4 * (C) Copyright IBM Corporation 2005.
5 * Released under GPL v2.
6 * Author : Ram Pai (linuxram@us.ibm.com)
9 #include <linux/mnt_namespace.h>
10 #include <linux/mount.h>
15 /* return the next shared peer mount of @p */
16 static inline struct vfsmount
*next_peer(struct vfsmount
*p
)
18 return list_entry(p
->mnt_share
.next
, struct vfsmount
, mnt_share
);
21 static inline struct vfsmount
*first_slave(struct vfsmount
*p
)
23 return list_entry(p
->mnt_slave_list
.next
, struct vfsmount
, mnt_slave
);
26 static inline struct vfsmount
*next_slave(struct vfsmount
*p
)
28 return list_entry(p
->mnt_slave
.next
, struct vfsmount
, mnt_slave
);
32 * Return true if path is reachable from root
34 * namespace_sem is held, and mnt is attached
36 static bool is_path_reachable(struct vfsmount
*mnt
, struct dentry
*dentry
,
37 const struct path
*root
)
39 while (mnt
!= root
->mnt
&& mnt
->mnt_parent
!= mnt
) {
40 dentry
= mnt
->mnt_mountpoint
;
41 mnt
= mnt
->mnt_parent
;
43 return mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
46 static struct vfsmount
*get_peer_under_root(struct vfsmount
*mnt
,
47 struct mnt_namespace
*ns
,
48 const struct path
*root
)
50 struct vfsmount
*m
= mnt
;
53 /* Check the namespace first for optimization */
54 if (m
->mnt_ns
== ns
&& is_path_reachable(m
, m
->mnt_root
, root
))
64 * Get ID of closest dominating peer group having a representative
65 * under the given root.
67 * Caller must hold namespace_sem
69 int get_dominating_id(struct vfsmount
*mnt
, const struct path
*root
)
73 for (m
= mnt
->mnt_master
; m
!= NULL
; m
= m
->mnt_master
) {
74 struct vfsmount
*d
= get_peer_under_root(m
, mnt
->mnt_ns
, root
);
76 return d
->mnt_group_id
;
82 static int do_make_slave(struct vfsmount
*mnt
)
84 struct vfsmount
*peer_mnt
= mnt
, *master
= mnt
->mnt_master
;
85 struct vfsmount
*slave_mnt
;
88 * slave 'mnt' to a peer mount that has the
89 * same root dentry. If none is available then
90 * slave it to anything that is available.
92 while ((peer_mnt
= next_peer(peer_mnt
)) != mnt
&&
93 peer_mnt
->mnt_root
!= mnt
->mnt_root
) ;
95 if (peer_mnt
== mnt
) {
96 peer_mnt
= next_peer(mnt
);
100 if (IS_MNT_SHARED(mnt
) && list_empty(&mnt
->mnt_share
))
101 mnt_release_group_id(mnt
);
103 list_del_init(&mnt
->mnt_share
);
104 mnt
->mnt_group_id
= 0;
110 list_for_each_entry(slave_mnt
, &mnt
->mnt_slave_list
, mnt_slave
)
111 slave_mnt
->mnt_master
= master
;
112 list_move(&mnt
->mnt_slave
, &master
->mnt_slave_list
);
113 list_splice(&mnt
->mnt_slave_list
, master
->mnt_slave_list
.prev
);
114 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
116 struct list_head
*p
= &mnt
->mnt_slave_list
;
117 while (!list_empty(p
)) {
118 slave_mnt
= list_first_entry(p
,
119 struct vfsmount
, mnt_slave
);
120 list_del_init(&slave_mnt
->mnt_slave
);
121 slave_mnt
->mnt_master
= NULL
;
124 mnt
->mnt_master
= master
;
125 CLEAR_MNT_SHARED(mnt
);
130 * vfsmount lock must be held for write
132 void change_mnt_propagation(struct vfsmount
*mnt
, int type
)
134 if (type
== MS_SHARED
) {
139 if (type
!= MS_SLAVE
) {
140 list_del_init(&mnt
->mnt_slave
);
141 mnt
->mnt_master
= NULL
;
142 if (type
== MS_UNBINDABLE
)
143 mnt
->mnt_flags
|= MNT_UNBINDABLE
;
145 mnt
->mnt_flags
&= ~MNT_UNBINDABLE
;
150 * get the next mount in the propagation tree.
151 * @m: the mount seen last
152 * @origin: the original mount from where the tree walk initiated
154 * Note that peer groups form contiguous segments of slave lists.
155 * We rely on that in get_source() to be able to find out if
156 * vfsmount found while iterating with propagation_next() is
157 * a peer of one we'd found earlier.
