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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 | ||
97e7e0f7 MS |
31 | static struct vfsmount *get_peer_under_root(struct vfsmount *mnt, |
32 | struct mnt_namespace *ns, | |
33 | const struct path *root) | |
34 | { | |
35 | struct vfsmount *m = mnt; | |
36 | ||
37 | do { | |
38 | /* Check the namespace first for optimization */ | |
39 | if (m->mnt_ns == ns && is_path_reachable(m, m->mnt_root, root)) | |
40 | return m; | |
41 | ||
42 | m = next_peer(m); | |
43 | } while (m != mnt); | |
44 | ||
45 | return NULL; | |
46 | } | |
47 | ||
48 | /* | |
49 | * Get ID of closest dominating peer group having a representative | |
50 | * under the given root. | |
51 | * | |
52 | * Caller must hold namespace_sem | |
53 | */ | |
54 | int get_dominating_id(struct vfsmount *mnt, const struct path *root) | |
55 | { | |
56 | struct vfsmount *m; | |
57 | ||
58 | for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) { | |
59 | struct vfsmount *d = get_peer_under_root(m, mnt->mnt_ns, root); | |
60 | if (d) | |
61 | return d->mnt_group_id; | |
62 | } | |
63 | ||
64 | return 0; | |
65 | } | |
66 | ||
a58b0eb8 RP |
67 | static int do_make_slave(struct vfsmount *mnt) |
68 | { | |
69 | struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master; | |
70 | struct vfsmount *slave_mnt; | |
71 | ||
72 | /* | |
73 | * slave 'mnt' to a peer mount that has the | |
796a6b52 | 74 | * same root dentry. If none is available then |
a58b0eb8 RP |
75 | * slave it to anything that is available. |
76 | */ | |
77 | while ((peer_mnt = next_peer(peer_mnt)) != mnt && | |
78 | peer_mnt->mnt_root != mnt->mnt_root) ; | |
79 | ||
80 | if (peer_mnt == mnt) { | |
81 | peer_mnt = next_peer(mnt); | |
82 | if (peer_mnt == mnt) | |
83 | peer_mnt = NULL; | |
84 | } | |
719f5d7f | 85 | if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share)) |
4b8b21f4 | 86 | mnt_release_group_id(real_mount(mnt)); |
719f5d7f | 87 | |
a58b0eb8 | 88 | list_del_init(&mnt->mnt_share); |
719f5d7f | 89 | mnt->mnt_group_id = 0; |
a58b0eb8 RP |
90 | |
91 | if (peer_mnt) | |
92 | master = peer_mnt; | |
93 | ||
94 | if (master) { | |
95 | list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave) | |
96 | slave_mnt->mnt_master = master; | |
1bfba4e8 | 97 | list_move(&mnt->mnt_slave, &master->mnt_slave_list); |
a58b0eb8 RP |
98 | list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev); |
99 | INIT_LIST_HEAD(&mnt->mnt_slave_list); | |
100 | } else { | |
101 | struct list_head *p = &mnt->mnt_slave_list; | |
102 | while (!list_empty(p)) { | |
b5e61818 | 103 | slave_mnt = list_first_entry(p, |
a58b0eb8 RP |
104 | struct vfsmount, mnt_slave); |
105 | list_del_init(&slave_mnt->mnt_slave); | |
106 | slave_mnt->mnt_master = NULL; | |
107 | } | |
108 | } | |
109 | mnt->mnt_master = master; | |
110 | CLEAR_MNT_SHARED(mnt); | |
a58b0eb8 RP |
111 | return 0; |
112 | } | |
113 | ||
99b7db7b NP |
114 | /* |
115 | * vfsmount lock must be held for write | |
116 | */ | |
0f0afb1d | 117 | void change_mnt_propagation(struct mount *mnt, int type) |
07b20889 | 118 | { |
03e06e68 | 119 | if (type == MS_SHARED) { |
b90fa9ae | 120 | set_mnt_shared(mnt); |
a58b0eb8 RP |
121 | return; |
122 | } | |
0f0afb1d | 123 | do_make_slave(&mnt->mnt); |
a58b0eb8 | 124 | if (type != MS_SLAVE) { |
0f0afb1d AV |
125 | list_del_init(&mnt->mnt.mnt_slave); |
126 | mnt->mnt.mnt_master = NULL; | |
9676f0c6 | 127 | if (type == MS_UNBINDABLE) |
0f0afb1d | 128 | mnt->mnt.mnt_flags |= MNT_UNBINDABLE; |
0b03cfb2 | 129 | else |
0f0afb1d | 130 | mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE; |
03e06e68 | 131 | } |
07b20889 | 132 | } |
b90fa9ae RP |
133 | |
134 | /* | |
135 | * get the next mount in the propagation tree. | |
136 | * @m: the mount seen last | |
137 | * @origin: the original mount from where the tree walk initiated | |
796a6b52 AV |
138 | * |
139 | * Note that peer groups form contiguous segments of slave lists. | |
140 | * We rely on that in get_source() to be able to find out if | |
141 | * vfsmount found while iterating with propagation_next() is | |
