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
);
156 * vfsmount lock must be held for write
158 unsigned int mnt_get_count(struct vfsmount
*mnt
)
161 unsigned int count
= 0;
164 for_each_possible_cpu(cpu
) {
165 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_count
;
170 return mnt
->mnt_count
;
174 static struct vfsmount
*alloc_vfsmnt(const char *name
)
176 struct vfsmount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
180 err
= mnt_alloc_id(mnt
);
185 mnt
->mnt_devname
= kstrdup(name
, GFP_KERNEL
);
186 if (!mnt
->mnt_devname
)
191 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
193 goto out_free_devname
;
195 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
198 mnt
->mnt_writers
= 0;
201 INIT_LIST_HEAD(&mnt
->mnt_hash
);
202 INIT_LIST_HEAD(&mnt
->mnt_child
);
203 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
204 INIT_LIST_HEAD(&mnt
->mnt_list
);
205 INIT_LIST_HEAD(&mnt
->mnt_expire
);
206 INIT_LIST_HEAD(&mnt
->mnt_share
);
207 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
208 INIT_LIST_HEAD(&mnt
->mnt_slave
);
209 #ifdef CONFIG_FSNOTIFY
210 INIT_HLIST_HEAD(&mnt
->mnt_fsnotify_marks
);
217 kfree(mnt
->mnt_devname
);
222 kmem_cache_free(mnt_cache
, mnt
);
227 * Most r/o checks on a fs are for operations that take
228 * discrete amounts of time, like a write() or unlink().
229 * We must keep track of when those operations start
230 * (for permission checks) and when they end, so that
231 * we can determine when writes are able to occur to
235 * __mnt_is_readonly: check whether a mount is read-only
236 * @mnt: the mount to check for its write status
238 * This shouldn't be used directly ouside of the VFS.
239 * It does not guarantee that the filesystem will stay
240 * r/w, just that it is right *now*. This can not and
241 * should not be used in place of IS_RDONLY(inode).
242 * mnt_want/drop_write() will _keep_ the filesystem
245 int __mnt_is_readonly(struct vfsmount
*mnt
)
247 if (mnt
->mnt_flags
& MNT_READONLY
)
249 if (mnt
->mnt_sb
->s_flags
& MS_RDONLY
)
253 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
255 static inline void mnt_inc_writers(struct vfsmount
*mnt
)
258 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
264 static inline void mnt_dec_writers(struct vfsmount
*mnt
)
267 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
273 static unsigned int mnt_get_writers(struct vfsmount
*mnt
)
276 unsigned int count
= 0;
279 for_each_possible_cpu(cpu
) {
280 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_writers
;
285 return mnt
->mnt_writers
;
290 * Most r/o checks on a fs are for operations that take
291 * discrete amounts of time, like a write() or unlink().
292 * We must keep track of when those operations start
293 * (for permission checks) and when they end, so that
294 * we can determine when writes are able to occur to
298 * mnt_want_write - get write access to a mount
299 * @mnt: the mount on which to take a write
301 * This tells the low-level filesystem that a write is
302 * about to be performed to it, and makes sure that
303 * writes are allowed before returning success. When
304 * the write operation is finished, mnt_drop_write()
305 * must be called. This is effectively a refcount.
307 int mnt_want_write(struct vfsmount
*mnt
)
312 mnt_inc_writers(mnt
);
314 * The store to mnt_inc_writers must be visible before we pass
315 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
316 * incremented count after it has set MNT_WRITE_HOLD.
319 while (mnt
->mnt_flags
& MNT_WRITE_HOLD
)
322 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
323 * be set to match its requirements. So we must not load that until
324 * MNT_WRITE_HOLD is cleared.
327 if (__mnt_is_readonly(mnt
)) {
328 mnt_dec_writers(mnt
);
336 EXPORT_SYMBOL_GPL(mnt_want_write
);
339 * mnt_clone_write - get write access to a mount
340 * @mnt: the mount on which to take a write
342 * This is effectively like mnt_want_write, except
343 * it must only be used to take an extra write reference
344 * on a mountpoint that we already know has a write reference
345 * on it. This allows some optimisation.
347 * After finished, mnt_drop_write must be called as usual to
348 * drop the reference.
350 int mnt_clone_write(struct vfsmount
*mnt
)
352 /* superblock may be r/o */
353 if (__mnt_is_readonly(mnt
))
356 mnt_inc_writers(mnt
);
360 EXPORT_SYMBOL_GPL(mnt_clone_write
);
363 * mnt_want_write_file - get write access to a file's mount
364 * @file: the file who's mount on which to take a write
366 * This is like mnt_want_write, but it takes a file and can
367 * do some optimisations if the file is open for write already
369 int mnt_want_write_file(struct file
*file
)
371 struct inode
*inode
= file
->f_dentry
->d_inode
;
372 if (!(file
->f_mode
& FMODE_WRITE
) || special_file(inode
->i_mode
))
373 return mnt_want_write(file
->f_path
.mnt
);
375 return mnt_clone_write(file
->f_path
.mnt
);
377 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
380 * mnt_drop_write - give up write access to a mount
381 * @mnt: the mount on which to give up write access
383 * Tells the low-level filesystem that we are done
384 * performing writes to it. Must be matched with
385 * mnt_want_write() call above.
387 void mnt_drop_write(struct vfsmount
*mnt
)
390 mnt_dec_writers(mnt
);
393 EXPORT_SYMBOL_GPL(mnt_drop_write
);
395 void mnt_drop_write_file(struct file
*file
)
397 mnt_drop_write(file
->f_path
.mnt
);
399 EXPORT_SYMBOL(mnt_drop_write_file
);
401 static int mnt_make_readonly(struct vfsmount
*mnt
)
405 br_write_lock(vfsmount_lock
);
406 mnt
->mnt_flags
|= MNT_WRITE_HOLD
;
408 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
409 * should be visible before we do.
414 * With writers on hold, if this value is zero, then there are
415 * definitely no active writers (although held writers may subsequently
416 * increment the count, they'll have to wait, and decrement it after
417 * seeing MNT_READONLY).
419 * It is OK to have counter incremented on one CPU and decremented on
420 * another: the sum will add up correctly. The danger would be when we
421 * sum up each counter, if we read a counter before it is incremented,
422 * but then read another CPU's count which it has been subsequently
423 * decremented from -- we would see more decrements than we should.
424 * MNT_WRITE_HOLD protects against this scenario, because
425 * mnt_want_write first increments count, then smp_mb, then spins on
426 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
427 * we're counting up here.
429 if (mnt_get_writers(mnt
) > 0)
432 mnt
->mnt_flags
|= MNT_READONLY
;
434 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
435 * that become unheld will see MNT_READONLY.
438 mnt
->mnt_flags
&= ~MNT_WRITE_HOLD
;
439 br_write_unlock(vfsmount_lock
);
443 static void __mnt_unmake_readonly(struct vfsmount
*mnt
)
445 br_write_lock(vfsmount_lock
);
446 mnt
->mnt_flags
&= ~MNT_READONLY
;
447 br_write_unlock(vfsmount_lock
);
450 static void free_vfsmnt(struct vfsmount
*mnt
)
452 kfree(mnt
->mnt_devname
);
455 free_percpu(mnt
->mnt_pcp
);
457 kmem_cache_free(mnt_cache
, mnt
);
461 * find the first or last mount at @dentry on vfsmount @mnt depending on
462 * @dir. If @dir is set return the first mount else return the last mount.
463 * vfsmount_lock must be held for read or write.
465 struct vfsmount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
,
468 struct list_head
*head
= mount_hashtable
+ hash(mnt
, dentry
);
469 struct list_head
*tmp
= head
;
470 struct vfsmount
*p
, *found
= NULL
;
473 tmp
= dir
? tmp
->next
: tmp
->prev
;
477 p
= list_entry(tmp
, struct vfsmount
, mnt_hash
);
478 if (p
->mnt_parent
== mnt
&& p
->mnt_mountpoint
== dentry
) {
487 * lookup_mnt increments the ref count before returning
488 * the vfsmount struct.
