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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 */
9#include <linux/mnt_namespace.h>
10#include <linux/mount.h>
11#include <linux/fs.h>
12#include "internal.h"
13#include "pnode.h"
14
15/* return the next shared peer mount of @p */
16static inline struct vfsmount *next_peer(struct vfsmount *p)
17{
18 return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);
19}
20
21static inline struct vfsmount *first_slave(struct vfsmount *p)
22{
23 return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave);
24}
25
26static inline struct vfsmount *next_slave(struct vfsmount *p)
27{
28 return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);
29}
30
31/*
32 * Return true if path is reachable from root
33 *
34 * namespace_sem is held, and mnt is attached
35 */
36static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,
37 const struct path *root)
38{
39 while (mnt != root->mnt && mnt->mnt_parent != mnt) {
40 dentry = mnt->mnt_mountpoint;
41 mnt = mnt->mnt_parent;
42 }
43 return mnt == root->mnt && is_subdir(dentry, root->dentry);
44}
45
46static struct vfsmount *get_peer_under_root(struct vfsmount *mnt,
47 struct mnt_namespace *ns,
48 const struct path *root)
49{
50 struct vfsmount *m = mnt;
51
52 do {
53 /* Check the namespace first for optimization */
54 if (m->mnt_ns == ns && is_path_reachable(m, m->mnt_root, root))
55 return m;
56
57 m = next_peer(m);
58 } while (m != mnt);
59
60 return NULL;
61}
62
63/*
64 * Get ID of closest dominating peer group having a representative
65 * under the given root.
66 *
67 * Caller must hold namespace_sem
68 */
69int get_dominating_id(struct vfsmount *mnt, const struct path *root)
70{
71 struct vfsmount *m;
72
73 for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
74 struct vfsmount *d = get_peer_under_root(m, mnt->mnt_ns, root);
75 if (d)
76 return d->mnt_group_id;
77 }
78
79 return 0;
80}
81
82static int do_make_slave(struct vfsmount *mnt)
83{
84 struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
85 struct vfsmount *slave_mnt;
86
87 /*
88 * slave 'mnt' to a peer mount that has the
89 * same root dentry. If none is available then
90 * slave it to anything that is available.
91 */
92 while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
93 peer_mnt->mnt_root != mnt->mnt_root) ;
94
95 if (peer_mnt == mnt) {
96 peer_mnt = next_peer(mnt);
97 if (peer_mnt == mnt)
98 peer_mnt = NULL;
99 }
100 if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share))
101 mnt_release_group_id(mnt);
102
103 list_del_init(&mnt->mnt_share);
104 mnt->mnt_group_id = 0;
105
106 if (peer_mnt)
107 master = peer_mnt;
108
109 if (master) {
110 list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
111 slave_mnt->mnt_master = master;
112 list_move(&mnt->mnt_slave, &master->mnt_slave_list);
113 list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
114 INIT_LIST_HEAD(&mnt->mnt_slave_list);
115 } else {
116 struct list_head *p = &mnt->mnt_slave_list;
117 while (!list_empty(p)) {
118 slave_mnt = list_first_entry(p,
119 struct vfsmount, mnt_slave);
120 list_del_init(&slave_mnt->mnt_slave);
121 slave_mnt->mnt_master = NULL;
122 }
123 }
124 mnt->mnt_master = master;
125 CLEAR_MNT_SHARED(mnt);
126 return 0;
127}
128
129/*
130 * vfsmount lock must be held for write
131 */
132void change_mnt_propagation(struct vfsmount *mnt, int type)
133{
134 if (type == MS_SHARED) {
135 set_mnt_shared(mnt);
136 return;
137 }
138 do_make_slave(mnt);
139 if (type != MS_SLAVE) {
140 list_del_init(&mnt->mnt_slave);
141 mnt->mnt_master = NULL;
142 if (type == MS_UNBINDABLE)
143 mnt->mnt_flags |= MNT_UNBINDABLE;
144 else
145 mnt->mnt_flags &= ~MNT_UNBINDABLE;
146 }
147}
148
149/*
150 * get the next mount in the propagation tree.
151 * @m: the mount seen last
152 * @origin: the original mount from where the tree walk initiated
153 *
154 * Note that peer groups form contiguous segments of slave lists.
