4 * (C) Copyright IBM Corporation 2005.
5 * Released under GPL v2.
6 * Author : Ram Pai (linuxram@us.ibm.com)
9 #include <linux/namespace.h>
10 #include <linux/mount.h>
14 /* return the next shared peer mount of @p */
15 static inline struct vfsmount
*next_peer(struct vfsmount
*p
)
17 return list_entry(p
->mnt_share
.next
, struct vfsmount
, mnt_share
);
20 static inline struct vfsmount
*first_slave(struct vfsmount
*p
)
22 return list_entry(p
->mnt_slave_list
.next
, struct vfsmount
, mnt_slave
);
25 static inline struct vfsmount
*next_slave(struct vfsmount
*p
)
27 return list_entry(p
->mnt_slave
.next
, struct vfsmount
, mnt_slave
);
30 static int do_make_slave(struct vfsmount
*mnt
)
32 struct vfsmount
*peer_mnt
= mnt
, *master
= mnt
->mnt_master
;
33 struct vfsmount
*slave_mnt
;
36 * slave 'mnt' to a peer mount that has the
37 * same root dentry. If none is available than
38 * slave it to anything that is available.
40 while ((peer_mnt
= next_peer(peer_mnt
)) != mnt
&&
41 peer_mnt
->mnt_root
!= mnt
->mnt_root
) ;
43 if (peer_mnt
== mnt
) {
44 peer_mnt
= next_peer(mnt
);
48 list_del_init(&mnt
->mnt_share
);
54 list_for_each_entry(slave_mnt
, &mnt
->mnt_slave_list
, mnt_slave
)
55 slave_mnt
->mnt_master
= master
;
56 list_del(&mnt
->mnt_slave
);
57 list_add(&mnt
->mnt_slave
, &master
->mnt_slave_list
);
58 list_splice(&mnt
->mnt_slave_list
, master
->mnt_slave_list
.prev
);
59 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
61 struct list_head
*p
= &mnt
->mnt_slave_list
;
62 while (!list_empty(p
)) {
63 slave_mnt
= list_entry(p
->next
,
64 struct vfsmount
, mnt_slave
);
65 list_del_init(&slave_mnt
->mnt_slave
);
66 slave_mnt
->mnt_master
= NULL
;
69 mnt
->mnt_master
= master
;
70 CLEAR_MNT_SHARED(mnt
);
71 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
75 void change_mnt_propagation(struct vfsmount
*mnt
, int type
)
77 if (type
== MS_SHARED
) {
82 if (type
!= MS_SLAVE
) {
83 list_del_init(&mnt
->mnt_slave
);
84 mnt
->mnt_master
= NULL
;
85 if (type
== MS_UNBINDABLE
)
86 mnt
->mnt_flags
|= MNT_UNBINDABLE
;
91 * get the next mount in the propagation tree.
92 * @m: the mount seen last
93 * @origin: the original mount from where the tree walk initiated
95 static struct vfsmount
*propagation_next(struct vfsmount
*m
,
96 struct vfsmount
*origin
)
98 /* are there any slaves of this mount? */
99 if (!IS_MNT_NEW(m
) && !list_empty(&m
->mnt_slave_list
))
100 return first_slave(m
);
103 struct vfsmount
*next
;
104 struct vfsmount
*master
= m
->mnt_master
;
106 if (master
== origin
->mnt_master
) {
108 return ((next
== origin
) ? NULL
: next
);
109 } else if (m
->mnt_slave
.next
!= &master
->mnt_slave_list
)
110 return next_slave(m
);
118 * return the source mount to be used for cloning
120 * @dest the current destination mount
121 * @last_dest the last seen destination mount
122 * @last_src the last seen source mount
123 * @type return CL_SLAVE if the new mount has to be
126 static struct vfsmount
*get_source(struct vfsmount
*dest
,
127 struct vfsmount
*last_dest
,
128 struct vfsmount
*last_src
,
131 struct vfsmount
*p_last_src
= NULL
;
132 struct vfsmount
*p_last_dest
= NULL
;
133 *type
= CL_PROPAGATION
;;
135 if (IS_MNT_SHARED(dest
))
136 *type
|= CL_MAKE_SHARED
;
138 while (last_dest
!= dest
->mnt_master
) {
139 p_last_dest
= last_dest
;
140 p_last_src
= last_src
;
141 last_dest
= last_dest
->mnt_master
;
142 last_src
= last_src
->mnt_master
;
147 p_last_dest
= next_peer(p_last_dest
);
148 } while (IS_MNT_NEW(p_last_dest
));
151 if (dest
!= p_last_dest
) {
159 * mount 'source_mnt' under the destination 'dest_mnt' at
160 * dentry 'dest_dentry'. And propagate that mount to
161 * all the peer and slave mounts of 'dest_mnt'.