490 struct vfsmount
*lookup_mnt(struct path
*path
)
492 struct vfsmount
*child_mnt
;
494 br_read_lock(vfsmount_lock
);
495 if ((child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
, 1)))
497 br_read_unlock(vfsmount_lock
);
501 static inline int check_mnt(struct vfsmount
*mnt
)
503 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
507 * vfsmount lock must be held for write
509 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
513 wake_up_interruptible(&ns
->poll
);
518 * vfsmount lock must be held for write
520 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
522 if (ns
&& ns
->event
!= event
) {
524 wake_up_interruptible(&ns
->poll
);
529 * Clear dentry's mounted state if it has no remaining mounts.
530 * vfsmount_lock must be held for write.
532 static void dentry_reset_mounted(struct dentry
*dentry
)
536 for (u
= 0; u
< HASH_SIZE
; u
++) {
539 list_for_each_entry(p
, &mount_hashtable
[u
], mnt_hash
) {
540 if (p
->mnt_mountpoint
== dentry
)
544 spin_lock(&dentry
->d_lock
);
545 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
546 spin_unlock(&dentry
->d_lock
);
550 * vfsmount lock must be held for write
552 static void detach_mnt(struct vfsmount
*mnt
, struct path
*old_path
)
554 old_path
->dentry
= mnt
->mnt_mountpoint
;
555 old_path
->mnt
= mnt
->mnt_parent
;
556 mnt
->mnt_parent
= mnt
;
557 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
558 list_del_init(&mnt
->mnt_child
);
559 list_del_init(&mnt
->mnt_hash
);
560 dentry_reset_mounted(old_path
->dentry
);
564 * vfsmount lock must be held for write
566 void mnt_set_mountpoint(struct vfsmount
*mnt
, struct dentry
*dentry
,
567 struct vfsmount
*child_mnt
)
569 child_mnt
->mnt_parent
= mntget(mnt
);
570 child_mnt
->mnt_mountpoint
= dget(dentry
);
571 spin_lock(&dentry
->d_lock
);
572 dentry
->d_flags
|= DCACHE_MOUNTED
;
573 spin_unlock(&dentry
->d_lock
);
577 * vfsmount lock must be held for write
579 static void attach_mnt(struct vfsmount
*mnt
, struct path
*path
)
581 mnt_set_mountpoint(path
->mnt
, path
->dentry
, mnt
);
582 list_add_tail(&mnt
->mnt_hash
, mount_hashtable
+
583 hash(path
->mnt
, path
->dentry
));
584 list_add_tail(&mnt
->mnt_child
, &path
->mnt
->mnt_mounts
);
587 static inline void __mnt_make_longterm(struct vfsmount
*mnt
)
590 atomic_inc(&mnt
->mnt_longterm
);
594 /* needs vfsmount lock for write */
595 static inline void __mnt_make_shortterm(struct vfsmount
*mnt
)
598 atomic_dec(&mnt
->mnt_longterm
);
603 * vfsmount lock must be held for write
605 static void commit_tree(struct vfsmount
*mnt
)
607 struct vfsmount
*parent
= mnt
->mnt_parent
;
610 struct mnt_namespace
*n
= parent
->mnt_ns
;
612 BUG_ON(parent
== mnt
);
614 list_add_tail(&head
, &mnt
->mnt_list
);
615 list_for_each_entry(m
, &head
, mnt_list
) {
617 __mnt_make_longterm(m
);
620 list_splice(&head
, n
->list
.prev
);
622 list_add_tail(&mnt
->mnt_hash
, mount_hashtable
+
623 hash(parent
, mnt
->mnt_mountpoint
));
624 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
625 touch_mnt_namespace(n
);
628 static struct vfsmount
*next_mnt(struct vfsmount
*p
, struct vfsmount
*root
)
630 struct list_head
*next
= p
->mnt_mounts
.next
;
631 if (next
== &p
->mnt_mounts
) {
635 next
= p
->mnt_child
.next
;
636 if (next
!= &p
->mnt_parent
->mnt_mounts
)
641 return list_entry(next
, struct vfsmount
, mnt_child
);
644 static struct vfsmount
*skip_mnt_tree(struct vfsmount
*p
)
646 struct list_head
*prev
= p
->mnt_mounts
.prev
;
647 while (prev
!= &p
->mnt_mounts
) {
648 p
= list_entry(prev
, struct vfsmount
, mnt_child
);
649 prev
= p
->mnt_mounts
.prev
;
655 vfs_kern_mount(struct file_system_type
*type
, int flags
, const char *name
, void *data
)
657 struct vfsmount
*mnt
;
661 return ERR_PTR(-ENODEV
);
663 mnt
= alloc_vfsmnt(name
);
665 return ERR_PTR(-ENOMEM
);
667 if (flags
& MS_KERNMOUNT
)
668 mnt
->mnt_flags
= MNT_INTERNAL
;
670 root
= mount_fs(type
, flags
, name
, data
);
673 return ERR_CAST(root
);
676 mnt
->mnt_root
= root
;
677 mnt
->mnt_sb
= root
->d_sb
;
678 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
679 mnt
->mnt_parent
= mnt
;
682 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
684 static struct vfsmount
*clone_mnt(struct vfsmount
*old
, struct dentry
*root
,
687 struct super_block
*sb
= old
->mnt_sb
;
688 struct vfsmount
*mnt
= alloc_vfsmnt(old
->mnt_devname
);
691 if (flag
& (CL_SLAVE
| CL_PRIVATE
))
692 mnt
->mnt_group_id
= 0; /* not a peer of original */
694 mnt
->mnt_group_id
= old
->mnt_group_id
;
696 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
697 int err
= mnt_alloc_group_id(mnt
);
702 mnt
->mnt_flags
= old
->mnt_flags
& ~MNT_WRITE_HOLD
;
703 atomic_inc(&sb
->s_active
);
705 mnt
->mnt_root
= dget(root
);
706 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
707 mnt
->mnt_parent
= mnt
;
709 if (flag
& CL_SLAVE
) {
710 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
711 mnt
->mnt_master
= old
;
712 CLEAR_MNT_SHARED(mnt
);
713 } else if (!(flag
& CL_PRIVATE
)) {
714 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
715 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
716 if (IS_MNT_SLAVE(old
))
717 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
718 mnt
->mnt_master
= old
->mnt_master
;
720 if (flag
& CL_MAKE_SHARED
)
723 /* stick the duplicate mount on the same expiry list
724 * as the original if that was on one */
725 if (flag
& CL_EXPIRE
) {
726 if (!list_empty(&old
->mnt_expire
))
727 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
737 static inline void mntfree(struct vfsmount
*mnt
)
739 struct super_block
*sb
= mnt
->mnt_sb
;
742 * This probably indicates that somebody messed
743 * up a mnt_want/drop_write() pair. If this
744 * happens, the filesystem was probably unable
745 * to make r/w->r/o transitions.
748 * The locking used to deal with mnt_count decrement provides barriers,
749 * so mnt_get_writers() below is safe.
751 WARN_ON(mnt_get_writers(mnt
));
752 fsnotify_vfsmount_delete(mnt
);
755 deactivate_super(sb
);
758 static void mntput_no_expire(struct vfsmount
*mnt
)
762 br_read_lock(vfsmount_lock
);
763 if (likely(atomic_read(&mnt
->mnt_longterm
))) {
764 mnt_add_count(mnt
, -1);
765 br_read_unlock(vfsmount_lock
);
768 br_read_unlock(vfsmount_lock
);
770 br_write_lock(vfsmount_lock
);
771 mnt_add_count(mnt
, -1);
772 if (mnt_get_count(mnt
)) {
773 br_write_unlock(vfsmount_lock
);
777 mnt_add_count(mnt
, -1);
778 if (likely(mnt_get_count(mnt
)))
780 br_write_lock(vfsmount_lock
);
782 if (unlikely(mnt
->mnt_pinned
)) {
783 mnt_add_count(mnt
, mnt
->mnt_pinned
+ 1);
785 br_write_unlock(vfsmount_lock
);
786 acct_auto_close_mnt(mnt
);
789 br_write_unlock(vfsmount_lock
);
793 void mntput(struct vfsmount
*mnt
)
796 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
797 if (unlikely(mnt
->mnt_expiry_mark
))
798 mnt
->mnt_expiry_mark
= 0;
799 mntput_no_expire(mnt
);
802 EXPORT_SYMBOL(mntput
);
804 struct vfsmount
*mntget(struct vfsmount
*mnt
)
807 mnt_add_count(mnt
, 1);
810 EXPORT_SYMBOL(mntget
);
812 void mnt_pin(struct vfsmount
*mnt
)
814 br_write_lock(vfsmount_lock
);
816 br_write_unlock(vfsmount_lock
);
818 EXPORT_SYMBOL(mnt_pin
);
820 void mnt_unpin(struct vfsmount
*mnt
)
822 br_write_lock(vfsmount_lock
);
823 if (mnt
->mnt_pinned
) {
824 mnt_add_count(mnt
, 1);
827 br_write_unlock(vfsmount_lock
);
829 EXPORT_SYMBOL(mnt_unpin
);
831 static inline void mangle(struct seq_file
*m
, const char *s
)
833 seq_escape(m
, s
, " \t\n\\");
837 * Simple .show_options callback for filesystems which don't want to
838 * implement more complex mount option showing.