142 | * a peer of one we'd found earlier. | |
b90fa9ae RP |
143 | */ |
144 | static struct vfsmount *propagation_next(struct vfsmount *m, | |
145 | struct vfsmount *origin) | |
146 | { | |
5afe0022 RP |
147 | /* are there any slaves of this mount? */ |
148 | if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list)) | |
149 | return first_slave(m); | |
150 | ||
151 | while (1) { | |
152 | struct vfsmount *next; | |
153 | struct vfsmount *master = m->mnt_master; | |
154 | ||
bf066c7d | 155 | if (master == origin->mnt_master) { |
5afe0022 RP |
156 | next = next_peer(m); |
157 | return ((next == origin) ? NULL : next); | |
158 | } else if (m->mnt_slave.next != &master->mnt_slave_list) | |
159 | return next_slave(m); | |
160 | ||
161 | /* back at master */ | |
162 | m = master; | |
163 | } | |
164 | } | |
165 | ||
166 | /* | |
167 | * return the source mount to be used for cloning | |
168 | * | |
169 | * @dest the current destination mount | |
170 | * @last_dest the last seen destination mount | |
171 | * @last_src the last seen source mount | |
172 | * @type return CL_SLAVE if the new mount has to be | |
173 | * cloned as a slave. | |
174 | */ | |
175 | static struct vfsmount *get_source(struct vfsmount *dest, | |
176 | struct vfsmount *last_dest, | |
177 | struct vfsmount *last_src, | |
178 | int *type) | |
179 | { | |
180 | struct vfsmount *p_last_src = NULL; | |
181 | struct vfsmount *p_last_dest = NULL; | |
5afe0022 RP |
182 | |
183 | while (last_dest != dest->mnt_master) { | |
184 | p_last_dest = last_dest; | |
185 | p_last_src = last_src; | |
186 | last_dest = last_dest->mnt_master; | |
187 | last_src = last_src->mnt_master; | |
188 | } | |
189 | ||
190 | if (p_last_dest) { | |
191 | do { | |
192 | p_last_dest = next_peer(p_last_dest); | |
193 | } while (IS_MNT_NEW(p_last_dest)); | |
796a6b52 AV |
194 | /* is that a peer of the earlier? */ |
195 | if (dest == p_last_dest) { | |
196 | *type = CL_MAKE_SHARED; | |
197 | return p_last_src; | |
198 | } | |
5afe0022 | 199 | } |
796a6b52 AV |
200 | /* slave of the earlier, then */ |
201 | *type = CL_SLAVE; | |
202 | /* beginning of peer group among the slaves? */ | |
203 | if (IS_MNT_SHARED(dest)) | |
204 | *type |= CL_MAKE_SHARED; | |
205 | return last_src; | |
b90fa9ae RP |
206 | } |
207 | ||
208 | /* | |
209 | * mount 'source_mnt' under the destination 'dest_mnt' at | |
210 | * dentry 'dest_dentry'. And propagate that mount to | |
211 | * all the peer and slave mounts of 'dest_mnt'. | |
212 | * Link all the new mounts into a propagation tree headed at | |
213 | * source_mnt. Also link all the new mounts using ->mnt_list | |
214 | * headed at source_mnt's ->mnt_list | |
215 | * | |
216 | * @dest_mnt: destination mount. | |
217 | * @dest_dentry: destination dentry. | |
218 | * @source_mnt: source mount. | |
219 | * @tree_list : list of heads of trees to be attached. | |
220 | */ | |
221 | int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry, | |
222 | struct vfsmount *source_mnt, struct list_head *tree_list) | |
223 | { | |
cb338d06 AV |
224 | struct vfsmount *m; |
225 | struct mount *child; | |
b90fa9ae RP |
226 | int ret = 0; |
227 | struct vfsmount *prev_dest_mnt = dest_mnt; | |
228 | struct vfsmount *prev_src_mnt = source_mnt; | |
229 | LIST_HEAD(tmp_list); | |
230 | LIST_HEAD(umount_list); | |
231 | ||
232 | for (m = propagation_next(dest_mnt, dest_mnt); m; | |
233 | m = propagation_next(m, dest_mnt)) { | |
5afe0022 RP |
234 | int type; |
235 | struct vfsmount *source; | |
b90fa9ae RP |
236 | |
237 | if (IS_MNT_NEW(m)) | |
238 | continue; | |
239 | ||
5afe0022 | 240 | source = get_source(m, prev_dest_mnt, prev_src_mnt, &type); |
b90fa9ae | 241 | |
5afe0022 | 242 | if (!(child = copy_tree(source, source->mnt_root, type))) { |
b90fa9ae RP |
243 | ret = -ENOMEM; |
244 | list_splice(tree_list, tmp_list.prev); | |
245 | goto out; | |
246 | } | |
247 | ||
248 | if (is_subdir(dest_dentry, m->mnt_root)) { | |
cb338d06 | 249 | mnt_set_mountpoint(m, dest_dentry, &child->mnt); |
1b8e5564 | 250 | list_add_tail(&child->mnt_hash, tree_list); |
b90fa9ae RP |
