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_id
);
90 mnt_id_start
= mnt
->mnt_id
+ 1;
91 spin_unlock(&mnt_id_lock
);
98 static void mnt_free_id(struct mount
*mnt
)
100 int id
= mnt
->mnt_id
;
101 spin_lock(&mnt_id_lock
);
102 ida_remove(&mnt_id_ida
, id
);
103 if (mnt_id_start
> id
)
105 spin_unlock(&mnt_id_lock
);
109 * Allocate a new peer group ID
111 * mnt_group_ida is protected by namespace_sem
113 static int mnt_alloc_group_id(struct mount
*mnt
)
117 if (!ida_pre_get(&mnt_group_ida
, GFP_KERNEL
))
120 res
= ida_get_new_above(&mnt_group_ida
,
124 mnt_group_start
= 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_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 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
*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 mount
*mnt
)
258 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
264 static inline void mnt_dec_writers(struct mount
*mnt
)
267 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
273 static unsigned int mnt_get_writers(struct mount
*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 * @m: 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
*m
)
309 struct mount
*mnt
= real_mount(m
);
313 mnt_inc_writers(mnt
);
315 * The store to mnt_inc_writers must be visible before we pass
316 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
317 * incremented count after it has set MNT_WRITE_HOLD.
320 while (mnt
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
323 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
324 * be set to match its requirements. So we must not load that until
325 * MNT_WRITE_HOLD is cleared.
328 if (__mnt_is_readonly(m
)) {
329 mnt_dec_writers(mnt
);
337 EXPORT_SYMBOL_GPL(mnt_want_write
);
340 * mnt_clone_write - get write access to a mount
341 * @mnt: the mount on which to take a write
343 * This is effectively like mnt_want_write, except
344 * it must only be used to take an extra write reference
345 * on a mountpoint that we already know has a write reference
346 * on it. This allows some optimisation.
348 * After finished, mnt_drop_write must be called as usual to
349 * drop the reference.
351 int mnt_clone_write(struct vfsmount
*mnt
)
353 /* superblock may be r/o */
354 if (__mnt_is_readonly(mnt
))
357 mnt_inc_writers(real_mount(mnt
));
361 EXPORT_SYMBOL_GPL(mnt_clone_write
);
364 * mnt_want_write_file - get write access to a file's mount
365 * @file: the file who's mount on which to take a write
367 * This is like mnt_want_write, but it takes a file and can
368 * do some optimisations if the file is open for write already
370 int mnt_want_write_file(struct file
*file
)
372 struct inode
*inode
= file
->f_dentry
->d_inode
;
373 if (!(file
->f_mode
& FMODE_WRITE
) || special_file(inode
->i_mode
))
374 return mnt_want_write(file
->f_path
.mnt
);
376 return mnt_clone_write(file
->f_path
.mnt
);
378 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
381 * mnt_drop_write - give up write access to a mount
382 * @mnt: the mount on which to give up write access
384 * Tells the low-level filesystem that we are done
385 * performing writes to it. Must be matched with
386 * mnt_want_write() call above.
388 void mnt_drop_write(struct vfsmount
*mnt
)
391 mnt_dec_writers(real_mount(mnt
));
394 EXPORT_SYMBOL_GPL(mnt_drop_write
);
396 void mnt_drop_write_file(struct file
*file
)
398 mnt_drop_write(file
->f_path
.mnt
);
400 EXPORT_SYMBOL(mnt_drop_write_file
);
402 static int mnt_make_readonly(struct mount
*mnt
)
406 br_write_lock(vfsmount_lock
);
407 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
409 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
410 * should be visible before we do.
415 * With writers on hold, if this value is zero, then there are
416 * definitely no active writers (although held writers may subsequently
417 * increment the count, they'll have to wait, and decrement it after
418 * seeing MNT_READONLY).
420 * It is OK to have counter incremented on one CPU and decremented on
421 * another: the sum will add up correctly. The danger would be when we
422 * sum up each counter, if we read a counter before it is incremented,
423 * but then read another CPU's count which it has been subsequently
424 * decremented from -- we would see more decrements than we should.
425 * MNT_WRITE_HOLD protects against this scenario, because
426 * mnt_want_write first increments count, then smp_mb, then spins on
427 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
428 * we're counting up here.
430 if (mnt_get_writers(mnt
) > 0)
433 mnt
->mnt
.mnt_flags
|= MNT_READONLY
;
435 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
436 * that become unheld will see MNT_READONLY.
439 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
440 br_write_unlock(vfsmount_lock
);
444 static void __mnt_unmake_readonly(struct mount
*mnt
)
446 br_write_lock(vfsmount_lock
);
447 mnt
->mnt
.mnt_flags
&= ~MNT_READONLY
;
448 br_write_unlock(vfsmount_lock
);
451 static void free_vfsmnt(struct mount
*mnt
)
453 kfree(mnt
->mnt_devname
);
456 free_percpu(mnt
->mnt_pcp
);
458 kmem_cache_free(mnt_cache
, mnt
);
462 * find the first or last mount at @dentry on vfsmount @mnt depending on
463 * @dir. If @dir is set return the first mount else return the last mount.
464 * vfsmount_lock must be held for read or write.
466 struct mount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
,
469 struct list_head
*head
= mount_hashtable
+ hash(mnt
, dentry
);
470 struct list_head
*tmp
= head
;
471 struct mount
*p
, *found
= NULL
;
474 tmp
= dir
? tmp
->next
: tmp
->prev
;
478 p
= list_entry(tmp
, struct mount
, mnt_hash
);
479 if (&p
->mnt_parent
->mnt
== mnt
&& p
->mnt_mountpoint
== dentry
) {
488 * lookup_mnt increments the ref count before returning
489 * the vfsmount struct.
491 struct vfsmount
*lookup_mnt(struct path
*path
)
493 struct mount
*child_mnt
;
495 br_read_lock(vfsmount_lock
);
496 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
, 1);
498 mnt_add_count(child_mnt
, 1);
499 br_read_unlock(vfsmount_lock
);
500 return &child_mnt
->mnt
;
502 br_read_unlock(vfsmount_lock
);
507 static inline int check_mnt(struct mount
*mnt
)
509 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
513 * vfsmount lock must be held for write
515 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
519 wake_up_interruptible(&ns
->poll
);
524 * vfsmount lock must be held for write
526 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
528 if (ns
&& ns
->event
!= event
) {
530 wake_up_interruptible(&ns
->poll
);
535 * Clear dentry's mounted state if it has no remaining mounts.
536 * vfsmount_lock must be held for write.
