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/config.h>
12 #include <linux/syscalls.h>
13 #include <linux/slab.h>
14 #include <linux/sched.h>
15 #include <linux/smp_lock.h>
16 #include <linux/init.h>
17 #include <linux/quotaops.h>
18 #include <linux/acct.h>
19 #include <linux/module.h>
20 #include <linux/seq_file.h>
21 #include <linux/namespace.h>
22 #include <linux/namei.h>
23 #include <linux/security.h>
24 #include <linux/mount.h>
25 #include <asm/uaccess.h>
26 #include <asm/unistd.h>
29 extern int __init
init_rootfs(void);
31 #define CL_EXPIRE 0x01
34 extern int __init
sysfs_init(void);
36 static inline int sysfs_init(void)
42 /* spinlock for vfsmount related operations, inplace of dcache_lock */
43 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(vfsmount_lock
);
47 static struct list_head
*mount_hashtable
;
48 static int hash_mask __read_mostly
, hash_bits __read_mostly
;
49 static kmem_cache_t
*mnt_cache
;
50 static struct rw_semaphore namespace_sem
;
52 static inline unsigned long hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
54 unsigned long tmp
= ((unsigned long)mnt
/ L1_CACHE_BYTES
);
55 tmp
+= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
56 tmp
= tmp
+ (tmp
>> hash_bits
);
57 return tmp
& hash_mask
;
60 struct vfsmount
*alloc_vfsmnt(const char *name
)
62 struct vfsmount
*mnt
= kmem_cache_alloc(mnt_cache
, GFP_KERNEL
);
64 memset(mnt
, 0, sizeof(struct vfsmount
));
65 atomic_set(&mnt
->mnt_count
, 1);
66 INIT_LIST_HEAD(&mnt
->mnt_hash
);
67 INIT_LIST_HEAD(&mnt
->mnt_child
);
68 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
69 INIT_LIST_HEAD(&mnt
->mnt_list
);
70 INIT_LIST_HEAD(&mnt
->mnt_expire
);
71 INIT_LIST_HEAD(&mnt
->mnt_share
);
73 int size
= strlen(name
) + 1;
74 char *newname
= kmalloc(size
, GFP_KERNEL
);
76 memcpy(newname
, name
, size
);
77 mnt
->mnt_devname
= newname
;
84 void free_vfsmnt(struct vfsmount
*mnt
)
86 kfree(mnt
->mnt_devname
);
87 kmem_cache_free(mnt_cache
, mnt
);
91 * Now, lookup_mnt increments the ref count before returning
92 * the vfsmount struct.
94 struct vfsmount
*lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
96 struct list_head
*head
= mount_hashtable
+ hash(mnt
, dentry
);
97 struct list_head
*tmp
= head
;
98 struct vfsmount
*p
, *found
= NULL
;
100 spin_lock(&vfsmount_lock
);
106 p
= list_entry(tmp
, struct vfsmount
, mnt_hash
);
107 if (p
->mnt_parent
== mnt
&& p
->mnt_mountpoint
== dentry
) {
112 spin_unlock(&vfsmount_lock
);
116 static inline int check_mnt(struct vfsmount
*mnt
)
118 return mnt
->mnt_namespace
== current
->namespace;
121 static void touch_namespace(struct namespace *ns
)
125 wake_up_interruptible(&ns
->poll
);
129 static void __touch_namespace(struct namespace *ns
)
131 if (ns
&& ns
->event
!= event
) {
133 wake_up_interruptible(&ns
->poll
);
137 static void detach_mnt(struct vfsmount
*mnt
, struct nameidata
*old_nd
)
139 old_nd
->dentry
= mnt
->mnt_mountpoint
;
140 old_nd
->mnt
= mnt
->mnt_parent
;
141 mnt
->mnt_parent
= mnt
;
142 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
143 list_del_init(&mnt
->mnt_child
);
144 list_del_init(&mnt
->mnt_hash
);
145 old_nd
->dentry
->d_mounted
--;
148 static void attach_mnt(struct vfsmount
*mnt
, struct nameidata
*nd
)
150 mnt
->mnt_parent
= mntget(nd
->mnt
);
151 mnt
->mnt_mountpoint
= dget(nd
->dentry
);
152 list_add(&mnt
->mnt_hash
, mount_hashtable
+ hash(nd
->mnt
, nd
->dentry
));
153 list_add_tail(&mnt
->mnt_child
, &nd
->mnt
->mnt_mounts
);
154 nd
->dentry
->d_mounted
++;
157 static struct vfsmount
*next_mnt(struct vfsmount
*p
, struct vfsmount
*root
)
159 struct list_head
*next
= p
->mnt_mounts
.next
;
160 if (next
== &p
->mnt_mounts
) {
164 next
= p
->mnt_child
.next
;
165 if (next
!= &p
->mnt_parent
->mnt_mounts
)
170 return list_entry(next
, struct vfsmount
, mnt_child
);
173 static struct vfsmount
*clone_mnt(struct vfsmount
*old
, struct dentry
*root
,
176 struct super_block
*sb
= old
->mnt_sb
;
177 struct vfsmount
*mnt
= alloc_vfsmnt(old
->mnt_devname
);
180 mnt
->mnt_flags
= old
->mnt_flags
;
181 atomic_inc(&sb
->s_active
);
183 mnt
->mnt_root
= dget(root
);
