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90586523 EP |
1 | /* |
2 | * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com> | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2, or (at your option) | |
7 | * any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; see the file COPYING. If not, write to | |
16 | * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. | |
17 | */ | |
18 | ||
a2d8bc6c EP |
19 | /* |
20 | * Basic idea behind the notification queue: An fsnotify group (like inotify) | |
b3834be5 | 21 | * sends the userspace notification about events asynchronously some time after |
a2d8bc6c EP |
22 | * the event happened. When inotify gets an event it will need to add that |
23 | * event to the group notify queue. Since a single event might need to be on | |
24 | * multiple group's notification queues we can't add the event directly to each | |
25 | * queue and instead add a small "event_holder" to each queue. This event_holder | |
26 | * has a pointer back to the original event. Since the majority of events are | |
27 | * going to end up on one, and only one, notification queue we embed one | |
28 | * event_holder into each event. This means we have a single allocation instead | |
29 | * of always needing two. If the embedded event_holder is already in use by | |
30 | * another group a new event_holder (from fsnotify_event_holder_cachep) will be | |
31 | * allocated and used. | |
32 | */ | |
33 | ||
90586523 EP |
34 | #include <linux/fs.h> |
35 | #include <linux/init.h> | |
36 | #include <linux/kernel.h> | |
37 | #include <linux/list.h> | |
47882c6f | 38 | #include <linux/module.h> |
90586523 EP |
39 | #include <linux/mount.h> |
40 | #include <linux/mutex.h> | |
41 | #include <linux/namei.h> | |
42 | #include <linux/path.h> | |
43 | #include <linux/slab.h> | |
44 | #include <linux/spinlock.h> | |
45 | ||
60063497 | 46 | #include <linux/atomic.h> |
90586523 EP |
47 | |
48 | #include <linux/fsnotify_backend.h> | |
49 | #include "fsnotify.h" | |
50 | ||
47882c6f EP |
51 | static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0); |
52 | ||
53 | /** | |
54 | * fsnotify_get_cookie - return a unique cookie for use in synchronizing events. | |
55 | * Called from fsnotify_move, which is inlined into filesystem modules. | |
56 | */ | |
57 | u32 fsnotify_get_cookie(void) | |
58 | { | |
59 | return atomic_inc_return(&fsnotify_sync_cookie); | |
60 | } | |
61 | EXPORT_SYMBOL_GPL(fsnotify_get_cookie); | |
a2d8bc6c EP |
62 | |
63 | /* return true if the notify queue is empty, false otherwise */ | |
64 | bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group) | |
65 | { | |
66 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); | |
67 | return list_empty(&group->notification_list) ? true : false; | |
68 | } | |
90586523 | 69 | |
7053aee2 JK |
70 | void fsnotify_destroy_event(struct fsnotify_group *group, |
71 | struct fsnotify_event *event) | |
90586523 | 72 | { |
7053aee2 JK |
73 | /* Overflow events are per-group and we don't want to free them */ |
74 | if (!event || event->mask == FS_Q_OVERFLOW) | |
90586523 | 75 | return; |
5838d444 JK |
76 | /* If the event is still queued, we have a problem... */ |
77 | WARN_ON(!list_empty(&event->list)); | |
7053aee2 | 78 | group->ops->free_event(event); |
e4aff117 EP |
79 | } |
80 | ||
90586523 | 81 | /* |
a2d8bc6c | 82 | * Add an event to the group notification queue. The group can later pull this |
83c0e1b4 | 83 | * event off the queue to deal with. The function returns 0 if the event was |
482ef06c | 84 | * added to the queue, 1 if the event was merged with some other queued event, |
12703dbf JK |
85 | * 2 if the event was not queued - either the queue of events has overflown |
86 | * or the group is shutting down. | |
90586523 | 87 | */ |
8ba8fa91 JK |
88 | int fsnotify_add_event(struct fsnotify_group *group, |
89 | struct fsnotify_event *event, | |
90 | int (*merge)(struct list_head *, | |
91 | struct fsnotify_event *)) | |
a2d8bc6c | 92 | { |
83c0e1b4 | 93 | int ret = 0; |
a2d8bc6c | 94 | struct list_head *list = &group->notification_list; |
e4aff117 | 95 | |
7053aee2 | 96 | pr_debug("%s: group=%p event=%p\n", __func__, group, event); |
a2d8bc6c EP |
97 | |
98 | mutex_lock(&group->notification_mutex); | |