538 static void dentry_reset_mounted(struct dentry
*dentry
)
542 for (u
= 0; u
< HASH_SIZE
; u
++) {
545 list_for_each_entry(p
, &mount_hashtable
[u
], mnt_hash
) {
546 if (p
->mnt_mountpoint
== dentry
)
550 spin_lock(&dentry
->d_lock
);
551 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
552 spin_unlock(&dentry
->d_lock
);
556 * vfsmount lock must be held for write
558 static void detach_mnt(struct mount
*mnt
, struct path
*old_path
)
560 old_path
->dentry
= mnt
->mnt_mountpoint
;
561 old_path
->mnt
= &mnt
->mnt_parent
->mnt
;
562 mnt
->mnt_parent
= mnt
;
563 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
564 list_del_init(&mnt
->mnt_child
);
565 list_del_init(&mnt
->mnt_hash
);
566 dentry_reset_mounted(old_path
->dentry
);
570 * vfsmount lock must be held for write
572 void mnt_set_mountpoint(struct mount
*mnt
, struct dentry
*dentry
,
573 struct mount
*child_mnt
)
575 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
576 child_mnt
->mnt_mountpoint
= dget(dentry
);
577 child_mnt
->mnt_parent
= mnt
;
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_list
);
622 list_for_each_entry(m
, &head
, mnt_list
) {
624 __mnt_make_longterm(m
);
627 list_splice(&head
, n
->list
.prev
);
629 list_add_tail(&mnt
->mnt_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 mount
*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_devname
);
698 if (flag
& (CL_SLAVE
| CL_PRIVATE
))
699 mnt
->mnt_group_id
= 0; /* not a peer of original */
701 mnt
->mnt_group_id
= old
->mnt_group_id
;
703 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
704 int err
= mnt_alloc_group_id(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
);
720 } else if (!(flag
& CL_PRIVATE
)) {
721 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
722 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
723 if (IS_MNT_SLAVE(old
))
724 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
725 mnt
->mnt_master
= old
->mnt_master
;
727 if (flag
& CL_MAKE_SHARED
)
730 /* stick the duplicate mount on the same expiry list
731 * as the original if that was on one */
732 if (flag
& CL_EXPIRE
) {
733 if (!list_empty(&old
->mnt_expire
))
734 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
744 static inline void mntfree(struct 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_pinned
)) {
791 mnt_add_count(mnt
, mnt
->mnt_pinned
+ 1);
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 struct mount
*m
= real_mount(mnt
);
805 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
806 if (unlikely(m
->mnt_expiry_mark
))
807 m
->mnt_expiry_mark
= 0;
811 EXPORT_SYMBOL(mntput
);
813 struct vfsmount
*mntget(struct vfsmount
*mnt
)
816 mnt_add_count(real_mount(mnt
), 1);
819 EXPORT_SYMBOL(mntget
);
821 void mnt_pin(struct vfsmount
*mnt
)
823 br_write_lock(vfsmount_lock
);
824 real_mount(mnt
)->mnt_pinned
++;
825 br_write_unlock(vfsmount_lock
);
827 EXPORT_SYMBOL(mnt_pin
);
829 void mnt_unpin(struct vfsmount
*m
)
831 struct mount
*mnt
= real_mount(m
);
832 br_write_lock(vfsmount_lock
);
833 if (mnt
->mnt_pinned
) {
834 mnt_add_count(mnt
, 1);
837 br_write_unlock(vfsmount_lock
);
839 EXPORT_SYMBOL(mnt_unpin
);
841 static inline void mangle(struct seq_file
*m
, const char *s
)
843 seq_escape(m
, s
, " \t\n\\");
847 * Simple .show_options callback for filesystems which don't want to
848 * implement more complex mount option showing.
850 * See also save_mount_options().
852 int generic_show_options(struct seq_file
*m
, struct vfsmount
*mnt
)
857 options
= rcu_dereference(mnt
->mnt_sb
->s_options
);
859 if (options
!= NULL
&& options
[0]) {
867 EXPORT_SYMBOL(generic_show_options
);
870 * If filesystem uses generic_show_options(), this function should be
871 * called from the fill_super() callback.
873 * The .remount_fs callback usually needs to be handled in a special
874 * way, to make sure, that previous options are not overwritten if the
877 * Also note, that if the filesystem's .remount_fs function doesn't
878 * reset all options to their default value, but changes only newly
879 * given options, then the displayed options will not reflect reality
882 void save_mount_options(struct super_block
*sb
, char *options
)
884 BUG_ON(sb
->s_options
);
885 rcu_assign_pointer(sb
->s_options
, kstrdup(options
, GFP_KERNEL
));
887 EXPORT_SYMBOL(save_mount_options
);
889 void replace_mount_options(struct super_block
*sb
, char *options
)
891 char *old
= sb
->s_options
;
892 rcu_assign_pointer(sb
->s_options
, options
);
898 EXPORT_SYMBOL(replace_mount_options
);
900 #ifdef CONFIG_PROC_FS
901 /* iterator; we want it to have access to namespace_sem, thus here... */
902 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
904 struct proc_mounts
*p
= container_of(m
, struct proc_mounts
, m
);
906 down_read(&namespace_sem
);
907 return seq_list_start(&p
->ns
->list
, *pos
);
910 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
912 struct proc_mounts
*p
= container_of(m
, struct proc_mounts
, m
);
914 return seq_list_next(v
, &p
->ns
->list
, pos
);
917 static void m_stop(struct seq_file
*m
, void *v
)
919 up_read(&namespace_sem
);
922 static int m_show(struct seq_file
*m
, void *v
)
924 struct proc_mounts
*p
= container_of(m
, struct proc_mounts
, m
);
925 struct mount
*r
= list_entry(v
, struct mount
, mnt_list
);
926 return p
->show(m
, &r
->mnt
);
929 const struct seq_operations mounts_op
= {
935 #endif /* CONFIG_PROC_FS */
938 * may_umount_tree - check if a mount tree is busy
939 * @mnt: root of mount tree
941 * This is called to check if a tree of mounts has any
942 * open files, pwds, chroots or sub mounts that are
945 int may_umount_tree(struct vfsmount
*m
)
947 struct mount
*mnt
= real_mount(m
);
949 int minimum_refs
= 0;
953 /* write lock needed for mnt_get_count */
954 br_write_lock(vfsmount_lock
);
955 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
956 actual_refs
+= mnt_get_count(p
);
959 br_write_unlock(vfsmount_lock
);
961 if (actual_refs
> minimum_refs
)
967 EXPORT_SYMBOL(may_umount_tree
);
970 * may_umount - check if a mount point is busy
971 * @mnt: root of mount
973 * This is called to check if a mount point has any
974 * open files, pwds, chroots or sub mounts. If the
975 * mount has sub mounts this will return busy
976 * regardless of whether the sub mounts are busy.
