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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>
Eric W. Biederman132c94e2013-03-22 04:08:05 -070012#include <linux/nsproxy.h>
Al Viro6d59e7f2008-03-22 15:48:17 -040013#include "internal.h"
Ram Pai07b20882005-11-07 17:19:07 -050014#include "pnode.h"
15
Ram Pai03e06e62005-11-07 17:19:33 -050016/* return the next shared peer mount of @p */
Al Viroc9371352011-11-24 23:56:26 -050017static inline struct mount *next_peer(struct mount *p)
Ram Pai03e06e62005-11-07 17:19:33 -050018{
Al Viro6776db3d2011-11-25 00:22:05 -050019 return list_entry(p->mnt_share.next, struct mount, mnt_share);
Ram Pai03e06e62005-11-07 17:19:33 -050020}
21
Al Viroc9371352011-11-24 23:56:26 -050022static inline struct mount *first_slave(struct mount *p)
Ram Pai5afe0022005-11-07 17:21:01 -050023{
Al Viro6776db3d2011-11-25 00:22:05 -050024 return list_entry(p->mnt_slave_list.next, struct mount, mnt_slave);
Ram Pai5afe0022005-11-07 17:21:01 -050025}
26
Eric W. Biederman54fcb232016-10-24 17:25:19 -050027static inline struct mount *last_slave(struct mount *p)
28{
29 return list_entry(p->mnt_slave_list.prev, struct mount, mnt_slave);
30}
31
Al Viroc9371352011-11-24 23:56:26 -050032static inline struct mount *next_slave(struct mount *p)
Ram Pai5afe0022005-11-07 17:21:01 -050033{
Al Viro6776db3d2011-11-25 00:22:05 -050034 return list_entry(p->mnt_slave.next, struct mount, mnt_slave);
Ram Pai5afe0022005-11-07 17:21:01 -050035}
36
Al Viro6fc78712011-11-24 23:35:54 -050037static struct mount *get_peer_under_root(struct mount *mnt,
38 struct mnt_namespace *ns,
39 const struct path *root)
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010040{
Al Viro6fc78712011-11-24 23:35:54 -050041 struct mount *m = mnt;
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010042
43 do {
44 /* Check the namespace first for optimization */
Al Viro143c8c92011-11-25 00:46:35 -050045 if (m->mnt_ns == ns && is_path_reachable(m, m->mnt.mnt_root, root))
Al Viro6fc78712011-11-24 23:35:54 -050046 return m;
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010047
Al Viroc9371352011-11-24 23:56:26 -050048 m = next_peer(m);
Al Viro6fc78712011-11-24 23:35:54 -050049 } while (m != mnt);
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010050
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 */
Al Viro6fc78712011-11-24 23:35:54 -050060int get_dominating_id(struct mount *mnt, const struct path *root)
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010061{
Al Viro6fc78712011-11-24 23:35:54 -050062 struct mount *m;
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010063
Al Viro32301922011-11-25 00:10:28 -050064 for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
Al Viro143c8c92011-11-25 00:46:35 -050065 struct mount *d = get_peer_under_root(m, mnt->mnt_ns, root);
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010066 if (d)
Al Viro15169fe2011-11-25 00:50:41 -050067 return d->mnt_group_id;
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010068 }
69
70 return 0;
71}
72
Al Viro6fc78712011-11-24 23:35:54 -050073static int do_make_slave(struct mount *mnt)
Ram Paia58b0eb2005-11-07 17:20:48 -050074{
Al Viro32301922011-11-25 00:10:28 -050075 struct mount *peer_mnt = mnt, *master = mnt->mnt_master;
Al Virod10e8de2011-11-25 00:07:16 -050076 struct mount *slave_mnt;
Ram Paia58b0eb2005-11-07 17:20:48 -050077
78 /*
79 * slave 'mnt' to a peer mount that has the
Al Viro796a6b52010-01-16 13:28:47 -050080 * same root dentry. If none is available then
Ram Paia58b0eb2005-11-07 17:20:48 -050081 * slave it to anything that is available.
