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Commit | Line | Data |
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07b20889 RP |
1 | /* |
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 | */ | |
6b3286ed | 9 | #include <linux/mnt_namespace.h> |
07b20889 RP |
10 | #include <linux/mount.h> |
11 | #include <linux/fs.h> | |
6d59e7f5 | 12 | #include "internal.h" |
07b20889 RP |
13 | #include "pnode.h" |
14 | ||
03e06e68 RP |
15 | /* return the next shared peer mount of @p */ |
16 | static inline struct vfsmount *next_peer(struct vfsmount *p) | |
17 | { | |
18 | return list_entry(p->mnt_share.next, struct vfsmount, mnt_share); | |
19 | } | |
20 | ||
5afe0022 RP |
21 | static inline struct vfsmount *first_slave(struct vfsmount *p) |
22 | { | |
23 | return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave); | |
24 | } | |
25 | ||
26 | static inline struct vfsmount *next_slave(struct vfsmount *p) | |
27 | { | |
28 | return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave); | |
29 | } | |
30 | ||
a58b0eb8 RP |
31 | static int do_make_slave(struct vfsmount *mnt) |
32 | { | |
33 | struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master; | |
34 | struct vfsmount *slave_mnt; | |
35 | ||
36 | /* | |
37 | * slave 'mnt' to a peer mount that has the | |
38 | * same root dentry. If none is available than | |
39 | * slave it to anything that is available. | |
40 | */ | |
41 | while ((peer_mnt = next_peer(peer_mnt)) != mnt && | |
42 | peer_mnt->mnt_root != mnt->mnt_root) ; | |
43 | ||
44 | if (peer_mnt == mnt) { | |
45 | peer_mnt = next_peer(mnt); | |
46 | if (peer_mnt == mnt) | |
47 | peer_mnt = NULL; | |
48 | } | |
719f5d7f MS |
49 | if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share)) |
50 | mnt_release_group_id(mnt); | |
51 | ||
a58b0eb8 | 52 | list_del_init(&mnt->mnt_share); |
719f5d7f | 53 | mnt->mnt_group_id = 0; |
a58b0eb8 RP |
54 | |
55 | if (peer_mnt) | |
56 | master = peer_mnt; | |
57 | ||
58 | if (master) { | |
59 | list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave) | |
60 | slave_mnt->mnt_master = master; | |
1bfba4e8 | 61 | list_move(&mnt->mnt_slave, &master->mnt_slave_list); |
a58b0eb8 RP |
62 | list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev); |
63 | INIT_LIST_HEAD(&mnt->mnt_slave_list); | |
64 | } else { | |
65 | struct list_head *p = &mnt->mnt_slave_list; | |
66 | while (!list_empty(p)) { | |
b5e61818 | 67 | slave_mnt = list_first_entry(p, |
a58b0eb8 RP |
68 | struct vfsmount, mnt_slave); |
69 | list_del_init(&slave_mnt->mnt_slave); | |
70 | slave_mnt->mnt_master = NULL; | |
71 | } | |
72 | } | |
73 | mnt->mnt_master = master; | |
74 | CLEAR_MNT_SHARED(mnt); | |
a58b0eb8 RP |
75 | return 0; |
76 | } | |
77 | ||
07b20889 RP |
78 | void change_mnt_propagation(struct vfsmount *mnt, int type) |
79 | { | |
03e06e68 | 80 | if (type == MS_SHARED) { |
b90fa9ae | 81 | set_mnt_shared(mnt); |
a58b0eb8 RP |
82 | return; |
83 | } | |
84 | do_make_slave(mnt); | |
85 | if (type != MS_SLAVE) { | |
86 | list_del_init(&mnt->mnt_slave); | |
87 | mnt->mnt_master = NULL; | |
9676f0c6 RP |
88 | if (type == MS_UNBINDABLE) |
89 | mnt->mnt_flags |= MNT_UNBINDABLE; | |
0b03cfb2 AB |
90 | else |
91 | mnt->mnt_flags &= ~MNT_UNBINDABLE; | |
03e06e68 | 92 | } |
07b20889 | 93 | } |
b90fa9ae RP |
94 | |
95 | /* | |
96 | * get the next mount in the propagation tree. | |
97 | * @m: the mount seen last | |
98 | * @origin: the original mount from where the tree walk initiated | |
99 | */ | |
100 | static struct vfsmount *propagation_next(struct vfsmount *m, | |
101 | struct vfsmount *origin) | |
102 | { | |
5afe0022 RP |
