summaryrefslogtreecommitdiffstats
path: root/fs/notify/group.c
blob: 6a297efc478874b10346b1d8ac0e8a9c941d6bd3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
 */

#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/srcu.h>
#include <linux/rculist.h>
#include <linux/wait.h>
#include <linux/memcontrol.h>

#include <linux/fsnotify_backend.h>
#include "fsnotify.h"

#include <linux/atomic.h>

/*
 * Final freeing of a group
 */
static void fsnotify_final_destroy_group(struct fsnotify_group *group)
{
	if (group->ops->free_group_priv)
		group->ops->free_group_priv(group);

	mem_cgroup_put(group->memcg);
	mutex_destroy(&group->mark_mutex);

	kfree(group);
}

/*
 * Stop queueing new events for this group. Once this function returns
 * fsnotify_add_event() will not add any new events to the group's queue.
 */
void fsnotify_group_stop_queueing(struct fsnotify_group *group)
{
	spin_lock(&group->notification_lock);
	group->shutdown = true;
	spin_unlock(&group->notification_lock);
}

/*
 * Trying to get rid of a group. Remove all marks, flush all events and release
 * the group reference.
 * Note that another thread calling fsnotify_clear_marks_by_group() may still
 * hold a ref to the group.
 */
void fsnotify_destroy_group(struct fsnotify_group *group)
{
	/*
	 * Stop queueing new events. The code below is careful enough to not
	 * require this but fanotify needs to stop queuing events even before
	 * fsnotify_destroy_group() is called and this makes the other callers
	 * of fsnotify_destroy_group() to see the same behavior.
	 */
	fsnotify_group_stop_queueing(group);

	/* Clear all marks for this group and queue them for destruction */
	fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_ALL_TYPES_MASK);

	/*
	 * Some marks can still be pinned when waiting for response from
	 * userspace. Wait for those now. fsnotify_prepare_user_wait() will
	 * not succeed now so this wait is race-free.
	 */
	wait_event(group->notification_waitq, !atomic_read(&group->user_waits));

	/*
	 * Wait until all marks get really destroyed. We could actually destroy
	 * them ourselves instead of waiting for worker to do it, however that
	 * would be racy as worker can already be processing some marks before
	 * we even entered fsnotify_destroy_group().
	 */
	fsnotify_wait_marks_destroyed();

	/*
	 * Since we have waited for fsnotify_mark_srcu in
	 * fsnotify_mark_destroy_list() there can be no outstanding event
	 * notification against this group. So clearing the notification queue
	 * of all events is reliable now.
	 */
	fsnotify_flush_notify(group);

	/*
	 * Destroy overflow event (we cannot use fsnotify_destroy_event() as
	 * that deliberately ignores overflow events.
	 */
	if (group->overflow_event)
		group->ops->free_event(group, group->overflow_event);

	fsnotify_put_group(group);
}

/*
 * Get reference to a group.
 */
void fsnotify_get_group(struct fsnotify_group *group)
{
	refcount_inc(&group->refcnt);
}

/*
 * Drop a reference to a group.  Free it if it's through.
 */
void fsnotify_put_group(struct fsnotify_group *group)
{
	if (refcount_dec_and_test(&group->refcnt))
		fsnotify_final_destroy_group(group);
}
EXPORT_SYMBOL_GPL(fsnotify_put_group);

static struct fsnotify_group *__fsnotify_alloc_group(
				const struct fsnotify_ops *ops, gfp_t gfp)
{
	struct fsnotify_group *group;

	group = kzalloc(sizeof(struct fsnotify_group), gfp);
	if (!group)
		return ERR_PTR(-ENOMEM);

	/* set to 0 when there a no external references to this group */
	refcount_set(&group->refcnt, 1);
	atomic_set(&group->user_waits, 0);

	spin_lock_init(&group->notification_lock);
	INIT_LIST_HEAD(&group->notification_list);
	init_waitqueue_head(&group->notification_waitq);
	group->max_events = UINT_MAX;

	mutex_init(&group->mark_mutex);
	INIT_LIST_HEAD(&group->marks_list);

	group->ops = ops;

	return group;
}

/*
 * Create a new fsnotify_group and hold a reference for the group returned.
 */
struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
{
	return __fsnotify_alloc_group(ops, GFP_KERNEL);
}
EXPORT_SYMBOL_GPL(fsnotify_alloc_group);

/*
 * Create a new fsnotify_group and hold a reference for the group returned.
 */
struct fsnotify_group *fsnotify_alloc_user_group(const struct fsnotify_ops *ops)
{
	return __fsnotify_alloc_group(ops, GFP_KERNEL_ACCOUNT);
}
EXPORT_SYMBOL_GPL(fsnotify_alloc_user_group);

int fsnotify_fasync(int fd, struct file *file, int on)
{
	struct fsnotify_group *group = file->private_data;

	return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
}