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/smp_lock.h>
15 #include <linux/init.h>
16 #include <linux/kernel.h>
17 #include <linux/acct.h>
18 #include <linux/capability.h>
19 #include <linux/cpumask.h>
20 #include <linux/module.h>
21 #include <linux/sysfs.h>
22 #include <linux/seq_file.h>
23 #include <linux/mnt_namespace.h>
24 #include <linux/namei.h>
25 #include <linux/nsproxy.h>
26 #include <linux/security.h>
27 #include <linux/mount.h>
28 #include <linux/ramfs.h>
29 #include <linux/log2.h>
30 #include <linux/idr.h>
31 #include <linux/fs_struct.h>
32 #include <linux/fsnotify.h>
33 #include <asm/uaccess.h>
34 #include <asm/unistd.h>
38 #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
39 #define HASH_SIZE (1UL << HASH_SHIFT)
41 /* spinlock for vfsmount related operations, inplace of dcache_lock */
42 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(vfsmount_lock
);
45 static DEFINE_IDA(mnt_id_ida
);
46 static DEFINE_IDA(mnt_group_ida
);
47 static int mnt_id_start
= 0;
48 static int mnt_group_start
= 1;
50 static struct list_head
*mount_hashtable __read_mostly
;
51 static struct kmem_cache
*mnt_cache __read_mostly
;
52 static struct rw_semaphore namespace_sem
;
55 struct kobject
*fs_kobj
;
56 EXPORT_SYMBOL_GPL(fs_kobj
);
58 static inline unsigned long hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
60 unsigned long tmp
= ((unsigned long)mnt
/ L1_CACHE_BYTES
);
61 tmp
+= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
62 tmp
= tmp
+ (tmp
>> HASH_SHIFT
);
63 return tmp
& (HASH_SIZE
- 1);
66 #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
68 /* allocation is serialized by namespace_sem */
69 static int mnt_alloc_id(struct vfsmount
*mnt
)
74 ida_pre_get(&mnt_id_ida
, GFP_KERNEL
);
75 spin_lock(&vfsmount_lock
);
76 res
= ida_get_new_above(&mnt_id_ida
, mnt_id_start
, &mnt
->mnt_id
);
78 mnt_id_start
= mnt
->mnt_id
+ 1;
79 spin_unlock(&vfsmount_lock
);
86 static void mnt_free_id(struct vfsmount
*mnt
)
89 spin_lock(&vfsmount_lock
);
90 ida_remove(&mnt_id_ida
, id
);
91 if (mnt_id_start
> id
)
93 spin_unlock(&vfsmount_lock
);
97 * Allocate a new peer group ID
99 * mnt_group_ida is protected by namespace_sem
101 static int mnt_alloc_group_id(struct vfsmount
*mnt
)
105 if (!ida_pre_get(&mnt_group_ida
, GFP_KERNEL
))
108 res
= ida_get_new_above(&mnt_group_ida
,
112 mnt_group_start
= mnt
->mnt_group_id
+ 1;
118 * Release a peer group ID
120 void mnt_release_group_id(struct vfsmount
*mnt
)
122 int id
= mnt
->mnt_group_id
;
123 ida_remove(&mnt_group_ida
, id
);
124 if (mnt_group_start
> id
)
125 mnt_group_start
= id
;
126 mnt
->mnt_group_id
= 0;
129 struct vfsmount
*alloc_vfsmnt(const char *name
)
131 struct vfsmount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
135 err
= mnt_alloc_id(mnt
);
140 mnt
->mnt_devname
= kstrdup(name
, GFP_KERNEL
);
141 if (!mnt
->mnt_devname
)
145 atomic_set(&mnt
->mnt_count
, 1);
146 INIT_LIST_HEAD(&mnt
->mnt_hash
);
147 INIT_LIST_HEAD(&mnt
->mnt_child
);
148 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
149 INIT_LIST_HEAD(&mnt
->mnt_list
);
150 INIT_LIST_HEAD(&mnt
->mnt_expire
);
151 INIT_LIST_HEAD(&mnt
->mnt_share
);
152 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
153 INIT_LIST_HEAD(&mnt
->mnt_slave
);
154 #ifdef CONFIG_FSNOTIFY
155 INIT_HLIST_HEAD(&mnt
->mnt_fsnotify_marks
);
158 mnt
->mnt_writers
= alloc_percpu(int);
159 if (!mnt
->mnt_writers
)
160 goto out_free_devname
;
162 mnt
->mnt_writers
= 0;
169 kfree(mnt
->mnt_devname
);
174 kmem_cache_free(mnt_cache
, mnt
);
179 * Most r/o checks on a fs are for operations that take
180 * discrete amounts of time, like a write() or unlink().
181 * We must keep track of when those operations start
182 * (for permission checks) and when they end, so that
183 * we can determine when writes are able to occur to
187 * __mnt_is_readonly: check whether a mount is read-only
188 * @mnt: the mount to check for its write status
190 * This shouldn't be used directly ouside of the VFS.
191 * It does not guarantee that the filesystem will stay
192 * r/w, just that it is right *now*. This can not and
193 * should not be used in place of IS_RDONLY(inode).
194 * mnt_want/drop_write() will _keep_ the filesystem
197 int __mnt_is_readonly(struct vfsmount
*mnt
)
199 if (mnt
->mnt_flags
& MNT_READONLY
)
201 if (mnt
->mnt_sb
->s_flags
& MS_RDONLY
)
205 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
207 static inline void inc_mnt_writers(struct vfsmount
*mnt
)
210 (*per_cpu_ptr(mnt
->mnt_writers
, smp_processor_id()))++;
216 static inline void dec_mnt_writers(struct vfsmount
*mnt
)
219 (*per_cpu_ptr(mnt
->mnt_writers
, smp_processor_id()))--;
225 static unsigned int count_mnt_writers(struct vfsmount
*mnt
)
228 unsigned int count
= 0;
231 for_each_possible_cpu(cpu
) {
232 count
+= *per_cpu_ptr(mnt
->mnt_writers
, cpu
);
237 return mnt
->mnt_writers
;
242 * Most r/o checks on a fs are for operations that take
243 * discrete amounts of time, like a write() or unlink().
244 * We must keep track of when those operations start
245 * (for permission checks) and when they end, so that
246 * we can determine when writes are able to occur to
250 * mnt_want_write - get write access to a mount
251 * @mnt: the mount on which to take a write
253 * This tells the low-level filesystem that a write is
254 * about to be performed to it, and makes sure that
255 * writes are allowed before returning success. When
256 * the write operation is finished, mnt_drop_write()
257 * must be called. This is effectively a refcount.
259 int mnt_want_write(struct vfsmount
*mnt
)
264 inc_mnt_writers(mnt
);
266 * The store to inc_mnt_writers must be visible before we pass
267 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
268 * incremented count after it has set MNT_WRITE_HOLD.
271 while (mnt
->mnt_flags
& MNT_WRITE_HOLD
)
274 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
275 * be set to match its requirements. So we must not load that until
276 * MNT_WRITE_HOLD is cleared.
279 if (__mnt_is_readonly(mnt
)) {
280 dec_mnt_writers(mnt
);
288 EXPORT_SYMBOL_GPL(mnt_want_write
);
291 * mnt_clone_write - get write access to a mount
292 * @mnt: the mount on which to take a write
294 * This is effectively like mnt_want_write, except
295 * it must only be used to take an extra write reference
296 * on a mountpoint that we already know has a write reference
297 * on it. This allows some optimisation.
299 * After finished, mnt_drop_write must be called as usual to
300 * drop the reference.
