_path.mnt);
376 return mnt_clone_write(file->f_path.mnt);
378 EXPORT_SYMBOL_GPL(mnt_want_write_file);
381 * mnt_drop_write - give up write access to a mount
382 * @mnt: the mount on which to give up write access
384 * Tells the low-level filesystem that we are done
385 * performing writes to it. Must be matched with
386 * mnt_want_write() call above.
388 void mnt_drop_write(struct vfsmount *mnt)
391 mnt_dec_writers(mnt);
394 EXPORT_SYMBOL_GPL(mnt_drop_write);
396 void mnt_drop_write_file(struct file *file)
398 mnt_drop_write(file->f_path.mnt);
400 EXPORT_SYMBOL(mnt_drop_write_file);
402 static int mnt_make_readonly(struct vfsmount *mnt)
406 br_write_lock(vfsmount_lock);
407 mnt->mnt_flags |= MNT_WRITE_HOLD;
409 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
410 * should be visible before we do.
415 * With writers on hold, if this value is zero, then there are
416 * definitely no active writers (although held writers may subsequently
417 * increment the count, they'll have to wait, and decrement it after
418 * seeing MNT_READONLY).
420 * It is OK to have counter incremented on one CPU and decremented on
421 * another: the sum will add up correctly. The danger would be when we
422 * sum up each counter, if we read a counter before it is incremented,
423 * but then read another CPU's count which it has been subsequently
424 * decremented from -- we would see more decrements than we should.
425 * MNT_WRITE_HOLD protects against this scenario, because
426 * mnt_want_write first increments count, then smp_mb, then spins on
427 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
428 * we're counting up here.
430 if (mnt_get_writers(mnt) > 0)
433 mnt->mnt_flags |= MNT_READONLY;
435 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
436 * that become unheld will see MNT_READONLY.
439 mnt->mnt_flags &= ~MNT_WRITE_HOLD;
440 br_write_unlock(vfsmount_lock);
444 static void __mnt_unmake_readonly(struct vfsmount *mnt)
446 br_write_lock(vfsmount_lock);
447 mnt->mnt_flags &= ~MNT_READONLY;
448 br_write_unlock(vfsmount_lock);
451 static void free_vfsmnt(struct vfsmount *mnt)
453 struct mount *p = real_mount(mnt);
454 kfree(mnt->mnt_devname);
457 free_percpu(mnt->mnt_pcp);
459 kmem_cache_free(mnt_cache, p);
463 * find the first or last mount at @dentry on vfsmount @mnt depending on
464 * @dir. If @dir is set return the first mount else return the last mount.
465 * vfsmount_lock must be held for read or write.
467 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
470 struct list_head *head = mount_hashtable + hash(mnt, dentry);
471 struct list_head *tmp = head;
472 struct mount *p, *found = NULL;
475 tmp = dir ? tmp->next : tmp->prev;
479 p = list_entry(tmp, struct mount, mnt.mnt_hash);
480 if (p->mnt.mnt_parent == mnt && p->mnt.mnt_mountpoint == dentry) {
489 * lookup_mnt increments the ref count before returning
490 * the vfsmount struct.
492 struct vfsmount *lookup_mnt(struct path *path)
494 struct mount *child_mnt;
496 br_read_lock(vfsmount_lock);
497 child_mnt = __lookup_mnt(path->mnt, path->dentry, 1);
499 mnt_add_count(child_mnt, 1);
500 br_read_unlock(vfsmount_lock);
501 return &child_mnt->mnt;
503 br_read_unlock(vfsmount_lock);
508 static inline int check_mnt(struct vfsmount *mnt)
510 return mnt->mnt_ns == current->nsproxy->mnt_ns;
514 * vfsmount lock must be held for write
516 static void touch_mnt_namespace(struct mnt_namespace *ns)
520 wake_up_interruptible(&ns->poll);
525 * vfsmount lock must be held for write
527 static void __touch_mnt_namespace(struct mnt_namespace *ns)
529 if (ns && ns->event != event) {
531 wake_up_interruptible(&ns->poll);
536 * Clear dentry's mounted state if it has no remaining mounts.
537 * vfsmount_lock must be held for write.
539 static void dentry_reset_mounted(struct dentry *dentry)
543 for (u = 0; u < HASH_SIZE; u++) {
546 list_for_each_entry(p, &mount_hashtable[u], mnt_hash) {
547 if (p->mnt_mountpoint == dentry)
551 spin_lock(&dentry->d_lock);
552 dentry->d_flags &= ~DCACHE_MOUNTED;
553 spin_unlock(&dentry->d_lock);
557 * vfsmount lock must be held for write
559 static void detach_mnt(struct mount *mnt, struct path *old_path)
561 old_path->dentry = mnt->mnt.mnt_mountpoint;
562 old_path->mnt = mnt->mnt.mnt_parent;
563 mnt->mnt.mnt_parent = &mnt->mnt;
564 mnt->mnt.mnt_mountpoint = mnt->mnt.mnt_root;
565 list_del_init(&mnt->mnt.mnt_child);
566 list_del_init(&mnt->mnt.mnt_hash);
567 dentry_reset_mounted(old_path->dentry);
571 * vfsmount lock must be held for write
573 void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
574 struct vfsmount *child_mnt)
576 child_mnt->mnt_parent = mntget(mnt);
577 child_mnt->mnt_mountpoint = dget(dentry);
578 spin_lock(&dentry->d_lock);
579 dentry->d_flags |= DCACHE_MOUNTED;
580 spin_unlock(&dentry->d_lock);
584 * vfsmount lock must be held for write
586 static void attach_mnt(struct mount *mnt, struct path *path)
588 mnt_set_mountpoint(path->mnt, path->dentry, &mnt->mnt);
589 list_add_tail(&mnt->mnt.mnt_hash, mount_hashtable +
590 hash(path->mnt, path->dentry));
591 list_add_tail(&mnt->mnt.mnt_child, &path->mnt->mnt_mounts);
594 static inline void __mnt_make_longterm(struct vfsmount *mnt)
597 atomic_inc(&mnt->mnt_longterm);
601 /* needs vfsmount lock for write */
602 static inline void __mnt_make_shortterm(struct vfsmount *mnt)
