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>
28 extern int __init
init_rootfs(void);
31 extern int __init
sysfs_init(void);
33 static inline int sysfs_init(void)
39 /* spinlock for vfsmount related operations, inplace of dcache_lock */
40 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(vfsmount_lock
);
44 static struct list_head
*mount_hashtable
;
45 static int hash_mask __read_mostly
, hash_bits __read_mostly
;
46 static kmem_cache_t
*mnt_cache
;
48 static inline unsigned long hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
50 unsigned long tmp
= ((unsigned long) mnt
/ L1_CACHE_BYTES
);
51 tmp
+= ((unsigned long) dentry
/ L1_CACHE_BYTES
);
52 tmp
= tmp
+ (tmp
>> hash_bits
);
53 return tmp
& hash_mask
;
56 struct vfsmount
*alloc_vfsmnt(const char *name
)
58 struct vfsmount
*mnt
= kmem_cache_alloc(mnt_cache
, GFP_KERNEL
);
60 memset(mnt
, 0, sizeof(struct vfsmount
));
61 atomic_set(&mnt
->mnt_count
,1);
62 INIT_LIST_HEAD(&mnt
->mnt_hash
);
63 INIT_LIST_HEAD(&mnt
->mnt_child
);
64 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
65 INIT_LIST_HEAD(&mnt
->mnt_list
);
66 INIT_LIST_HEAD(&mnt
->mnt_expire
);
68 int size
= strlen(name
)+1;
69 char *newname
= kmalloc(size
, GFP_KERNEL
);
71 memcpy(newname
, name
, size
);
72 mnt
->mnt_devname
= newname
;
79 void free_vfsmnt(struct vfsmount
*mnt
)
81 kfree(mnt
->mnt_devname
);
82 kmem_cache_free(mnt_cache
, mnt
);
86 * Now, lookup_mnt increments the ref count before returning
87 * the vfsmount struct.
89 struct vfsmount
*lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
91 struct list_head
* head
= mount_hashtable
+ hash(mnt
, dentry
);
92 struct list_head
* tmp
= head
;
93 struct vfsmount
*p
, *found
= NULL
;
95 spin_lock(&vfsmount_lock
);
101 p
= list_entry(tmp
, struct vfsmount
, mnt_hash
);
102 if (p
->mnt_parent
== mnt
&& p
->mnt_mountpoint
== dentry
) {
107 spin_unlock(&vfsmount_lock
);
111 static inline int check_mnt(struct vfsmount
*mnt
)
113 return mnt
->mnt_namespace
== current
->namespace;
116 static void touch_namespace(struct namespace *ns
)
120 wake_up_interruptible(&ns
->poll
);
124 static void __touch_namespace(struct namespace *ns
)
126 if (ns
&& ns
->event
!= event
) {
128 wake_up_interruptible(&ns
->poll
);
132 static void detach_mnt(struct vfsmount
*mnt
, struct nameidata
*old_nd
)
134 old_nd
->dentry
= mnt
->mnt_mountpoint
;
135 old_nd
->mnt
= mnt
->mnt_parent
;
136 mnt
->mnt_parent
= mnt
;
137 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
138 list_del_init(&mnt
->mnt_child
);
139 list_del_init(&mnt
->mnt_hash
);
140 old_nd
->dentry
->d_mounted
--;
143 static void attach_mnt(struct vfsmount
*mnt
, struct nameidata
*nd
)
145 mnt
->mnt_parent
= mntget(nd
->mnt
);
146 mnt
->mnt_mountpoint
= dget(nd
->dentry
);
147 list_add(&mnt
->mnt_hash
, mount_hashtable
+hash(nd
->mnt
, nd
->dentry
));
148 list_add_tail(&mnt
->mnt_child
, &nd
->mnt
->mnt_mounts
);
149 nd
->dentry
->d_mounted
++;
152 static struct vfsmount
*next_mnt(struct vfsmount
*p
, struct vfsmount
*root
)
154 struct list_head
*next
= p
->mnt_mounts
.next
;
155 if (next
== &p
->mnt_mounts
) {
159 next
= p
->mnt_child
.next
;
160 if (next
!= &p
->mnt_parent
->mnt_mounts
)
165 return list_entry(next
, struct vfsmount
, mnt_child
);
168 static struct vfsmount
*
169 clone_mnt(struct vfsmount
*old
, struct dentry
*root
)
171 struct super_block
*sb
= old
->mnt_sb
;
172 struct vfsmount
*mnt
= alloc_vfsmnt(old
->mnt_devname
);
175 mnt
->mnt_flags
= old
->mnt_flags
;
176 atomic_inc(&sb
->s_active
);
178 mnt
->mnt_root
= dget(root
);
179 mnt
->mnt_mountpoint
= mnt
->mnt_root
;
180 mnt
->mnt_parent
= mnt
;
181 mnt
->mnt_namespace
= current
->namespace;
183 /* stick the duplicate mount on the same expiry list
184 * as the original if that was on one */
185 spin_lock(&vfsmount_lock
);
186 if (!list_empty(&old
->mnt_expire
))
187 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
