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Ram Pai07b20882005-11-07 17:19:07 -05001/*
2 * linux/fs/pnode.c
3 *
4 * (C) Copyright IBM Corporation 2005.
5 * Released under GPL v2.
6 * Author : Ram Pai (linuxram@us.ibm.com)
7 *
8 */
Kirill Korotaev6b3286e2006-12-08 02:37:56 -08009#include <linux/mnt_namespace.h>
Ram Pai07b20882005-11-07 17:19:07 -050010#include <linux/mount.h>
11#include <linux/fs.h>
12#include "pnode.h"
13
Ram Pai03e06e62005-11-07 17:19:33 -050014/* return the next shared peer mount of @p */
15static inline struct vfsmount *next_peer(struct vfsmount *p)
16{
17 return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);
18}
19
Ram Pai5afe0022005-11-07 17:21:01 -050020static inline struct vfsmount *first_slave(struct vfsmount *p)
21{
22 return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave);
23}
24
25static inline struct vfsmount *next_slave(struct vfsmount *p)
26{
27 return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);
28}
29
Ram Paia58b0eb2005-11-07 17:20:48 -050030static int do_make_slave(struct vfsmount *mnt)
31{
32 struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
33 struct vfsmount *slave_mnt;
34
35 /*
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.
39 */
40 while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
41 peer_mnt->mnt_root != mnt->mnt_root) ;
42
43 if (peer_mnt == mnt) {
44 peer_mnt = next_peer(mnt);
45 if (peer_mnt == mnt)
46 peer_mnt = NULL;
47 }
48 list_del_init(&mnt->mnt_share);
49
50 if (peer_mnt)
51 master = peer_mnt;
52
53 if (master) {
54 list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
55 slave_mnt->mnt_master = master;
Akinobu Mita1bfba4e2006-06-26 00:24:40 -070056 list_move(&mnt->mnt_slave, &master->mnt_slave_list);
Ram Paia58b0eb2005-11-07 17:20:48 -050057 list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
58 INIT_LIST_HEAD(&mnt->mnt_slave_list);
59 } else {
60 struct list_head *p = &mnt->mnt_slave_list;
61 while (!list_empty(p)) {
Pavel Emelianovb5e61812007-05-08 00:30:19 -070062 slave_mnt = list_first_entry(p,
Ram Paia58b0eb2005-11-07 17:20:48 -050063 struct vfsmount, mnt_slave);
64 list_del_init(&slave_mnt->mnt_slave);
65 slave_mnt->mnt_master = NULL;
66 }
67 }
68 mnt->mnt_master = master;
69 CLEAR_MNT_SHARED(mnt);
70 INIT_LIST_HEAD(&mnt->mnt_slave_list);
71 return 0;
72}
73
Ram Pai07b20882005-11-07 17:19:07 -050074void change_mnt_propagation(struct vfsmount *mnt, int type)
75{
Ram Pai03e06e62005-11-07 17:19:33 -050076 if (type == MS_SHARED) {
Ram Paib90fa9a2005-11-07 17:19:50 -050077 set_mnt_shared(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -050078 return;
79 }
80 do_make_slave(mnt);
81 if (type != MS_SLAVE) {
82 list_del_init(&mnt->mnt_slave);
83 mnt->mnt_master = NULL;
Ram Pai9676f0c2005-11-07 17:21:20 -050084 if (type == MS_UNBINDABLE)
85 mnt->mnt_flags |= MNT_UNBINDABLE;
Andries E. Brouwer0b03cfb2008-02-06 01:36:32 -080086 else
87 mnt->mnt_flags &= ~MNT_UNBINDABLE;
Ram Pai03e06e62005-11-07 17:19:33 -050088 }
Ram Pai07b20882005-11-07 17:19:07 -050089}
Ram Paib90fa9a2005-11-07 17:19:50 -050090
91/*
92 * get the next mount in the propagation tree.