184 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
185 mnt
->mnt_parent
= mnt
;
186 mnt
->mnt_namespace
= current
->namespace;
188 /* stick the duplicate mount on the same expiry list
189 * as the original if that was on one */
190 if (flag
& CL_EXPIRE
) {
191 spin_lock(&vfsmount_lock
);
192 if (!list_empty(&old
->mnt_expire
))
193 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
194 spin_unlock(&vfsmount_lock
);
200 static inline void __mntput(struct vfsmount
*mnt
)
202 struct super_block
*sb
= mnt
->mnt_sb
;
205 deactivate_super(sb
);
208 void mntput_no_expire(struct vfsmount
*mnt
)
211 if (atomic_dec_and_lock(&mnt
->mnt_count
, &vfsmount_lock
)) {
212 if (likely(!mnt
->mnt_pinned
)) {
213 spin_unlock(&vfsmount_lock
);
217 atomic_add(mnt
->mnt_pinned
+ 1, &mnt
->mnt_count
);
219 spin_unlock(&vfsmount_lock
);
220 acct_auto_close_mnt(mnt
);
221 security_sb_umount_close(mnt
);
226 EXPORT_SYMBOL(mntput_no_expire
);
228 void mnt_pin(struct vfsmount
*mnt
)
230 spin_lock(&vfsmount_lock
);
232 spin_unlock(&vfsmount_lock
);
235 EXPORT_SYMBOL(mnt_pin
);
237 void mnt_unpin(struct vfsmount
*mnt
)
239 spin_lock(&vfsmount_lock
);
240 if (mnt
->mnt_pinned
) {
241 atomic_inc(&mnt
->mnt_count
);
244 spin_unlock(&vfsmount_lock
);
247 EXPORT_SYMBOL(mnt_unpin
);
250 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
252 struct namespace *n
= m
->private;
256 down_read(&namespace_sem
);
257 list_for_each(p
, &n
->list
)
259 return list_entry(p
, struct vfsmount
, mnt_list
);
263 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
265 struct namespace *n
= m
->private;
266 struct list_head
*p
= ((struct vfsmount
*)v
)->mnt_list
.next
;
268 return p
== &n
->list
? NULL
: list_entry(p
, struct vfsmount
, mnt_list
);
271 static void m_stop(struct seq_file
*m
, void *v
)
273 up_read(&namespace_sem
);
276 static inline void mangle(struct seq_file
*m
, const char *s
)
278 seq_escape(m
, s
, " \t\n\\");
281 static int show_vfsmnt(struct seq_file
*m
, void *v
)
283 struct vfsmount
*mnt
= v
;
285 static struct proc_fs_info
{
289 { MS_SYNCHRONOUS
, ",sync" },
290 { MS_DIRSYNC
, ",dirsync" },
291 { MS_MANDLOCK
, ",mand" },
292 { MS_NOATIME
, ",noatime" },
293 { MS_NODIRATIME
, ",nodiratime" },
296 static struct proc_fs_info mnt_info
[] = {
297 { MNT_NOSUID
, ",nosuid" },
298 { MNT_NODEV
, ",nodev" },
299 { MNT_NOEXEC
, ",noexec" },
302 struct proc_fs_info
*fs_infop
;
304 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
306 seq_path(m
, mnt
, mnt
->mnt_root
, " \t\n\\");
308 mangle(m
, mnt
->mnt_sb
->s_type
->name
);
309 seq_puts(m
, mnt
->mnt_sb
->s_flags
& MS_RDONLY
? " ro" : " rw");
310 for (fs_infop
= fs_info
; fs_infop
->flag
; fs_infop
++) {
311 if (mnt
->mnt_sb
->s_flags
& fs_infop
->flag
)
312 seq_puts(m
, fs_infop
->str
);
314 for (fs_infop
= mnt_info
; fs_infop
->flag
; fs_infop
++) {
315 if (mnt
->mnt_flags
& fs_infop
->flag
)
316 seq_puts(m
, fs_infop
->str
);
318 if (mnt
->mnt_sb
->s_op
->show_options
)
319 err
= mnt
->mnt_sb
->s_op
->show_options(m
, mnt
);
320 seq_puts(m
, " 0 0\n");
324 struct seq_operations mounts_op
= {
332 * may_umount_tree - check if a mount tree is busy
333 * @mnt: root of mount tree
335 * This is called to check if a tree of mounts has any
336 * open files, pwds, chroots or sub mounts that are
339 int may_umount_tree(struct vfsmount
*mnt
)
342 int minimum_refs
= 0;
345 spin_lock(&vfsmount_lock
);
346 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
347 actual_refs
+= atomic_read(&p
->mnt_count
);
350 spin_unlock(&vfsmount_lock
);
352 if (actual_refs
> minimum_refs
)
358 EXPORT_SYMBOL(may_umount_tree
);
361 * may_umount - check if a mount point is busy
362 * @mnt: root of mount
364 * This is called to check if a mount point has any
365 * open files, pwds, chroots or sub mounts. If the
366 * mount has sub mounts this will return busy
367 * regardless of whether the sub mounts are busy.
369 * Doesn't take quota and stuff into account. IOW, in some cases it will
370 * give false negatives. The main reason why it's here is that we need
371 * a non-destructive way to look for easily umountable filesystems.
