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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 */
9#include <linux/namespace.h>
10#include <linux/mount.h>
11#include <linux/fs.h>
12#include "pnode.h"
13
Ram Pai03e06e62005-11-07 17:19:33 -050014/* return the next shared peer mount of @p */
15static inline struct vfsmount *next_peer(struct vfsmount *p)
16{
17 return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);
18}
19
Ram Pai5afe0022005-11-07 17:21:01 -050020static inline struct vfsmount *first_slave(struct vfsmount *p)
21{
22 return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave);
23}
24
25static inline struct vfsmount *next_slave(struct vfsmount *p)
26{
27 return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);
28}
29
Ram Paia58b0eb2005-11-07 17:20:48 -050030static int do_make_slave(struct vfsmount *mnt)
31{
32 struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
33 struct vfsmount *slave_mnt;
34
35 /*
36 * slave 'mnt' to a peer mount that has the
37 * same root dentry. If none is available than
38 * slave it to anything that is available.
39 */
40 while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
41 peer_mnt->mnt_root != mnt->mnt_root) ;
42
43 if (peer_mnt == mnt) {
44 peer_mnt = next_peer(mnt);
45 if (peer_mnt == mnt)
46 peer_mnt = NULL;
47 }
48 list_del_init(&mnt->mnt_share);
49
50 if (peer_mnt)
51 master = peer_mnt;
52
53 if (master) {
54 list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
55 slave_mnt->mnt_master = master;
56 list_del(&mnt->mnt_slave);
57 list_add(&mnt->mnt_slave, &master->mnt_slave_list);
58 list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
59 INIT_LIST_HEAD(&mnt->mnt_slave_list);
60 } else {
61 struct list_head *p = &mnt->mnt_slave_list;
62 while (!list_empty(p)) {
63 slave_mnt = list_entry(p->next,
64 struct vfsmount, mnt_slave);
65 list_del_init(&slave_mnt->mnt_slave);
66 slave_mnt->mnt_master = NULL;
67 }
68 }
69 mnt->mnt_master = master;
70 CLEAR_MNT_SHARED(mnt);
71 INIT_LIST_HEAD(&mnt->mnt_slave_list);
72 return 0;
73}
74
Ram Pai07b20882005-11-07 17:19:07 -050075void change_mnt_propagation(struct vfsmount *mnt, int type)
76{
Ram Pai03e06e62005-11-07 17:19:33 -050077 if (type == MS_SHARED) {
Ram Paib90fa9a2005-11-07 17:19:50 -050078 set_mnt_shared(mnt);
Ram Paia58b0eb2005-11-07 17:20:48 -050079 return;
80 }
81 do_make_slave(mnt);
82 if (type != MS_SLAVE) {
83 list_del_init(&mnt->mnt_slave);
84 mnt->mnt_master = NULL;
Ram Pai9676f0c2005-11-07 17:21:20 -050085 if (type == MS_UNBINDABLE)
86 mnt->mnt_flags |= MNT_UNBINDABLE;
Ram Pai03e06e62005-11-07 17:19:33 -050087 }
Ram Pai07b20882005-11-07 17:19:07 -050088}
Ram Paib90fa9a2005-11-07 17:19:50 -050089
90/*
91 * get the next mount in the propagation tree.
92 * @m: the mount seen last
93 * @origin: the original mount from where the tree walk initiated
94 */
95static struct vfsmount *propagation_next(struct vfsmount *m,
96 struct vfsmount *origin)
97{
Ram Pai5afe0022005-11-07 17:21:01 -050098 /* are there any slaves of this mount? */
99 if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
100 return first_slave(m);
101
102 while (1) {
103 struct vfsmount *next;
104 struct vfsmount *master = m->mnt_master;
105
106 if ( master == origin->mnt_master ) {
107 next = next_peer(m);
108 return ((next == origin) ? NULL : next);
109 } else if (m->mnt_slave.next != &master->mnt_slave_list)
110 return next_slave(m);
111
112 /* back at master */
113 m = master;
114 }
115}
116
117/*
118 * return the source mount to be used for cloning
119 *
120 * @dest the current destination mount
121 * @last_dest the last seen destination mount
122 * @last_src the last seen source mount
123 * @type return CL_SLAVE if the new mount has to be
124 * cloned as a slave.
125 */
126static struct vfsmount *get_source(struct vfsmount *dest,
127 struct vfsmount *last_dest,
128 struct vfsmount *last_src,
129 int *type)
130{
131 struct vfsmount *p_last_src = NULL;
132 struct vfsmount *p_last_dest = NULL;
133 *type = CL_PROPAGATION;;
134
135 if (IS_MNT_SHARED(dest))
136 *type |= CL_MAKE_SHARED;
137
138 while (last_dest != dest->mnt_master) {
139 p_last_dest = last_dest;
140 p_last_src = last_src;
141 last_dest = last_dest->mnt_master;
142 last_src = last_src->mnt_master;
143 }
144
145 if (p_last_dest) {
146 do {
147 p_last_dest = next_peer(p_last_dest);
148 } while (IS_MNT_NEW(p_last_dest));
149 }
150
151 if (dest != p_last_dest) {
152 *type |= CL_SLAVE;
153 return last_src;
154 } else
155 return p_last_src;
Ram Paib90fa9a2005-11-07 17:19:50 -0500156}
157
158/*
159 * mount 'source_mnt' under the destination 'dest_mnt' at
160 * dentry 'dest_dentry'. And propagate that mount to
161 * all the peer and slave mounts of 'dest_mnt'.
