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90586523 EP |
1 | /* |
2 | * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2, or (at your option) | |
7 | * any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; see the file COPYING. If not, write to | |
16 | * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. | |
17 | */ | |
18 | ||
19 | #include <linux/list.h> | |
20 | #include <linux/mutex.h> | |
21 | #include <linux/slab.h> | |
22 | #include <linux/srcu.h> | |
23 | #include <linux/rculist.h> | |
24 | #include <linux/wait.h> | |
25 | ||
26 | #include <linux/fsnotify_backend.h> | |
27 | #include "fsnotify.h" | |
28 | ||
29 | #include <asm/atomic.h> | |
30 | ||
31 | /* protects writes to fsnotify_groups and fsnotify_mask */ | |
32 | static DEFINE_MUTEX(fsnotify_grp_mutex); | |
7131485a | 33 | /* all groups registered to receive inode filesystem notifications */ |
19c2a0e1 | 34 | LIST_HEAD(fsnotify_inode_groups); |
7131485a EP |
35 | /* all groups registered to receive mount point filesystem notifications */ |
36 | LIST_HEAD(fsnotify_vfsmount_groups); | |
90586523 | 37 | |
7131485a EP |
38 | void fsnotify_add_vfsmount_group(struct fsnotify_group *group) |
39 | { | |
cb2d429f | 40 | struct fsnotify_group *group_iter; |
cb2d429f | 41 | |
7131485a EP |
42 | mutex_lock(&fsnotify_grp_mutex); |
43 | ||
cb2d429f EP |
44 | if (!group->on_vfsmount_group_list) { |
45 | list_for_each_entry(group_iter, &fsnotify_vfsmount_groups, | |
46 | vfsmount_group_list) { | |
47 | /* insert in front of this one? */ | |
08ae8938 | 48 | if (group < group_iter) { |
cb2d429f EP |
49 | /* list_add_tail() insert in front of group_iter */ |
50 | list_add_tail_rcu(&group->inode_group_list, | |
51 | &group_iter->inode_group_list); | |
52 | goto out; | |
53 | } | |
54 | } | |
55 | ||
56 | /* apparently we need to be the last entry */ | |
7131485a | 57 | list_add_tail_rcu(&group->vfsmount_group_list, &fsnotify_vfsmount_groups); |
cb2d429f EP |
58 | } |
59 | out: | |
7131485a EP |
60 | group->on_vfsmount_group_list = 1; |
61 | ||
62 | mutex_unlock(&fsnotify_grp_mutex); | |
63 | } | |
64 | ||
4ca76352 | 65 | void fsnotify_add_inode_group(struct fsnotify_group *group) |
19c2a0e1 | 66 | { |
cb2d429f | 67 | struct fsnotify_group *group_iter; |
cb2d429f | 68 | |
4ca76352 | 69 | mutex_lock(&fsnotify_grp_mutex); |
19c2a0e1 | 70 | |
08ae8938 | 71 | /* add to global group list */ |
cb2d429f EP |
72 | if (!group->on_inode_group_list) { |
73 | list_for_each_entry(group_iter, &fsnotify_inode_groups, | |
74 | inode_group_list) { | |
08ae8938 | 75 | if (group < group_iter) { |
cb2d429f EP |
76 | /* list_add_tail() insert in front of group_iter */ |
77 | list_add_tail_rcu(&group->inode_group_list, | |
78 | &group_iter->inode_group_list); | |
79 | goto out; | |
80 | } | |
81 | } | |
82 | ||
83 | /* apparently we need to be the last entry */ | |
4ca76352 | 84 | list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups); |
cb2d429f EP |
85 | } |
86 | out: | |
19c2a0e1 | 87 | group->on_inode_group_list = 1; |
4ca76352 EP |
88 | |
89 | mutex_unlock(&fsnotify_grp_mutex); | |
19c2a0e1 EP |
90 | } |
91 | ||
90586523 EP |
92 | /* |
93 | * Final freeing of a group | |
94 | */ | |
3be25f49 | 95 | void fsnotify_final_destroy_group(struct fsnotify_group *group) |
90586523 | 96 | { |
a2d8bc6c EP |
97 | /* clear the notification queue of all events */ |
98 | fsnotify_flush_notify(group); | |
99 | ||
90586523 EP |
100 | if (group->ops->free_group_priv) |
101 | group->ops->free_group_priv(group); | |
102 | ||
103 | kfree(group); | |
104 | } | |
105 | ||
3be25f49 EP |
106 | /* |
107 | * Trying to get rid of a group. We need to first get rid of any outstanding | |
108 | * allocations and then free the group. Remember that fsnotify_clear_marks_by_group | |
109 | * could miss marks that are being freed by inode and those marks could still | |
110 | * hold a reference to this group (via group->num_marks) If we get into that | |
