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 vfsmount
*mnt
)
117 if (!ida_pre_get(&mnt_group_ida
, GFP_KERNEL
))
120 res
= ida_get_new_above(&mnt_group_ida
,
124 mnt_group_start
= mnt
->mnt_group_id
+ 1;
130 * Release a peer group ID
132 void mnt_release_group_id(struct vfsmount
*mnt
)
134 int id
= mnt
->mnt_group_id
;
135 ida_remove(&mnt_group_ida
, id
);
136 if (mnt_group_start
> id
)
137 mnt_group_start
= id
;
138 mnt
->mnt_group_id
= 0;
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
);
155 static inline void mnt_set_count(struct vfsmount
*mnt
, int n
)
158 this_cpu_write(mnt
->mnt_pcp
->mnt_count
, n
);
165 * vfsmount lock must be held for read
167 static inline void mnt_inc_count(struct vfsmount
*mnt
)
169 mnt_add_count(mnt
, 1);
173 * vfsmount lock must be held for read
175 static inline void mnt_dec_count(struct vfsmount
*mnt
)
177 mnt_add_count(mnt
, -1);
181 * vfsmount lock must be held for write
183 unsigned int mnt_get_count(struct vfsmount
*mnt
)
186 unsigned int count
= 0;
189 for_each_possible_cpu(cpu
) {
190 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_count
;
195 return mnt
->mnt_count
;
199 static struct vfsmount
*alloc_vfsmnt(const char *name
)
201 struct vfsmount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
205 err
= mnt_alloc_id(mnt
);
210 mnt
->mnt_devname
= kstrdup(name
, GFP_KERNEL
);
211 if (!mnt
->mnt_devname
)
216 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
218 goto out_free_devname
;
220 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
223 mnt
->mnt_writers
= 0;
226 INIT_LIST_HEAD(&mnt
->mnt_hash
);
227 INIT_LIST_HEAD(&mnt
->mnt_child
);
228 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
229 INIT_LIST_HEAD(&mnt
->mnt_list
);
230 INIT_LIST_HEAD(&mnt
->mnt_expire
);
231 INIT_LIST_HEAD(&mnt
->mnt_share
);
232 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
233 INIT_LIST_HEAD(&mnt
->mnt_slave
);
234 #ifdef CONFIG_FSNOTIFY
235 INIT_HLIST_HEAD(&mnt
->mnt_fsnotify_marks
);
242 kfree(mnt
->mnt_devname
);
247 kmem_cache_free(mnt_cache
, mnt
);
252 * Most r/o checks on a fs are for operations that take
253 * discrete amounts of time, like a write() or unlink().
254 * We must keep track of when those operations start
255 * (for permission checks) and when they end, so that
256 * we can determine when writes are able to occur to
260 * __mnt_is_readonly: check whether a mount is read-only
261 * @mnt: the mount to check for its write status
263 * This shouldn't be used directly ouside of the VFS.
264 * It does not guarantee that the filesystem will stay
265 * r/w, just that it is right *now*. This can not and
266 * should not be used in place of IS_RDONLY(inode).
267 * mnt_want/drop_write() will _keep_ the filesystem
270 int __mnt_is_readonly(struct vfsmount
*mnt
)
272 if (mnt
->mnt_flags
& MNT_READONLY
)
274 if (mnt
->mnt_sb
->s_flags
& MS_RDONLY
)
278 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
280 static inline void mnt_inc_writers(struct vfsmount
*mnt
)
283 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
289 static inline void mnt_dec_writers(struct vfsmount
*mnt
)
292 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
298 static unsigned int mnt_get_writers(struct vfsmount
*mnt
)
301 unsigned int count
= 0;
304 for_each_possible_cpu(cpu
) {
305 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_writers
;
310 return mnt
->mnt_writers
;
315 * Most r/o checks on a fs are for operations that take
316 * discrete amounts of time, like a write() or unlink().
317 * We must keep track of when those operations start
318 * (for permission checks) and when they end, so that
319 * we can determine when writes are able to occur to
323 * mnt_want_write - get write access to a mount
324 * @mnt: the mount on which to take a write
326 * This tells the low-level filesystem that a write is
327 * about to be performed to it, and makes sure that
328 * writes are allowed before returning success. When
329 * the write operation is finished, mnt_drop_write()
330 * must be called. This is effectively a refcount.
332 int mnt_want_write(struct vfsmount
*mnt
)
337 mnt_inc_writers(mnt
);
339 * The store to mnt_inc_writers must be visible before we pass
340 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
341 * incremented count after it has set MNT_WRITE_HOLD.
344 while (mnt
->mnt_flags
& MNT_WRITE_HOLD
)
347 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
348 * be set to match its requirements. So we must not load that until
349 * MNT_WRITE_HOLD is cleared.
352 if (__mnt_is_readonly(mnt
)) {
353 mnt_dec_writers(mnt
);
361 EXPORT_SYMBOL_GPL(mnt_want_write
);
364 * mnt_clone_write - get write access to a mount
365 * @mnt: the mount on which to take a write
367 * This is effectively like mnt_want_write, except
368 * it must only be used to take an extra write reference
369 * on a mountpoint that we already know has a write reference
370 * on it. This allows some optimisation.
372 * After finished, mnt_drop_write must be called as usual to
373 * drop the reference.
375 int mnt_clone_write(struct vfsmount
*mnt
)
377 /* superblock may be r/o */
378 if (__mnt_is_readonly(mnt
))
381 mnt_inc_writers(mnt
);
385 EXPORT_SYMBOL_GPL(mnt_clone_write
);
388 * mnt_want_write_file - get write access to a file's mount
389 * @file: the file who's mount on which to take a write
391 * This is like mnt_want_write, but it takes a file and can
392 * do some optimisations if the file is open for write already
394 int mnt_want_write_file(struct file
*file
)
396 struct inode
*inode
= file
->f_dentry
->d_inode
;
397 if (!(file
->f_mode
& FMODE_WRITE
) || special_file(inode
->i_mode
))
398 return mnt_want_write(file
->f_path
.mnt
);
400 return mnt_clone_write(file
->f_path
.mnt
);
402 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
405 * mnt_drop_write - give up write access to a mount
406 * @mnt: the mount on which to give up write access
408 * Tells the low-level filesystem that we are done
409 * performing writes to it. Must be matched with
410 * mnt_want_write() call above.
412 void mnt_drop_write(struct vfsmount
*mnt
)
415 mnt_dec_writers(mnt
);
418 EXPORT_SYMBOL_GPL(mnt_drop_write
);
420 static int mnt_make_readonly(struct vfsmount
*mnt
)
424 br_write_lock(vfsmount_lock
);
425 mnt
->mnt_flags
|= MNT_WRITE_HOLD
;
427 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
428 * should be visible before we do.
433 * With writers on hold, if this value is zero, then there are
434 * definitely no active writers (although held writers may subsequently
435 * increment the count, they'll have to wait, and decrement it after
436 * seeing MNT_READONLY).
438 * It is OK to have counter incremented on one CPU and decremented on
439 * another: the sum will add up correctly. The danger would be when we
440 * sum up each counter, if we read a counter before it is incremented,
441 * but then read another CPU's count which it has been subsequently
442 * decremented from -- we would see more decrements than we should.
443 * MNT_WRITE_HOLD protects against this scenario, because
444 * mnt_want_write first increments count, then smp_mb, then spins on
445 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
446 * we're counting up here.
448 if (mnt_get_writers(mnt
) > 0)
451 mnt
->mnt_flags
|= MNT_READONLY
;
453 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
454 * that become unheld will see MNT_READONLY.
457 mnt
->mnt_flags
&= ~MNT_WRITE_HOLD
;
458 br_write_unlock(vfsmount_lock
);
462 static void __mnt_unmake_readonly(struct vfsmount
*mnt
)
464 br_write_lock(vfsmount_lock
);
465 mnt
->mnt_flags
&= ~MNT_READONLY
;
466 br_write_unlock(vfsmount_lock
);
469 static void free_vfsmnt(struct vfsmount
*mnt
)
471 kfree(mnt
->mnt_devname
);
474 free_percpu(mnt
->mnt_pcp
);
476 kmem_cache_free(mnt_cache
, mnt
);
480 * find the first or last mount at @dentry on vfsmount @mnt depending on
481 * @dir. If @dir is set return the first mount else return the last mount.
482 * vfsmount_lock must be held for read or write.