373 int may_umount(struct vfsmount
*mnt
)
375 if (atomic_read(&mnt
->mnt_count
) > 2)
380 EXPORT_SYMBOL(may_umount
);
382 static void release_mounts(struct list_head
*head
)
384 struct vfsmount
*mnt
;
385 while(!list_empty(head
)) {
386 mnt
= list_entry(head
->next
, struct vfsmount
, mnt_hash
);
387 list_del_init(&mnt
->mnt_hash
);
388 if (mnt
->mnt_parent
!= mnt
) {
389 struct dentry
*dentry
;
391 spin_lock(&vfsmount_lock
);
392 dentry
= mnt
->mnt_mountpoint
;
394 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
395 mnt
->mnt_parent
= mnt
;
396 spin_unlock(&vfsmount_lock
);
404 static void umount_tree(struct vfsmount
*mnt
, struct list_head
*kill
)
408 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
409 list_del(&p
->mnt_hash
);
410 list_add(&p
->mnt_hash
, kill
);
413 list_for_each_entry(p
, kill
, mnt_hash
) {
414 list_del_init(&p
->mnt_expire
);
415 list_del_init(&p
->mnt_list
);
416 __touch_namespace(p
->mnt_namespace
);
417 p
->mnt_namespace
= NULL
;
418 list_del_init(&p
->mnt_child
);
419 if (p
->mnt_parent
!= p
)
420 mnt
->mnt_mountpoint
->d_mounted
--;
424 static int do_umount(struct vfsmount
*mnt
, int flags
)
426 struct super_block
*sb
= mnt
->mnt_sb
;
428 LIST_HEAD(umount_list
);
430 retval
= security_sb_umount(mnt
, flags
);
435 * Allow userspace to request a mountpoint be expired rather than
436 * unmounting unconditionally. Unmount only happens if:
437 * (1) the mark is already set (the mark is cleared by mntput())
438 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
440 if (flags
& MNT_EXPIRE
) {
441 if (mnt
== current
->fs
->rootmnt
||
442 flags
& (MNT_FORCE
| MNT_DETACH
))
445 if (atomic_read(&mnt
->mnt_count
) != 2)
448 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
453 * If we may have to abort operations to get out of this
454 * mount, and they will themselves hold resources we must
455 * allow the fs to do things. In the Unix tradition of
456 * 'Gee thats tricky lets do it in userspace' the umount_begin
457 * might fail to complete on the first run through as other tasks
458 * must return, and the like. Thats for the mount program to worry
459 * about for the moment.
463 if ((flags
& MNT_FORCE
) && sb
->s_op
->umount_begin
)
464 sb
->s_op
->umount_begin(sb
);
468 * No sense to grab the lock for this test, but test itself looks
469 * somewhat bogus. Suggestions for better replacement?
470 * Ho-hum... In principle, we might treat that as umount + switch
471 * to rootfs. GC would eventually take care of the old vfsmount.
472 * Actually it makes sense, especially if rootfs would contain a
473 * /reboot - static binary that would close all descriptors and
474 * call reboot(9). Then init(8) could umount root and exec /reboot.
476 if (mnt
== current
->fs
->rootmnt
&& !(flags
& MNT_DETACH
)) {
478 * Special case for "unmounting" root ...
479 * we just try to remount it readonly.
481 down_write(&sb
->s_umount
);
482 if (!(sb
->s_flags
& MS_RDONLY
)) {
485 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
488 up_write(&sb
->s_umount
);
492 down_write(&namespace_sem
);
493 spin_lock(&vfsmount_lock
);
497 if (atomic_read(&mnt
->mnt_count
) == 2 || flags
& MNT_DETACH
) {
498 if (!list_empty(&mnt
->mnt_list
))
499 umount_tree(mnt
, &umount_list
);
502 spin_unlock(&vfsmount_lock
);
504 security_sb_umount_busy(mnt
);
505 up_write(&namespace_sem
);
506 release_mounts(&umount_list
);
511 * Now umount can handle mount points as well as block devices.
512 * This is important for filesystems which use unnamed block devices.
514 * We now support a flag for forced unmount like the other 'big iron'
515 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
518 asmlinkage
long sys_umount(char __user
* name
, int flags
)
523 retval
= __user_walk(name
, LOOKUP_FOLLOW
, &nd
);
527 if (nd
.dentry
!= nd
.mnt
->mnt_root
)
529 if (!check_mnt(nd
.mnt
))
533 if (!capable(CAP_SYS_ADMIN
))
536 retval
= do_umount(nd
.mnt
, flags
);
538 path_release_on_umount(&nd
);
543 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
546 * The 2.0 compatible umount. No flags.
