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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 }
Al Virofc7be132011-11-25 01:05:37 -050086 if (IS_MNT_SHARED(mnt) && list_empty(&mnt->mnt_share))
Al Viro6fc78712011-11-24 23:35:54 -050087 mnt_release_group_id(mnt);
Miklos Szeredi719f5d72008-03-27 13:06:23 +010088
Al Viro6776db3d2011-11-25 00:22:05 -050089 list_del_init(&mnt->mnt_share);
Al Viro15169fe2011-11-25 00:50:41 -050090 mnt->mnt_group_id = 0;
Ram Paia58b0eb2005-11-07 17:20:48 -050091
92 if (peer_mnt)
93 master = peer_mnt;
94
95 if (master) {
Al Viro6776db3d2011-11-25 00:22:05 -050096 list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
Al Viro32301922011-11-25 00:10:28 -050097 slave_mnt->mnt_master = master;
Al Viro6776db3d2011-11-25 00:22:05 -050098 list_move(&mnt->mnt_slave, &master->mnt_slave_list);
99 list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
100 INIT_LIST_HEAD(&mnt->mnt_slave_list);
Ram Paia58b0eb2005-11-07 17:20:48 -0500101 } else {
Al Viro6776db3d2011-11-25 00:22:05 -0500102 struct list_head *p = &mnt->mnt_slave_list;
Ram Paia58b0eb2005-11-07 17:20:48 -0500103 while (!list_empty(p)) {
Pavel Emelianovb5e61812007-05-08 00:30:19 -0700104 slave_mnt = list_first_entry(p,
Al Viro6776db3d2011-11-25 00:22:05 -0500105 struct mount, mnt_slave);
106 list_del_init(&slave_mnt->mnt_slave);
Ram Paia58b0eb2005-11-07 17:20:48 -0500107 slave_mnt->mnt_master = NULL;
108 }
109 }
Al Viro32301922011-11-25 00:10:28 -0500110 mnt->mnt_master = master;
Al Virofc7be132011-11-25 01:05:37 -0500111 CLEAR_MNT_SHARED(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -0500112 return 0;
113}
114
Nick Piggin99b7db72010-08-18 04:37:39 +1000115/*
116 * vfsmount lock must be held for write
117 */
Al Viro0f0afb12011-11-24 20:43:10 -0500118void change_mnt_propagation(struct mount *mnt, int type)
Ram Pai07b20882005-11-07 17:19:07 -0500119{
Ram Pai03e06e62005-11-07 17:19:33 -0500120 if (type == MS_SHARED) {
Ram Paib90fa9a2005-11-07 17:19:50 -0500121 set_mnt_shared(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -0500122 return;
123 }
Al Viro6fc78712011-11-24 23:35:54 -0500124 do_make_slave(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -0500125 if (type != MS_SLAVE) {
Al Viro6776db3d2011-11-25 00:22:05 -0500126 list_del_init(&mnt->mnt_slave);
Al Virod10e8de2011-11-25 00:07:16 -0500127 mnt->mnt_master = NULL;
Ram Pai9676f0c2005-11-07 17:21:20 -0500128 if (type == MS_UNBINDABLE)
Al Viro0f0afb12011-11-24 20:43:10 -0500129 mnt->mnt.mnt_flags |= MNT_UNBINDABLE;
Andries E. Brouwer0b03cfb2008-02-06 01:36:32 -0800130 else
Al Viro0f0afb12011-11-24 20:43:10 -0500131 mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;
Ram Pai03e06e62005-11-07 17:19:33 -0500132 }
Ram Pai07b20882005-11-07 17:19:07 -0500133}
Ram Paib90fa9a2005-11-07 17:19:50 -0500134
135/*
136 * get the next mount in the propagation tree.
137 * @m: the mount seen last
138 * @origin: the original mount from where the tree walk initiated
Al Viro796a6b52010-01-16 13:28:47 -0500139 *
140 * Note that peer groups form contiguous segments of slave lists.
141 * We rely on that in get_source() to be able to find out if
142 * vfsmount found while iterating with propagation_next() is
143 * a peer of one we'd found earlier.