605 atomic_dec(&mnt->mnt_longterm);
610 * vfsmount lock must be held for write
612 static void commit_tree(struct mount *mnt)
614 struct vfsmount *parent = mnt->mnt.mnt_parent;
617 struct mnt_namespace *n = parent->mnt_ns;
619 BUG_ON(parent == &mnt->mnt);
621 list_add_tail(&head, &mnt->mnt.mnt_list);
622 list_for_each_entry(m, &head, mnt_list) {
624 __mnt_make_longterm(m);
627 list_splice(&head, n->list.prev);
629 list_add_tail(&mnt->mnt.mnt_hash, mount_hashtable +
630 hash(parent, mnt->mnt.mnt_mountpoint));
631 list_add_tail(&mnt->mnt.mnt_child, &parent->mnt_mounts);
632 touch_mnt_namespace(n);
635 static struct mount *next_mnt(struct mount *p, struct vfsmount *root)
637 struct list_head *next = p->mnt.mnt_mounts.next;
638 if (next == &p->mnt.mnt_mounts) {
642 next = p->mnt.mnt_child.next;
643 if (next != &p->mnt.mnt_parent->mnt_mounts)
645 p = real_mount(p->mnt.mnt_parent);
648 return list_entry(next, struct mount, mnt.mnt_child);
651 static struct mount *skip_mnt_tree(struct mount *p)
653 struct list_head *prev = p->mnt.mnt_mounts.prev;
654 while (prev != &p->mnt.mnt_mounts) {
655 p = list_entry(prev, struct mount, mnt.mnt_child);
656 prev = p->mnt.mnt_mounts.prev;
662 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
664 struct vfsmount *mnt;
668 return ERR_PTR(-ENODEV);
670 mnt = alloc_vfsmnt(name);
672 return ERR_PTR(-ENOMEM);
674 if (flags & MS_KERNMOUNT)
675 mnt->mnt_flags = MNT_INTERNAL;
677 root = mount_fs(type, flags, name, data);
680 return ERR_CAST(root);
683 mnt->mnt_root = root;
684 mnt->mnt_sb = root->d_sb;
685 mnt->mnt_mountpoint = mnt->mnt_root;
686 mnt->mnt_parent = mnt;
689 EXPORT_SYMBOL_GPL(vfs_kern_mount);
691 static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
694 struct super_block *sb = old->mnt_sb;
695 struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
698 if (flag & (CL_SLAVE | CL_PRIVATE))
699 mnt->mnt_group_id = 0; /* not a peer of original */
701 mnt->mnt_group_id = old->mnt_group_id;
703 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
704 int err = mnt_alloc_group_id(real_mount(mnt));
709 mnt->mnt_flags = old->mnt_flags & ~MNT_WRITE_HOLD;
710 atomic_inc(&sb->s_active);
712 mnt->mnt_root = dget(root);
713 mnt->mnt_mountpoint = mnt->mnt_root;
714 mnt->mnt_parent = mnt;
716 if (flag & CL_SLAVE) {
717 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
718 mnt->mnt_master = old;
719 CLEAR_MNT_SHARED(mnt);
720 } else if (!(flag & CL_PRIVATE)) {
721 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
722 list_add(&mnt->mnt_share, &old->mnt_share);
723 if (IS_MNT_SLAVE(old))
724 list_add(&mnt->mnt_slave, &old->mnt_slave);
725 mnt->mnt_master = old->mnt_master;
727 if (flag & CL_MAKE_SHARED)
730 /* stick the duplicate mount on the same expiry list
731 * as the original if that was on one */
732 if (flag & CL_EXPIRE) {
733 if (!list_empty(&old->mnt_expire))
734 list_add(&mnt->mnt_expire, &old->mnt_expire);
744 static inline void mntfree(struct vfsmount *mnt)
746 struct super_block *sb = mnt->mnt_sb;
749 * This probably indicates that somebody messed
750 * up a mnt_want/drop_write() pair. If this
751 * happens, the filesystem was probably unable
752 * to make r/w->r/o transitions.
755 * The locking used to deal with mnt_count decrement provides barriers,
756 * so mnt_get_writers() below is safe.
758 WARN_ON(mnt_get_writers(mnt));
759 fsnotify_vfsmount_delete(mnt);
762 deactivate_super(sb);
765 static void mntput_no_expire(struct vfsmount *mnt)
769 br_read_lock(vfsmount_lock);
770 if (likely(atomic_read(&mnt->mnt_longterm))) {
771 mnt_add_count(mnt, -1);
772 br_read_unlock(vfsmount_lock);
775 br_read_unlock(vfsmount_lock);
777 br_write_lock(vfsmount_lock);
778 mnt_add_count(mnt, -1);
779 if (mnt_get_count(mnt)) {
780 br_write_unlock(vfsmount_lock);
784 mnt_add_count(mnt, -1);
785 if (likely(mnt_get_count(mnt)))
787 br_write_lock(vfsmount_lock);
789 if (unlikely(mnt->mnt_pinned)) {
790 mnt_add_count(mnt, mnt->mnt_pinned + 1);
792 br_write_unlock(vfsmount_lock);
793 acct_auto_close_mnt(mnt);
796 br_write_unlock(vfsmount_lock);
800 void mntput(struct vfsmount *mnt)
803 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
804 if (unlikely(mnt->mnt_expiry_mark))
805 mnt->mnt_expiry_mark = 0;
806 mntput_no_expire(mnt);
809 EXPORT_SYMBOL(mntput);
811 struct vfsmount *mntget(struct vfsmount *mnt)
814 mnt_add_count(mnt, 1);
817 EXPORT_SYMBOL(mntget);
819 void mnt_pin(struct vfsmount *mnt)
821 br_write_lock(vfsmount_lock);
823 br_write_unlock(vfsmount_lock);
825 EXPORT_SYMBOL(mnt_pin);
827 void mnt_unpin(struct vfsmount *mnt)
829 br_write_lock(vfsmount_lock);
830 if (mnt->mnt_pinned) {
831 mnt_add_count(mnt, 1);
834 br_write_unlock(vfsmount_lock);
836 EXPORT_SYMBOL(mnt_unpin);
838 static inline void mangle(struct seq_file *m, const char *s)
840 seq_escape(m, s, " \t\n\\");
844 * Simple .show_options callback for filesystems which don't want to
845 * implement more complex mount option showing.
847 * See also save_mount_options().
849 int generic_show_options(struct seq_file *m, struct vfsmount *mnt)
854 options = rcu_dereference(mnt->mnt_sb->s_options);
856 if (options != NULL && options[0]) {
864 EXPORT_SYMBOL(generic_show_options);
867 * If filesystem uses generic_show_options(), this function should be
868 * called from the fill_super() callback.