978 * Doesn't take quota and stuff into account. IOW, in some cases it will
979 * give false negatives. The main reason why it's here is that we need
980 * a non-destructive way to look for easily umountable filesystems.
982 int may_umount(struct vfsmount
*mnt
)
985 down_read(&namespace_sem
);
986 br_write_lock(vfsmount_lock
);
987 if (propagate_mount_busy(real_mount(mnt
), 2))
989 br_write_unlock(vfsmount_lock
);
990 up_read(&namespace_sem
);
994 EXPORT_SYMBOL(may_umount
);
996 void release_mounts(struct list_head
*head
)
999 while (!list_empty(head
)) {
1000 mnt
= list_first_entry(head
, struct mount
, mnt_hash
);
1001 list_del_init(&mnt
->mnt_hash
);
1002 if (mnt_has_parent(mnt
)) {
1003 struct dentry
*dentry
;
1006 br_write_lock(vfsmount_lock
);
1007 dentry
= mnt
->mnt_mountpoint
;
1008 m
= mnt
->mnt_parent
;
1009 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1010 mnt
->mnt_parent
= mnt
;
1012 br_write_unlock(vfsmount_lock
);
1021 * vfsmount lock must be held for write
1022 * namespace_sem must be held for write
1024 void umount_tree(struct mount
*mnt
, int propagate
, struct list_head
*kill
)
1026 LIST_HEAD(tmp_list
);
1029 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
1030 list_move(&p
->mnt_hash
, &tmp_list
);
1033 propagate_umount(&tmp_list
);
1035 list_for_each_entry(p
, &tmp_list
, mnt_hash
) {
1036 list_del_init(&p
->mnt_expire
);
1037 list_del_init(&p
->mnt_list
);
1038 __touch_mnt_namespace(p
->mnt_ns
);
1040 __mnt_make_shortterm(p
);
1041 list_del_init(&p
->mnt_child
);
1042 if (mnt_has_parent(p
)) {
1043 p
->mnt_parent
->mnt_ghosts
++;
1044 dentry_reset_mounted(p
->mnt_mountpoint
);
1046 change_mnt_propagation(p
, MS_PRIVATE
);
1048 list_splice(&tmp_list
, kill
);
1051 static void shrink_submounts(struct mount
*mnt
, struct list_head
*umounts
);
1053 static int do_umount(struct mount
*mnt
, int flags
)
1055 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1057 LIST_HEAD(umount_list
);
1059 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1064 * Allow userspace to request a mountpoint be expired rather than
1065 * unmounting unconditionally. Unmount only happens if:
1066 * (1) the mark is already set (the mark is cleared by mntput())
1067 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1069 if (flags
& MNT_EXPIRE
) {
1070 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1071 flags
& (MNT_FORCE
| MNT_DETACH
))
1075 * probably don't strictly need the lock here if we examined
1076 * all race cases, but it's a slowpath.
1078 br_write_lock(vfsmount_lock
);
1079 if (mnt_get_count(mnt
) != 2) {
1080 br_write_unlock(vfsmount_lock
);
1083 br_write_unlock(vfsmount_lock
);
1085 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1090 * If we may have to abort operations to get out of this
1091 * mount, and they will themselves hold resources we must
1092 * allow the fs to do things. In the Unix tradition of
1093 * 'Gee thats tricky lets do it in userspace' the umount_begin
1094 * might fail to complete on the first run through as other tasks
1095 * must return, and the like. Thats for the mount program to worry
1096 * about for the moment.
1099 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1100 sb
->s_op
->umount_begin(sb
);
1104 * No sense to grab the lock for this test, but test itself looks
1105 * somewhat bogus. Suggestions for better replacement?
1106 * Ho-hum... In principle, we might treat that as umount + switch
1107 * to rootfs. GC would eventually take care of the old vfsmount.
1108 * Actually it makes sense, especially if rootfs would contain a
1109 * /reboot - static binary that would close all descriptors and
1110 * call reboot(9). Then init(8) could umount root and exec /reboot.
1112 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1114 * Special case for "unmounting" root ...
1115 * we just try to remount it readonly.
1117 down_write(&sb
->s_umount
);
1118 if (!(sb
->s_flags
& MS_RDONLY
))
1119 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
1120 up_write(&sb
->s_umount
);
1124 down_write(&namespace_sem
);
1125 br_write_lock(vfsmount_lock
);
1128 if (!(flags
& MNT_DETACH
))
1129 shrink_submounts(mnt
, &umount_list
);
1132 if (flags
& MNT_DETACH
|| !propagate_mount_busy(mnt
, 2)) {
1133 if (!list_empty(&mnt
->mnt_list
))
1134 umount_tree(mnt
, 1, &umount_list
);
1137 br_write_unlock(vfsmount_lock
);
1138 up_write(&namespace_sem
);
1139 release_mounts(&umount_list
);
1144 * Now umount can handle mount points as well as block devices.
1145 * This is important for filesystems which use unnamed block devices.
1147 * We now support a flag for forced unmount like the other 'big iron'
1148 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1151 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1156 int lookup_flags
= 0;
1158 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1161 if (!(flags
& UMOUNT_NOFOLLOW
))
1162 lookup_flags
|= LOOKUP_FOLLOW
;
1164 retval
= user_path_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1167 mnt
= real_mount(path
.mnt
);
1169 if (path
.dentry
!= path
.mnt
->mnt_root
)
1171 if (!check_mnt(mnt
))
1175 if (!capable(CAP_SYS_ADMIN
))
1178 retval
= do_umount(mnt
, flags
);
1180 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1182 mntput_no_expire(mnt
);
1187 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1190 * The 2.0 compatible umount. No flags.
