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 | */ |
22 | static 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 | */ |
37 | void 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 | */ |
50 | void 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 | */ |
99 | void 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 | */ |
107 | void fsnotify_put_group(struct fsnotify_group *group) |
108 | { |
109 | if (refcount_dec_and_test(r: &group->refcnt)) |
110 | fsnotify_final_destroy_group(group); |
111 | } |
112 | EXPORT_SYMBOL_GPL(fsnotify_put_group); |
113 | |
114 | static struct fsnotify_group *__fsnotify_alloc_group( |
115 | const struct fsnotify_ops *ops, |
116 | int flags, gfp_t gfp) |
117 | { |
118 | static struct lock_class_key nofs_marks_lock; |
119 | struct fsnotify_group *group; |
120 | |
121 | group = kzalloc(size: sizeof(struct fsnotify_group), flags: gfp); |
122 | if (!group) |
123 | return ERR_PTR(error: -ENOMEM); |
124 | |
125 | /* set to 0 when there a no external references to this group */ |
126 | refcount_set(r: &group->refcnt, n: 1); |
127 | atomic_set(v: &group->user_waits, i: 0); |
128 | |
129 | spin_lock_init(&group->notification_lock); |
130 | INIT_LIST_HEAD(list: &group->notification_list); |
131 | init_waitqueue_head(&group->notification_waitq); |
132 | group->max_events = UINT_MAX; |
133 | |
134 | mutex_init(&group->mark_mutex); |
135 | INIT_LIST_HEAD(list: &group->marks_list); |
136 | |
137 | group->ops = ops; |
138 | group->flags = flags; |
139 | /* |
140 | * For most backends, eviction of inode with a mark is not expected, |
141 | * because marks hold a refcount on the inode against eviction. |
142 | * |
143 | * Use a different lockdep class for groups that support evictable |
144 | * inode marks, because with evictable marks, mark_mutex is NOT |
145 | * fs-reclaim safe - the mutex is taken when evicting inodes. |
146 | */ |
147 | if (flags & FSNOTIFY_GROUP_NOFS) |
148 | lockdep_set_class(&group->mark_mutex, &nofs_marks_lock); |
149 | |
150 | return group; |
151 | } |
152 | |
153 | /* |
154 | * Create a new fsnotify_group and hold a reference for the group returned. |
155 | */ |
156 | struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops, |
157 | int flags) |
158 | { |
159 | gfp_t gfp = (flags & FSNOTIFY_GROUP_USER) ? GFP_KERNEL_ACCOUNT : |
160 | GFP_KERNEL; |
161 | |
162 | return __fsnotify_alloc_group(ops, flags, gfp); |
163 | } |
164 | EXPORT_SYMBOL_GPL(fsnotify_alloc_group); |
165 | |
166 | int fsnotify_fasync(int fd, struct file *file, int on) |
167 | { |
168 | struct fsnotify_group *group = file->private_data; |
169 | |
170 | return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO; |
171 | } |
172 | |