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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 | 49 | |
7053aee2 JK |
50 | void fsnotify_destroy_event(struct fsnotify_group *group, |
51 | struct fsnotify_event *event) | |
90586523 | 52 | { |
7053aee2 | 53 | /* Overflow events are per-group and we don't want to free them */ |
a0a92d26 | 54 | if (!event || event == group->overflow_event) |
90586523 | 55 | return; |
0b1b8652 JK |
56 | /* |
57 | * If the event is still queued, we have a problem... Do an unreliable | |
58 | * lockless check first to avoid locking in the common case. The | |
59 | * locking may be necessary for permission events which got removed | |
60 | * from the list by a different CPU than the one freeing the event. | |
61 | */ | |
62 | if (!list_empty(&event->list)) { | |
63 | spin_lock(&group->notification_lock); | |
64 | WARN_ON(!list_empty(&event->list)); | |
65 | spin_unlock(&group->notification_lock); | |
66 | } | |
330ae77d | 67 | group->ops->free_event(group, event); |
e4aff117 EP |
68 | } |
69 | ||
90586523 | 70 | /* |
94e00d28 AG |
71 | * Try to add an event to the notification queue. |
72 | * The group can later pull this event off the queue to deal with. | |
73 | * The group can use the @merge hook to merge the event with a queued event. | |
74 | * The group can use the @insert hook to insert the event into hash table. | |
75 | * The function returns: | |
76 | * 0 if the event was added to a queue | |
77 | * 1 if the event was merged with some other queued event | |
12703dbf | 78 | * 2 if the event was not queued - either the queue of events has overflown |
94e00d28 | 79 | * or the group is shutting down. |
90586523 | 80 | */ |
1ad03c3a GKB |
81 | int fsnotify_insert_event(struct fsnotify_group *group, |
82 | struct fsnotify_event *event, | |
83 | int (*merge)(struct fsnotify_group *, | |
84 | struct fsnotify_event *), | |
85 | void (*insert)(struct fsnotify_group *, | |
86 | struct fsnotify_event *)) | |
a2d8bc6c | 87 | { |
83c0e1b4 | 88 | int ret = 0; |
a2d8bc6c | 89 | struct list_head *list = &group->notification_list; |
e4aff117 | 90 | |
7053aee2 | 91 | pr_debug("%s: group=%p event=%p\n", __func__, group, event); |
a2d8bc6c | 92 | |
c21dbe20 | 93 | spin_lock(&group->notification_lock); |
a2d8bc6c | 94 | |
12703dbf | 95 | if (group->shutdown) { |
c21dbe20 | 96 | spin_unlock(&group->notification_lock); |
12703dbf JK |
97 | return 2; |
98 | } | |
99 | ||
7b1f6417 JK |
100 | if (event == group->overflow_event || |
101 | group->q_len >= group->max_events) { | |
482ef06c | 102 | ret = 2; |
7053aee2 | 103 | /* Queue overflow event only if it isn't already queued */ |
ff57cd58 | 104 | if (!list_empty(&group->overflow_event->list)) { |
c21dbe20 | 105 | spin_unlock(&group->notification_lock); |
482ef06c JK |
106 | return ret; |
107 | } | |
ff57cd58 | 108 | event = group->overflow_event; |
482ef06c | 109 | goto queue; |
e4aff117 | 110 | } |
a2d8bc6c | 111 | |
74766bbf | 112 | if (!list_empty(list) && merge) { |
94e00d28 | 113 | ret = merge(group, event); |
83c0e1b4 | 114 | if (ret) { |
c21dbe20 | 115 | spin_unlock(&group->notification_lock); |
83c0e1b4 | 116 | return ret; |
f70ab54c | 117 | } |
a2d8bc6c EP |
118 | } |
119 | ||
482ef06c | 120 | queue: |
a2d8bc6c | 121 | group->q_len++; |
7053aee2 | 122 | list_add_tail(&event->list, list); |
94e00d28 AG |
123 | if (insert) |
124 | insert(group, event); | |
c21dbe20 | 125 | spin_unlock(&group->notification_lock); |
a2d8bc6c EP |
126 | |
127 | wake_up(&group->notification_waitq); | |
0a6b6bd5 | 128 | kill_fasync(&group->fsn_fa, SIGIO, POLL_IN); |
83c0e1b4 | 129 | return ret; |
a2d8bc6c EP |
130 | } |
131 | ||
f7db89ac JK |
132 | void fsnotify_remove_queued_event(struct fsnotify_group *group, |
133 | struct fsnotify_event *event) | |
134 | { | |
135 | assert_spin_locked(&group->notification_lock); | |
136 | /* | |
137 | * We need to init list head for the case of overflow event so that | |
138 | * check in fsnotify_add_event() works | |
139 | */ | |
140 | list_del_init(&event->list); | |
141 | group->q_len--; | |
142 | } | |
143 | ||
a2d8bc6c | 144 | /* |
6f73171e AG |
145 | * Return the first event on the notification list without removing it. |
146 | * Returns NULL if the list is empty. | |
a2d8bc6c | 147 | */ |
6f73171e | 148 | struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group) |
90586523 | 149 | { |
ed272640 | 150 | assert_spin_locked(&group->notification_lock); |
90586523 | 151 | |
6f73171e AG |
152 | if (fsnotify_notify_queue_is_empty(group)) |
153 | return NULL; | |
5ba08e2e | 154 | |
6f73171e AG |
155 | return list_first_entry(&group->notification_list, |
156 | struct fsnotify_event, list); | |
a2d8bc6c EP |
157 | } |
158 | ||
159 | /* | |
6f73171e AG |
160 | * Remove and return the first event from the notification list. It is the |
161 | * responsibility of the caller to destroy the obtained event | |
a2d8bc6c | 162 | */ |
6f73171e | 163 | struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group) |
a2d8bc6c | 164 | { |
6f73171e | 165 | struct fsnotify_event *event = fsnotify_peek_first_event(group); |
a2d8bc6c | 166 | |
6f73171e AG |
167 | if (!event) |
168 | return NULL; | |
169 | ||
170 | pr_debug("%s: group=%p event=%p\n", __func__, group, event); | |
171 | ||
172 | fsnotify_remove_queued_event(group, event); | |
173 | ||
174 | return event; | |
a2d8bc6c EP |
175 | } |
176 | ||
177 | /* | |
178 | * Called when a group is being torn down to clean up any outstanding | |
179 | * event notifications. | |
180 | */ | |
181 | void fsnotify_flush_notify(struct fsnotify_group *group) | |
182 | { | |
183 | struct fsnotify_event *event; | |
184 | ||
c21dbe20 | 185 | spin_lock(&group->notification_lock); |
a2d8bc6c | 186 | while (!fsnotify_notify_queue_is_empty(group)) { |
8ba8fa91 | 187 | event = fsnotify_remove_first_event(group); |
c21dbe20 | 188 | spin_unlock(&group->notification_lock); |
7053aee2 | 189 | fsnotify_destroy_event(group, event); |
c21dbe20 | 190 | spin_lock(&group->notification_lock); |
a2d8bc6c | 191 | } |
c21dbe20 | 192 | spin_unlock(&group->notification_lock); |
a2d8bc6c | 193 | } |