302 int mnt_clone_write(struct vfsmount
*mnt
)
304 /* superblock may be r/o */
305 if (__mnt_is_readonly(mnt
))
308 inc_mnt_writers(mnt
);
312 EXPORT_SYMBOL_GPL(mnt_clone_write
);
315 * mnt_want_write_file - get write access to a file's mount
316 * @file: the file who's mount on which to take a write
318 * This is like mnt_want_write, but it takes a file and can
319 * do some optimisations if the file is open for write already
321 int mnt_want_write_file(struct file
*file
)
323 struct inode
*inode
= file
->f_dentry
->d_inode
;
324 if (!(file
->f_mode
& FMODE_WRITE
) || special_file(inode
->i_mode
))
325 return mnt_want_write(file
->f_path
.mnt
);
327 return mnt_clone_write(file
->f_path
.mnt
);
329 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
332 * mnt_drop_write - give up write access to a mount
333 * @mnt: the mount on which to give up write access
335 * Tells the low-level filesystem that we are done
336 * performing writes to it. Must be matched with
337 * mnt_want_write() call above.
339 void mnt_drop_write(struct vfsmount
*mnt
)
342 dec_mnt_writers(mnt
);
345 EXPORT_SYMBOL_GPL(mnt_drop_write
);
347 static int mnt_make_readonly(struct vfsmount
*mnt
)
351 spin_lock(&vfsmount_lock
);
352 mnt
->mnt_flags
|= MNT_WRITE_HOLD
;
354 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
355 * should be visible before we do.
360 * With writers on hold, if this value is zero, then there are
361 * definitely no active writers (although held writers may subsequently
362 * increment the count, they'll have to wait, and decrement it after
363 * seeing MNT_READONLY).
365 * It is OK to have counter incremented on one CPU and decremented on
366 * another: the sum will add up correctly. The danger would be when we
367 * sum up each counter, if we read a counter before it is incremented,
368 * but then read another CPU's count which it has been subsequently
369 * decremented from -- we would see more decrements than we should.
370 * MNT_WRITE_HOLD protects against this scenario, because
371 * mnt_want_write first increments count, then smp_mb, then spins on
372 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
373 * we're counting up here.
375 if (count_mnt_writers(mnt
) > 0)
378 mnt
->mnt_flags
|= MNT_READONLY
;
380 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
381 * that become unheld will see MNT_READONLY.
384 mnt
->mnt_flags
&= ~MNT_WRITE_HOLD
;
385 spin_unlock(&vfsmount_lock
);
389 static void __mnt_unmake_readonly(struct vfsmount
*mnt
)
391 spin_lock(&vfsmount_lock
);
392 mnt
->mnt_flags
&= ~MNT_READONLY
;
393 spin_unlock(&vfsmount_lock
);
396 void simple_set_mnt(struct vfsmount
*mnt
, struct super_block
*sb
)
399 mnt
->mnt_root
= dget(sb
->s_root
);
402 EXPORT_SYMBOL(simple_set_mnt
);
404 void free_vfsmnt(struct vfsmount
*mnt
)
406 kfree(mnt
->mnt_devname
);
409 free_percpu(mnt
->mnt_writers
);
411 kmem_cache_free(mnt_cache
, mnt
);
415 * find the first or last mount at @dentry on vfsmount @mnt depending on
416 * @dir. If @dir is set return the first mount else return the last mount.
418 struct vfsmount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
,
421 struct list_head
*head
= mount_hashtable
+ hash(mnt
, dentry
);
422 struct list_head
*tmp
= head
;
423 struct vfsmount
*p
, *found
= NULL
;
426 tmp
= dir
? tmp
->next
: tmp
->prev
;
430 p
= list_entry(tmp
, struct vfsmount
, mnt_hash
);
431 if (p
->mnt_parent
== mnt
&& p
->mnt_mountpoint
== dentry
) {
440 * lookup_mnt increments the ref count before returning
441 * the vfsmount struct.
443 struct vfsmount
*lookup_mnt(struct path
*path
)
445 struct vfsmount
*child_mnt
;
446 spin_lock(&vfsmount_lock
);
447 if ((child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
, 1)))
449 spin_unlock(&vfsmount_lock
);
453 static inline int check_mnt(struct vfsmount
*mnt
)
455 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
458 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
462 wake_up_interruptible(&ns
->poll
);
466 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
468 if (ns
&& ns
->event
!= event
) {
470 wake_up_interruptible(&ns
->poll
);
474 static void detach_mnt(struct vfsmount
*mnt
, struct path
*old_path
)
476 old_path
->dentry
= mnt
->mnt_mountpoint
;
477 old_path
->mnt
= mnt
->mnt_parent
;
478 mnt
->mnt_parent
= mnt
;
479 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
480 list_del_init(&mnt
->mnt_child
);
481 list_del_init(&mnt
->mnt_hash
);
482 old_path
->dentry
->d_mounted
--;
485 void mnt_set_mountpoint(struct vfsmount
*mnt
, struct dentry
*dentry
,
486 struct vfsmount
*child_mnt
)
488 child_mnt
->mnt_parent
= mntget(mnt
);
489 child_mnt
->mnt_mountpoint
= dget(dentry
);
493 static void attach_mnt(struct vfsmount
*mnt
, struct path
*path
)
495 mnt_set_mountpoint(path
->mnt
, path
->dentry
, mnt
);
496 list_add_tail(&mnt
->mnt_hash
, mount_hashtable
+
497 hash(path
->mnt
, path
->dentry
));
498 list_add_tail(&mnt
->mnt_child
, &path
->mnt
->mnt_mounts
);
502 * the caller must hold vfsmount_lock
504 static void commit_tree(struct vfsmount
*mnt
)
506 struct vfsmount
*parent
= mnt
->mnt_parent
;
509 struct mnt_namespace
*n
= parent
->mnt_ns
;
511 BUG_ON(parent
== mnt
);
513 list_add_tail(&head
, &mnt
->mnt_list
);
514 list_for_each_entry(m
, &head
, mnt_list
)
516 list_splice(&head
, n
->list
.prev
);
518 list_add_tail(&mnt
->mnt_hash
, mount_hashtable
+
519 hash(parent
, mnt
->mnt_mountpoint
));
520 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
521 touch_mnt_namespace(n
);
524 static struct vfsmount
*next_mnt(struct vfsmount
*p
, struct vfsmount
*root
)
526 struct list_head
*next
= p
->mnt_mounts
.next
;
527 if (next
== &p
->mnt_mounts
) {
531 next
= p
->mnt_child
.next
;
532 if (next
!= &p
->mnt_parent
->mnt_mounts
)
537 return list_entry(next
, struct vfsmount
, mnt_child
);
540 static struct vfsmount
*skip_mnt_tree(struct vfsmount
*p
)
542 struct list_head
*prev
= p
->mnt_mounts
.prev
;
543 while (prev
!= &p
->mnt_mounts
) {
544 p
= list_entry(prev
, struct vfsmount
, mnt_child
);
545 prev
= p
->mnt_mounts
.prev
;
550 static struct vfsmount
*clone_mnt(struct vfsmount
*old
, struct dentry
*root
,
553 struct super_block
*sb
= old
->mnt_sb
;
554 struct vfsmount
*mnt
= alloc_vfsmnt(old
->mnt_devname
);
557 if (flag
& (CL_SLAVE
| CL_PRIVATE
))
558 mnt
->mnt_group_id
= 0; /* not a peer of original */
560 mnt
->mnt_group_id
= old
->mnt_group_id
;
562 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
563 int err
= mnt_alloc_group_id(mnt
);
568 mnt
->mnt_flags
= old
->mnt_flags
;
569 atomic_inc(&sb
->s_active
);
571 mnt
->mnt_root
= dget(root
);
572 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
573 mnt
->mnt_parent
= mnt
;
575 if (flag
& CL_SLAVE
) {
576 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
577 mnt
->mnt_master
= old
;
578 CLEAR_MNT_SHARED(mnt
);
579 } else if (!(flag
& CL_PRIVATE
)) {
580 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
581 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
582 if (IS_MNT_SLAVE(old
))
583 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
584 mnt
->mnt_master
= old
->mnt_master
;
586 if (flag
& CL_MAKE_SHARED
)
589 /* stick the duplicate mount on the same expiry list
590 * as the original if that was on one */
591 if (flag
& CL_EXPIRE
) {
592 if (!list_empty(&old
->mnt_expire
))
593 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
603 static inline void __mntput(struct vfsmount
*mnt
)
605 struct super_block
*sb
= mnt
->mnt_sb
;
607 * This probably indicates that somebody messed
608 * up a mnt_want/drop_write() pair. If this
609 * happens, the filesystem was probably unable
610 * to make r/w->r/o transitions.