82 */
Al Viroc9371352011-11-24 23:56:26 -050083 while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
Al Viro6fc78712011-11-24 23:35:54 -050084 peer_mnt->mnt.mnt_root != mnt->mnt.mnt_root) ;
Ram Paia58b0eb2005-11-07 17:20:48 -050085
86 if (peer_mnt == mnt) {
Al Viroc9371352011-11-24 23:56:26 -050087 peer_mnt = next_peer(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -050088 if (peer_mnt == mnt)
89 peer_mnt = NULL;
90 }
Takashi Iwai5d477b62013-05-10 14:04:11 +020091 if (mnt->mnt_group_id && IS_MNT_SHARED(mnt) &&
92 list_empty(&mnt->mnt_share))
Al Viro6fc78712011-11-24 23:35:54 -050093 mnt_release_group_id(mnt);
Miklos Szeredi719f5d72008-03-27 13:06:23 +010094
Al Viro6776db3d2011-11-25 00:22:05 -050095 list_del_init(&mnt->mnt_share);
Al Viro15169fe2011-11-25 00:50:41 -050096 mnt->mnt_group_id = 0;
Ram Paia58b0eb2005-11-07 17:20:48 -050097
98 if (peer_mnt)
99 master = peer_mnt;
100
101 if (master) {
Al Viro6776db3d2011-11-25 00:22:05 -0500102 list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
Al Viro32301922011-11-25 00:10:28 -0500103 slave_mnt->mnt_master = master;
Al Viro6776db3d2011-11-25 00:22:05 -0500104 list_move(&mnt->mnt_slave, &master->mnt_slave_list);
105 list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
106 INIT_LIST_HEAD(&mnt->mnt_slave_list);
Ram Paia58b0eb2005-11-07 17:20:48 -0500107 } else {
Al Viro6776db3d2011-11-25 00:22:05 -0500108 struct list_head *p = &mnt->mnt_slave_list;
Ram Paia58b0eb2005-11-07 17:20:48 -0500109 while (!list_empty(p)) {
Pavel Emelianovb5e61812007-05-08 00:30:19 -0700110 slave_mnt = list_first_entry(p,
Al Viro6776db3d2011-11-25 00:22:05 -0500111 struct mount, mnt_slave);
112 list_del_init(&slave_mnt->mnt_slave);
Ram Paia58b0eb2005-11-07 17:20:48 -0500113 slave_mnt->mnt_master = NULL;
114 }
115 }
Al Viro32301922011-11-25 00:10:28 -0500116 mnt->mnt_master = master;
Al Virofc7be132011-11-25 01:05:37 -0500117 CLEAR_MNT_SHARED(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -0500118 return 0;
119}
120
Nick Piggin99b7db72010-08-18 04:37:39 +1000121/*
122 * vfsmount lock must be held for write
123 */
Al Viro0f0afb12011-11-24 20:43:10 -0500124void change_mnt_propagation(struct mount *mnt, int type)
Ram Pai07b20882005-11-07 17:19:07 -0500125{
Ram Pai03e06e62005-11-07 17:19:33 -0500126 if (type == MS_SHARED) {
Ram Paib90fa9a2005-11-07 17:19:50 -0500127 set_mnt_shared(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -0500128 return;
129 }
Al Viro6fc78712011-11-24 23:35:54 -0500130 do_make_slave(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -0500131 if (type != MS_SLAVE) {
Al Viro6776db3d2011-11-25 00:22:05 -0500132 list_del_init(&mnt->mnt_slave);
Al Virod10e8de2011-11-25 00:07:16 -0500133 mnt->mnt_master = NULL;
Ram Pai9676f0c2005-11-07 17:21:20 -0500134 if (type == MS_UNBINDABLE)
Al Viro0f0afb12011-11-24 20:43:10 -0500135 mnt->mnt.mnt_flags |= MNT_UNBINDABLE;
Andries E. Brouwer0b03cfb2008-02-06 01:36:32 -0800136 else
Al Viro0f0afb12011-11-24 20:43:10 -0500137 mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;
Ram Pai03e06e62005-11-07 17:19:33 -0500138 }
Ram Pai07b20882005-11-07 17:19:07 -0500139}
Ram Paib90fa9a2005-11-07 17:19:50 -0500140
141/*
142 * get the next mount in the propagation tree.