484 struct vfsmount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
,
487 struct list_head
*head
= mount_hashtable
+ hash(mnt
, dentry
);
488 struct list_head
*tmp
= head
;
489 struct vfsmount
*p
, *found
= NULL
;
492 tmp
= dir
? tmp
->next
: tmp
->prev
;
496 p
= list_entry(tmp
, struct vfsmount
, mnt_hash
);
497 if (p
->mnt_parent
== mnt
&& p
->mnt_mountpoint
== dentry
) {
506 * lookup_mnt increments the ref count before returning
507 * the vfsmount struct.
509 struct vfsmount
*lookup_mnt(struct path
*path
)
511 struct vfsmount
*child_mnt
;
513 br_read_lock(vfsmount_lock
);
514 if ((child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
, 1)))
516 br_read_unlock(vfsmount_lock
);
520 static inline int check_mnt(struct vfsmount
*mnt
)
522 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
526 * vfsmount lock must be held for write
528 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
532 wake_up_interruptible(&ns
->poll
);
537 * vfsmount lock must be held for write
539 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
541 if (ns
&& ns
->event
!= event
) {
543 wake_up_interruptible(&ns
->poll
);
548 * Clear dentry's mounted state if it has no remaining mounts.
549 * vfsmount_lock must be held for write.
551 static void dentry_reset_mounted(struct vfsmount
*mnt
, struct dentry
*dentry
)
555 for (u
= 0; u
< HASH_SIZE
; u
++) {
558 list_for_each_entry(p
, &mount_hashtable
[u
], mnt_hash
) {
559 if (p
->mnt_mountpoint
== dentry
)
563 spin_lock(&dentry
->d_lock
);
564 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
565 spin_unlock(&dentry
->d_lock
);
569 * vfsmount lock must be held for write
571 static void detach_mnt(struct vfsmount
*mnt
, struct path
*old_path
)
573 old_path
->dentry
= mnt
->mnt_mountpoint
;
574 old_path
->mnt
= mnt
->mnt_parent
;
575 mnt
->mnt_parent
= mnt
;
576 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
577 list_del_init(&mnt
->mnt_child
);
578 list_del_init(&mnt
->mnt_hash
);
579 dentry_reset_mounted(old_path
->mnt
, old_path
->dentry
);
583 * vfsmount lock must be held for write
585 void mnt_set_mountpoint(struct vfsmount
*mnt
, struct dentry
*dentry
,
586 struct vfsmount
*child_mnt
)
588 child_mnt
->mnt_parent
= mntget(mnt
);
589 child_mnt
->mnt_mountpoint
= dget(dentry
);
590 spin_lock(&dentry
->d_lock
);
591 dentry
->d_flags
|= DCACHE_MOUNTED
;
592 spin_unlock(&dentry
->d_lock
);
596 * vfsmount lock must be held for write
598 static void attach_mnt(struct vfsmount
*mnt
, struct path
*path
)
600 mnt_set_mountpoint(path
->mnt
, path
->dentry
, mnt
);
601 list_add_tail(&mnt
->mnt_hash
, mount_hashtable
+
602 hash(path
->mnt
, path
->dentry
));
603 list_add_tail(&mnt
->mnt_child
, &path
->mnt
->mnt_mounts
);
606 static inline void __mnt_make_longterm(struct vfsmount
*mnt
)
609 atomic_inc(&mnt
->mnt_longterm
);
613 /* needs vfsmount lock for write */
614 static inline void __mnt_make_shortterm(struct vfsmount
*mnt
)
617 atomic_dec(&mnt
->mnt_longterm
);
622 * vfsmount lock must be held for write
624 static void commit_tree(struct vfsmount
*mnt
)
626 struct vfsmount
*parent
= mnt
->mnt_parent
;
629 struct mnt_namespace
*n
= parent
->mnt_ns
;
631 BUG_ON(parent
== mnt
);
633 list_add_tail(&head
, &mnt
->mnt_list
);
634 list_for_each_entry(m
, &head
, mnt_list
) {
636 __mnt_make_longterm(m
);
639 list_splice(&head
, n
->list
.prev
);
641 list_add_tail(&mnt
->mnt_hash
, mount_hashtable
+
642 hash(parent
, mnt
->mnt_mountpoint
));
643 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
644 touch_mnt_namespace(n
);
647 static struct vfsmount
*next_mnt(struct vfsmount
*p
, struct vfsmount
*root
)
649 struct list_head
*next
= p
->mnt_mounts
.next
;
650 if (next
== &p
->mnt_mounts
) {
654 next
= p
->mnt_child
.next
;
655 if (next
!= &p
->mnt_parent
->mnt_mounts
)
660 return list_entry(next
, struct vfsmount
, mnt_child
);
663 static struct vfsmount
*skip_mnt_tree(struct vfsmount
*p
)
665 struct list_head
*prev
= p
->mnt_mounts
.prev
;
666 while (prev
!= &p
->mnt_mounts
) {
667 p
= list_entry(prev
, struct vfsmount
, mnt_child
);
668 prev
= p
->mnt_mounts
.prev
;
674 vfs_kern_mount(struct file_system_type
*type
, int flags
, const char *name
, void *data
)
676 struct vfsmount
*mnt
;
680 return ERR_PTR(-ENODEV
);
682 mnt
= alloc_vfsmnt(name
);
684 return ERR_PTR(-ENOMEM
);
686 if (flags
& MS_KERNMOUNT
)
687 mnt
->mnt_flags
= MNT_INTERNAL
;
689 root
= mount_fs(type
, flags
, name
, data
);
692 return ERR_CAST(root
);
695 mnt
->mnt_root
= root
;
696 mnt
->mnt_sb
= root
->d_sb
;
697 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
698 mnt
->mnt_parent
= mnt
;
701 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
703 static struct vfsmount
*clone_mnt(struct vfsmount
*old
, struct dentry
*root
,
706 struct super_block
*sb
= old
->mnt_sb
;
707 struct vfsmount
*mnt
= alloc_vfsmnt(old
->mnt_devname
);
710 if (flag
& (CL_SLAVE
| CL_PRIVATE
))
711 mnt
->mnt_group_id
= 0; /* not a peer of original */
713 mnt
->mnt_group_id
= old
->mnt_group_id
;
715 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
716 int err
= mnt_alloc_group_id(mnt
);
721 mnt
->mnt_flags
= old
->mnt_flags
& ~MNT_WRITE_HOLD
;
722 atomic_inc(&sb
->s_active
);
724 mnt
->mnt_root
= dget(root
);
725 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
726 mnt
->mnt_parent
= mnt
;
728 if (flag
& CL_SLAVE
) {
729 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
730 mnt
->mnt_master
= old
;
731 CLEAR_MNT_SHARED(mnt
);
732 } else if (!(flag
& CL_PRIVATE
)) {
733 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
734 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
735 if (IS_MNT_SLAVE(old
))
736 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
737 mnt
->mnt_master
= old
->mnt_master
;
739 if (flag
& CL_MAKE_SHARED
)
742 /* stick the duplicate mount on the same expiry list
743 * as the original if that was on one */
744 if (flag
& CL_EXPIRE
) {
745 if (!list_empty(&old
->mnt_expire
))
746 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
756 static inline void mntfree(struct vfsmount
*mnt
)
758 struct super_block
*sb
= mnt
->mnt_sb
;
761 * This probably indicates that somebody messed
762 * up a mnt_want/drop_write() pair. If this
763 * happens, the filesystem was probably unable
764 * to make r/w->r/o transitions.
767 * The locking used to deal with mnt_count decrement provides barriers,
768 * so mnt_get_writers() below is safe.