159 static struct vfsmount
*propagation_next(struct vfsmount
*m
,
160 struct vfsmount
*origin
)
162 /* are there any slaves of this mount? */
163 if (!IS_MNT_NEW(m
) && !list_empty(&m
->mnt_slave_list
))
164 return first_slave(m
);
167 struct vfsmount
*next
;
168 struct vfsmount
*master
= m
->mnt_master
;
170 if (master
== origin
->mnt_master
) {
172 return ((next
== origin
) ? NULL
: next
);
173 } else if (m
->mnt_slave
.next
!= &master
->mnt_slave_list
)
174 return next_slave(m
);
182 * return the source mount to be used for cloning
184 * @dest the current destination mount
185 * @last_dest the last seen destination mount
186 * @last_src the last seen source mount
187 * @type return CL_SLAVE if the new mount has to be
190 static struct vfsmount
*get_source(struct vfsmount
*dest
,
191 struct vfsmount
*last_dest
,
192 struct vfsmount
*last_src
,
195 struct vfsmount
*p_last_src
= NULL
;
196 struct vfsmount
*p_last_dest
= NULL
;
198 while (last_dest
!= dest
->mnt_master
) {
199 p_last_dest
= last_dest
;
200 p_last_src
= last_src
;
201 last_dest
= last_dest
->mnt_master
;
202 last_src
= last_src
->mnt_master
;
207 p_last_dest
= next_peer(p_last_dest
);
208 } while (IS_MNT_NEW(p_last_dest
));
209 /* is that a peer of the earlier? */
210 if (dest
== p_last_dest
) {
211 *type
= CL_MAKE_SHARED
;
215 /* slave of the earlier, then */
217 /* beginning of peer group among the slaves? */
218 if (IS_MNT_SHARED(dest
))
219 *type
|= CL_MAKE_SHARED
;
224 * mount 'source_mnt' under the destination 'dest_mnt' at
225 * dentry 'dest_dentry'. And propagate that mount to
226 * all the peer and slave mounts of 'dest_mnt'.
227 * Link all the new mounts into a propagation tree headed at
228 * source_mnt. Also link all the new mounts using ->mnt_list
229 * headed at source_mnt's ->mnt_list
231 * @dest_mnt: destination mount.
232 * @dest_dentry: destination dentry.
233 * @source_mnt: source mount.
234 * @tree_list : list of heads of trees to be attached.
236 int propagate_mnt(struct vfsmount
*dest_mnt
, struct dentry
*dest_dentry
,
237 struct vfsmount
*source_mnt
, struct list_head
*tree_list
)
239 struct vfsmount
*m
, *child
;
241 struct vfsmount
*prev_dest_mnt
= dest_mnt
;
242 struct vfsmount
*prev_src_mnt
= source_mnt
;
244 LIST_HEAD(umount_list
);
246 for (m
= propagation_next(dest_mnt
, dest_mnt
); m
;
247 m
= propagation_next(m
, dest_mnt
)) {
249 struct vfsmount
*source
;
254 source
= get_source(m
, prev_dest_mnt
, prev_src_mnt
, &type
);
256 if (!(child
= copy_tree(source
, source
->mnt_root
, type
))) {
258 list_splice(tree_list
, tmp_list
.prev
);
262 if (is_subdir(dest_dentry
, m
->mnt_root
)) {
263 mnt_set_mountpoint(m
, dest_dentry
, child
);
264 list_add_tail(&child
->mnt_hash
, tree_list
);
267 * This can happen if the parent mount was bind mounted
268 * on some subdirectory of a shared/slave mount.
270 list_add_tail(&child
->mnt_hash
, &tmp_list
);
273 prev_src_mnt
= child
;
276 br_write_lock(vfsmount_lock
);
277 while (!list_empty(&tmp_list
)) {
278 child
= list_first_entry(&tmp_list
, struct vfsmount
, mnt_hash
);
279 umount_tree(child
, 0, &umount_list
);
281 br_write_unlock(vfsmount_lock
);
282 release_mounts(&umount_list
);
287 * return true if the refcount is greater than count
289 static inline int do_refcount_check(struct vfsmount
*mnt
, int count
)
291 int mycount
= mnt_get_count(mnt
) - mnt
->mnt_ghosts
;
292 return (mycount
> count
);
296 * check if the mount 'mnt' can be unmounted successfully.
297 * @mnt: the mount to be checked for unmount
298 * NOTE: unmounting 'mnt' would naturally propagate to all
299 * other mounts its parent propagates to.
300 * Check if any of these mounts that **do not have submounts**
301 * have more references than 'refcnt'. If so return busy.
303 * vfsmount lock must be held for write
305 int propagate_mount_busy(struct vfsmount
*mnt
, int refcnt
)
307 struct vfsmount
*m
, *child
;
308 struct vfsmount
*parent
= mnt
->mnt_parent
;
312 return do_refcount_check(mnt
, refcnt
);
315 * quickly check if the current mount can be unmounted.
316 * If not, we don't have to go checking for all other
319 if (!list_empty(&mnt
->mnt_mounts
) || do_refcount_check(mnt
, refcnt
))
322 for (m
= propagation_next(parent
, parent
); m
;
323 m
= propagation_next(m
, parent
)) {
324 child
= __lookup_mnt(m
, mnt
->mnt_mountpoint
, 0);
325 if (child
&& list_empty(&child
->mnt_mounts
) &&
326 (ret
= do_refcount_check(child
, 1)))
333 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
334 * parent propagates to.
336 static void __propagate_umount(struct vfsmount
*mnt
)
338 struct vfsmount
*parent
= mnt
->mnt_parent
;
341 BUG_ON(parent
== mnt
);
343 for (m
= propagation_next(parent
, parent
); m
;
344 m
= propagation_next(m
, parent
)) {
346 struct vfsmount
*child
= __lookup_mnt(m
,
347 mnt
->mnt_mountpoint
, 0);
349 * umount the child only if the child has no
352 if (child
&& list_empty(&child
->mnt_mounts
))
353 list_move_tail(&child
->mnt_hash
, &mnt
->mnt_hash
);
358 * collect all mounts that receive propagation from the mount in @list,
359 * and return these additional mounts in the same list.
360 * @list: the list of mounts to be unmounted.
362 * vfsmount lock must be held for write
364 int propagate_umount(struct list_head
*list
)
366 struct vfsmount
*mnt
;
368 list_for_each_entry(mnt
, list
, mnt_hash
)
369 __propagate_umount(mnt
);
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