548 asmlinkage
long sys_oldumount(char __user
* name
)
550 return sys_umount(name
, 0);
555 static int mount_is_safe(struct nameidata
*nd
)
557 if (capable(CAP_SYS_ADMIN
))
561 if (S_ISLNK(nd
->dentry
->d_inode
->i_mode
))
563 if (nd
->dentry
->d_inode
->i_mode
& S_ISVTX
) {
564 if (current
->uid
!= nd
->dentry
->d_inode
->i_uid
)
567 if (permission(nd
->dentry
->d_inode
, MAY_WRITE
, nd
))
573 static int lives_below_in_same_fs(struct dentry
*d
, struct dentry
*dentry
)
578 if (d
== NULL
|| d
== d
->d_parent
)
584 static struct vfsmount
*copy_tree(struct vfsmount
*mnt
, struct dentry
*dentry
,
587 struct vfsmount
*res
, *p
, *q
, *r
, *s
;
590 res
= q
= clone_mnt(mnt
, dentry
, flag
);
593 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
596 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
597 if (!lives_below_in_same_fs(r
->mnt_mountpoint
, dentry
))
600 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
601 while (p
!= s
->mnt_parent
) {
607 nd
.dentry
= p
->mnt_mountpoint
;
608 q
= clone_mnt(p
, p
->mnt_root
, flag
);
611 spin_lock(&vfsmount_lock
);
612 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
614 spin_unlock(&vfsmount_lock
);
620 LIST_HEAD(umount_list
);
621 spin_lock(&vfsmount_lock
);
622 umount_tree(res
, &umount_list
);
623 spin_unlock(&vfsmount_lock
);
624 release_mounts(&umount_list
);
629 static int graft_tree(struct vfsmount
*mnt
, struct nameidata
*nd
)
632 if (mnt
->mnt_sb
->s_flags
& MS_NOUSER
)
635 if (S_ISDIR(nd
->dentry
->d_inode
->i_mode
) !=
636 S_ISDIR(mnt
->mnt_root
->d_inode
->i_mode
))
640 down(&nd
->dentry
->d_inode
->i_sem
);
641 if (IS_DEADDIR(nd
->dentry
->d_inode
))
644 err
= security_sb_check_sb(mnt
, nd
);
649 spin_lock(&vfsmount_lock
);
650 if (IS_ROOT(nd
->dentry
) || !d_unhashed(nd
->dentry
)) {
651 struct list_head head
;
654 list_add_tail(&head
, &mnt
->mnt_list
);
655 list_splice(&head
, current
->namespace->list
.prev
);
657 touch_namespace(current
->namespace);
659 spin_unlock(&vfsmount_lock
);
661 up(&nd
->dentry
->d_inode
->i_sem
);
663 security_sb_post_addmount(mnt
, nd
);
668 * recursively change the type of the mountpoint.
670 static int do_change_type(struct nameidata
*nd
, int flag
)
672 struct vfsmount
*m
, *mnt
= nd
->mnt
;
673 int recurse
= flag
& MS_REC
;
674 int type
= flag
& ~MS_REC
;
676 if (nd
->dentry
!= nd
->mnt
->mnt_root
)
679 down_write(&namespace_sem
);
680 spin_lock(&vfsmount_lock
);
681 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
682 change_mnt_propagation(m
, type
);
683 spin_unlock(&vfsmount_lock
);
684 up_write(&namespace_sem
);
691 static int do_loopback(struct nameidata
*nd
, char *old_name
, int recurse
)
693 struct nameidata old_nd
;
694 struct vfsmount
*mnt
= NULL
;
695 int err
= mount_is_safe(nd
);
698 if (!old_name
|| !*old_name
)
700 err
= path_lookup(old_name
, LOOKUP_FOLLOW
, &old_nd
);
704 down_write(&namespace_sem
);
706 if (!check_mnt(nd
->mnt
) || !check_mnt(old_nd
.mnt
))
711 mnt
= copy_tree(old_nd
.mnt
, old_nd
.dentry
, 0);
713 mnt
= clone_mnt(old_nd
.mnt
, old_nd
.dentry
, 0);
718 err
= graft_tree(mnt
, nd
);
720 LIST_HEAD(umount_list
);
721 spin_lock(&vfsmount_lock
);
722 umount_tree(mnt
, &umount_list
);
723 spin_unlock(&vfsmount_lock
);
724 release_mounts(&umount_list
);
728 up_write(&namespace_sem
);
729 path_release(&old_nd
);
734 * change filesystem flags. dir should be a physical root of filesystem.
735 * If you've mounted a non-root directory somewhere and want to do remount
736 * on it - tough luck.
