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 mount
*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
.mnt_id
);
90 mnt_id_start
= mnt
->mnt
.mnt_id
+ 1;
91 spin_unlock(&mnt_id_lock
);
98 static void mnt_free_id(struct mount
*mnt
)
100 int id
= mnt
->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 mount
*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 mount
*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 mount
*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(p
);
186 mnt
->mnt_devname
= kstrdup(name
, GFP_KERNEL
);
187 if (!mnt
->mnt_devname
)
192 p
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
194 goto out_free_devname
;
196 this_cpu_add(p
->mnt_pcp
->mnt_count
, 1);
202 INIT_LIST_HEAD(&p
->mnt_hash
);
203 INIT_LIST_HEAD(&p
->mnt_child
);
204 INIT_LIST_HEAD(&p
->mnt_mounts
);
205 INIT_LIST_HEAD(&mnt
->mnt_list
);
206 INIT_LIST_HEAD(&p
->mnt_expire
);
207 INIT_LIST_HEAD(&p
->mnt_share
);
208 INIT_LIST_HEAD(&p
->mnt_slave_list
);
209 INIT_LIST_HEAD(&p
->mnt_slave
);
210 #ifdef CONFIG_FSNOTIFY
211 INIT_HLIST_HEAD(&mnt
->mnt_fsnotify_marks
);
218 kfree(p
->mnt
.mnt_devname
);
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 mount
*mnt
)
259 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
265 static inline void mnt_dec_writers(struct mount
*mnt
)
268 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
274 static unsigned int mnt_get_writers(struct mount
*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 * @m: 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
*m
)
310 struct mount
*mnt
= real_mount(m
);
314 mnt_inc_writers(mnt
);
316 * The store to mnt_inc_writers must be visible before we pass
317 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
318 * incremented count after it has set MNT_WRITE_HOLD.
321 while (mnt
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
324 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
325 * be set to match its requirements. So we must not load that until
326 * MNT_WRITE_HOLD is cleared.
329 if (__mnt_is_readonly(m
)) {
330 mnt_dec_writers(mnt
);
338 EXPORT_SYMBOL_GPL(mnt_want_write
);
341 * mnt_clone_write - get write access to a mount
342 * @mnt: the mount on which to take a write
344 * This is effectively like mnt_want_write, except
345 * it must only be used to take an extra write reference
346 * on a mountpoint that we already know has a write reference
347 * on it. This allows some optimisation.
349 * After finished, mnt_drop_write must be called as usual to
350 * drop the reference.
352 int mnt_clone_write(struct vfsmount
*mnt
)
354 /* superblock may be r/o */
355 if (__mnt_is_readonly(mnt
))
358 mnt_inc_writers(real_mount(mnt
));
362 EXPORT_SYMBOL_GPL(mnt_clone_write
);
365 * mnt_want_write_file - get write access to a file's mount
366 * @file: the file who's mount on which to take a write
368 * This is like mnt_want_write, but it takes a file and can
369 * do some optimisations if the file is open for write already
371 int mnt_want_write_file(struct file
*file
)
373 struct inode
*inode
= file
->f_dentry
->d_inode
;
374 if (!(file
->f_mode
& FMODE_WRITE
) || special_file(inode
->i_mode
))
375 return mnt_want_write(file
->f_path
.mnt
);
377 return mnt_clone_write(file
->f_path
.mnt
);
379 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
382 * mnt_drop_write - give up write access to a mount
383 * @mnt: the mount on which to give up write access
385 * Tells the low-level filesystem that we are done
386 * performing writes to it. Must be matched with
387 * mnt_want_write() call above.
389 void mnt_drop_write(struct vfsmount
*mnt
)
392 mnt_dec_writers(real_mount(mnt
));
395 EXPORT_SYMBOL_GPL(mnt_drop_write
);
397 void mnt_drop_write_file(struct file
*file
)
399 mnt_drop_write(file
->f_path
.mnt
);
401 EXPORT_SYMBOL(mnt_drop_write_file
);
403 static int mnt_make_readonly(struct mount
*mnt
)
407 br_write_lock(vfsmount_lock
);
408 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
410 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
411 * should be visible before we do.
416 * With writers on hold, if this value is zero, then there are
417 * definitely no active writers (although held writers may subsequently
418 * increment the count, they'll have to wait, and decrement it after
419 * seeing MNT_READONLY).
421 * It is OK to have counter incremented on one CPU and decremented on
422 * another: the sum will add up correctly. The danger would be when we
423 * sum up each counter, if we read a counter before it is incremented,
424 * but then read another CPU's count which it has been subsequently
425 * decremented from -- we would see more decrements than we should.
426 * MNT_WRITE_HOLD protects against this scenario, because
427 * mnt_want_write first increments count, then smp_mb, then spins on
428 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
429 * we're counting up here.
431 if (mnt_get_writers(mnt
) > 0)
434 mnt
->mnt
.mnt_flags
|= MNT_READONLY
;
436 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
437 * that become unheld will see MNT_READONLY.
440 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
441 br_write_unlock(vfsmount_lock
);
445 static void __mnt_unmake_readonly(struct mount
*mnt
)
447 br_write_lock(vfsmount_lock
);
448 mnt
->mnt
.mnt_flags
&= ~MNT_READONLY
;
449 br_write_unlock(vfsmount_lock
);
452 static void free_vfsmnt(struct mount
*mnt
)
454 kfree(mnt
->mnt
.mnt_devname
);
457 free_percpu(mnt
->mnt_pcp
);
459 kmem_cache_free(mnt_cache
, mnt
);
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_hash
);
480 if (&p
->mnt_parent
->mnt
== mnt
&& p
->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 mount
*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_mountpoint
;
562 old_path
->mnt
= &mnt
->mnt_parent
->mnt
;
563 mnt
->mnt_parent
= mnt
;
564 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
565 list_del_init(&mnt
->mnt_child
);
566 list_del_init(&mnt
->mnt_hash
);
567 dentry_reset_mounted(old_path
->dentry
);
571 * vfsmount lock must be held for write
573 void mnt_set_mountpoint(struct mount
*mnt
, struct dentry
*dentry
,
574 struct mount
*child_mnt
)
576 child_mnt
->mnt_parent
= real_mount(mntget(&mnt
->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(real_mount(path
->mnt
), path
->dentry
, mnt
);
589 list_add_tail(&mnt
->mnt_hash
, mount_hashtable
+
590 hash(path
->mnt
, path
->dentry
));
591 list_add_tail(&mnt
->mnt_child
, &real_mount(path
->mnt
)->mnt_mounts
);
594 static inline void __mnt_make_longterm(struct mount
*mnt
)
597 atomic_inc(&mnt
->mnt_longterm
);
601 /* needs vfsmount lock for write */
602 static inline void __mnt_make_shortterm(struct mount
*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 mount
*parent
= mnt
->mnt_parent
;
617 struct mnt_namespace
*n
= parent
->mnt_ns
;
619 BUG_ON(parent
== mnt
);
621 list_add_tail(&head
, &mnt
->mnt
.mnt_list
);
622 list_for_each_entry(m
, &head
, mnt
.mnt_list
) {
624 __mnt_make_longterm(m
);
627 list_splice(&head
, n
->list
.prev
);
629 list_add_tail(&mnt
->mnt_hash
, mount_hashtable
+
630 hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
631 list_add_tail(&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_mounts
.next
;
638 if (next
== &p
->mnt_mounts
) {
642 next
= p
->mnt_child
.next
;
643 if (next
!= &p
->mnt_parent
->mnt_mounts
)
648 return list_entry(next
, struct mount
, mnt_child
);
651 static struct mount
*skip_mnt_tree(struct mount
*p
)
653 struct list_head
*prev
= p
->mnt_mounts
.prev
;
654 while (prev
!= &p
->mnt_mounts
) {
655 p
= list_entry(prev
, struct mount
, mnt_child
);
656 prev
= p
->mnt_mounts
.prev
;
662 vfs_kern_mount(struct file_system_type
*type
, int flags
, const char *name
, void *data
)
668 return ERR_PTR(-ENODEV
);
670 mnt
= alloc_vfsmnt(name
);
672 return ERR_PTR(-ENOMEM
);
674 if (flags
& MS_KERNMOUNT
)
675 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
677 root
= mount_fs(type
, flags
, name
, data
);
680 return ERR_CAST(root
);
683 mnt
->mnt
.mnt_root
= root
;
684 mnt
->mnt
.mnt_sb
= root
->d_sb
;
685 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
686 mnt
->mnt_parent
= mnt
;
689 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
691 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
694 struct super_block
*sb
= old
->mnt
.mnt_sb
;
695 struct mount
*mnt
= alloc_vfsmnt(old
->mnt
.mnt_devname
);
698 if (flag
& (CL_SLAVE
| CL_PRIVATE
))
699 mnt
->mnt
.mnt_group_id
= 0; /* not a peer of original */
701 mnt
->mnt
.mnt_group_id
= old
->mnt
.mnt_group_id
;
703 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt
.mnt_group_id
) {
704 int err
= mnt_alloc_group_id(mnt
);
709 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
& ~MNT_WRITE_HOLD
;
710 atomic_inc(&sb
->s_active
);
711 mnt
->mnt
.mnt_sb
= sb
;
712 mnt
->mnt
.mnt_root
= dget(root
);
713 mnt
->mnt_mountpoint
= mnt
->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
->mnt
);
720 } else if (!(flag
& CL_PRIVATE
)) {
721 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(&old
->mnt
))
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 mount
*mnt
)
746 struct vfsmount
*m
= &mnt
->mnt
;
747 struct super_block
*sb
= m
->mnt_sb
;
750 * This probably indicates that somebody messed
751 * up a mnt_want/drop_write() pair. If this
752 * happens, the filesystem was probably unable
753 * to make r/w->r/o transitions.