870 * The .remount_fs callback usually needs to be handled in a special
871 * way, to make sure, that previous options are not overwritten if the
874 * Also note, that if the filesystem's .remount_fs function doesn't
875 * reset all options to their default value, but changes only newly
876 * given options, then the displayed options will not reflect reality
879 void save_mount_options(struct super_block *sb, char *options)
881 BUG_ON(sb->s_options);
882 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
884 EXPORT_SYMBOL(save_mount_options);
886 void replace_mount_options(struct super_block *sb, char *options)
888 char *old = sb->s_options;
889 rcu_assign_pointer(sb->s_options, options);
895 EXPORT_SYMBOL(replace_mount_options);
897 #ifdef CONFIG_PROC_FS
899 static void *m_start(struct seq_file *m, loff_t *pos)
901 struct proc_mounts *p = m->private;
903 down_read(&namespace_sem);
904 return seq_list_start(&p->ns->list, *pos);
907 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
909 struct proc_mounts *p = m->private;
911 return seq_list_next(v, &p->ns->list, pos);
914 static void m_stop(struct seq_file *m, void *v)
916 up_read(&namespace_sem);
919 int mnt_had_events(struct proc_mounts *p)
921 struct mnt_namespace *ns = p->ns;
924 br_read_lock(vfsmount_lock);
925 if (p->m.poll_event != ns->event) {
926 p->m.poll_event = ns->event;
929 br_read_unlock(vfsmount_lock);
934 struct proc_fs_info {
939 static int show_sb_opts(struct seq_file *m, struct super_block *sb)
941 static const struct proc_fs_info fs_info[] = {
942 { MS_SYNCHRONOUS, ",sync" },
943 { MS_DIRSYNC, ",dirsync" },
944 { MS_MANDLOCK, ",mand" },
947 const struct proc_fs_info *fs_infop;
949 for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
950 if (sb->s_flags & fs_infop->flag)
951 seq_puts(m, fs_infop->str);
954 return security_sb_show_options(m, sb);
957 static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
959 static const struct proc_fs_info mnt_info[] = {
960 { MNT_NOSUID, ",nosuid" },
961 { MNT_NODEV, ",nodev" },
962 { MNT_NOEXEC, ",noexec" },
963 { MNT_NOATIME, ",noatime" },
964 { MNT_NODIRATIME, ",nodiratime" },
965 { MNT_RELATIME, ",relatime" },
968 const struct proc_fs_info *fs_infop;
970 for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
971 if (mnt->mnt_flags & fs_infop->flag)
972 seq_puts(m, fs_infop->str);
976 static void show_type(struct seq_file *m, struct super_block *sb)
978 mangle(m, sb->s_type->name);
979 if (sb->s_subtype && sb->s_subtype[0]) {
981 mangle(m, sb->s_subtype);
985 static int show_vfsmnt(struct seq_file *m, void *v)
987 struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
989 struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
991 if (mnt->mnt_sb->s_op->show_devname) {
992 err = mnt->mnt_sb->s_op->show_devname(m, mnt);
996 mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
999 seq_path(m, &mnt_path, " \t\n\\");
1001 show_type(m, mnt->mnt_sb);
1002 seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
1003 err = show_sb_opts(m, mnt->mnt_sb);
1006 show_mnt_opts(m, mnt);
1007 if (mnt->mnt_sb->s_op->show_options)
1008 err = mnt->mnt_sb->s_op->show_options(m, mnt);
1009 seq_puts(m, " 0 0\n");
1014 const struct seq_operations mounts_op = {
1021 static int show_mountinfo(struct seq_file *m, void *v)
1023 struct proc_mounts *p = m->private;
1024 struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
1025 struct super_block *sb = mnt->mnt_sb;
1026 struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
1027 struct path root = p->root;
1030 seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id,
1031 MAJOR(sb->s_dev), MINOR(sb->s_dev));
1032 if (sb->s_op->show_path)
1033 err = sb->s_op->show_path(m, mnt);
1035 seq_dentry(m, mnt->mnt_root, " \t\n\\");
1040 /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
1041 err = seq_path_root(m, &mnt_path, &root, " \t\n\\");
1045 seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
1046 show_mnt_opts(m, mnt);
1048 /* Tagged fields ("foo:X" or "bar") */
1049 if (IS_MNT_SHARED(mnt))
1050 seq_printf(m, " shared:%i", mnt->mnt_group_id);
1051 if (IS_MNT_SLAVE(mnt)) {
1052 int master = mnt->mnt_master->mnt_group_id;
1053 int dom = get_dominating_id(mnt, &p->root);
1054 seq_printf(m, " master:%i", master);
1055 if (dom && dom != master)
1056 seq_printf(m, " propagate_from:%i", dom);
1058 if (IS_MNT_UNBINDABLE(mnt))
1059 seq_puts(m, " unbindable");
1061 /* Filesystem specific data */
1065 if (sb->s_op->show_devname)
1066 err = sb->s_op->show_devname(m, mnt);
1068 mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
1071 seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
1072 err = show_sb_opts(m, sb);
1075 if (sb->s_op->show_options)
1076 err = sb->s_op->show_options(m, mnt);
1082 const struct seq_operations mountinfo_op = {
1086 .show = show_mountinfo,
1089 static int show_vfsstat(struct seq_file *m, void *v)
1091 struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
1092 struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
1096 if (mnt->mnt_sb->s_op->show_devname) {
1097 seq_puts(m, "device ");
1098 err = mnt->mnt_sb->s_op->show_devname(m, mnt);
1100 if (mnt->mnt_devname) {
1101 seq_puts(m, "device ");
1102 mangle(m, mnt->mnt_devname);
1104 seq_puts(m, "no device");
1108 seq_puts(m, " mounted on ");
1109 seq_path(m, &mnt_path, " \t\n\\");
1112 /* file system type */
1113 seq_puts(m, "with fstype ");
1114 show_type(m, mnt->mnt_sb);
1116 /* optional statistics */
1117 if (mnt->mnt_sb->s_op->show_stats) {
1120 err = mnt->mnt_sb->s_op->show_stats(m, mnt);
1127 const struct seq_operations mountstats_op = {
1131 .show = show_vfsstat,
1133 #endif /* CONFIG_PROC_FS */
1136 * may_umount_tree - check if a mount tree is busy
1137 * @mnt: root of mount tree
1139 * This is called to check if a tree of mounts has any
1140 * open files, pwds, chroots or sub mounts that are
1143 int may_umount_tree(struct vfsmount *mnt)
1145 int actual_refs = 0;
1146 int minimum_refs = 0;
1150 /* write lock needed for mnt_get_count */
1151 br_write_lock(vfsmount_lock);
1152 for (p = real_mount(mnt); p; p = next_mnt(p, mnt)) {
1153 actual_refs += mnt_get_count(&p->mnt);
1156 br_write_unlock(vfsmount_lock);
1158 if (actual_refs > minimum_refs)
1164 EXPORT_SYMBOL(may_umount_tree);
1167 * may_umount - check if a mount point is busy
1168 * @mnt: root of mount
1170 * This is called to check if a mount point has any
1171 * open files, pwds, chroots or sub mounts. If the
1172 * mount has sub mounts this will return busy
1173 * regardless of whether the sub mounts are busy.
1175 * Doesn't take quota and stuff into account. IOW, in some cases it will
1176 * give false negatives. The main reason why it's here is that we need
1177 * a non-destructive way to look for easily umountable filesystems.