155 * We rely on that in get_source() to be able to find out if
156 * vfsmount found while iterating with propagation_next() is
157 * a peer of one we'd found earlier.
158 */
159static struct vfsmount *propagation_next(struct vfsmount *m,
160 struct vfsmount *origin)
161{
162 /* are there any slaves of this mount? */
163 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
164 return first_slave(m);
165
166 while (1) {
167 struct vfsmount *next;
168 struct vfsmount *master = m->mnt_master;
169
170 if (master == origin->mnt_master) {
171 next = next_peer(m);
172 return ((next == origin) ? NULL : next);
173 } else if (m->mnt_slave.next != &master->mnt_slave_list)
174 return next_slave(m);
175
176 /* back at master */
177 m = master;
178 }
179}
180
181/*
182 * return the source mount to be used for cloning
183 *
184 * @dest the current destination mount
185 * @last_dest the last seen destination mount
186 * @last_src the last seen source mount
187 * @type return CL_SLAVE if the new mount has to be
188 * cloned as a slave.
189 */
190static struct vfsmount *get_source(struct vfsmount *dest,
191 struct vfsmount *last_dest,
192 struct vfsmount *last_src,
193 int *type)
194{
195 struct vfsmount *p_last_src = NULL;
196 struct vfsmount *p_last_dest = NULL;
197
198 while (last_dest != dest->mnt_master) {
199 p_last_dest = last_dest;
200 p_last_src = last_src;
201 last_dest = last_dest->mnt_master;
202 last_src = last_src->mnt_master;
203 }
204
205 if (p_last_dest) {
206 do {
207 p_last_dest = next_peer(p_last_dest);
208 } while (IS_MNT_NEW(p_last_dest));
209 /* is that a peer of the earlier? */
210 if (dest == p_last_dest) {
211 *type = CL_MAKE_SHARED;
212 return p_last_src;
213 }
214 }
215 /* slave of the earlier, then */
216 *type = CL_SLAVE;
217 /* beginning of peer group among the slaves? */
218 if (IS_MNT_SHARED(dest))
219 *type |= CL_MAKE_SHARED;
220 return last_src;
221}
222
223/*
224 * mount 'source_mnt' under the destination 'dest_mnt' at
225 * dentry 'dest_dentry'. And propagate that mount to
226 * all the peer and slave mounts of 'dest_mnt'.
227 * Link all the new mounts into a propagation tree headed at
228 * source_mnt. Also link all the new mounts using ->mnt_list
229 * headed at source_mnt's ->mnt_list
230 *
231 * @dest_mnt: destination mount.
232 * @dest_dentry: destination dentry.
233 * @source_mnt: source mount.
234 * @tree_list : list of heads of trees to be attached.
235 */
236int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry,
237 struct vfsmount *source_mnt, struct list_head *tree_list)
238{
239 struct vfsmount *m, *child;
240 int ret = 0;
241 struct vfsmount *prev_dest_mnt = dest_mnt;
242 struct vfsmount *prev_src_mnt = source_mnt;
243 LIST_HEAD(tmp_list);
244 LIST_HEAD(umount_list);
245
246 for (m = propagation_next(dest_mnt, dest_mnt); m;
247 m = propagation_next(m, dest_mnt)) {
248 int type;
249 struct vfsmount *source;
250
251 if (IS_MNT_NEW(m))
252 continue;
253
254 source = get_source(m, prev_dest_mnt, prev_src_mnt, &type);
255
256 if (!(child = copy_tree(source, source->mnt_root, type))) {
257 ret = -ENOMEM;
258 list_splice(tree_list, tmp_list.prev);
259 goto out;
260 }
261
262 if (is_subdir(dest_dentry, m->mnt_root)) {
263 mnt_set_mountpoint(m, dest_dentry, child);
264 list_add_tail(&child->mnt_hash, tree_list);
265 } else {
266 /*
267 * This can happen if the parent mount was bind mounted
268 * on some subdirectory of a shared/slave mount.