613 * atomic_dec_and_lock() used to deal with ->mnt_count decrements
614 * provides barriers, so count_mnt_writers() below is safe. AV
616 WARN_ON(count_mnt_writers(mnt
));
617 fsnotify_vfsmount_delete(mnt
);
620 deactivate_super(sb
);
623 void mntput_no_expire(struct vfsmount
*mnt
)
626 if (atomic_dec_and_lock(&mnt
->mnt_count
, &vfsmount_lock
)) {
627 if (likely(!mnt
->mnt_pinned
)) {
628 spin_unlock(&vfsmount_lock
);
632 atomic_add(mnt
->mnt_pinned
+ 1, &mnt
->mnt_count
);
634 spin_unlock(&vfsmount_lock
);
635 acct_auto_close_mnt(mnt
);
640 EXPORT_SYMBOL(mntput_no_expire
);
642 void mnt_pin(struct vfsmount
*mnt
)
644 spin_lock(&vfsmount_lock
);
646 spin_unlock(&vfsmount_lock
);
649 EXPORT_SYMBOL(mnt_pin
);
651 void mnt_unpin(struct vfsmount
*mnt
)
653 spin_lock(&vfsmount_lock
);
654 if (mnt
->mnt_pinned
) {
655 atomic_inc(&mnt
->mnt_count
);
658 spin_unlock(&vfsmount_lock
);
661 EXPORT_SYMBOL(mnt_unpin
);
663 static inline void mangle(struct seq_file
*m
, const char *s
)
665 seq_escape(m
, s
, " \t\n\\");
669 * Simple .show_options callback for filesystems which don't want to
670 * implement more complex mount option showing.
672 * See also save_mount_options().
674 int generic_show_options(struct seq_file
*m
, struct vfsmount
*mnt
)
679 options
= rcu_dereference(mnt
->mnt_sb
->s_options
);
681 if (options
!= NULL
&& options
[0]) {
689 EXPORT_SYMBOL(generic_show_options
);
692 * If filesystem uses generic_show_options(), this function should be
693 * called from the fill_super() callback.
695 * The .remount_fs callback usually needs to be handled in a special
696 * way, to make sure, that previous options are not overwritten if the
699 * Also note, that if the filesystem's .remount_fs function doesn't
700 * reset all options to their default value, but changes only newly
701 * given options, then the displayed options will not reflect reality
704 void save_mount_options(struct super_block
*sb
, char *options
)
706 BUG_ON(sb
->s_options
);
707 rcu_assign_pointer(sb
->s_options
, kstrdup(options
, GFP_KERNEL
));
709 EXPORT_SYMBOL(save_mount_options
);
711 void replace_mount_options(struct super_block
*sb
, char *options
)
713 char *old
= sb
->s_options
;
714 rcu_assign_pointer(sb
->s_options
, options
);
720 EXPORT_SYMBOL(replace_mount_options
);
722 #ifdef CONFIG_PROC_FS
724 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
726 struct proc_mounts
*p
= m
->private;
728 down_read(&namespace_sem
);
729 return seq_list_start(&p
->ns
->list
, *pos
);
732 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
734 struct proc_mounts
*p
= m
->private;
736 return seq_list_next(v
, &p
->ns
->list
, pos
);
739 static void m_stop(struct seq_file
*m
, void *v
)
741 up_read(&namespace_sem
);
744 int mnt_had_events(struct proc_mounts
*p
)
746 struct mnt_namespace
*ns
= p
->ns
;
749 spin_lock(&vfsmount_lock
);
750 if (p
->event
!= ns
->event
) {
751 p
->event
= ns
->event
;
754 spin_unlock(&vfsmount_lock
);
759 struct proc_fs_info
{
764 static int show_sb_opts(struct seq_file
*m
, struct super_block
*sb
)
766 static const struct proc_fs_info fs_info
[] = {
767 { MS_SYNCHRONOUS
, ",sync" },
768 { MS_DIRSYNC
, ",dirsync" },
769 { MS_MANDLOCK
, ",mand" },
772 const struct proc_fs_info
*fs_infop
;
774 for (fs_infop
= fs_info
; fs_infop
->flag
; fs_infop
++) {
775 if (sb
->s_flags
& fs_infop
->flag
)
776 seq_puts(m
, fs_infop
->str
);
779 return security_sb_show_options(m
, sb
);
782 static void show_mnt_opts(struct seq_file
*m
, struct vfsmount
*mnt
)
784 static const struct proc_fs_info mnt_info
[] = {
785 { MNT_NOSUID
, ",nosuid" },
786 { MNT_NODEV
, ",nodev" },
787 { MNT_NOEXEC
, ",noexec" },
788 { MNT_NOATIME
, ",noatime" },
789 { MNT_NODIRATIME
, ",nodiratime" },
790 { MNT_RELATIME
, ",relatime" },
791 { MNT_STRICTATIME
, ",strictatime" },
794 const struct proc_fs_info
*fs_infop
;
796 for (fs_infop
= mnt_info
; fs_infop
->flag
; fs_infop
++) {
797 if (mnt
->mnt_flags
& fs_infop
->flag
)
798 seq_puts(m
, fs_infop
->str
);
802 static void show_type(struct seq_file
*m
, struct super_block
*sb
)
804 mangle(m
, sb
->s_type
->name
);
805 if (sb
->s_subtype
&& sb
->s_subtype
[0]) {
807 mangle(m
, sb
->s_subtype
);
811 static int show_vfsmnt(struct seq_file
*m
, void *v
)
813 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
815 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
817 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
819 seq_path(m
, &mnt_path
, " \t\n\\");
821 show_type(m
, mnt
->mnt_sb
);
822 seq_puts(m
, __mnt_is_readonly(mnt
) ? " ro" : " rw");
823 err
= show_sb_opts(m
, mnt
->mnt_sb
);
826 show_mnt_opts(m
, mnt
);
827 if (mnt
->mnt_sb
->s_op
->show_options
)
828 err
= mnt
->mnt_sb
->s_op
->show_options(m
, mnt
);
829 seq_puts(m
, " 0 0\n");
834 const struct seq_operations mounts_op
= {
841 static int show_mountinfo(struct seq_file
*m
, void *v
)
843 struct proc_mounts
*p
= m
->private;
844 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
845 struct super_block
*sb
= mnt
->mnt_sb
;
846 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
847 struct path root
= p
->root
;
850 seq_printf(m
, "%i %i %u:%u ", mnt
->mnt_id
, mnt
->mnt_parent
->mnt_id
,
851 MAJOR(sb
->s_dev
), MINOR(sb
->s_dev
));
852 seq_dentry(m
, mnt
->mnt_root
, " \t\n\\");
854 seq_path_root(m
, &mnt_path
, &root
, " \t\n\\");
855 if (root
.mnt
!= p
->root
.mnt
|| root
.dentry
!= p
->root
.dentry
) {
857 * Mountpoint is outside root, discard that one. Ugly,
858 * but less so than trying to do that in iterator in a
859 * race-free way (due to renames).