1179 int may_umount(struct vfsmount *mnt)
1182 down_read(&namespace_sem);
1183 br_write_lock(vfsmount_lock);
1184 if (propagate_mount_busy(mnt, 2))
1186 br_write_unlock(vfsmount_lock);
1187 up_read(&namespace_sem);
1191 EXPORT_SYMBOL(may_umount);
1193 void release_mounts(struct list_head *head)
1195 struct vfsmount *mnt;
1196 while (!list_empty(head)) {
1197 mnt = list_first_entry(head, struct vfsmount, mnt_hash);
1198 list_del_init(&mnt->mnt_hash);
1199 if (mnt_has_parent(mnt)) {
1200 struct dentry *dentry;
1203 br_write_lock(vfsmount_lock);
1204 dentry = mnt->mnt_mountpoint;
1205 m = mnt->mnt_parent;
1206 mnt->mnt_mountpoint = mnt->mnt_root;
1207 mnt->mnt_parent = mnt;
1209 br_write_unlock(vfsmount_lock);
1218 * vfsmount lock must be held for write
1219 * namespace_sem must be held for write
1221 void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
1223 LIST_HEAD(tmp_list);
1226 for (p = real_mount(mnt); p; p = next_mnt(p, mnt))
1227 list_move(&p->mnt.mnt_hash, &tmp_list);
1230 propagate_umount(&tmp_list);
1232 list_for_each_entry(p, &tmp_list, mnt.mnt_hash) {
1233 list_del_init(&p->mnt.mnt_expire);
1234 list_del_init(&p->mnt.mnt_list);
1235 __touch_mnt_namespace(p->mnt.mnt_ns);
1236 p->mnt.mnt_ns = NULL;
1237 __mnt_make_shortterm(&p->mnt);
1238 list_del_init(&p->mnt.mnt_child);
1239 if (mnt_has_parent(&p->mnt)) {
1240 p->mnt.mnt_parent->mnt_ghosts++;
1241 dentry_reset_mounted(p->mnt.mnt_mountpoint);
1243 change_mnt_propagation(&p->mnt, MS_PRIVATE);
1245 list_splice(&tmp_list, kill);
1248 static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts);
1250 static int do_umount(struct vfsmount *mnt, int flags)
1252 struct super_block *sb = mnt->mnt_sb;
1254 LIST_HEAD(umount_list);
1256 retval = security_sb_umount(mnt, flags);
1261 * Allow userspace to request a mountpoint be expired rather than
1262 * unmounting unconditionally. Unmount only happens if:
1263 * (1) the mark is already set (the mark is cleared by mntput())
1264 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1266 if (flags & MNT_EXPIRE) {
1267 if (mnt == current->fs->root.mnt ||
1268 flags & (MNT_FORCE | MNT_DETACH))
1272 * probably don't strictly need the lock here if we examined
1273 * all race cases, but it's a slowpath.
1275 br_write_lock(vfsmount_lock);
1276 if (mnt_get_count(mnt) != 2) {
1277 br_write_unlock(vfsmount_lock);
1280 br_write_unlock(vfsmount_lock);
1282 if (!xchg(&mnt->mnt_expiry_mark, 1))
1287 * If we may have to abort operations to get out of this
1288 * mount, and they will themselves hold resources we must
1289 * allow the fs to do things. In the Unix tradition of
1290 * 'Gee thats tricky lets do it in userspace' the umount_begin
1291 * might fail to complete on the first run through as other tasks
1292 * must return, and the like. Thats for the mount program to worry
1293 * about for the moment.
1296 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1297 sb->s_op->umount_begin(sb);
1301 * No sense to grab the lock for this test, but test itself looks
1302 * somewhat bogus. Suggestions for better replacement?
1303 * Ho-hum... In principle, we might treat that as umount + switch
1304 * to rootfs. GC would eventually take care of the old vfsmount.
1305 * Actually it makes sense, especially if rootfs would contain a
1306 * /reboot - static binary that would close all descriptors and
1307 * call reboot(9). Then init(8) could umount root and exec /reboot.
1309 if (mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1311 * Special case for "unmounting" root ...
1312 * we just try to remount it readonly.
1314 down_write(&sb->s_umount);
1315 if (!(sb->s_flags & MS_RDONLY))
1316 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1317 up_write(&sb->s_umount);
1321 down_write(&namespace_sem);
1322 br_write_lock(vfsmount_lock);
1325 if (!(flags & MNT_DETACH))
1326 shrink_submounts(mnt, &umount_list);
1329 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
1330 if (!list_empty(&mnt->mnt_list))
1331 umount_tree(mnt, 1, &umount_list);
1334 br_write_unlock(vfsmount_lock);
1335 up_write(&namespace_sem);
1336 release_mounts(&umount_list);
1341 * Now umount can handle mount points as well as block devices.
1342 * This is important for filesystems which use unnamed block devices.
1344 * We now support a flag for forced unmount like the other 'big iron'
1345 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1348 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1352 int lookup_flags = 0;
1354 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1357 if (!(flags & UMOUNT_NOFOLLOW))
1358 lookup_flags |= LOOKUP_FOLLOW;
1360 retval = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1364 if (path.dentry != path.mnt->mnt_root)
1366 if (!check_mnt(path.mnt))
1370 if (!capable(CAP_SYS_ADMIN))
1373 retval = do_umount(path.mnt, flags);
1375 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1377 mntput_no_expire(path.mnt);
1382 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1385 * The 2.0 compatible umount. No flags.
1387 SYSCALL_DEFINE1(oldumount, char __user *, name)
1389 return sys_umount(name, 0);
1394 static int mount_is_safe(struct path *path)
1396 if (capable(CAP_SYS_ADMIN))
1400 if (S_ISLNK(path->dentry->d_inode->i_mode))
1402 if (path->dentry->d_inode->i_mode & S_ISVTX) {
1403 if (current_uid() != path->dentry->d_inode->i_uid)
1406 if (inode_permission(path->dentry->d_inode, MAY_WRITE))
1412 struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
1415 struct vfsmount *res, *p, *q, *r;
1418 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
1421 res = q = clone_mnt(mnt, dentry, flag);
1424 q->mnt_mountpoint = mnt->mnt_mountpoint;
1427 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1429 if (!is_subdir(r->mnt_mountpoint, dentry))
1432 for (s = real_mount(r); s; s = next_mnt(s, r)) {
1433 if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(&s->mnt)) {
1434 s = skip_mnt_tree(s);
1437 while (p != s->mnt.mnt_parent) {
1443 path.dentry = p->mnt_mountpoint;
1444 q = clone_mnt(p, p->mnt_root, flag);
1447 br_write_lock(vfsmount_lock);
1448 list_add_tail(&q->mnt_list, &res->mnt_list);
1449 attach_mnt(real_mount(q), &path);
1450 br_write_unlock(vfsmount_lock);
1456 LIST_HEAD(umount_list);
1457 br_write_lock(vfsmount_lock);
1458 umount_tree(res, 0, &umount_list);
1459 br_write_unlock(vfsmount_lock);
1460 release_mounts(&umount_list);
1465 struct vfsmount *collect_mounts(struct path *path)
1467 struct vfsmount *tree;
1468 down_write(&namespace_sem);
1469 tree = copy_tree(path->mnt, path->dentry, CL_COPY_ALL | CL_PRIVATE);
1470 up_write(&namespace_sem);
1474 void drop_collected_mounts(struct vfsmount *mnt)
1476 LIST_HEAD(umount_list);
1477 down_write(&namespace_sem);
1478 br_write_lock(vfsmount_lock);
1479 umount_tree(mnt, 0, &umount_list);
1480 br_write_unlock(vfsmount_lock);
1481 up_write(&namespace_sem);
1482 release_mounts(&umount_list);
1485 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1486 struct vfsmount *root)
1488 struct vfsmount *mnt;
1489 int res = f(root, arg);
1492 list_for_each_entry(mnt, &root->mnt_list, mnt_list) {
1500 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1504 for (p = mnt; p != end; p = next_mnt(p, &mnt->mnt)) {
1505 if (p->mnt.mnt_group_id && !IS_MNT_SHARED(&p->mnt))
1506 mnt_release_group_id(p);
1510 static int invent_group_ids(struct mount *mnt, bool recurse)
1514 for (p = mnt; p; p = recurse ? next_mnt(p, &mnt->mnt) : NULL) {
1515 if (!p->mnt.mnt_group_id && !IS_MNT_SHARED(&p->mnt)) {
1516 int err = mnt_alloc_group_id(p);
1518 cleanup_group_ids(mnt, p);
1528 * @source_mnt : mount tree to be attached
1529 * @nd : place the mount tree @source_mnt is attached
1530 * @parent_nd : if non-null, detach the source_mnt from its parent and
1531 * store the parent mount and mountpoint dentry.