770 WARN_ON(mnt_get_writers(mnt
));
771 fsnotify_vfsmount_delete(mnt
);
774 deactivate_super(sb
);
777 static void mntput_no_expire(struct vfsmount
*mnt
)
781 br_read_lock(vfsmount_lock
);
782 if (likely(atomic_read(&mnt
->mnt_longterm
))) {
784 br_read_unlock(vfsmount_lock
);
787 br_read_unlock(vfsmount_lock
);
789 br_write_lock(vfsmount_lock
);
791 if (mnt_get_count(mnt
)) {
792 br_write_unlock(vfsmount_lock
);
797 if (likely(mnt_get_count(mnt
)))
799 br_write_lock(vfsmount_lock
);
801 if (unlikely(mnt
->mnt_pinned
)) {
802 mnt_add_count(mnt
, mnt
->mnt_pinned
+ 1);
804 br_write_unlock(vfsmount_lock
);
805 acct_auto_close_mnt(mnt
);
808 br_write_unlock(vfsmount_lock
);
812 void mntput(struct vfsmount
*mnt
)
815 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
816 if (unlikely(mnt
->mnt_expiry_mark
))
817 mnt
->mnt_expiry_mark
= 0;
818 mntput_no_expire(mnt
);
821 EXPORT_SYMBOL(mntput
);
823 struct vfsmount
*mntget(struct vfsmount
*mnt
)
829 EXPORT_SYMBOL(mntget
);
831 void mnt_pin(struct vfsmount
*mnt
)
833 br_write_lock(vfsmount_lock
);
835 br_write_unlock(vfsmount_lock
);
837 EXPORT_SYMBOL(mnt_pin
);
839 void mnt_unpin(struct vfsmount
*mnt
)
841 br_write_lock(vfsmount_lock
);
842 if (mnt
->mnt_pinned
) {
846 br_write_unlock(vfsmount_lock
);
848 EXPORT_SYMBOL(mnt_unpin
);
850 static inline void mangle(struct seq_file
*m
, const char *s
)
852 seq_escape(m
, s
, " \t\n\\");
856 * Simple .show_options callback for filesystems which don't want to
857 * implement more complex mount option showing.
859 * See also save_mount_options().
861 int generic_show_options(struct seq_file
*m
, struct vfsmount
*mnt
)
866 options
= rcu_dereference(mnt
->mnt_sb
->s_options
);
868 if (options
!= NULL
&& options
[0]) {
876 EXPORT_SYMBOL(generic_show_options
);
879 * If filesystem uses generic_show_options(), this function should be
880 * called from the fill_super() callback.
882 * The .remount_fs callback usually needs to be handled in a special
883 * way, to make sure, that previous options are not overwritten if the
886 * Also note, that if the filesystem's .remount_fs function doesn't
887 * reset all options to their default value, but changes only newly
888 * given options, then the displayed options will not reflect reality
891 void save_mount_options(struct super_block
*sb
, char *options
)
893 BUG_ON(sb
->s_options
);
894 rcu_assign_pointer(sb
->s_options
, kstrdup(options
, GFP_KERNEL
));
896 EXPORT_SYMBOL(save_mount_options
);
898 void replace_mount_options(struct super_block
*sb
, char *options
)
900 char *old
= sb
->s_options
;
901 rcu_assign_pointer(sb
->s_options
, options
);
907 EXPORT_SYMBOL(replace_mount_options
);
909 #ifdef CONFIG_PROC_FS
911 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
913 struct proc_mounts
*p
= m
->private;
915 down_read(&namespace_sem
);
916 return seq_list_start(&p
->ns
->list
, *pos
);
919 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
921 struct proc_mounts
*p
= m
->private;
923 return seq_list_next(v
, &p
->ns
->list
, pos
);
926 static void m_stop(struct seq_file
*m
, void *v
)
928 up_read(&namespace_sem
);
931 int mnt_had_events(struct proc_mounts
*p
)
933 struct mnt_namespace
*ns
= p
->ns
;
936 br_read_lock(vfsmount_lock
);
937 if (p
->event
!= ns
->event
) {
938 p
->event
= ns
->event
;
941 br_read_unlock(vfsmount_lock
);
946 struct proc_fs_info
{
951 static int show_sb_opts(struct seq_file
*m
, struct super_block
*sb
)
953 static const struct proc_fs_info fs_info
[] = {
954 { MS_SYNCHRONOUS
, ",sync" },
955 { MS_DIRSYNC
, ",dirsync" },
956 { MS_MANDLOCK
, ",mand" },
959 const struct proc_fs_info
*fs_infop
;
961 for (fs_infop
= fs_info
; fs_infop
->flag
; fs_infop
++) {
962 if (sb
->s_flags
& fs_infop
->flag
)
963 seq_puts(m
, fs_infop
->str
);
966 return security_sb_show_options(m
, sb
);
969 static void show_mnt_opts(struct seq_file
*m
, struct vfsmount
*mnt
)
971 static const struct proc_fs_info mnt_info
[] = {
972 { MNT_NOSUID
, ",nosuid" },
973 { MNT_NODEV
, ",nodev" },
974 { MNT_NOEXEC
, ",noexec" },
975 { MNT_NOATIME
, ",noatime" },
976 { MNT_NODIRATIME
, ",nodiratime" },
977 { MNT_RELATIME
, ",relatime" },
980 const struct proc_fs_info
*fs_infop
;
982 for (fs_infop
= mnt_info
; fs_infop
->flag
; fs_infop
++) {
983 if (mnt
->mnt_flags
& fs_infop
->flag
)
984 seq_puts(m
, fs_infop
->str
);
988 static void show_type(struct seq_file
*m
, struct super_block
*sb
)
990 mangle(m
, sb
->s_type
->name
);
991 if (sb
->s_subtype
&& sb
->s_subtype
[0]) {
993 mangle(m
, sb
->s_subtype
);
997 static int show_vfsmnt(struct seq_file
*m
, void *v
)
999 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
1001 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
1003 if (mnt
->mnt_sb
->s_op
->show_devname
) {
1004 err
= mnt
->mnt_sb
->s_op
->show_devname(m
, mnt
);
1008 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
1011 seq_path(m
, &mnt_path
, " \t\n\\");
1013 show_type(m
, mnt
->mnt_sb
);
1014 seq_puts(m
, __mnt_is_readonly(mnt
) ? " ro" : " rw");
1015 err
= show_sb_opts(m
, mnt
->mnt_sb
);
1018 show_mnt_opts(m
, mnt
);
1019 if (mnt
->mnt_sb
->s_op
->show_options
)
1020 err
= mnt
->mnt_sb
->s_op
->show_options(m
, mnt
);
1021 seq_puts(m
, " 0 0\n");
1026 const struct seq_operations mounts_op
= {
1033 static int uuid_is_nil(u8
*uuid
)
1036 u8
*cp
= (u8
*)uuid
;
1038 for (i
= 0; i
< 16; i
++) {
1045 static int show_mountinfo(struct seq_file
*m
, void *v
)
1047 struct proc_mounts
*p
= m
->private;
1048 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
1049 struct super_block
*sb
= mnt
->mnt_sb
;
1050 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
1051 struct path root
= p
->root
;
1054 seq_printf(m
, "%i %i %u:%u ", mnt
->mnt_id
, mnt
->mnt_parent
->mnt_id
,
1055 MAJOR(sb
->s_dev
), MINOR(sb
->s_dev
));
1056 if (sb
->s_op
->show_path
)
1057 err
= sb
->s_op
->show_path(m
, mnt
);
1059 seq_dentry(m
, mnt
->mnt_root
, " \t\n\\");
1063 seq_path_root(m
, &mnt_path
, &root
, " \t\n\\");
1064 if (root
.mnt
!= p
->root
.mnt
|| root
.dentry
!= p
->root
.dentry
) {
1066 * Mountpoint is outside root, discard that one. Ugly,
1067 * but less so than trying to do that in iterator in a
1068 * race-free way (due to renames).