269 */
270 list_add_tail(&child->mnt_hash, &tmp_list);
271 }
272 prev_dest_mnt = m;
273 prev_src_mnt = child;
274 }
275out:
276 br_write_lock(vfsmount_lock);
277 while (!list_empty(&tmp_list)) {
278 child = list_first_entry(&tmp_list, struct vfsmount, mnt_hash);
279 umount_tree(child, 0, &umount_list);
280 }
281 br_write_unlock(vfsmount_lock);
282 release_mounts(&umount_list);
283 return ret;
284}
285
286/*
287 * return true if the refcount is greater than count
288 */
289static inline int do_refcount_check(struct vfsmount *mnt, int count)
290{
291 int mycount = mnt_get_count(mnt) - mnt->mnt_ghosts;
292 return (mycount > count);
293}
294
295/*
296 * check if the mount 'mnt' can be unmounted successfully.
297 * @mnt: the mount to be checked for unmount
298 * NOTE: unmounting 'mnt' would naturally propagate to all
299 * other mounts its parent propagates to.
300 * Check if any of these mounts that **do not have submounts**
301 * have more references than 'refcnt'. If so return busy.
302 *
303 * vfsmount lock must be held for write
304 */
305int propagate_mount_busy(struct vfsmount *mnt, int refcnt)
306{
307 struct vfsmount *m, *child;
308 struct vfsmount *parent = mnt->mnt_parent;
309 int ret = 0;
310
311 if (mnt == parent)
312 return do_refcount_check(mnt, refcnt);
313
314 /*
315 * quickly check if the current mount can be unmounted.
316 * If not, we don't have to go checking for all other
317 * mounts
318 */
319 if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
320 return 1;
321
322 for (m = propagation_next(parent, parent); m;
323 m = propagation_next(m, parent)) {
324 child = __lookup_mnt(m, mnt->mnt_mountpoint, 0);
325 if (child && list_empty(&child->mnt_mounts) &&
326 (ret = do_refcount_check(child, 1)))
327 break;
328 }
329 return ret;
330}
331
332/*
333 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
334 * parent propagates to.
335 */
336static void __propagate_umount(struct vfsmount *mnt)
337{
338 struct vfsmount *parent = mnt->mnt_parent;
339 struct vfsmount *m;
340
341 BUG_ON(parent == mnt);
342
343 for (m = propagation_next(parent, parent); m;
344 m = propagation_next(m, parent)) {
345
346 struct vfsmount *child = __lookup_mnt(m,
347 mnt->mnt_mountpoint, 0);
348 /*
349 * umount the child only if the child has no
350 * other children
351 */
352 if (child && list_empty(&child->mnt_mounts))
353 list_move_tail(&child->mnt_hash, &mnt->mnt_hash);
354 }
355}
356
357/*
358 * collect all mounts that receive propagation from the mount in @list,
359 * and return these additional mounts in the same list.
360 * @list: the list of mounts to be unmounted.
361 *
362 * vfsmount lock must be held for write
363 */
364int propagate_umount(struct list_head *list)
365{
366 struct vfsmount *mnt;
367
368 list_for_each_entry(mnt, list, mnt_hash)
369 __propagate_umount(mnt);
370 return 0;
371}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/fs/pnode.c
4 *
5 * (C) Copyright IBM Corporation 2005.
6 * Author : Ram Pai (linuxram@us.ibm.com)
7 */
8#include <linux/mnt_namespace.h>
9#include <linux/mount.h>
10#include <linux/fs.h>
11#include <linux/nsproxy.h>
12#include <uapi/linux/mount.h>
13#include "internal.h"
14#include "pnode.h"
15
16/* return the next shared peer mount of @p */
17static inline struct mount *next_peer(struct mount *p)
18{
19 return list_entry(p->mnt_share.next, struct mount, mnt_share);
20}
21
22static inline struct mount *first_slave(struct mount *p)
23{
24 return list_entry(p->mnt_slave_list.next, struct mount, mnt_slave);
25}
26
27static inline struct mount *last_slave(struct mount *p)
28{
29 return list_entry(p->mnt_slave_list.prev, struct mount, mnt_slave);
30}
31
32static inline struct mount *next_slave(struct mount *p)
33{
34 return list_entry(p->mnt_slave.next, struct mount, mnt_slave);
35}
36
37static struct mount *get_peer_under_root(struct mount *mnt,
38 struct mnt_namespace *ns,
39 const struct path *root)
40{
41 struct mount *m = mnt;
42
43 do {
44 /* Check the namespace first for optimization */
45 if (m->mnt_ns == ns && is_path_reachable(m, m->mnt.mnt_root, root))
46 return m;
47
48 m = next_peer(m);
49 } while (m != mnt);
50
51 return NULL;
52}
53
54/*
55 * Get ID of closest dominating peer group having a representative
56 * under the given root.