1532 * (done when source_mnt is moved)
1534 * NOTE: in the table below explains the semantics when a source mount
1535 * of a given type is attached to a destination mount of a given type.
1536 * ---------------------------------------------------------------------------
1537 * | BIND MOUNT OPERATION |
1538 * |**************************************************************************
1539 * | source-->| shared | private | slave | unbindable |
1543 * |**************************************************************************
1544 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1546 * |non-shared| shared (+) | private | slave (*) | invalid |
1547 * ***************************************************************************
1548 * A bind operation clones the source mount and mounts the clone on the
1549 * destination mount.
1551 * (++) the cloned mount is propagated to all the mounts in the propagation
1552 * tree of the destination mount and the cloned mount is added to
1553 * the peer group of the source mount.
1554 * (+) the cloned mount is created under the destination mount and is marked
1555 * as shared. The cloned mount is added to the peer group of the source
1557 * (+++) the mount is propagated to all the mounts in the propagation tree
1558 * of the destination mount and the cloned mount is made slave
1559 * of the same master as that of the source mount. The cloned mount
1560 * is marked as 'shared and slave'.
1561 * (*) the cloned mount is made a slave of the same master as that of the
1564 * ---------------------------------------------------------------------------
1565 * | MOVE MOUNT OPERATION |
1566 * |**************************************************************************
1567 * | source-->| shared | private | slave | unbindable |
1571 * |**************************************************************************
1572 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1574 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1575 * ***************************************************************************
1577 * (+) the mount is moved to the destination. And is then propagated to
1578 * all the mounts in the propagation tree of the destination mount.
1579 * (+*) the mount is moved to the destination.
1580 * (+++) the mount is moved to the destination and is then propagated to
1581 * all the mounts belonging to the destination mount's propagation tree.
1582 * the mount is marked as 'shared and slave'.
1583 * (*) the mount continues to be a slave at the new location.
1585 * if the source mount is a tree, the operations explained above is
1586 * applied to each mount in the tree.
1587 * Must be called without spinlocks held, since this function can sleep
1590 static int attach_recursive_mnt(struct mount *source_mnt,
1591 struct path *path, struct path *parent_path)
1593 LIST_HEAD(tree_list);
1594 struct vfsmount *dest_mnt = path->mnt;
1595 struct dentry *dest_dentry = path->dentry;
1596 struct mount *child, *p;
1599 if (IS_MNT_SHARED(dest_mnt)) {
1600 err = invent_group_ids(source_mnt, true);
1604 err = propagate_mnt(dest_mnt, dest_dentry, &source_mnt->mnt, &tree_list);
1606 goto out_cleanup_ids;
1608 br_write_lock(vfsmount_lock);
1610 if (IS_MNT_SHARED(dest_mnt)) {
1611 for (p = source_mnt; p; p = next_mnt(p, &source_mnt->mnt))
1612 set_mnt_shared(&p->mnt);
1615 detach_mnt(source_mnt, parent_path);
1616 attach_mnt(source_mnt, path);
1617 touch_mnt_namespace(parent_path->mnt->mnt_ns);
1619 mnt_set_mountpoint(dest_mnt, dest_dentry, &source_mnt->mnt);
1620 commit_tree(source_mnt);
1623 list_for_each_entry_safe(child, p, &tree_list, mnt.mnt_hash) {
1624 list_del_init(&child->mnt.mnt_hash);
1627 br_write_unlock(vfsmount_lock);
1632 if (IS_MNT_SHARED(dest_mnt))
1633 cleanup_group_ids(source_mnt, NULL);
1638 static int lock_mount(struct path *path)
1640 struct vfsmount *mnt;
1642 mutex_lock(&path->dentry->d_inode->i_mutex);
1643 if (unlikely(cant_mount(path->dentry))) {
1644 mutex_unlock(&path->dentry->d_inode->i_mutex);
1647 down_write(&namespace_sem);
1648 mnt = lookup_mnt(path);
1651 up_write(&namespace_sem);
1652 mutex_unlock(&path->dentry->d_inode->i_mutex);
1655 path->dentry = dget(mnt->mnt_root);
1659 static void unlock_mount(struct path *path)
1661 up_write(&namespace_sem);
1662 mutex_unlock(&path->dentry->d_inode->i_mutex);
1665 static int graft_tree(struct vfsmount *mnt, struct path *path)
1667 if (mnt->mnt_sb->s_flags & MS_NOUSER)
1670 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1671 S_ISDIR(mnt->mnt_root->d_inode->i_mode))
1674 if (d_unlinked(path->dentry))
1677 return attach_recursive_mnt(real_mount(mnt), path, NULL);
1681 * Sanity check the flags to change_mnt_propagation.
1684 static int flags_to_propagation_type(int flags)
1686 int type = flags & ~(MS_REC | MS_SILENT);
1688 /* Fail if any non-propagation flags are set */
1689 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1691 /* Only one propagation flag should be set */
1692 if (!is_power_of_2(type))
1698 * recursively change the type of the mountpoint.
1700 static int do_change_type(struct path *path, int flag)
1703 struct mount *mnt = real_mount(path->mnt);
1704 int recurse = flag & MS_REC;
1708 if (!capable(CAP_SYS_ADMIN))
1711 if (path->dentry != path->mnt->mnt_root)
1714 type = flags_to_propagation_type(flag);
1718 down_write(&namespace_sem);
1719 if (type == MS_SHARED) {
1720 err = invent_group_ids(mnt, recurse);
1725 br_write_lock(vfsmount_lock);
1726 for (m = mnt; m; m = (recurse ? next_mnt(m, &mnt->mnt) : NULL))
1727 change_mnt_propagation(&m->mnt, type);
1728 br_write_unlock(vfsmount_lock);
1731 up_write(&namespace_sem);
1736 * do loopback mount.
1738 static int do_loopback(struct path *path, char *old_name,
1741 LIST_HEAD(umount_list);
1742 struct path old_path;
1743 struct vfsmount *mnt = NULL;
1744 int err = mount_is_safe(path);
1747 if (!old_name || !*old_name)
1749 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1753 err = lock_mount(path);
1758 if (IS_MNT_UNBINDABLE(old_path.mnt))
1761 if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
1766 mnt = copy_tree(old_path.mnt, old_path.dentry, 0);
1768 mnt = clone_mnt(old_path.mnt, old_path.dentry, 0);
1773 err = graft_tree(mnt, path);
1775 br_write_lock(vfsmount_lock);
1776 umount_tree(mnt, 0, &umount_list);
1777 br_write_unlock(vfsmount_lock);
1781 release_mounts(&umount_list);
1783 path_put(&old_path);
1787 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1790 int readonly_request = 0;
1792 if (ms_flags & MS_RDONLY)
1793 readonly_request = 1;
1794 if (readonly_request == __mnt_is_readonly(mnt))
1797 if (readonly_request)
1798 error = mnt_make_readonly(mnt);
1800 __mnt_unmake_readonly(mnt);
1805 * change filesystem flags. dir should be a physical root of filesystem.