1072 seq_puts(m
, mnt
->mnt_flags
& MNT_READONLY
? " ro" : " rw");
1073 show_mnt_opts(m
, mnt
);
1075 /* Tagged fields ("foo:X" or "bar") */
1076 if (IS_MNT_SHARED(mnt
))
1077 seq_printf(m
, " shared:%i", mnt
->mnt_group_id
);
1078 if (IS_MNT_SLAVE(mnt
)) {
1079 int master
= mnt
->mnt_master
->mnt_group_id
;
1080 int dom
= get_dominating_id(mnt
, &p
->root
);
1081 seq_printf(m
, " master:%i", master
);
1082 if (dom
&& dom
!= master
)
1083 seq_printf(m
, " propagate_from:%i", dom
);
1085 if (IS_MNT_UNBINDABLE(mnt
))
1086 seq_puts(m
, " unbindable");
1088 if (!uuid_is_nil(mnt
->mnt_sb
->s_uuid
))
1089 /* print the uuid */
1090 seq_printf(m
, " uuid:%pU", mnt
->mnt_sb
->s_uuid
);
1092 /* Filesystem specific data */
1096 if (sb
->s_op
->show_devname
)
1097 err
= sb
->s_op
->show_devname(m
, mnt
);
1099 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
1102 seq_puts(m
, sb
->s_flags
& MS_RDONLY
? " ro" : " rw");
1103 err
= show_sb_opts(m
, sb
);
1106 if (sb
->s_op
->show_options
)
1107 err
= sb
->s_op
->show_options(m
, mnt
);
1113 const struct seq_operations mountinfo_op
= {
1117 .show
= show_mountinfo
,
1120 static int show_vfsstat(struct seq_file
*m
, void *v
)
1122 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
1123 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
1127 if (mnt
->mnt_sb
->s_op
->show_devname
) {
1128 err
= mnt
->mnt_sb
->s_op
->show_devname(m
, mnt
);
1130 if (mnt
->mnt_devname
) {
1131 seq_puts(m
, "device ");
1132 mangle(m
, mnt
->mnt_devname
);
1134 seq_puts(m
, "no device");
1138 seq_puts(m
, " mounted on ");
1139 seq_path(m
, &mnt_path
, " \t\n\\");
1142 /* file system type */
1143 seq_puts(m
, "with fstype ");
1144 show_type(m
, mnt
->mnt_sb
);
1146 /* optional statistics */
1147 if (mnt
->mnt_sb
->s_op
->show_stats
) {
1150 err
= mnt
->mnt_sb
->s_op
->show_stats(m
, mnt
);
1157 const struct seq_operations mountstats_op
= {
1161 .show
= show_vfsstat
,
1163 #endif /* CONFIG_PROC_FS */
1166 * may_umount_tree - check if a mount tree is busy
1167 * @mnt: root of mount tree
1169 * This is called to check if a tree of mounts has any
1170 * open files, pwds, chroots or sub mounts that are
1173 int may_umount_tree(struct vfsmount
*mnt
)
1175 int actual_refs
= 0;
1176 int minimum_refs
= 0;
1179 /* write lock needed for mnt_get_count */
1180 br_write_lock(vfsmount_lock
);
1181 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1182 actual_refs
+= mnt_get_count(p
);
1185 br_write_unlock(vfsmount_lock
);
1187 if (actual_refs
> minimum_refs
)
1193 EXPORT_SYMBOL(may_umount_tree
);
1196 * may_umount - check if a mount point is busy
1197 * @mnt: root of mount
1199 * This is called to check if a mount point has any
1200 * open files, pwds, chroots or sub mounts. If the
1201 * mount has sub mounts this will return busy
1202 * regardless of whether the sub mounts are busy.
1204 * Doesn't take quota and stuff into account. IOW, in some cases it will
1205 * give false negatives. The main reason why it's here is that we need
1206 * a non-destructive way to look for easily umountable filesystems.
1208 int may_umount(struct vfsmount
*mnt
)
1211 down_read(&namespace_sem
);
1212 br_write_lock(vfsmount_lock
);
1213 if (propagate_mount_busy(mnt
, 2))
1215 br_write_unlock(vfsmount_lock
);
1216 up_read(&namespace_sem
);
1220 EXPORT_SYMBOL(may_umount
);
1222 void release_mounts(struct list_head
*head
)
1224 struct vfsmount
*mnt
;
1225 while (!list_empty(head
)) {
1226 mnt
= list_first_entry(head
, struct vfsmount
, mnt_hash
);
1227 list_del_init(&mnt
->mnt_hash
);
1228 if (mnt
->mnt_parent
!= mnt
) {
1229 struct dentry
*dentry
;
1232 br_write_lock(vfsmount_lock
);
1233 dentry
= mnt
->mnt_mountpoint
;
1234 m
= mnt
->mnt_parent
;
1235 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
1236 mnt
->mnt_parent
= mnt
;
1238 br_write_unlock(vfsmount_lock
);
1247 * vfsmount lock must be held for write
1248 * namespace_sem must be held for write
1250 void umount_tree(struct vfsmount
*mnt
, int propagate
, struct list_head
*kill
)
1252 LIST_HEAD(tmp_list
);
1255 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
1256 list_move(&p
->mnt_hash
, &tmp_list
);
1259 propagate_umount(&tmp_list
);
1261 list_for_each_entry(p
, &tmp_list
, mnt_hash
) {
1262 list_del_init(&p
->mnt_expire
);
1263 list_del_init(&p
->mnt_list
);
1264 __touch_mnt_namespace(p
->mnt_ns
);
1266 __mnt_make_shortterm(p
);
1267 list_del_init(&p
->mnt_child
);
1268 if (p
->mnt_parent
!= p
) {
1269 p
->mnt_parent
->mnt_ghosts
++;
1270 dentry_reset_mounted(p
->mnt_parent
, p
->mnt_mountpoint
);
1272 change_mnt_propagation(p
, MS_PRIVATE
);
1274 list_splice(&tmp_list
, kill
);
1277 static void shrink_submounts(struct vfsmount
*mnt
, struct list_head
*umounts
);
1279 static int do_umount(struct vfsmount
*mnt
, int flags
)
1281 struct super_block
*sb
= mnt
->mnt_sb
;
1283 LIST_HEAD(umount_list
);
1285 retval
= security_sb_umount(mnt
, flags
);
1290 * Allow userspace to request a mountpoint be expired rather than
1291 * unmounting unconditionally. Unmount only happens if:
1292 * (1) the mark is already set (the mark is cleared by mntput())
1293 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1295 if (flags
& MNT_EXPIRE
) {
1296 if (mnt
== current
->fs
->root
.mnt
||
1297 flags
& (MNT_FORCE
| MNT_DETACH
))
1301 * probably don't strictly need the lock here if we examined
1302 * all race cases, but it's a slowpath.
1304 br_write_lock(vfsmount_lock
);
1305 if (mnt_get_count(mnt
) != 2) {
1306 br_write_unlock(vfsmount_lock
);
1309 br_write_unlock(vfsmount_lock
);
1311 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1316 * If we may have to abort operations to get out of this
1317 * mount, and they will themselves hold resources we must
1318 * allow the fs to do things. In the Unix tradition of
1319 * 'Gee thats tricky lets do it in userspace' the umount_begin
1320 * might fail to complete on the first run through as other tasks
1321 * must return, and the like. Thats for the mount program to worry
1322 * about for the moment.
1325 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1326 sb
->s_op
->umount_begin(sb
);
1330 * No sense to grab the lock for this test, but test itself looks
1331 * somewhat bogus. Suggestions for better replacement?
1332 * Ho-hum... In principle, we might treat that as umount + switch
1333 * to rootfs. GC would eventually take care of the old vfsmount.
1334 * Actually it makes sense, especially if rootfs would contain a
1335 * /reboot - static binary that would close all descriptors and
1336 * call reboot(9). Then init(8) could umount root and exec /reboot.
1338 if (mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1340 * Special case for "unmounting" root ...
1341 * we just try to remount it readonly.
1343 down_write(&sb
->s_umount
);
1344 if (!(sb
->s_flags
& MS_RDONLY
))
1345 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
1346 up_write(&sb
->s_umount
);
1350 down_write(&namespace_sem
);
1351 br_write_lock(vfsmount_lock
);
1354 if (!(flags
& MNT_DETACH
))
1355 shrink_submounts(mnt
, &umount_list
);
1358 if (flags
& MNT_DETACH
|| !propagate_mount_busy(mnt
, 2)) {
1359 if (!list_empty(&mnt
->mnt_list
))
1360 umount_tree(mnt
, 1, &umount_list
);
1363 br_write_unlock(vfsmount_lock
);
1364 up_write(&namespace_sem
);
1365 release_mounts(&umount_list
);
1370 * Now umount can handle mount points as well as block devices.
1371 * This is important for filesystems which use unnamed block devices.
1373 * We now support a flag for forced unmount like the other 'big iron'
1374 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1377 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1381 int lookup_flags
= 0;
1383 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1386 if (!(flags
& UMOUNT_NOFOLLOW
))
1387 lookup_flags
|= LOOKUP_FOLLOW
;
1389 retval
= user_path_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1393 if (path
.dentry
!= path
.mnt
->mnt_root
)
1395 if (!check_mnt(path
.mnt
))
1399 if (!capable(CAP_SYS_ADMIN
))
1402 retval
= do_umount(path
.mnt
, flags
);
1404 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1406 mntput_no_expire(path
.mnt
);
1411 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1414 * The 2.0 compatible umount. No flags.