188 spin_unlock(&vfsmount_lock
);
193 static inline void __mntput(struct vfsmount
*mnt
)
195 struct super_block
*sb
= mnt
->mnt_sb
;
198 deactivate_super(sb
);
201 void mntput_no_expire(struct vfsmount
*mnt
)
204 if (atomic_dec_and_lock(&mnt
->mnt_count
, &vfsmount_lock
)) {
205 if (likely(!mnt
->mnt_pinned
)) {
206 spin_unlock(&vfsmount_lock
);
210 atomic_add(mnt
->mnt_pinned
+ 1, &mnt
->mnt_count
);
212 spin_unlock(&vfsmount_lock
);
213 acct_auto_close_mnt(mnt
);
214 security_sb_umount_close(mnt
);
219 EXPORT_SYMBOL(mntput_no_expire
);
221 void mnt_pin(struct vfsmount
*mnt
)
223 spin_lock(&vfsmount_lock
);
225 spin_unlock(&vfsmount_lock
);
228 EXPORT_SYMBOL(mnt_pin
);
230 void mnt_unpin(struct vfsmount
*mnt
)
232 spin_lock(&vfsmount_lock
);
233 if (mnt
->mnt_pinned
) {
234 atomic_inc(&mnt
->mnt_count
);
237 spin_unlock(&vfsmount_lock
);
240 EXPORT_SYMBOL(mnt_unpin
);
243 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
245 struct namespace *n
= m
->private;
250 list_for_each(p
, &n
->list
)
252 return list_entry(p
, struct vfsmount
, mnt_list
);
256 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
258 struct namespace *n
= m
->private;
259 struct list_head
*p
= ((struct vfsmount
*)v
)->mnt_list
.next
;
261 return p
==&n
->list
? NULL
: list_entry(p
, struct vfsmount
, mnt_list
);
264 static void m_stop(struct seq_file
*m
, void *v
)
266 struct namespace *n
= m
->private;
270 static inline void mangle(struct seq_file
*m
, const char *s
)
272 seq_escape(m
, s
, " \t\n\\");
275 static int show_vfsmnt(struct seq_file
*m
, void *v
)
277 struct vfsmount
*mnt
= v
;
279 static struct proc_fs_info
{
283 { MS_SYNCHRONOUS
, ",sync" },
284 { MS_DIRSYNC
, ",dirsync" },
285 { MS_MANDLOCK
, ",mand" },
286 { MS_NOATIME
, ",noatime" },
287 { MS_NODIRATIME
, ",nodiratime" },
290 static struct proc_fs_info mnt_info
[] = {
291 { MNT_NOSUID
, ",nosuid" },
292 { MNT_NODEV
, ",nodev" },
293 { MNT_NOEXEC
, ",noexec" },
296 struct proc_fs_info
*fs_infop
;
298 mangle(m
, mnt
->mnt_devname
? mnt
->mnt_devname
: "none");
300 seq_path(m
, mnt
, mnt
->mnt_root
, " \t\n\\");
302 mangle(m
, mnt
->mnt_sb
->s_type
->name
);
303 seq_puts(m
, mnt
->mnt_sb
->s_flags
& MS_RDONLY
? " ro" : " rw");
304 for (fs_infop
= fs_info
; fs_infop
->flag
; fs_infop
++) {
305 if (mnt
->mnt_sb
->s_flags
& fs_infop
->flag
)
306 seq_puts(m
, fs_infop
->str
);
308 for (fs_infop
= mnt_info
; fs_infop
->flag
; fs_infop
++) {
309 if (mnt
->mnt_flags
& fs_infop
->flag
)
310 seq_puts(m
, fs_infop
->str
);
312 if (mnt
->mnt_sb
->s_op
->show_options
)
313 err
= mnt
->mnt_sb
->s_op
->show_options(m
, mnt
);
314 seq_puts(m
, " 0 0\n");
318 struct seq_operations mounts_op
= {
326 * may_umount_tree - check if a mount tree is busy
327 * @mnt: root of mount tree
329 * This is called to check if a tree of mounts has any
330 * open files, pwds, chroots or sub mounts that are
333 int may_umount_tree(struct vfsmount
*mnt
)
335 struct list_head
*next
;
336 struct vfsmount
*this_parent
= mnt
;
340 spin_lock(&vfsmount_lock
);
341 actual_refs
= atomic_read(&mnt
->mnt_count
);
344 next
= this_parent
->mnt_mounts
.next
;
346 while (next
!= &this_parent
->mnt_mounts
) {
347 struct vfsmount
*p
= list_entry(next
, struct vfsmount
, mnt_child
);
351 actual_refs
+= atomic_read(&p
->mnt_count
);
354 if (!list_empty(&p
->mnt_mounts
)) {
360 if (this_parent
!= mnt
) {
361 next
= this_parent
->mnt_child
.next
;
362 this_parent
= this_parent
->mnt_parent
;
365 spin_unlock(&vfsmount_lock
);
367 if (actual_refs
> minimum_refs
)
373 EXPORT_SYMBOL(may_umount_tree
);
376 * may_umount - check if a mount point is busy
377 * @mnt: root of mount
379 * This is called to check if a mount point has any
380 * open files, pwds, chroots or sub mounts. If the
381 * mount has sub mounts this will return busy
382 * regardless of whether the sub mounts are busy.
