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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
Al Viroc9371352011-11-24 23:56:26 -050027static inline struct mount *next_slave(struct mount *p)
Ram Pai5afe0022005-11-07 17:21:01 -050028{
Al Viro6776db3d2011-11-25 00:22:05 -050029 return list_entry(p->mnt_slave.next, struct mount, mnt_slave);
Ram Pai5afe0022005-11-07 17:21:01 -050030}
31
Al Viro6fc78712011-11-24 23:35:54 -050032static struct mount *get_peer_under_root(struct mount *mnt,
33 struct mnt_namespace *ns,
34 const struct path *root)
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010035{
Al Viro6fc78712011-11-24 23:35:54 -050036 struct mount *m = mnt;
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010037
38 do {
39 /* Check the namespace first for optimization */
Al Viro143c8c92011-11-25 00:46:35 -050040 if (m->mnt_ns == ns && is_path_reachable(m, m->mnt.mnt_root, root))
Al Viro6fc78712011-11-24 23:35:54 -050041 return m;
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010042
Al Viroc9371352011-11-24 23:56:26 -050043 m = next_peer(m);
Al Viro6fc78712011-11-24 23:35:54 -050044 } while (m != mnt);
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010045
46 return NULL;
47}
48
49/*
50 * Get ID of closest dominating peer group having a representative
51 * under the given root.
52 *
53 * Caller must hold namespace_sem
54 */
Al Viro6fc78712011-11-24 23:35:54 -050055int get_dominating_id(struct mount *mnt, const struct path *root)
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010056{
Al Viro6fc78712011-11-24 23:35:54 -050057 struct mount *m;
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010058
Al Viro32301922011-11-25 00:10:28 -050059 for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
Al Viro143c8c92011-11-25 00:46:35 -050060 struct mount *d = get_peer_under_root(m, mnt->mnt_ns, root);
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010061 if (d)
Al Viro15169fe2011-11-25 00:50:41 -050062 return d->mnt_group_id;
Miklos Szeredi97e7e0f2008-03-27 13:06:26 +010063 }
64
65 return 0;
66}
67
Al Viro6fc78712011-11-24 23:35:54 -050068static int do_make_slave(struct mount *mnt)
Ram Paia58b0eb2005-11-07 17:20:48 -050069{
Al Viro32301922011-11-25 00:10:28 -050070 struct mount *peer_mnt = mnt, *master = mnt->mnt_master;
Al Virod10e8de2011-11-25 00:07:16 -050071 struct mount *slave_mnt;
Ram Paia58b0eb2005-11-07 17:20:48 -050072
73 /*
74 * slave 'mnt' to a peer mount that has the
Al Viro796a6b52010-01-16 13:28:47 -050075 * same root dentry. If none is available then
Ram Paia58b0eb2005-11-07 17:20:48 -050076 * slave it to anything that is available.
77 */
Al Viroc9371352011-11-24 23:56:26 -050078 while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
Al Viro6fc78712011-11-24 23:35:54 -050079 peer_mnt->mnt.mnt_root != mnt->mnt.mnt_root) ;
Ram Paia58b0eb2005-11-07 17:20:48 -050080
81 if (peer_mnt == mnt) {
Al Viroc9371352011-11-24 23:56:26 -050082 peer_mnt = next_peer(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -050083 if (peer_mnt == mnt)
84 peer_mnt = NULL;
85 }
Takashi Iwai5d477b62013-05-10 14:04:11 +020086 if (mnt->mnt_group_id && IS_MNT_SHARED(mnt) &&
87 list_empty(&mnt->mnt_share))
Al Viro6fc78712011-11-24 23:35:54 -050088 mnt_release_group_id(mnt);
Miklos Szeredi719f5d72008-03-27 13:06:23 +010089
Al Viro6776db3d2011-11-25 00:22:05 -050090 list_del_init(&mnt->mnt_share);
Al Viro15169fe2011-11-25 00:50:41 -050091 mnt->mnt_group_id = 0;
Ram Paia58b0eb2005-11-07 17:20:48 -050092
93 if (peer_mnt)
94 master = peer_mnt;
95
96 if (master) {
Al Viro6776db3d2011-11-25 00:22:05 -050097 list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
Al Viro32301922011-11-25 00:10:28 -050098 slave_mnt->mnt_master = master;