1806 * If you've mounted a non-root directory somewhere and want to do remount
1807 * on it - tough luck.
1809 static int do_remount(struct path *path, int flags, int mnt_flags,
1813 struct super_block *sb = path->mnt->mnt_sb;
1815 if (!capable(CAP_SYS_ADMIN))
1818 if (!check_mnt(path->mnt))
1821 if (path->dentry != path->mnt->mnt_root)
1824 err = security_sb_remount(sb, data);
1828 down_write(&sb->s_umount);
1829 if (flags & MS_BIND)
1830 err = change_mount_flags(path->mnt, flags);
1832 err = do_remount_sb(sb, flags, data, 0);
1834 br_write_lock(vfsmount_lock);
1835 mnt_flags |= path->mnt->mnt_flags & MNT_PROPAGATION_MASK;
1836 path->mnt->mnt_flags = mnt_flags;
1837 br_write_unlock(vfsmount_lock);
1839 up_write(&sb->s_umount);
1841 br_write_lock(vfsmount_lock);
1842 touch_mnt_namespace(path->mnt->mnt_ns);
1843 br_write_unlock(vfsmount_lock);
1848 static inline int tree_contains_unbindable(struct vfsmount *mnt)
1851 for (p = real_mount(mnt); p; p = next_mnt(p, mnt)) {
1852 if (IS_MNT_UNBINDABLE(&p->mnt))
1858 static int do_move_mount(struct path *path, char *old_name)
1860 struct path old_path, parent_path;
1864 if (!capable(CAP_SYS_ADMIN))
1866 if (!old_name || !*old_name)
1868 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1872 err = lock_mount(path);
1877 if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
1880 if (d_unlinked(path->dentry))
1884 if (old_path.dentry != old_path.mnt->mnt_root)
1887 old = real_mount(old_path.mnt);
1889 if (!mnt_has_parent(old_path.mnt))
1892 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1893 S_ISDIR(old_path.dentry->d_inode->i_mode))
1896 * Don't move a mount residing in a shared parent.
1898 if (IS_MNT_SHARED(old_path.mnt->mnt_parent))
1901 * Don't move a mount tree containing unbindable mounts to a destination
1902 * mount which is shared.
1904 if (IS_MNT_SHARED(path->mnt) &&
1905 tree_contains_unbindable(old_path.mnt))
1908 for (p = path->mnt; mnt_has_parent(p); p = p->mnt_parent)
1909 if (p == old_path.mnt)
1912 err = attach_recursive_mnt(old, path, &parent_path);
1916 /* if the mount is moved, it should no longer be expire
1918 list_del_init(&old_path.mnt->mnt_expire);
1923 path_put(&parent_path);
1924 path_put(&old_path);
1928 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
1931 const char *subtype = strchr(fstype, '.');
1940 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
1942 if (!mnt->mnt_sb->s_subtype)
1948 return ERR_PTR(err);
1951 static struct vfsmount *
1952 do_kern_mount(const char *fstype, int flags, const char *name, void *data)
1954 struct file_system_type *type = get_fs_type(fstype);
1955 struct vfsmount *mnt;
1957 return ERR_PTR(-ENODEV);
1958 mnt = vfs_kern_mount(type, flags, name, data);
1959 if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
1960 !mnt->mnt_sb->s_subtype)
1961 mnt = fs_set_subtype(mnt, fstype);
1962 put_filesystem(type);
1967 * add a mount into a namespace's mount tree
1969 static int do_add_mount(struct vfsmount *newmnt, struct path *path, int mnt_flags)
1973 mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
1975 err = lock_mount(path);
1980 if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt))
1983 /* Refuse the same filesystem on the same mount point */
1985 if (path->mnt->mnt_sb == newmnt->mnt_sb &&
1986 path->mnt->mnt_root == path->dentry)
1990 if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
1993 newmnt->mnt_flags = mnt_flags;
1994 err = graft_tree(newmnt, path);
2002 * create a new mount for userspace and request it to be added into the
2005 static int do_new_mount(struct path *path, char *type, int flags,
2006 int mnt_flags, char *name, void *data)
2008 struct vfsmount *mnt;
2014 /* we need capabilities... */
2015 if (!capable(CAP_SYS_ADMIN))
2018 mnt = do_kern_mount(type, flags, name, data);
2020 return PTR_ERR(mnt);
2022 err = do_add_mount(mnt, path, mnt_flags);
2028 int finish_automount(struct vfsmount *m, struct path *path)
2031 /* The new mount record should have at least 2 refs to prevent it being
2032 * expired before we get a chance to add it
2034 BUG_ON(mnt_get_count(m) < 2);
2036 if (m->mnt_sb == path->mnt->mnt_sb &&
2037 m->mnt_root == path->dentry) {
2042 err = do_add_mount(m, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2046 /* remove m from any expiration list it may be on */
2047 if (!list_empty(&m->mnt_expire)) {
2048 down_write(&namespace_sem);
2049 br_write_lock(vfsmount_lock);
2050 list_del_init(&m->mnt_expire);
2051 br_write_unlock(vfsmount_lock);
2052 up_write(&namespace_sem);
2060 * mnt_set_expiry - Put a mount on an expiration list
2061 * @mnt: The mount to list.
2062 * @expiry_list: The list to add the mount to.
2064 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2066 down_write(&namespace_sem);
2067 br_write_lock(vfsmount_lock);
2069 list_add_tail(&mnt->mnt_expire, expiry_list);
2071 br_write_unlock(vfsmount_lock);
2072 up_write(&namespace_sem);
2074 EXPORT_SYMBOL(mnt_set_expiry);
2077 * process a list of expirable mountpoints with the intent of discarding any
2078 * mountpoints that aren't in use and haven't been touched since last we came
2081 void mark_mounts_for_expiry(struct list_head *mounts)
2083 struct vfsmount *mnt, *next;
2084 LIST_HEAD(graveyard);
2087 if (list_empty(mounts))
2090 down_write(&namespace_sem);
2091 br_write_lock(vfsmount_lock);
2093 /* extract from the expiration list every vfsmount that matches the
2094 * following criteria:
2095 * - only referenced by its parent vfsmount
2096 * - still marked for expiry (marked on the last call here; marks are
2097 * cleared by mntput())
2099 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2100 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2101 propagate_mount_busy(mnt, 1))
2103 list_move(&mnt->mnt_expire, &graveyard);
2105 while (!list_empty(&graveyard)) {
2106 mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire);
2107 touch_mnt_namespace(mnt->mnt_ns);
2108 umount_tree(mnt, 1, &umounts);
2110 br_write_unlock(vfsmount_lock);
2111 up_write(&namespace_sem);
2113 release_mounts(&umounts);
2116 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2119 * Ripoff of 'select_parent()'
2121 * search the list of submounts for a given mountpoint, and move any
2122 * shrinkable submounts to the 'graveyard' list.
2124 static int select_submounts(struct vfsmount *parent, struct list_head *graveyard)
2126 struct vfsmount *this_parent = parent;
2127 struct list_head *next;
2131 next = this_parent->mnt_mounts.next;
2133 while (next != &this_parent->mnt_mounts) {
2134 struct list_head *tmp = next;
2135 struct vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child);
2138 if (!(mnt->mnt_flags & MNT_SHRINKABLE))
2141 * Descend a level if the d_mounts list is non-empty.