384 * Doesn't take quota and stuff into account. IOW, in some cases it will
385 * give false negatives. The main reason why it's here is that we need
386 * a non-destructive way to look for easily umountable filesystems.
388 int may_umount(struct vfsmount
*mnt
)
390 if (atomic_read(&mnt
->mnt_count
) > 2)
395 EXPORT_SYMBOL(may_umount
);
397 static void umount_tree(struct vfsmount
*mnt
)
402 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
403 list_del(&p
->mnt_list
);
404 list_add(&p
->mnt_list
, &kill
);
405 __touch_namespace(p
->mnt_namespace
);
406 p
->mnt_namespace
= NULL
;
409 while (!list_empty(&kill
)) {
410 mnt
= list_entry(kill
.next
, struct vfsmount
, mnt_list
);
411 list_del_init(&mnt
->mnt_list
);
412 list_del_init(&mnt
->mnt_expire
);
413 if (mnt
->mnt_parent
== mnt
) {
414 spin_unlock(&vfsmount_lock
);
416 struct nameidata old_nd
;
417 detach_mnt(mnt
, &old_nd
);
418 spin_unlock(&vfsmount_lock
);
419 path_release(&old_nd
);
422 spin_lock(&vfsmount_lock
);
426 static int do_umount(struct vfsmount
*mnt
, int flags
)
428 struct super_block
* sb
= mnt
->mnt_sb
;
431 retval
= security_sb_umount(mnt
, flags
);
436 * Allow userspace to request a mountpoint be expired rather than
437 * unmounting unconditionally. Unmount only happens if:
438 * (1) the mark is already set (the mark is cleared by mntput())
439 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
441 if (flags
& MNT_EXPIRE
) {
442 if (mnt
== current
->fs
->rootmnt
||
443 flags
& (MNT_FORCE
| MNT_DETACH
))
446 if (atomic_read(&mnt
->mnt_count
) != 2)
449 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
454 * If we may have to abort operations to get out of this
455 * mount, and they will themselves hold resources we must
456 * allow the fs to do things. In the Unix tradition of
457 * 'Gee thats tricky lets do it in userspace' the umount_begin
458 * might fail to complete on the first run through as other tasks
459 * must return, and the like. Thats for the mount program to worry
460 * about for the moment.
464 if( (flags
&MNT_FORCE
) && sb
->s_op
->umount_begin
)
465 sb
->s_op
->umount_begin(sb
);
469 * No sense to grab the lock for this test, but test itself looks
470 * somewhat bogus. Suggestions for better replacement?
471 * Ho-hum... In principle, we might treat that as umount + switch
472 * to rootfs. GC would eventually take care of the old vfsmount.
473 * Actually it makes sense, especially if rootfs would contain a
474 * /reboot - static binary that would close all descriptors and
475 * call reboot(9). Then init(8) could umount root and exec /reboot.
477 if (mnt
== current
->fs
->rootmnt
&& !(flags
& MNT_DETACH
)) {
479 * Special case for "unmounting" root ...
480 * we just try to remount it readonly.
482 down_write(&sb
->s_umount
);
483 if (!(sb
->s_flags
& MS_RDONLY
)) {
486 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
489 up_write(&sb
->s_umount
);
493 down_write(¤t
->namespace->sem
);
494 spin_lock(&vfsmount_lock
);
498 if (atomic_read(&mnt
->mnt_count
) == 2 || flags
& MNT_DETACH
) {
499 if (!list_empty(&mnt
->mnt_list
))
503 spin_unlock(&vfsmount_lock
);
505 security_sb_umount_busy(mnt
);
506 up_write(¤t
->namespace->sem
);
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.