1192 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1194 return sys_umount(name
, 0);
1199 static int mount_is_safe(struct path
*path
)
1201 if (capable(CAP_SYS_ADMIN
))
1205 if (S_ISLNK(path
->dentry
->d_inode
->i_mode
))
1207 if (path
->dentry
->d_inode
->i_mode
& S_ISVTX
) {
1208 if (current_uid() != path
->dentry
->d_inode
->i_uid
)
1211 if (inode_permission(path
->dentry
->d_inode
, MAY_WRITE
))
1217 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1220 struct mount
*res
, *p
, *q
, *r
;
1223 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(mnt
))
1226 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1229 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1232 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1234 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1237 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1238 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(s
)) {
1239 s
= skip_mnt_tree(s
);
1242 while (p
!= s
->mnt_parent
) {
1248 path
.dentry
= p
->mnt_mountpoint
;
1249 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
1252 br_write_lock(vfsmount_lock
);
1253 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1254 attach_mnt(q
, &path
);
1255 br_write_unlock(vfsmount_lock
);
1261 LIST_HEAD(umount_list
);
1262 br_write_lock(vfsmount_lock
);
1263 umount_tree(res
, 0, &umount_list
);
1264 br_write_unlock(vfsmount_lock
);
1265 release_mounts(&umount_list
);
1270 struct vfsmount
*collect_mounts(struct path
*path
)
1273 down_write(&namespace_sem
);
1274 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
1275 CL_COPY_ALL
| CL_PRIVATE
);
1276 up_write(&namespace_sem
);
1277 return tree
? &tree
->mnt
: NULL
;
1280 void drop_collected_mounts(struct vfsmount
*mnt
)
1282 LIST_HEAD(umount_list
);
1283 down_write(&namespace_sem
);
1284 br_write_lock(vfsmount_lock
);
1285 umount_tree(real_mount(mnt
), 0, &umount_list
);
1286 br_write_unlock(vfsmount_lock
);
1287 up_write(&namespace_sem
);
1288 release_mounts(&umount_list
);
1291 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1292 struct vfsmount
*root
)
1295 int res
= f(root
, arg
);
1298 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
1299 res
= f(&mnt
->mnt
, arg
);
1306 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
1310 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
1311 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
1312 mnt_release_group_id(p
);
1316 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
1320 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
1321 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
1322 int err
= mnt_alloc_group_id(p
);
1324 cleanup_group_ids(mnt
, p
);
1334 * @source_mnt : mount tree to be attached
1335 * @nd : place the mount tree @source_mnt is attached
1336 * @parent_nd : if non-null, detach the source_mnt from its parent and
1337 * store the parent mount and mountpoint dentry.
1338 * (done when source_mnt is moved)
1340 * NOTE: in the table below explains the semantics when a source mount
1341 * of a given type is attached to a destination mount of a given type.
1342 * ---------------------------------------------------------------------------
1343 * | BIND MOUNT OPERATION |
1344 * |**************************************************************************
1345 * | source-->| shared | private | slave | unbindable |
1349 * |**************************************************************************
1350 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1352 * |non-shared| shared (+) | private | slave (*) | invalid |
1353 * ***************************************************************************
1354 * A bind operation clones the source mount and mounts the clone on the
1355 * destination mount.
1357 * (++) the cloned mount is propagated to all the mounts in the propagation
1358 * tree of the destination mount and the cloned mount is added to
1359 * the peer group of the source mount.
1360 * (+) the cloned mount is created under the destination mount and is marked
1361 * as shared. The cloned mount is added to the peer group of the source
1363 * (+++) the mount is propagated to all the mounts in the propagation tree
1364 * of the destination mount and the cloned mount is made slave
1365 * of the same master as that of the source mount. The cloned mount
1366 * is marked as 'shared and slave'.
1367 * (*) the cloned mount is made a slave of the same master as that of the
1370 * ---------------------------------------------------------------------------
1371 * | MOVE MOUNT OPERATION |
1372 * |**************************************************************************
1373 * | source-->| shared | private | slave | unbindable |
1377 * |**************************************************************************
1378 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1380 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1381 * ***************************************************************************
1383 * (+) the mount is moved to the destination. And is then propagated to
1384 * all the mounts in the propagation tree of the destination mount.
1385 * (+*) the mount is moved to the destination.
1386 * (+++) the mount is moved to the destination and is then propagated to
1387 * all the mounts belonging to the destination mount's propagation tree.
1388 * the mount is marked as 'shared and slave'.
1389 * (*) the mount continues to be a slave at the new location.
1391 * if the source mount is a tree, the operations explained above is
1392 * applied to each mount in the tree.
1393 * Must be called without spinlocks held, since this function can sleep
1396 static int attach_recursive_mnt(struct mount
*source_mnt
,
1397 struct path
*path
, struct path
*parent_path
)
1399 LIST_HEAD(tree_list
);
1400 struct mount
*dest_mnt
= real_mount(path
->mnt
);
1401 struct dentry
*dest_dentry
= path
->dentry
;
1402 struct mount
*child
, *p
;
1405 if (IS_MNT_SHARED(dest_mnt
)) {
1406 err
= invent_group_ids(source_mnt
, true);
1410 err
= propagate_mnt(dest_mnt
, dest_dentry
, source_mnt
, &tree_list
);
1412 goto out_cleanup_ids
;
1414 br_write_lock(vfsmount_lock
);
1416 if (IS_MNT_SHARED(dest_mnt
)) {
1417 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
1421 detach_mnt(source_mnt
, parent_path
);
1422 attach_mnt(source_mnt
, path
);
1423 touch_mnt_namespace(source_mnt
->mnt_ns
);
1425 mnt_set_mountpoint(dest_mnt
, dest_dentry
, source_mnt
);
1426 commit_tree(source_mnt
);
1429 list_for_each_entry_safe(child
, p
, &tree_list
, mnt_hash
) {
1430 list_del_init(&child
->mnt_hash
);
1433 br_write_unlock(vfsmount_lock
);
1438 if (IS_MNT_SHARED(dest_mnt
))
1439 cleanup_group_ids(source_mnt
, NULL
);
1444 static int lock_mount(struct path
*path
)
1446 struct vfsmount
*mnt
;
1448 mutex_lock(&path
->dentry
->d_inode
->i_mutex
);
1449 if (unlikely(cant_mount(path
->dentry
))) {
1450 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1453 down_write(&namespace_sem
);
1454 mnt
= lookup_mnt(path
);
1457 up_write(&namespace_sem
);
1458 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1461 path
->dentry
= dget(mnt
->mnt_root
);
1465 static void unlock_mount(struct path
*path
)
1467 up_write(&namespace_sem
);
1468 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1471 static int graft_tree(struct mount
*mnt
, struct path
*path
)
1473 if (mnt
->mnt
.mnt_sb
->s_flags
& MS_NOUSER
)
1476 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
1477 S_ISDIR(mnt
->mnt
.mnt_root
->d_inode
->i_mode
))
1480 if (d_unlinked(path
->dentry
))
1483 return attach_recursive_mnt(mnt
, path
, NULL
);
1487 * Sanity check the flags to change_mnt_propagation.
1490 static int flags_to_propagation_type(int flags
)
1492 int type
= flags
& ~(MS_REC
| MS_SILENT
);
1494 /* Fail if any non-propagation flags are set */
1495 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
1497 /* Only one propagation flag should be set */
1498 if (!is_power_of_2(type
))
1504 * recursively change the type of the mountpoint.