840 * See also save_mount_options().
842 int generic_show_options(struct seq_file
*m
, struct vfsmount
*mnt
)
847 options
= rcu_dereference(mnt
->mnt_sb
->s_options
);
849 if (options
!= NULL
&& options
[0]) {
857 EXPORT_SYMBOL(generic_show_options
);
860 * If filesystem uses generic_show_options(), this function should be
861 * called from the fill_super() callback.
863 * The .remount_fs callback usually needs to be handled in a special
864 * way, to make sure, that previous options are not overwritten if the
867 * Also note, that if the filesystem's .remount_fs function doesn't
868 * reset all options to their default value, but changes only newly
869 * given options, then the displayed options will not reflect reality
872 void save_mount_options(struct super_block
*sb
, char *options
)
874 BUG_ON(sb
->s_options
);
875 rcu_assign_pointer(sb
->s_options
, kstrdup(options
, GFP_KERNEL
));
877 EXPORT_SYMBOL(save_mount_options
);
879 void replace_mount_options(struct super_block
*sb
, char *options
)
881 char *old
= sb
->s_options
;
882 rcu_assign_pointer(sb
->s_options
, options
);
888 EXPORT_SYMBOL(replace_mount_options
);
890 #ifdef CONFIG_PROC_FS
892 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
894 struct proc_mounts
*p
= m
->private;
896 down_read(&namespace_sem
);
897 return seq_list_start(&p
->ns
->list
, *pos
);
900 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
902 struct proc_mounts
*p
= m
->private;
904 return seq_list_next(v
, &p
->ns
->list
, pos
);
907 static void m_stop(struct seq_file
*m
, void *v
)
909 up_read(&namespace_sem
);
912 int mnt_had_events(struct proc_mounts
*p
)
914 struct mnt_namespace
*ns
= p
->ns
;
917 br_read_lock(vfsmount_lock
);
918 if (p
->m
.poll_event
!= ns
->event
) {
919 p
->m
.poll_event
= ns
->event
;
922 br_read_unlock(vfsmount_lock
);
927 struct proc_fs_info
{
932 static int show_sb_opts(struct seq_file
*m
, struct super_block
*sb
)
934 static const struct proc_fs_info fs_info
[] = {
935 { MS_SYNCHRONOUS
, ",sync" },
936 { MS_DIRSYNC
, ",dirsync" },
937 { MS_MANDLOCK
, ",mand" },
940 const struct proc_fs_info
*fs_infop
;
942 for (fs_infop
= fs_info
; fs_infop
->flag
; fs_infop
++) {
943 if (sb
->s_flags
& fs_infop
->flag
)
944 seq_puts(m
, fs_infop
->str
);
947 return security_sb_show_options(m
, sb
);
950 static void show_mnt_opts(struct seq_file
*m
, struct vfsmount
*mnt
)
952 static const struct proc_fs_info mnt_info
[] = {
953 { MNT_NOSUID
, ",nosuid" },
954 { MNT_NODEV
, ",nodev" },
955 { MNT_NOEXEC
, ",noexec" },
956 { MNT_NOATIME
, ",noatime" },
957 { MNT_NODIRATIME
, ",nodiratime" },
958 { MNT_RELATIME
, ",relatime" },
961 const struct proc_fs_info
*fs_infop
;
963 for (fs_infop
= mnt_info
; fs_infop
->flag
; fs_infop
++) {
964 if (mnt
->mnt_flags
& fs_infop
->flag
)
965 seq_puts(m
, fs_infop
->str
);
969 static void show_type(struct seq_file
*m
, struct super_block
*sb
)
971 mangle(m
, sb
->s_type
->name
);
972 if (sb
->s_subtype
&& sb
->s_subtype
[0]) {
974 mangle(m
, sb
->s_subtype
);
978 static int show_vfsmnt(struct seq_file
*m
, void *v
)
980 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
982 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
984 if (mnt
->mnt_sb
->s_op
->show_devname
) {
985 err
= mnt
->mnt_sb
->s_op
->show_devname(m
, mnt
);
989 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
992 seq_path(m
, &mnt_path
, " \t\n\\");
994 show_type(m
, mnt
->mnt_sb
);
995 seq_puts(m
, __mnt_is_readonly(mnt
) ? " ro" : " rw");
996 err
= show_sb_opts(m
, mnt
->mnt_sb
);
999 show_mnt_opts(m
, mnt
);
1000 if (mnt
->mnt_sb
->s_op
->show_options
)
1001 err
= mnt
->mnt_sb
->s_op
->show_options(m
, mnt
);
1002 seq_puts(m
, " 0 0\n");
1007 const struct seq_operations mounts_op
= {
1014 static int show_mountinfo(struct seq_file
*m
, void *v
)
1016 struct proc_mounts
*p
= m
->private;
1017 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
1018 struct super_block
*sb
= mnt
->mnt_sb
;
1019 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
1020 struct path root
= p
->root
;
1023 seq_printf(m
, "%i %i %u:%u ", mnt
->mnt_id
, mnt
->mnt_parent
->mnt_id
,
1024 MAJOR(sb
->s_dev
), MINOR(sb
->s_dev
));
1025 if (sb
->s_op
->show_path
)
1026 err
= sb
->s_op
->show_path(m
, mnt
);
1028 seq_dentry(m
, mnt
->mnt_root
, " \t\n\\");
1033 /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
1034 err
= seq_path_root(m
, &mnt_path
, &root
, " \t\n\\");
1038 seq_puts(m
, mnt
->mnt_flags
& MNT_READONLY
? " ro" : " rw");
1039 show_mnt_opts(m
, mnt
);
1041 /* Tagged fields ("foo:X" or "bar") */
1042 if (IS_MNT_SHARED(mnt
))
1043 seq_printf(m
, " shared:%i", mnt
->mnt_group_id
);
1044 if (IS_MNT_SLAVE(mnt
)) {
1045 int master
= mnt
->mnt_master
->mnt_group_id
;
1046 int dom
= get_dominating_id(mnt
, &p
->root
);
1047 seq_printf(m
, " master:%i", master
);
1048 if (dom
&& dom
!= master
)
1049 seq_printf(m
, " propagate_from:%i", dom
);
1051 if (IS_MNT_UNBINDABLE(mnt
))
1052 seq_puts(m
, " unbindable");
1054 /* Filesystem specific data */
1058 if (sb
->s_op
->show_devname
)
1059 err
= sb
->s_op
->show_devname(m
, mnt
);
1061 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
1064 seq_puts(m
, sb
->s_flags
& MS_RDONLY
? " ro" : " rw");
1065 err
= show_sb_opts(m
, sb
);
1068 if (sb
->s_op
->show_options
)
1069 err
= sb
->s_op
->show_options(m
, mnt
);
1075 const struct seq_operations mountinfo_op
= {
1079 .show
= show_mountinfo
,
1082 static int show_vfsstat(struct seq_file
*m
, void *v
)
1084 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
1085 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
1089 if (mnt
->mnt_sb
->s_op
->show_devname
) {
1090 seq_puts(m
, "device ");
1091 err
= mnt
->mnt_sb
->s_op
->show_devname(m
, mnt
);
1093 if (mnt
->mnt_devname
) {
1094 seq_puts(m
, "device ");
1095 mangle(m
, mnt
->mnt_devname
);
1097 seq_puts(m
, "no device");
1101 seq_puts(m
, " mounted on ");
1102 seq_path(m
, &mnt_path
, " \t\n\\");
1105 /* file system type */
1106 seq_puts(m
, "with fstype ");
1107 show_type(m
, mnt
->mnt_sb
);
1109 /* optional statistics */
1110 if (mnt
->mnt_sb
->s_op
->show_stats
) {
1113 err
= mnt
->mnt_sb
->s_op
->show_stats(m
, mnt
);
1120 const struct seq_operations mountstats_op
= {
1124 .show
= show_vfsstat
,
1126 #endif /* CONFIG_PROC_FS */
1129 * may_umount_tree - check if a mount tree is busy
1130 * @mnt: root of mount tree
1132 * This is called to check if a tree of mounts has any
1133 * open files, pwds, chroots or sub mounts that are
1136 int may_umount_tree(struct vfsmount
*mnt
)
1138 int actual_refs
= 0;
1139 int minimum_refs
= 0;
1142 /* write lock needed for mnt_get_count */
1143 br_write_lock(vfsmount_lock
);
1144 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1145 actual_refs
+= mnt_get_count(p
);
1148 br_write_unlock(vfsmount_lock
);
1150 if (actual_refs
> minimum_refs
)
1156 EXPORT_SYMBOL(may_umount_tree
);
1159 * may_umount - check if a mount point is busy
1160 * @mnt: root of mount
1162 * This is called to check if a mount point has any
1163 * open files, pwds, chroots or sub mounts. If the
1164 * mount has sub mounts this will return busy
1165 * regardless of whether the sub mounts are busy.