162 * Link all the new mounts into a propagation tree headed at
163 * source_mnt. Also link all the new mounts using ->mnt_list
164 * headed at source_mnt's ->mnt_list
166 * @dest_mnt: destination mount.
167 * @dest_dentry: destination dentry.
168 * @source_mnt: source mount.
169 * @tree_list : list of heads of trees to be attached.
171 int propagate_mnt(struct vfsmount
*dest_mnt
, struct dentry
*dest_dentry
,
172 struct vfsmount
*source_mnt
, struct list_head
*tree_list
)
174 struct vfsmount
*m
, *child
;
176 struct vfsmount
*prev_dest_mnt
= dest_mnt
;
177 struct vfsmount
*prev_src_mnt
= source_mnt
;
179 LIST_HEAD(umount_list
);
181 for (m
= propagation_next(dest_mnt
, dest_mnt
); m
;
182 m
= propagation_next(m
, dest_mnt
)) {
184 struct vfsmount
*source
;
189 source
= get_source(m
, prev_dest_mnt
, prev_src_mnt
, &type
);
191 if (!(child
= copy_tree(source
, source
->mnt_root
, type
))) {
193 list_splice(tree_list
, tmp_list
.prev
);
197 if (is_subdir(dest_dentry
, m
->mnt_root
)) {
198 mnt_set_mountpoint(m
, dest_dentry
, child
);
199 list_add_tail(&child
->mnt_hash
, tree_list
);
202 * This can happen if the parent mount was bind mounted
203 * on some subdirectory of a shared/slave mount.
205 list_add_tail(&child
->mnt_hash
, &tmp_list
);
208 prev_src_mnt
= child
;
211 spin_lock(&vfsmount_lock
);
212 while (!list_empty(&tmp_list
)) {
213 child
= list_entry(tmp_list
.next
, struct vfsmount
, mnt_hash
);
214 list_del_init(&child
->mnt_hash
);
215 umount_tree(child
, 0, &umount_list
);
217 spin_unlock(&vfsmount_lock
);
218 release_mounts(&umount_list
);
223 * return true if the refcount is greater than count
225 static inline int do_refcount_check(struct vfsmount
*mnt
, int count
)
227 int mycount
= atomic_read(&mnt
->mnt_count
);
228 return (mycount
> count
);
232 * check if the mount 'mnt' can be unmounted successfully.
233 * @mnt: the mount to be checked for unmount
234 * NOTE: unmounting 'mnt' would naturally propagate to all
235 * other mounts its parent propagates to.
236 * Check if any of these mounts that **do not have submounts**
237 * have more references than 'refcnt'. If so return busy.
239 int propagate_mount_busy(struct vfsmount
*mnt
, int refcnt
)
241 struct vfsmount
*m
, *child
;
242 struct vfsmount
*parent
= mnt
->mnt_parent
;
246 return do_refcount_check(mnt
, refcnt
);
249 * quickly check if the current mount can be unmounted.
250 * If not, we don't have to go checking for all other
253 if (!list_empty(&mnt
->mnt_mounts
) || do_refcount_check(mnt
, refcnt
))
256 for (m
= propagation_next(parent
, parent
); m
;
257 m
= propagation_next(m
, parent
)) {
258 child
= __lookup_mnt(m
, mnt
->mnt_mountpoint
, 0);
259 if (child
&& list_empty(&child
->mnt_mounts
) &&
260 (ret
= do_refcount_check(child
, 1)))
267 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
268 * parent propagates to.
270 static void __propagate_umount(struct vfsmount
*mnt
)
272 struct vfsmount
*parent
= mnt
->mnt_parent
;
275 BUG_ON(parent
== mnt
);
277 for (m
= propagation_next(parent
, parent
); m
;
278 m
= propagation_next(m
, parent
)) {
280 struct vfsmount
*child
= __lookup_mnt(m
,
281 mnt
->mnt_mountpoint
, 0);
283 * umount the child only if the child has no
286 if (child
&& list_empty(&child
->mnt_mounts
)) {
287 list_del(&child
->mnt_hash
);
288 list_add_tail(&child
->mnt_hash
, &mnt
->mnt_hash
);
294 * collect all mounts that receive propagation from the mount in @list,
295 * and return these additional mounts in the same list.
296 * @list: the list of mounts to be unmounted.
298 int propagate_umount(struct list_head
*list
)
300 struct vfsmount
*mnt
;
302 list_for_each_entry(mnt
, list
, mnt_hash
)
303 __propagate_umount(mnt
);
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