549 asmlinkage
long sys_oldumount(char __user
* name
)
551 return sys_umount(name
,0);
556 static int mount_is_safe(struct nameidata
*nd
)
558 if (capable(CAP_SYS_ADMIN
))
562 if (S_ISLNK(nd
->dentry
->d_inode
->i_mode
))
564 if (nd
->dentry
->d_inode
->i_mode
& S_ISVTX
) {
565 if (current
->uid
!= nd
->dentry
->d_inode
->i_uid
)
568 if (permission(nd
->dentry
->d_inode
, MAY_WRITE
, nd
))
575 lives_below_in_same_fs(struct dentry
*d
, struct dentry
*dentry
)
580 if (d
== NULL
|| d
== d
->d_parent
)
586 static struct vfsmount
*copy_tree(struct vfsmount
*mnt
, struct dentry
*dentry
)
588 struct vfsmount
*res
, *p
, *q
, *r
, *s
;
591 res
= q
= clone_mnt(mnt
, dentry
);
594 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
597 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
598 if (!lives_below_in_same_fs(r
->mnt_mountpoint
, dentry
))
601 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
602 while (p
!= s
->mnt_parent
) {
608 nd
.dentry
= p
->mnt_mountpoint
;
609 q
= clone_mnt(p
, p
->mnt_root
);
612 spin_lock(&vfsmount_lock
);
613 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
615 spin_unlock(&vfsmount_lock
);
621 spin_lock(&vfsmount_lock
);
623 spin_unlock(&vfsmount_lock
);
628 static int graft_tree(struct vfsmount
*mnt
, struct nameidata
*nd
)
631 if (mnt
->mnt_sb
->s_flags
& MS_NOUSER
)
634 if (S_ISDIR(nd
->dentry
->d_inode
->i_mode
) !=
635 S_ISDIR(mnt
->mnt_root
->d_inode
->i_mode
))
639 down(&nd
->dentry
->d_inode
->i_sem
);
640 if (IS_DEADDIR(nd
->dentry
->d_inode
))
643 err
= security_sb_check_sb(mnt
, nd
);
648 spin_lock(&vfsmount_lock
);
649 if (IS_ROOT(nd
->dentry
) || !d_unhashed(nd
->dentry
)) {
650 struct list_head head
;
653 list_add_tail(&head
, &mnt
->mnt_list
);
654 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
);
670 static int do_loopback(struct nameidata
*nd
, char *old_name
, int recurse
)
672 struct nameidata old_nd
;
673 struct vfsmount
*mnt
= NULL
;
674 int err
= mount_is_safe(nd
);
677 if (!old_name
|| !*old_name
)
679 err
= path_lookup(old_name
, LOOKUP_FOLLOW
, &old_nd
);
683 down_write(¤t
->namespace->sem
);
685 if (!check_mnt(nd
->mnt
) || !check_mnt(old_nd
.mnt
))
690 mnt
= copy_tree(old_nd
.mnt
, old_nd
.dentry
);
692 mnt
= clone_mnt(old_nd
.mnt
, old_nd
.dentry
);
697 /* stop bind mounts from expiring */
698 spin_lock(&vfsmount_lock
);
699 list_del_init(&mnt
->mnt_expire
);
700 spin_unlock(&vfsmount_lock
);
702 err
= graft_tree(mnt
, nd
);
704 spin_lock(&vfsmount_lock
);
706 spin_unlock(&vfsmount_lock
);
711 up_write(¤t
->namespace->sem
);
712 path_release(&old_nd
);
717 * change filesystem flags. dir should be a physical root of filesystem.
718 * If you've mounted a non-root directory somewhere and want to do remount
719 * on it - tough luck.
722 static int do_remount(struct nameidata
*nd
, int flags
, int mnt_flags
,
726 struct super_block
* sb
= nd
->mnt
->mnt_sb
;
728 if (!capable(CAP_SYS_ADMIN
))
731 if (!check_mnt(nd
->mnt
))
734 if (nd
->dentry
!= nd
->mnt
->mnt_root
)
737 down_write(&sb
->s_umount
);
738 err
= do_remount_sb(sb
, flags
, data
, 0);
740 nd
->mnt
->mnt_flags
=mnt_flags
;
741 up_write(&sb
->s_umount
);
743 security_sb_post_remount(nd
->mnt
, flags
, data
);
747 static int do_move_mount(struct nameidata
*nd
, char *old_name
)
749 struct nameidata old_nd
, parent_nd
;
752 if (!capable(CAP_SYS_ADMIN
))
754 if (!old_name
|| !*old_name
)
756 err
= path_lookup(old_name
, LOOKUP_FOLLOW
, &old_nd
);
760 down_write(¤t
->namespace->sem
);
761 while(d_mountpoint(nd
->dentry
) && follow_down(&nd
->mnt
, &nd
->dentry
))
764 if (!check_mnt(nd
->mnt
) || !check_mnt(old_nd
.mnt
))
768 down(&nd
->dentry
->d_inode
->i_sem
);
769 if (IS_DEADDIR(nd
->dentry
->d_inode
))
772 spin_lock(&vfsmount_lock
);
773 if (!IS_ROOT(nd
->dentry
) && d_unhashed(nd
->dentry
))
777 if (old_nd
.dentry
!= old_nd
.mnt
->mnt_root
)
780 if (old_nd
.mnt
== old_nd
.mnt
->mnt_parent
)
783 if (S_ISDIR(nd
->dentry
->d_inode
->i_mode
) !=
784 S_ISDIR(old_nd
.dentry
->d_inode
->i_mode
))
788 for (p
= nd
->mnt
; p
->mnt_parent
!=p
; p
= p
->mnt_parent
)
793 detach_mnt(old_nd
.mnt
, &parent_nd
);
794 attach_mnt(old_nd
.mnt
, nd
);
795 touch_namespace(current
->namespace);
797 /* if the mount is moved, it should no longer be expire
799 list_del_init(&old_nd
.mnt
->mnt_expire
);
801 spin_unlock(&vfsmount_lock
);
803 up(&nd
->dentry
->d_inode
->i_sem
);
805 up_write(¤t
->namespace->sem
);
807 path_release(&parent_nd
);
808 path_release(&old_nd
);
813 * create a new mount for userspace and request it to be added into the
816 static int do_new_mount(struct nameidata
*nd
, char *type
, int flags
,
817 int mnt_flags
, char *name