103 | /* are there any slaves of this mount? */ |
104 | if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list)) | |
105 | return first_slave(m); | |
106 | ||
107 | while (1) { | |
108 | struct vfsmount *next; | |
109 | struct vfsmount *master = m->mnt_master; | |
110 | ||
bf066c7d | 111 | if (master == origin->mnt_master) { |
5afe0022 RP |
112 | next = next_peer(m); |
113 | return ((next == origin) ? NULL : next); | |
114 | } else if (m->mnt_slave.next != &master->mnt_slave_list) | |
115 | return next_slave(m); | |
116 | ||
117 | /* back at master */ | |
118 | m = master; | |
119 | } | |
120 | } | |
121 | ||
122 | /* | |
123 | * return the source mount to be used for cloning | |
124 | * | |
125 | * @dest the current destination mount | |
126 | * @last_dest the last seen destination mount | |
127 | * @last_src the last seen source mount | |
128 | * @type return CL_SLAVE if the new mount has to be | |
129 | * cloned as a slave. | |
130 | */ | |
131 | static struct vfsmount *get_source(struct vfsmount *dest, | |
132 | struct vfsmount *last_dest, | |
133 | struct vfsmount *last_src, | |
134 | int *type) | |
135 | { | |
136 | struct vfsmount *p_last_src = NULL; | |
137 | struct vfsmount *p_last_dest = NULL; | |
53b3531b | 138 | *type = CL_PROPAGATION; |
5afe0022 RP |
139 | |
140 | if (IS_MNT_SHARED(dest)) | |
141 | *type |= CL_MAKE_SHARED; | |
142 | ||
143 | while (last_dest != dest->mnt_master) { | |
144 | p_last_dest = last_dest; | |
145 | p_last_src = last_src; | |
146 | last_dest = last_dest->mnt_master; | |
147 | last_src = last_src->mnt_master; | |
148 | } | |
149 | ||
150 | if (p_last_dest) { | |
151 | do { | |
152 | p_last_dest = next_peer(p_last_dest); | |
153 | } while (IS_MNT_NEW(p_last_dest)); | |
154 | } | |
155 | ||
156 | if (dest != p_last_dest) { | |
157 | *type |= CL_SLAVE; | |
158 | return last_src; | |
159 | } else | |
160 | return p_last_src; | |
b90fa9ae RP |
161 | } |
162 | ||
163 | /* | |
164 | * mount 'source_mnt' under the destination 'dest_mnt' at | |
165 | * dentry 'dest_dentry'. And propagate that mount to | |
166 | * all the peer and slave mounts of 'dest_mnt'. | |
167 | * Link all the new mounts into a propagation tree headed at | |
168 | * source_mnt. Also link all the new mounts using ->mnt_list | |
169 | * headed at source_mnt's ->mnt_list | |
170 | * | |
171 | * @dest_mnt: destination mount. | |
172 | * @dest_dentry: destination dentry. | |
173 | * @source_mnt: source mount. | |
174 | * @tree_list : list of heads of trees to be attached. | |
175 | */ | |
176 | int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry, | |
177 | struct vfsmount *source_mnt, struct list_head *tree_list) | |
178 | { | |
179 | struct vfsmount *m, *child; | |
180 | int ret = 0; | |
181 | struct vfsmount *prev_dest_mnt = dest_mnt; | |
182 | struct vfsmount *prev_src_mnt = source_mnt; | |
183 | LIST_HEAD(tmp_list); | |
184 | LIST_HEAD(umount_list); | |
185 | ||
186 | for (m = propagation_next(dest_mnt, dest_mnt); m; | |
187 | m = propagation_next(m, dest_mnt)) { | |
5afe0022 RP |
188 | int type; |
189 | struct vfsmount *source; | |
b90fa9ae RP |
190 | |
191 | if (IS_MNT_NEW(m)) | |
192 | continue; | |
193 | ||
5afe0022 | 194 | source = get_source(m, prev_dest_mnt, prev_src_mnt, &type); |
b90fa9ae | 195 | |
5afe0022 | 196 | if (!(child = copy_tree(source, source->mnt_root, type))) { |
b90fa9ae RP |
197 | ret = -ENOMEM; |
198 | list_splice(tree_list, tmp_list.prev); | |
199 | goto out; | |
200 | } | |
201 | ||
202 | if (is_subdir(dest_dentry, m->mnt_root)) { | |
203 | mnt_set_mountpoint(m, dest_dentry, child); | |
204 | list_add_tail(&child->mnt_hash, tree_list); | |