57 *
58 * Caller must hold namespace_sem
59 */
60int get_dominating_id(struct mount *mnt, const struct path *root)
61{
62 struct mount *m;
63
64 for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
65 struct mount *d = get_peer_under_root(m, mnt->mnt_ns, root);
66 if (d)
67 return d->mnt_group_id;
68 }
69
70 return 0;
71}
72
73static int do_make_slave(struct mount *mnt)
74{
75 struct mount *master, *slave_mnt;
76
77 if (list_empty(&mnt->mnt_share)) {
78 if (IS_MNT_SHARED(mnt)) {
79 mnt_release_group_id(mnt);
80 CLEAR_MNT_SHARED(mnt);
81 }
82 master = mnt->mnt_master;
83 if (!master) {
84 struct list_head *p = &mnt->mnt_slave_list;
85 while (!list_empty(p)) {
86 slave_mnt = list_first_entry(p,
87 struct mount, mnt_slave);
88 list_del_init(&slave_mnt->mnt_slave);
89 slave_mnt->mnt_master = NULL;
90 }
91 return 0;
92 }
93 } else {
94 struct mount *m;
95 /*
96 * slave 'mnt' to a peer mount that has the
97 * same root dentry. If none is available then
98 * slave it to anything that is available.
99 */
100 for (m = master = next_peer(mnt); m != mnt; m = next_peer(m)) {
101 if (m->mnt.mnt_root == mnt->mnt.mnt_root) {
102 master = m;
103 break;
104 }
105 }
106 list_del_init(&mnt->mnt_share);
107 mnt->mnt_group_id = 0;
108 CLEAR_MNT_SHARED(mnt);
109 }
110 list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
111 slave_mnt->mnt_master = master;
112 list_move(&mnt->mnt_slave, &master->mnt_slave_list);
113 list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
114 INIT_LIST_HEAD(&mnt->mnt_slave_list);
115 mnt->mnt_master = master;
116 return 0;
117}
118
119/*
120 * vfsmount lock must be held for write
121 */
122void change_mnt_propagation(struct mount *mnt, int type)
123{
124 if (type == MS_SHARED) {
125 set_mnt_shared(mnt);
126 return;
127 }
128 do_make_slave(mnt);
129 if (type != MS_SLAVE) {
130 list_del_init(&mnt->mnt_slave);
131 mnt->mnt_master = NULL;
132 if (type == MS_UNBINDABLE)
133 mnt->mnt.mnt_flags |= MNT_UNBINDABLE;
134 else
135 mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;
136 }
137}
138
139/*
140 * get the next mount in the propagation tree.
141 * @m: the mount seen last
142 * @origin: the original mount from where the tree walk initiated
143 *
144 * Note that peer groups form contiguous segments of slave lists.
145 * We rely on that in get_source() to be able to find out if
146 * vfsmount found while iterating with propagation_next() is
147 * a peer of one we'd found earlier.
148 */
149static struct mount *propagation_next(struct mount *m,
150 struct mount *origin)
151{
152 /* are there any slaves of this mount? */
153 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
154 return first_slave(m);
155
156 while (1) {
157 struct mount *master = m->mnt_master;
158
159 if (master == origin->mnt_master) {
160 struct mount *next = next_peer(m);
161 return (next == origin) ? NULL : next;
162 } else if (m->mnt_slave.next != &master->mnt_slave_list)
163 return next_slave(m);
164
165 /* back at master */
166 m = master;
167 }
168}
169
170static struct mount *skip_propagation_subtree(struct mount *m,
171 struct mount *origin)
172{
173 /*
174 * Advance m such that propagation_next will not return
175 * the slaves of m.