, void *data
)
819 struct vfsmount
*mnt
;
821 if (!type
|| !memchr(type
, 0, PAGE_SIZE
))
824 /* we need capabilities... */
825 if (!capable(CAP_SYS_ADMIN
))
828 mnt
= do_kern_mount(type
, flags
, name
, data
);
832 return do_add_mount(mnt
, nd
, mnt_flags
, NULL
);
836 * add a mount into a namespace's mount tree
837 * - provide the option of adding the new mount to an expiration list
839 int do_add_mount(struct vfsmount
*newmnt
, struct nameidata
*nd
,
840 int mnt_flags
, struct list_head
*fslist
)
844 down_write(¤t
->namespace->sem
);
845 /* Something was mounted here while we slept */
846 while(d_mountpoint(nd
->dentry
) && follow_down(&nd
->mnt
, &nd
->dentry
))
849 if (!check_mnt(nd
->mnt
))
852 /* Refuse the same filesystem on the same mount point */
854 if (nd
->mnt
->mnt_sb
== newmnt
->mnt_sb
&&
855 nd
->mnt
->mnt_root
== nd
->dentry
)
859 if (S_ISLNK(newmnt
->mnt_root
->d_inode
->i_mode
))
862 newmnt
->mnt_flags
= mnt_flags
;
863 newmnt
->mnt_namespace
= current
->namespace;
864 err
= graft_tree(newmnt
, nd
);
866 if (err
== 0 && fslist
) {
867 /* add to the specified expiration list */
868 spin_lock(&vfsmount_lock
);
869 list_add_tail(&newmnt
->mnt_expire
, fslist
);
870 spin_unlock(&vfsmount_lock
);
874 up_write(¤t
->namespace->sem
);
879 EXPORT_SYMBOL_GPL(do_add_mount
);
881 static void expire_mount(struct vfsmount
*mnt
, struct list_head
*mounts
)
883 spin_lock(&vfsmount_lock
);
886 * Check if mount is still attached, if not, let whoever holds it deal
889 if (mnt
->mnt_parent
== mnt
) {
890 spin_unlock(&vfsmount_lock
);
895 * Check that it is still dead: the count should now be 2 - as
896 * contributed by the vfsmount parent and the mntget above
898 if (atomic_read(&mnt
->mnt_count
) == 2) {
899 struct nameidata old_nd
;
901 /* delete from the namespace */
902 touch_namespace(mnt
->mnt_namespace
);
903 list_del_init(&mnt
->mnt_list
);
904 mnt
->mnt_namespace
= NULL
;
905 detach_mnt(mnt
, &old_nd
);
906 spin_unlock(&vfsmount_lock
);
907 path_release(&old_nd
);
911 * Someone brought it back to life whilst we didn't have any
912 * locks held so return it to the expiration list
914 list_add_tail(&mnt
->mnt_expire
, mounts
);
915 spin_unlock(&vfsmount_lock
);
920 * process a list of expirable mountpoints with the intent of discarding any
921 * mountpoints that aren't in use and haven't been touched since last we came
924 void mark_mounts_for_expiry(struct list_head
*mounts
)
926 struct namespace *namespace;
927 struct vfsmount
*mnt
, *next
;
928 LIST_HEAD(graveyard
);
930 if (list_empty(mounts
))
933 spin_lock(&vfsmount_lock
);
935 /* extract from the expiration list every vfsmount that matches the
936 * following criteria:
937 * - only referenced by its parent vfsmount
938 * - still marked for expiry (marked on the last call here; marks are
939 * cleared by mntput())
941 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
942 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
943 atomic_read(&mnt
->mnt_count
) != 1)
947 list_move(&mnt
->mnt_expire
, &graveyard
);
951 * go through the vfsmounts we've just consigned to the graveyard to
952 * - check that they're still dead
953 * - delete the vfsmount from the appropriate namespace under lock
954 * - dispose of the corpse
956 while (!list_empty(&graveyard
)) {
957 mnt
= list_entry(graveyard
.next
, struct vfsmount
, mnt_expire
);
958 list_del_init(&mnt
->mnt_expire
);
960 /* don't do anything if the namespace is dead - all the
961 * vfsmounts from it are going away anyway */
962 namespace = mnt
->mnt_namespace
;
963 if (!namespace || !namespace->root
)
965 get_namespace(namespace);
967 spin_unlock(&vfsmount_lock
);
968 down_write(&namespace->sem
);
969 expire_mount(mnt
, mounts
);
970 up_write(&namespace->sem
);
973 put_namespace(namespace);
975 spin_lock(&vfsmount_lock
);
978 spin_unlock(&vfsmount_lock
);
981 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
984 * Some copy_from_user() implementations do not return the exact number of
985 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
986 * Note that this function differs from copy_from_user() in that it will oops
987 * on bad values of `to', rather than returning a short copy.
990 exact_copy_from_user(void *to
, const void __user
*from
, unsigned long n
)
993 const char __user
*f
= from
;
996 if (!access_ok(VERIFY_READ
, from
, n
))
1000 if (__get_user(c
, f
)) {
1011 int copy_mount_options(const void __user
*data
, unsigned long *where
)
1021 if (!(page
= __get_free_page(GFP_KERNEL
)))
1024 /* We only care that *some* data at the address the user
1025 * gave us is valid. Just in case, we'll zero
1026 * the remainder of the page.
