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>
12 #include <linux/nsproxy.h>
16 /* return the next shared peer mount of @p */
17 static inline struct mount
*next_peer(struct mount
*p
)
19 return list_entry(p
->mnt_share
.next
, struct mount
, mnt_share
);
22 static inline struct mount
*first_slave(struct mount
*p
)
24 return list_entry(p
->mnt_slave_list
.next
, struct mount
, mnt_slave
);
27 static inline struct mount
*next_slave(struct mount
*p
)
29 return list_entry(p
->mnt_slave
.next
, struct mount
, mnt_slave
);
32 static struct mount
*get_peer_under_root(struct mount
*mnt
,
33 struct mnt_namespace
*ns
,
34 const struct path
*root
)
36 struct mount
*m
= mnt
;
39 /* Check the namespace first for optimization */
40 if (m
->mnt_ns
== ns
&& is_path_reachable(m
, m
->mnt
.mnt_root
, root
))
50 * Get ID of closest dominating peer group having a representative
51 * under the given root.
53 * Caller must hold namespace_sem
55 int get_dominating_id(struct mount
*mnt
, const struct path
*root
)
59 for (m
= mnt
->mnt_master
; m
!= NULL
; m
= m
->mnt_master
) {
60 struct mount
*d
= get_peer_under_root(m
, mnt
->mnt_ns
, root
);
62 return d
->mnt_group_id
;
68 static int do_make_slave(struct mount
*mnt
)
70 struct mount
*peer_mnt
= mnt
, *master
= mnt
->mnt_master
;
71 struct mount
*slave_mnt
;
74 * slave 'mnt' to a peer mount that has the
75 * same root dentry. If none is available then
76 * slave it to anything that is available.
78 while ((peer_mnt
= next_peer(peer_mnt
)) != mnt
&&
79 peer_mnt
->mnt
.mnt_root
!= mnt
->mnt
.mnt_root
) ;
81 if (peer_mnt
== mnt
) {
82 peer_mnt
= next_peer(mnt
);
86 if (mnt
->mnt_group_id
&& IS_MNT_SHARED(mnt
) &&
87 list_empty(&mnt
->mnt_share
))
88 mnt_release_group_id(mnt
);
90 list_del_init(&mnt
->mnt_share
);
91 mnt
->mnt_group_id
= 0;
97 list_for_each_entry(slave_mnt
, &mnt
->mnt_slave_list
, mnt_slave
)
98 slave_mnt
->mnt_master
= master
;
99 list_move(&mnt
->mnt_slave
, &master
->mnt_slave_list
);
100 list_splice(&mnt
->mnt_slave_list
, master
->mnt_slave_list
.prev
);
101 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
103 struct list_head
*p
= &mnt
->mnt_slave_list
;
104 while (!list_empty(p
)) {
105 slave_mnt
= list_first_entry(p
,
106 struct mount
, mnt_slave
);
107 list_del_init(&slave_mnt
->mnt_slave
);
108 slave_mnt
->mnt_master
= NULL
;
111 mnt
->mnt_master
= master
;
112 CLEAR_MNT_SHARED(mnt
);
117 * vfsmount lock must be held for write
119 void change_mnt_propagation(struct mount
*mnt
, int type
)
121 if (type
== MS_SHARED
) {
126 if (type
!= MS_SLAVE
) {
127 list_del_init(&mnt
->mnt_slave
);
128 mnt
->mnt_master
= NULL
;
129 if (type
== MS_UNBINDABLE
)
130 mnt
->mnt
.mnt_flags
|= MNT_UNBINDABLE
;
132 mnt
->mnt
.mnt_flags
&= ~MNT_UNBINDABLE
;
137 * get the next mount in the propagation tree.
138 * @m: the mount seen last
139 * @origin: the original mount from where the tree walk initiated
141 * Note that peer groups form contiguous segments of slave lists.
142 * We rely on that in get_source() to be able to find out if
143 * vfsmount found while iterating with propagation_next() is
144 * a peer of one we'd found earlier.
146 static struct mount
*propagation_next(struct mount
*m
,
147 struct mount
*origin
)
149 /* are there any slaves of this mount? */
150 if (!IS_MNT_NEW(m
) && !list_empty(&m
->mnt_slave_list
))
151 return first_slave(m
);
154 struct mount
*master
= m
->mnt_master
;
156 if (master
== origin
->mnt_master
) {
157 struct mount
*next
= next_peer(m
);
158 return (next
== origin
) ? NULL
: next
;
159 } else if (m
->mnt_slave
.next
!= &master
->mnt_slave_list
)
160 return next_slave(m
);
168 * return the source mount to be used for cloning
170 * @dest the current destination mount
171 * @last_dest the last seen destination mount
172 * @last_src the last seen source mount
173 * @type return CL_SLAVE if the new mount has to be
176 static struct mount
*get_source(struct mount
*dest
,
177 struct mount
*last_dest
,
178 struct mount
*last_src
,
181 struct mount
*p_last_src
= NULL
;
182 struct mount
*p_last_dest
= NULL
;
184 while (last_dest
!= dest
->mnt_master
) {
185 p_last_dest
= last_dest
;
186 p_last_src
= last_src
;
187 last_dest
= last_dest
->mnt_master
;
188 last_src
= last_src
->mnt_master
;
193 p_last_dest
= next_peer(p_last_dest
);
194 } while (IS_MNT_NEW(p_last_dest
));
195 /* is that a peer of the earlier? */
196 if (dest
== p_last_dest
) {
197 *type
= CL_MAKE_SHARED
;
201 /* slave of the earlier, then */
203 /* beginning of peer group among the slaves? */
204 if (IS_MNT_SHARED(dest
))
205 *type
|= CL_MAKE_SHARED
;
210 * mount 'source_mnt' under the destination 'dest_mnt' at
211 * dentry 'dest_dentry'. And propagate that mount to
212 * all the peer and slave mounts of 'dest_mnt'.