756 * The locking used to deal with mnt_count decrement provides barriers,
757 * so mnt_get_writers() below is safe.
759 WARN_ON(mnt_get_writers(mnt
));
760 fsnotify_vfsmount_delete(m
);
763 deactivate_super(sb
);
766 static void mntput_no_expire(struct mount
*mnt
)
770 br_read_lock(vfsmount_lock
);
771 if (likely(atomic_read(&mnt
->mnt_longterm
))) {
772 mnt_add_count(mnt
, -1);
773 br_read_unlock(vfsmount_lock
);
776 br_read_unlock(vfsmount_lock
);
778 br_write_lock(vfsmount_lock
);
779 mnt_add_count(mnt
, -1);
780 if (mnt_get_count(mnt
)) {
781 br_write_unlock(vfsmount_lock
);
785 mnt_add_count(mnt
, -1);
786 if (likely(mnt_get_count(mnt
)))
788 br_write_lock(vfsmount_lock
);
790 if (unlikely(mnt
->mnt
.mnt_pinned
)) {
791 mnt_add_count(mnt
, mnt
->mnt
.mnt_pinned
+ 1);
792 mnt
->mnt
.mnt_pinned
= 0;
793 br_write_unlock(vfsmount_lock
);
794 acct_auto_close_mnt(&mnt
->mnt
);
797 br_write_unlock(vfsmount_lock
);
801 void mntput(struct vfsmount
*mnt
)
804 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
805 if (unlikely(mnt
->mnt_expiry_mark
))
806 mnt
->mnt_expiry_mark
= 0;
807 mntput_no_expire(real_mount(mnt
));
810 EXPORT_SYMBOL(mntput
);
812 struct vfsmount
*mntget(struct vfsmount
*mnt
)
815 mnt_add_count(real_mount(mnt
), 1);
818 EXPORT_SYMBOL(mntget
);
820 void mnt_pin(struct vfsmount
*mnt
)
822 br_write_lock(vfsmount_lock
);
824 br_write_unlock(vfsmount_lock
);
826 EXPORT_SYMBOL(mnt_pin
);
828 void mnt_unpin(struct vfsmount
*mnt
)
830 br_write_lock(vfsmount_lock
);
831 if (mnt
->mnt_pinned
) {
832 mnt_add_count(real_mount(mnt
), 1);
835 br_write_unlock(vfsmount_lock
);
837 EXPORT_SYMBOL(mnt_unpin
);
839 static inline void mangle(struct seq_file
*m
, const char *s
)
841 seq_escape(m
, s
, " \t\n\\");
845 * Simple .show_options callback for filesystems which don't want to
846 * implement more complex mount option showing.
848 * See also save_mount_options().
850 int generic_show_options(struct seq_file
*m
, struct vfsmount
*mnt
)
855 options
= rcu_dereference(mnt
->mnt_sb
->s_options
);
857 if (options
!= NULL
&& options
[0]) {
865 EXPORT_SYMBOL(generic_show_options
);
868 * If filesystem uses generic_show_options(), this function should be
869 * called from the fill_super() callback.
871 * The .remount_fs callback usually needs to be handled in a special
872 * way, to make sure, that previous options are not overwritten if the
875 * Also note, that if the filesystem's .remount_fs function doesn't
876 * reset all options to their default value, but changes only newly
877 * given options, then the displayed options will not reflect reality
880 void save_mount_options(struct super_block
*sb
, char *options
)
882 BUG_ON(sb
->s_options
);
883 rcu_assign_pointer(sb
->s_options
, kstrdup(options
, GFP_KERNEL
));
885 EXPORT_SYMBOL(save_mount_options
);
887 void replace_mount_options(struct super_block
*sb
, char *options
)
889 char *old
= sb
->s_options
;
890 rcu_assign_pointer(sb
->s_options
, options
);
896 EXPORT_SYMBOL(replace_mount_options
);
898 #ifdef CONFIG_PROC_FS
900 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
902 struct proc_mounts
*p
= m
->private;
904 down_read(&namespace_sem
);
905 return seq_list_start(&p
->ns
->list
, *pos
);
908 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
910 struct proc_mounts
*p
= m
->private;
912 return seq_list_next(v
, &p
->ns
->list
, pos
);
915 static void m_stop(struct seq_file
*m
, void *v
)
917 up_read(&namespace_sem
);
920 int mnt_had_events(struct proc_mounts
*p
)
922 struct mnt_namespace
*ns
= p
->ns
;
925 br_read_lock(vfsmount_lock
);
926 if (p
->m
.poll_event
!= ns
->event
) {
927 p
->m
.poll_event
= ns
->event
;
930 br_read_unlock(vfsmount_lock
);
935 struct proc_fs_info
{
940 static int show_sb_opts(struct seq_file
*m
, struct super_block
*sb
)
942 static const struct proc_fs_info fs_info
[] = {
943 { MS_SYNCHRONOUS
, ",sync" },
944 { MS_DIRSYNC
, ",dirsync" },
945 { MS_MANDLOCK
, ",mand" },
948 const struct proc_fs_info
*fs_infop
;
950 for (fs_infop
= fs_info
; fs_infop
->flag
; fs_infop
++) {
951 if (sb
->s_flags
& fs_infop
->flag
)
952 seq_puts(m
, fs_infop
->str
);
955 return security_sb_show_options(m
, sb
);
958 static void show_mnt_opts(struct seq_file
*m
, struct vfsmount
*mnt
)
960 static const struct proc_fs_info mnt_info
[] = {
961 { MNT_NOSUID
, ",nosuid" },
962 { MNT_NODEV
, ",nodev" },
963 { MNT_NOEXEC
, ",noexec" },
964 { MNT_NOATIME
, ",noatime" },
965 { MNT_NODIRATIME
, ",nodiratime" },
966 { MNT_RELATIME
, ",relatime" },
969 const struct proc_fs_info
*fs_infop
;
971 for (fs_infop
= mnt_info
; fs_infop
->flag
; fs_infop
++) {
972 if (mnt
->mnt_flags
& fs_infop
->flag
)
973 seq_puts(m
, fs_infop
->str
);
977 static void show_type(struct seq_file
*m
, struct super_block
*sb
)
979 mangle(m
, sb
->s_type
->name
);
980 if (sb
->s_subtype
&& sb
->s_subtype
[0]) {
982 mangle(m
, sb
->s_subtype
);
986 static int show_vfsmnt(struct seq_file
*m
, void *v
)
988 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
990 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
992 if (mnt
->mnt_sb
->s_op
->show_devname
) {
993 err
= mnt
->mnt_sb
->s_op
->show_devname(m
, mnt
);
997 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
1000 seq_path(m
, &mnt_path
, " \t\n\\");
1002 show_type(m
, mnt
->mnt_sb
);
1003 seq_puts(m
, __mnt_is_readonly(mnt
) ? " ro" : " rw");
1004 err
= show_sb_opts(m
, mnt
->mnt_sb
);
1007 show_mnt_opts(m
, mnt
);
1008 if (mnt
->mnt_sb
->s_op
->show_options
)
1009 err
= mnt
->mnt_sb
->s_op
->show_options(m
, mnt
);
1010 seq_puts(m
, " 0 0\n");
1015 const struct seq_operations mounts_op
= {
1022 static int show_mountinfo(struct seq_file
*m
, void *v
)
1024 struct proc_mounts
*p
= m
->private;
1025 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
1026 struct mount
*r
= real_mount(mnt