Ram Paib90fa9a2005-11-07 17:19:50 -0500144 */
Al Viroc9371352011-11-24 23:56:26 -0500145static struct mount *propagation_next(struct mount *m,
146 struct mount *origin)
Ram Paib90fa9a2005-11-07 17:19:50 -0500147{
Ram Pai5afe0022005-11-07 17:21:01 -0500148 /* are there any slaves of this mount? */
Al Viro143c8c92011-11-25 00:46:35 -0500149 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
Ram Pai5afe0022005-11-07 17:21:01 -0500150 return first_slave(m);
151
152 while (1) {
Al Viro32301922011-11-25 00:10:28 -0500153 struct mount *master = m->mnt_master;
Ram Pai5afe0022005-11-07 17:21:01 -0500154
Al Viro32301922011-11-25 00:10:28 -0500155 if (master == origin->mnt_master) {
Al Viroc9371352011-11-24 23:56:26 -0500156 struct mount *next = next_peer(m);
157 return (next == origin) ? NULL : next;
Al Viro6776db3d2011-11-25 00:22:05 -0500158 } else if (m->mnt_slave.next != &master->mnt_slave_list)
Ram Pai5afe0022005-11-07 17:21:01 -0500159 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 */
Al Viroc9371352011-11-24 23:56:26 -0500175static struct mount *get_source(struct mount *dest,
176 struct mount *last_dest,
177 struct mount *last_src,
178 int *type)
Ram Pai5afe0022005-11-07 17:21:01 -0500179{
Al Viroc9371352011-11-24 23:56:26 -0500180 struct mount *p_last_src = NULL;
181 struct mount *p_last_dest = NULL;
Ram Pai5afe0022005-11-07 17:21:01 -0500182
Al Viro32301922011-11-25 00:10:28 -0500183 while (last_dest != dest->mnt_master) {
Ram Pai5afe0022005-11-07 17:21:01 -0500184 p_last_dest = last_dest;
185 p_last_src = last_src;
Al Viro32301922011-11-25 00:10:28 -0500186 last_dest = last_dest->mnt_master;
187 last_src = last_src->mnt_master;
Ram Pai5afe0022005-11-07 17:21:01 -0500188 }
189
190 if (p_last_dest) {
191 do {
192 p_last_dest = next_peer(p_last_dest);
Al Viro143c8c92011-11-25 00:46:35 -0500193 } while (IS_MNT_NEW(p_last_dest));
Al Viro796a6b52010-01-16 13:28:47 -0500194 /* is that a peer of the earlier? */
195 if (dest == p_last_dest) {
196 *type = CL_MAKE_SHARED;
197 return p_last_src;
198 }
Ram Pai5afe0022005-11-07 17:21:01 -0500199 }
Al Viro796a6b52010-01-16 13:28:47 -0500200 /* slave of the earlier, then */
201 *type = CL_SLAVE;
202 /* beginning of peer group among the slaves? */
Al Virofc7be132011-11-25 01:05:37 -0500203 if (IS_MNT_SHARED(dest))
Al Viro796a6b52010-01-16 13:28:47 -0500204 *type |= CL_MAKE_SHARED;
205 return last_src;
Ram Paib90fa9a2005-11-07 17:19:50 -0500206}
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 */
Al Viroa8d56d82011-11-24 23:59:29 -0500221int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,
222 struct mount *source_mnt, struct list_head *tree_list)
Ram Paib90fa9a2005-11-07 17:19:50 -0500223{
Eric W. Biederman132c94e2013-03-22 04:08:05 -0700224 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
Al Viroc9371352011-11-24 23:56:26 -0500225 struct mount *m, *child;
Ram Paib90fa9a2005-11-07 17:19:50 -0500226 int ret = 0;
Al Viroa8d56d82011-11-24 23:59:29 -0500227 struct mount *prev_dest_mnt = dest_mnt;
228 struct mount *prev_src_mnt = source_mnt;
Ram Paib90fa9a2005-11-07 17:19:50 -0500229 LIST_HEAD(tmp_list);
230 LIST_HEAD(umount_list);
231
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 Viroc9371352011-11-24 23:56:26 -0500253 if (is_subdir(dest_dentry, m->mnt.mnt_root)) {
Al Viro14cf1fa2011-11-25 00:01:17 -0500254 mnt_set_mountpoint(m, dest_dentry, 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:
Andi Kleen962830d2012-05-08 13:32:02 +0930267 br_write_lock(&vfsmount_lock);
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 Viro761d5c32011-11-24 21:07:43 -0500270 umount_tree(child, 0, &umount_list);
Ram Paib90fa9a2005-11-07 17:19:50 -0500271 }
Andi Kleen962830d2012-05-08 13:32:02 +0930272 br_write_unlock(&vfsmount_lock);
Ram Paib90fa9a2005-11-07 17:19:50 -0500273 release_mounts(&umount_list);
274 return ret;
275}
Ram Paia05964f2005-11-07 17:20:17 -0500276
277/*
278 * return true if the refcount is greater than count
279 */
Al Viro1ab59732011-11-24 21:35:16 -0500280static inline int do_refcount_check(struct mount *mnt, int count)
Ram Paia05964f2005-11-07 17:20:17 -0500281{
Al Viro863d6842011-11-25 00:57:42 -0500282 int mycount = mnt_get_count(mnt) - mnt->mnt_ghosts;
Ram Paia05964f2005-11-07 17:20:17 -0500283 return (mycount > count);
284}
285
286/*
287 * check if the mount 'mnt' can be unmounted successfully.