1167 * Doesn't take quota and stuff into account. IOW, in some cases it will
1168 * give false negatives. The main reason why it's here is that we need
1169 * a non-destructive way to look for easily umountable filesystems.
1171 int may_umount(struct vfsmount
*mnt
)
1174 down_read(&namespace_sem
);
1175 br_write_lock(vfsmount_lock
);
1176 if (propagate_mount_busy(mnt
, 2))
1178 br_write_unlock(vfsmount_lock
);
1179 up_read(&namespace_sem
);
1183 EXPORT_SYMBOL(may_umount
);
1185 void release_mounts(struct list_head
*head
)
1187 struct vfsmount
*mnt
;
1188 while (!list_empty(head
)) {
1189 mnt
= list_first_entry(head
, struct vfsmount
, mnt_hash
);
1190 list_del_init(&mnt
->mnt_hash
);
1191 if (mnt_has_parent(mnt
)) {
1192 struct dentry
*dentry
;
1195 br_write_lock(vfsmount_lock
);
1196 dentry
= mnt
->mnt_mountpoint
;
1197 m
= mnt
->mnt_parent
;
1198 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
1199 mnt
->mnt_parent
= mnt
;
1201 br_write_unlock(vfsmount_lock
);
1210 * vfsmount lock must be held for write
1211 * namespace_sem must be held for write
1213 void umount_tree(struct vfsmount
*mnt
, int propagate
, struct list_head
*kill
)
1215 LIST_HEAD(tmp_list
);
1218 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
1219 list_move(&p
->mnt_hash
, &tmp_list
);
1222 propagate_umount(&tmp_list
);
1224 list_for_each_entry(p
, &tmp_list
, mnt_hash
) {
1225 list_del_init(&p
->mnt_expire
);
1226 list_del_init(&p
->mnt_list
);
1227 __touch_mnt_namespace(p
->mnt_ns
);
1229 __mnt_make_shortterm(p
);
1230 list_del_init(&p
->mnt_child
);
1231 if (mnt_has_parent(p
)) {
1232 p
->mnt_parent
->mnt_ghosts
++;
1233 dentry_reset_mounted(p
->mnt_mountpoint
);
1235 change_mnt_propagation(p
, MS_PRIVATE
);
1237 list_splice(&tmp_list
, kill
);
1240 static void shrink_submounts(struct vfsmount
*mnt
, struct list_head
*umounts
);
1242 static int do_umount(struct vfsmount
*mnt
, int flags
)
1244 struct super_block
*sb
= mnt
->mnt_sb
;
1246 LIST_HEAD(umount_list
);
1248 retval
= security_sb_umount(mnt
, flags
);
1253 * Allow userspace to request a mountpoint be expired rather than
1254 * unmounting unconditionally. Unmount only happens if:
1255 * (1) the mark is already set (the mark is cleared by mntput())
1256 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1258 if (flags
& MNT_EXPIRE
) {
1259 if (mnt
== current
->fs
->root
.mnt
||
1260 flags
& (MNT_FORCE
| MNT_DETACH
))
1264 * probably don't strictly need the lock here if we examined
1265 * all race cases, but it's a slowpath.
1267 br_write_lock(vfsmount_lock
);
1268 if (mnt_get_count(mnt
) != 2) {
1269 br_write_unlock(vfsmount_lock
);
1272 br_write_unlock(vfsmount_lock
);
1274 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1279 * If we may have to abort operations to get out of this
1280 * mount, and they will themselves hold resources we must
1281 * allow the fs to do things. In the Unix tradition of
1282 * 'Gee thats tricky lets do it in userspace' the umount_begin
1283 * might fail to complete on the first run through as other tasks
1284 * must return, and the like. Thats for the mount program to worry
1285 * about for the moment.
1288 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1289 sb
->s_op
->umount_begin(sb
);
1293 * No sense to grab the lock for this test, but test itself looks
1294 * somewhat bogus. Suggestions for better replacement?
1295 * Ho-hum... In principle, we might treat that as umount + switch
1296 * to rootfs. GC would eventually take care of the old vfsmount.
1297 * Actually it makes sense, especially if rootfs would contain a
1298 * /reboot - static binary that would close all descriptors and
1299 * call reboot(9). Then init(8) could umount root and exec /reboot.
1301 if (mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1303 * Special case for "unmounting" root ...
1304 * we just try to remount it readonly.
1306 down_write(&sb
->s_umount
);
1307 if (!(sb
->s_flags
& MS_RDONLY
))
1308 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
1309 up_write(&sb
->s_umount
);
1313 down_write(&namespace_sem
);
1314 br_write_lock(vfsmount_lock
);
1317 if (!(flags
& MNT_DETACH
))
1318 shrink_submounts(mnt
, &umount_list
);
1321 if (flags
& MNT_DETACH
|| !propagate_mount_busy(mnt
, 2)) {
1322 if (!list_empty(&mnt
->mnt_list
))
1323 umount_tree(mnt
, 1, &umount_list
);
1326 br_write_unlock(vfsmount_lock
);
1327 up_write(&namespace_sem
);
1328 release_mounts(&umount_list
);
1333 * Now umount can handle mount points as well as block devices.
1334 * This is important for filesystems which use unnamed block devices.
1336 * We now support a flag for forced unmount like the other 'big iron'
1337 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1340 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1344 int lookup_flags
= 0;
1346 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1349 if (!(flags
& UMOUNT_NOFOLLOW
))
1350 lookup_flags
|= LOOKUP_FOLLOW
;
1352 retval
= user_path_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1356 if (path
.dentry
!= path
.mnt
->mnt_root
)
1358 if (!check_mnt(path
.mnt
))
1362 if (!capable(CAP_SYS_ADMIN
))
1365 retval
= do_umount(path
.mnt
, flags
);
1367 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1369 mntput_no_expire(path
.mnt
);
1374 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1377 * The 2.0 compatible umount. No flags.