);
1027 struct super_block
*sb
= mnt
->mnt_sb
;
1028 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
1029 struct path root
= p
->root
;
1032 seq_printf(m
, "%i %i %u:%u ", mnt
->mnt_id
, r
->mnt_parent
->mnt
.mnt_id
,
1033 MAJOR(sb
->s_dev
), MINOR(sb
->s_dev
));
1034 if (sb
->s_op
->show_path
)
1035 err
= sb
->s_op
->show_path(m
, mnt
);
1037 seq_dentry(m
, mnt
->mnt_root
, " \t\n\\");
1042 /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
1043 err
= seq_path_root(m
, &mnt_path
, &root
, " \t\n\\");
1047 seq_puts(m
, mnt
->mnt_flags
& MNT_READONLY
? " ro" : " rw");
1048 show_mnt_opts(m
, mnt
);
1050 /* Tagged fields ("foo:X" or "bar") */
1051 if (IS_MNT_SHARED(mnt
))
1052 seq_printf(m
, " shared:%i", mnt
->mnt_group_id
);
1053 if (IS_MNT_SLAVE(r
)) {
1054 int master
= r
->mnt_master
->mnt
.mnt_group_id
;
1055 int dom
= get_dominating_id(r
, &p
->root
);
1056 seq_printf(m
, " master:%i", master
);
1057 if (dom
&& dom
!= master
)
1058 seq_printf(m
, " propagate_from:%i", dom
);
1060 if (IS_MNT_UNBINDABLE(mnt
))
1061 seq_puts(m
, " unbindable");
1063 /* Filesystem specific data */
1067 if (sb
->s_op
->show_devname
)
1068 err
= sb
->s_op
->show_devname(m
, mnt
);
1070 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
1073 seq_puts(m
, sb
->s_flags
& MS_RDONLY
? " ro" : " rw");
1074 err
= show_sb_opts(m
, sb
);
1077 if (sb
->s_op
->show_options
)
1078 err
= sb
->s_op
->show_options(m
, mnt
);
1084 const struct seq_operations mountinfo_op
= {
1088 .show
= show_mountinfo
,
1091 static int show_vfsstat(struct seq_file
*m
, void *v
)
1093 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
1094 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
1098 if (mnt
->mnt_sb
->s_op
->show_devname
) {
1099 seq_puts(m
, "device ");
1100 err
= mnt
->mnt_sb
->s_op
->show_devname(m
, mnt
);
1102 if (mnt
->mnt_devname
) {
1103 seq_puts(m
, "device ");
1104 mangle(m
, mnt
->mnt_devname
);
1106 seq_puts(m
, "no device");
1110 seq_puts(m
, " mounted on ");
1111 seq_path(m
, &mnt_path
, " \t\n\\");
1114 /* file system type */
1115 seq_puts(m
, "with fstype ");
1116 show_type(m
, mnt
->mnt_sb
);
1118 /* optional statistics */
1119 if (mnt
->mnt_sb
->s_op
->show_stats
) {
1122 err
= mnt
->mnt_sb
->s_op
->show_stats(m
, mnt
);
1129 const struct seq_operations mountstats_op
= {
1133 .show
= show_vfsstat
,
1135 #endif /* CONFIG_PROC_FS */
1138 * may_umount_tree - check if a mount tree is busy
1139 * @mnt: root of mount tree
1141 * This is called to check if a tree of mounts has any
1142 * open files, pwds, chroots or sub mounts that are
1145 int may_umount_tree(struct vfsmount
*mnt
)
1147 int actual_refs
= 0;
1148 int minimum_refs
= 0;
1152 /* write lock needed for mnt_get_count */
1153 br_write_lock(vfsmount_lock
);
1154 for (p
= real_mount(mnt
); p
; p
= next_mnt(p
, mnt
)) {
1155 actual_refs
+= mnt_get_count(p
);
1158 br_write_unlock(vfsmount_lock
);
1160 if (actual_refs
> minimum_refs
)
1166 EXPORT_SYMBOL(may_umount_tree
);
1169 * may_umount - check if a mount point is busy
1170 * @mnt: root of mount
1172 * This is called to check if a mount point has any
1173 * open files, pwds, chroots or sub mounts. If the
1174 * mount has sub mounts this will return busy
1175 * regardless of whether the sub mounts are busy.
1177 * Doesn't take quota and stuff into account. IOW, in some cases it will
1178 * give false negatives. The main reason why it's here is that we need
1179 * a non-destructive way to look for easily umountable filesystems.
1181 int may_umount(struct vfsmount
*mnt
)
1184 down_read(&namespace_sem
);
1185 br_write_lock(vfsmount_lock
);
1186 if (propagate_mount_busy(real_mount(mnt
), 2))
1188 br_write_unlock(vfsmount_lock
);
1189 up_read(&namespace_sem
);
1193 EXPORT_SYMBOL(may_umount
);
1195 void release_mounts(struct list_head
*head
)
1198 while (!list_empty(head
)) {
1199 mnt
= list_first_entry(head
, struct mount
, mnt_hash
);
1200 list_del_init(&mnt
->mnt_hash
);
1201 if (mnt_has_parent(mnt
)) {
1202 struct dentry
*dentry
;
1205 br_write_lock(vfsmount_lock
);
1206 dentry
= mnt
->mnt_mountpoint
;
1207 m
= &mnt
->mnt_parent
->mnt
;
1208 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1209 mnt
->mnt_parent
= mnt
;
1211 br_write_unlock(vfsmount_lock
);
1220 * vfsmount lock must be held for write
1221 * namespace_sem must be held for write
1223 void umount_tree(struct mount
*mnt
, int propagate
, struct list_head
*kill
)
1225 LIST_HEAD(tmp_list
);
1228 for (p
= mnt
; p
; p
= next_mnt(p
, &mnt
->mnt
))
1229 list_move(&p
->mnt_hash
, &tmp_list
);
1232 propagate_umount(&tmp_list
);
1234 list_for_each_entry(p
, &tmp_list
, mnt_hash
) {
1235 list_del_init(&p
->mnt_expire
);
1236 list_del_init(&p
->mnt
.mnt_list
);
1237 __touch_mnt_namespace(p
->mnt_ns
);
1239 __mnt_make_shortterm(p
);
1240 list_del_init(&p
->mnt_child
);
1241 if (mnt_has_parent(p
)) {
1242 p
->mnt_parent
->mnt
.mnt_ghosts
++;
1243 dentry_reset_mounted(p
->mnt_mountpoint
);
1245 change_mnt_propagation(p
, MS_PRIVATE
);
1247 list_splice(&tmp_list
, kill
);
1250 static void shrink_submounts(struct mount
*mnt
, struct list_head
*umounts
);
1252 static int do_umount(struct mount
*mnt
, int flags
)
1254 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1256 LIST_HEAD(umount_list
);
1258 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1263 * Allow userspace to request a mountpoint be expired rather than
1264 * unmounting unconditionally. Unmount only happens if:
1265 * (1) the mark is already set (the mark is cleared by mntput())
1266 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1268 if (flags
& MNT_EXPIRE
) {
1269 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1270 flags
& (MNT_FORCE
| MNT_DETACH
))
1274 * probably don't strictly need the lock here if we examined
1275 * all race cases, but it's a slowpath.