143 * @m: the mount seen last
144 * @origin: the original mount from where the tree walk initiated
Al Viro796a6b52010-01-16 13:28:47 -0500145 *
146 * Note that peer groups form contiguous segments of slave lists.
147 * We rely on that in get_source() to be able to find out if
148 * vfsmount found while iterating with propagation_next() is
149 * a peer of one we'd found earlier.
Ram Paib90fa9a2005-11-07 17:19:50 -0500150 */
Al Viroc9371352011-11-24 23:56:26 -0500151static struct mount *propagation_next(struct mount *m,
152 struct mount *origin)
Ram Paib90fa9a2005-11-07 17:19:50 -0500153{
Ram Pai5afe0022005-11-07 17:21:01 -0500154 /* are there any slaves of this mount? */
Al Viro143c8c92011-11-25 00:46:35 -0500155 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
Ram Pai5afe0022005-11-07 17:21:01 -0500156 return first_slave(m);
157
158 while (1) {
Al Viro32301922011-11-25 00:10:28 -0500159 struct mount *master = m->mnt_master;
Ram Pai5afe0022005-11-07 17:21:01 -0500160
Al Viro32301922011-11-25 00:10:28 -0500161 if (master == origin->mnt_master) {
Al Viroc9371352011-11-24 23:56:26 -0500162 struct mount *next = next_peer(m);
163 return (next == origin) ? NULL : next;
Al Viro6776db3d2011-11-25 00:22:05 -0500164 } else if (m->mnt_slave.next != &master->mnt_slave_list)
Ram Pai5afe0022005-11-07 17:21:01 -0500165 return next_slave(m);
166
167 /* back at master */
168 m = master;
169 }
170}
171
Eric W. Biederman54fcb232016-10-24 17:25:19 -0500172static struct mount *skip_propagation_subtree(struct mount *m,
173 struct mount *origin)
174{
175 /*
176 * Advance m such that propagation_next will not return
177 * the slaves of m.
178 */
179 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
180 m = last_slave(m);
181
182 return m;
183}
184
Al Virof2ebb3a2014-02-27 09:35:45 -0500185static struct mount *next_group(struct mount *m, struct mount *origin)
Ram Pai5afe0022005-11-07 17:21:01 -0500186{
Al Virof2ebb3a2014-02-27 09:35:45 -0500187 while (1) {
188 while (1) {
189 struct mount *next;
190 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
191 return first_slave(m);
192 next = next_peer(m);
193 if (m->mnt_group_id == origin->mnt_group_id) {
194 if (next == origin)
195 return NULL;
196 } else if (m->mnt_slave.next != &next->mnt_slave)
197 break;
198 m = next;
Al Viro796a6b52010-01-16 13:28:47 -0500199 }
Al Virof2ebb3a2014-02-27 09:35:45 -0500200 /* m is the last peer */
201 while (1) {
202 struct mount *master = m->mnt_master;
203 if (m->mnt_slave.next != &master->mnt_slave_list)
204 return next_slave(m);
205 m = next_peer(master);
206 if (master->mnt_group_id == origin->mnt_group_id)
207 break;
208 if (master->mnt_slave.next == &m->mnt_slave)
209 break;
210 m = master;
211 }
212 if (m == origin)
213 return NULL;
Ram Pai5afe0022005-11-07 17:21:01 -0500214 }
Al Virof2ebb3a2014-02-27 09:35:45 -0500215}
216
217/* all accesses are serialized by namespace_sem */
218static struct user_namespace *user_ns;
Eric W. Biederman5ec08112016-05-05 09:29:29 -0500219static struct mount *last_dest, *first_source, *last_source, *dest_master;