1028 /* copy_from_user cannot cross TASK_SIZE ! */
1029 size
= TASK_SIZE
- (unsigned long)data
;
1030 if (size
> PAGE_SIZE
)
1033 i
= size
- exact_copy_from_user((void *)page
, data
, size
);
1039 memset((char *)page
+ i
, 0, PAGE_SIZE
- i
);
1045 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
1046 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
1048 * data is a (void *) that can point to any structure up to
1049 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
1050 * information (or be NULL).
1052 * Pre-0.97 versions of mount() didn't have a flags word.
1053 * When the flags word was introduced its top half was required
1054 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
1055 * Therefore, if this magic number is present, it carries no information
1056 * and must be discarded.
1058 long do_mount(char * dev_name
, char * dir_name
, char *type_page
,
1059 unsigned long flags
, void *data_page
)
1061 struct nameidata nd
;
1066 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
1067 flags
&= ~MS_MGC_MSK
;
1069 /* Basic sanity checks */
1071 if (!dir_name
|| !*dir_name
|| !memchr(dir_name
, 0, PAGE_SIZE
))
1073 if (dev_name
&& !memchr(dev_name
, 0, PAGE_SIZE
))
1077 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
1079 /* Separate the per-mountpoint flags */
1080 if (flags
& MS_NOSUID
)
1081 mnt_flags
|= MNT_NOSUID
;
1082 if (flags
& MS_NODEV
)
1083 mnt_flags
|= MNT_NODEV
;
1084 if (flags
& MS_NOEXEC
)
1085 mnt_flags
|= MNT_NOEXEC
;
1086 flags
&= ~(MS_NOSUID
|MS_NOEXEC
|MS_NODEV
|MS_ACTIVE
);
1088 /* ... and get the mountpoint */
1089 retval
= path_lookup(dir_name
, LOOKUP_FOLLOW
, &nd
);
1093 retval
= security_sb_mount(dev_name
, &nd
, type_page
, flags
, data_page
);
1097 if (flags
& MS_REMOUNT
)
1098 retval
= do_remount(&nd
, flags
& ~MS_REMOUNT
, mnt_flags
,
1100 else if (flags
& MS_BIND
)
1101 retval
= do_loopback(&nd
, dev_name
, flags
& MS_REC
);
1102 else if (flags
& MS_MOVE
)
1103 retval
= do_move_mount(&nd
, dev_name
);
1105 retval
= do_new_mount(&nd
, type_page
, flags
, mnt_flags
,
1106 dev_name
, data_page
);
1112 int copy_namespace(int flags
, struct task_struct
*tsk
)
1114 struct namespace *namespace = tsk
->namespace;
1115 struct namespace *new_ns
;
1116 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
, *altrootmnt
= NULL
;
1117 struct fs_struct
*fs
= tsk
->fs
;
1118 struct vfsmount
*p
, *q
;
1123 get_namespace(namespace);
1125 if (!(flags
& CLONE_NEWNS
))
1128 if (!capable(CAP_SYS_ADMIN
)) {
1129 put_namespace(namespace);
1133 new_ns
= kmalloc(sizeof(struct namespace), GFP_KERNEL
);
1137 atomic_set(&new_ns
->count
, 1);
1138 init_rwsem(&new_ns
->sem
);
1139 INIT_LIST_HEAD(&new_ns
->list
);
1140 init_waitqueue_head(&new_ns
->poll
);
1143 down_write(&tsk
->namespace->sem
);
1144 /* First pass: copy the tree topology */
1145 new_ns
->root
= copy_tree(namespace->root
, namespace->root
->mnt_root
);
1146 if (!new_ns
->root
) {
1147 up_write(&tsk
->namespace->sem
);
1151 spin_lock(&vfsmount_lock
);
1152 list_add_tail(&new_ns
->list
, &new_ns
->root
->mnt_list
);
1153 spin_unlock(&vfsmount_lock
);
1156 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
1157 * as belonging to new namespace. We have already acquired a private
1158 * fs_struct, so tsk->fs->lock is not needed.
1160 p
= namespace->root
;
1163 q
->mnt_namespace
= new_ns
;
1165 if (p
== fs
->rootmnt
) {
1167 fs
->rootmnt
= mntget(q
);
1169 if (p
== fs
->pwdmnt
) {
1171 fs
->pwdmnt
= mntget(q
);
1173 if (p
== fs
->altrootmnt
) {
1175 fs
->altrootmnt
= mntget(q
);
1178 p
= next_mnt(p
, namespace->root
);
1179 q
= next_mnt(q
, new_ns
->root
);
1181 up_write(&tsk
->namespace->sem
);
1183 tsk
->namespace = new_ns
;
1192 put_namespace(namespace);
1196 put_namespace(namespace);
1200 asmlinkage
long sys_mount(char __user
* dev_name
, char __user
* dir_name
,
1201 char __user
* type
, unsigned long flags
,
1205 unsigned long data_page
;
1206 unsigned long type_page
;
1207 unsigned long dev_page
;
1210 retval
= copy_mount_options (type
, &type_page
);
1214 dir_page
= getname(dir_name
);
1215 retval
= PTR_ERR(dir_page
);
1216 if (IS_ERR(dir_page
))
1219 retval
= copy_mount_options (dev_name
, &dev_page
);
1223 retval
= copy_mount_options (data
, &data_page
);
1228 retval
= do_mount((char*)dev_page
, dir_page
, (char*)type_page
,
1229 flags
, (void*)data_page
);
1231 free_page(data_page
);
1234 free_page(dev_page
);
1238 free_page(type_page
);
1243 * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
1244 * It can block. Requires the big lock held.
