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c82ee6d3 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
90586523 EP |
2 | /* |
3 | * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> | |
90586523 EP |
4 | */ |
5 | ||
a2d8bc6c EP |
6 | /* |
7 | * Basic idea behind the notification queue: An fsnotify group (like inotify) | |
b3834be5 | 8 | * sends the userspace notification about events asynchronously some time after |
a2d8bc6c EP |
9 | * the event happened. When inotify gets an event it will need to add that |
10 | * event to the group notify queue. Since a single event might need to be on | |
11 | * multiple group's notification queues we can't add the event directly to each | |
12 | * queue and instead add a small "event_holder" to each queue. This event_holder | |
13 | * has a pointer back to the original event. Since the majority of events are | |
14 | * going to end up on one, and only one, notification queue we embed one | |
15 | * event_holder into each event. This means we have a single allocation instead | |
16 | * of always needing two. If the embedded event_holder is already in use by | |
17 | * another group a new event_holder (from fsnotify_event_holder_cachep) will be | |
18 | * allocated and used. | |
19 | */ | |
20 | ||
90586523 EP |
21 | #include <linux/fs.h> |
22 | #include <linux/init.h> | |
23 | #include <linux/kernel.h> | |
24 | #include <linux/list.h> | |
47882c6f | 25 | #include <linux/module.h> |
90586523 EP |
26 | #include <linux/mount.h> |
27 | #include <linux/mutex.h> | |
28 | #include <linux/namei.h> | |
29 | #include <linux/path.h> | |
30 | #include <linux/slab.h> | |
31 | #include <linux/spinlock.h> | |
32 | ||
60063497 | 33 | #include <linux/atomic.h> |
90586523 EP |
34 | |
35 | #include <linux/fsnotify_backend.h> | |
36 | #include "fsnotify.h" | |
37 | ||
47882c6f EP |
38 | static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0); |
39 | ||
40 | /** | |
41 | * fsnotify_get_cookie - return a unique cookie for use in synchronizing events. | |
42 | * Called from fsnotify_move, which is inlined into filesystem modules. | |
43 | */ | |
44 | u32 fsnotify_get_cookie(void) | |
45 | { | |
46 | return atomic_inc_return(&fsnotify_sync_cookie); | |
47 | } | |
48 | EXPORT_SYMBOL_GPL(fsnotify_get_cookie); | |
a2d8bc6c EP |
49 | |
50 | /* return true if the notify queue is empty, false otherwise */ | |
51 | bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group) | |
52 | { | |
ed272640 | 53 | assert_spin_locked(&group->notification_lock); |
a2d8bc6c EP |
54 | return list_empty(&group->notification_list) ? true : false; |
55 | } | |
90586523 | 56 | |
7053aee2 JK |
57 | void fsnotify_destroy_event(struct fsnotify_group *group, |
58 | struct fsnotify_event *event) | |
90586523 | 59 | { |
7053aee2 | 60 | /* Overflow events are per-group and we don't want to free them */ |
a0a92d26 | 61 | if (!event || event == group->overflow_event) |
90586523 | 62 | return; |
0b1b8652 JK |
63 | /* |
64 | * If the event is still queued, we have a problem... Do an unreliable | |
65 | * lockless check first to avoid locking in the common case. The | |
66 | * locking may be necessary for permission events which got removed | |
67 | * from the list by a different CPU than the one freeing the event. | |
68 | */ | |
69 | if (!list_empty(&event->list)) { | |
70 | spin_lock(&group->notification_lock); | |
71 | WARN_ON(!list_empty(&event->list)); | |
72 | spin_unlock(&group->notification_lock); | |
73 | } | |
7053aee2 | 74 | group->ops->free_event(event); |
e4aff117 EP |
75 | } |
76 | ||
90586523 | 77 | /* |
a2d8bc6c | 78 | * Add an event to the group notification queue. The group can later pull this |
83c0e1b4 | 79 | * event off the queue to deal with. The function returns 0 if the event was |
482ef06c | 80 | * added to the queue, 1 if the event was merged with some other queued event, |
12703dbf JK |
81 | * 2 if the event was not queued - either the queue of events has overflown |
82 | * or the group is shutting down. | |
90586523 | 83 | */ |
8ba8fa91 JK |
84 | int fsnotify_add_event(struct fsnotify_group *group, |
