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07b20889 RP |
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/namespace.h> | |
10 | #include <linux/mount.h> | |
11 | #include <linux/fs.h> | |
12 | #include "pnode.h" | |
13 | ||
03e06e68 RP |
14 | /* return the next shared peer mount of @p */ |
15 | static inline struct vfsmount *next_peer(struct vfsmount *p) | |
16 | { | |
17 | return list_entry(p->mnt_share.next, struct vfsmount, mnt_share); | |
18 | } | |
19 | ||
07b20889 RP |
20 | void change_mnt_propagation(struct vfsmount *mnt, int type) |
21 | { | |
03e06e68 | 22 | if (type == MS_SHARED) { |
b90fa9ae | 23 | set_mnt_shared(mnt); |
03e06e68 RP |
24 | } else { |
25 | list_del_init(&mnt->mnt_share); | |
26 | mnt->mnt_flags &= ~MNT_PNODE_MASK; | |
27 | } | |
07b20889 | 28 | } |
b90fa9ae RP |
29 | |
30 | /* | |
31 | * get the next mount in the propagation tree. | |
32 | * @m: the mount seen last | |
33 | * @origin: the original mount from where the tree walk initiated | |
34 | */ | |
35 | static struct vfsmount *propagation_next(struct vfsmount *m, | |
36 | struct vfsmount *origin) | |
37 | { | |
38 | m = next_peer(m); | |
39 | if (m == origin) | |
40 | return NULL; | |
41 | return m; | |
42 | } | |
43 | ||
44 | /* | |
45 | * mount 'source_mnt' under the destination 'dest_mnt' at | |
46 | * dentry 'dest_dentry'. And propagate that mount to | |
47 | * all the peer and slave mounts of 'dest_mnt'. | |
48 | * Link all the new mounts into a propagation tree headed at | |
49 | * source_mnt. Also link all the new mounts using ->mnt_list | |
50 | * headed at source_mnt's ->mnt_list | |
51 | * | |
52 | * @dest_mnt: destination mount. | |
53 | * @dest_dentry: destination dentry. | |
54 | * @source_mnt: source mount. | |
55 | * @tree_list : list of heads of trees to be attached. | |
56 | */ | |
57 | int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry, | |
58 | struct vfsmount *source_mnt, struct list_head *tree_list) | |
59 | { | |
60 | struct vfsmount *m, *child; | |
61 | int ret = 0; | |
62 | struct vfsmount *prev_dest_mnt = dest_mnt; | |
63 | struct vfsmount *prev_src_mnt = source_mnt; | |
64 | LIST_HEAD(tmp_list); | |
65 | LIST_HEAD(umount_list); | |
66 | ||
67 | for (m = propagation_next(dest_mnt, dest_mnt); m; | |
68 | m = propagation_next(m, dest_mnt)) { | |
69 | int type = CL_PROPAGATION; | |
70 | ||
71 | if (IS_MNT_NEW(m)) | |
72 | continue; | |
73 | ||
74 | if (IS_MNT_SHARED(m)) | |
75 | type |= CL_MAKE_SHARED; | |
76 | ||
77 | if (!(child = copy_tree(source_mnt, source_mnt->mnt_root, | |
78 | type))) { | |
79 | ret = -ENOMEM; | |
80 | list_splice(tree_list, tmp_list.prev); | |
81 | goto out; | |
82 | } | |
83 | ||
84 | if (is_subdir(dest_dentry, m->mnt_root)) { | |
85 | mnt_set_mountpoint(m, dest_dentry, child); | |
86 | list_add_tail(&child->mnt_hash, tree_list); | |
87 | } else { | |
88 | /* | |
89 | * This can happen if the parent mount was bind mounted | |
90 | * on some subdirectory of a shared/slave mount. | |
91 | */ | |
92 | list_add_tail(&child->mnt_hash, &tmp_list); | |
93 | } | |
94 | prev_dest_mnt = m; | |
95 | prev_src_mnt = child; | |
96 | } | |
97 | out: | |
98 | spin_lock(&vfsmount_lock); | |
99 | while (!list_empty(&tmp_list)) { | |