162 * Link all the new mounts into a propagation tree headed at
163 * source_mnt. Also link all the new mounts using ->mnt_list
164 * headed at source_mnt's ->mnt_list
165 *
166 * @dest_mnt: destination mount.
167 * @dest_dentry: destination dentry.
168 * @source_mnt: source mount.
169 * @tree_list : list of heads of trees to be attached.
170 */
171int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry,
172 struct vfsmount *source_mnt, struct list_head *tree_list)
173{
174 struct vfsmount *m, *child;
175 int ret = 0;
176 struct vfsmount *prev_dest_mnt = dest_mnt;
177 struct vfsmount *prev_src_mnt = source_mnt;
178 LIST_HEAD(tmp_list);
179 LIST_HEAD(umount_list);
180
181 for (m = propagation_next(dest_mnt, dest_mnt); m;
182 m = propagation_next(m, dest_mnt)) {
Ram Pai5afe0022005-11-07 17:21:01 -0500183 int type;
184 struct vfsmount *source;
Ram Paib90fa9a2005-11-07 17:19:50 -0500185
186 if (IS_MNT_NEW(m))
187 continue;
188
Ram Pai5afe0022005-11-07 17:21:01 -0500189 source = get_source(m, prev_dest_mnt, prev_src_mnt, &type);
Ram Paib90fa9a2005-11-07 17:19:50 -0500190
Ram Pai5afe0022005-11-07 17:21:01 -0500191 if (!(child = copy_tree(source, source->mnt_root, type))) {
Ram Paib90fa9a2005-11-07 17:19:50 -0500192 ret = -ENOMEM;
193 list_splice(tree_list, tmp_list.prev);
194 goto out;
195 }
196
197 if (is_subdir(dest_dentry, m->mnt_root)) {
198 mnt_set_mountpoint(m, dest_dentry, child);
199 list_add_tail(&child->mnt_hash, tree_list);
200 } else {
201 /*
202 * This can happen if the parent mount was bind mounted
203 * on some subdirectory of a shared/slave mount.
204 */
205 list_add_tail(&child->mnt_hash, &tmp_list);
206 }
207 prev_dest_mnt = m;
208 prev_src_mnt = child;
209 }
210out:
211 spin_lock(&vfsmount_lock);
212 while (!list_empty(&tmp_list)) {
213 child = list_entry(tmp_list.next, struct vfsmount, mnt_hash);
214 list_del_init(&child->mnt_hash);
Ram Paia05964f2005-11-07 17:20:17 -0500215 umount_tree(child, 0, &umount_list);
Ram Paib90fa9a2005-11-07 17:19:50 -0500216 }
217 spin_unlock(&vfsmount_lock);
218 release_mounts(&umount_list);
219 return ret;
220}
Ram Paia05964f2005-11-07 17:20:17 -0500221
222/*
223 * return true if the refcount is greater than count
224 */
225static inline int do_refcount_check(struct vfsmount *mnt, int count)
226{
227 int mycount = atomic_read(&mnt->mnt_count);
228 return (mycount > count);
229}
230
231/*
232 * check if the mount 'mnt' can be unmounted successfully.
233 * @mnt: the mount to be checked for unmount
234 * NOTE: unmounting 'mnt' would naturally propagate to all
235 * other mounts its parent propagates to.
236 * Check if any of these mounts that **do not have submounts**
237 * have more references than 'refcnt'. If so return busy.
238 */
239int propagate_mount_busy(struct vfsmount *mnt, int refcnt)
240{
241 struct vfsmount *m, *child;
242 struct vfsmount *parent = mnt->mnt_parent;
243 int ret = 0;
244
245 if (mnt == parent)
246 return do_refcount_check(mnt, refcnt);
247
248 /*
249 * quickly check if the current mount can be unmounted.
250 * If not, we don't have to go checking for all other
251 * mounts
252 */
253 if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
254 return 1;
255
256 for (m = propagation_next(parent, parent); m;
257 m = propagation_next(m, parent)) {
258 child = __lookup_mnt(m, mnt->mnt_mountpoint, 0);
259 if (child && list_empty(&child->mnt_mounts) &&
260 (ret = do_refcount_check(child, 1)))
261 break;
262 }
263 return ret;
264}
265
266/*
267 * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
268 * parent propagates to.
269 */
270static void __propagate_umount(struct vfsmount *mnt)
271{
272 struct vfsmount *parent = mnt->mnt_parent;
273 struct vfsmount *m;
274
275 BUG_ON(parent == mnt);
276
277 for (m = propagation_next(parent, parent); m;
278 m = propagation_next(m, parent)) {
279
280 struct vfsmount *child = __lookup_mnt(m,
281 mnt->mnt_mountpoint, 0);
282 /*
283 * umount the child only if the child has no
284 * other children
285 */
286 if (child && list_empty(&child->mnt_mounts)) {
287 list_del(&child->mnt_hash);
288 list_add_tail(&child->mnt_hash, &mnt->mnt_hash);
289 }
290 }
291}
292
293/*
294 * collect all mounts that receive propagation from the mount in @list,
295 * and return these additional mounts in the same list.
296 * @list: the list of mounts to be unmounted.
297 */
298int propagate_umount(struct list_head *list)
299{
300 struct vfsmount *mnt;
301
302 list_for_each_entry(mnt, list, mnt_hash)
303 __propagate_umount(mnt);
304 return 0;
305}