1416 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1418 return sys_umount(name
, 0);
1423 static int mount_is_safe(struct path
*path
)
1425 if (capable(CAP_SYS_ADMIN
))
1429 if (S_ISLNK(path
->dentry
->d_inode
->i_mode
))
1431 if (path
->dentry
->d_inode
->i_mode
& S_ISVTX
) {
1432 if (current_uid() != path
->dentry
->d_inode
->i_uid
)
1435 if (inode_permission(path
->dentry
->d_inode
, MAY_WRITE
))
1441 struct vfsmount
*copy_tree(struct vfsmount
*mnt
, struct dentry
*dentry
,
1444 struct vfsmount
*res
, *p
, *q
, *r
, *s
;
1447 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(mnt
))
1450 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1453 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1456 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1457 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1460 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1461 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(s
)) {
1462 s
= skip_mnt_tree(s
);
1465 while (p
!= s
->mnt_parent
) {
1471 path
.dentry
= p
->mnt_mountpoint
;
1472 q
= clone_mnt(p
, p
->mnt_root
, flag
);
1475 br_write_lock(vfsmount_lock
);
1476 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1477 attach_mnt(q
, &path
);
1478 br_write_unlock(vfsmount_lock
);
1484 LIST_HEAD(umount_list
);
1485 br_write_lock(vfsmount_lock
);
1486 umount_tree(res
, 0, &umount_list
);
1487 br_write_unlock(vfsmount_lock
);
1488 release_mounts(&umount_list
);
1493 struct vfsmount
*collect_mounts(struct path
*path
)
1495 struct vfsmount
*tree
;
1496 down_write(&namespace_sem
);
1497 tree
= copy_tree(path
->mnt
, path
->dentry
, CL_COPY_ALL
| CL_PRIVATE
);
1498 up_write(&namespace_sem
);
1502 void drop_collected_mounts(struct vfsmount
*mnt
)
1504 LIST_HEAD(umount_list
);
1505 down_write(&namespace_sem
);
1506 br_write_lock(vfsmount_lock
);
1507 umount_tree(mnt
, 0, &umount_list
);
1508 br_write_unlock(vfsmount_lock
);
1509 up_write(&namespace_sem
);
1510 release_mounts(&umount_list
);
1513 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1514 struct vfsmount
*root
)
1516 struct vfsmount
*mnt
;
1517 int res
= f(root
, arg
);
1520 list_for_each_entry(mnt
, &root
->mnt_list
, mnt_list
) {
1528 static void cleanup_group_ids(struct vfsmount
*mnt
, struct vfsmount
*end
)
1532 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
1533 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
1534 mnt_release_group_id(p
);
1538 static int invent_group_ids(struct vfsmount
*mnt
, bool recurse
)
1542 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
1543 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
1544 int err
= mnt_alloc_group_id(p
);
1546 cleanup_group_ids(mnt
, p
);
1556 * @source_mnt : mount tree to be attached
1557 * @nd : place the mount tree @source_mnt is attached
1558 * @parent_nd : if non-null, detach the source_mnt from its parent and
1559 * store the parent mount and mountpoint dentry.
1560 * (done when source_mnt is moved)
1562 * NOTE: in the table below explains the semantics when a source mount
1563 * of a given type is attached to a destination mount of a given type.
1564 * ---------------------------------------------------------------------------
1565 * | BIND MOUNT OPERATION |
1566 * |**************************************************************************
1567 * | source-->| shared | private | slave | unbindable |
1571 * |**************************************************************************
1572 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1574 * |non-shared| shared (+) | private | slave (*) | invalid |
1575 * ***************************************************************************
1576 * A bind operation clones the source mount and mounts the clone on the
1577 * destination mount.
1579 * (++) the cloned mount is propagated to all the mounts in the propagation
1580 * tree of the destination mount and the cloned mount is added to
1581 * the peer group of the source mount.
1582 * (+) the cloned mount is created under the destination mount and is marked
1583 * as shared. The cloned mount is added to the peer group of the source
1585 * (+++) the mount is propagated to all the mounts in the propagation tree
1586 * of the destination mount and the cloned mount is made slave
1587 * of the same master as that of the source mount. The cloned mount
1588 * is marked as 'shared and slave'.
1589 * (*) the cloned mount is made a slave of the same master as that of the
1592 * ---------------------------------------------------------------------------
1593 * | MOVE MOUNT OPERATION |
1594 * |**************************************************************************
1595 * | source-->| shared | private | slave | unbindable |
1599 * |**************************************************************************
1600 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1602 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1603 * ***************************************************************************
1605 * (+) the mount is moved to the destination. And is then propagated to
1606 * all the mounts in the propagation tree of the destination mount.
1607 * (+*) the mount is moved to the destination.
1608 * (+++) the mount is moved to the destination and is then propagated to
1609 * all the mounts belonging to the destination mount's propagation tree.
1610 * the mount is marked as 'shared and slave'.
1611 * (*) the mount continues to be a slave at the new location.
1613 * if the source mount is a tree, the operations explained above is
1614 * applied to each mount in the tree.
1615 * Must be called without spinlocks held, since this function can sleep
1618 static int attach_recursive_mnt(struct vfsmount
*source_mnt
,
1619 struct path
*path
, struct path
*parent_path
)
1621 LIST_HEAD(tree_list
);
1622 struct vfsmount
*dest_mnt
= path
->mnt
;
1623 struct dentry
*dest_dentry
= path
->dentry
;
1624 struct vfsmount
*child
, *p
;
1627 if (IS_MNT_SHARED(dest_mnt
)) {
1628 err
= invent_group_ids(source_mnt
, true);
1632 err
= propagate_mnt(dest_mnt
, dest_dentry
, source_mnt
, &tree_list
);
1634 goto out_cleanup_ids
;
1636 br_write_lock(vfsmount_lock
);
1638 if (IS_MNT_SHARED(dest_mnt
)) {
1639 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
1643 detach_mnt(source_mnt
, parent_path
);
1644 attach_mnt(source_mnt
, path
);
1645 touch_mnt_namespace(parent_path
->mnt
->mnt_ns
);
1647 mnt_set_mountpoint(dest_mnt
, dest_dentry
, source_mnt
);
1648 commit_tree(source_mnt
);
1651 list_for_each_entry_safe(child
, p
, &tree_list
, mnt_hash
) {
1652 list_del_init(&child
->mnt_hash
);
1655 br_write_unlock(vfsmount_lock
);
1660 if (IS_MNT_SHARED(dest_mnt
))
1661 cleanup_group_ids(source_mnt
, NULL
);
1666 static int graft_tree(struct vfsmount
*mnt
, struct path
*path
)
1669 if (mnt
->mnt_sb
->s_flags
& MS_NOUSER
)
1672 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
1673 S_ISDIR(mnt
->mnt_root
->d_inode
->i_mode
))
1677 mutex_lock(&path
->dentry
->d_inode
->i_mutex
);
1678 if (cant_mount(path
->dentry
))
1681 if (!d_unlinked(path
->dentry
))
1682 err
= attach_recursive_mnt(mnt
, path
, NULL
);
1684 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1689 * Sanity check the flags to change_mnt_propagation.
1692 static int flags_to_propagation_type(int flags
)
1694 int type
= flags
& ~MS_REC
;
1696 /* Fail if any non-propagation flags are set */
1697 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
1699 /* Only one propagation flag should be set */
1700 if (!is_power_of_2(type
))
1706 * recursively change the type of the mountpoint.
1708 static int do_change_type(struct path
*path
, int flag
)
1710 struct vfsmount
*m
, *mnt
= path
->mnt
;
1711 int recurse
= flag
& MS_REC
;
1715 if (!capable(CAP_SYS_ADMIN
))
1718 if (path
->dentry
!= path
->mnt
->mnt_root
)
1721 type
= flags_to_propagation_type(flag
);
1725 down_write(&namespace_sem
);
1726 if (type
== MS_SHARED
) {
1727 err
= invent_group_ids(mnt
, recurse
);
1732 br_write_lock(vfsmount_lock
);
1733 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
1734 change_mnt_propagation(m
, type
);
1735 br_write_unlock(vfsmount_lock
);
1738 up_write(&namespace_sem
);
1743 * do loopback mount.