1246 void set_fs_root(struct fs_struct
*fs
, struct vfsmount
*mnt
,
1247 struct dentry
*dentry
)
1249 struct dentry
*old_root
;
1250 struct vfsmount
*old_rootmnt
;
1251 write_lock(&fs
->lock
);
1252 old_root
= fs
->root
;
1253 old_rootmnt
= fs
->rootmnt
;
1254 fs
->rootmnt
= mntget(mnt
);
1255 fs
->root
= dget(dentry
);
1256 write_unlock(&fs
->lock
);
1259 mntput(old_rootmnt
);
1264 * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
1265 * It can block. Requires the big lock held.
1267 void set_fs_pwd(struct fs_struct
*fs
, struct vfsmount
*mnt
,
1268 struct dentry
*dentry
)
1270 struct dentry
*old_pwd
;
1271 struct vfsmount
*old_pwdmnt
;
1273 write_lock(&fs
->lock
);
1275 old_pwdmnt
= fs
->pwdmnt
;
1276 fs
->pwdmnt
= mntget(mnt
);
1277 fs
->pwd
= dget(dentry
);
1278 write_unlock(&fs
->lock
);
1286 static void chroot_fs_refs(struct nameidata
*old_nd
, struct nameidata
*new_nd
)
1288 struct task_struct
*g
, *p
;
1289 struct fs_struct
*fs
;
1291 read_lock(&tasklist_lock
);
1292 do_each_thread(g
, p
) {
1296 atomic_inc(&fs
->count
);
1298 if (fs
->root
==old_nd
->dentry
&&fs
->rootmnt
==old_nd
->mnt
)
1299 set_fs_root(fs
, new_nd
->mnt
, new_nd
->dentry
);
1300 if (fs
->pwd
==old_nd
->dentry
&&fs
->pwdmnt
==old_nd
->mnt
)
1301 set_fs_pwd(fs
, new_nd
->mnt
, new_nd
->dentry
);
1305 } while_each_thread(g
, p
);
1306 read_unlock(&tasklist_lock
);
1310 * pivot_root Semantics:
1311 * Moves the root file system of the current process to the directory put_old,
1312 * makes new_root as the new root file system of the current process, and sets
1313 * root/cwd of all processes which had them on the current root to new_root.
1316 * The new_root and put_old must be directories, and must not be on the
1317 * same file system as the current process root. The put_old must be
1318 * underneath new_root, i.e. adding a non-zero number of /.. to the string
1319 * pointed to by put_old must yield the same directory as new_root. No other
1320 * file system may be mounted on put_old. After all, new_root is a mountpoint.
1323 * - we don't move root/cwd if they are not at the root (reason: if something
1324 * cared enough to change them, it's probably wrong to force them elsewhere)
1325 * - it's okay to pick a root that isn't the root of a file system, e.g.
1326 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
1327 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
1331 asmlinkage
long sys_pivot_root(const char __user
*new_root
, const char __user
*put_old
)
1333 struct vfsmount
*tmp
;
1334 struct nameidata new_nd
, old_nd
, parent_nd
, root_parent
, user_nd
;
1337 if (!capable(CAP_SYS_ADMIN
))
1342 error
= __user_walk(new_root
, LOOKUP_FOLLOW
|LOOKUP_DIRECTORY
, &new_nd
);
1346 if (!check_mnt(new_nd
.mnt
))
1349 error
= __user_walk(put_old
, LOOKUP_FOLLOW
|LOOKUP_DIRECTORY
, &old_nd
);
1353 error
= security_sb_pivotroot(&old_nd
, &new_nd
);
1355 path_release(&old_nd
);
1359 read_lock(¤t
->fs
->lock
);
1360 user_nd
.mnt
= mntget(current
->fs
->rootmnt
);
1361 user_nd
.dentry
= dget(current
->fs
->root
);
1362 read_unlock(¤t
->fs
->lock
);
1363 down_write(¤t
->namespace->sem
);
1364 down(&old_nd
.dentry
->d_inode
->i_sem
);
1366 if (!check_mnt(user_nd
.mnt
))
1369 if (IS_DEADDIR(new_nd
.dentry
->d_inode
))
1371 if (d_unhashed(new_nd
.dentry
) && !IS_ROOT(new_nd
.dentry
))
1373 if (d_unhashed(old_nd
.dentry
) && !IS_ROOT(old_nd
.dentry
))
1376 if (new_nd
.mnt
== user_nd
.mnt
|| old_nd
.mnt
== user_nd
.mnt
)
1377 goto out2
; /* loop, on the same file system */
1379 if (user_nd
.mnt
->mnt_root
!= user_nd
.dentry
)
1380 goto out2
; /* not a mountpoint */
1381 if (user_nd
.mnt
->mnt_parent