Al Virof2ebb3a2014-02-27 09:35:45 -0500220static struct mountpoint *mp;
221static struct hlist_head *list;
222
Maxim Patlasov7ae8fd02016-02-16 11:45:33 -0800223static inline bool peers(struct mount *m1, struct mount *m2)
224{
225 return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id;
226}
227
Al Virof2ebb3a2014-02-27 09:35:45 -0500228static int propagate_one(struct mount *m)
229{
230 struct mount *child;
231 int type;
232 /* skip ones added by this propagate_mnt() */
233 if (IS_MNT_NEW(m))
234 return 0;
235 /* skip if mountpoint isn't covered by it */
236 if (!is_subdir(mp->m_dentry, m->mnt.mnt_root))
237 return 0;
Maxim Patlasov7ae8fd02016-02-16 11:45:33 -0800238 if (peers(m, last_dest)) {
Al Virof2ebb3a2014-02-27 09:35:45 -0500239 type = CL_MAKE_SHARED;
240 } else {
241 struct mount *n, *p;
Eric W. Biederman5ec08112016-05-05 09:29:29 -0500242 bool done;
Al Virof2ebb3a2014-02-27 09:35:45 -0500243 for (n = m; ; n = p) {
244 p = n->mnt_master;
Eric W. Biederman5ec08112016-05-05 09:29:29 -0500245 if (p == dest_master || IS_MNT_MARKED(p))
Al Virof2ebb3a2014-02-27 09:35:45 -0500246 break;
Al Virof2ebb3a2014-02-27 09:35:45 -0500247 }
Eric W. Biederman5ec08112016-05-05 09:29:29 -0500248 do {
249 struct mount *parent = last_source->mnt_parent;
250 if (last_source == first_source)
251 break;
252 done = parent->mnt_master == p;
253 if (done && peers(n, parent))
254 break;
255 last_source = last_source->mnt_master;
256 } while (!done);
257
Al Virof2ebb3a2014-02-27 09:35:45 -0500258 type = CL_SLAVE;
259 /* beginning of peer group among the slaves? */
260 if (IS_MNT_SHARED(m))
261 type |= CL_MAKE_SHARED;
262 }
263
264 /* Notice when we are propagating across user namespaces */
265 if (m->mnt_ns->user_ns != user_ns)
266 type |= CL_UNPRIVILEGED;
267 child = copy_tree(last_source, last_source->mnt.mnt_root, type);
268 if (IS_ERR(child))
269 return PTR_ERR(child);
Eric W. Biederman8486a782014-10-07 16:22:52 -0700270 child->mnt.mnt_flags &= ~MNT_LOCKED;
Al Virofcd41812020-04-27 10:26:22 -0400271 read_seqlock_excl(&mount_lock);
Al Virof2ebb3a2014-02-27 09:35:45 -0500272 mnt_set_mountpoint(m, mp, child);
Al Virofcd41812020-04-27 10:26:22 -0400273 if (m->mnt_master != dest_master)
274 SET_MNT_MARK(m->mnt_master);
275 read_sequnlock_excl(&mount_lock);
Al Virof2ebb3a2014-02-27 09:35:45 -0500276 last_dest = m;
277 last_source = child;
Al Virof2ebb3a2014-02-27 09:35:45 -0500278 hlist_add_head(&child->mnt_hash, list);
Eric W. Biedermand2921682016-09-28 00:27:17 -0500279 return count_mounts(m->mnt_ns, child);
Ram Paib90fa9a2005-11-07 17:19:50 -0500280}
281
282/*
283 * mount 'source_mnt' under the destination 'dest_mnt' at
284 * dentry 'dest_dentry'. And propagate that mount to
285 * all the peer and slave mounts of 'dest_mnt'.
286 * Link all the new mounts into a propagation tree headed at
287 * source_mnt. Also link all the new mounts using ->mnt_list
288 * headed at source_mnt's ->mnt_list
289 *
290 * @dest_mnt: destination mount.