176 */
177 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
178 m = last_slave(m);
179
180 return m;
181}
182
183static struct mount *next_group(struct mount *m, struct mount *origin)
184{
185 while (1) {
186 while (1) {
187 struct mount *next;
188 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
189 return first_slave(m);
190 next = next_peer(m);
191 if (m->mnt_group_id == origin->mnt_group_id) {
192 if (next == origin)
193 return NULL;
194 } else if (m->mnt_slave.next != &next->mnt_slave)
195 break;
196 m = next;
197 }
198 /* m is the last peer */
199 while (1) {
200 struct mount *master = m->mnt_master;
201 if (m->mnt_slave.next != &master->mnt_slave_list)
202 return next_slave(m);
203 m = next_peer(master);
204 if (master->mnt_group_id == origin->mnt_group_id)
205 break;
206 if (master->mnt_slave.next == &m->mnt_slave)
207 break;
208 m = master;
209 }
210 if (m == origin)
211 return NULL;
212 }
213}
214
215/* all accesses are serialized by namespace_sem */
216static struct mount *last_dest, *first_source, *last_source, *dest_master;
217static struct mountpoint *mp;
218static struct hlist_head *list;
219
220static inline bool peers(struct mount *m1, struct mount *m2)
221{
222 return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id;
223}
224
225static int propagate_one(struct mount *m)
226{
227 struct mount *child;
228 int type;
229 /* skip ones added by this propagate_mnt() */
230 if (IS_MNT_NEW(m))
231 return 0;
232 /* skip if mountpoint isn't covered by it */
233 if (!is_subdir(mp->m_dentry, m->mnt.mnt_root))
234 return 0;
235 if (peers(m, last_dest)) {
236 type = CL_MAKE_SHARED;
237 } else {
238 struct mount *n, *p;
239 bool done;
240 for (n = m; ; n = p) {
241 p = n->mnt_master;
242 if (p == dest_master || IS_MNT_MARKED(p))
243 break;
244 }
245 do {
246 struct mount *parent = last_source->mnt_parent;
247 if (last_source == first_source)
248 break;
249 done = parent->mnt_master == p;
250 if (done && peers(n, parent))
251 break;
252 last_source = last_source->mnt_master;
253 } while (!done);
254
255 type = CL_SLAVE;
256 /* beginning of peer group among the slaves? */
257 if (IS_MNT_SHARED(m))
258 type |= CL_MAKE_SHARED;
259 }
260
261 child = copy_tree(last_source, last_source->mnt.mnt_root, type);
262 if (IS_ERR(child))
263 return PTR_ERR(child);
264 mnt_set_mountpoint(m, mp, child);
265 last_dest = m;
266 last_source = child;
267 if (m->mnt_master != dest_master) {
268 read_seqlock_excl(&mount_lock);
269 SET_MNT_MARK(m->mnt_master);
270 read_sequnlock_excl(&mount_lock);
271 }
272 hlist_add_head(&child->mnt_hash, list);
273 return count_mounts(m->mnt_ns, child);
274}
275
276/*
277 * mount 'source_mnt' under the destination 'dest_mnt' at
278 * dentry 'dest_dentry'. And propagate that mount to
279 * all the peer and slave mounts of 'dest_mnt'.
280 * Link all the new mounts into a propagation tree headed at
281 * source_mnt. Also link all the new mounts using ->mnt_list
282 * headed at source_mnt's ->mnt_list
283 *
284 * @dest_mnt: destination mount.
285 * @dest_dentry: destination dentry.
286 * @source_mnt: source mount.
287 * @tree_list : list of heads of trees to be attached.
288 */
289int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
290 struct mount *source_mnt, struct hlist_head *tree_list)
291{
292 struct mount *m, *n;
293 int ret = 0;
294
295 /*
296 * we don't want to bother passing tons of arguments to
297 * propagate_one(); everything is serialized by namespace_sem,
298 * so globals will do just fine.
299 */
300 last_dest = dest_mnt;
301 first_source = source_mnt;
302 last_source = source_mnt;
303 mp = dest_mp;
304 list = tree_list;
305 dest_master = dest_mnt->mnt_master;
306
307 /* all peers of dest_mnt, except dest_mnt itself */
308 for (n = next_peer(dest_mnt); n != dest_mnt; n = next_peer(n)) {
309 ret = propagate_one(n);
310 if (ret)
311 goto out;
312 }
313
314 /* all slave groups */
315 for (m = next_group(dest_mnt, dest_mnt); m;
316 m = next_group(m, dest_mnt)) {
317 /* everything in that slave group */
318 n = m;
319 do {
320 ret = propagate_one(n);
321 if (ret)
322 goto out;
323 n = next_peer(n);
324 } while (n != m);
325 }
326out:
327 read_seqlock_excl(&mount_lock);
328 hlist_for_each_entry(n, tree_list, mnt_hash) {
329 m = n->mnt_parent;
330 if (m->mnt_master != dest_mnt->mnt_master)
331 CLEAR_MNT_MARK(m->mnt_master);
332 }
333 read_sequnlock_excl(&mount_lock);
334 return ret;
335}
336
337static struct mount *find_topper(struct mount *mnt)
338{
339 /* If there is exactly one mount covering mnt completely return it. */
340 struct mount *child;
341
342 if (!list_is_singular(&mnt->mnt_mounts))
343 return NULL;
344
345 child = list_first_entry(&mnt->mnt_mounts, struct mount, mnt_child);
346 if (child->mnt_mountpoint != mnt->mnt.mnt_root)
347 return NULL;
348
349 return child;
350}
351
352/*
353 * return true if the refcount is greater than count
354 */
355static inline int do_refcount_check(struct mount *mnt, int count)
356{
357 return mnt_get_count(mnt) > count;
358}
359
360/*
361 * check if the mount 'mnt' can be unmounted successfully.