Al Viro6776db3d2011-11-25 00:22:05 -050099 list_move(&mnt->mnt_slave, &master->mnt_slave_list);
100 list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
101 INIT_LIST_HEAD(&mnt->mnt_slave_list);
Ram Paia58b0eb2005-11-07 17:20:48 -0500102 } else {
Al Viro6776db3d2011-11-25 00:22:05 -0500103 struct list_head *p = &mnt->mnt_slave_list;
Ram Paia58b0eb2005-11-07 17:20:48 -0500104 while (!list_empty(p)) {
Pavel Emelianovb5e61812007-05-08 00:30:19 -0700105 slave_mnt = list_first_entry(p,
Al Viro6776db3d2011-11-25 00:22:05 -0500106 struct mount, mnt_slave);
107 list_del_init(&slave_mnt->mnt_slave);
Ram Paia58b0eb2005-11-07 17:20:48 -0500108 slave_mnt->mnt_master = NULL;
109 }
110 }
Al Viro32301922011-11-25 00:10:28 -0500111 mnt->mnt_master = master;
Al Virofc7be132011-11-25 01:05:37 -0500112 CLEAR_MNT_SHARED(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -0500113 return 0;
114}
115
Nick Piggin99b7db72010-08-18 04:37:39 +1000116/*
117 * vfsmount lock must be held for write
118 */
Al Viro0f0afb12011-11-24 20:43:10 -0500119void change_mnt_propagation(struct mount *mnt, int type)
Ram Pai07b20882005-11-07 17:19:07 -0500120{
Ram Pai03e06e62005-11-07 17:19:33 -0500121 if (type == MS_SHARED) {
Ram Paib90fa9a2005-11-07 17:19:50 -0500122 set_mnt_shared(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -0500123 return;
124 }
Al Viro6fc78712011-11-24 23:35:54 -0500125 do_make_slave(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -0500126 if (type != MS_SLAVE) {
Al Viro6776db3d2011-11-25 00:22:05 -0500127 list_del_init(&mnt->mnt_slave);
Al Virod10e8de2011-11-25 00:07:16 -0500128 mnt->mnt_master = NULL;
Ram Pai9676f0c2005-11-07 17:21:20 -0500129 if (type == MS_UNBINDABLE)
Al Viro0f0afb12011-11-24 20:43:10 -0500130 mnt->mnt.mnt_flags |= MNT_UNBINDABLE;
Andries E. Brouwer0b03cfb2008-02-06 01:36:32 -0800131 else
Al Viro0f0afb12011-11-24 20:43:10 -0500132 mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;
Ram Pai03e06e62005-11-07 17:19:33 -0500133 }
Ram Pai07b20882005-11-07 17:19:07 -0500134}
Ram Paib90fa9a2005-11-07 17:19:50 -0500135
136/*
137 * get the next mount in the propagation tree.
138 * @m: the mount seen last
139 * @origin: the original mount from where the tree walk initiated
Al Viro796a6b52010-01-16 13:28:47 -0500140 *
141 * Note that peer groups form contiguous segments of slave lists.
142 * We rely on that in get_source() to be able to find out if
143 * vfsmount found while iterating with propagation_next() is
144 * a peer of one we'd found earlier.
Ram Paib90fa9a2005-11-07 17:19:50 -0500145 */
Al Viroc9371352011-11-24 23:56:26 -0500146static struct mount *propagation_next(struct mount *m,
147 struct mount *origin)
Ram Paib90fa9a2005-11-07 17:19:50 -0500148{
Ram Pai5afe0022005-11-07 17:21:01 -0500149 /* are there any slaves of this mount? */
Al Viro143c8c92011-11-25 00:46:35 -0500150 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
Ram Pai5afe0022005-11-07 17:21:01 -0500151 return first_slave(m);
152
153 while (1) {
Al Viro32301922011-11-25 00:10:28 -0500154 struct mount *master = m->mnt_master;
Ram Pai5afe0022005-11-07 17:21:01 -0500155
Al Viro32301922011-11-25 00:10:28 -0500156 if (master == origin->mnt_master) {
Al Viroc9371352011-11-24 23:56:26 -0500157 struct mount *next = next_peer(m);
158 return (next == origin) ? NULL : next;
Al Viro6776db3d2011-11-25 00:22:05 -0500159 } else if (m->mnt_slave.next != &master->mnt_slave_list)
Ram Pai5afe0022005-11-07 17:21:01 -0500160 return next_slave(m);
161
162 /* back at master */
163 m = master;
164 }
165}
166
167/*
168 * return the source mount to be used for cloning
169 *
170 * @dest the current destination mount
171 * @last_dest the last seen destination mount
172 * @last_src the last seen source mount
173 * @type return CL_SLAVE if the new mount has to be
174 * cloned as a slave.