291 * @dest_dentry: destination dentry.
292 * @source_mnt: source mount.
293 * @tree_list : list of heads of trees to be attached.
294 */
Al Viro84d17192013-03-15 10:53:28 -0400295int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
Al Viro38129a12014-03-20 21:10:51 -0400296 struct mount *source_mnt, struct hlist_head *tree_list)
Ram Paib90fa9a2005-11-07 17:19:50 -0500297{
Al Virof2ebb3a2014-02-27 09:35:45 -0500298 struct mount *m, *n;
Ram Paib90fa9a2005-11-07 17:19:50 -0500299 int ret = 0;
Ram Paib90fa9a2005-11-07 17:19:50 -0500300
Al Virof2ebb3a2014-02-27 09:35:45 -0500301 /*
302 * we don't want to bother passing tons of arguments to
303 * propagate_one(); everything is serialized by namespace_sem,
304 * so globals will do just fine.
305 */
306 user_ns = current->nsproxy->mnt_ns->user_ns;
307 last_dest = dest_mnt;
Eric W. Biederman5ec08112016-05-05 09:29:29 -0500308 first_source = source_mnt;
Al Virof2ebb3a2014-02-27 09:35:45 -0500309 last_source = source_mnt;
310 mp = dest_mp;
311 list = tree_list;
312 dest_master = dest_mnt->mnt_master;
Ram Paib90fa9a2005-11-07 17:19:50 -0500313
Al Virof2ebb3a2014-02-27 09:35:45 -0500314 /* all peers of dest_mnt, except dest_mnt itself */
315 for (n = next_peer(dest_mnt); n != dest_mnt; n = next_peer(n)) {
316 ret = propagate_one(n);
317 if (ret)
Ram Paib90fa9a2005-11-07 17:19:50 -0500318 goto out;
Al Virof2ebb3a2014-02-27 09:35:45 -0500319 }
Ram Paib90fa9a2005-11-07 17:19:50 -0500320
Al Virof2ebb3a2014-02-27 09:35:45 -0500321 /* all slave groups */
322 for (m = next_group(dest_mnt, dest_mnt); m;
323 m = next_group(m, dest_mnt)) {
324 /* everything in that slave group */
325 n = m;
326 do {
327 ret = propagate_one(n);
328 if (ret)
329 goto out;
330 n = next_peer(n);
331 } while (n != m);
Ram Paib90fa9a2005-11-07 17:19:50 -0500332 }
333out:
Al Virof2ebb3a2014-02-27 09:35:45 -0500334 read_seqlock_excl(&mount_lock);
335 hlist_for_each_entry(n, tree_list, mnt_hash) {
336 m = n->mnt_parent;
337 if (m->mnt_master != dest_mnt->mnt_master)
338 CLEAR_MNT_MARK(m->mnt_master);
Ram Paib90fa9a2005-11-07 17:19:50 -0500339 }
Al Virof2ebb3a2014-02-27 09:35:45 -0500340 read_sequnlock_excl(&mount_lock);
Ram Paib90fa9a2005-11-07 17:19:50 -0500341 return ret;
342}
Ram Paia05964f2005-11-07 17:20:17 -0500343
Eric W. Biederman808e83e2017-01-20 18:28:35 +1300344static struct mount *find_topper(struct mount *mnt)
345{
346 /* If there is exactly one mount covering mnt completely return it. */
347 struct mount *child;
348
349 if (!list_is_singular(&mnt->mnt_mounts))
350 return NULL;
351
352 child = list_first_entry(&mnt->mnt_mounts, struct mount, mnt_child);
353 if (child->mnt_mountpoint != mnt->mnt.mnt_root)
354 return NULL;
355
356 return child;
357}
358
Ram Paia05964f2005-11-07 17:20:17 -0500359/*
360 * return true if the refcount is greater than count
361 */
Al Viro1ab59732011-11-24 21:35:16 -0500362static inline int do_refcount_check(struct mount *mnt, int count)
Ram Paia05964f2005-11-07 17:20:17 -0500363{
Al Viroaba809cf2013-09-28 23:10:55 -0400364 return mnt_get_count(mnt) > count;
Ram Paia05964f2005-11-07 17:20:17 -0500365}
366
367/*
368 * check if the mount 'mnt' can be unmounted successfully.