738 static int do_remount(struct nameidata
*nd
, int flags
, int mnt_flags
,
742 struct super_block
*sb
= nd
->mnt
->mnt_sb
;
744 if (!capable(CAP_SYS_ADMIN
))
747 if (!check_mnt(nd
->mnt
))
750 if (nd
->dentry
!= nd
->mnt
->mnt_root
)
753 down_write(&sb
->s_umount
);
754 err
= do_remount_sb(sb
, flags
, data
, 0);
756 nd
->mnt
->mnt_flags
= mnt_flags
;
757 up_write(&sb
->s_umount
);
759 security_sb_post_remount(nd
->mnt
, flags
, data
);
763 static int do_move_mount(struct nameidata
*nd
, char *old_name
)
765 struct nameidata old_nd
, parent_nd
;
768 if (!capable(CAP_SYS_ADMIN
))
770 if (!old_name
|| !*old_name
)
772 err
= path_lookup(old_name
, LOOKUP_FOLLOW
, &old_nd
);
776 down_write(&namespace_sem
);
777 while (d_mountpoint(nd
->dentry
) && follow_down(&nd
->mnt
, &nd
->dentry
))
780 if (!check_mnt(nd
->mnt
) || !check_mnt(old_nd
.mnt
))
784 down(&nd
->dentry
->d_inode
->i_sem
);
785 if (IS_DEADDIR(nd
->dentry
->d_inode
))
788 spin_lock(&vfsmount_lock
);
789 if (!IS_ROOT(nd
->dentry
) && d_unhashed(nd
->dentry
))
793 if (old_nd
.dentry
!= old_nd
.mnt
->mnt_root
)
796 if (old_nd
.mnt
== old_nd
.mnt
->mnt_parent
)
799 if (S_ISDIR(nd
->dentry
->d_inode
->i_mode
) !=
800 S_ISDIR(old_nd
.dentry
->d_inode
->i_mode
))
804 for (p
= nd
->mnt
; p
->mnt_parent
!= p
; p
= p
->mnt_parent
)
809 detach_mnt(old_nd
.mnt
, &parent_nd
);
810 attach_mnt(old_nd
.mnt
, nd
);
811 touch_namespace(current
->namespace);
813 /* if the mount is moved, it should no longer be expire
815 list_del_init(&old_nd
.mnt
->mnt_expire
);
817 spin_unlock(&vfsmount_lock
);
819 up(&nd
->dentry
->d_inode
->i_sem
);
821 up_write(&namespace_sem
);
823 path_release(&parent_nd
);
824 path_release(&old_nd
);
829 * create a new mount for userspace and request it to be added into the
832 static int do_new_mount(struct nameidata
*nd
, char *type
, int flags
,
833 int mnt_flags
, char *name
, void *data
)
835 struct vfsmount
*mnt
;
837 if (!type
|| !memchr(type
, 0, PAGE_SIZE
))
840 /* we need capabilities... */
841 if (!capable(CAP_SYS_ADMIN
))
844 mnt
= do_kern_mount(type
, flags
, name
, data
);
848 return do_add_mount(mnt
, nd
, mnt_flags
, NULL
);
852 * add a mount into a namespace's mount tree
853 * - provide the option of adding the new mount to an expiration list
855 int do_add_mount(struct vfsmount
*newmnt
, struct nameidata
*nd
,
856 int mnt_flags
, struct list_head
*fslist
)
860 down_write(&namespace_sem
);
861 /* Something was mounted here while we slept */
862 while (d_mountpoint(nd
->dentry
) && follow_down(&nd
->mnt
, &nd
->dentry
))
865 if (!check_mnt(nd
->mnt
))
868 /* Refuse the same filesystem on the same mount point */
870 if (nd
->mnt
->mnt_sb
== newmnt
->mnt_sb
&&
871 nd
->mnt
->mnt_root
== nd
->dentry
)
875 if (S_ISLNK(newmnt
->mnt_root
->d_inode
->i_mode
))
878 newmnt
->mnt_flags
= mnt_flags
;
879 if ((err
= graft_tree(newmnt
, nd
)))
883 /* add to the specified expiration list */
884 spin_lock(&vfsmount_lock
);
885 list_add_tail(&newmnt
->mnt_expire
, fslist
);
886 spin_unlock(&vfsmount_lock
);
888 up_write(&namespace_sem
);
892 up_write(&namespace_sem
);
897 EXPORT_SYMBOL_GPL(do_add_mount
);
899 static void expire_mount(struct vfsmount
*mnt
, struct list_head
*mounts
,
900 struct list_head
*umounts
)
902 spin_lock(&vfsmount_lock
);
905 * Check if mount is still attached, if not, let whoever holds it deal
908 if (mnt
->mnt_parent
== mnt
) {
909 spin_unlock(&vfsmount_lock
);
914 * Check that it is still dead: the count should now be 2 - as
915 * contributed by the vfsmount parent and the mntget above
917 if (atomic_read(&mnt
->mnt_count
) == 2) {
918 /* delete from the namespace */
919 touch_namespace(mnt
->mnt_namespace
);
920 list_del_init(&mnt
->mnt_list
);
921 mnt
->mnt_namespace
= NULL
;
922 umount_tree(mnt
, umounts
);
923 spin_unlock(&vfsmount_lock
);
926 * Someone brought it back to life whilst we didn't have any
927 * locks held so return it to the expiration list
929 list_add_tail(&mnt
->mnt_expire
, mounts
);
930 spin_unlock(&vfsmount_lock
);
935 * process a list of expirable mountpoints with the intent of discarding any
936 * mountpoints that aren't in use and haven't been touched since last we came
939 void mark_mounts_for_expiry(struct list_head
*mounts
)
941 struct namespace *namespace;
942 struct vfsmount
*mnt
, *next
;
943 LIST_HEAD(graveyard
);
945 if (list_empty(mounts
))
948 spin_lock(&vfsmount_lock
);
950 /* extract from the expiration list every vfsmount that matches the
951 * following criteria:
952 * - only referenced by its parent vfsmount
953 * - still marked for expiry (marked on the last call here; marks are
954 * cleared by mntput())
956 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
957 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
958 atomic_read(&mnt
->mnt_count
) != 1)
962 list_move(&mnt
->mnt_expire
, &graveyard
);
966 * go through the vfsmounts we've just consigned to the graveyard to
967 * - check that they're still dead
968 * - delete the vfsmount from the appropriate namespace under lock
969 * - dispose of the corpse
971 while (!list_empty(&graveyard
)) {
973 mnt
= list_entry(graveyard
.next
, struct vfsmount
, mnt_expire
);
974 list_del_init(&mnt
->mnt_expire
);
976 /* don't do anything if the namespace is dead - all the
977 * vfsmounts from it are going away anyway */
978 namespace = mnt
->mnt_namespace
;
979 if (!namespace || !namespace->root
)
981 get_namespace(namespace);
983 spin_unlock(&vfsmount_lock
);
984 down_write(&namespace_sem
);
985 expire_mount(mnt
, mounts
, &umounts
);
986 up_write(&namespace_sem
);
987 release_mounts(&umounts
);
989 put_namespace(namespace);
990 spin_lock(&vfsmount_lock
);
993 spin_unlock(&vfsmount_lock
);
996 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
999 * Some copy_from_user() implementations do not return the exact number of
1000 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
1001 * Note that this function differs from copy_from_user() in that it will oops
1002 * on bad values of `to', rather than returning a short copy.
