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 #include <linux/memcontrol.h>
26
27 #include <linux/fsnotify_backend.h>
28 #include "fsnotify.h"
29
30 #include <linux/atomic.h>
31
32 /*
33 * Final freeing of a group
34 */
fsnotify_final_destroy_group(struct fsnotify_group * group)35 static void fsnotify_final_destroy_group(struct fsnotify_group *group)
36 {
37 if (group->ops->free_group_priv)
38 group->ops->free_group_priv(group);
39
40 mem_cgroup_put(group->memcg);
41
42 kfree(group);
43 }
44
45 /*
46 * Stop queueing new events for this group. Once this function returns
47 * fsnotify_add_event() will not add any new events to the group's queue.
48 */
fsnotify_group_stop_queueing(struct fsnotify_group * group)49 void fsnotify_group_stop_queueing(struct fsnotify_group *group)
50 {
51 spin_lock(&group->notification_lock);
52 group->shutdown = true;
53 spin_unlock(&group->notification_lock);
54 }
55
56 /*
57 * Trying to get rid of a group. Remove all marks, flush all events and release
58 * the group reference.
59 * Note that another thread calling fsnotify_clear_marks_by_group() may still
60 * hold a ref to the group.
61 */
fsnotify_destroy_group(struct fsnotify_group * group)62 void fsnotify_destroy_group(struct fsnotify_group *group)
63 {
64 /*
65 * Stop queueing new events. The code below is careful enough to not
66 * require this but fanotify needs to stop queuing events even before
67 * fsnotify_destroy_group() is called and this makes the other callers
68 * of fsnotify_destroy_group() to see the same behavior.
69 */
70 fsnotify_group_stop_queueing(group);
71
72 /* Clear all marks for this group and queue them for destruction */
73 fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_ALL_TYPES_MASK);
74
75 /*
76 * Some marks can still be pinned when waiting for response from
77 * userspace. Wait for those now. fsnotify_prepare_user_wait() will
78 * not succeed now so this wait is race-free.
79 */
80 wait_event(group->notification_waitq, !atomic_read(&group->user_waits));
81
82 /*
83 * Wait until all marks get really destroyed. We could actually destroy
84 * them ourselves instead of waiting for worker to do it, however that
85 * would be racy as worker can already be processing some marks before
86 * we even entered fsnotify_destroy_group().
87 */
88 fsnotify_wait_marks_destroyed();
89
90 /*
91 * Since we have waited for fsnotify_mark_srcu in
92 * fsnotify_mark_destroy_list() there can be no outstanding event
93 * notification against this group. So clearing the notification queue
94 * of all events is reliable now.
95 */
96 fsnotify_flush_notify(group);
97
98 /*
99 * Destroy overflow event (we cannot use fsnotify_destroy_event() as
100 * that deliberately ignores overflow events.
101 */
102 if (group->overflow_event)
103 group->ops->free_event(group->overflow_event);
104
105 fsnotify_put_group(group);
106 }
107
108 /*
109 * Get reference to a group.
110 */
fsnotify_get_group(struct fsnotify_group * group)111 void fsnotify_get_group(struct fsnotify_group *group)
112 {
113 refcount_inc(&group->refcnt);
114 }
115
116 /*
117 * Drop a reference to a group. Free it if it's through.
118 */
fsnotify_put_group(struct fsnotify_group * group)119 void fsnotify_put_group(struct fsnotify_group *group)
120 {
121 if (refcount_dec_and_test(&group->refcnt))
122 fsnotify_final_destroy_group(group);
123 }
124
125 /*
126 * Create a new fsnotify_group and hold a reference for the group returned.
127 */
fsnotify_alloc_group(const struct fsnotify_ops * ops)128 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
129 {
130 struct fsnotify_group *group;
131
132 group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
133 if (!group)
134 return ERR_PTR(-ENOMEM);
135
136 /* set to 0 when there a no external references to this group */
137 refcount_set(&group->refcnt, 1);
138 atomic_set(&group->num_marks, 0);
139 atomic_set(&group->user_waits, 0);
140
141 spin_lock_init(&group->notification_lock);
142 INIT_LIST_HEAD(&group->notification_list);
143 init_waitqueue_head(&group->notification_waitq);
144 group->max_events = UINT_MAX;
145
146 mutex_init(&group->mark_mutex);
147 INIT_LIST_HEAD(&group->marks_list);
148
149 group->ops = ops;
150
151 return group;
152 }
153
fsnotify_fasync(int fd,struct file * file,int on)154 int fsnotify_fasync(int fd, struct file *file, int on)
155 {
156 struct fsnotify_group *group = file->private_data;
157
158 return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
159 }
160