2143 if (!list_empty(&mnt->mnt_mounts)) {
2148 if (!propagate_mount_busy(mnt, 1)) {
2149 list_move_tail(&mnt->mnt_expire, graveyard);
2154 * All done at this level ... ascend and resume the search
2156 if (this_parent != parent) {
2157 next = this_parent->mnt_child.next;
2158 this_parent = this_parent->mnt_parent;
2165 * process a list of expirable mountpoints with the intent of discarding any
2166 * submounts of a specific parent mountpoint
2168 * vfsmount_lock must be held for write
2170 static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts)
2172 LIST_HEAD(graveyard);
2175 /* extract submounts of 'mountpoint' from the expiration list */
2176 while (select_submounts(mnt, &graveyard)) {
2177 while (!list_empty(&graveyard)) {
2178 m = list_first_entry(&graveyard, struct vfsmount,
2180 touch_mnt_namespace(m->mnt_ns);
2181 umount_tree(m, 1, umounts);
2187 * Some copy_from_user() implementations do not return the exact number of
2188 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2189 * Note that this function differs from copy_from_user() in that it will oops
2190 * on bad values of `to', rather than returning a short copy.
2192 static long exact_copy_from_user(void *to, const void __user * from,
2196 const char __user *f = from;
2199 if (!access_ok(VERIFY_READ, from, n))
2203 if (__get_user(c, f)) {
2214 int copy_mount_options(const void __user * data, unsigned long *where)
2224 if (!(page = __get_free_page(GFP_KERNEL)))
2227 /* We only care that *some* data at the address the user
2228 * gave us is valid. Just in case, we'll zero
2229 * the remainder of the page.
2231 /* copy_from_user cannot cross TASK_SIZE ! */
2232 size = TASK_SIZE - (unsigned long)data;
2233 if (size > PAGE_SIZE)
2236 i = size - exact_copy_from_user((void *)page, data, size);
2242 memset((char *)page + i, 0, PAGE_SIZE - i);
2247 int copy_mount_string(const void __user *data, char **where)
2256 tmp = strndup_user(data, PAGE_SIZE);
2258 return PTR_ERR(tmp);
2265 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2266 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2268 * data is a (void *) that can point to any structure up to
2269 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2270 * information (or be NULL).
2272 * Pre-0.97 versions of mount() didn't have a flags word.
2273 * When the flags word was introduced its top half was required
2274 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2275 * Therefore, if this magic number is present, it carries no information
2276 * and must be discarded.
2278 long do_mount(char *dev_name, char *dir_name, char *type_page,
2279 unsigned long flags, void *data_page)
2286 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2287 flags &= ~MS_MGC_MSK;
2289 /* Basic sanity checks */
2291 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2295 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2297 /* ... and get the mountpoint */
2298 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2302 retval = security_sb_mount(dev_name, &path,
2303 type_page, flags, data_page);
2307 /* Default to relatime unless overriden */
2308 if (!(flags & MS_NOATIME))
2309 mnt_flags |= MNT_RELATIME;
2311 /* Separate the per-mountpoint flags */
2312 if (flags & MS_NOSUID)
2313 mnt_flags |= MNT_NOSUID;
2314 if (flags & MS_NODEV)
2315 mnt_flags |= MNT_NODEV;
2316 if (flags & MS_NOEXEC)
2317 mnt_flags |= MNT_NOEXEC;
2318 if (flags & MS_NOATIME)
2319 mnt_flags |= MNT_NOATIME;
2320 if (flags & MS_NODIRATIME)
2321 mnt_flags |= MNT_NODIRATIME;
2322 if (flags & MS_STRICTATIME)
2323 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2324 if (flags & MS_RDONLY)
2325 mnt_flags |= MNT_READONLY;
2327 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2328 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2331 if (flags & MS_REMOUNT)
2332 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2334 else if (flags & MS_BIND)
2335 retval = do_loopback(&path, dev_name, flags & MS_REC);
2336 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2337 retval = do_change_type(&path, flags);
2338 else if (flags & MS_MOVE)
2339 retval = do_move_mount(&path, dev_name);
2341 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2342 dev_name, data_page);
2348 static struct mnt_namespace *alloc_mnt_ns(void)
2350 struct mnt_namespace *new_ns;
2352 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2354 return ERR_PTR(-ENOMEM);
2355 atomic_set(&new_ns->count, 1);
2356 new_ns->root = NULL;
2357 INIT_LIST_HEAD(&new_ns->list);
2358 init_waitqueue_head(&new_ns->poll);
2363 void mnt_make_longterm(struct vfsmount *mnt)
2365 __mnt_make_longterm(mnt);
2368 void mnt_make_shortterm(struct vfsmount *mnt)
2371 if (atomic_add_unless(&mnt->mnt_longterm, -1, 1))
2373 br_write_lock(vfsmount_lock);
2374 atomic_dec(&mnt->mnt_longterm);
2375 br_write_unlock(vfsmount_lock);
2380 * Allocate a new namespace structure and populate it with contents
2381 * copied from the namespace of the passed in task structure.
2383 static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
2384 struct fs_struct *fs)
2386 struct mnt_namespace *new_ns;
2387 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2388 struct mount *p, *q;
2390 new_ns = alloc_mnt_ns();
2394 down_write(&namespace_sem);
2395 /* First pass: copy the tree topology */
2396 new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root,
2397 CL_COPY_ALL | CL_EXPIRE);
2398 if (!new_ns->root) {
2399 up_write(&namespace_sem);
2401 return ERR_PTR(-ENOMEM);
2403 br_write_lock(vfsmount_lock);
2404 list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
2405 br_write_unlock(vfsmount_lock);
2408 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2409 * as belonging to new namespace. We have already acquired a private
2410 * fs_struct, so tsk->fs->lock is not needed.