863 seq_puts(m
, mnt
->mnt_flags
& MNT_READONLY
? " ro" : " rw");
864 show_mnt_opts(m
, mnt
);
866 /* Tagged fields ("foo:X" or "bar") */
867 if (IS_MNT_SHARED(mnt
))
868 seq_printf(m
, " shared:%i", mnt
->mnt_group_id
);
869 if (IS_MNT_SLAVE(mnt
)) {
870 int master
= mnt
->mnt_master
->mnt_group_id
;
871 int dom
= get_dominating_id(mnt
, &p
->root
);
872 seq_printf(m
, " master:%i", master
);
873 if (dom
&& dom
!= master
)
874 seq_printf(m
, " propagate_from:%i", dom
);
876 if (IS_MNT_UNBINDABLE(mnt
))
877 seq_puts(m
, " unbindable");
879 /* Filesystem specific data */
883 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
884 seq_puts(m
, sb
->s_flags
& MS_RDONLY
? " ro" : " rw");
885 err
= show_sb_opts(m
, sb
);
888 if (sb
->s_op
->show_options
)
889 err
= sb
->s_op
->show_options(m
, mnt
);
895 const struct seq_operations mountinfo_op
= {
899 .show
= show_mountinfo
,
902 static int show_vfsstat(struct seq_file
*m
, void *v
)
904 struct vfsmount
*mnt
= list_entry(v
, struct vfsmount
, mnt_list
);
905 struct path mnt_path
= { .dentry
= mnt
->mnt_root
, .mnt
= mnt
};
909 if (mnt
->mnt_devname
) {
910 seq_puts(m
, "device ");
911 mangle(m
, mnt
->mnt_devname
);
913 seq_puts(m
, "no device");
916 seq_puts(m
, " mounted on ");
917 seq_path(m
, &mnt_path
, " \t\n\\");
920 /* file system type */
921 seq_puts(m
, "with fstype ");
922 show_type(m
, mnt
->mnt_sb
);
924 /* optional statistics */
925 if (mnt
->mnt_sb
->s_op
->show_stats
) {
927 err
= mnt
->mnt_sb
->s_op
->show_stats(m
, mnt
);
934 const struct seq_operations mountstats_op
= {
938 .show
= show_vfsstat
,
940 #endif /* CONFIG_PROC_FS */
943 * may_umount_tree - check if a mount tree is busy
944 * @mnt: root of mount tree
946 * This is called to check if a tree of mounts has any
947 * open files, pwds, chroots or sub mounts that are
950 int may_umount_tree(struct vfsmount
*mnt
)
953 int minimum_refs
= 0;
956 spin_lock(&vfsmount_lock
);
957 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
958 actual_refs
+= atomic_read(&p
->mnt_count
);
961 spin_unlock(&vfsmount_lock
);
963 if (actual_refs
> minimum_refs
)
969 EXPORT_SYMBOL(may_umount_tree
);
972 * may_umount - check if a mount point is busy
973 * @mnt: root of mount
975 * This is called to check if a mount point has any
976 * open files, pwds, chroots or sub mounts. If the
977 * mount has sub mounts this will return busy
978 * regardless of whether the sub mounts are busy.
980 * Doesn't take quota and stuff into account. IOW, in some cases it will
981 * give false negatives. The main reason why it's here is that we need
982 * a non-destructive way to look for easily umountable filesystems.
984 int may_umount(struct vfsmount
*mnt
)
987 down_read(&namespace_sem
);
988 spin_lock(&vfsmount_lock
);
989 if (propagate_mount_busy(mnt
, 2))
991 spin_unlock(&vfsmount_lock
);
992 up_read(&namespace_sem
);
996 EXPORT_SYMBOL(may_umount
);
998 void release_mounts(struct list_head
*head
)
1000 struct vfsmount
*mnt
;
1001 while (!list_empty(head
)) {
1002 mnt
= list_first_entry(head
, struct vfsmount
, mnt_hash
);
1003 list_del_init(&mnt
->mnt_hash
);
1004 if (mnt
->mnt_parent
!= mnt
) {
1005 struct dentry
*dentry
;
1007 spin_lock(&vfsmount_lock
);
1008 dentry
= mnt
->mnt_mountpoint
;
1009 m
= mnt
->mnt_parent
;
1010 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
1011 mnt
->mnt_parent
= mnt
;
1013 spin_unlock(&vfsmount_lock
);
1021 void umount_tree(struct vfsmount
*mnt
, int propagate
, struct list_head
*kill
)
1025 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
1026 list_move(&p
->mnt_hash
, kill
);
1029 propagate_umount(kill
);
1031 list_for_each_entry(p
, kill
, mnt_hash
) {
1032 list_del_init(&p
->mnt_expire
);
1033 list_del_init(&p
->mnt_list
);
1034 __touch_mnt_namespace(p
->mnt_ns
);
1036 list_del_init(&p
->mnt_child
);
1037 if (p
->mnt_parent
!= p
) {
1038 p
->mnt_parent
->mnt_ghosts
++;
1039 p
->mnt_mountpoint
->d_mounted
--;
1041 change_mnt_propagation(p
, MS_PRIVATE
);
1045 static void shrink_submounts(struct vfsmount
*mnt
, struct list_head
*umounts
);
1047 static int do_umount(struct vfsmount
*mnt
, int flags
)
1049 struct super_block
*sb
= mnt
->mnt_sb
;
1051 LIST_HEAD(umount_list
);
1053 retval
= security_sb_umount(mnt
, flags
);
1058 * Allow userspace to request a mountpoint be expired rather than
1059 * unmounting unconditionally. Unmount only happens if:
1060 * (1) the mark is already set (the mark is cleared by mntput())
1061 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1063 if (flags
& MNT_EXPIRE
) {
1064 if (mnt
== current
->fs
->root
.mnt
||
1065 flags
& (MNT_FORCE
| MNT_DETACH
))
1068 if (atomic_read(&mnt
->mnt_count
) != 2)
1071 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1076 * If we may have to abort operations to get out of this
1077 * mount, and they will themselves hold resources we must
1078 * allow the fs to do things. In the Unix tradition of
1079 * 'Gee thats tricky lets do it in userspace' the umount_begin
1080 * might fail to complete on the first run through as other tasks
1081 * must return, and the like. Thats for the mount program to worry
1082 * about for the moment.
1085 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1086 sb
->s_op
->umount_begin(sb
);
1090 * No sense to grab the lock for this test, but test itself looks
1091 * somewhat bogus. Suggestions for better replacement?
1092 * Ho-hum... In principle, we might treat that as umount + switch
1093 * to rootfs. GC would eventually take care of the old vfsmount.
1094 * Actually it makes sense, especially if rootfs would contain a
1095 * /reboot - static binary that would close all descriptors and
1096 * call reboot(9). Then init(8) could umount root and exec /reboot.
1098 if (mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1100 * Special case for "unmounting" root ...
1101 * we just try to remount it readonly.
1103 down_write(&sb
->s_umount
);
1104 if (!(sb
->s_flags
& MS_RDONLY
))
1105 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
1106 up_write(&sb
->s_umount
);
1110 down_write(&namespace_sem
);
1111 spin_lock(&vfsmount_lock
);
1114 if (!(flags
& MNT_DETACH
))
1115 shrink_submounts(mnt
, &umount_list
);
1118 if (flags
& MNT_DETACH
|| !propagate_mount_busy(mnt
, 2)) {
1119 if (!list_empty(&mnt
->mnt_list
))
1120 umount_tree(mnt
, 1, &umount_list
);
1123 spin_unlock(&vfsmount_lock
);
1124 up_write(&namespace_sem
);
1125 release_mounts(&umount_list
);
1130 * Now umount can handle mount points as well as block devices.
1131 * This is important for filesystems which use unnamed block devices.