1506 static int do_change_type(struct path
*path
, int flag
)
1509 struct mount
*mnt
= real_mount(path
->mnt
);
1510 int recurse
= flag
& MS_REC
;
1514 if (!capable(CAP_SYS_ADMIN
))
1517 if (path
->dentry
!= path
->mnt
->mnt_root
)
1520 type
= flags_to_propagation_type(flag
);
1524 down_write(&namespace_sem
);
1525 if (type
== MS_SHARED
) {
1526 err
= invent_group_ids(mnt
, recurse
);
1531 br_write_lock(vfsmount_lock
);
1532 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
1533 change_mnt_propagation(m
, type
);
1534 br_write_unlock(vfsmount_lock
);
1537 up_write(&namespace_sem
);
1542 * do loopback mount.
1544 static int do_loopback(struct path
*path
, char *old_name
,
1547 LIST_HEAD(umount_list
);
1548 struct path old_path
;
1549 struct mount
*mnt
= NULL
, *old
;
1550 int err
= mount_is_safe(path
);
1553 if (!old_name
|| !*old_name
)
1555 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
1559 err
= lock_mount(path
);
1563 old
= real_mount(old_path
.mnt
);
1566 if (IS_MNT_UNBINDABLE(old
))
1569 if (!check_mnt(real_mount(path
->mnt
)) || !check_mnt(old
))
1574 mnt
= copy_tree(old
, old_path
.dentry
, 0);
1576 mnt
= clone_mnt(old
, old_path
.dentry
, 0);
1581 err
= graft_tree(mnt
, path
);
1583 br_write_lock(vfsmount_lock
);
1584 umount_tree(mnt
, 0, &umount_list
);
1585 br_write_unlock(vfsmount_lock
);
1589 release_mounts(&umount_list
);
1591 path_put(&old_path
);
1595 static int change_mount_flags(struct vfsmount
*mnt
, int ms_flags
)
1598 int readonly_request
= 0;
1600 if (ms_flags
& MS_RDONLY
)
1601 readonly_request
= 1;
1602 if (readonly_request
== __mnt_is_readonly(mnt
))
1605 if (readonly_request
)
1606 error
= mnt_make_readonly(real_mount(mnt
));
1608 __mnt_unmake_readonly(real_mount(mnt
));
1613 * change filesystem flags. dir should be a physical root of filesystem.
1614 * If you've mounted a non-root directory somewhere and want to do remount
1615 * on it - tough luck.
1617 static int do_remount(struct path
*path
, int flags
, int mnt_flags
,
1621 struct super_block
*sb
= path
->mnt
->mnt_sb
;
1622 struct mount
*mnt
= real_mount(path
->mnt
);
1624 if (!capable(CAP_SYS_ADMIN
))
1627 if (!check_mnt(mnt
))
1630 if (path
->dentry
!= path
->mnt
->mnt_root
)
1633 err
= security_sb_remount(sb
, data
);
1637 down_write(&sb
->s_umount
);
1638 if (flags
& MS_BIND
)
1639 err
= change_mount_flags(path
->mnt
, flags
);
1641 err
= do_remount_sb(sb
, flags
, data
, 0);
1643 br_write_lock(vfsmount_lock
);
1644 mnt_flags
|= mnt
->mnt
.mnt_flags
& MNT_PROPAGATION_MASK
;
1645 mnt
->mnt
.mnt_flags
= mnt_flags
;
1646 br_write_unlock(vfsmount_lock
);
1648 up_write(&sb
->s_umount
);
1650 br_write_lock(vfsmount_lock
);
1651 touch_mnt_namespace(mnt
->mnt_ns
);
1652 br_write_unlock(vfsmount_lock
);
1657 static inline int tree_contains_unbindable(struct mount
*mnt
)
1660 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1661 if (IS_MNT_UNBINDABLE(p
))
1667 static int do_move_mount(struct path
*path
, char *old_name
)
1669 struct path old_path
, parent_path
;
1673 if (!capable(CAP_SYS_ADMIN
))
1675 if (!old_name
|| !*old_name
)
1677 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
1681 err
= lock_mount(path
);
1685 old
= real_mount(old_path
.mnt
);
1686 p
= real_mount(path
->mnt
);
1689 if (!check_mnt(p
) || !check_mnt(old
))
1692 if (d_unlinked(path
->dentry
))
1696 if (old_path
.dentry
!= old_path
.mnt
->mnt_root
)
1699 if (!mnt_has_parent(old
))
1702 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
1703 S_ISDIR(old_path
.dentry
->d_inode
->i_mode
))
1706 * Don't move a mount residing in a shared parent.
1708 if (IS_MNT_SHARED(old
->mnt_parent
))
1711 * Don't move a mount tree containing unbindable mounts to a destination
1712 * mount which is shared.
1714 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
1717 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
1721 err
= attach_recursive_mnt(old
, path
, &parent_path
);
1725 /* if the mount is moved, it should no longer be expire
1727 list_del_init(&old
->mnt_expire
);
1732 path_put(&parent_path
);
1733 path_put(&old_path
);
1737 static struct vfsmount
*fs_set_subtype(struct vfsmount
*mnt
, const char *fstype
)
1740 const char *subtype
= strchr(fstype
, '.');
1749 mnt
->mnt_sb
->s_subtype
= kstrdup(subtype
, GFP_KERNEL
);
1751 if (!mnt
->mnt_sb
->s_subtype
)
1757 return ERR_PTR(err
);
1760 static struct vfsmount
*
1761 do_kern_mount(const char *fstype
, int flags
, const char *name
, void *data
)
1763 struct file_system_type
*type
= get_fs_type(fstype
);
1764 struct vfsmount
*mnt
;
1766 return ERR_PTR(-ENODEV
);
1767 mnt
= vfs_kern_mount(type
, flags
, name
, data
);
1768 if (!IS_ERR(mnt
) && (type
->fs_flags
& FS_HAS_SUBTYPE
) &&
1769 !mnt
->mnt_sb
->s_subtype
)
1770 mnt
= fs_set_subtype(mnt
, fstype
);
1771 put_filesystem(type
);
1776 * add a mount into a namespace's mount tree
1778 static int do_add_mount(struct mount
*newmnt
, struct path
*path
, int mnt_flags
)
1782 mnt_flags
&= ~(MNT_SHARED
| MNT_WRITE_HOLD
| MNT_INTERNAL
);
1784 err
= lock_mount(path
);
1789 if (!(mnt_flags
& MNT_SHRINKABLE
) && !check_mnt(real_mount(path
->mnt
)))
1792 /* Refuse the same filesystem on the same mount point */
1794 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
1795 path
->mnt
->mnt_root
== path
->dentry
)
1799 if (S_ISLNK(newmnt
->mnt
.mnt_root
->d_inode
->i_mode
))
1802 newmnt
->mnt
.mnt_flags
= mnt_flags
;
1803 err
= graft_tree(newmnt
, path
);
1811 * create a new mount for userspace and request it to be added into the
1814 static int do_new_mount(struct path
*path
, char *type
, int flags
,
1815 int mnt_flags
, char *name
, void *data
)
1817 struct vfsmount
*mnt
;
1823 /* we need capabilities... */
1824 if (!capable(CAP_SYS_ADMIN
))
1827 mnt
= do_kern_mount(type
, flags
, name
, data
);
1829 return PTR_ERR(mnt
);
1831 err
= do_add_mount(real_mount(mnt
), path
, mnt_flags
);
1837 int finish_automount(struct vfsmount
*m
, struct path
*path
)
1839 struct mount
*mnt
= real_mount(m
);
1841 /* The new mount record should have at least 2 refs to prevent it being
1842 * expired before we get a chance to add it
1844 BUG_ON(mnt_get_count(mnt
) < 2);
1846 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
1847 m
->mnt_root
== path
->dentry
) {
1852 err
= do_add_mount(mnt
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
1856 /* remove m from any expiration list it may be on */
1857 if (!list_empty(&mnt
->mnt_expire
)) {
1858 down_write(&namespace_sem
);
1859 br_write_lock(vfsmount_lock
);
1860 list_del_init(&mnt
->mnt_expire
);
1861 br_write_unlock(vfsmount_lock
);
1862 up_write(&namespace_sem
);
1870 * mnt_set_expiry - Put a mount on an expiration list
1871 * @mnt: The mount to list.