93 * @m: the mount seen last
94 * @origin: the original mount from where the tree walk initiated
95 */
96static struct vfsmount *propagation_next(struct vfsmount *m,
97 struct vfsmount *origin)
98{
Ram Pai5afe0022005-11-07 17:21:01 -050099 /* are there any slaves of this mount? */
100 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
101 return first_slave(m);
102
103 while (1) {
104 struct vfsmount *next;
105 struct vfsmount *master = m->mnt_master;
106
Miklos Szeredibf066c72006-01-08 01:03:19 -0800107 if (master == origin->mnt_master) {
Ram Pai5afe0022005-11-07 17:21:01 -0500108 next = next_peer(m);
109 return ((next == origin) ? NULL : next);
110 } else if (m->mnt_slave.next != &master->mnt_slave_list)
111 return next_slave(m);
112
113 /* back at master */
114 m = master;
115 }
116}
117
118/*
119 * return the source mount to be used for cloning
120 *
121 * @dest the current destination mount
122 * @last_dest the last seen destination mount
123 * @last_src the last seen source mount
124 * @type return CL_SLAVE if the new mount has to be
125 * cloned as a slave.
126 */
127static struct vfsmount *get_source(struct vfsmount *dest,
128 struct vfsmount *last_dest,
129 struct vfsmount *last_src,
130 int *type)
131{
132 struct vfsmount *p_last_src = NULL;
133 struct vfsmount *p_last_dest = NULL;
Alexey Dobriyan53b35312006-03-24 03:16:13 -0800134 *type = CL_PROPAGATION;
Ram Pai5afe0022005-11-07 17:21:01 -0500135
136 if (IS_MNT_SHARED(dest))
137 *type |= CL_MAKE_SHARED;
138
139 while (last_dest != dest->mnt_master) {
140 p_last_dest = last_dest;
141 p_last_src = last_src;
142 last_dest = last_dest->mnt_master;
143 last_src = last_src->mnt_master;
144 }
145
146 if (p_last_dest) {
147 do {
148 p_last_dest = next_peer(p_last_dest);
149 } while (IS_MNT_NEW(p_last_dest));
150 }
151
152 if (dest != p_last_dest) {
153 *type |= CL_SLAVE;
154 return last_src;
155 } else
156 return p_last_src;
Ram Paib90fa9a2005-11-07 17:19:50 -0500157}
158
159/*
160 * mount 'source_mnt' under the destination 'dest_mnt' at
161 * dentry 'dest_dentry'. And propagate that mount to
162 * all the peer and slave mounts of 'dest_mnt'.
163 * Link all the new mounts into a propagation tree headed at
164 * source_mnt. Also link all the new mounts using ->mnt_list
165 * headed at source_mnt's ->mnt_list
166 *
167 * @dest_mnt: destination mount.
168 * @dest_dentry: destination dentry.
169 * @source_mnt: source mount.
170 * @tree_list : list of heads of trees to be attached.
171 */
172int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry,
173 struct vfsmount *source_mnt, struct list_head *tree_list)
174{
175 struct vfsmount *m, *child;
176 int ret = 0;
177 struct vfsmount *prev_dest_mnt = dest_mnt;
178 struct vfsmount *prev_src_mnt = source_mnt;
179 LIST_HEAD(tmp_list);
180 LIST_HEAD(umount_list);
181
182 for (m = propagation_next(dest_mnt, dest_mnt); m;
183 m = propagation_next(m, dest_mnt)) {
Ram Pai5afe0022005-11-07 17:21:01 -0500184 int type;
185 struct vfsmount *source;
Ram Paib90fa9a2005-11-07 17:19:50 -0500186
187 if (IS_MNT_NEW(m))
188 continue;
189
Ram Pai5afe0022005-11-07 17:21:01 -0500190 source = get_source(m, prev_dest_mnt, prev_src_mnt, &type);
Ram Paib90fa9a2005-11-07 17:19:50 -0500191
Ram Pai5afe0022005-11-07 17:21:01 -0500192 if (!(child = copy_tree(source, source->mnt_root, type))) {
Ram Paib90fa9a2005-11-07 17:19:50 -0500193 ret = -ENOMEM;
194 list_splice(tree_list, tmp_list.prev);
195 goto out;
196 }
197
198 if (is_subdir(dest_dentry, m->mnt_root)) {
199 mnt_set_mountpoint(m, dest_dentry, child);
200 list_add_tail(&child->mnt_hash, tree_list);
201 } else {
202 /*
203 * This can happen if the parent mount was bind mounted
204 * on some subdirectory of a shared/slave mount.