111 | * situtation, the fsnotify_final_destroy_group will get called when that final | |
112 | * mark is freed. | |
113 | */ | |
114 | static void fsnotify_destroy_group(struct fsnotify_group *group) | |
115 | { | |
e61ce867 | 116 | /* clear all inode marks for this group */ |
3be25f49 EP |
117 | fsnotify_clear_marks_by_group(group); |
118 | ||
75c1be48 EP |
119 | synchronize_srcu(&fsnotify_mark_srcu); |
120 | ||
3be25f49 EP |
121 | /* past the point of no return, matches the initial value of 1 */ |
122 | if (atomic_dec_and_test(&group->num_marks)) | |
123 | fsnotify_final_destroy_group(group); | |
124 | } | |
125 | ||
90586523 EP |
126 | /* |
127 | * Remove this group from the global list of groups that will get events | |
128 | * this can be done even if there are still references and things still using | |
129 | * this group. This just stops the group from getting new events. | |
130 | */ | |
131 | static void __fsnotify_evict_group(struct fsnotify_group *group) | |
132 | { | |
133 | BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex)); | |
134 | ||
19c2a0e1 EP |
135 | if (group->on_inode_group_list) |
136 | list_del_rcu(&group->inode_group_list); | |
137 | group->on_inode_group_list = 0; | |
7131485a EP |
138 | if (group->on_vfsmount_group_list) |
139 | list_del_rcu(&group->vfsmount_group_list); | |
140 | group->on_vfsmount_group_list = 0; | |
90586523 EP |
141 | } |
142 | ||
143 | /* | |
144 | * Called when a group is no longer interested in getting events. This can be | |
145 | * used if a group is misbehaving or if for some reason a group should no longer | |
146 | * get any filesystem events. | |
147 | */ | |
148 | void fsnotify_evict_group(struct fsnotify_group *group) | |
149 | { | |
150 | mutex_lock(&fsnotify_grp_mutex); | |
151 | __fsnotify_evict_group(group); | |
152 | mutex_unlock(&fsnotify_grp_mutex); | |
153 | } | |
154 | ||
155 | /* | |
156 | * Drop a reference to a group. Free it if it's through. | |
157 | */ | |
158 | void fsnotify_put_group(struct fsnotify_group *group) | |
159 | { | |
160 | if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex)) | |
161 | return; | |
162 | ||
163 | /* | |
164 | * OK, now we know that there's no other users *and* we hold mutex, | |
165 | * so no new references will appear | |
166 | */ | |
167 | __fsnotify_evict_group(group); | |
168 | ||
90586523 | 169 | mutex_unlock(&fsnotify_grp_mutex); |
90586523 | 170 | |
90586523 EP |
171 | fsnotify_destroy_group(group); |
172 | } | |
173 | ||
90586523 | 174 | /* |
ffab8340 | 175 | * Create a new fsnotify_group and hold a reference for the group returned. |
90586523 | 176 | */ |
0d2e2a1d | 177 | struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) |
90586523 | 178 | { |
74be0cc8 | 179 | struct fsnotify_group *group; |
90586523 | 180 | |
f0553af0 | 181 | group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL); |
90586523 EP |
182 | if (!group) |
183 | return ERR_PTR(-ENOMEM); | |
184 | ||
36fddeba | 185 | /* set to 0 when there a no external references to this group */ |
90586523 | 186 | atomic_set(&group->refcnt, 1); |
36fddeba EP |
187 | /* |
188 | * hits 0 when there are no external references AND no marks for | |
189 | * this group | |
190 | */ | |
191 | atomic_set(&group->num_marks, 1); | |
192 | ||
a2d8bc6c EP |
193 | mutex_init(&group->notification_mutex); |
194 | INIT_LIST_HEAD(&group->notification_list); | |
195 | init_waitqueue_head(&group->notification_waitq); | |
a2d8bc6c EP |
196 | group->max_events = UINT_MAX; |
197 | ||
4ca76352 | 198 | INIT_LIST_HEAD(&group->inode_group_list); |
7131485a | 199 | INIT_LIST_HEAD(&group->vfsmount_group_list); |
4ca76352 | 200 | |
3be25f49 | 201 | spin_lock_init(&group->mark_lock); |
e61ce867 | 202 | INIT_LIST_HEAD(&group->marks_list); |
3be25f49 | 203 | |
90586523 EP |
204 | group->ops = ops; |
205 | ||
90586523 EP |
206 | return group; |
207 | } |