1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
4 */
5
6#include <linux/list.h>
7#include <linux/mutex.h>
8#include <linux/slab.h>
9#include <linux/srcu.h>
10#include <linux/rculist.h>
11#include <linux/wait.h>
12#include <linux/memcontrol.h>
13
14#include <linux/fsnotify_backend.h>
15#include "fsnotify.h"
16
17#include <linux/atomic.h>
18
19/*
20 * Final freeing of a group
21 */
22static void fsnotify_final_destroy_group(struct fsnotify_group *group)
23{
24 if (group->ops->free_group_priv)
25 group->ops->free_group_priv(group);
26
27 mem_cgroup_put(memcg: group->memcg);
28 mutex_destroy(lock: &group->mark_mutex);
29
30 kfree(objp: group);
31}
32
33/*
34 * Stop queueing new events for this group. Once this function returns
35 * fsnotify_add_event() will not add any new events to the group's queue.
36 */
37void fsnotify_group_stop_queueing(struct fsnotify_group *group)
38{
39 spin_lock(lock: &group->notification_lock);
40 group->shutdown = true;
41 spin_unlock(lock: &group->notification_lock);
42}
43
44/*
45 * Trying to get rid of a group. Remove all marks, flush all events and release
46 * the group reference.
47 * Note that another thread calling fsnotify_clear_marks_by_group() may still
48 * hold a ref to the group.
49 */
50void fsnotify_destroy_group(struct fsnotify_group *group)
51{
52 /*
53 * Stop queueing new events. The code below is careful enough to not
54 * require this but fanotify needs to stop queuing events even before
55 * fsnotify_destroy_group() is called and this makes the other callers
56 * of fsnotify_destroy_group() to see the same behavior.
57 */
58 fsnotify_group_stop_queueing(group);
59
60 /* Clear all marks for this group and queue them for destruction */
61 fsnotify_clear_marks_by_group(group, obj_type: FSNOTIFY_OBJ_TYPE_ANY);
62
63 /*
64 * Some marks can still be pinned when waiting for response from
65 * userspace. Wait for those now. fsnotify_prepare_user_wait() will
66 * not succeed now so this wait is race-free.
67 */
68 wait_event(group->notification_waitq, !atomic_read(&group->user_waits));
69
70 /*
71 * Wait until all marks get really destroyed. We could actually destroy
72 * them ourselves instead of waiting for worker to do it, however that
73 * would be racy as worker can already be processing some marks before
74 * we even entered fsnotify_destroy_group().
75 */
76 fsnotify_wait_marks_destroyed();
77
78 /*
79 * Since we have waited for fsnotify_mark_srcu in
80 * fsnotify_mark_destroy_list() there can be no outstanding event
81 * notification against this group. So clearing the notification queue
82 * of all events is reliable now.
83 */
84 fsnotify_flush_notify(group);
85
86 /*
87 * Destroy overflow event (we cannot use fsnotify_destroy_event() as
88 * that deliberately ignores overflow events.
89 */
90 if (group->overflow_event)
91 group->ops->free_event(group, group->overflow_event);
92
93 fsnotify_put_group(group);
94}
95
96/*
97 * Get reference to a group.
98 */
99void fsnotify_get_group(struct fsnotify_group *group)
100{
101 refcount_inc(r: &group->refcnt);
102}
103
104/*
105 * Drop a reference to a group. Free it if it's through.
106 */
107void fsnotify_put_group(struct fsnotify_group *group)
108{
109 if (refcount_dec_and_test(r: &group->refcnt))
110 fsnotify_final_destroy_group(group);
111}
112EXPORT_SYMBOL_GPL(fsnotify_put_group);
113
114static struct fsnotify_group *__fsnotify_alloc_group(
115 const struct fsnotify_ops *ops,
116 int flags, gfp_t gfp)
117{
118 struct fsnotify_group *group;
119
120 group = kzalloc(sizeof(struct fsnotify_group), gfp);
121 if (!group)
122 return ERR_PTR(error: -ENOMEM);
123
124 /* set to 0 when there a no external references to this group */
125 refcount_set(r: &group->refcnt, n: 1);
126 atomic_set(v: &group->user_waits, i: 0);
127
128 spin_lock_init(&group->notification_lock);
129 INIT_LIST_HEAD(list: &group->notification_list);
130 init_waitqueue_head(&group->notification_waitq);
131 group->max_events = UINT_MAX;
132
133 mutex_init(&group->mark_mutex);
134 INIT_LIST_HEAD(list: &group->marks_list);
135
136 group->ops = ops;
137 group->flags = flags;
138
139 return group;
140}
141
142/*
143 * Create a new fsnotify_group and hold a reference for the group returned.
144 */
145struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops,
146 int flags)
147{
148 gfp_t gfp = (flags & FSNOTIFY_GROUP_USER) ? GFP_KERNEL_ACCOUNT :
149 GFP_KERNEL;
150
151 return __fsnotify_alloc_group(ops, flags, gfp);
152}
153EXPORT_SYMBOL_GPL(fsnotify_alloc_group);
154
155int fsnotify_fasync(int fd, struct file *file, int on)
156{
157 struct fsnotify_group *group = file->private_data;
158
159 return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
160}
161