1277 br_write_lock(vfsmount_lock
);
1278 if (mnt_get_count(mnt
) != 2) {
1279 br_write_unlock(vfsmount_lock
);
1282 br_write_unlock(vfsmount_lock
);
1284 if (!xchg(&mnt
->mnt
.mnt_expiry_mark
, 1))
1289 * If we may have to abort operations to get out of this
1290 * mount, and they will themselves hold resources we must
1291 * allow the fs to do things. In the Unix tradition of
1292 * 'Gee thats tricky lets do it in userspace' the umount_begin
1293 * might fail to complete on the first run through as other tasks
1294 * must return, and the like. Thats for the mount program to worry
1295 * about for the moment.
1298 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1299 sb
->s_op
->umount_begin(sb
);
1303 * No sense to grab the lock for this test, but test itself looks
1304 * somewhat bogus. Suggestions for better replacement?
1305 * Ho-hum... In principle, we might treat that as umount + switch
1306 * to rootfs. GC would eventually take care of the old vfsmount.
1307 * Actually it makes sense, especially if rootfs would contain a
1308 * /reboot - static binary that would close all descriptors and
1309 * call reboot(9). Then init(8) could umount root and exec /reboot.
1311 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1313 * Special case for "unmounting" root ...
1314 * we just try to remount it readonly.
1316 down_write(&sb
->s_umount
);
1317 if (!(sb
->s_flags
& MS_RDONLY
))
1318 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
1319 up_write(&sb
->s_umount
);
1323 down_write(&namespace_sem
);
1324 br_write_lock(vfsmount_lock
);
1327 if (!(flags
& MNT_DETACH
))
1328 shrink_submounts(mnt
, &umount_list
);
1331 if (flags
& MNT_DETACH
|| !propagate_mount_busy(mnt
, 2)) {
1332 if (!list_empty(&mnt
->mnt
.mnt_list
))
1333 umount_tree(mnt
, 1, &umount_list
);
1336 br_write_unlock(vfsmount_lock
);
1337 up_write(&namespace_sem
);
1338 release_mounts(&umount_list
);
1343 * Now umount can handle mount points as well as block devices.
1344 * This is important for filesystems which use unnamed block devices.
1346 * We now support a flag for forced unmount like the other 'big iron'
1347 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1350 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1355 int lookup_flags
= 0;
1357 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1360 if (!(flags
& UMOUNT_NOFOLLOW
))
1361 lookup_flags
|= LOOKUP_FOLLOW
;
1363 retval
= user_path_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1366 mnt
= real_mount(path
.mnt
);
1368 if (path
.dentry
!= path
.mnt
->mnt_root
)
1370 if (!check_mnt(mnt
))
1374 if (!capable(CAP_SYS_ADMIN
))
1377 retval
= do_umount(mnt
, flags
);
1379 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1381 mntput_no_expire(mnt
);
1386 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1389 * The 2.0 compatible umount. No flags.
1391 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1393 return sys_umount(name
, 0);
1398 static int mount_is_safe(struct path
*path
)
1400 if (capable(CAP_SYS_ADMIN
))
1404 if (S_ISLNK(path
->dentry
->d_inode
->i_mode
))
1406 if (path
->dentry
->d_inode
->i_mode
& S_ISVTX
) {
1407 if (current_uid() != path
->dentry
->d_inode
->i_uid
)
1410 if (inode_permission(path
->dentry
->d_inode
, MAY_WRITE
))
1416 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1419 struct mount
*res
, *p
, *q
, *r
;
1422 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(&mnt
->mnt
))
1425 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1428 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1431 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1433 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1436 for (s
= r
; s
; s
= next_mnt(s
, &r
->mnt
)) {
1437 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(&s
->mnt
)) {
1438 s
= skip_mnt_tree(s
);
1441 while (p
!= s
->mnt_parent
) {
1447 path
.dentry
= p
->mnt_mountpoint
;
1448 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
1451 br_write_lock(vfsmount_lock
);
1452 list_add_tail(&q
->mnt
.mnt_list
, &res
->mnt
.mnt_list
);
1453 attach_mnt(q
, &path
);
1454 br_write_unlock(vfsmount_lock
);
1460 LIST_HEAD(umount_list
);
1461 br_write_lock(vfsmount_lock
);
1462 umount_tree(res
, 0, &umount_list
);
1463 br_write_unlock(vfsmount_lock
);
1464 release_mounts(&umount_list
);
1469 struct vfsmount
*collect_mounts(struct path
*path
)
1472 down_write(&namespace_sem
);
1473 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
1474 CL_COPY_ALL
| CL_PRIVATE
);
1475 up_write(&namespace_sem
);
1476 return tree
? &tree
->mnt
: NULL
;
1479 void drop_collected_mounts(struct vfsmount
*mnt
)
1481 LIST_HEAD(umount_list
);
1482 down_write(&namespace_sem
);
1483 br_write_lock(vfsmount_lock
);
1484 umount_tree(real_mount(mnt
), 0, &umount_list
);
1485 br_write_unlock(vfsmount_lock
);
1486 up_write(&namespace_sem
);
1487 release_mounts(&umount_list
);
1490 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1491 struct vfsmount
*root
)
1493 struct vfsmount
*mnt
;
1494 int res
= f(root
, arg
);
1497 list_for_each_entry(mnt
, &root
->mnt_list
, mnt_list
) {
1505 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
1509 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, &mnt
->mnt
)) {
1510 if (p
->mnt
.mnt_group_id
&& !IS_MNT_SHARED(&p
->mnt
))
1511 mnt_release_group_id(p
);
1515 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
1519 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, &mnt
->mnt
) : NULL
) {
1520 if (!p
->mnt
.mnt_group_id
&& !IS_MNT_SHARED(&p
->mnt
)) {
1521 int err
= mnt_alloc_group_id(p
);
1523 cleanup_group_ids(mnt
, p
);
1533 * @source_mnt : mount tree to be attached
1534 * @nd : place the mount tree @source_mnt is attached
1535 * @parent_nd : if non-null, detach the source_mnt from its parent and
1536 * store the parent mount and mountpoint dentry.
1537 * (done when source_mnt is moved)
1539 * NOTE: in the table below explains the semantics when a source mount
1540 * of a given type is attached to a destination mount of a given type.
1541 * ---------------------------------------------------------------------------
1542 * | BIND MOUNT OPERATION |
1543 * |**************************************************************************
1544 * | source-->| shared | private | slave | unbindable |
1548 * |**************************************************************************
1549 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1551 * |non-shared| shared (+) | private | slave (*) | invalid |
1552 * ***************************************************************************
1553 * A bind operation clones the source mount and mounts the clone on the
1554 * destination mount.
