xref: /linux/fs/notify/group.c (revision d91517839e5d95adc0cf4b28caa7af62a71de526)
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  */
34 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  */
48 void 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 	fsnotify_put_group(group);
59 }
60 
61 /*
62  * Get reference to a group.
63  */
64 void fsnotify_get_group(struct fsnotify_group *group)
65 {
66 	atomic_inc(&group->refcnt);
67 }
68 
69 /*
70  * Drop a reference to a group.  Free it if it's through.
71  */
72 void fsnotify_put_group(struct fsnotify_group *group)
73 {
74 	if (atomic_dec_and_test(&group->refcnt))
75 		fsnotify_final_destroy_group(group);
76 }
77 
78 /*
79  * Create a new fsnotify_group and hold a reference for the group returned.
80  */
81 struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
82 {
83 	struct fsnotify_group *group;
84 
85 	group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
86 	if (!group)
87 		return ERR_PTR(-ENOMEM);
88 
89 	/* set to 0 when there a no external references to this group */
90 	atomic_set(&group->refcnt, 1);
91 	atomic_set(&group->num_marks, 0);
92 
93 	mutex_init(&group->notification_mutex);
94 	INIT_LIST_HEAD(&group->notification_list);
95 	init_waitqueue_head(&group->notification_waitq);
96 	group->max_events = UINT_MAX;
97 
98 	mutex_init(&group->mark_mutex);
99 	INIT_LIST_HEAD(&group->marks_list);
100 
101 	group->ops = ops;
102 	fsnotify_init_event(&group->overflow_event, NULL, FS_Q_OVERFLOW);
103 
104 	return group;
105 }
106 
107 int fsnotify_fasync(int fd, struct file *file, int on)
108 {
109 	struct fsnotify_group *group = file->private_data;
110 
111 	return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
112 }
113