175 */
Al Viroc9371352011-11-24 23:56:26 -0500176static struct mount *get_source(struct mount *dest,
177 struct mount *last_dest,
178 struct mount *last_src,
179 int *type)
Ram Pai5afe0022005-11-07 17:21:01 -0500180{
Al Viroc9371352011-11-24 23:56:26 -0500181 struct mount *p_last_src = NULL;
182 struct mount *p_last_dest = NULL;
Ram Pai5afe0022005-11-07 17:21:01 -0500183
Al Viro32301922011-11-25 00:10:28 -0500184 while (last_dest != dest->mnt_master) {
Ram Pai5afe0022005-11-07 17:21:01 -0500185 p_last_dest = last_dest;
186 p_last_src = last_src;
Al Viro32301922011-11-25 00:10:28 -0500187 last_dest = last_dest->mnt_master;
188 last_src = last_src->mnt_master;
Ram Pai5afe0022005-11-07 17:21:01 -0500189 }
190
191 if (p_last_dest) {
192 do {
193 p_last_dest = next_peer(p_last_dest);
Al Viro143c8c92011-11-25 00:46:35 -0500194 } while (IS_MNT_NEW(p_last_dest));
Al Viro796a6b52010-01-16 13:28:47 -0500195 /* is that a peer of the earlier? */
196 if (dest == p_last_dest) {
197 *type = CL_MAKE_SHARED;
198 return p_last_src;
199 }
Ram Pai5afe0022005-11-07 17:21:01 -0500200 }
Al Viro796a6b52010-01-16 13:28:47 -0500201 /* slave of the earlier, then */
202 *type = CL_SLAVE;
203 /* beginning of peer group among the slaves? */
Al Virofc7be132011-11-25 01:05:37 -0500204 if (IS_MNT_SHARED(dest))
Al Viro796a6b52010-01-16 13:28:47 -0500205 *type |= CL_MAKE_SHARED;
206 return last_src;
Ram Paib90fa9a2005-11-07 17:19:50 -0500207}
208
209/*
210 * mount 'source_mnt' under the destination 'dest_mnt' at
211 * dentry 'dest_dentry'. And propagate that mount to
212 * all the peer and slave mounts of 'dest_mnt'.
213 * Link all the new mounts into a propagation tree headed at
214 * source_mnt. Also link all the new mounts using ->mnt_list
215 * headed at source_mnt's ->mnt_list
216 *
217 * @dest_mnt: destination mount.
218 * @dest_dentry: destination dentry.
219 * @source_mnt: source mount.
220 * @tree_list : list of heads of trees to be attached.