1556 * (++) the cloned mount is propagated to all the mounts in the propagation
1557 * tree of the destination mount and the cloned mount is added to
1558 * the peer group of the source mount.
1559 * (+) the cloned mount is created under the destination mount and is marked
1560 * as shared. The cloned mount is added to the peer group of the source
1562 * (+++) the mount is propagated to all the mounts in the propagation tree
1563 * of the destination mount and the cloned mount is made slave
1564 * of the same master as that of the source mount. The cloned mount
1565 * is marked as 'shared and slave'.
1566 * (*) the cloned mount is made a slave of the same master as that of the
1569 * ---------------------------------------------------------------------------
1570 * | MOVE MOUNT OPERATION |
1571 * |**************************************************************************
1572 * | source-->| shared | private | slave | unbindable |
1576 * |**************************************************************************
1577 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1579 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1580 * ***************************************************************************
1582 * (+) the mount is moved to the destination. And is then propagated to
1583 * all the mounts in the propagation tree of the destination mount.
1584 * (+*) the mount is moved to the destination.
1585 * (+++) the mount is moved to the destination and is then propagated to
1586 * all the mounts belonging to the destination mount's propagation tree.
1587 * the mount is marked as 'shared and slave'.
1588 * (*) the mount continues to be a slave at the new location.
1590 * if the source mount is a tree, the operations explained above is
1591 * applied to each mount in the tree.
1592 * Must be called without spinlocks held, since this function can sleep
1595 static int attach_recursive_mnt(struct mount
*source_mnt
,
1596 struct path
*path
, struct path
*parent_path
)
1598 LIST_HEAD(tree_list
);
1599 struct mount
*dest_mnt
= real_mount(path
->mnt
);
1600 struct dentry
*dest_dentry
= path
->dentry
;
1601 struct mount
*child
, *p
;
1604 if (IS_MNT_SHARED(&dest_mnt
->mnt
)) {
1605 err
= invent_group_ids(source_mnt
, true);
1609 err
= propagate_mnt(dest_mnt
, dest_dentry
, source_mnt
, &tree_list
);
1611 goto out_cleanup_ids
;
1613 br_write_lock(vfsmount_lock
);
1615 if (IS_MNT_SHARED(&dest_mnt
->mnt
)) {
1616 for (p
= source_mnt
; p
; p
= next_mnt(p
, &source_mnt
->mnt
))
1620 detach_mnt(source_mnt
, parent_path
);
1621 attach_mnt(source_mnt
, path
);
1622 touch_mnt_namespace(source_mnt
->mnt_ns
);
1624 mnt_set_mountpoint(dest_mnt
, dest_dentry
, source_mnt
);
1625 commit_tree(source_mnt
);
1628 list_for_each_entry_safe(child
, p
, &tree_list
, mnt_hash
) {
1629 list_del_init(&child
->mnt_hash
);
1632 br_write_unlock(vfsmount_lock
);
1637 if (IS_MNT_SHARED(&dest_mnt
->mnt
))
1638 cleanup_group_ids(source_mnt
, NULL
);
1643 static int lock_mount(struct path
*path
)
1645 struct vfsmount
*mnt
;
1647 mutex_lock(&path
->dentry
->d_inode
->i_mutex
);
1648 if (unlikely(cant_mount(path
->dentry
))) {
1649 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1652 down_write(&namespace_sem
);
1653 mnt
= lookup_mnt(path
);
1656 up_write(&namespace_sem
);
1657 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1660 path
->dentry
= dget(mnt
->mnt_root
);
1664 static void unlock_mount(struct path
*path
)
1666 up_write(&namespace_sem
);
1667 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1670 static int graft_tree(struct mount
*mnt
, struct path
*path
)
1672 if (mnt
->mnt
.mnt_sb
->s_flags
& MS_NOUSER
)
1675 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
1676 S_ISDIR(mnt
->mnt
.mnt_root
->d_inode
->i_mode
))
1679 if (d_unlinked(path
->dentry
))
1682 return attach_recursive_mnt(mnt
, path
, NULL
);
1686 * Sanity check the flags to change_mnt_propagation.
1689 static int flags_to_propagation_type(int flags
)
1691 int type
= flags
& ~(MS_REC
| MS_SILENT
);
1693 /* Fail if any non-propagation flags are set */
1694 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
1696 /* Only one propagation flag should be set */
1697 if (!is_power_of_2(type
))
1703 * recursively change the type of the mountpoint.
1705 static int do_change_type(struct path
*path
, int flag
)
1708 struct mount
*mnt
= real_mount(path
->mnt
);
1709 int recurse
= flag
& MS_REC
;
1713 if (!capable(CAP_SYS_ADMIN
))
1716 if (path
->dentry
!= path
->mnt
->mnt_root
)
1719 type
= flags_to_propagation_type(flag
);
1723 down_write(&namespace_sem
);
1724 if (type
== MS_SHARED
) {
1725 err
= invent_group_ids(mnt
, recurse
);
1730 br_write_lock(vfsmount_lock
);
1731 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, &mnt
->mnt
) : NULL
))
1732 change_mnt_propagation(m
, type
);
1733 br_write_unlock(vfsmount_lock
);
1736 up_write(&namespace_sem
);
1741 * do loopback mount.
1743 static int do_loopback(struct path
*path
, char *old_name
,
1746 LIST_HEAD(umount_list
);
1747 struct path old_path
;
1748 struct mount
*mnt
= NULL
, *old
;
1749 int err
= mount_is_safe(path
);
1752 if (!old_name
|| !*old_name
)
1754 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
1758 err
= lock_mount(path
);
1762 old
= real_mount(old_path
.mnt
);
1765 if (IS_MNT_UNBINDABLE(old_path
.mnt
))
1768 if (!check_mnt(real_mount(path
->mnt
)) || !check_mnt(old
))
1773 mnt
= copy_tree(old
, old_path
.dentry
, 0);
1775 mnt
= clone_mnt(old
, old_path
.dentry
, 0);
1780 err
= graft_tree(mnt
, path
);
1782 br_write_lock(vfsmount_lock
);
1783 umount_tree(mnt
, 0, &umount_list
);
1784 br_write_unlock(vfsmount_lock
);
1788 release_mounts(&umount_list
);
1790 path_put(&old_path
);
1794 static int change_mount_flags(struct vfsmount
*mnt
, int ms_flags
)
1797 int readonly_request
= 0;
1799 if (ms_flags
& MS_RDONLY
)
1800 readonly_request
= 1;
1801 if (readonly_request
== __mnt_is_readonly(mnt
))
1804 if (readonly_request
)
1805 error
= mnt_make_readonly(real_mount(mnt
));
1807 __mnt_unmake_readonly(real_mount(mnt
));
1812 * change filesystem flags. dir should be a physical root of filesystem.
1813 * If you've mounted a non-root directory somewhere and want to do remount
1814 * on it - tough luck.