1004 static long exact_copy_from_user(void *to
, const void __user
* from
,
1008 const char __user
*f
= from
;
1011 if (!access_ok(VERIFY_READ
, from
, n
))
1015 if (__get_user(c
, f
)) {
1026 int copy_mount_options(const void __user
* data
, unsigned long *where
)
1036 if (!(page
= __get_free_page(GFP_KERNEL
)))
1039 /* We only care that *some* data at the address the user
1040 * gave us is valid. Just in case, we'll zero
1041 * the remainder of the page.
1043 /* copy_from_user cannot cross TASK_SIZE ! */
1044 size
= TASK_SIZE
- (unsigned long)data
;
1045 if (size
> PAGE_SIZE
)
1048 i
= size
- exact_copy_from_user((void *)page
, data
, size
);
1054 memset((char *)page
+ i
, 0, PAGE_SIZE
- i
);
1060 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
1061 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
1063 * data is a (void *) that can point to any structure up to
1064 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
1065 * information (or be NULL).
1067 * Pre-0.97 versions of mount() didn't have a flags word.
1068 * When the flags word was introduced its top half was required
1069 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
1070 * Therefore, if this magic number is present, it carries no information
1071 * and must be discarded.
1073 long do_mount(char *dev_name
, char *dir_name
, char *type_page
,
1074 unsigned long flags
, void *data_page
)
1076 struct nameidata nd
;
1081 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
1082 flags
&= ~MS_MGC_MSK
;
1084 /* Basic sanity checks */
1086 if (!dir_name
|| !*dir_name
|| !memchr(dir_name
, 0, PAGE_SIZE
))
1088 if (dev_name
&& !memchr(dev_name
, 0, PAGE_SIZE
))
1092 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
1094 /* Separate the per-mountpoint flags */
1095 if (flags
& MS_NOSUID
)
1096 mnt_flags
|= MNT_NOSUID
;
1097 if (flags
& MS_NODEV
)
1098 mnt_flags
|= MNT_NODEV
;
1099 if (flags
& MS_NOEXEC
)
1100 mnt_flags
|= MNT_NOEXEC
;
1101 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
);
1103 /* ... and get the mountpoint */
1104 retval
= path_lookup(dir_name
, LOOKUP_FOLLOW
, &nd
);
1108 retval
= security_sb_mount(dev_name
, &nd
, type_page
, flags
, data_page
);
1112 if (flags
& MS_REMOUNT
)
1113 retval
= do_remount(&nd
, flags
& ~MS_REMOUNT
, mnt_flags
,
1115 else if (flags
& MS_BIND
)
1116 retval
= do_loopback(&nd
, dev_name
, flags
& MS_REC
);
1117 else if (flags
& (MS_SHARED
| MS_PRIVATE
))
1118 retval
= do_change_type(&nd
, flags
);
1119 else if (flags
& MS_MOVE
)
1120 retval
= do_move_mount(&nd
, dev_name
);
1122 retval
= do_new_mount(&nd
, type_page
, flags
, mnt_flags
,
1123 dev_name
, data_page
);
1129 int copy_namespace(int flags
, struct task_struct
*tsk
)
1131 struct namespace *namespace = tsk
->namespace;
1132 struct namespace *new_ns
;
1133 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
, *altrootmnt
= NULL
;
1134 struct fs_struct
*fs
= tsk
->fs
;
1135 struct vfsmount
*p
, *q
;
1140 get_namespace(namespace);
1142 if (!(flags
& CLONE_NEWNS
))
1145 if (!capable(CAP_SYS_ADMIN
)) {
1146 put_namespace(namespace);
1150 new_ns
= kmalloc(sizeof(struct namespace), GFP_KERNEL
);
1154 atomic_set(&new_ns
->count
, 1);
1155 INIT_LIST_HEAD(&new_ns
->list
);
1156 init_waitqueue_head(&new_ns
->poll
);
1159 down_write(&namespace_sem
);
1160 /* First pass: copy the tree topology */
1161 new_ns
->root
= copy_tree(namespace->root
, namespace->root
->mnt_root
,
1163 if (!new_ns
->root
) {
1164 up_write(&namespace_sem
);
1168 spin_lock(&vfsmount_lock
);
1169 list_add_tail(&new_ns
->list
, &new_ns
->root
->mnt_list
);
1170 spin_unlock(&vfsmount_lock
);
1173 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
1174 * as belonging to new namespace. We have already acquired a private
1175 * fs_struct, so tsk->fs->lock is not needed.