99 | ||
12703dbf JK |
100 | if (group->shutdown) { |
101 | mutex_unlock(&group->notification_mutex); | |
102 | return 2; | |
103 | } | |
104 | ||
e4aff117 | 105 | if (group->q_len >= group->max_events) { |
482ef06c | 106 | ret = 2; |
7053aee2 | 107 | /* Queue overflow event only if it isn't already queued */ |
ff57cd58 | 108 | if (!list_empty(&group->overflow_event->list)) { |
482ef06c JK |
109 | mutex_unlock(&group->notification_mutex); |
110 | return ret; | |
111 | } | |
ff57cd58 | 112 | event = group->overflow_event; |
482ef06c | 113 | goto queue; |
e4aff117 | 114 | } |
a2d8bc6c | 115 | |
74766bbf | 116 | if (!list_empty(list) && merge) { |
83c0e1b4 JK |
117 | ret = merge(list, event); |
118 | if (ret) { | |
7053aee2 | 119 | mutex_unlock(&group->notification_mutex); |
83c0e1b4 | 120 | return ret; |
f70ab54c | 121 | } |
a2d8bc6c EP |
122 | } |
123 | ||
482ef06c | 124 | queue: |
a2d8bc6c | 125 | group->q_len++; |
7053aee2 | 126 | list_add_tail(&event->list, list); |
a2d8bc6c EP |
127 | mutex_unlock(&group->notification_mutex); |
128 | ||
129 | wake_up(&group->notification_waitq); | |
0a6b6bd5 | 130 | kill_fasync(&group->fsn_fa, SIGIO, POLL_IN); |
83c0e1b4 | 131 | return ret; |
a2d8bc6c EP |
132 | } |
133 | ||
134 | /* | |
7053aee2 JK |
135 | * Remove and return the first event from the notification list. It is the |
136 | * responsibility of the caller to destroy the obtained event | |
a2d8bc6c | 137 | */ |
8ba8fa91 | 138 | struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group) |
90586523 EP |
139 | { |
140 | struct fsnotify_event *event; | |
141 | ||
a2d8bc6c | 142 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); |
90586523 | 143 | |
5ba08e2e EP |
144 | pr_debug("%s: group=%p\n", __func__, group); |
145 | ||
7053aee2 JK |
146 | event = list_first_entry(&group->notification_list, |
147 | struct fsnotify_event, list); | |
2513190a JK |
148 | /* |
149 | * We need to init list head for the case of overflow event so that | |
8ba8fa91 | 150 | * check in fsnotify_add_event() works |
2513190a JK |
151 | */ |
152 | list_del_init(&event->list); | |
a2d8bc6c EP |
153 | group->q_len--; |
154 | ||
155 | return event; | |
156 | } | |
157 | ||
158 | /* | |
8ba8fa91 JK |
159 | * This will not remove the event, that must be done with |
160 | * fsnotify_remove_first_event() | |
a2d8bc6c | 161 | */ |
8ba8fa91 | 162 | struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group) |
a2d8bc6c | 163 | { |
a2d8bc6c EP |
164 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); |
165 | ||
7053aee2 JK |
166 | return list_first_entry(&group->notification_list, |
167 | struct fsnotify_event, list); | |
a2d8bc6c EP |
168 | } |
169 | ||
170 | /* | |
171 | * Called when a group is being torn down to clean up any outstanding | |
172 | * event notifications. | |
173 | */ | |
174 | void fsnotify_flush_notify(struct fsnotify_group *group) | |
175 | { | |
176 | struct fsnotify_event *event; | |
177 | ||
178 | mutex_lock(&group->notification_mutex); | |
179 | while (!fsnotify_notify_queue_is_empty(group)) { | |
8ba8fa91 | 180 | event = fsnotify_remove_first_event(group); |
7053aee2 | 181 | fsnotify_destroy_event(group, event); |
a2d8bc6c EP |
182 | } |
183 | mutex_unlock(&group->notification_mutex); | |
184 | } | |
185 | ||
a2d8bc6c EP |
186 | /* |
187 | * fsnotify_create_event - Allocate a new event which will be sent to each | |
188 | * group's handle_event function if the group was interested in this | |
189 | * particular event. | |
190 | * | |
7053aee2 | 191 | * @inode the inode which is supposed to receive the event (sometimes a |
a2d8bc6c EP |
192 | * parent of the inode to which the event happened. |
193 | * @mask what actually happened. | |
194 | * @data pointer to the object which was actually affected | |
195 | * @data_type flag indication if the data is a file, path, inode, nothing... | |
62ffe5df | 196 | * @name the filename, if available |
a2d8bc6c | 197 | */ |
7053aee2 JK |
198 | void fsnotify_init_event(struct fsnotify_event *event, struct inode *inode, |
199 | u32 mask) | |
a2d8bc6c | 200 | { |
7053aee2 JK |
201 | INIT_LIST_HEAD(&event->list); |
202 | event->inode = inode; | |
90586523 | 203 | event->mask = mask; |
90586523 | 204 | } |