1872 * @expiry_list: The list to add the mount to.
1874 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
1876 down_write(&namespace_sem
);
1877 br_write_lock(vfsmount_lock
);
1879 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
1881 br_write_unlock(vfsmount_lock
);
1882 up_write(&namespace_sem
);
1884 EXPORT_SYMBOL(mnt_set_expiry
);
1887 * process a list of expirable mountpoints with the intent of discarding any
1888 * mountpoints that aren't in use and haven't been touched since last we came
1891 void mark_mounts_for_expiry(struct list_head
*mounts
)
1893 struct mount
*mnt
, *next
;
1894 LIST_HEAD(graveyard
);
1897 if (list_empty(mounts
))
1900 down_write(&namespace_sem
);
1901 br_write_lock(vfsmount_lock
);
1903 /* extract from the expiration list every vfsmount that matches the
1904 * following criteria:
1905 * - only referenced by its parent vfsmount
1906 * - still marked for expiry (marked on the last call here; marks are
1907 * cleared by mntput())
1909 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
1910 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
1911 propagate_mount_busy(mnt
, 1))
1913 list_move(&mnt
->mnt_expire
, &graveyard
);
1915 while (!list_empty(&graveyard
)) {
1916 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
1917 touch_mnt_namespace(mnt
->mnt_ns
);
1918 umount_tree(mnt
, 1, &umounts
);
1920 br_write_unlock(vfsmount_lock
);
1921 up_write(&namespace_sem
);
1923 release_mounts(&umounts
);
1926 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
1929 * Ripoff of 'select_parent()'
1931 * search the list of submounts for a given mountpoint, and move any
1932 * shrinkable submounts to the 'graveyard' list.
1934 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
1936 struct mount
*this_parent
= parent
;
1937 struct list_head
*next
;
1941 next
= this_parent
->mnt_mounts
.next
;
1943 while (next
!= &this_parent
->mnt_mounts
) {
1944 struct list_head
*tmp
= next
;
1945 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
1948 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
1951 * Descend a level if the d_mounts list is non-empty.
1953 if (!list_empty(&mnt
->mnt_mounts
)) {
1958 if (!propagate_mount_busy(mnt
, 1)) {
1959 list_move_tail(&mnt
->mnt_expire
, graveyard
);
1964 * All done at this level ... ascend and resume the search
1966 if (this_parent
!= parent
) {
1967 next
= this_parent
->mnt_child
.next
;
1968 this_parent
= this_parent
->mnt_parent
;
1975 * process a list of expirable mountpoints with the intent of discarding any
1976 * submounts of a specific parent mountpoint
1978 * vfsmount_lock must be held for write
1980 static void shrink_submounts(struct mount
*mnt
, struct list_head
*umounts
)
1982 LIST_HEAD(graveyard
);
1985 /* extract submounts of 'mountpoint' from the expiration list */
1986 while (select_submounts(mnt
, &graveyard
)) {
1987 while (!list_empty(&graveyard
)) {
1988 m
= list_first_entry(&graveyard
, struct mount
,
1990 touch_mnt_namespace(m
->mnt_ns
);
1991 umount_tree(m
, 1, umounts
);
1997 * Some copy_from_user() implementations do not return the exact number of
1998 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
1999 * Note that this function differs from copy_from_user() in that it will oops
2000 * on bad values of `to', rather than returning a short copy.
2002 static long exact_copy_from_user(void *to
, const void __user
* from
,
2006 const char __user
*f
= from
;
2009 if (!access_ok(VERIFY_READ
, from
, n
))
2013 if (__get_user(c
, f
)) {
2024 int copy_mount_options(const void __user
* data
, unsigned long *where
)
2034 if (!(page
= __get_free_page(GFP_KERNEL
)))
2037 /* We only care that *some* data at the address the user
2038 * gave us is valid. Just in case, we'll zero
2039 * the remainder of the page.
2041 /* copy_from_user cannot cross TASK_SIZE ! */
2042 size
= TASK_SIZE
- (unsigned long)data
;
2043 if (size
> PAGE_SIZE
)
2046 i
= size
- exact_copy_from_user((void *)page
, data
, size
);
2052 memset((char *)page
+ i
, 0, PAGE_SIZE
- i
);
2057 int copy_mount_string(const void __user
*data
, char **where
)
2066 tmp
= strndup_user(data
, PAGE_SIZE
);
2068 return PTR_ERR(tmp
);
2075 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2076 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2078 * data is a (void *) that can point to any structure up to
2079 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2080 * information (or be NULL).
2082 * Pre-0.97 versions of mount() didn't have a flags word.
2083 * When the flags word was introduced its top half was required
2084 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2085 * Therefore, if this magic number is present, it carries no information
2086 * and must be discarded.