1816 static int do_remount(struct path
*path
, int flags
, int mnt_flags
,
1820 struct super_block
*sb
= path
->mnt
->mnt_sb
;
1821 struct mount
*mnt
= real_mount(path
->mnt
);
1823 if (!capable(CAP_SYS_ADMIN
))
1826 if (!check_mnt(mnt
))
1829 if (path
->dentry
!= path
->mnt
->mnt_root
)
1832 err
= security_sb_remount(sb
, data
);
1836 down_write(&sb
->s_umount
);
1837 if (flags
& MS_BIND
)
1838 err
= change_mount_flags(path
->mnt
, flags
);
1840 err
= do_remount_sb(sb
, flags
, data
, 0);
1842 br_write_lock(vfsmount_lock
);
1843 mnt_flags
|= mnt
->mnt
.mnt_flags
& MNT_PROPAGATION_MASK
;
1844 mnt
->mnt
.mnt_flags
= mnt_flags
;
1845 br_write_unlock(vfsmount_lock
);
1847 up_write(&sb
->s_umount
);
1849 br_write_lock(vfsmount_lock
);
1850 touch_mnt_namespace(mnt
->mnt_ns
);
1851 br_write_unlock(vfsmount_lock
);
1856 static inline int tree_contains_unbindable(struct mount
*mnt
)
1859 for (p
= mnt
; p
; p
= next_mnt(p
, &mnt
->mnt
)) {
1860 if (IS_MNT_UNBINDABLE(&p
->mnt
))
1866 static int do_move_mount(struct path
*path
, char *old_name
)
1868 struct path old_path
, parent_path
;
1872 if (!capable(CAP_SYS_ADMIN
))
1874 if (!old_name
|| !*old_name
)
1876 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
1880 err
= lock_mount(path
);
1884 old
= real_mount(old_path
.mnt
);
1887 if (!check_mnt(real_mount(path
->mnt
)) || !check_mnt(old
))
1890 if (d_unlinked(path
->dentry
))
1894 if (old_path
.dentry
!= old_path
.mnt
->mnt_root
)
1897 if (!mnt_has_parent(old
))
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 (IS_MNT_SHARED(&old
->mnt_parent
->mnt
))
1909 * Don't move a mount tree containing unbindable mounts to a destination
1910 * mount which is shared.
1912 if (IS_MNT_SHARED(path
->mnt
) &&
1913 tree_contains_unbindable(old
))
1916 for (p
= real_mount(path
->mnt
); mnt_has_parent(p
); p
= p
->mnt_parent
)
1920 err
= attach_recursive_mnt(old
, path
, &parent_path
);
1924 /* if the mount is moved, it should no longer be expire
1926 list_del_init(&old
->mnt_expire
);
1931 path_put(&parent_path
);
1932 path_put(&old_path
);
1936 static struct vfsmount
*fs_set_subtype(struct vfsmount
*mnt
, const char *fstype
)
1939 const char *subtype
= strchr(fstype
, '.');
1948 mnt
->mnt_sb
->s_subtype
= kstrdup(subtype
, GFP_KERNEL
);
1950 if (!mnt
->mnt_sb
->s_subtype
)
1956 return ERR_PTR(err
);
1959 static struct vfsmount
*
1960 do_kern_mount(const char *fstype
, int flags
, const char *name
, void *data
)
1962 struct file_system_type
*type
= get_fs_type(fstype
);
1963 struct vfsmount
*mnt
;
1965 return ERR_PTR(-ENODEV
);
1966 mnt
= vfs_kern_mount(type
, flags
, name
, data
);
1967 if (!IS_ERR(mnt
) && (type
->fs_flags
& FS_HAS_SUBTYPE
) &&
1968 !mnt
->mnt_sb
->s_subtype
)
1969 mnt
= fs_set_subtype(mnt
, fstype
);
1970 put_filesystem(type
);
1975 * add a mount into a namespace's mount tree
1977 static int do_add_mount(struct mount
*newmnt
, struct path
*path
, int mnt_flags
)
1981 mnt_flags
&= ~(MNT_SHARED
| MNT_WRITE_HOLD
| MNT_INTERNAL
);
1983 err
= lock_mount(path
);
1988 if (!(mnt_flags
& MNT_SHRINKABLE
) && !check_mnt(real_mount(path
->mnt
)))
1991 /* Refuse the same filesystem on the same mount point */
1993 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
1994 path
->mnt
->mnt_root
== path
->dentry
)
1998 if (S_ISLNK(newmnt
->mnt
.mnt_root
->d_inode
->i_mode
))
2001 newmnt
->mnt
.mnt_flags
= mnt_flags
;
2002 err
= graft_tree(newmnt
, path
);
2010 * create a new mount for userspace and request it to be added into the
2013 static int do_new_mount(struct path
*path
, char *type
, int flags
,
2014 int mnt_flags
, char *name
, void *data
)
2016 struct vfsmount
*mnt
;
2022 /* we need capabilities... */
2023 if (!capable(CAP_SYS_ADMIN
))
2026 mnt
= do_kern_mount(type
, flags
, name
, data
);
2028 return PTR_ERR(mnt
);
2030 err
= do_add_mount(real_mount(mnt
), path
, mnt_flags
);
2036 int finish_automount(struct vfsmount
*m
, struct path
*path
)
2038 struct mount
*mnt
= real_mount(m
);
2040 /* The new mount record should have at least 2 refs to prevent it being
2041 * expired before we get a chance to add it
2043 BUG_ON(mnt_get_count(mnt
) < 2);
2045 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
2046 m
->mnt_root
== path
->dentry
) {
2051 err
= do_add_mount(mnt
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
2055 /* remove m from any expiration list it may be on */
2056 if (!list_empty(&mnt
->mnt_expire
)) {
2057 down_write(&namespace_sem
);
2058 br_write_lock(vfsmount_lock
);
2059 list_del_init(&mnt
->mnt_expire
);
2060 br_write_unlock(vfsmount_lock
);
2061 up_write(&namespace_sem
);
2069 * mnt_set_expiry - Put a mount on an expiration list
2070 * @mnt: The mount to list.
2071 * @expiry_list: The list to add the mount to.
2073 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
2075 down_write(&namespace_sem
);
2076 br_write_lock(vfsmount_lock
);
2078 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
2080 br_write_unlock(vfsmount_lock
);
2081 up_write(&namespace_sem
);
2083 EXPORT_SYMBOL(mnt_set_expiry
);
2086 * process a list of expirable mountpoints with the intent of discarding any
2087 * mountpoints that aren't in use and haven't been touched since last we came
2090 void mark_mounts_for_expiry(struct list_head
*mounts
)
2092 struct mount
*mnt
, *next
;
2093 LIST_HEAD(graveyard
);
2096 if (list_empty(mounts
))
2099 down_write(&namespace_sem
);
2100 br_write_lock(vfsmount_lock
);
2102 /* extract from the expiration list every vfsmount that matches the
2103 * following criteria:
2104 * - only referenced by its parent vfsmount
2105 * - still marked for expiry (marked on the last call here; marks are
2106 * cleared by mntput())
2108 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
2109 if (!xchg(&mnt
->mnt
.mnt_expiry_mark
, 1) ||
2110 propagate_mount_busy(mnt
, 1))
2112 list_move(&mnt
->mnt_expire
, &graveyard
);
2114 while (!list_empty(&graveyard
)) {
2115 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
2116 touch_mnt_namespace(mnt
->mnt_ns
);
2117 umount_tree(mnt
, 1, &umounts
);
2119 br_write_unlock(vfsmount_lock
);
2120 up_write(&namespace_sem
);
2122 release_mounts(&umounts
);
2125 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
2128 * Ripoff of 'select_parent()'
2130 * search the list of submounts for a given mountpoint, and move any
2131 * shrinkable submounts to the 'graveyard' list.
2133 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
2135 struct mount
*this_parent
= parent
;
2136 struct list_head
*next
;
2140 next
= this_parent
->mnt_mounts
.next
;
2142 while (next
!= &this_parent
->mnt_mounts
) {
2143 struct list_head
*tmp
= next
;
2144 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
2147 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
2150 * Descend a level if the d_mounts list is non-empty.
2152 if (!list_empty(&mnt
->mnt_mounts
)) {
2157 if (!propagate_mount_busy(mnt
, 1)) {
2158 list_move_tail(&mnt
->mnt_expire
, graveyard
);
2163 * All done at this level ... ascend and resume the search
2165 if (this_parent
!= parent
) {
2166 next
= this_parent
->mnt_child
.next
;
2167 this_parent
= this_parent
->mnt_parent
;
2174 * process a list of expirable mountpoints with the intent of discarding any
2175 * submounts of a specific parent mountpoint
2177 * vfsmount_lock must be held for write
2179 static void shrink_submounts(struct mount
*mnt
, struct list_head
*umounts
)
2181 LIST_HEAD(graveyard
);
2184 /* extract submounts of 'mountpoint' from the expiration list */
2185 while (select_submounts(mnt
, &graveyard
)) {
2186 while (!list_empty(&graveyard
)) {
2187 m
= list_first_entry(&graveyard
, struct mount
,
2189 touch_mnt_namespace(m
->mnt_ns
);
2190 umount_tree(m
, 1, umounts
);
2196 * Some copy_from_user() implementations do not return the exact number of
2197 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2198 * Note that this function differs from copy_from_user() in that it will oops
2199 * on bad values of `to', rather than returning a short copy.