1133 * We now support a flag for forced unmount like the other 'big iron'
1134 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1137 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1141 int lookup_flags
= 0;
1143 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1146 if (!(flags
& UMOUNT_NOFOLLOW
))
1147 lookup_flags
|= LOOKUP_FOLLOW
;
1149 retval
= user_path_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1153 if (path
.dentry
!= path
.mnt
->mnt_root
)
1155 if (!check_mnt(path
.mnt
))
1159 if (!capable(CAP_SYS_ADMIN
))
1162 retval
= do_umount(path
.mnt
, flags
);
1164 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1166 mntput_no_expire(path
.mnt
);
1171 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1174 * The 2.0 compatible umount. No flags.
1176 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1178 return sys_umount(name
, 0);
1183 static int mount_is_safe(struct path
*path
)
1185 if (capable(CAP_SYS_ADMIN
))
1189 if (S_ISLNK(path
->dentry
->d_inode
->i_mode
))
1191 if (path
->dentry
->d_inode
->i_mode
& S_ISVTX
) {
1192 if (current_uid() != path
->dentry
->d_inode
->i_uid
)
1195 if (inode_permission(path
->dentry
->d_inode
, MAY_WRITE
))
1201 struct vfsmount
*copy_tree(struct vfsmount
*mnt
, struct dentry
*dentry
,
1204 struct vfsmount
*res
, *p
, *q
, *r
, *s
;
1207 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(mnt
))
1210 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1213 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1216 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1217 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1220 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1221 if (!(flag
& CL_COPY_ALL
) && IS_MNT_UNBINDABLE(s
)) {
1222 s
= skip_mnt_tree(s
);
1225 while (p
!= s
->mnt_parent
) {
1231 path
.dentry
= p
->mnt_mountpoint
;
1232 q
= clone_mnt(p
, p
->mnt_root
, flag
);
1235 spin_lock(&vfsmount_lock
);
1236 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1237 attach_mnt(q
, &path
);
1238 spin_unlock(&vfsmount_lock
);
1244 LIST_HEAD(umount_list
);
1245 spin_lock(&vfsmount_lock
);
1246 umount_tree(res
, 0, &umount_list
);
1247 spin_unlock(&vfsmount_lock
);
1248 release_mounts(&umount_list
);
1253 struct vfsmount
*collect_mounts(struct path
*path
)
1255 struct vfsmount
*tree
;
1256 down_write(&namespace_sem
);
1257 tree
= copy_tree(path
->mnt
, path
->dentry
, CL_COPY_ALL
| CL_PRIVATE
);
1258 up_write(&namespace_sem
);
1262 void drop_collected_mounts(struct vfsmount
*mnt
)
1264 LIST_HEAD(umount_list
);
1265 down_write(&namespace_sem
);
1266 spin_lock(&vfsmount_lock
);
1267 umount_tree(mnt
, 0, &umount_list
);
1268 spin_unlock(&vfsmount_lock
);
1269 up_write(&namespace_sem
);
1270 release_mounts(&umount_list
);
1273 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1274 struct vfsmount
*root
)
1276 struct vfsmount
*mnt
;
1277 int res
= f(root
, arg
);
1280 list_for_each_entry(mnt
, &root
->mnt_list
, mnt_list
) {
1288 static void cleanup_group_ids(struct vfsmount
*mnt
, struct vfsmount
*end
)
1292 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
1293 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
1294 mnt_release_group_id(p
);
1298 static int invent_group_ids(struct vfsmount
*mnt
, bool recurse
)
1302 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
1303 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
1304 int err
= mnt_alloc_group_id(p
);
1306 cleanup_group_ids(mnt
, p
);
1316 * @source_mnt : mount tree to be attached
1317 * @nd : place the mount tree @source_mnt is attached
1318 * @parent_nd : if non-null, detach the source_mnt from its parent and
1319 * store the parent mount and mountpoint dentry.
1320 * (done when source_mnt is moved)
1322 * NOTE: in the table below explains the semantics when a source mount
1323 * of a given type is attached to a destination mount of a given type.
1324 * ---------------------------------------------------------------------------
1325 * | BIND MOUNT OPERATION |
1326 * |**************************************************************************
1327 * | source-->| shared | private | slave | unbindable |
1331 * |**************************************************************************
1332 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1334 * |non-shared| shared (+) | private | slave (*) | invalid |
1335 * ***************************************************************************
1336 * A bind operation clones the source mount and mounts the clone on the
1337 * destination mount.
1339 * (++) the cloned mount is propagated to all the mounts in the propagation
1340 * tree of the destination mount and the cloned mount is added to
1341 * the peer group of the source mount.
1342 * (+) the cloned mount is created under the destination mount and is marked
1343 * as shared. The cloned mount is added to the peer group of the source
1345 * (+++) the mount is propagated to all the mounts in the propagation tree
1346 * of the destination mount and the cloned mount is made slave
1347 * of the same master as that of the source mount. The cloned mount
1348 * is marked as 'shared and slave'.
1349 * (*) the cloned mount is made a slave of the same master as that of the
1352 * ---------------------------------------------------------------------------
1353 * | MOVE MOUNT OPERATION |
1354 * |**************************************************************************
1355 * | source-->| shared | private | slave | unbindable |
1359 * |**************************************************************************
1360 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1362 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1363 * ***************************************************************************
1365 * (+) the mount is moved to the destination. And is then propagated to
1366 * all the mounts in the propagation tree of the destination mount.
1367 * (+*) the mount is moved to the destination.
1368 * (+++) the mount is moved to the destination and is then propagated to
1369 * all the mounts belonging to the destination mount's propagation tree.
1370 * the mount is marked as 'shared and slave'.
1371 * (*) the mount continues to be a slave at the new location.
1373 * if the source mount is a tree, the operations explained above is
1374 * applied to each mount in the tree.
1375 * Must be called without spinlocks held, since this function can sleep
1378 static int attach_recursive_mnt(struct vfsmount
*source_mnt
,
1379 struct path
*path
, struct path
*parent_path
)
1381 LIST_HEAD(tree_list
);
1382 struct vfsmount
*dest_mnt
= path
->mnt
;
1383 struct dentry
*dest_dentry
= path
->dentry
;
1384 struct vfsmount
*child
, *p
;
1387 if (IS_MNT_SHARED(dest_mnt
)) {
1388 err
= invent_group_ids(source_mnt
, true);
1392 err
= propagate_mnt(dest_mnt
, dest_dentry
, source_mnt
, &tree_list
);
1394 goto out_cleanup_ids
;
1396 spin_lock(&vfsmount_lock
);
1398 if (IS_MNT_SHARED(dest_mnt
)) {
1399 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
1403 detach_mnt(source_mnt
, parent_path
);
1404 attach_mnt(source_mnt
, path
);
1405 touch_mnt_namespace(parent_path
->mnt
->mnt_ns
);
1407 mnt_set_mountpoint(dest_mnt
, dest_dentry
, source_mnt
);
1408 commit_tree(source_mnt
);
1411 list_for_each_entry_safe(child
, p
, &tree_list
, mnt_hash
) {
1412 list_del_init(&child
->mnt_hash
);
1415 spin_unlock(&vfsmount_lock
);
1419 if (IS_MNT_SHARED(dest_mnt
))
1420 cleanup_group_ids(source_mnt
, NULL
);
1425 static int graft_tree(struct vfsmount
*mnt
, struct path
*path
)
1428 if (mnt
->mnt_sb
->s_flags
& MS_NOUSER
)
1431 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
1432 S_ISDIR(mnt
->mnt_root
->d_inode
->i_mode
))
1436 mutex_lock(&path
->dentry
->d_inode
->i_mutex
);
1437 if (cant_mount(path
->dentry
))
1440 if (!d_unlinked(path
->dentry
))
1441 err
= attach_recursive_mnt(mnt
, path
, NULL
);
1443 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1448 * recursively change the type of the mountpoint.