1745 static int do_loopback(struct path
*path
, char *old_name
,
1748 struct path old_path
;
1749 struct vfsmount
*mnt
= NULL
;
1750 int err
= mount_is_safe(path
);
1753 if (!old_name
|| !*old_name
)
1755 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
1759 down_write(&namespace_sem
);
1761 if (IS_MNT_UNBINDABLE(old_path
.mnt
))
1764 if (!check_mnt(path
->mnt
) || !check_mnt(old_path
.mnt
))
1769 mnt
= copy_tree(old_path
.mnt
, old_path
.dentry
, 0);
1771 mnt
= clone_mnt(old_path
.mnt
, old_path
.dentry
, 0);
1776 err
= graft_tree(mnt
, path
);
1778 LIST_HEAD(umount_list
);
1780 br_write_lock(vfsmount_lock
);
1781 umount_tree(mnt
, 0, &umount_list
);
1782 br_write_unlock(vfsmount_lock
);
1783 release_mounts(&umount_list
);
1787 up_write(&namespace_sem
);
1788 path_put(&old_path
);
1792 static int change_mount_flags(struct vfsmount
*mnt
, int ms_flags
)
1795 int readonly_request
= 0;
1797 if (ms_flags
& MS_RDONLY
)
1798 readonly_request
= 1;
1799 if (readonly_request
== __mnt_is_readonly(mnt
))
1802 if (readonly_request
)
1803 error
= mnt_make_readonly(mnt
);
1805 __mnt_unmake_readonly(mnt
);
1810 * change filesystem flags. dir should be a physical root of filesystem.
1811 * If you've mounted a non-root directory somewhere and want to do remount
1812 * on it - tough luck.
1814 static int do_remount(struct path
*path
, int flags
, int mnt_flags
,
1818 struct super_block
*sb
= path
->mnt
->mnt_sb
;
1820 if (!capable(CAP_SYS_ADMIN
))
1823 if (!check_mnt(path
->mnt
))
1826 if (path
->dentry
!= path
->mnt
->mnt_root
)
1829 err
= security_sb_remount(sb
, data
);
1833 down_write(&sb
->s_umount
);
1834 if (flags
& MS_BIND
)
1835 err
= change_mount_flags(path
->mnt
, flags
);
1837 err
= do_remount_sb(sb
, flags
, data
, 0);
1839 br_write_lock(vfsmount_lock
);
1840 mnt_flags
|= path
->mnt
->mnt_flags
& MNT_PROPAGATION_MASK
;
1841 path
->mnt
->mnt_flags
= mnt_flags
;
1842 br_write_unlock(vfsmount_lock
);
1844 up_write(&sb
->s_umount
);
1846 br_write_lock(vfsmount_lock
);
1847 touch_mnt_namespace(path
->mnt
->mnt_ns
);
1848 br_write_unlock(vfsmount_lock
);
1853 static inline int tree_contains_unbindable(struct vfsmount
*mnt
)
1856 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1857 if (IS_MNT_UNBINDABLE(p
))
1863 static int do_move_mount(struct path
*path
, char *old_name
)
1865 struct path old_path
, parent_path
;
1868 if (!capable(CAP_SYS_ADMIN
))
1870 if (!old_name
|| !*old_name
)
1872 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
1876 down_write(&namespace_sem
);
1877 err
= follow_down(path
, true);
1882 if (!check_mnt(path
->mnt
) || !check_mnt(old_path
.mnt
))
1886 mutex_lock(&path
->dentry
->d_inode
->i_mutex
);
1887 if (cant_mount(path
->dentry
))
1890 if (d_unlinked(path
->dentry
))
1894 if (old_path
.dentry
!= old_path
.mnt
->mnt_root
)
1897 if (old_path
.mnt
== old_path
.mnt
->mnt_parent
)
1900 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
1901 S_ISDIR(old_path
.dentry
->d_inode
->i_mode
))
1904 * Don't move a mount residing in a shared parent.
1906 if (old_path
.mnt
->mnt_parent
&&
1907 IS_MNT_SHARED(old_path
.mnt
->mnt_parent
))
1910 * Don't move a mount tree containing unbindable mounts to a destination
1911 * mount which is shared.
1913 if (IS_MNT_SHARED(path
->mnt
) &&
1914 tree_contains_unbindable(old_path
.mnt
))
1917 for (p
= path
->mnt
; p
->mnt_parent
!= p
; p
= p
->mnt_parent
)
1918 if (p
== old_path
.mnt
)
1921 err
= attach_recursive_mnt(old_path
.mnt
, path
, &parent_path
);
1925 /* if the mount is moved, it should no longer be expire
1927 list_del_init(&old_path
.mnt
->mnt_expire
);
1929 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1931 up_write(&namespace_sem
);
1933 path_put(&parent_path
);
1934 path_put(&old_path
);
1938 static struct vfsmount
*fs_set_subtype(struct vfsmount
*mnt
, const char *fstype
)
1941 const char *subtype
= strchr(fstype
, '.');
1950 mnt
->mnt_sb
->s_subtype
= kstrdup(subtype
, GFP_KERNEL
);
1952 if (!mnt
->mnt_sb
->s_subtype
)
1958 return ERR_PTR(err
);
1962 do_kern_mount(const char *fstype
, int flags
, const char *name
, void *data
)
1964 struct file_system_type
*type
= get_fs_type(fstype
);
1965 struct vfsmount
*mnt
;
1967 return ERR_PTR(-ENODEV
);
1968 mnt
= vfs_kern_mount(type
, flags
, name
, data
);
1969 if (!IS_ERR(mnt
) && (type
->fs_flags
& FS_HAS_SUBTYPE
) &&
1970 !mnt
->mnt_sb
->s_subtype
)
1971 mnt
= fs_set_subtype(mnt
, fstype
);
1972 put_filesystem(type
);
1975 EXPORT_SYMBOL_GPL(do_kern_mount
);
1978 * add a mount into a namespace's mount tree
1980 static int do_add_mount(struct vfsmount
*newmnt
, struct path
*path
, int mnt_flags
)
1984 mnt_flags
&= ~(MNT_SHARED
| MNT_WRITE_HOLD
| MNT_INTERNAL
);
1986 down_write(&namespace_sem
);
1987 /* Something was mounted here while we slept */
1988 err
= follow_down(path
, true);
1993 if (!(mnt_flags
& MNT_SHRINKABLE
) && !check_mnt(path
->mnt
))
1996 /* Refuse the same filesystem on the same mount point */
1998 if (path
->mnt
->mnt_sb
== newmnt
->mnt_sb
&&
1999 path
->mnt
->mnt_root
== path
->dentry
)
2003 if (S_ISLNK(newmnt
->mnt_root
->d_inode
->i_mode
))
2006 newmnt
->mnt_flags
= mnt_flags
;
2007 err
= graft_tree(newmnt
, path
);
2010 up_write(&namespace_sem
);
2015 * create a new mount for userspace and request it to be added into the
2018 static int do_new_mount(struct path
*path
, char *type
, int flags
,
2019 int mnt_flags
, char *name
, void *data
)
2021 struct vfsmount
*mnt
;
2027 /* we need capabilities... */
2028 if (!capable(CAP_SYS_ADMIN
))
2031 mnt
= do_kern_mount(type
, flags
, name
, data
);
2033 return PTR_ERR(mnt
);
2035 err
= do_add_mount(mnt
, path
, mnt_flags
);
2041 int finish_automount(struct vfsmount
*m
, struct path
*path
)
2044 /* The new mount record should have at least 2 refs to prevent it being
2045 * expired before we get a chance to add it
2047 BUG_ON(mnt_get_count(m
) < 2);
2049 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
2050 m
->mnt_root
== path
->dentry
) {
2055 err
= do_add_mount(m
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
2059 /* remove m from any expiration list it may be on */
2060 if (!list_empty(&m
->mnt_expire
)) {
2061 down_write(&namespace_sem
);
2062 br_write_lock(vfsmount_lock
);
2063 list_del_init(&m
->mnt_expire
);
2064 br_write_unlock(vfsmount_lock
);
2065 up_write(&namespace_sem
);
2073 * mnt_set_expiry - Put a mount on an expiration list
2074 * @mnt: The mount to list.
2075 * @expiry_list: The list to add the mount to.