221 */
Al Viro84d17192013-03-15 10:53:28 -0400222int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
Al Viroa8d56d82011-11-24 23:59:29 -0500223 struct mount *source_mnt, struct list_head *tree_list)
Ram Paib90fa9a2005-11-07 17:19:50 -0500224{
Eric W. Biederman132c94e2013-03-22 04:08:05 -0700225 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
Al Viroc9371352011-11-24 23:56:26 -0500226 struct mount *m, *child;
Ram Paib90fa9a2005-11-07 17:19:50 -0500227 int ret = 0;
Al Viroa8d56d82011-11-24 23:59:29 -0500228 struct mount *prev_dest_mnt = dest_mnt;
229 struct mount *prev_src_mnt = source_mnt;
Ram Paib90fa9a2005-11-07 17:19:50 -0500230 LIST_HEAD(tmp_list);
Ram Paib90fa9a2005-11-07 17:19:50 -0500231
Al Viroa8d56d82011-11-24 23:59:29 -0500232 for (m = propagation_next(dest_mnt, dest_mnt); m;
233 m = propagation_next(m, dest_mnt)) {
Ram Pai5afe0022005-11-07 17:21:01 -0500234 int type;
Al Viroc9371352011-11-24 23:56:26 -0500235 struct mount *source;
Ram Paib90fa9a2005-11-07 17:19:50 -0500236
Al Viro143c8c92011-11-25 00:46:35 -0500237 if (IS_MNT_NEW(m))
Ram Paib90fa9a2005-11-07 17:19:50 -0500238 continue;
239
Ram Pai5afe0022005-11-07 17:21:01 -0500240 source = get_source(m, prev_dest_mnt, prev_src_mnt, &type);
Ram Paib90fa9a2005-11-07 17:19:50 -0500241
Eric W. Biederman132c94e2013-03-22 04:08:05 -0700242 /* Notice when we are propagating across user namespaces */
243 if (m->mnt_ns->user_ns != user_ns)
244 type |= CL_UNPRIVILEGED;
245
David Howellsbe34d1a2012-06-25 12:55:18 +0100246 child = copy_tree(source, source->mnt.mnt_root, type);
247 if (IS_ERR(child)) {
248 ret = PTR_ERR(child);
Ram Paib90fa9a2005-11-07 17:19:50 -0500249 list_splice(tree_list, tmp_list.prev);
250 goto out;
251 }
252
Al Viro84d17192013-03-15 10:53:28 -0400253 if (is_subdir(dest_mp->m_dentry, m->mnt.mnt_root)) {
254 mnt_set_mountpoint(m, dest_mp, child);
Al Viro1b8e5562011-11-24 21:01:32 -0500255 list_add_tail(&child->mnt_hash, tree_list);
Ram Paib90fa9a2005-11-07 17:19:50 -0500256 } else {
257 /*
258 * This can happen if the parent mount was bind mounted
259 * on some subdirectory of a shared/slave mount.
260 */
Al Viro1b8e5562011-11-24 21:01:32 -0500261 list_add_tail(&child->mnt_hash, &tmp_list);
Ram Paib90fa9a2005-11-07 17:19:50 -0500262 }
263 prev_dest_mnt = m;
Al Viroc9371352011-11-24 23:56:26 -0500264 prev_src_mnt = child;
Ram Paib90fa9a2005-11-07 17:19:50 -0500265 }
266out:
Al Viro719ea2f2013-09-29 11:24:49 -0400267 lock_mount_hash();
Ram Paib90fa9a2005-11-07 17:19:50 -0500268 while (!list_empty(&tmp_list)) {
Al Viro1b8e5562011-11-24 21:01:32 -0500269 child = list_first_entry(&tmp_list, struct mount, mnt_hash);
Al Viro328e6d92013-03-16 14:49:45 -0400270 umount_tree(child, 0);
Ram Paib90fa9a2005-11-07 17:19:50 -0500271 }
Al Viro719ea2f2013-09-29 11:24:49 -0400272 unlock_mount_hash();
Ram Paib90fa9a2005-11-07 17:19:50 -0500273 return ret;
274}
Ram Paia05964f2005-11-07 17:20:17 -0500275
276/*
277 * return true if the refcount is greater than count
278 */
Al Viro1ab59732011-11-24 21:35:16 -0500279static inline int do_refcount_check(struct mount *mnt, int count)
Ram Paia05964f2005-11-07 17:20:17 -0500280{
Al Viroaba809cf2013-09-28 23:10:55 -0400281 return mnt_get_count(mnt) > count;
Ram Paia05964f2005-11-07 17:20:17 -0500282}
283
284/*
285 * check if the mount 'mnt' can be unmounted successfully.
286 * @mnt: the mount to be checked for unmount
287 * NOTE: unmounting 'mnt' would naturally propagate to all
288 * other mounts its parent propagates to.
289 * Check if any of these mounts that **do not have submounts**
290 * have more references than 'refcnt'. If so return busy.