1450 static int do_change_type(struct path
*path
, int flag
)
1452 struct vfsmount
*m
, *mnt
= path
->mnt
;
1453 int recurse
= flag
& MS_REC
;
1454 int type
= flag
& ~MS_REC
;
1457 if (!capable(CAP_SYS_ADMIN
))
1460 if (path
->dentry
!= path
->mnt
->mnt_root
)
1463 down_write(&namespace_sem
);
1464 if (type
== MS_SHARED
) {
1465 err
= invent_group_ids(mnt
, recurse
);
1470 spin_lock(&vfsmount_lock
);
1471 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
1472 change_mnt_propagation(m
, type
);
1473 spin_unlock(&vfsmount_lock
);
1476 up_write(&namespace_sem
);
1481 * do loopback mount.
1483 static int do_loopback(struct path
*path
, char *old_name
,
1486 struct path old_path
;
1487 struct vfsmount
*mnt
= NULL
;
1488 int err
= mount_is_safe(path
);
1491 if (!old_name
|| !*old_name
)
1493 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
1497 down_write(&namespace_sem
);
1499 if (IS_MNT_UNBINDABLE(old_path
.mnt
))
1502 if (!check_mnt(path
->mnt
) || !check_mnt(old_path
.mnt
))
1507 mnt
= copy_tree(old_path
.mnt
, old_path
.dentry
, 0);
1509 mnt
= clone_mnt(old_path
.mnt
, old_path
.dentry
, 0);
1514 err
= graft_tree(mnt
, path
);
1516 LIST_HEAD(umount_list
);
1517 spin_lock(&vfsmount_lock
);
1518 umount_tree(mnt
, 0, &umount_list
);
1519 spin_unlock(&vfsmount_lock
);
1520 release_mounts(&umount_list
);
1524 up_write(&namespace_sem
);
1525 path_put(&old_path
);
1529 static int change_mount_flags(struct vfsmount
*mnt
, int ms_flags
)
1532 int readonly_request
= 0;
1534 if (ms_flags
& MS_RDONLY
)
1535 readonly_request
= 1;
1536 if (readonly_request
== __mnt_is_readonly(mnt
))
1539 if (readonly_request
)
1540 error
= mnt_make_readonly(mnt
);
1542 __mnt_unmake_readonly(mnt
);
1547 * change filesystem flags. dir should be a physical root of filesystem.
1548 * If you've mounted a non-root directory somewhere and want to do remount
1549 * on it - tough luck.
1551 static int do_remount(struct path
*path
, int flags
, int mnt_flags
,
1555 struct super_block
*sb
= path
->mnt
->mnt_sb
;
1557 if (!capable(CAP_SYS_ADMIN
))
1560 if (!check_mnt(path
->mnt
))
1563 if (path
->dentry
!= path
->mnt
->mnt_root
)
1566 down_write(&sb
->s_umount
);
1567 if (flags
& MS_BIND
)
1568 err
= change_mount_flags(path
->mnt
, flags
);
1570 err
= do_remount_sb(sb
, flags
, data
, 0);
1572 spin_lock(&vfsmount_lock
);
1573 mnt_flags
|= path
->mnt
->mnt_flags
& MNT_PROPAGATION_MASK
;
1574 path
->mnt
->mnt_flags
= mnt_flags
;
1575 spin_unlock(&vfsmount_lock
);
1577 up_write(&sb
->s_umount
);
1579 spin_lock(&vfsmount_lock
);
1580 touch_mnt_namespace(path
->mnt
->mnt_ns
);
1581 spin_unlock(&vfsmount_lock
);
1586 static inline int tree_contains_unbindable(struct vfsmount
*mnt
)
1589 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1590 if (IS_MNT_UNBINDABLE(p
))
1596 static int do_move_mount(struct path
*path
, char *old_name
)
1598 struct path old_path
, parent_path
;
1601 if (!capable(CAP_SYS_ADMIN
))
1603 if (!old_name
|| !*old_name
)
1605 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
1609 down_write(&namespace_sem
);
1610 while (d_mountpoint(path
->dentry
) &&
1614 if (!check_mnt(path
->mnt
) || !check_mnt(old_path
.mnt
))
1618 mutex_lock(&path
->dentry
->d_inode
->i_mutex
);
1619 if (cant_mount(path
->dentry
))
1622 if (d_unlinked(path
->dentry
))
1626 if (old_path
.dentry
!= old_path
.mnt
->mnt_root
)
1629 if (old_path
.mnt
== old_path
.mnt
->mnt_parent
)
1632 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
1633 S_ISDIR(old_path
.dentry
->d_inode
->i_mode
))
1636 * Don't move a mount residing in a shared parent.
1638 if (old_path
.mnt
->mnt_parent
&&
1639 IS_MNT_SHARED(old_path
.mnt
->mnt_parent
))
1642 * Don't move a mount tree containing unbindable mounts to a destination
1643 * mount which is shared.
1645 if (IS_MNT_SHARED(path
->mnt
) &&
1646 tree_contains_unbindable(old_path
.mnt
))
1649 for (p
= path
->mnt
; p
->mnt_parent
!= p
; p
= p
->mnt_parent
)
1650 if (p
== old_path
.mnt
)
1653 err
= attach_recursive_mnt(old_path
.mnt
, path
, &parent_path
);
1657 /* if the mount is moved, it should no longer be expire
1659 list_del_init(&old_path
.mnt
->mnt_expire
);
1661 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1663 up_write(&namespace_sem
);
1665 path_put(&parent_path
);
1666 path_put(&old_path
);
1671 * create a new mount for userspace and request it to be added into the
1674 static int do_new_mount(struct path
*path
, char *type
, int flags
,
1675 int mnt_flags
, char *name
, void *data
)
1677 struct vfsmount
*mnt
;
1682 /* we need capabilities... */
1683 if (!capable(CAP_SYS_ADMIN
))
1687 mnt
= do_kern_mount(type
, flags
, name
, data
);
1690 return PTR_ERR(mnt
);
1692 return do_add_mount(mnt
, path
, mnt_flags
, NULL
);
1696 * add a mount into a namespace's mount tree
1697 * - provide the option of adding the new mount to an expiration list
1699 int do_add_mount(struct vfsmount
*newmnt
, struct path
*path
,
1700 int mnt_flags
, struct list_head
*fslist
)
1704 mnt_flags
&= ~(MNT_SHARED
| MNT_WRITE_HOLD
| MNT_INTERNAL
);
1706 down_write(&namespace_sem
);
1707 /* Something was mounted here while we slept */
1708 while (d_mountpoint(path
->dentry
) &&
1712 if (!(mnt_flags
& MNT_SHRINKABLE
) && !check_mnt(path
->mnt
))
1715 /* Refuse the same filesystem on the same mount point */
1717 if (path
->mnt
->mnt_sb
== newmnt
->mnt_sb
&&
1718 path
->mnt
->mnt_root
== path
->dentry
)
1722 if (S_ISLNK(newmnt
->mnt_root
->d_inode
->i_mode
))
1725 newmnt
->mnt_flags
= mnt_flags
;
1726 if ((err
= graft_tree(newmnt
, path
)))
1729 if (fslist
) /* add to the specified expiration list */
1730 list_add_tail(&newmnt
->mnt_expire
, fslist
);
1732 up_write(&namespace_sem
);
1736 up_write(&namespace_sem
);
1741 EXPORT_SYMBOL_GPL(do_add_mount
);
1744 * process a list of expirable mountpoints with the intent of discarding any
1745 * mountpoints that aren't in use and haven't been touched since last we came
1748 void mark_mounts_for_expiry(struct list_head
*mounts
)
1750 struct vfsmount
*mnt
, *next
;
1751 LIST_HEAD(graveyard
);
1754 if (list_empty(mounts
))
1757 down_write(&namespace_sem
);
1758 spin_lock(&vfsmount_lock
);
1760 /* extract from the expiration list every vfsmount that matches the
1761 * following criteria:
1762 * - only referenced by its parent vfsmount
1763 * - still marked for expiry (marked on the last call here; marks are
1764 * cleared by mntput())
1766 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
1767 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
1768 propagate_mount_busy(mnt
, 1))
1770 list_move(&mnt
->mnt_expire
, &graveyard
);
1772 while (!list_empty(&graveyard
)) {
1773 mnt
= list_first_entry(&graveyard
, struct vfsmount
, mnt_expire
);
1774 touch_mnt_namespace(mnt
->mnt_ns
);
1775 umount_tree(mnt
, 1, &umounts
);
1777 spin_unlock(&vfsmount_lock
);
1778 up_write(&namespace_sem
);
1780 release_mounts(&umounts
);
1783 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
1786 * Ripoff of 'select_parent()'
1788 * search the list of submounts for a given mountpoint, and move any
1789 * shrinkable submounts to the 'graveyard' list.