2077 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
2079 down_write(&namespace_sem
);
2080 br_write_lock(vfsmount_lock
);
2082 list_add_tail(&mnt
->mnt_expire
, expiry_list
);
2084 br_write_unlock(vfsmount_lock
);
2085 up_write(&namespace_sem
);
2087 EXPORT_SYMBOL(mnt_set_expiry
);
2090 * process a list of expirable mountpoints with the intent of discarding any
2091 * mountpoints that aren't in use and haven't been touched since last we came
2094 void mark_mounts_for_expiry(struct list_head
*mounts
)
2096 struct vfsmount
*mnt
, *next
;
2097 LIST_HEAD(graveyard
);
2100 if (list_empty(mounts
))
2103 down_write(&namespace_sem
);
2104 br_write_lock(vfsmount_lock
);
2106 /* extract from the expiration list every vfsmount that matches the
2107 * following criteria:
2108 * - only referenced by its parent vfsmount
2109 * - still marked for expiry (marked on the last call here; marks are
2110 * cleared by mntput())
2112 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
2113 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
2114 propagate_mount_busy(mnt
, 1))
2116 list_move(&mnt
->mnt_expire
, &graveyard
);
2118 while (!list_empty(&graveyard
)) {
2119 mnt
= list_first_entry(&graveyard
, struct vfsmount
, mnt_expire
);
2120 touch_mnt_namespace(mnt
->mnt_ns
);
2121 umount_tree(mnt
, 1, &umounts
);
2123 br_write_unlock(vfsmount_lock
);
2124 up_write(&namespace_sem
);
2126 release_mounts(&umounts
);
2129 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
2132 * Ripoff of 'select_parent()'
2134 * search the list of submounts for a given mountpoint, and move any
2135 * shrinkable submounts to the 'graveyard' list.
2137 static int select_submounts(struct vfsmount
*parent
, struct list_head
*graveyard
)
2139 struct vfsmount
*this_parent
= parent
;
2140 struct list_head
*next
;
2144 next
= this_parent
->mnt_mounts
.next
;
2146 while (next
!= &this_parent
->mnt_mounts
) {
2147 struct list_head
*tmp
= next
;
2148 struct vfsmount
*mnt
= list_entry(tmp
, struct vfsmount
, mnt_child
);
2151 if (!(mnt
->mnt_flags
& MNT_SHRINKABLE
))
2154 * Descend a level if the d_mounts list is non-empty.
2156 if (!list_empty(&mnt
->mnt_mounts
)) {
2161 if (!propagate_mount_busy(mnt
, 1)) {
2162 list_move_tail(&mnt
->mnt_expire
, graveyard
);
2167 * All done at this level ... ascend and resume the search
2169 if (this_parent
!= parent
) {
2170 next
= this_parent
->mnt_child
.next
;
2171 this_parent
= this_parent
->mnt_parent
;
2178 * process a list of expirable mountpoints with the intent of discarding any
2179 * submounts of a specific parent mountpoint
2181 * vfsmount_lock must be held for write
2183 static void shrink_submounts(struct vfsmount
*mnt
, struct list_head
*umounts
)
2185 LIST_HEAD(graveyard
);
2188 /* extract submounts of 'mountpoint' from the expiration list */
2189 while (select_submounts(mnt
, &graveyard
)) {
2190 while (!list_empty(&graveyard
)) {
2191 m
= list_first_entry(&graveyard
, struct vfsmount
,
2193 touch_mnt_namespace(m
->mnt_ns
);
2194 umount_tree(m
, 1, umounts
);
2200 * Some copy_from_user() implementations do not return the exact number of
2201 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2202 * Note that this function differs from copy_from_user() in that it will oops
2203 * on bad values of `to', rather than returning a short copy.
2205 static long exact_copy_from_user(void *to
, const void __user
* from
,
2209 const char __user
*f
= from
;
2212 if (!access_ok(VERIFY_READ
, from
, n
))
2216 if (__get_user(c
, f
)) {
2227 int copy_mount_options(const void __user
* data
, unsigned long *where
)
2237 if (!(page
= __get_free_page(GFP_KERNEL
)))
2240 /* We only care that *some* data at the address the user
2241 * gave us is valid. Just in case, we'll zero
2242 * the remainder of the page.
2244 /* copy_from_user cannot cross TASK_SIZE ! */
2245 size
= TASK_SIZE
- (unsigned long)data
;
2246 if (size
> PAGE_SIZE
)
2249 i
= size
- exact_copy_from_user((void *)page
, data
, size
);
2255 memset((char *)page
+ i
, 0, PAGE_SIZE
- i
);
2260 int copy_mount_string(const void __user
*data
, char **where
)
2269 tmp
= strndup_user(data
, PAGE_SIZE
);
2271 return PTR_ERR(tmp
);
2278 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2279 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2281 * data is a (void *) that can point to any structure up to
2282 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2283 * information (or be NULL).
2285 * Pre-0.97 versions of mount() didn't have a flags word.
2286 * When the flags word was introduced its top half was required
2287 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2288 * Therefore, if this magic number is present, it carries no information
2289 * and must be discarded.
2291 long do_mount(char *dev_name
, char *dir_name
, char *type_page
,
2292 unsigned long flags
, void *data_page
)
2299 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
2300 flags
&= ~MS_MGC_MSK
;
2302 /* Basic sanity checks */
2304 if (!dir_name
|| !*dir_name
|| !memchr(dir_name
, 0, PAGE_SIZE
))
2308 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
2310 /* ... and get the mountpoint */
2311 retval
= kern_path(dir_name
, LOOKUP_FOLLOW
, &path
);
2315 retval
= security_sb_mount(dev_name
, &path
,
2316 type_page
, flags
, data_page
);
2320 /* Default to relatime unless overriden */
2321 if (!(flags
& MS_NOATIME
))
2322 mnt_flags
|= MNT_RELATIME
;
2324 /* Separate the per-mountpoint flags */
2325 if (flags
& MS_NOSUID
)
2326 mnt_flags
|= MNT_NOSUID
;
2327 if (flags
& MS_NODEV
)
2328 mnt_flags
|= MNT_NODEV
;
2329 if (flags
& MS_NOEXEC
)
2330 mnt_flags
|= MNT_NOEXEC
;
2331 if (flags
& MS_NOATIME
)
2332 mnt_flags
|= MNT_NOATIME
;
2333 if (flags
& MS_NODIRATIME
)
2334 mnt_flags
|= MNT_NODIRATIME
;
2335 if (flags
& MS_STRICTATIME
)
2336 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
2337 if (flags
& MS_RDONLY
)
2338 mnt_flags
|= MNT_READONLY
;
2340 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
| MS_BORN
|
2341 MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
| MS_KERNMOUNT
|
2344 if (flags
& MS_REMOUNT
)
2345 retval
= do_remount(&path
, flags
& ~MS_REMOUNT
, mnt_flags
,
2347 else if (flags
& MS_BIND
)
2348 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
2349 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2350 retval
= do_change_type(&path
, flags
);
2351 else if (flags
& MS_MOVE
)
2352 retval
= do_move_mount(&path
, dev_name
);
2354 retval
= do_new_mount(&path
, type_page
, flags
, mnt_flags
,
2355 dev_name
, data_page
);
2361 static struct mnt_namespace
*alloc_mnt_ns(void)
2363 struct mnt_namespace
*new_ns
;
2365 new_ns
= kmalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
2367 return ERR_PTR(-ENOMEM
);
2368 atomic_set(&new_ns
->count
, 1);
2369 new_ns
->root
= NULL
;
2370 INIT_LIST_HEAD(&new_ns
->list
);
2371 init_waitqueue_head(&new_ns
->poll
);
2376 void mnt_make_longterm(struct vfsmount
*mnt
)
2378 __mnt_make_longterm(mnt
);
2381 void mnt_make_shortterm(struct vfsmount
*mnt
)
2384 if (atomic_add_unless(&mnt
->mnt_longterm
, -1, 1))
2386 br_write_lock(vfsmount_lock
);
2387 atomic_dec(&mnt
->mnt_longterm
);
2388 br_write_unlock(vfsmount_lock
);
2393 * Allocate a new namespace structure and populate it with contents
2394 * copied from the namespace of the passed in task structure.
2396 static struct mnt_namespace
*dup_mnt_ns(struct mnt_namespace
*mnt_ns
,
2397 struct fs_struct
*fs
)
2399 struct mnt_namespace
*new_ns
;
2400 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
2401 struct vfsmount
*p
, *q
;
2403 new_ns
= alloc_mnt_ns();
2407 down_write(&namespace_sem
);
2408 /* First pass: copy the tree topology */
2409 new_ns
->root
= copy_tree(mnt_ns
->root
, mnt_ns
->root
->mnt_root
,
2410 CL_COPY_ALL
| CL_EXPIRE
);
2411 if (!new_ns
->root
) {
2412 up_write(&namespace_sem
);
2414 return ERR_PTR(-ENOMEM
);
2416 br_write_lock(vfsmount_lock
);
2417 list_add_tail(&new_ns
->list
, &new_ns
->root
->mnt_list
);
2418 br_write_unlock(vfsmount_lock
);
2421 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2422 * as belonging to new namespace. We have already acquired a private
2423 * fs_struct, so tsk->fs->lock is not needed.