362 * @mnt: the mount to be checked for unmount
363 * NOTE: unmounting 'mnt' would naturally propagate to all
364 * other mounts its parent propagates to.
365 * Check if any of these mounts that **do not have submounts**
366 * have more references than 'refcnt'. If so return busy.
367 *
368 * vfsmount lock must be held for write
369 */
370int propagate_mount_busy(struct mount *mnt, int refcnt)
371{
372 struct mount *m, *child, *topper;
373 struct mount *parent = mnt->mnt_parent;
374
375 if (mnt == parent)
376 return do_refcount_check(mnt, refcnt);
377
378 /*
379 * quickly check if the current mount can be unmounted.
380 * If not, we don't have to go checking for all other
381 * mounts
382 */
383 if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
384 return 1;
385
386 for (m = propagation_next(parent, parent); m;
387 m = propagation_next(m, parent)) {
388 int count = 1;
389 child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint);
390 if (!child)
391 continue;
392
393 /* Is there exactly one mount on the child that covers
394 * it completely whose reference should be ignored?
395 */
396 topper = find_topper(child);
397 if (topper)
398 count += 1;
399 else if (!list_empty(&child->mnt_mounts))
400 continue;
401
402 if (do_refcount_check(child, count))
403 return 1;
404 }
405 return 0;
406}
407
408/*
409 * Clear MNT_LOCKED when it can be shown to be safe.
410 *
411 * mount_lock lock must be held for write
412 */
413void propagate_mount_unlock(struct mount *mnt)
414{
415 struct mount *parent = mnt->mnt_parent;
416 struct mount *m, *child;
417
418 BUG_ON(parent == mnt);
419
420 for (m = propagation_next(parent, parent); m;
421 m = propagation_next(m, parent)) {
422 child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint);
423 if (child)
424 child->mnt.mnt_flags &= ~MNT_LOCKED;
425 }
426}
427
428static void umount_one(struct mount *mnt, struct list_head *to_umount)
429{
430 CLEAR_MNT_MARK(mnt);
431 mnt->mnt.mnt_flags |= MNT_UMOUNT;
432 list_del_init(&mnt->mnt_child);
433 list_del_init(&mnt->mnt_umounting);
434 list_move_tail(&mnt->mnt_list, to_umount);
435}
436
437/*
438 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
439 * parent propagates to.
440 */
441static bool __propagate_umount(struct mount *mnt,
442 struct list_head *to_umount,
443 struct list_head *to_restore)
444{
445 bool progress = false;
446 struct mount *child;
447
448 /*
449 * The state of the parent won't change if this mount is
450 * already unmounted or marked as without children.
451 */
452 if (mnt->mnt.mnt_flags & (MNT_UMOUNT | MNT_MARKED))
453 goto out;
454
455 /* Verify topper is the only grandchild that has not been
456 * speculatively unmounted.