1791 static int select_submounts(struct vfsmount
*parent
, struct list_head
*graveyard
)
1793 struct vfsmount
*this_parent
= parent
;
1794 struct list_head
*next
;
1798 next
= this_parent
->mnt_mounts
.next
;
1800 while (next
!= &this_parent
->mnt_mounts
) {
1801 struct list_head
*tmp
= next
;
1802 struct vfsmount
*mnt
= list_entry(tmp
, struct vfsmount
, mnt_child
);
1805 if (!(mnt
->mnt_flags
& MNT_SHRINKABLE
))
1808 * Descend a level if the d_mounts list is non-empty.
1810 if (!list_empty(&mnt
->mnt_mounts
)) {
1815 if (!propagate_mount_busy(mnt
, 1)) {
1816 list_move_tail(&mnt
->mnt_expire
, graveyard
);
1821 * All done at this level ... ascend and resume the search
1823 if (this_parent
!= parent
) {
1824 next
= this_parent
->mnt_child
.next
;
1825 this_parent
= this_parent
->mnt_parent
;
1832 * process a list of expirable mountpoints with the intent of discarding any
1833 * submounts of a specific parent mountpoint
1835 static void shrink_submounts(struct vfsmount
*mnt
, struct list_head
*umounts
)
1837 LIST_HEAD(graveyard
);
1840 /* extract submounts of 'mountpoint' from the expiration list */
1841 while (select_submounts(mnt
, &graveyard
)) {
1842 while (!list_empty(&graveyard
)) {
1843 m
= list_first_entry(&graveyard
, struct vfsmount
,
1845 touch_mnt_namespace(m
->mnt_ns
);
1846 umount_tree(m
, 1, umounts
);
1852 * Some copy_from_user() implementations do not return the exact number of
1853 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
1854 * Note that this function differs from copy_from_user() in that it will oops
1855 * on bad values of `to', rather than returning a short copy.
1857 static long exact_copy_from_user(void *to
, const void __user
* from
,
1861 const char __user
*f
= from
;
1864 if (!access_ok(VERIFY_READ
, from
, n
))
1868 if (__get_user(c
, f
)) {
1879 int copy_mount_options(const void __user
* data
, unsigned long *where
)
1889 if (!(page
= __get_free_page(GFP_KERNEL
)))
1892 /* We only care that *some* data at the address the user
1893 * gave us is valid. Just in case, we'll zero
1894 * the remainder of the page.
1896 /* copy_from_user cannot cross TASK_SIZE ! */
1897 size
= TASK_SIZE
- (unsigned long)data
;
1898 if (size
> PAGE_SIZE
)
1901 i
= size
- exact_copy_from_user((void *)page
, data
, size
);
1907 memset((char *)page
+ i
, 0, PAGE_SIZE
- i
);
1912 int copy_mount_string(const void __user
*data
, char **where
)
1921 tmp
= strndup_user(data
, PAGE_SIZE
);
1923 return PTR_ERR(tmp
);
1930 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
1931 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
1933 * data is a (void *) that can point to any structure up to
1934 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
1935 * information (or be NULL).
1937 * Pre-0.97 versions of mount() didn't have a flags word.
1938 * When the flags word was introduced its top half was required
1939 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
1940 * Therefore, if this magic number is present, it carries no information
1941 * and must be discarded.
1943 long do_mount(char *dev_name
, char *dir_name
, char *type_page
,
1944 unsigned long flags
, void *data_page
)
1951 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
1952 flags
&= ~MS_MGC_MSK
;
1954 /* Basic sanity checks */
1956 if (!dir_name
|| !*dir_name
|| !memchr(dir_name
, 0, PAGE_SIZE
))
1960 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
1962 /* ... and get the mountpoint */
1963 retval
= kern_path(dir_name
, LOOKUP_FOLLOW
, &path
);
1967 retval
= security_sb_mount(dev_name
, &path
,
1968 type_page
, flags
, data_page
);
1972 /* Default to relatime unless overriden */
1973 if (!(flags
& MS_NOATIME
))
1974 mnt_flags
|= MNT_RELATIME
;
1976 /* Separate the per-mountpoint flags */
1977 if (flags
& MS_NOSUID
)
1978 mnt_flags
|= MNT_NOSUID
;
1979 if (flags
& MS_NODEV
)
1980 mnt_flags
|= MNT_NODEV
;
1981 if (flags
& MS_NOEXEC
)
1982 mnt_flags
|= MNT_NOEXEC
;
1983 if (flags
& MS_NOATIME
)
1984 mnt_flags
|= MNT_NOATIME
;
1985 if (flags
& MS_NODIRATIME
)
1986 mnt_flags
|= MNT_NODIRATIME
;
1987 if (flags
& MS_STRICTATIME
)
1988 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
1989 if (flags
& MS_RDONLY
)
1990 mnt_flags
|= MNT_READONLY
;
1992 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
| MS_BORN
|
1993 MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
| MS_KERNMOUNT
|
1996 if (flags
& MS_REMOUNT
)
1997 retval
= do_remount(&path
, flags
& ~MS_REMOUNT
, mnt_flags
,
1999 else if (flags
& MS_BIND
)
2000 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
2001 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2002 retval
= do_change_type(&path
, flags
);
2003 else if (flags
& MS_MOVE
)
2004 retval
= do_move_mount(&path
, dev_name
);
2006 retval
= do_new_mount(&path
, type_page
, flags
, mnt_flags
,
2007 dev_name
, data_page
);
2013 static struct mnt_namespace
*alloc_mnt_ns(void)
2015 struct mnt_namespace
*new_ns
;
2017 new_ns
= kmalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
2019 return ERR_PTR(-ENOMEM
);
2020 atomic_set(&new_ns
->count
, 1);
2021 new_ns
->root
= NULL
;
2022 INIT_LIST_HEAD(&new_ns
->list
);
2023 init_waitqueue_head(&new_ns
->poll
);
2029 * Allocate a new namespace structure and populate it with contents
2030 * copied from the namespace of the passed in task structure.
2032 static struct mnt_namespace
*dup_mnt_ns(struct mnt_namespace
*mnt_ns
,
2033 struct fs_struct
*fs
)
2035 struct mnt_namespace
*new_ns
;
2036 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
2037 struct vfsmount
*p
, *q
;
2039 new_ns
= alloc_mnt_ns();
2043 down_write(&namespace_sem
);
2044 /* First pass: copy the tree topology */
2045 new_ns
->root
= copy_tree(mnt_ns
->root
, mnt_ns
->root
->mnt_root
,
2046 CL_COPY_ALL
| CL_EXPIRE
);
2047 if (!new_ns
->root
) {
2048 up_write(&namespace_sem
);
2050 return ERR_PTR(-ENOMEM
);
2052 spin_lock(&vfsmount_lock
);
2053 list_add_tail(&new_ns
->list
, &new_ns
->root
->mnt_list
);
2054 spin_unlock(&vfsmount_lock
);
2057 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2058 * as belonging to new namespace. We have already acquired a private
2059 * fs_struct, so tsk->fs->lock is not needed.