369 * @mnt: the mount to be checked for unmount
370 * NOTE: unmounting 'mnt' would naturally propagate to all
371 * other mounts its parent propagates to.
372 * Check if any of these mounts that **do not have submounts**
373 * have more references than 'refcnt'. If so return busy.
Nick Piggin99b7db72010-08-18 04:37:39 +1000374 *
Nick Pigginb3e19d92011-01-07 17:50:11 +1100375 * vfsmount lock must be held for write
Ram Paia05964f2005-11-07 17:20:17 -0500376 */
Al Viro1ab59732011-11-24 21:35:16 -0500377int propagate_mount_busy(struct mount *mnt, int refcnt)
Ram Paia05964f2005-11-07 17:20:17 -0500378{
Eric W. Biederman808e83e2017-01-20 18:28:35 +1300379 struct mount *m, *child, *topper;
Al Viro0714a532011-11-24 22:19:58 -0500380 struct mount *parent = mnt->mnt_parent;
Ram Paia05964f2005-11-07 17:20:17 -0500381
Al Viro0714a532011-11-24 22:19:58 -0500382 if (mnt == parent)
Ram Paia05964f2005-11-07 17:20:17 -0500383 return do_refcount_check(mnt, refcnt);
384
385 /*
386 * quickly check if the current mount can be unmounted.
387 * If not, we don't have to go checking for all other
388 * mounts
389 */
Al Viro6b41d532011-11-24 23:24:33 -0500390 if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
Ram Paia05964f2005-11-07 17:20:17 -0500391 return 1;
392
Al Viroc9371352011-11-24 23:56:26 -0500393 for (m = propagation_next(parent, parent); m;
394 m = propagation_next(m, parent)) {
Eric W. Biederman808e83e2017-01-20 18:28:35 +1300395 int count = 1;
396 child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint);
397 if (!child)
398 continue;
399
400 /* Is there exactly one mount on the child that covers
401 * it completely whose reference should be ignored?
402 */
403 topper = find_topper(child);
404 if (topper)
405 count += 1;
406 else if (!list_empty(&child->mnt_mounts))
407 continue;
408
409 if (do_refcount_check(child, count))
410 return 1;
Ram Paia05964f2005-11-07 17:20:17 -0500411 }
Eric W. Biederman808e83e2017-01-20 18:28:35 +1300412 return 0;
Ram Paia05964f2005-11-07 17:20:17 -0500413}
414
415/*
Eric W. Biederman5d884572015-01-03 05:39:35 -0600416 * Clear MNT_LOCKED when it can be shown to be safe.
417 *
418 * mount_lock lock must be held for write
419 */
420void propagate_mount_unlock(struct mount *mnt)
421{
422 struct mount *parent = mnt->mnt_parent;
423 struct mount *m, *child;
424
425 BUG_ON(parent == mnt);
426
427 for (m = propagation_next(parent, parent); m;
428 m = propagation_next(m, parent)) {
Eric W. Biederman808e83e2017-01-20 18:28:35 +1300429 child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint);
Eric W. Biederman5d884572015-01-03 05:39:35 -0600430 if (child)
431 child->mnt.mnt_flags &= ~MNT_LOCKED;
432 }
433}
434
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500435static void umount_one(struct mount *mnt, struct list_head *to_umount)
Eric W. Biederman0c56fe32015-01-05 13:38:04 -0600436{
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500437 CLEAR_MNT_MARK(mnt);
438 mnt->mnt.mnt_flags |= MNT_UMOUNT;
439 list_del_init(&mnt->mnt_child);
440 list_del_init(&mnt->mnt_umounting);
441 list_move_tail(&mnt->mnt_list, to_umount);
Eric W. Biederman0c56fe32015-01-05 13:38:04 -0600442}
443
444/*
Ram Paia05964f2005-11-07 17:20:17 -0500445 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
446 * parent propagates to.