1379 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1381 return sys_umount(name
, 0);
1386 static int mount_is_safe(struct path
*path
)
1388 if (capable(CAP_SYS_ADMIN
))
1392 if (S_ISLNK(path
->dentry
->d_inode
->i_mode
))
1394 if (path
->dentry
->d_inode
->i_mode
& S_ISVTX
) {
1395 if (current_uid() != path
->dentry
->d_inode
->i_uid
)
1398 if (inode_permission(path
->dentry
->d_inode
, MAY_WRITE
))
1404 struct vfsmount
*copy_tree(struct vfsmount
*mnt
, struct dentry
*dentry
,
1407 struct vfsmount
*res
, *p
, *q
, *r
, *s
;
1410 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(mnt
))
1413 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1416 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1419 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1420 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1423 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1424 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(s
)) {
1425 s
= skip_mnt_tree(s
);
1428 while (p
!= s
->mnt_parent
) {
1434 path
.dentry
= p
->mnt_mountpoint
;
1435 q
= clone_mnt(p
, p
->mnt_root
, flag
);
1438 br_write_lock(vfsmount_lock
);
1439 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1440 attach_mnt(q
, &path
);
1441 br_write_unlock(vfsmount_lock
);
1447 LIST_HEAD(umount_list
);
1448 br_write_lock(vfsmount_lock
);
1449 umount_tree(res
, 0, &umount_list
);
1450 br_write_unlock(vfsmount_lock
);
1451 release_mounts(&umount_list
);
1456 struct vfsmount
*collect_mounts(struct path
*path
)
1458 struct vfsmount
*tree
;
1459 down_write(&namespace_sem
);
1460 tree
= copy_tree(path
->mnt
, path
->dentry
, CL_COPY_ALL
| CL_PRIVATE
);
1461 up_write(&namespace_sem
);
1465 void drop_collected_mounts(struct vfsmount
*mnt
)
1467 LIST_HEAD(umount_list
);
1468 down_write(&namespace_sem
);
1469 br_write_lock(vfsmount_lock
);
1470 umount_tree(mnt
, 0, &umount_list
);
1471 br_write_unlock(vfsmount_lock
);
1472 up_write(&namespace_sem
);
1473 release_mounts(&umount_list
);
1476 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1477 struct vfsmount
*root
)
1479 struct vfsmount
*mnt
;
1480 int res
= f(root
, arg
);
1483 list_for_each_entry(mnt
, &root
->mnt_list
, mnt_list
) {
1491 static void cleanup_group_ids(struct vfsmount
*mnt
, struct vfsmount
*end
)
1495 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
1496 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
1497 mnt_release_group_id(p
);
1501 static int invent_group_ids(struct vfsmount
*mnt
, bool recurse
)
1505 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
1506 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
1507 int err
= mnt_alloc_group_id(p
);
1509 cleanup_group_ids(mnt
, p
);
1519 * @source_mnt : mount tree to be attached
1520 * @nd : place the mount tree @source_mnt is attached
1521 * @parent_nd : if non-null, detach the source_mnt from its parent and
1522 * store the parent mount and mountpoint dentry.
1523 * (done when source_mnt is moved)
1525 * NOTE: in the table below explains the semantics when a source mount
1526 * of a given type is attached to a destination mount of a given type.
1527 * ---------------------------------------------------------------------------
1528 * | BIND MOUNT OPERATION |
1529 * |**************************************************************************
1530 * | source-->| shared | private | slave | unbindable |
1534 * |**************************************************************************
1535 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1537 * |non-shared| shared (+) | private | slave (*) | invalid |
1538 * ***************************************************************************
1539 * A bind operation clones the source mount and mounts the clone on the
1540 * destination mount.
1542 * (++) the cloned mount is propagated to all the mounts in the propagation
1543 * tree of the destination mount and the cloned mount is added to
1544 * the peer group of the source mount.
1545 * (+) the cloned mount is created under the destination mount and is marked
1546 * as shared. The cloned mount is added to the peer group of the source
1548 * (+++) the mount is propagated to all the mounts in the propagation tree
1549 * of the destination mount and the cloned mount is made slave
1550 * of the same master as that of the source mount. The cloned mount
1551 * is marked as 'shared and slave'.
1552 * (*) the cloned mount is made a slave of the same master as that of the
1555 * ---------------------------------------------------------------------------
1556 * | MOVE MOUNT OPERATION |
1557 * |**************************************************************************
1558 * | source-->| shared | private | slave | unbindable |
1562 * |**************************************************************************
1563 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1565 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1566 * ***************************************************************************
1568 * (+) the mount is moved to the destination. And is then propagated to
1569 * all the mounts in the propagation tree of the destination mount.
1570 * (+*) the mount is moved to the destination.
1571 * (+++) the mount is moved to the destination and is then propagated to
1572 * all the mounts belonging to the destination mount's propagation tree.
1573 * the mount is marked as 'shared and slave'.
1574 * (*) the mount continues to be a slave at the new location.
1576 * if the source mount is a tree, the operations explained above is
1577 * applied to each mount in the tree.
1578 * Must be called without spinlocks held, since this function can sleep
1581 static int attach_recursive_mnt(struct vfsmount
*source_mnt
,
1582 struct path
*path
, struct path
*parent_path
)
1584 LIST_HEAD(tree_list
);
1585 struct vfsmount
*dest_mnt
= path
->mnt
;
1586 struct dentry
*dest_dentry
= path
->dentry
;
1587 struct vfsmount
*child
, *p
;
1590 if (IS_MNT_SHARED(dest_mnt
)) {
1591 err
= invent_group_ids(source_mnt
, true);
1595 err
= propagate_mnt(dest_mnt
, dest_dentry
, source_mnt
, &tree_list
);
1597 goto out_cleanup_ids
;
1599 br_write_lock(vfsmount_lock
);
1601 if (IS_MNT_SHARED(dest_mnt
)) {
1602 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
1606 detach_mnt(source_mnt
, parent_path
);
1607 attach_mnt(source_mnt
, path
);
1608 touch_mnt_namespace(parent_path
->mnt
->mnt_ns
);
1610 mnt_set_mountpoint(dest_mnt
, dest_dentry
, source_mnt
);
1611 commit_tree(source_mnt
);
1614 list_for_each_entry_safe(child
, p
, &tree_list
, mnt_hash
) {
1615 list_del_init(&child
->mnt_hash
);
1618 br_write_unlock(vfsmount_lock
);
1623 if (IS_MNT_SHARED(dest_mnt
))
1624 cleanup_group_ids(source_mnt
, NULL
);
1629 static int lock_mount(struct path
*path
)
1631 struct vfsmount
*mnt
;
1633 mutex_lock(&path
->dentry
->d_inode
->i_mutex
);
1634 if (unlikely(cant_mount(path
->dentry
))) {
1635 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1638 down_write(&namespace_sem
);
1639 mnt
= lookup_mnt(path
);
1642 up_write(&namespace_sem
);
1643 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1646 path
->dentry
= dget(mnt
->mnt_root
);
1650 static void unlock_mount(struct path
*path
)
1652 up_write(&namespace_sem
);
1653 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1656 static int graft_tree(struct vfsmount
*mnt
, struct path
*path
)
1658 if (mnt
->mnt_sb
->s_flags
& MS_NOUSER
)
1661 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
1662 S_ISDIR(mnt
->mnt_root
->d_inode
->i_mode
))
1665 if (d_unlinked(path
->dentry
))
1668 return attach_recursive_mnt(mnt
, path
, NULL
);
1672 * Sanity check the flags to change_mnt_propagation.
1675 static int flags_to_propagation_type(int flags
)
1677 int type
= flags
& ~(MS_REC
| MS_SILENT
);
1679 /* Fail if any non-propagation flags are set */
1680 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
1682 /* Only one propagation flag should be set */
1683 if (!is_power_of_2(type
))
1689 * recursively change the type of the mountpoint.
1691 static int do_change_type(struct path
*path
, int flag
)
1693 struct vfsmount
*m
, *mnt
= path
->mnt
;
1694 int recurse
= flag
& MS_REC
;
1698 if (!capable(CAP_SYS_ADMIN
))
1701 if (path
->dentry
!= path
->mnt
->mnt_root
)
1704 type
= flags_to_propagation_type(flag
);
1708 down_write(&namespace_sem
);
1709 if (type
== MS_SHARED
) {
1710 err
= invent_group_ids(mnt
, recurse
);
1715 br_write_lock(vfsmount_lock
);
1716 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
1717 change_mnt_propagation(m
, type
);
1718 br_write_unlock(vfsmount_lock
);
1721 up_write(&namespace_sem
);
1726 * do loopback mount.
1728 static int do_loopback(struct path
*path
, char *old_name
,
1731 LIST_HEAD(umount_list
);
1732 struct path old_path
;
1733 struct vfsmount
*mnt
= NULL
;
1734 int err
= mount_is_safe(path
);
1737 if (!old_name
|| !*old_name
)
1739 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
1743 err
= lock_mount(path
);
1748 if (IS_MNT_UNBINDABLE(old_path
.mnt
))
1751 if (!check_mnt(path
->mnt
) || !check_mnt(old_path
.mnt
))
1756 mnt
= copy_tree(old_path
.mnt
, old_path
.dentry
, 0);
1758 mnt
= clone_mnt(old_path
.mnt
, old_path
.dentry
, 0);
1763 err
= graft_tree(mnt
, path
);
1765 br_write_lock(vfsmount_lock
);
1766 umount_tree(mnt
, 0, &umount_list
);
1767 br_write_unlock(vfsmount_lock
);
1771 release_mounts(&umount_list
);
1773 path_put(&old_path
);
1777 static int change_mount_flags(struct vfsmount
*mnt
, int ms_flags
)
1780 int readonly_request
= 0;
1782 if (ms_flags
& MS_RDONLY
)
1783 readonly_request
= 1;
1784 if (readonly_request
== __mnt_is_readonly(mnt
))
1787 if (readonly_request
)
1788 error
= mnt_make_readonly(mnt
);
1790 __mnt_unmake_readonly(mnt
);
1795 * change filesystem flags. dir should be a physical root of filesystem.