213 * Link all the new mounts into a propagation tree headed at
214 * source_mnt. Also link all the new mounts using ->mnt_list
215 * headed at source_mnt's ->mnt_list
217 * @dest_mnt: destination mount.
218 * @dest_dentry: destination dentry.
219 * @source_mnt: source mount.
220 * @tree_list : list of heads of trees to be attached.
222 int propagate_mnt(struct mount
*dest_mnt
, struct mountpoint
*dest_mp
,
223 struct mount
*source_mnt
, struct list_head
*tree_list
)
225 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
226 struct mount
*m
, *child
;
228 struct mount
*prev_dest_mnt
= dest_mnt
;
229 struct mount
*prev_src_mnt
= source_mnt
;
232 for (m
= propagation_next(dest_mnt
, dest_mnt
); m
;
233 m
= propagation_next(m
, dest_mnt
)) {
235 struct mount
*source
;
240 source
= get_source(m
, prev_dest_mnt
, prev_src_mnt
, &type
);
242 /* Notice when we are propagating across user namespaces */
243 if (m
->mnt_ns
->user_ns
!= user_ns
)
244 type
|= CL_UNPRIVILEGED
;
246 child
= copy_tree(source
, source
->mnt
.mnt_root
, type
);
248 ret
= PTR_ERR(child
);
249 list_splice(tree_list
, tmp_list
.prev
);
253 if (is_subdir(dest_mp
->m_dentry
, m
->mnt
.mnt_root
)) {
254 mnt_set_mountpoint(m
, dest_mp
, child
);
255 list_add_tail(&child
->mnt_hash
, tree_list
);
258 * This can happen if the parent mount was bind mounted
259 * on some subdirectory of a shared/slave mount.
261 list_add_tail(&child
->mnt_hash
, &tmp_list
);
264 prev_src_mnt
= child
;
267 br_write_lock(&vfsmount_lock
);
268 while (!list_empty(&tmp_list
)) {
269 child
= list_first_entry(&tmp_list
, struct mount
, mnt_hash
);
270 umount_tree(child
, 0);
272 br_write_unlock(&vfsmount_lock
);
277 * return true if the refcount is greater than count
279 static inline int do_refcount_check(struct mount
*mnt
, int count
)
281 int mycount
= mnt_get_count(mnt
) - mnt
->mnt_ghosts
;
282 return (mycount
> count
);
286 * check if the mount 'mnt' can be unmounted successfully.
287 * @mnt: the mount to be checked for unmount
288 * NOTE: unmounting 'mnt' would naturally propagate to all
289 * other mounts its parent propagates to.
290 * Check if any of these mounts that **do not have submounts**
291 * have more references than 'refcnt'. If so return busy.
293 * vfsmount lock must be held for write
295 int propagate_mount_busy(struct mount
*mnt
, int refcnt
)
297 struct mount
*m
, *child
;
298 struct mount
*parent
= mnt
->mnt_parent
;
302 return do_refcount_check(mnt
, refcnt
);
305 * quickly check if the current mount can be unmounted.
306 * If not, we don't have to go checking for all other
309 if (!list_empty(&mnt
->mnt_mounts
) || do_refcount_check(mnt
, refcnt
))
312 for (m
= propagation_next(parent
, parent
); m
;
313 m
= propagation_next(m
, parent
)) {
314 child
= __lookup_mnt(&m
->mnt
, mnt
->mnt_mountpoint
, 0);
315 if (child
&& list_empty(&child
->mnt_mounts
) &&
316 (ret
= do_refcount_check(child
, 1)))
323 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
324 * parent propagates to.
326 static void __propagate_umount(struct mount
*mnt
)
328 struct mount
*parent
= mnt
->mnt_parent
;
331 BUG_ON(parent
== mnt
);
333 for (m
= propagation_next(parent
, parent
); m
;
334 m
= propagation_next(m
, parent
)) {
336 struct mount
*child
= __lookup_mnt(&m
->mnt
,
337 mnt
->mnt_mountpoint
, 0);
339 * umount the child only if the child has no
342 if (child
&& list_empty(&child
->mnt_mounts
))
343 list_move_tail(&child
->mnt_hash
, &mnt
->mnt_hash
);
348 * collect all mounts that receive propagation from the mount in @list,
349 * and return these additional mounts in the same list.
350 * @list: the list of mounts to be unmounted.
352 * vfsmount lock must be held for write
354 int propagate_umount(struct list_head
*list
)
358 list_for_each_entry(mnt
, list
, mnt_hash
)
359 __propagate_umount(mnt
);
This page took 0.037642 seconds and 6 git commands to generate.