447 */
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500448static bool __propagate_umount(struct mount *mnt,
449 struct list_head *to_umount,
450 struct list_head *to_restore)
Ram Paia05964f2005-11-07 17:20:17 -0500451{
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500452 bool progress = false;
453 struct mount *child;
Ram Paia05964f2005-11-07 17:20:17 -0500454
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500455 /*
456 * The state of the parent won't change if this mount is
457 * already unmounted or marked as without children.
458 */
459 if (mnt->mnt.mnt_flags & (MNT_UMOUNT | MNT_MARKED))
460 goto out;
Ram Paia05964f2005-11-07 17:20:17 -0500461
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500462 /* Verify topper is the only grandchild that has not been
463 * speculatively unmounted.
464 */
465 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
466 if (child->mnt_mountpoint == mnt->mnt.mnt_root)
Eric W. Biederman0c56fe32015-01-05 13:38:04 -0600467 continue;
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500468 if (!list_empty(&child->mnt_umounting) && IS_MNT_MARKED(child))
469 continue;
470 /* Found a mounted child */
471 goto children;
472 }
Eric W. Biederman808e83e2017-01-20 18:28:35 +1300473
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500474 /* Mark mounts that can be unmounted if not locked */
475 SET_MNT_MARK(mnt);
476 progress = true;
Eric W. Biederman808e83e2017-01-20 18:28:35 +1300477
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500478 /* If a mount is without children and not locked umount it. */
479 if (!IS_MNT_LOCKED(mnt)) {
480 umount_one(mnt, to_umount);
481 } else {
482children:
483 list_move_tail(&mnt->mnt_umounting, to_restore);
484 }
485out:
486 return progress;
487}
488
489static void umount_list(struct list_head *to_umount,
490 struct list_head *to_restore)
491{
492 struct mount *mnt, *child, *tmp;
493 list_for_each_entry(mnt, to_umount, mnt_list) {
494 list_for_each_entry_safe(child, tmp, &mnt->mnt_mounts, mnt_child) {
495 /* topper? */
496 if (child->mnt_mountpoint == mnt->mnt.mnt_root)
497 list_move_tail(&child->mnt_umounting, to_restore);
498 else
499 umount_one(child, to_umount);
Al Viro38129a12014-03-20 21:10:51 -0400500 }
Ram Paia05964f2005-11-07 17:20:17 -0500501 }
502}
503
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500504static void restore_mounts(struct list_head *to_restore)
Eric W. Biedermane260db72017-05-15 14:42:07 -0500505{
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500506 /* Restore mounts to a clean working state */
507 while (!list_empty(to_restore)) {
Eric W. Biedermane260db72017-05-15 14:42:07 -0500508 struct mount *mnt, *parent;
509 struct mountpoint *mp;
510
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500511 mnt = list_first_entry(to_restore, struct mount, mnt_umounting);
512 CLEAR_MNT_MARK(mnt);
513 list_del_init(&mnt->mnt_umounting);
Eric W. Biedermane260db72017-05-15 14:42:07 -0500514
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500515 /* Should this mount be reparented? */
Eric W. Biedermane260db72017-05-15 14:42:07 -0500516 mp = mnt->mnt_mp;
517 parent = mnt->mnt_parent;
518 while (parent->mnt.mnt_flags & MNT_UMOUNT) {
519 mp = parent->mnt_mp;
520 parent = parent->mnt_parent;
521 }
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500522 if (parent != mnt->mnt_parent)
523 mnt_change_mountpoint(parent, mp, mnt);
Eric W. Biedermane260db72017-05-15 14:42:07 -0500524 }
525}
526
Eric W. Biederman54fcb232016-10-24 17:25:19 -0500527static void cleanup_umount_visitations(struct list_head *visited)
528{
529 while (!list_empty(visited)) {
530 struct mount *mnt =
531 list_first_entry(visited, struct mount, mnt_umounting);
532 list_del_init(&mnt->mnt_umounting);
533 }
534}
535
Ram Paia05964f2005-11-07 17:20:17 -0500536/*
537 * collect all mounts that receive propagation from the mount in @list,
538 * and return these additional mounts in the same list.