288 * @mnt: the mount to be checked for unmount
289 * NOTE: unmounting 'mnt' would naturally propagate to all
290 * other mounts its parent propagates to.
291 * Check if any of these mounts that **do not have submounts**
292 * have more references than 'refcnt'. If so return busy.
Nick Piggin99b7db72010-08-18 04:37:39 +1000293 *
Nick Pigginb3e19d92011-01-07 17:50:11 +1100294 * vfsmount lock must be held for write
Ram Paia05964f2005-11-07 17:20:17 -0500295 */
Al Viro1ab59732011-11-24 21:35:16 -0500296int propagate_mount_busy(struct mount *mnt, int refcnt)
Ram Paia05964f2005-11-07 17:20:17 -0500297{
Al Viroc9371352011-11-24 23:56:26 -0500298 struct mount *m, *child;
Al Viro0714a532011-11-24 22:19:58 -0500299 struct mount *parent = mnt->mnt_parent;
Ram Paia05964f2005-11-07 17:20:17 -0500300 int ret = 0;
301
Al Viro0714a532011-11-24 22:19:58 -0500302 if (mnt == parent)
Ram Paia05964f2005-11-07 17:20:17 -0500303 return do_refcount_check(mnt, refcnt);
304
305 /*
306 * quickly check if the current mount can be unmounted.
307 * If not, we don't have to go checking for all other
308 * mounts
309 */
Al Viro6b41d532011-11-24 23:24:33 -0500310 if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
Ram Paia05964f2005-11-07 17:20:17 -0500311 return 1;
312
Al Viroc9371352011-11-24 23:56:26 -0500313 for (m = propagation_next(parent, parent); m;
314 m = propagation_next(m, parent)) {
315 child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint, 0);
Al Viro6b41d532011-11-24 23:24:33 -0500316 if (child && list_empty(&child->mnt_mounts) &&
Al Viro1ab59732011-11-24 21:35:16 -0500317 (ret = do_refcount_check(child, 1)))
Ram Paia05964f2005-11-07 17:20:17 -0500318 break;
319 }
320 return ret;
321}
322
323/*
324 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
325 * parent propagates to.
326 */
Al Viro61ef47b2011-11-24 18:25:28 -0500327static void __propagate_umount(struct mount *mnt)
Ram Paia05964f2005-11-07 17:20:17 -0500328{
Al Viro0714a532011-11-24 22:19:58 -0500329 struct mount *parent = mnt->mnt_parent;
Al Viroc9371352011-11-24 23:56:26 -0500330 struct mount *m;
Ram Paia05964f2005-11-07 17:20:17 -0500331
Al Viro0714a532011-11-24 22:19:58 -0500332 BUG_ON(parent == mnt);
Ram Paia05964f2005-11-07 17:20:17 -0500333
Al Viroc9371352011-11-24 23:56:26 -0500334 for (m = propagation_next(parent, parent); m;
335 m = propagation_next(m, parent)) {
Ram Paia05964f2005-11-07 17:20:17 -0500336
Al Viroc9371352011-11-24 23:56:26 -0500337 struct mount *child = __lookup_mnt(&m->mnt,
Al Viroa73324d2011-11-24 22:25:07 -0500338 mnt->mnt_mountpoint, 0);
Ram Paia05964f2005-11-07 17:20:17 -0500339 /*
340 * umount the child only if the child has no
341 * other children
342 */
Al Viro6b41d532011-11-24 23:24:33 -0500343 if (child && list_empty(&child->mnt_mounts))
Al Viro1b8e5562011-11-24 21:01:32 -0500344 list_move_tail(&child->mnt_hash, &mnt->mnt_hash);
Ram Paia05964f2005-11-07 17:20:17 -0500345 }
346}
347
348/*
349 * collect all mounts that receive propagation from the mount in @list,
350 * and return these additional mounts in the same list.
351 * @list: the list of mounts to be unmounted.
Nick Piggin99b7db72010-08-18 04:37:39 +1000352 *
353 * vfsmount lock must be held for write
Ram Paia05964f2005-11-07 17:20:17 -0500354 */
355int propagate_umount(struct list_head *list)
356{
Al Viro61ef47b2011-11-24 18:25:28 -0500357 struct mount *mnt;
Ram Paia05964f2005-11-07 17:20:17 -0500358
Al Viro1b8e5562011-11-24 21:01:32 -0500359 list_for_each_entry(mnt, list, mnt_hash)
Ram Paia05964f2005-11-07 17:20:17 -0500360 __propagate_umount(mnt);
361 return 0;
362}