251 | } else { |
252 | /* | |
253 | * This can happen if the parent mount was bind mounted | |
254 | * on some subdirectory of a shared/slave mount. | |
255 | */ | |
1b8e5564 | 256 | list_add_tail(&child->mnt_hash, &tmp_list); |
b90fa9ae RP |
257 | } |
258 | prev_dest_mnt = m; | |
cb338d06 | 259 | prev_src_mnt = &child->mnt; |
b90fa9ae RP |
260 | } |
261 | out: | |
99b7db7b | 262 | br_write_lock(vfsmount_lock); |
b90fa9ae | 263 | while (!list_empty(&tmp_list)) { |
1b8e5564 | 264 | child = list_first_entry(&tmp_list, struct mount, mnt_hash); |
cb338d06 | 265 | umount_tree(&child->mnt, 0, &umount_list); |
b90fa9ae | 266 | } |
99b7db7b | 267 | br_write_unlock(vfsmount_lock); |
b90fa9ae RP |
268 | release_mounts(&umount_list); |
269 | return ret; | |
270 | } | |
a05964f3 RP |
271 | |
272 | /* | |
273 | * return true if the refcount is greater than count | |
274 | */ | |
275 | static inline int do_refcount_check(struct vfsmount *mnt, int count) | |
276 | { | |
b3e19d92 | 277 | int mycount = mnt_get_count(mnt) - mnt->mnt_ghosts; |
a05964f3 RP |
278 | return (mycount > count); |
279 | } | |
280 | ||
281 | /* | |
282 | * check if the mount 'mnt' can be unmounted successfully. | |
283 | * @mnt: the mount to be checked for unmount | |
284 | * NOTE: unmounting 'mnt' would naturally propagate to all | |
285 | * other mounts its parent propagates to. | |
286 | * Check if any of these mounts that **do not have submounts** | |
287 | * have more references than 'refcnt'. If so return busy. | |
99b7db7b | 288 | * |
b3e19d92 | 289 | * vfsmount lock must be held for write |
a05964f3 RP |
290 | */ |
291 | int propagate_mount_busy(struct vfsmount *mnt, int refcnt) | |
292 | { | |
c7105365 AV |
293 | struct vfsmount *m; |
294 | struct mount *child; | |
a05964f3 RP |
295 | struct vfsmount *parent = mnt->mnt_parent; |
296 | int ret = 0; | |
297 | ||
298 | if (mnt == parent) | |
299 | return do_refcount_check(mnt, refcnt); | |
300 | ||
301 | /* | |
302 | * quickly check if the current mount can be unmounted. | |
303 | * If not, we don't have to go checking for all other | |
304 | * mounts | |
305 | */ | |
306 | if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt)) | |
307 | return 1; | |
308 | ||
309 | for (m = propagation_next(parent, parent); m; | |
310 | m = propagation_next(m, parent)) { | |
311 | child = __lookup_mnt(m, mnt->mnt_mountpoint, 0); | |
c7105365 AV |
312 | if (child && list_empty(&child->mnt.mnt_mounts) && |
313 | (ret = do_refcount_check(&child->mnt, 1))) | |
a05964f3 RP |
314 | break; |
315 | } | |
316 | return ret; | |
317 | } | |
318 | ||
319 | /* | |
320 | * NOTE: unmounting 'mnt' naturally propagates to all other mounts its | |
321 | * parent propagates to. | |
322 | */ | |
61ef47b1 | 323 | static void __propagate_umount(struct mount *mnt) |
a05964f3 | 324 | { |
61ef47b1 | 325 | struct vfsmount *parent = mnt->mnt.mnt_parent; |
a05964f3 RP |
326 | struct vfsmount *m; |
327 | ||
61ef47b1 | 328 | BUG_ON(parent == &mnt->mnt); |
a05964f3 RP |
329 | |
330 | for (m = propagation_next(parent, parent); m; | |
331 | m = propagation_next(m, parent)) { | |
332 | ||
c7105365 | 333 | struct mount *child = __lookup_mnt(m, |
61ef47b1 | 334 | mnt->mnt.mnt_mountpoint, 0); |
a05964f3 RP |
335 | /* |
336 | * umount the child only if the child has no | |
337 | * other children | |
338 | */ | |
c7105365 | 339 | if (child && list_empty(&child->mnt.mnt_mounts)) |
1b8e5564 | 340 | list_move_tail(&child->mnt_hash, &mnt->mnt_hash); |
a05964f3 RP |
341 | } |
342 | } | |
343 | ||
344 | /* | |
345 | * collect all mounts that receive propagation from the mount in @list, | |
346 | * and return these additional mounts in the same list. | |
347 | * @list: the list of mounts to be unmounted. | |
99b7db7b NP |
348 | * |
349 | * vfsmount lock must be held for write | |
a05964f3 RP |
350 | */ |
351 | int propagate_umount(struct list_head *list) | |
352 | { | |
61ef47b1 | 353 | struct mount *mnt; |
a05964f3 | 354 | |
1b8e5564 | 355 | list_for_each_entry(mnt, list, mnt_hash) |
a05964f3 RP |
356 | __propagate_umount(mnt); |
357 | return 0; | |
358 | } |