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 <linux/atomic.h>
30
31/*
32 * Final freeing of a group
33 */
34static void fsnotify_final_destroy_group(struct fsnotify_group *group)
35{
36	if (group->ops->free_group_priv)
37		group->ops->free_group_priv(group);
38
39	kfree(group);
40}
41
42/*
43 * Trying to get rid of a group. Remove all marks, flush all events and release
44 * the group reference.
45 * Note that another thread calling fsnotify_clear_marks_by_group() may still
46 * hold a ref to the group.
47 */
48void fsnotify_destroy_group(struct fsnotify_group *group)
49{
50	/* clear all inode marks for this group */
51	fsnotify_clear_marks_by_group(group);
52
53	synchronize_srcu(&fsnotify_mark_srcu);
54
55	/* clear the notification queue of all events */
56	fsnotify_flush_notify(group);
57
58	/*
59	 * Destroy overflow event (we cannot use fsnotify_destroy_event() as
60	 * that deliberately ignores overflow events.
61	 */
62	if (group->overflow_event)
63		group->ops->free_event(group->overflow_event);
64
65	fsnotify_put_group(group);
66}
67
68/*
69 * Get reference to a group.
70 */
71void fsnotify_get_group(struct fsnotify_group *group)
72{
73	atomic_inc(&group->refcnt);
74}
75
76/*
77 * Drop a reference to a group.  Free it if it's through.
78 */
79void fsnotify_put_group(struct fsnotify_group *group)
80{
81	if (atomic_dec_and_test(&group->refcnt))
82		fsnotify_final_destroy_group(group);
83}
84
85/*
86 * Create a new fsnotify_group and hold a reference for the group returned.
87 */
88struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
89{
90	struct fsnotify_group *group;
91
92	group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
93	if (!group)
94		return ERR_PTR(-ENOMEM);
95
96	/* set to 0 when there a no external references to this group */
97	atomic_set(&group->refcnt, 1);
98	atomic_set(&group->num_marks, 0);
99
100	mutex_init(&group->notification_mutex);
101	INIT_LIST_HEAD(&group->notification_list);
102	init_waitqueue_head(&group->notification_waitq);
103	group->max_events = UINT_MAX;
104
105	mutex_init(&group->mark_mutex);
106	INIT_LIST_HEAD(&group->marks_list);
107
108	group->ops = ops;
109
110	return group;
111}
112
113int fsnotify_fasync(int fd, struct file *file, int on)
114{
115	struct fsnotify_group *group = file->private_data;
116
117	return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
118}
119