== user_nd
.mnt
)
1382 goto out2
; /* not attached */
1383 if (new_nd
.mnt
->mnt_root
!= new_nd
.dentry
)
1384 goto out2
; /* not a mountpoint */
1385 if (new_nd
.mnt
->mnt_parent
== new_nd
.mnt
)
1386 goto out2
; /* not attached */
1387 tmp
= old_nd
.mnt
; /* make sure we can reach put_old from new_root */
1388 spin_lock(&vfsmount_lock
);
1389 if (tmp
!= new_nd
.mnt
) {
1391 if (tmp
->mnt_parent
== tmp
)
1392 goto out3
; /* already mounted on put_old */
1393 if (tmp
->mnt_parent
== new_nd
.mnt
)
1395 tmp
= tmp
->mnt_parent
;
1397 if (!is_subdir(tmp
->mnt_mountpoint
, new_nd
.dentry
))
1399 } else if (!is_subdir(old_nd
.dentry
, new_nd
.dentry
))
1401 detach_mnt(new_nd
.mnt
, &parent_nd
);
1402 detach_mnt(user_nd
.mnt
, &root_parent
);
1403 attach_mnt(user_nd
.mnt
, &old_nd
); /* mount old root on put_old */
1404 attach_mnt(new_nd
.mnt
, &root_parent
); /* mount new_root on / */
1405 touch_namespace(current
->namespace);
1406 spin_unlock(&vfsmount_lock
);
1407 chroot_fs_refs(&user_nd
, &new_nd
);
1408 security_sb_post_pivotroot(&user_nd
, &new_nd
);
1410 path_release(&root_parent
);
1411 path_release(&parent_nd
);
1413 up(&old_nd
.dentry
->d_inode
->i_sem
);
1414 up_write(¤t
->namespace->sem
);
1415 path_release(&user_nd
);
1416 path_release(&old_nd
);
1418 path_release(&new_nd
);
1423 spin_unlock(&vfsmount_lock
);
1427 static void __init
init_mount_tree(void)
1429 struct vfsmount
*mnt
;
1430 struct namespace *namespace;
1431 struct task_struct
*g
, *p
;
1433 mnt
= do_kern_mount("rootfs", 0, "rootfs", NULL
);
1435 panic("Can't create rootfs");
1436 namespace = kmalloc(sizeof(*namespace), GFP_KERNEL
);
1438 panic("Can't allocate initial namespace");
1439 atomic_set(&namespace->count
, 1);
1440 INIT_LIST_HEAD(&namespace->list
);
1441 init_rwsem(&namespace->sem
);
1442 init_waitqueue_head(&namespace->poll
);
1443 namespace->event
= 0;
1444 list_add(&mnt
->mnt_list
, &namespace->list
);
1445 namespace->root
= mnt
;
1446 mnt
->mnt_namespace
= namespace;
1448 init_task
.namespace = namespace;
1449 read_lock(&tasklist_lock
);
1450 do_each_thread(g
, p
) {
1451 get_namespace(namespace);
1452 p
->namespace = namespace;
1453 } while_each_thread(g
, p
);
1454 read_unlock(&tasklist_lock
);
1456 set_fs_pwd(current
->fs
, namespace->root
, namespace->root
->mnt_root
);
1457 set_fs_root(current
->fs
, namespace->root
, namespace->root
->mnt_root
);
1460 void __init
mnt_init(unsigned long mempages
)
1462 struct list_head
*d
;
1463 unsigned int nr_hash
;
1466 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct vfsmount
),
1467 0, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
, NULL
);
1469 mount_hashtable
= (struct list_head
*)
1470 __get_free_page(GFP_ATOMIC
);
1472 if (!mount_hashtable
)
1473 panic("Failed to allocate mount hash table\n");
1476 * Find the power-of-two list-heads that can fit into the allocation..
1477 * We don't guarantee that "sizeof(struct list_head)" is necessarily
1480 nr_hash
= PAGE_SIZE
/ sizeof(struct list_head
);
1484 } while ((nr_hash
>> hash_bits
) != 0);
1488 * Re-calculate the actual number of entries and the mask
1489 * from the number of bits we can fit.
1491 nr_hash
= 1UL << hash_bits
;
1492 hash_mask
= nr_hash
-1;
1494 printk("Mount-cache hash table entries: %d\n", nr_hash
);
1496 /* And initialize the newly allocated array */
1497 d
= mount_hashtable
;
1509 void __put_namespace(struct namespace *namespace)
1511 struct vfsmount
*root
= namespace->root
;
1512 namespace->root
= NULL
;
1513 spin_unlock(&vfsmount_lock
);
1514 down_write(&namespace->sem
);
1515 spin_lock(&vfsmount_lock
);
1517 spin_unlock(&vfsmount_lock
);
1518 up_write(&namespace->sem
);