2088 long do_mount(char *dev_name
, char *dir_name
, char *type_page
,
2089 unsigned long flags
, void *data_page
)
2096 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
2097 flags
&= ~MS_MGC_MSK
;
2099 /* Basic sanity checks */
2101 if (!dir_name
|| !*dir_name
|| !memchr(dir_name
, 0, PAGE_SIZE
))
2105 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
2107 /* ... and get the mountpoint */
2108 retval
= kern_path(dir_name
, LOOKUP_FOLLOW
, &path
);
2112 retval
= security_sb_mount(dev_name
, &path
,
2113 type_page
, flags
, data_page
);
2117 /* Default to relatime unless overriden */
2118 if (!(flags
& MS_NOATIME
))
2119 mnt_flags
|= MNT_RELATIME
;
2121 /* Separate the per-mountpoint flags */
2122 if (flags
& MS_NOSUID
)
2123 mnt_flags
|= MNT_NOSUID
;
2124 if (flags
& MS_NODEV
)
2125 mnt_flags
|= MNT_NODEV
;
2126 if (flags
& MS_NOEXEC
)
2127 mnt_flags
|= MNT_NOEXEC
;
2128 if (flags
& MS_NOATIME
)
2129 mnt_flags
|= MNT_NOATIME
;
2130 if (flags
& MS_NODIRATIME
)
2131 mnt_flags
|= MNT_NODIRATIME
;
2132 if (flags
& MS_STRICTATIME
)
2133 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
2134 if (flags
& MS_RDONLY
)
2135 mnt_flags
|= MNT_READONLY
;
2137 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
| MS_BORN
|
2138 MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
| MS_KERNMOUNT
|
2141 if (flags
& MS_REMOUNT
)
2142 retval
= do_remount(&path
, flags
& ~MS_REMOUNT
, mnt_flags
,
2144 else if (flags
& MS_BIND
)
2145 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
2146 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2147 retval
= do_change_type(&path
, flags
);
2148 else if (flags
& MS_MOVE
)
2149 retval
= do_move_mount(&path
, dev_name
);
2151 retval
= do_new_mount(&path
, type_page
, flags
, mnt_flags
,
2152 dev_name
, data_page
);
2158 static struct mnt_namespace
*alloc_mnt_ns(void)
2160 struct mnt_namespace
*new_ns
;
2162 new_ns
= kmalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
2164 return ERR_PTR(-ENOMEM
);
2165 atomic_set(&new_ns
->count
, 1);
2166 new_ns
->root
= NULL
;
2167 INIT_LIST_HEAD(&new_ns
->list
);
2168 init_waitqueue_head(&new_ns
->poll
);
2173 void mnt_make_longterm(struct vfsmount
*mnt
)
2175 __mnt_make_longterm(real_mount(mnt
));
2178 void mnt_make_shortterm(struct vfsmount
*m
)
2181 struct mount
*mnt
= real_mount(m
);
2182 if (atomic_add_unless(&mnt
->mnt_longterm
, -1, 1))
2184 br_write_lock(vfsmount_lock
);
2185 atomic_dec(&mnt
->mnt_longterm
);
2186 br_write_unlock(vfsmount_lock
);
2191 * Allocate a new namespace structure and populate it with contents
2192 * copied from the namespace of the passed in task structure.
2194 static struct mnt_namespace
*dup_mnt_ns(struct mnt_namespace
*mnt_ns
,
2195 struct fs_struct
*fs
)
2197 struct mnt_namespace
*new_ns
;
2198 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
2199 struct mount
*p
, *q
;
2200 struct mount
*old
= real_mount(mnt_ns
->root
);
2203 new_ns
= alloc_mnt_ns();
2207 down_write(&namespace_sem
);
2208 /* First pass: copy the tree topology */
2209 new = copy_tree(old
, old
->mnt
.mnt_root
, CL_COPY_ALL
| CL_EXPIRE
);
2211 up_write(&namespace_sem
);
2213 return ERR_PTR(-ENOMEM
);
2215 new_ns
->root
= &new->mnt
;
2216 br_write_lock(vfsmount_lock
);
2217 list_add_tail(&new_ns
->list
, &new->mnt_list
);
2218 br_write_unlock(vfsmount_lock
);
2221 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2222 * as belonging to new namespace. We have already acquired a private
2223 * fs_struct, so tsk->fs->lock is not needed.
2229 __mnt_make_longterm(q
);
2231 if (&p
->mnt
== fs
->root
.mnt
) {
2232 fs
->root
.mnt
= mntget(&q
->mnt
);
2233 __mnt_make_longterm(q
);
2234 mnt_make_shortterm(&p
->mnt
);
2237 if (&p
->mnt
== fs
->pwd
.mnt
) {
2238 fs
->pwd
.mnt
= mntget(&q
->mnt
);
2239 __mnt_make_longterm(q
);
2240 mnt_make_shortterm(&p
->mnt
);
2244 p
= next_mnt(p
, old
);
2245 q
= next_mnt(q
, new);
2247 up_write(&namespace_sem
);
2257 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
2258 struct fs_struct
*new_fs
)
2260 struct mnt_namespace
*new_ns
;
2265 if (!(flags
& CLONE_NEWNS
))
2268 new_ns
= dup_mnt_ns(ns
, new_fs
);
2275 * create_mnt_ns - creates a private namespace and adds a root filesystem
2276 * @mnt: pointer to the new root filesystem mountpoint
2278 static struct mnt_namespace
*create_mnt_ns(struct vfsmount
*m
)
2280 struct mnt_namespace
*new_ns
= alloc_mnt_ns();
2281 if (!IS_ERR(new_ns
)) {
2282 struct mount
*mnt
= real_mount(m
);
2283 mnt
->mnt_ns
= new_ns
;
2284 __mnt_make_longterm(mnt
);
2286 list_add(&new_ns
->list
, &mnt
->mnt_list
);
2293 struct dentry
*mount_subtree(struct vfsmount
*mnt
, const char *name
)
2295 struct mnt_namespace
*ns
;
2296 struct super_block
*s
;
2300 ns
= create_mnt_ns(mnt
);
2302 return ERR_CAST(ns
);
2304 err
= vfs_path_lookup(mnt
->mnt_root
, mnt
,
2305 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
2310 return ERR_PTR(err
);
2312 /* trade a vfsmount reference for active sb one */
2313 s
= path
.mnt
->mnt_sb
;
2314 atomic_inc(&s
->s_active
);
2316 /* lock the sucker */
2317 down_write(&s
->s_umount
);
2318 /* ... and return the root of (sub)tree on it */
2321 EXPORT_SYMBOL(mount_subtree
);
2323 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
2324 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
2330 unsigned long data_page
;
2332 ret
= copy_mount_string(type
, &kernel_type
);
2336 kernel_dir
= getname(dir_name
);
2337 if (IS_ERR(kernel_dir
)) {
2338 ret
= PTR_ERR(kernel_dir
);
2342 ret
= copy_mount_string(dev_name
, &kernel_dev
);
2346 ret
= copy_mount_options(data
, &data_page
);
2350 ret
= do_mount(kernel_dev
, kernel_dir
, kernel_type
, flags
,
2351 (void *) data_page
);
2353 free_page(data_page
);
2357 putname(kernel_dir
);
2365 * Return true if path is reachable from root
2367 * namespace_sem or vfsmount_lock is held
2369 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
2370 const struct path
*root
)
2372 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
2373 dentry
= mnt
->mnt_mountpoint
;
2374 mnt
= mnt
->mnt_parent
;
2376 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
2379 int path_is_under(struct path
*path1
, struct path
*path2
)
2382 br_read_lock(vfsmount_lock
);
2383 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
2384 br_read_unlock(vfsmount_lock
);
2387 EXPORT_SYMBOL(path_is_under
);
2390 * pivot_root Semantics:
2391 * Moves the root file system of the current process to the directory put_old,
2392 * makes new_root as the new root file system of the current process, and sets
2393 * root/cwd of all processes which had them on the current root to new_root.