1177 p
= namespace->root
;
1180 q
->mnt_namespace
= new_ns
;
1182 if (p
== fs
->rootmnt
) {
1184 fs
->rootmnt
= mntget(q
);
1186 if (p
== fs
->pwdmnt
) {
1188 fs
->pwdmnt
= mntget(q
);
1190 if (p
== fs
->altrootmnt
) {
1192 fs
->altrootmnt
= mntget(q
);
1195 p
= next_mnt(p
, namespace->root
);
1196 q
= next_mnt(q
, new_ns
->root
);
1198 up_write(&namespace_sem
);
1200 tsk
->namespace = new_ns
;
1209 put_namespace(namespace);
1213 put_namespace(namespace);
1217 asmlinkage
long sys_mount(char __user
* dev_name
, char __user
* dir_name
,
1218 char __user
* type
, unsigned long flags
,
1222 unsigned long data_page
;
1223 unsigned long type_page
;
1224 unsigned long dev_page
;
1227 retval
= copy_mount_options(type
, &type_page
);
1231 dir_page
= getname(dir_name
);
1232 retval
= PTR_ERR(dir_page
);
1233 if (IS_ERR(dir_page
))
1236 retval
= copy_mount_options(dev_name
, &dev_page
);
1240 retval
= copy_mount_options(data
, &data_page
);
1245 retval
= do_mount((char *)dev_page
, dir_page
, (char *)type_page
,
1246 flags
, (void *)data_page
);
1248 free_page(data_page
);
1251 free_page(dev_page
);
1255 free_page(type_page
);
1260 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
1261 * It can block. Requires the big lock held.
1263 void set_fs_root(struct fs_struct
*fs
, struct vfsmount
*mnt
,
1264 struct dentry
*dentry
)
1266 struct dentry
*old_root
;
1267 struct vfsmount
*old_rootmnt
;
1268 write_lock(&fs
->lock
);
1269 old_root
= fs
->root
;
1270 old_rootmnt
= fs
->rootmnt
;
1271 fs
->rootmnt
= mntget(mnt
);
1272 fs
->root
= dget(dentry
);
1273 write_unlock(&fs
->lock
);
1276 mntput(old_rootmnt
);
1281 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
1282 * It can block. Requires the big lock held.
1284 void set_fs_pwd(struct fs_struct
*fs
, struct vfsmount
*mnt
,
1285 struct dentry
*dentry
)
1287 struct dentry
*old_pwd
;
1288 struct vfsmount
*old_pwdmnt
;
1290 write_lock(&fs
->lock
);
1292 old_pwdmnt
= fs
->pwdmnt
;
1293 fs
->pwdmnt
= mntget(mnt
);
1294 fs
->pwd
= dget(dentry
);
1295 write_unlock(&fs
->lock
);
1303 static void chroot_fs_refs(struct nameidata
*old_nd
, struct nameidata
*new_nd
)
1305 struct task_struct
*g
, *p
;
1306 struct fs_struct
*fs
;
1308 read_lock(&tasklist_lock
);
1309 do_each_thread(g
, p
) {
1313 atomic_inc(&fs
->count
);
1315 if (fs
->root
== old_nd
->dentry
1316 && fs
->rootmnt
== old_nd
->mnt
)
1317 set_fs_root(fs
, new_nd
->mnt
, new_nd
->dentry
);
1318 if (fs
->pwd
== old_nd
->dentry
1319 && fs
->pwdmnt
== old_nd
->mnt
)
1320 set_fs_pwd(fs
, new_nd
->mnt
, new_nd
->dentry
);
1324 } while_each_thread(g
, p
);
1325 read_unlock(&tasklist_lock
);
1329 * pivot_root Semantics:
1330 * Moves the root file system of the current process to the directory put_old,
1331 * makes new_root as the new root file system of the current process, and sets
1332 * root/cwd of all processes which had them on the current root to new_root.
1335 * The new_root and put_old must be directories, and must not be on the
1336 * same file system as the current process root. The put_old must be
1337 * underneath new_root, i.e. adding a non-zero number of /.. to the string
1338 * pointed to by put_old must yield the same directory as new_root. No other
1339 * file system may be mounted on put_old. After all, new_root is a mountpoint.
1342 * - we don't move root/cwd if they are not at the root (reason: if something
1343 * cared enough to change them, it's probably wrong to force them elsewhere)
1344 * - it's okay to pick a root that isn't the root of a file system, e.g.