2066 if (p
== fs
->root
.mnt
) {
2068 fs
->root
.mnt
= mntget(q
);
2070 if (p
== fs
->pwd
.mnt
) {
2072 fs
->pwd
.mnt
= mntget(q
);
2075 p
= next_mnt(p
, mnt_ns
->root
);
2076 q
= next_mnt(q
, new_ns
->root
);
2078 up_write(&namespace_sem
);
2088 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
2089 struct fs_struct
*new_fs
)
2091 struct mnt_namespace
*new_ns
;
2096 if (!(flags
& CLONE_NEWNS
))
2099 new_ns
= dup_mnt_ns(ns
, new_fs
);
2106 * create_mnt_ns - creates a private namespace and adds a root filesystem
2107 * @mnt: pointer to the new root filesystem mountpoint
2109 struct mnt_namespace
*create_mnt_ns(struct vfsmount
*mnt
)
2111 struct mnt_namespace
*new_ns
;
2113 new_ns
= alloc_mnt_ns();
2114 if (!IS_ERR(new_ns
)) {
2115 mnt
->mnt_ns
= new_ns
;
2117 list_add(&new_ns
->list
, &new_ns
->root
->mnt_list
);
2121 EXPORT_SYMBOL(create_mnt_ns
);
2123 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
2124 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
2130 unsigned long data_page
;
2132 ret
= copy_mount_string(type
, &kernel_type
);
2136 kernel_dir
= getname(dir_name
);
2137 if (IS_ERR(kernel_dir
)) {
2138 ret
= PTR_ERR(kernel_dir
);
2142 ret
= copy_mount_string(dev_name
, &kernel_dev
);
2146 ret
= copy_mount_options(data
, &data_page
);
2150 ret
= do_mount(kernel_dev
, kernel_dir
, kernel_type
, flags
,
2151 (void *) data_page
);
2153 free_page(data_page
);
2157 putname(kernel_dir
);
2165 * pivot_root Semantics:
2166 * Moves the root file system of the current process to the directory put_old,
2167 * makes new_root as the new root file system of the current process, and sets
2168 * root/cwd of all processes which had them on the current root to new_root.
2171 * The new_root and put_old must be directories, and must not be on the
2172 * same file system as the current process root. The put_old must be
2173 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2174 * pointed to by put_old must yield the same directory as new_root. No other
2175 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2177 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2178 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2179 * in this situation.
2182 * - we don't move root/cwd if they are not at the root (reason: if something
2183 * cared enough to change them, it's probably wrong to force them elsewhere)
2184 * - it's okay to pick a root that isn't the root of a file system, e.g.
2185 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2186 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2189 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
2190 const char __user
*, put_old
)
2192 struct vfsmount
*tmp
;
2193 struct path
new, old
, parent_path
, root_parent
, root
;
2196 if (!capable(CAP_SYS_ADMIN
))
2199 error
= user_path_dir(new_root
, &new);
2203 if (!check_mnt(new.mnt
))
2206 error
= user_path_dir(put_old
, &old
);
2210 error
= security_sb_pivotroot(&old
, &new);
2216 read_lock(¤t
->fs
->lock
);
2217 root
= current
->fs
->root
;
2218 path_get(¤t
->fs
->root
);
2219 read_unlock(¤t
->fs
->lock
);
2220 down_write(&namespace_sem
);
2221 mutex_lock(&old
.dentry
->d_inode
->i_mutex
);
2223 if (IS_MNT_SHARED(old
.mnt
) ||
2224 IS_MNT_SHARED(new.mnt
->mnt_parent
) ||
2225 IS_MNT_SHARED(root
.mnt
->mnt_parent
))
2227 if (!check_mnt(root
.mnt
))
2230 if (cant_mount(old
.dentry
))
2232 if (d_unlinked(new.dentry
))
2234 if (d_unlinked(old
.dentry
))
2237 if (new.mnt
== root
.mnt
||
2238 old
.mnt
== root
.mnt
)
2239 goto out2
; /* loop, on the same file system */
2241 if (root
.mnt
->mnt_root
!= root
.dentry
)
2242 goto out2
; /* not a mountpoint */
2243 if (root
.mnt
->mnt_parent
== root
.mnt
)
2244 goto out2
; /* not attached */
2245 if (new.mnt
->mnt_root
!= new.dentry
)
2246 goto out2
; /* not a mountpoint */
2247 if (new.mnt
->mnt_parent
== new.mnt
)
2248 goto out2
; /* not attached */
2249 /* make sure we can reach put_old from new_root */
2251 spin_lock(&vfsmount_lock
);
2252 if (tmp
!= new.mnt
) {
2254 if (tmp
->mnt_parent
== tmp
)
2255 goto out3
; /* already mounted on put_old */
2256 if (tmp
->mnt_parent
== new.mnt
)
2258 tmp
= tmp
->mnt_parent
;
2260 if (!is_subdir(tmp
->mnt_mountpoint
, new.dentry
))
2262 } else if (!is_subdir(old
.dentry
, new.dentry
))
2264 detach_mnt(new.mnt
, &parent_path
);
2265 detach_mnt(root
.mnt
, &root_parent
);
2266 /* mount old root on put_old */
2267 attach_mnt(root
.mnt
, &old
);
2268 /* mount new_root on / */
2269 attach_mnt(new.mnt
, &root_parent
);
2270 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
2271 spin_unlock(&vfsmount_lock
);
2272 chroot_fs_refs(&root
, &new);
2274 path_put(&root_parent
);
2275 path_put(&parent_path
);
2277 mutex_unlock(&old
.dentry
->d_inode
->i_mutex
);
2278 up_write(&namespace_sem
);
2286 spin_unlock(&vfsmount_lock
);
2290 static void __init
init_mount_tree(void)
2292 struct vfsmount
*mnt
;
2293 struct mnt_namespace
*ns
;
2296 mnt
= do_kern_mount("rootfs", 0, "rootfs", NULL
);
2298 panic("Can't create rootfs");
2299 ns
= create_mnt_ns(mnt
);
2301 panic("Can't allocate initial namespace");
2303 init_task
.nsproxy
->mnt_ns
= ns
;
2306 root
.mnt
= ns
->root
;
2307 root
.dentry
= ns
->root
->mnt_root
;
2309 set_fs_pwd(current
->fs
, &root
);
2310 set_fs_root(current
->fs
, &root
);
2313 void __init
mnt_init(void)
2318 init_rwsem(&namespace_sem
);
2320 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct vfsmount
),
2321 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
2323 mount_hashtable
= (struct list_head
*)__get_free_page(GFP_ATOMIC
);
2325 if (!mount_hashtable
)
2326 panic("Failed to allocate mount hash table\n");
2328 printk("Mount-cache hash table entries: %lu\n", HASH_SIZE
);
2330 for (u
= 0; u
< HASH_SIZE
; u
++)
2331 INIT_LIST_HEAD(&mount_hashtable
[u
]);
2335 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
2337 fs_kobj
= kobject_create_and_add("fs", NULL
);
2339 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
2344 void put_mnt_ns(struct mnt_namespace
*ns
)
2346 LIST_HEAD(umount_list
);
2348 if (!atomic_dec_and_test(&ns
->count
))
2350 down_write(&namespace_sem
);
2351 spin_lock(&vfsmount_lock
);
2352 umount_tree(ns
->root
, 0, &umount_list
);
2353 spin_unlock(&vfsmount_lock
);
2354 up_write(&namespace_sem
);
2355 release_mounts(&umount_list
);
2358 EXPORT_SYMBOL(put_mnt_ns
);