1796 * If you've mounted a non-root directory somewhere and want to do remount
1797 * on it - tough luck.
1799 static int do_remount(struct path
*path
, int flags
, int mnt_flags
,
1803 struct super_block
*sb
= path
->mnt
->mnt_sb
;
1805 if (!capable(CAP_SYS_ADMIN
))
1808 if (!check_mnt(path
->mnt
))
1811 if (path
->dentry
!= path
->mnt
->mnt_root
)
1814 err
= security_sb_remount(sb
, data
);
1818 down_write(&sb
->s_umount
);
1819 if (flags
& MS_BIND
)
1820 err
= change_mount_flags(path
->mnt
, flags
);
1822 err
= do_remount_sb(sb
, flags
, data
, 0);
1824 br_write_lock(vfsmount_lock
);
1825 mnt_flags
|= path
->mnt
->mnt_flags
& MNT_PROPAGATION_MASK
;
1826 path
->mnt
->mnt_flags
= mnt_flags
;
1827 br_write_unlock(vfsmount_lock
);
1829 up_write(&sb
->s_umount
);
1831 br_write_lock(vfsmount_lock
);
1832 touch_mnt_namespace(path
->mnt
->mnt_ns
);
1833 br_write_unlock(vfsmount_lock
);
1838 static inline int tree_contains_unbindable(struct vfsmount
*mnt
)
1841 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1842 if (IS_MNT_UNBINDABLE(p
))
1848 static int do_move_mount(struct path
*path
, char *old_name
)
1850 struct path old_path
, parent_path
;
1853 if (!capable(CAP_SYS_ADMIN
))
1855 if (!old_name
|| !*old_name
)
1857 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
1861 err
= lock_mount(path
);
1866 if (!check_mnt(path
->mnt
) || !check_mnt(old_path
.mnt
))
1869 if (d_unlinked(path
->dentry
))
1873 if (old_path
.dentry
!= old_path
.mnt
->mnt_root
)
1876 if (!mnt_has_parent(old_path
.mnt
))
1879 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
1880 S_ISDIR(old_path
.dentry
->d_inode
->i_mode
))
1883 * Don't move a mount residing in a shared parent.
1885 if (IS_MNT_SHARED(old_path
.mnt
->mnt_parent
))
1888 * Don't move a mount tree containing unbindable mounts to a destination
1889 * mount which is shared.
1891 if (IS_MNT_SHARED(path
->mnt
) &&
1892 tree_contains_unbindable(old_path
.mnt
))
1895 for (p
= path
->mnt
; mnt_has_parent(p
); p
= p
->mnt_parent
)
1896 if (p
== old_path
.mnt
)
1899 err
= attach_recursive_mnt(old_path
.mnt
, path
, &parent_path
);
1903 /* if the mount is moved, it should no longer be expire
1905 list_del_init(&old_path
.mnt
->mnt_expire
);
1910 path_put(&parent_path
);
1911 path_put(&old_path
);
1915 static struct vfsmount
*fs_set_subtype(struct vfsmount
*mnt
, const char *fstype
)
1918 const char *subtype
= strchr(fstype
, '.');
1927 mnt
->mnt_sb
->s_subtype
= kstrdup(subtype
, GFP_KERNEL
);
1929 if (!mnt
->mnt_sb
->s_subtype
)
1935 return ERR_PTR(err
);
1938 static struct vfsmount
*
1939 do_kern_mount(const char *fstype
, int flags
, const char *name
, void *data
)
1941 struct file_system_type
*type
= get_fs_type(fstype
);
1942 struct vfsmount
*mnt
;
1944 return ERR_PTR(-ENODEV
);
1945 mnt
= vfs_kern_mount(type
, flags
, name
, data
);
1946 if (!IS_ERR(mnt
) && (type
->fs_flags
& FS_HAS_SUBTYPE
) &&
1947 !mnt
->mnt_sb
->s_subtype
)
1948 mnt
= fs_set_subtype(mnt
, fstype
);
1949 put_filesystem(type
);
1954 * add a mount into a namespace's mount tree
1956 static int do_add_mount(struct vfsmount
*newmnt
, struct path
*path
, int mnt_flags
)
1960 mnt_flags
&= ~(MNT_SHARED
| MNT_WRITE_HOLD
| MNT_INTERNAL
);
1962 err
= lock_mount(path
);
1967 if (!(mnt_flags
& MNT_SHRINKABLE
) && !check_mnt(path
->mnt
))
1970 /* Refuse the same filesystem on the same mount point */
1972 if (path
->mnt
->mnt_sb
== newmnt
->mnt_sb
&&
1973 path
->mnt
->mnt_root
== path
->dentry
)
1977 if (S_ISLNK(newmnt
->mnt_root
->d_inode
->i_mode
))
1980 newmnt
->mnt_flags
= mnt_flags
;
1981 err
= graft_tree(newmnt
, path
);
1989 * create a new mount for userspace and request it to be added into the
1992 static int do_new_mount(struct path
*path
, char *type
, int flags
,
1993 int mnt_flags
, char *name
, void *data
)
1995 struct vfsmount
*mnt
;
2001 /* we need capabilities... */
2002 if (!capable(CAP_SYS_ADMIN
))
2005 mnt
= do_kern_mount(type
, flags
, name
, data
);
2007 return PTR_ERR(mnt
);
2009 err
= do_add_mount(mnt
, path
, mnt_flags
);
2015 int finish_automount(struct vfsmount
*m
, struct path
*path
)
2018 /* The new mount record should have at least 2 refs to prevent it being
2019 * expired before we get a chance to add it
2021 BUG_ON(mnt_get_count(m
) < 2);
2023 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
2024 m
->mnt_root
== path
->dentry
) {
2029 err
= do_add_mount(m
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
2033 /* remove m from any expiration list it may be on */
2034 if (!list_empty(&m
->mnt_expire
)) {
2035 down_write(&namespace_sem
);
2036 br_write_lock(vfsmount_lock
);
2037 list_del_init(&m
->mnt_expire
);
2038 br_write_unlock(vfsmount_lock
);
2039 up_write(&namespace_sem
);
2047 * mnt_set_expiry - Put a mount on an expiration list
2048 * @mnt: The mount to list.
2049 * @expiry_list: The list to add the mount to.
2051 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
2053 down_write(&namespace_sem
);
2054 br_write_lock(vfsmount_lock
);
2056 list_add_tail(&mnt
->mnt_expire
, expiry_list
);
2058 br_write_unlock(vfsmount_lock
);
2059 up_write(&namespace_sem
);
2061 EXPORT_SYMBOL(mnt_set_expiry
);
2064 * process a list of expirable mountpoints with the intent of discarding any
2065 * mountpoints that aren't in use and haven't been touched since last we came
2068 void mark_mounts_for_expiry(struct list_head
*mounts
)
2070 struct vfsmount
*mnt
, *next
;
2071 LIST_HEAD(graveyard
);
2074 if (list_empty(mounts
))
2077 down_write(&namespace_sem
);
2078 br_write_lock(vfsmount_lock
);
2080 /* extract from the expiration list every vfsmount that matches the
2081 * following criteria:
2082 * - only referenced by its parent vfsmount
2083 * - still marked for expiry (marked on the last call here; marks are
2084 * cleared by mntput())
2086 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
2087 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
2088 propagate_mount_busy(mnt
, 1))
2090 list_move(&mnt
->mnt_expire
, &graveyard
);
2092 while (!list_empty(&graveyard
)) {
2093 mnt
= list_first_entry(&graveyard
, struct vfsmount
, mnt_expire
);
2094 touch_mnt_namespace(mnt
->mnt_ns
);
2095 umount_tree(mnt
, 1, &umounts
);
2097 br_write_unlock(vfsmount_lock
);
2098 up_write(&namespace_sem
);
2100 release_mounts(&umounts
);
2103 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
2106 * Ripoff of 'select_parent()'
2108 * search the list of submounts for a given mountpoint, and move any
2109 * shrinkable submounts to the 'graveyard' list.