2429 __mnt_make_longterm(q
);
2431 if (p
== fs
->root
.mnt
) {
2432 fs
->root
.mnt
= mntget(q
);
2433 __mnt_make_longterm(q
);
2434 mnt_make_shortterm(p
);
2437 if (p
== fs
->pwd
.mnt
) {
2438 fs
->pwd
.mnt
= mntget(q
);
2439 __mnt_make_longterm(q
);
2440 mnt_make_shortterm(p
);
2444 p
= next_mnt(p
, mnt_ns
->root
);
2445 q
= next_mnt(q
, new_ns
->root
);
2447 up_write(&namespace_sem
);
2457 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
2458 struct fs_struct
*new_fs
)
2460 struct mnt_namespace
*new_ns
;
2465 if (!(flags
& CLONE_NEWNS
))
2468 new_ns
= dup_mnt_ns(ns
, new_fs
);
2475 * create_mnt_ns - creates a private namespace and adds a root filesystem
2476 * @mnt: pointer to the new root filesystem mountpoint
2478 struct mnt_namespace
*create_mnt_ns(struct vfsmount
*mnt
)
2480 struct mnt_namespace
*new_ns
;
2482 new_ns
= alloc_mnt_ns();
2483 if (!IS_ERR(new_ns
)) {
2484 mnt
->mnt_ns
= new_ns
;
2485 __mnt_make_longterm(mnt
);
2487 list_add(&new_ns
->list
, &new_ns
->root
->mnt_list
);
2491 EXPORT_SYMBOL(create_mnt_ns
);
2493 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
2494 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
2500 unsigned long data_page
;
2502 ret
= copy_mount_string(type
, &kernel_type
);
2506 kernel_dir
= getname(dir_name
);
2507 if (IS_ERR(kernel_dir
)) {
2508 ret
= PTR_ERR(kernel_dir
);
2512 ret
= copy_mount_string(dev_name
, &kernel_dev
);
2516 ret
= copy_mount_options(data
, &data_page
);
2520 ret
= do_mount(kernel_dev
, kernel_dir
, kernel_type
, flags
,
2521 (void *) data_page
);
2523 free_page(data_page
);
2527 putname(kernel_dir
);
2535 * pivot_root Semantics:
2536 * Moves the root file system of the current process to the directory put_old,
2537 * makes new_root as the new root file system of the current process, and sets
2538 * root/cwd of all processes which had them on the current root to new_root.
2541 * The new_root and put_old must be directories, and must not be on the
2542 * same file system as the current process root. The put_old must be
2543 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2544 * pointed to by put_old must yield the same directory as new_root. No other
2545 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2547 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2548 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2549 * in this situation.
2552 * - we don't move root/cwd if they are not at the root (reason: if something
2553 * cared enough to change them, it's probably wrong to force them elsewhere)
2554 * - it's okay to pick a root that isn't the root of a file system, e.g.
2555 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2556 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2559 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
2560 const char __user
*, put_old
)
2562 struct vfsmount
*tmp
;
2563 struct path
new, old
, parent_path
, root_parent
, root
;
2566 if (!capable(CAP_SYS_ADMIN
))
2569 error
= user_path_dir(new_root
, &new);
2573 if (!check_mnt(new.mnt
))
2576 error
= user_path_dir(put_old
, &old
);
2580 error
= security_sb_pivotroot(&old
, &new);
2586 get_fs_root(current
->fs
, &root
);
2587 down_write(&namespace_sem
);
2588 mutex_lock(&old
.dentry
->d_inode
->i_mutex
);
2590 if (IS_MNT_SHARED(old
.mnt
) ||
2591 IS_MNT_SHARED(new.mnt
->mnt_parent
) ||
2592 IS_MNT_SHARED(root
.mnt
->mnt_parent
))
2594 if (!check_mnt(root
.mnt
))
2597 if (cant_mount(old
.dentry
))
2599 if (d_unlinked(new.dentry
))
2601 if (d_unlinked(old
.dentry
))
2604 if (new.mnt
== root
.mnt
||
2605 old
.mnt
== root
.mnt
)
2606 goto out2
; /* loop, on the same file system */
2608 if (root
.mnt
->mnt_root
!= root
.dentry
)
2609 goto out2
; /* not a mountpoint */
2610 if (root
.mnt
->mnt_parent
== root
.mnt
)
2611 goto out2
; /* not attached */
2612 if (new.mnt
->mnt_root
!= new.dentry
)
2613 goto out2
; /* not a mountpoint */
2614 if (new.mnt
->mnt_parent
== new.mnt
)
2615 goto out2
; /* not attached */
2616 /* make sure we can reach put_old from new_root */
2618 br_write_lock(vfsmount_lock
);
2619 if (tmp
!= new.mnt
) {
2621 if (tmp
->mnt_parent
== tmp
)
2622 goto out3
; /* already mounted on put_old */
2623 if (tmp
->mnt_parent
== new.mnt
)
2625 tmp
= tmp
->mnt_parent
;
2627 if (!is_subdir(tmp
->mnt_mountpoint
, new.dentry
))
2629 } else if (!is_subdir(old
.dentry
, new.dentry
))
2631 detach_mnt(new.mnt
, &parent_path
);
2632 detach_mnt(root
.mnt
, &root_parent
);
2633 /* mount old root on put_old */
2634 attach_mnt(root
.mnt
, &old
);
2635 /* mount new_root on / */
2636 attach_mnt(new.mnt
, &root_parent
);
2637 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
2638 br_write_unlock(vfsmount_lock
);
2639 chroot_fs_refs(&root
, &new);
2642 path_put(&root_parent
);
2643 path_put(&parent_path
);
2645 mutex_unlock(&old
.dentry
->d_inode
->i_mutex
);
2646 up_write(&namespace_sem
);
2654 br_write_unlock(vfsmount_lock
);
2658 static void __init
init_mount_tree(void)
2660 struct vfsmount
*mnt
;
2661 struct mnt_namespace
*ns
;
2664 mnt
= do_kern_mount("rootfs", 0, "rootfs", NULL
);
2666 panic("Can't create rootfs");
2668 ns
= create_mnt_ns(mnt
);
2670 panic("Can't allocate initial namespace");
2672 init_task
.nsproxy
->mnt_ns
= ns
;
2675 root
.mnt
= ns
->root
;
2676 root
.dentry
= ns
->root
->mnt_root
;
2678 set_fs_pwd(current
->fs
, &root
);
2679 set_fs_root(current
->fs
, &root
);
2682 void __init
mnt_init(void)
2687 init_rwsem(&namespace_sem
);
2689 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct vfsmount
),
2690 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
2692 mount_hashtable
= (struct list_head
*)__get_free_page(GFP_ATOMIC
);
2694 if (!mount_hashtable
)
2695 panic("Failed to allocate mount hash table\n");
2697 printk("Mount-cache hash table entries: %lu\n", HASH_SIZE
);
2699 for (u
= 0; u
< HASH_SIZE
; u
++)
2700 INIT_LIST_HEAD(&mount_hashtable
[u
]);
2702 br_lock_init(vfsmount_lock
);
2706 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
2708 fs_kobj
= kobject_create_and_add("fs", NULL
);
2710 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
2715 void put_mnt_ns(struct mnt_namespace
*ns
)
2717 LIST_HEAD(umount_list
);
2719 if (!atomic_dec_and_test(&ns
->count
))
2721 down_write(&namespace_sem
);
2722 br_write_lock(vfsmount_lock
);
2723 umount_tree(ns
->root
, 0, &umount_list
);
2724 br_write_unlock(vfsmount_lock
);
2725 up_write(&namespace_sem
);
2726 release_mounts(&umount_list
);
2729 EXPORT_SYMBOL(put_mnt_ns
);
2731 struct vfsmount
*kern_mount_data(struct file_system_type
*type
, void *data
)
2733 return vfs_kern_mount(type
, MS_KERNMOUNT
, type
->name
, data
);
2735 EXPORT_SYMBOL_GPL(kern_mount_data
);