2201 static long exact_copy_from_user(void *to
, const void __user
* from
,
2205 const char __user
*f
= from
;
2208 if (!access_ok(VERIFY_READ
, from
, n
))
2212 if (__get_user(c
, f
)) {
2223 int copy_mount_options(const void __user
* data
, unsigned long *where
)
2233 if (!(page
= __get_free_page(GFP_KERNEL
)))
2236 /* We only care that *some* data at the address the user
2237 * gave us is valid. Just in case, we'll zero
2238 * the remainder of the page.
2240 /* copy_from_user cannot cross TASK_SIZE ! */
2241 size
= TASK_SIZE
- (unsigned long)data
;
2242 if (size
> PAGE_SIZE
)
2245 i
= size
- exact_copy_from_user((void *)page
, data
, size
);
2251 memset((char *)page
+ i
, 0, PAGE_SIZE
- i
);
2256 int copy_mount_string(const void __user
*data
, char **where
)
2265 tmp
= strndup_user(data
, PAGE_SIZE
);
2267 return PTR_ERR(tmp
);
2274 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2275 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2277 * data is a (void *) that can point to any structure up to
2278 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2279 * information (or be NULL).
2281 * Pre-0.97 versions of mount() didn't have a flags word.
2282 * When the flags word was introduced its top half was required
2283 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2284 * Therefore, if this magic number is present, it carries no information
2285 * and must be discarded.
2287 long do_mount(char *dev_name
, char *dir_name
, char *type_page
,
2288 unsigned long flags
, void *data_page
)
2295 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
2296 flags
&= ~MS_MGC_MSK
;
2298 /* Basic sanity checks */
2300 if (!dir_name
|| !*dir_name
|| !memchr(dir_name
, 0, PAGE_SIZE
))
2304 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
2306 /* ... and get the mountpoint */
2307 retval
= kern_path(dir_name
, LOOKUP_FOLLOW
, &path
);
2311 retval
= security_sb_mount(dev_name
, &path
,
2312 type_page
, flags
, data_page
);
2316 /* Default to relatime unless overriden */
2317 if (!(flags
& MS_NOATIME
))
2318 mnt_flags
|= MNT_RELATIME
;
2320 /* Separate the per-mountpoint flags */
2321 if (flags
& MS_NOSUID
)
2322 mnt_flags
|= MNT_NOSUID
;
2323 if (flags
& MS_NODEV
)
2324 mnt_flags
|= MNT_NODEV
;
2325 if (flags
& MS_NOEXEC
)
2326 mnt_flags
|= MNT_NOEXEC
;
2327 if (flags
& MS_NOATIME
)
2328 mnt_flags
|= MNT_NOATIME
;
2329 if (flags
& MS_NODIRATIME
)
2330 mnt_flags
|= MNT_NODIRATIME
;
2331 if (flags
& MS_STRICTATIME
)
2332 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
2333 if (flags
& MS_RDONLY
)
2334 mnt_flags
|= MNT_READONLY
;
2336 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
| MS_BORN
|
2337 MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
| MS_KERNMOUNT
|
2340 if (flags
& MS_REMOUNT
)
2341 retval
= do_remount(&path
, flags
& ~MS_REMOUNT
, mnt_flags
,
2343 else if (flags
& MS_BIND
)
2344 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
2345 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2346 retval
= do_change_type(&path
, flags
);
2347 else if (flags
& MS_MOVE
)
2348 retval
= do_move_mount(&path
, dev_name
);
2350 retval
= do_new_mount(&path
, type_page
, flags
, mnt_flags
,
2351 dev_name
, data_page
);
2357 static struct mnt_namespace
*alloc_mnt_ns(void)
2359 struct mnt_namespace
*new_ns
;
2361 new_ns
= kmalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
2363 return ERR_PTR(-ENOMEM
);
2364 atomic_set(&new_ns
->count
, 1);
2365 new_ns
->root
= NULL
;
2366 INIT_LIST_HEAD(&new_ns
->list
);
2367 init_waitqueue_head(&new_ns
->poll
);
2372 void mnt_make_longterm(struct vfsmount
*mnt
)
2374 __mnt_make_longterm(real_mount(mnt
));
2377 void mnt_make_shortterm(struct vfsmount
*m
)
2380 struct mount
*mnt
= real_mount(m
);
2381 if (atomic_add_unless(&mnt
->mnt_longterm
, -1, 1))
2383 br_write_lock(vfsmount_lock
);
2384 atomic_dec(&mnt
->mnt_longterm
);
2385 br_write_unlock(vfsmount_lock
);
2390 * Allocate a new namespace structure and populate it with contents
2391 * copied from the namespace of the passed in task structure.
2393 static struct mnt_namespace
*dup_mnt_ns(struct mnt_namespace
*mnt_ns
,
2394 struct fs_struct
*fs
)
2396 struct mnt_namespace
*new_ns
;
2397 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
2398 struct mount
*p
, *q
;
2401 new_ns
= alloc_mnt_ns();
2405 down_write(&namespace_sem
);
2406 /* First pass: copy the tree topology */
2407 new = copy_tree(real_mount(mnt_ns
->root
), mnt_ns
->root
->mnt_root
,
2408 CL_COPY_ALL
| CL_EXPIRE
);
2410 up_write(&namespace_sem
);
2412 return ERR_PTR(-ENOMEM
);
2414 new_ns
->root
= &new->mnt
;
2415 br_write_lock(vfsmount_lock
);
2416 list_add_tail(&new_ns
->list
, &new_ns
->root
->mnt_list
);
2417 br_write_unlock(vfsmount_lock
);
2420 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2421 * as belonging to new namespace. We have already acquired a private
2422 * fs_struct, so tsk->fs->lock is not needed.