2111 static int select_submounts(struct vfsmount
*parent
, struct list_head
*graveyard
)
2113 struct vfsmount
*this_parent
= parent
;
2114 struct list_head
*next
;
2118 next
= this_parent
->mnt_mounts
.next
;
2120 while (next
!= &this_parent
->mnt_mounts
) {
2121 struct list_head
*tmp
= next
;
2122 struct vfsmount
*mnt
= list_entry(tmp
, struct vfsmount
, mnt_child
);
2125 if (!(mnt
->mnt_flags
& MNT_SHRINKABLE
))
2128 * Descend a level if the d_mounts list is non-empty.
2130 if (!list_empty(&mnt
->mnt_mounts
)) {
2135 if (!propagate_mount_busy(mnt
, 1)) {
2136 list_move_tail(&mnt
->mnt_expire
, graveyard
);
2141 * All done at this level ... ascend and resume the search
2143 if (this_parent
!= parent
) {
2144 next
= this_parent
->mnt_child
.next
;
2145 this_parent
= this_parent
->mnt_parent
;
2152 * process a list of expirable mountpoints with the intent of discarding any
2153 * submounts of a specific parent mountpoint
2155 * vfsmount_lock must be held for write
2157 static void shrink_submounts(struct vfsmount
*mnt
, struct list_head
*umounts
)
2159 LIST_HEAD(graveyard
);
2162 /* extract submounts of 'mountpoint' from the expiration list */
2163 while (select_submounts(mnt
, &graveyard
)) {
2164 while (!list_empty(&graveyard
)) {
2165 m
= list_first_entry(&graveyard
, struct vfsmount
,
2167 touch_mnt_namespace(m
->mnt_ns
);
2168 umount_tree(m
, 1, umounts
);
2174 * Some copy_from_user() implementations do not return the exact number of
2175 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2176 * Note that this function differs from copy_from_user() in that it will oops
2177 * on bad values of `to', rather than returning a short copy.
2179 static long exact_copy_from_user(void *to
, const void __user
* from
,
2183 const char __user
*f
= from
;
2186 if (!access_ok(VERIFY_READ
, from
, n
))
2190 if (__get_user(c
, f
)) {
2201 int copy_mount_options(const void __user
* data
, unsigned long *where
)
2211 if (!(page
= __get_free_page(GFP_KERNEL
)))
2214 /* We only care that *some* data at the address the user
2215 * gave us is valid. Just in case, we'll zero
2216 * the remainder of the page.
2218 /* copy_from_user cannot cross TASK_SIZE ! */
2219 size
= TASK_SIZE
- (unsigned long)data
;
2220 if (size
> PAGE_SIZE
)
2223 i
= size
- exact_copy_from_user((void *)page
, data
, size
);
2229 memset((char *)page
+ i
, 0, PAGE_SIZE
- i
);
2234 int copy_mount_string(const void __user
*data
, char **where
)
2243 tmp
= strndup_user(data
, PAGE_SIZE
);
2245 return PTR_ERR(tmp
);
2252 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2253 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2255 * data is a (void *) that can point to any structure up to
2256 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2257 * information (or be NULL).
2259 * Pre-0.97 versions of mount() didn't have a flags word.
2260 * When the flags word was introduced its top half was required
2261 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2262 * Therefore, if this magic number is present, it carries no information
2263 * and must be discarded.
2265 long do_mount(char *dev_name
, char *dir_name
, char *type_page
,
2266 unsigned long flags
, void *data_page
)
2273 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
2274 flags
&= ~MS_MGC_MSK
;
2276 /* Basic sanity checks */
2278 if (!dir_name
|| !*dir_name
|| !memchr(dir_name
, 0, PAGE_SIZE
))
2282 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
2284 /* ... and get the mountpoint */
2285 retval
= kern_path(dir_name
, LOOKUP_FOLLOW
, &path
);
2289 retval
= security_sb_mount(dev_name
, &path
,
2290 type_page
, flags
, data_page
);
2294 /* Default to relatime unless overriden */
2295 if (!(flags
& MS_NOATIME
))
2296 mnt_flags
|= MNT_RELATIME
;
2298 /* Separate the per-mountpoint flags */
2299 if (flags
& MS_NOSUID
)
2300 mnt_flags
|= MNT_NOSUID
;
2301 if (flags
& MS_NODEV
)
2302 mnt_flags
|= MNT_NODEV
;
2303 if (flags
& MS_NOEXEC
)
2304 mnt_flags
|= MNT_NOEXEC
;
2305 if (flags
& MS_NOATIME
)
2306 mnt_flags
|= MNT_NOATIME
;
2307 if (flags
& MS_NODIRATIME
)
2308 mnt_flags
|= MNT_NODIRATIME
;
2309 if (flags
& MS_STRICTATIME
)
2310 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
2311 if (flags
& MS_RDONLY
)
2312 mnt_flags
|= MNT_READONLY
;
2314 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
| MS_BORN
|
2315 MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
| MS_KERNMOUNT
|
2318 if (flags
& MS_REMOUNT
)
2319 retval
= do_remount(&path
, flags
& ~MS_REMOUNT
, mnt_flags
,
2321 else if (flags
& MS_BIND
)
2322 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
2323 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2324 retval
= do_change_type(&path
, flags
);
2325 else if (flags
& MS_MOVE
)
2326 retval
= do_move_mount(&path
, dev_name
);
2328 retval
= do_new_mount(&path
, type_page
, flags
, mnt_flags
,
2329 dev_name
, data_page
);
2335 static struct mnt_namespace
*alloc_mnt_ns(void)
2337 struct mnt_namespace
*new_ns
;
2339 new_ns
= kmalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
2341 return ERR_PTR(-ENOMEM
);
2342 atomic_set(&new_ns
->count
, 1);
2343 new_ns
->root
= NULL
;
2344 INIT_LIST_HEAD(&new_ns
->list
);
2345 init_waitqueue_head(&new_ns
->poll
);
2350 void mnt_make_longterm(struct vfsmount
*mnt
)
2352 __mnt_make_longterm(mnt
);
2355 void mnt_make_shortterm(struct vfsmount
*mnt
)
2358 if (atomic_add_unless(&mnt
->mnt_longterm
, -1, 1))
2360 br_write_lock(vfsmount_lock
);
2361 atomic_dec(&mnt
->mnt_longterm
);
2362 br_write_unlock(vfsmount_lock
);
2367 * Allocate a new namespace structure and populate it with contents
2368 * copied from the namespace of the passed in task structure.
2370 static struct mnt_namespace
*dup_mnt_ns(struct mnt_namespace
*mnt_ns
,
2371 struct fs_struct
*fs
)
2373 struct mnt_namespace
*new_ns
;
2374 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
2375 struct vfsmount
*p
, *q
;
2377 new_ns
= alloc_mnt_ns();
2381 down_write(&namespace_sem
);
2382 /* First pass: copy the tree topology */
2383 new_ns
->root
= copy_tree(mnt_ns
->root
, mnt_ns
->root
->mnt_root
,
2384 CL_COPY_ALL
| CL_EXPIRE
);
2385 if (!new_ns
->root
) {
2386 up_write(&namespace_sem
);
2388 return ERR_PTR(-ENOMEM
);
2390 br_write_lock(vfsmount_lock
);
2391 list_add_tail(&new_ns
->list
, &new_ns
->root
->mnt_list
);
2392 br_write_unlock(vfsmount_lock
);
2395 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2396 * as belonging to new namespace. We have already acquired a private
2397 * fs_struct, so tsk->fs->lock is not needed.