100 | child = list_entry(tmp_list.next, struct vfsmount, mnt_hash); | |
101 | list_del_init(&child->mnt_hash); | |
a05964f3 | 102 | umount_tree(child, 0, &umount_list); |
b90fa9ae RP |
103 | } |
104 | spin_unlock(&vfsmount_lock); | |
105 | release_mounts(&umount_list); | |
106 | return ret; | |
107 | } | |
a05964f3 RP |
108 | |
109 | /* | |
110 | * return true if the refcount is greater than count | |
111 | */ | |
112 | static inline int do_refcount_check(struct vfsmount *mnt, int count) | |
113 | { | |
114 | int mycount = atomic_read(&mnt->mnt_count); | |
115 | return (mycount > count); | |
116 | } | |
117 | ||
118 | /* | |
119 | * check if the mount 'mnt' can be unmounted successfully. | |
120 | * @mnt: the mount to be checked for unmount | |
121 | * NOTE: unmounting 'mnt' would naturally propagate to all | |
122 | * other mounts its parent propagates to. | |
123 | * Check if any of these mounts that **do not have submounts** | |
124 | * have more references than 'refcnt'. If so return busy. | |
125 | */ | |
126 | int propagate_mount_busy(struct vfsmount *mnt, int refcnt) | |
127 | { | |
128 | struct vfsmount *m, *child; | |
129 | struct vfsmount *parent = mnt->mnt_parent; | |
130 | int ret = 0; | |
131 | ||
132 | if (mnt == parent) | |
133 | return do_refcount_check(mnt, refcnt); | |
134 | ||
135 | /* | |
136 | * quickly check if the current mount can be unmounted. | |
137 | * If not, we don't have to go checking for all other | |
138 | * mounts | |
139 | */ | |
140 | if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt)) | |
141 | return 1; | |
142 | ||
143 | for (m = propagation_next(parent, parent); m; | |
144 | m = propagation_next(m, parent)) { | |
145 | child = __lookup_mnt(m, mnt->mnt_mountpoint, 0); | |
146 | if (child && list_empty(&child->mnt_mounts) && | |
147 | (ret = do_refcount_check(child, 1))) | |
148 | break; | |
149 | } | |
150 | return ret; | |
151 | } | |
152 | ||
153 | /* | |
154 | * NOTE: unmounting 'mnt' naturally propagates to all other mounts its | |
155 | * parent propagates to. | |
156 | */ | |
157 | static void __propagate_umount(struct vfsmount *mnt) | |
158 | { | |
159 | struct vfsmount *parent = mnt->mnt_parent; | |
160 | struct vfsmount *m; | |
161 | ||
162 | BUG_ON(parent == mnt); | |
163 | ||
164 | for (m = propagation_next(parent, parent); m; | |
165 | m = propagation_next(m, parent)) { | |
166 | ||
167 | struct vfsmount *child = __lookup_mnt(m, | |
168 | mnt->mnt_mountpoint, 0); | |
169 | /* | |
170 | * umount the child only if the child has no | |
171 | * other children | |
172 | */ | |
173 | if (child && list_empty(&child->mnt_mounts)) { | |
174 | list_del(&child->mnt_hash); | |
175 | list_add_tail(&child->mnt_hash, &mnt->mnt_hash); | |
176 | } | |
177 | } | |
178 | } | |
179 | ||
180 | /* | |
181 | * collect all mounts that receive propagation from the mount in @list, | |
182 | * and return these additional mounts in the same list. | |
183 | * @list: the list of mounts to be unmounted. | |
184 | */ | |
185 | int propagate_umount(struct list_head *list) | |
186 | { | |
187 | struct vfsmount *mnt; | |
188 | ||
189 | list_for_each_entry(mnt, list, mnt_hash) | |
190 | __propagate_umount(mnt); | |
191 | return 0; | |
192 | } |