539 * @list: the list of mounts to be unmounted.
Nick Piggin99b7db72010-08-18 04:37:39 +1000540 *
541 * vfsmount lock must be held for write
Ram Paia05964f2005-11-07 17:20:17 -0500542 */
Eric W. Biedermanc003b262014-12-18 13:10:48 -0600543int propagate_umount(struct list_head *list)
Ram Paia05964f2005-11-07 17:20:17 -0500544{
Al Viro61ef47b2011-11-24 18:25:28 -0500545 struct mount *mnt;
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500546 LIST_HEAD(to_restore);
547 LIST_HEAD(to_umount);
Eric W. Biederman54fcb232016-10-24 17:25:19 -0500548 LIST_HEAD(visited);
Ram Paia05964f2005-11-07 17:20:17 -0500549
Eric W. Biederman54fcb232016-10-24 17:25:19 -0500550 /* Find candidates for unmounting */
551 list_for_each_entry_reverse(mnt, list, mnt_list) {
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500552 struct mount *parent = mnt->mnt_parent;
553 struct mount *m;
Eric W. Biederman0c56fe32015-01-05 13:38:04 -0600554
Eric W. Biederman54fcb232016-10-24 17:25:19 -0500555 /*
556 * If this mount has already been visited it is known that it's
557 * entire peer group and all of their slaves in the propagation
558 * tree for the mountpoint has already been visited and there is
559 * no need to visit them again.
560 */
561 if (!list_empty(&mnt->mnt_umounting))
562 continue;
563
564 list_add_tail(&mnt->mnt_umounting, &visited);
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500565 for (m = propagation_next(parent, parent); m;
566 m = propagation_next(m, parent)) {
567 struct mount *child = __lookup_mnt(&m->mnt,
568 mnt->mnt_mountpoint);
569 if (!child)
570 continue;
Eric W. Biedermane260db72017-05-15 14:42:07 -0500571
Eric W. Biederman54fcb232016-10-24 17:25:19 -0500572 if (!list_empty(&child->mnt_umounting)) {
573 /*
574 * If the child has already been visited it is
575 * know that it's entire peer group and all of
576 * their slaves in the propgation tree for the
577 * mountpoint has already been visited and there
578 * is no need to visit this subtree again.
579 */
580 m = skip_propagation_subtree(m, parent);
581 continue;
582 } else if (child->mnt.mnt_flags & MNT_UMOUNT) {
583 /*
584 * We have come accross an partially unmounted
585 * mount in list that has not been visited yet.
586 * Remember it has been visited and continue
587 * about our merry way.
588 */
589 list_add_tail(&child->mnt_umounting, &visited);
590 continue;
591 }
592
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500593 /* Check the child and parents while progress is made */
594 while (__propagate_umount(child,
595 &to_umount, &to_restore)) {
596 /* Is the parent a umount candidate? */
597 child = child->mnt_parent;
598 if (list_empty(&child->mnt_umounting))
599 break;
600 }
601 }
602 }
603
604 umount_list(&to_umount, &to_restore);
605 restore_mounts(&to_restore);
Eric W. Biederman54fcb232016-10-24 17:25:19 -0500606 cleanup_umount_visitations(&visited);
Eric W. Biedermanbb4fbf02016-10-24 16:16:13 -0500607 list_splice_tail(&to_umount, list);
Eric W. Biedermane260db72017-05-15 14:42:07 -0500608
Ram Paia05964f2005-11-07 17:20:17 -0500609 return 0;
610}