205 */
206 list_add_tail(&child->mnt_hash, &tmp_list);
207 }
208 prev_dest_mnt = m;
209 prev_src_mnt = child;
210 }
211out:
212 spin_lock(&vfsmount_lock);
213 while (!list_empty(&tmp_list)) {
214 child = list_entry(tmp_list.next, struct vfsmount, mnt_hash);
215 list_del_init(&child->mnt_hash);
Ram Paia05964f2005-11-07 17:20:17 -0500216 umount_tree(child, 0, &umount_list);
Ram Paib90fa9a2005-11-07 17:19:50 -0500217 }
218 spin_unlock(&vfsmount_lock);
219 release_mounts(&umount_list);
220 return ret;
221}
Ram Paia05964f2005-11-07 17:20:17 -0500222
223/*
224 * return true if the refcount is greater than count
225 */
226static inline int do_refcount_check(struct vfsmount *mnt, int count)
227{
228 int mycount = atomic_read(&mnt->mnt_count);
229 return (mycount > count);
230}
231
232/*
233 * check if the mount 'mnt' can be unmounted successfully.
234 * @mnt: the mount to be checked for unmount
235 * NOTE: unmounting 'mnt' would naturally propagate to all
236 * other mounts its parent propagates to.
237 * Check if any of these mounts that **do not have submounts**
238 * have more references than 'refcnt'. If so return busy.
239 */
240int propagate_mount_busy(struct vfsmount *mnt, int refcnt)
241{
242 struct vfsmount *m, *child;
243 struct vfsmount *parent = mnt->mnt_parent;
244 int ret = 0;
245
246 if (mnt == parent)
247 return do_refcount_check(mnt, refcnt);
248
249 /*
250 * quickly check if the current mount can be unmounted.
251 * If not, we don't have to go checking for all other
252 * mounts
253 */
254 if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
255 return 1;
256
257 for (m = propagation_next(parent, parent); m;
258 m = propagation_next(m, parent)) {
259 child = __lookup_mnt(m, mnt->mnt_mountpoint, 0);
260 if (child && list_empty(&child->mnt_mounts) &&
261 (ret = do_refcount_check(child, 1)))
262 break;
263 }
264 return ret;
265}
266
267/*
268 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
269 * parent propagates to.
270 */
271static void __propagate_umount(struct vfsmount *mnt)
272{
273 struct vfsmount *parent = mnt->mnt_parent;
274 struct vfsmount *m;
275
276 BUG_ON(parent == mnt);
277
278 for (m = propagation_next(parent, parent); m;
279 m = propagation_next(m, parent)) {
280
281 struct vfsmount *child = __lookup_mnt(m,
282 mnt->mnt_mountpoint, 0);
283 /*
284 * umount the child only if the child has no
285 * other children
286 */
Akinobu Mita1bfba4e2006-06-26 00:24:40 -0700287 if (child && list_empty(&child->mnt_mounts))
288 list_move_tail(&child->mnt_hash, &mnt->mnt_hash);
Ram Paia05964f2005-11-07 17:20:17 -0500289 }
290}
291
292/*
293 * collect all mounts that receive propagation from the mount in @list,
294 * and return these additional mounts in the same list.
295 * @list: the list of mounts to be unmounted.
296 */
297int propagate_umount(struct list_head *list)
298{
299 struct vfsmount *mnt;
300
301 list_for_each_entry(mnt, list, mnt_hash)
302 __propagate_umount(mnt);
303 return 0;
304}