Nick Piggin99b7db72010-08-18 04:37:39 +1000291 *
Nick Pigginb3e19d92011-01-07 17:50:11 +1100292 * vfsmount lock must be held for write
Ram Paia05964f2005-11-07 17:20:17 -0500293 */
Al Viro1ab59732011-11-24 21:35:16 -0500294int propagate_mount_busy(struct mount *mnt, int refcnt)
Ram Paia05964f2005-11-07 17:20:17 -0500295{
Al Viroc9371352011-11-24 23:56:26 -0500296 struct mount *m, *child;
Al Viro0714a532011-11-24 22:19:58 -0500297 struct mount *parent = mnt->mnt_parent;
Ram Paia05964f2005-11-07 17:20:17 -0500298 int ret = 0;
299
Al Viro0714a532011-11-24 22:19:58 -0500300 if (mnt == parent)
Ram Paia05964f2005-11-07 17:20:17 -0500301 return do_refcount_check(mnt, refcnt);
302
303 /*
304 * quickly check if the current mount can be unmounted.
305 * If not, we don't have to go checking for all other
306 * mounts
307 */
Al Viro6b41d532011-11-24 23:24:33 -0500308 if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
Ram Paia05964f2005-11-07 17:20:17 -0500309 return 1;
310
Al Viroc9371352011-11-24 23:56:26 -0500311 for (m = propagation_next(parent, parent); m;
312 m = propagation_next(m, parent)) {
Al Viro474279d2013-10-01 16:11:26 -0400313 child = __lookup_mnt_last(&m->mnt, mnt->mnt_mountpoint);
Al Viro6b41d532011-11-24 23:24:33 -0500314 if (child && list_empty(&child->mnt_mounts) &&
Al Viro1ab59732011-11-24 21:35:16 -0500315 (ret = do_refcount_check(child, 1)))
Ram Paia05964f2005-11-07 17:20:17 -0500316 break;
317 }
318 return ret;
319}
320
321/*
322 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
323 * parent propagates to.
324 */
Al Viro61ef47b2011-11-24 18:25:28 -0500325static void __propagate_umount(struct mount *mnt)
Ram Paia05964f2005-11-07 17:20:17 -0500326{
Al Viro0714a532011-11-24 22:19:58 -0500327 struct mount *parent = mnt->mnt_parent;
Al Viroc9371352011-11-24 23:56:26 -0500328 struct mount *m;
Ram Paia05964f2005-11-07 17:20:17 -0500329
Al Viro0714a532011-11-24 22:19:58 -0500330 BUG_ON(parent == mnt);
Ram Paia05964f2005-11-07 17:20:17 -0500331
Al Viroc9371352011-11-24 23:56:26 -0500332 for (m = propagation_next(parent, parent); m;
333 m = propagation_next(m, parent)) {
Ram Paia05964f2005-11-07 17:20:17 -0500334
Al Viro474279d2013-10-01 16:11:26 -0400335 struct mount *child = __lookup_mnt_last(&m->mnt,
336 mnt->mnt_mountpoint);
Ram Paia05964f2005-11-07 17:20:17 -0500337 /*
338 * umount the child only if the child has no
339 * other children
340 */
Al Viro6b41d532011-11-24 23:24:33 -0500341 if (child && list_empty(&child->mnt_mounts))
Al Viro1b8e5562011-11-24 21:01:32 -0500342 list_move_tail(&child->mnt_hash, &mnt->mnt_hash);
Ram Paia05964f2005-11-07 17:20:17 -0500343 }
344}
345
346/*
347 * collect all mounts that receive propagation from the mount in @list,
348 * and return these additional mounts in the same list.
349 * @list: the list of mounts to be unmounted.
Nick Piggin99b7db72010-08-18 04:37:39 +1000350 *
351 * vfsmount lock must be held for write
Ram Paia05964f2005-11-07 17:20:17 -0500352 */
353int propagate_umount(struct list_head *list)
354{
Al Viro61ef47b2011-11-24 18:25:28 -0500355 struct mount *mnt;
Ram Paia05964f2005-11-07 17:20:17 -0500356
Al Viro1b8e5562011-11-24 21:01:32 -0500357 list_for_each_entry(mnt, list, mnt_hash)
Ram Paia05964f2005-11-07 17:20:17 -0500358 __propagate_umount(mnt);
359 return 0;
360}