85 | struct fsnotify_event *event, | |
86 | int (*merge)(struct list_head *, | |
87 | struct fsnotify_event *)) | |
a2d8bc6c | 88 | { |
83c0e1b4 | 89 | int ret = 0; |
a2d8bc6c | 90 | struct list_head *list = &group->notification_list; |
e4aff117 | 91 | |
7053aee2 | 92 | pr_debug("%s: group=%p event=%p\n", __func__, group, event); |
a2d8bc6c | 93 | |
c21dbe20 | 94 | spin_lock(&group->notification_lock); |
a2d8bc6c | 95 | |
12703dbf | 96 | if (group->shutdown) { |
c21dbe20 | 97 | spin_unlock(&group->notification_lock); |
12703dbf JK |
98 | return 2; |
99 | } | |
100 | ||
7b1f6417 JK |
101 | if (event == group->overflow_event || |
102 | group->q_len >= group->max_events) { | |
482ef06c | 103 | ret = 2; |
7053aee2 | 104 | /* Queue overflow event only if it isn't already queued */ |
ff57cd58 | 105 | if (!list_empty(&group->overflow_event->list)) { |
c21dbe20 | 106 | spin_unlock(&group->notification_lock); |
482ef06c JK |
107 | return ret; |
108 | } | |
ff57cd58 | 109 | event = group->overflow_event; |
482ef06c | 110 | goto queue; |
e4aff117 | 111 | } |
a2d8bc6c | 112 | |
74766bbf | 113 | if (!list_empty(list) && merge) { |
83c0e1b4 JK |
114 | ret = merge(list, event); |
115 | if (ret) { | |
c21dbe20 | 116 | spin_unlock(&group->notification_lock); |
83c0e1b4 | 117 | return ret; |
f70ab54c | 118 | } |
a2d8bc6c EP |
119 | } |
120 | ||
482ef06c | 121 | queue: |
a2d8bc6c | 122 | group->q_len++; |
7053aee2 | 123 | list_add_tail(&event->list, list); |
c21dbe20 | 124 | spin_unlock(&group->notification_lock); |
a2d8bc6c EP |
125 | |
126 | wake_up(&group->notification_waitq); | |
0a6b6bd5 | 127 | kill_fasync(&group->fsn_fa, SIGIO, POLL_IN); |
83c0e1b4 | 128 | return ret; |
a2d8bc6c EP |
129 | } |
130 | ||
f7db89ac JK |
131 | void fsnotify_remove_queued_event(struct fsnotify_group *group, |
132 | struct fsnotify_event *event) | |
133 | { | |
134 | assert_spin_locked(&group->notification_lock); | |
135 | /* | |
136 | * We need to init list head for the case of overflow event so that | |
137 | * check in fsnotify_add_event() works | |
138 | */ | |
139 | list_del_init(&event->list); | |
140 | group->q_len--; | |
141 | } | |
142 | ||
a2d8bc6c | 143 | /* |
7053aee2 JK |
144 | * Remove and return the first event from the notification list. It is the |
145 | * responsibility of the caller to destroy the obtained event | |
a2d8bc6c | 146 | */ |
8ba8fa91 | 147 | struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group) |
90586523 EP |
148 | { |
149 | struct fsnotify_event *event; | |
150 | ||
ed272640 | 151 | assert_spin_locked(&group->notification_lock); |
90586523 | 152 | |
5ba08e2e EP |
153 | pr_debug("%s: group=%p\n", __func__, group); |
154 | ||
7053aee2 JK |
155 | event = list_first_entry(&group->notification_list, |
156 | struct fsnotify_event, list); | |
f7db89ac | 157 | fsnotify_remove_queued_event(group, event); |
a2d8bc6c EP |
158 | return event; |
159 | } | |
160 | ||
161 | /* | |
8ba8fa91 JK |
162 | * This will not remove the event, that must be done with |
163 | * fsnotify_remove_first_event() | |
a2d8bc6c | 164 | */ |
8ba8fa91 | 165 | struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group) |
a2d8bc6c | 166 | { |
ed272640 | 167 | assert_spin_locked(&group->notification_lock); |
a2d8bc6c | 168 | |
7053aee2 JK |
169 | return list_first_entry(&group->notification_list, |
170 | struct fsnotify_event, list); | |
a2d8bc6c EP |
171 | } |
172 | ||
173 | /* | |
174 | * Called when a group is being torn down to clean up any outstanding | |
175 | * event notifications. | |
176 | */ | |
177 | void fsnotify_flush_notify(struct fsnotify_group *group) | |
178 | { | |
179 | struct fsnotify_event *event; | |
180 | ||
c21dbe20 | 181 | spin_lock(&group->notification_lock); |
a2d8bc6c | 182 | while (!fsnotify_notify_queue_is_empty(group)) { |
8ba8fa91 | 183 | event = fsnotify_remove_first_event(group); |
c21dbe20 | 184 | spin_unlock(&group->notification_lock); |
7053aee2 | 185 | fsnotify_destroy_event(group, event); |
c21dbe20 | 186 | spin_lock(&group->notification_lock); |
a2d8bc6c | 187 | } |
c21dbe20 | 188 | spin_unlock(&group->notification_lock); |
a2d8bc6c | 189 | } |