2403 __mnt_make_longterm(q
);
2405 if (p
== fs
->root
.mnt
) {
2406 fs
->root
.mnt
= mntget(q
);
2407 __mnt_make_longterm(q
);
2408 mnt_make_shortterm(p
);
2411 if (p
== fs
->pwd
.mnt
) {
2412 fs
->pwd
.mnt
= mntget(q
);
2413 __mnt_make_longterm(q
);
2414 mnt_make_shortterm(p
);
2418 p
= next_mnt(p
, mnt_ns
->root
);
2419 q
= next_mnt(q
, new_ns
->root
);
2421 up_write(&namespace_sem
);
2431 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
2432 struct fs_struct
*new_fs
)
2434 struct mnt_namespace
*new_ns
;
2439 if (!(flags
& CLONE_NEWNS
))
2442 new_ns
= dup_mnt_ns(ns
, new_fs
);
2449 * create_mnt_ns - creates a private namespace and adds a root filesystem
2450 * @mnt: pointer to the new root filesystem mountpoint
2452 static struct mnt_namespace
*create_mnt_ns(struct vfsmount
*mnt
)
2454 struct mnt_namespace
*new_ns
;
2456 new_ns
= alloc_mnt_ns();
2457 if (!IS_ERR(new_ns
)) {
2458 mnt
->mnt_ns
= new_ns
;
2459 __mnt_make_longterm(mnt
);
2461 list_add(&new_ns
->list
, &new_ns
->root
->mnt_list
);
2468 struct dentry
*mount_subtree(struct vfsmount
*mnt
, const char *name
)
2470 struct mnt_namespace
*ns
;
2471 struct super_block
*s
;
2475 ns
= create_mnt_ns(mnt
);
2477 return ERR_CAST(ns
);
2479 err
= vfs_path_lookup(mnt
->mnt_root
, mnt
,
2480 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
2485 return ERR_PTR(err
);
2487 /* trade a vfsmount reference for active sb one */
2488 s
= path
.mnt
->mnt_sb
;
2489 atomic_inc(&s
->s_active
);
2491 /* lock the sucker */
2492 down_write(&s
->s_umount
);
2493 /* ... and return the root of (sub)tree on it */
2496 EXPORT_SYMBOL(mount_subtree
);
2498 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
2499 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
2505 unsigned long data_page
;
2507 ret
= copy_mount_string(type
, &kernel_type
);
2511 kernel_dir
= getname(dir_name
);
2512 if (IS_ERR(kernel_dir
)) {
2513 ret
= PTR_ERR(kernel_dir
);
2517 ret
= copy_mount_string(dev_name
, &kernel_dev
);
2521 ret
= copy_mount_options(data
, &data_page
);
2525 ret
= do_mount(kernel_dev
, kernel_dir
, kernel_type
, flags
,
2526 (void *) data_page
);
2528 free_page(data_page
);
2532 putname(kernel_dir
);
2540 * Return true if path is reachable from root
2542 * namespace_sem or vfsmount_lock is held
2544 bool is_path_reachable(struct vfsmount
*mnt
, struct dentry
*dentry
,
2545 const struct path
*root
)
2547 while (mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
2548 dentry
= mnt
->mnt_mountpoint
;
2549 mnt
= mnt
->mnt_parent
;
2551 return mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
2554 int path_is_under(struct path
*path1
, struct path
*path2
)
2557 br_read_lock(vfsmount_lock
);
2558 res
= is_path_reachable(path1
->mnt
, path1
->dentry
, path2
);
2559 br_read_unlock(vfsmount_lock
);
2562 EXPORT_SYMBOL(path_is_under
);
2565 * pivot_root Semantics:
2566 * Moves the root file system of the current process to the directory put_old,
2567 * makes new_root as the new root file system of the current process, and sets
2568 * root/cwd of all processes which had them on the current root to new_root.
2571 * The new_root and put_old must be directories, and must not be on the
2572 * same file system as the current process root. The put_old must be
2573 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2574 * pointed to by put_old must yield the same directory as new_root. No other
2575 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2577 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2578 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2579 * in this situation.
2582 * - we don't move root/cwd if they are not at the root (reason: if something
2583 * cared enough to change them, it's probably wrong to force them elsewhere)
2584 * - it's okay to pick a root that isn't the root of a file system, e.g.
2585 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2586 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2589 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
2590 const char __user
*, put_old
)
2592 struct path
new, old
, parent_path
, root_parent
, root
;
2595 if (!capable(CAP_SYS_ADMIN
))
2598 error
= user_path_dir(new_root
, &new);
2602 error
= user_path_dir(put_old
, &old
);
2606 error
= security_sb_pivotroot(&old
, &new);
2610 get_fs_root(current
->fs
, &root
);
2611 error
= lock_mount(&old
);
2616 if (IS_MNT_SHARED(old
.mnt
) ||
2617 IS_MNT_SHARED(new.mnt
->mnt_parent
) ||
2618 IS_MNT_SHARED(root
.mnt
->mnt_parent
))
2620 if (!check_mnt(root
.mnt
) || !check_mnt(new.mnt
))
2623 if (d_unlinked(new.dentry
))
2625 if (d_unlinked(old
.dentry
))
2628 if (new.mnt
== root
.mnt
||
2629 old
.mnt
== root
.mnt
)
2630 goto out4
; /* loop, on the same file system */
2632 if (root
.mnt
->mnt_root
!= root
.dentry
)
2633 goto out4
; /* not a mountpoint */
2634 if (!mnt_has_parent(root
.mnt
))
2635 goto out4
; /* not attached */
2636 if (new.mnt
->mnt_root
!= new.dentry
)
2637 goto out4
; /* not a mountpoint */
2638 if (!mnt_has_parent(new.mnt
))
2639 goto out4
; /* not attached */
2640 /* make sure we can reach put_old from new_root */
2641 if (!is_path_reachable(old
.mnt
, old
.dentry
, &new))
2643 br_write_lock(vfsmount_lock
);
2644 detach_mnt(new.mnt
, &parent_path
);
2645 detach_mnt(root
.mnt
, &root_parent
);
2646 /* mount old root on put_old */
2647 attach_mnt(root
.mnt
, &old
);
2648 /* mount new_root on / */
2649 attach_mnt(new.mnt
, &root_parent
);
2650 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
2651 br_write_unlock(vfsmount_lock
);
2652 chroot_fs_refs(&root
, &new);
2657 path_put(&root_parent
);
2658 path_put(&parent_path
);
2670 static void __init
init_mount_tree(void)
2672 struct vfsmount
*mnt
;
2673 struct mnt_namespace
*ns
;
2676 mnt
= do_kern_mount("rootfs", 0, "rootfs", NULL
);
2678 panic("Can't create rootfs");
2680 ns
= create_mnt_ns(mnt
);
2682 panic("Can't allocate initial namespace");
2684 init_task
.nsproxy
->mnt_ns
= ns
;
2687 root
.mnt
= ns
->root
;
2688 root
.dentry
= ns
->root
->mnt_root
;
2690 set_fs_pwd(current
->fs
, &root
);
2691 set_fs_root(current
->fs
, &root
);
2694 void __init
mnt_init(void)
2699 init_rwsem(&namespace_sem
);
2701 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct vfsmount
),
2702 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
2704 mount_hashtable
= (struct list_head
*)__get_free_page(GFP_ATOMIC
);
2706 if (!mount_hashtable
)
2707 panic("Failed to allocate mount hash table\n");
2709 printk(KERN_INFO
"Mount-cache hash table entries: %lu\n", HASH_SIZE
);
2711 for (u
= 0; u
< HASH_SIZE
; u
++)
2712 INIT_LIST_HEAD(&mount_hashtable
[u
]);
2714 br_lock_init(vfsmount_lock
);
2718 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
2720 fs_kobj
= kobject_create_and_add("fs", NULL
);
2722 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
2727 void put_mnt_ns(struct mnt_namespace
*ns
)
2729 LIST_HEAD(umount_list
);
2731 if (!atomic_dec_and_test(&ns
->count
))
2733 down_write(&namespace_sem
);
2734 br_write_lock(vfsmount_lock
);
2735 umount_tree(ns
->root
, 0, &umount_list
);
2736 br_write_unlock(vfsmount_lock
);
2737 up_write(&namespace_sem
);
2738 release_mounts(&umount_list
);
2742 struct vfsmount
*kern_mount_data(struct file_system_type
*type
, void *data
)
2744 struct vfsmount
*mnt
;
2745 mnt
= vfs_kern_mount(type
, MS_KERNMOUNT
, type
->name
, data
);
2748 * it is a longterm mount, don't release mnt until
2749 * we unmount before file sys is unregistered
2751 mnt_make_longterm(mnt
);
2755 EXPORT_SYMBOL_GPL(kern_mount_data
);
2757 void kern_unmount(struct vfsmount
*mnt
)
2759 /* release long term mount so mount point can be released */
2760 if (!IS_ERR_OR_NULL(mnt
)) {
2761 mnt_make_shortterm(mnt
);
2765 EXPORT_SYMBOL(kern_unmount
);
2767 bool our_mnt(struct vfsmount
*mnt
)
2769 return check_mnt(mnt
);