2424 p
= real_mount(mnt_ns
->root
);
2428 __mnt_make_longterm(q
);
2430 if (&p
->mnt
== fs
->root
.mnt
) {
2431 fs
->root
.mnt
= mntget(&q
->mnt
);
2432 __mnt_make_longterm(q
);
2433 mnt_make_shortterm(&p
->mnt
);
2436 if (&p
->mnt
== fs
->pwd
.mnt
) {
2437 fs
->pwd
.mnt
= mntget(&q
->mnt
);
2438 __mnt_make_longterm(q
);
2439 mnt_make_shortterm(&p
->mnt
);
2443 p
= next_mnt(p
, mnt_ns
->root
);
2444 q
= next_mnt(q
, new_ns
->root
);
2446 up_write(&namespace_sem
);
2456 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
2457 struct fs_struct
*new_fs
)
2459 struct mnt_namespace
*new_ns
;
2464 if (!(flags
& CLONE_NEWNS
))
2467 new_ns
= dup_mnt_ns(ns
, new_fs
);
2474 * create_mnt_ns - creates a private namespace and adds a root filesystem
2475 * @mnt: pointer to the new root filesystem mountpoint
2477 static struct mnt_namespace
*create_mnt_ns(struct vfsmount
*mnt
)
2479 struct mnt_namespace
*new_ns
;
2481 new_ns
= alloc_mnt_ns();
2482 if (!IS_ERR(new_ns
)) {
2483 real_mount(mnt
)->mnt_ns
= new_ns
;
2484 __mnt_make_longterm(real_mount(mnt
));
2486 list_add(&new_ns
->list
, &new_ns
->root
->mnt_list
);
2493 struct dentry
*mount_subtree(struct vfsmount
*mnt
, const char *name
)
2495 struct mnt_namespace
*ns
;
2496 struct super_block
*s
;
2500 ns
= create_mnt_ns(mnt
);
2502 return ERR_CAST(ns
);
2504 err
= vfs_path_lookup(mnt
->mnt_root
, mnt
,
2505 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
2510 return ERR_PTR(err
);
2512 /* trade a vfsmount reference for active sb one */
2513 s
= path
.mnt
->mnt_sb
;
2514 atomic_inc(&s
->s_active
);
2516 /* lock the sucker */
2517 down_write(&s
->s_umount
);
2518 /* ... and return the root of (sub)tree on it */
2521 EXPORT_SYMBOL(mount_subtree
);
2523 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
2524 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
2530 unsigned long data_page
;
2532 ret
= copy_mount_string(type
, &kernel_type
);
2536 kernel_dir
= getname(dir_name
);
2537 if (IS_ERR(kernel_dir
)) {
2538 ret
= PTR_ERR(kernel_dir
);
2542 ret
= copy_mount_string(dev_name
, &kernel_dev
);
2546 ret
= copy_mount_options(data
, &data_page
);
2550 ret
= do_mount(kernel_dev
, kernel_dir
, kernel_type
, flags
,
2551 (void *) data_page
);
2553 free_page(data_page
);
2557 putname(kernel_dir
);
2565 * Return true if path is reachable from root
2567 * namespace_sem or vfsmount_lock is held
2569 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
2570 const struct path
*root
)
2572 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
2573 dentry
= mnt
->mnt_mountpoint
;
2574 mnt
= mnt
->mnt_parent
;
2576 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
2579 int path_is_under(struct path
*path1
, struct path
*path2
)
2582 br_read_lock(vfsmount_lock
);
2583 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
2584 br_read_unlock(vfsmount_lock
);
2587 EXPORT_SYMBOL(path_is_under
);
2590 * pivot_root Semantics:
2591 * Moves the root file system of the current process to the directory put_old,
2592 * makes new_root as the new root file system of the current process, and sets
2593 * root/cwd of all processes which had them on the current root to new_root.
2596 * The new_root and put_old must be directories, and must not be on the
2597 * same file system as the current process root. The put_old must be
2598 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2599 * pointed to by put_old must yield the same directory as new_root. No other
2600 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2602 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2603 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2604 * in this situation.
2607 * - we don't move root/cwd if they are not at the root (reason: if something
2608 * cared enough to change them, it's probably wrong to force them elsewhere)
2609 * - it's okay to pick a root that isn't the root of a file system, e.g.
2610 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2611 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2614 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
2615 const char __user
*, put_old
)
2617 struct path
new, old
, parent_path
, root_parent
, root
;
2618 struct mount
*new_mnt
, *root_mnt
;
2621 if (!capable(CAP_SYS_ADMIN
))
2624 error
= user_path_dir(new_root
, &new);
2628 error
= user_path_dir(put_old
, &old
);
2632 error
= security_sb_pivotroot(&old
, &new);
2636 get_fs_root(current
->fs
, &root
);
2637 error
= lock_mount(&old
);
2642 new_mnt
= real_mount(new.mnt
);
2643 root_mnt
= real_mount(root
.mnt
);
2644 if (IS_MNT_SHARED(old
.mnt
) ||
2645 IS_MNT_SHARED(&new_mnt
->mnt_parent
->mnt
) ||
2646 IS_MNT_SHARED(&root_mnt
->mnt_parent
->mnt
))
2648 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
2651 if (d_unlinked(new.dentry
))
2653 if (d_unlinked(old
.dentry
))
2656 if (new.mnt
== root
.mnt
||
2657 old
.mnt
== root
.mnt
)
2658 goto out4
; /* loop, on the same file system */
2660 if (root
.mnt
->mnt_root
!= root
.dentry
)
2661 goto out4
; /* not a mountpoint */
2662 if (!mnt_has_parent(root_mnt
))
2663 goto out4
; /* not attached */
2664 if (new.mnt
->mnt_root
!= new.dentry
)
2665 goto out4
; /* not a mountpoint */
2666 if (!mnt_has_parent(new_mnt
))
2667 goto out4
; /* not attached */
2668 /* make sure we can reach put_old from new_root */
2669 if (!is_path_reachable(real_mount(old
.mnt
), old
.dentry
, &new))
2671 br_write_lock(vfsmount_lock
);
2672 detach_mnt(new_mnt
, &parent_path
);
2673 detach_mnt(root_mnt
, &root_parent
);
2674 /* mount old root on put_old */
2675 attach_mnt(root_mnt
, &old
);
2676 /* mount new_root on / */
2677 attach_mnt(new_mnt
, &root_parent
);
2678 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
2679 br_write_unlock(vfsmount_lock
);
2680 chroot_fs_refs(&root
, &new);
2685 path_put(&root_parent
);
2686 path_put(&parent_path
);
2698 static void __init
init_mount_tree(void)
2700 struct vfsmount
*mnt
;
2701 struct mnt_namespace
*ns
;
2704 mnt
= do_kern_mount("rootfs", 0, "rootfs", NULL
);
2706 panic("Can't create rootfs");
2708 ns
= create_mnt_ns(mnt
);
2710 panic("Can't allocate initial namespace");
2712 init_task
.nsproxy
->mnt_ns
= ns
;
2715 root
.mnt
= ns
->root
;
2716 root
.dentry
= ns
->root
->mnt_root
;
2718 set_fs_pwd(current
->fs
, &root
);
2719 set_fs_root(current
->fs
, &root
);
2722 void __init
mnt_init(void)
2727 init_rwsem(&namespace_sem
);
2729 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
2730 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
2732 mount_hashtable
= (struct list_head
*)__get_free_page(GFP_ATOMIC
);
2734 if (!mount_hashtable
)
2735 panic("Failed to allocate mount hash table\n");
2737 printk(KERN_INFO
"Mount-cache hash table entries: %lu\n", HASH_SIZE
);
2739 for (u
= 0; u
< HASH_SIZE
; u
++)
2740 INIT_LIST_HEAD(&mount_hashtable
[u
]);
2742 br_lock_init(vfsmount_lock
);
2746 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
2748 fs_kobj
= kobject_create_and_add("fs", NULL
);
2750 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
2755 void put_mnt_ns(struct mnt_namespace
*ns
)
2757 LIST_HEAD(umount_list
);
2759 if (!atomic_dec_and_test(&ns
->count
))
2761 down_write(&namespace_sem
);
2762 br_write_lock(vfsmount_lock
);
2763 umount_tree(real_mount(ns
->root
), 0, &umount_list
);
2764 br_write_unlock(vfsmount_lock
);
2765 up_write(&namespace_sem
);
2766 release_mounts(&umount_list
);
2770 struct vfsmount
*kern_mount_data(struct file_system_type
*type
, void *data
)
2772 struct vfsmount
*mnt
;
2773 mnt
= vfs_kern_mount(type
, MS_KERNMOUNT
, type
->name
, data
);
2776 * it is a longterm mount, don't release mnt until
2777 * we unmount before file sys is unregistered
2779 mnt_make_longterm(mnt
);
2783 EXPORT_SYMBOL_GPL(kern_mount_data
);
2785 void kern_unmount(struct vfsmount
*mnt
)
2787 /* release long term mount so mount point can be released */
2788 if (!IS_ERR_OR_NULL(mnt
)) {
2789 mnt_make_shortterm(mnt
);
2793 EXPORT_SYMBOL(kern_unmount
);
2795 bool our_mnt(struct vfsmount
*mnt
)
2797 return check_mnt(real_mount(mnt
));