2412 p = real_mount(mnt_ns->root);
2413 q = real_mount(new_ns->root);
2415 q->mnt.mnt_ns = new_ns;
2416 __mnt_make_longterm(&q->mnt);
2418 if (&p->mnt == fs->root.mnt) {
2419 fs->root.mnt = mntget(&q->mnt);
2420 __mnt_make_longterm(&q->mnt);
2421 mnt_make_shortterm(&p->mnt);
2424 if (&p->mnt == fs->pwd.mnt) {
2425 fs->pwd.mnt = mntget(&q->mnt);
2426 __mnt_make_longterm(&q->mnt);
2427 mnt_make_shortterm(&p->mnt);
2431 p = next_mnt(p, mnt_ns->root);
2432 q = next_mnt(q, new_ns->root);
2434 up_write(&namespace_sem);
2444 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2445 struct fs_struct *new_fs)
2447 struct mnt_namespace *new_ns;
2452 if (!(flags & CLONE_NEWNS))
2455 new_ns = dup_mnt_ns(ns, new_fs);
2462 * create_mnt_ns - creates a private namespace and adds a root filesystem
2463 * @mnt: pointer to the new root filesystem mountpoint
2465 static struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
2467 struct mnt_namespace *new_ns;
2469 new_ns = alloc_mnt_ns();
2470 if (!IS_ERR(new_ns)) {
2471 mnt->mnt_ns = new_ns;
2472 __mnt_make_longterm(mnt);
2474 list_add(&new_ns->list, &new_ns->root->mnt_list);
2481 struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
2483 struct mnt_namespace *ns;
2484 struct super_block *s;
2488 ns = create_mnt_ns(mnt);
2490 return ERR_CAST(ns);
2492 err = vfs_path_lookup(mnt->mnt_root, mnt,
2493 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
2498 return ERR_PTR(err);
2500 /* trade a vfsmount reference for active sb one */
2501 s = path.mnt->mnt_sb;
2502 atomic_inc(&s->s_active);
2504 /* lock the sucker */
2505 down_write(&s->s_umount);
2506 /* ... and return the root of (sub)tree on it */
2509 EXPORT_SYMBOL(mount_subtree);
2511 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2512 char __user *, type, unsigned long, flags, void __user *, data)
2518 unsigned long data_page;
2520 ret = copy_mount_string(type, &kernel_type);
2524 kernel_dir = getname(dir_name);
2525 if (IS_ERR(kernel_dir)) {
2526 ret = PTR_ERR(kernel_dir);
2530 ret = copy_mount_string(dev_name, &kernel_dev);
2534 ret = copy_mount_options(data, &data_page);
2538 ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags,
2539 (void *) data_page);
2541 free_page(data_page);
2545 putname(kernel_dir);
2553 * Return true if path is reachable from root
2555 * namespace_sem or vfsmount_lock is held
2557 bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,
2558 const struct path *root)
2560 while (mnt != root->mnt && mnt_has_parent(mnt)) {
2561 dentry = mnt->mnt_mountpoint;
2562 mnt = mnt->mnt_parent;
2564 return mnt == root->mnt && is_subdir(dentry, root->dentry);
2567 int path_is_under(struct path *path1, struct path *path2)
2570 br_read_lock(vfsmount_lock);
2571 res = is_path_reachable(path1->mnt, path1->dentry, path2);
2572 br_read_unlock(vfsmount_lock);
2575 EXPORT_SYMBOL(path_is_under);
2578 * pivot_root Semantics:
2579 * Moves the root file system of the current process to the directory put_old,
2580 * makes new_root as the new root file system of the current process, and sets
2581 * root/cwd of all processes which had them on the current root to new_root.
2584 * The new_root and put_old must be directories, and must not be on the
2585 * same file system as the current process root. The put_old must be
2586 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2587 * pointed to by put_old must yield the same directory as new_root. No other
2588 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2590 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2591 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2592 * in this situation.
2595 * - we don't move root/cwd if they are not at the root (reason: if something
2596 * cared enough to change them, it's probably wrong to force them elsewhere)
2597 * - it's okay to pick a root that isn't the root of a file system, e.g.
2598 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2599 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2602 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2603 const char __user *, put_old)
2605 struct path new, old, parent_path, root_parent, root;
2606 struct mount *new_mnt, *root_mnt;
2609 if (!capable(CAP_SYS_ADMIN))
2612 error = user_path_dir(new_root, &new);
2616 error = user_path_dir(put_old, &old);
2620 error = security_sb_pivotroot(&old, &new);
2624 get_fs_root(current->fs, &root);
2625 error = lock_mount(&old);
2630 new_mnt = real_mount(new.mnt);
2631 root_mnt = real_mount(root.mnt);
2632 if (IS_MNT_SHARED(old.mnt) ||
2633 IS_MNT_SHARED(new.mnt->mnt_parent) ||
2634 IS_MNT_SHARED(root.mnt->mnt_parent))
2636 if (!check_mnt(root.mnt) || !check_mnt(new.mnt))
2639 if (d_unlinked(new.dentry))
2641 if (d_unlinked(old.dentry))
2644 if (new.mnt == root.mnt ||
2645 old.mnt == root.mnt)
2646 goto out4; /* loop, on the same file system */
2648 if (root.mnt->mnt_root != root.dentry)
2649 goto out4; /* not a mountpoint */
2650 if (!mnt_has_parent(root.mnt))
2651 goto out4; /* not attached */
2652 if (new.mnt->mnt_root != new.dentry)
2653 goto out4; /* not a mountpoint */
2654 if (!mnt_has_parent(new.mnt))
2655 goto out4; /* not attached */
2656 /* make sure we can reach put_old from new_root */
2657 if (!is_path_reachable(old.mnt, old.dentry, &new))
2659 br_write_lock(vfsmount_lock);
2660 detach_mnt(new_mnt, &parent_path);
2661 detach_mnt(root_mnt, &root_parent);
2662 /* mount old root on put_old */
2663 attach_mnt(root_mnt, &old);
2664 /* mount new_root on / */
2665 attach_mnt(new_mnt, &root_parent);
2666 touch_mnt_namespace(current->nsproxy->mnt_ns);
2667 br_write_unlock(vfsmount_lock);
2668 chroot_fs_refs(&root, &new);
2673 path_put(&root_parent);
2674 path_put(&parent_path);
2686 static void __init init_mount_tree(void)
2688 struct vfsmount *mnt;
2689 struct mnt_namespace *ns;
2692 mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
2694 panic("Can't create rootfs");
2696 ns = create_mnt_ns(mnt);
2698 panic("Can't allocate initial namespace");
2700 init_task.nsproxy->mnt_ns = ns;
2703 root.mnt = ns->root;
2704 root.dentry = ns->root->mnt_root;
2706 set_fs_pwd(current->fs, &root);
2707 set_fs_root(current->fs, &root);
2710 void __init mnt_init(void)
2715 init_rwsem(&namespace_sem);
2717 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
2718 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2720 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2722 if (!mount_hashtable)
2723 panic("Failed to allocate mount hash table\n");
2725 printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);
2727 for (u = 0; u < HASH_SIZE; u++)
2728 INIT_LIST_HEAD(&mount_hashtable[u]);
2730 br_lock_init(vfsmount_lock);
2734 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2736 fs_kobj = kobject_create_and_add("fs", NULL);
2738 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2743 void put_mnt_ns(struct mnt_namespace *ns)
2745 LIST_HEAD(umount_list);
2747 if (!atomic_dec_and_test(&ns->count))
2749 down_write(&namespace_sem);
2750 br_write_lock(vfsmount_lock);
2751 umount_tree(ns->root, 0, &umount_list);
2752 br_write_unlock(vfsmount_lock);
2753 up_write(&namespace_sem);
2754 release_mounts(&umount_list);
2758 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2760 struct vfsmount *mnt;
2761 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2764 * it is a longterm mount, don't release mnt until
2765 * we unmount before file sys is unregistered
2767 mnt_make_longterm(mnt);
2771 EXPORT_SYMBOL_GPL(kern_mount_data);
2773 void kern_unmount(struct vfsmount *mnt)
2775 /* release long term mount so mount point can be released */
2776 if (!IS_ERR_OR_NULL(mnt)) {
2777 mnt_make_shortterm(mnt);
2781 EXPORT_SYMBOL(kern_unmount);
2783 bool our_mnt(struct vfsmount *mnt)
2785 return check_mnt(mnt);