2396 * The new_root and put_old must be directories, and must not be on the
2397 * same file system as the current process root. The put_old must be
2398 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2399 * pointed to by put_old must yield the same directory as new_root. No other
2400 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2402 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2403 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2404 * in this situation.
2407 * - we don't move root/cwd if they are not at the root (reason: if something
2408 * cared enough to change them, it's probably wrong to force them elsewhere)
2409 * - it's okay to pick a root that isn't the root of a file system, e.g.
2410 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2411 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2414 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
2415 const char __user
*, put_old
)
2417 struct path
new, old
, parent_path
, root_parent
, root
;
2418 struct mount
*new_mnt
, *root_mnt
;
2421 if (!capable(CAP_SYS_ADMIN
))
2424 error
= user_path_dir(new_root
, &new);
2428 error
= user_path_dir(put_old
, &old
);
2432 error
= security_sb_pivotroot(&old
, &new);
2436 get_fs_root(current
->fs
, &root
);
2437 error
= lock_mount(&old
);
2442 new_mnt
= real_mount(new.mnt
);
2443 root_mnt
= real_mount(root
.mnt
);
2444 if (IS_MNT_SHARED(real_mount(old
.mnt
)) ||
2445 IS_MNT_SHARED(new_mnt
->mnt_parent
) ||
2446 IS_MNT_SHARED(root_mnt
->mnt_parent
))
2448 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
2451 if (d_unlinked(new.dentry
))
2453 if (d_unlinked(old
.dentry
))
2456 if (new.mnt
== root
.mnt
||
2457 old
.mnt
== root
.mnt
)
2458 goto out4
; /* loop, on the same file system */
2460 if (root
.mnt
->mnt_root
!= root
.dentry
)
2461 goto out4
; /* not a mountpoint */
2462 if (!mnt_has_parent(root_mnt
))
2463 goto out4
; /* not attached */
2464 if (new.mnt
->mnt_root
!= new.dentry
)
2465 goto out4
; /* not a mountpoint */
2466 if (!mnt_has_parent(new_mnt
))
2467 goto out4
; /* not attached */
2468 /* make sure we can reach put_old from new_root */
2469 if (!is_path_reachable(real_mount(old
.mnt
), old
.dentry
, &new))
2471 br_write_lock(vfsmount_lock
);
2472 detach_mnt(new_mnt
, &parent_path
);
2473 detach_mnt(root_mnt
, &root_parent
);
2474 /* mount old root on put_old */
2475 attach_mnt(root_mnt
, &old
);
2476 /* mount new_root on / */
2477 attach_mnt(new_mnt
, &root_parent
);
2478 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
2479 br_write_unlock(vfsmount_lock
);
2480 chroot_fs_refs(&root
, &new);
2485 path_put(&root_parent
);
2486 path_put(&parent_path
);
2498 static void __init
init_mount_tree(void)
2500 struct vfsmount
*mnt
;
2501 struct mnt_namespace
*ns
;
2504 mnt
= do_kern_mount("rootfs", 0, "rootfs", NULL
);
2506 panic("Can't create rootfs");
2508 ns
= create_mnt_ns(mnt
);
2510 panic("Can't allocate initial namespace");
2512 init_task
.nsproxy
->mnt_ns
= ns
;
2515 root
.mnt
= ns
->root
;
2516 root
.dentry
= ns
->root
->mnt_root
;
2518 set_fs_pwd(current
->fs
, &root
);
2519 set_fs_root(current
->fs
, &root
);
2522 void __init
mnt_init(void)
2527 init_rwsem(&namespace_sem
);
2529 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
2530 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
2532 mount_hashtable
= (struct list_head
*)__get_free_page(GFP_ATOMIC
);
2534 if (!mount_hashtable
)
2535 panic("Failed to allocate mount hash table\n");
2537 printk(KERN_INFO
"Mount-cache hash table entries: %lu\n", HASH_SIZE
);
2539 for (u
= 0; u
< HASH_SIZE
; u
++)
2540 INIT_LIST_HEAD(&mount_hashtable
[u
]);
2542 br_lock_init(vfsmount_lock
);
2546 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
2548 fs_kobj
= kobject_create_and_add("fs", NULL
);
2550 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
2555 void put_mnt_ns(struct mnt_namespace
*ns
)
2557 LIST_HEAD(umount_list
);
2559 if (!atomic_dec_and_test(&ns
->count
))
2561 down_write(&namespace_sem
);
2562 br_write_lock(vfsmount_lock
);
2563 umount_tree(real_mount(ns
->root
), 0, &umount_list
);
2564 br_write_unlock(vfsmount_lock
);
2565 up_write(&namespace_sem
);
2566 release_mounts(&umount_list
);
2570 struct vfsmount
*kern_mount_data(struct file_system_type
*type
, void *data
)
2572 struct vfsmount
*mnt
;
2573 mnt
= vfs_kern_mount(type
, MS_KERNMOUNT
, type
->name
, data
);
2576 * it is a longterm mount, don't release mnt until
2577 * we unmount before file sys is unregistered
2579 mnt_make_longterm(mnt
);
2583 EXPORT_SYMBOL_GPL(kern_mount_data
);
2585 void kern_unmount(struct vfsmount
*mnt
)
2587 /* release long term mount so mount point can be released */
2588 if (!IS_ERR_OR_NULL(mnt
)) {
2589 mnt_make_shortterm(mnt
);
2593 EXPORT_SYMBOL(kern_unmount
);
2595 bool our_mnt(struct vfsmount
*mnt
)
2597 return check_mnt(real_mount(mnt
));