205 | } else { | |
206 | /* | |
207 | * This can happen if the parent mount was bind mounted | |
208 | * on some subdirectory of a shared/slave mount. | |
209 | */ | |
210 | list_add_tail(&child->mnt_hash, &tmp_list); | |
211 | } | |
212 | prev_dest_mnt = m; | |
213 | prev_src_mnt = child; | |
214 | } | |
215 | out: | |
216 | spin_lock(&vfsmount_lock); | |
217 | while (!list_empty(&tmp_list)) { | |
4e1b36fb | 218 | child = list_first_entry(&tmp_list, struct vfsmount, mnt_hash); |
a05964f3 | 219 | umount_tree(child, 0, &umount_list); |
b90fa9ae RP |
220 | } |
221 | spin_unlock(&vfsmount_lock); | |
222 | release_mounts(&umount_list); | |
223 | return ret; | |
224 | } | |
a05964f3 RP |
225 | |
226 | /* | |
227 | * return true if the refcount is greater than count | |
228 | */ | |
229 | static inline int do_refcount_check(struct vfsmount *mnt, int count) | |
230 | { | |
7c4b93d8 | 231 | int mycount = atomic_read(&mnt->mnt_count) - mnt->mnt_ghosts; |
a05964f3 RP |
232 | return (mycount > count); |
233 | } | |
234 | ||
235 | /* | |
236 | * check if the mount 'mnt' can be unmounted successfully. | |
237 | * @mnt: the mount to be checked for unmount | |
238 | * NOTE: unmounting 'mnt' would naturally propagate to all | |
239 | * other mounts its parent propagates to. | |
240 | * Check if any of these mounts that **do not have submounts** | |
241 | * have more references than 'refcnt'. If so return busy. | |
242 | */ | |
243 | int propagate_mount_busy(struct vfsmount *mnt, int refcnt) | |
244 | { | |
245 | struct vfsmount *m, *child; | |
246 | struct vfsmount *parent = mnt->mnt_parent; | |
247 | int ret = 0; | |
248 | ||
249 | if (mnt == parent) | |
250 | return do_refcount_check(mnt, refcnt); | |
251 | ||
252 | /* | |
253 | * quickly check if the current mount can be unmounted. | |
254 | * If not, we don't have to go checking for all other | |
255 | * mounts | |
256 | */ | |
257 | if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt)) | |
258 | return 1; | |
259 | ||
260 | for (m = propagation_next(parent, parent); m; | |
261 | m = propagation_next(m, parent)) { | |
262 | child = __lookup_mnt(m, mnt->mnt_mountpoint, 0); | |
263 | if (child && list_empty(&child->mnt_mounts) && | |
264 | (ret = do_refcount_check(child, 1))) | |
265 | break; | |
266 | } | |
267 | return ret; | |
268 | } | |
269 | ||
270 | /* | |
271 | * NOTE: unmounting 'mnt' naturally propagates to all other mounts its | |
272 | * parent propagates to. | |
273 | */ | |
274 | static void __propagate_umount(struct vfsmount *mnt) | |
275 | { | |
276 | struct vfsmount *parent = mnt->mnt_parent; | |
277 | struct vfsmount *m; | |
278 | ||
279 | BUG_ON(parent == mnt); | |
280 | ||
281 | for (m = propagation_next(parent, parent); m; | |
282 | m = propagation_next(m, parent)) { | |
283 | ||
284 | struct vfsmount *child = __lookup_mnt(m, | |
285 | mnt->mnt_mountpoint, 0); | |
286 | /* | |
287 | * umount the child only if the child has no | |
288 | * other children | |
289 | */ | |
1bfba4e8 AM |
290 | if (child && list_empty(&child->mnt_mounts)) |
291 | list_move_tail(&child->mnt_hash, &mnt->mnt_hash); | |
a05964f3 RP |
292 | } |
293 | } | |
294 | ||
295 | /* | |
296 | * collect all mounts that receive propagation from the mount in @list, | |
297 | * and return these additional mounts in the same list. | |
298 | * @list: the list of mounts to be unmounted. | |
299 | */ | |
300 | int propagate_umount(struct list_head *list) | |
301 | { | |
302 | struct vfsmount *mnt; | |
303 | ||
304 | list_for_each_entry(mnt, list, mnt_hash) | |
305 | __propagate_umount(mnt); | |
306 | return 0; | |
307 | } |