1345 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
1346 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
1349 asmlinkage
long sys_pivot_root(const char __user
* new_root
,
1350 const char __user
* put_old
)
1352 struct vfsmount
*tmp
;
1353 struct nameidata new_nd
, old_nd
, parent_nd
, root_parent
, user_nd
;
1356 if (!capable(CAP_SYS_ADMIN
))
1361 error
= __user_walk(new_root
, LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
,
1366 if (!check_mnt(new_nd
.mnt
))
1369 error
= __user_walk(put_old
, LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
, &old_nd
);
1373 error
= security_sb_pivotroot(&old_nd
, &new_nd
);
1375 path_release(&old_nd
);
1379 read_lock(¤t
->fs
->lock
);
1380 user_nd
.mnt
= mntget(current
->fs
->rootmnt
);
1381 user_nd
.dentry
= dget(current
->fs
->root
);
1382 read_unlock(¤t
->fs
->lock
);
1383 down_write(&namespace_sem
);
1384 down(&old_nd
.dentry
->d_inode
->i_sem
);
1386 if (!check_mnt(user_nd
.mnt
))
1389 if (IS_DEADDIR(new_nd
.dentry
->d_inode
))
1391 if (d_unhashed(new_nd
.dentry
) && !IS_ROOT(new_nd
.dentry
))
1393 if (d_unhashed(old_nd
.dentry
) && !IS_ROOT(old_nd
.dentry
))
1396 if (new_nd
.mnt
== user_nd
.mnt
|| old_nd
.mnt
== user_nd
.mnt
)
1397 goto out2
; /* loop, on the same file system */
1399 if (user_nd
.mnt
->mnt_root
!= user_nd
.dentry
)
1400 goto out2
; /* not a mountpoint */
1401 if (user_nd
.mnt
->mnt_parent
== user_nd
.mnt
)
1402 goto out2
; /* not attached */
1403 if (new_nd
.mnt
->mnt_root
!= new_nd
.dentry
)
1404 goto out2
; /* not a mountpoint */
1405 if (new_nd
.mnt
->mnt_parent
== new_nd
.mnt
)
1406 goto out2
; /* not attached */
1407 tmp
= old_nd
.mnt
; /* make sure we can reach put_old from new_root */
1408 spin_lock(&vfsmount_lock
);
1409 if (tmp
!= new_nd
.mnt
) {
1411 if (tmp
->mnt_parent
== tmp
)
1412 goto out3
; /* already mounted on put_old */
1413 if (tmp
->mnt_parent
== new_nd
.mnt
)
1415 tmp
= tmp
->mnt_parent
;
1417 if (!is_subdir(tmp
->mnt_mountpoint
, new_nd
.dentry
))
1419 } else if (!is_subdir(old_nd
.dentry
, new_nd
.dentry
))
1421 detach_mnt(new_nd
.mnt
, &parent_nd
);
1422 detach_mnt(user_nd
.mnt
, &root_parent
);
1423 attach_mnt(user_nd
.mnt
, &old_nd
); /* mount old root on put_old */
1424 attach_mnt(new_nd
.mnt
, &root_parent
); /* mount new_root on / */
1425 touch_namespace(current
->namespace);
1426 spin_unlock(&vfsmount_lock
);
1427 chroot_fs_refs(&user_nd
, &new_nd
);
1428 security_sb_post_pivotroot(&user_nd
, &new_nd
);
1430 path_release(&root_parent
);
1431 path_release(&parent_nd
);
1433 up(&old_nd
.dentry
->d_inode
->i_sem
);
1434 up_write(&namespace_sem
);
1435 path_release(&user_nd
);
1436 path_release(&old_nd
);
1438 path_release(&new_nd
);
1443 spin_unlock(&vfsmount_lock
);
1447 static void __init
init_mount_tree(void)
1449 struct vfsmount
*mnt
;
1450 struct namespace *namespace;
1451 struct task_struct
*g
, *p
;
1453 mnt
= do_kern_mount("rootfs", 0, "rootfs", NULL
);
1455 panic("Can't create rootfs");
1456 namespace = kmalloc(sizeof(*namespace), GFP_KERNEL
);
1458 panic("Can't allocate initial namespace");
1459 atomic_set(&namespace->count
, 1);
1460 INIT_LIST_HEAD(&namespace->list
);
1461 init_waitqueue_head(&namespace->poll
);
1462 namespace->event
= 0;
1463 list_add(&mnt
->mnt_list
, &namespace->list
);
1464 namespace->root
= mnt
;
1465 mnt
->mnt_namespace
= namespace;
1467 init_task
.namespace = namespace;
1468 read_lock(&tasklist_lock
);
1469 do_each_thread(g
, p
) {
1470 get_namespace(namespace);
1471 p
->namespace = namespace;
1472 } while_each_thread(g
, p
);
1473 read_unlock(&tasklist_lock
);
1475 set_fs_pwd(current
->fs
, namespace->root
, namespace->root
->mnt_root
);
1476 set_fs_root(current
->fs
, namespace->root
, namespace->root
->mnt_root
);
1479 void __init
mnt_init(unsigned long mempages
)
1481 struct list_head
*d
;
1482 unsigned int nr_hash
;
1485 init_rwsem(&namespace_sem
);
1487 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct vfsmount
),
1488 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
, NULL
);
1490 mount_hashtable
= (struct list_head
*)__get_free_page(GFP_ATOMIC
);
1492 if (!mount_hashtable
)
1493 panic("Failed to allocate mount hash table\n");
1496 * Find the power-of-two list-heads that can fit into the allocation..
1497 * We don't guarantee that "sizeof(struct list_head)" is necessarily
1500 nr_hash
= PAGE_SIZE
/ sizeof(struct list_head
);
1504 } while ((nr_hash
>> hash_bits
) != 0);
1508 * Re-calculate the actual number of entries and the mask
1509 * from the number of bits we can fit.
1511 nr_hash
= 1UL << hash_bits
;
1512 hash_mask
= nr_hash
- 1;
1514 printk("Mount-cache hash table entries: %d\n", nr_hash
);
1516 /* And initialize the newly allocated array */
1517 d
= mount_hashtable
;
1529 void __put_namespace(struct namespace *namespace)
1531 struct vfsmount
*root
= namespace->root
;
1532 LIST_HEAD(umount_list
);
1533 namespace->root
= NULL
;
1534 spin_unlock(&vfsmount_lock
);
1535 down_write(&namespace_sem
);
1536 spin_lock(&vfsmount_lock
);
1537 umount_tree(root
, &umount_list
);
1538 spin_unlock(&vfsmount_lock
);
1539 up_write(&namespace_sem
);
1540 release_mounts(&umount_list
);