457 */
458 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
459 if (child->mnt_mountpoint == mnt->mnt.mnt_root)
460 continue;
461 if (!list_empty(&child->mnt_umounting) && IS_MNT_MARKED(child))
462 continue;
463 /* Found a mounted child */
464 goto children;
465 }
466
467 /* Mark mounts that can be unmounted if not locked */
468 SET_MNT_MARK(mnt);
469 progress = true;
470
471 /* If a mount is without children and not locked umount it. */
472 if (!IS_MNT_LOCKED(mnt)) {
473 umount_one(mnt, to_umount);
474 } else {
475children:
476 list_move_tail(&mnt->mnt_umounting, to_restore);
477 }
478out:
479 return progress;
480}
481
482static void umount_list(struct list_head *to_umount,
483 struct list_head *to_restore)
484{
485 struct mount *mnt, *child, *tmp;
486 list_for_each_entry(mnt, to_umount, mnt_list) {
487 list_for_each_entry_safe(child, tmp, &mnt->mnt_mounts, mnt_child) {
488 /* topper? */
489 if (child->mnt_mountpoint == mnt->mnt.mnt_root)
490 list_move_tail(&child->mnt_umounting, to_restore);
491 else
492 umount_one(child, to_umount);
493 }
494 }
495}
496
497static void restore_mounts(struct list_head *to_restore)
498{
499 /* Restore mounts to a clean working state */
500 while (!list_empty(to_restore)) {
501 struct mount *mnt, *parent;
502 struct mountpoint *mp;
503
504 mnt = list_first_entry(to_restore, struct mount, mnt_umounting);
505 CLEAR_MNT_MARK(mnt);
506 list_del_init(&mnt->mnt_umounting);
507
508 /* Should this mount be reparented? */
509 mp = mnt->mnt_mp;
510 parent = mnt->mnt_parent;
511 while (parent->mnt.mnt_flags & MNT_UMOUNT) {
512 mp = parent->mnt_mp;
513 parent = parent->mnt_parent;
514 }
515 if (parent != mnt->mnt_parent)
516 mnt_change_mountpoint(parent, mp, mnt);
517 }
518}
519
520static void cleanup_umount_visitations(struct list_head *visited)
521{
522 while (!list_empty(visited)) {
523 struct mount *mnt =
524 list_first_entry(visited, struct mount, mnt_umounting);
525 list_del_init(&mnt->mnt_umounting);
526 }
527}
528
529/*
530 * collect all mounts that receive propagation from the mount in @list,
531 * and return these additional mounts in the same list.
532 * @list: the list of mounts to be unmounted.
533 *
534 * vfsmount lock must be held for write
535 */
536int propagate_umount(struct list_head *list)
537{
538 struct mount *mnt;
539 LIST_HEAD(to_restore);
540 LIST_HEAD(to_umount);
541 LIST_HEAD(visited);
542
543 /* Find candidates for unmounting */
544 list_for_each_entry_reverse(mnt, list, mnt_list) {
545 struct mount *parent = mnt->mnt_parent;
546 struct mount *m;
547
548 /*
549 * If this mount has already been visited it is known that it's
550 * entire peer group and all of their slaves in the propagation
551 * tree for the mountpoint has already been visited and there is
552 * no need to visit them again.
553 */
554 if (!list_empty(&mnt->mnt_umounting))
555 continue;
556
557 list_add_tail(&mnt->mnt_umounting, &visited);
558 for (m = propagation_next(parent, parent); m;
559 m = propagation_next(m, parent)) {
560 struct mount *child = __lookup_mnt(&m->mnt,
561 mnt->mnt_mountpoint);
562 if (!child)
563 continue;
564
565 if (!list_empty(&child->mnt_umounting)) {
566 /*
567 * If the child has already been visited it is
568 * know that it's entire peer group and all of
569 * their slaves in the propgation tree for the
570 * mountpoint has already been visited and there
571 * is no need to visit this subtree again.
572 */
573 m = skip_propagation_subtree(m, parent);
574 continue;
575 } else if (child->mnt.mnt_flags & MNT_UMOUNT) {
576 /*
577 * We have come accross an partially unmounted
578 * mount in list that has not been visited yet.
579 * Remember it has been visited and continue
580 * about our merry way.
581 */
582 list_add_tail(&child->mnt_umounting, &visited);
583 continue;
584 }
585
586 /* Check the child and parents while progress is made */
587 while (__propagate_umount(child,
588 &to_umount, &to_restore)) {
589 /* Is the parent a umount candidate? */
590 child = child->mnt_parent;
591 if (list_empty(&child->mnt_umounting))
592 break;
593 }
594 }
595 }
596
597 umount_list(&to_umount, &to_restore);
598 restore_mounts(&to_restore);
599 cleanup_umount_visitations(&visited);
600 list_splice_tail(&to_umount, list);
601
602 return 0;
603}