]>
Commit | Line | Data |
---|---|---|
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) | |
21 | * sends the userspace notification about events asyncronously some time after | |
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 | ||
46 | #include <asm/atomic.h> | |
47 | ||
48 | #include <linux/fsnotify_backend.h> | |
49 | #include "fsnotify.h" | |
50 | ||
51 | static struct kmem_cache *fsnotify_event_cachep; | |
a2d8bc6c EP |
52 | static struct kmem_cache *fsnotify_event_holder_cachep; |
53 | /* | |
54 | * This is a magic event we send when the q is too full. Since it doesn't | |
55 | * hold real event information we just keep one system wide and use it any time | |
56 | * it is needed. It's refcnt is set 1 at kernel init time and will never | |
57 | * get set to 0 so it will never get 'freed' | |
58 | */ | |
59 | static struct fsnotify_event q_overflow_event; | |
47882c6f EP |
60 | static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0); |
61 | ||
62 | /** | |
63 | * fsnotify_get_cookie - return a unique cookie for use in synchronizing events. | |
64 | * Called from fsnotify_move, which is inlined into filesystem modules. | |
65 | */ | |
66 | u32 fsnotify_get_cookie(void) | |
67 | { | |
68 | return atomic_inc_return(&fsnotify_sync_cookie); | |
69 | } | |
70 | EXPORT_SYMBOL_GPL(fsnotify_get_cookie); | |
a2d8bc6c EP |
71 | |
72 | /* return true if the notify queue is empty, false otherwise */ | |
73 | bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group) | |
74 | { | |
75 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); | |
76 | return list_empty(&group->notification_list) ? true : false; | |
77 | } | |
90586523 EP |
78 | |
79 | void fsnotify_get_event(struct fsnotify_event *event) | |
80 | { | |
81 | atomic_inc(&event->refcnt); | |
82 | } | |
83 | ||
84 | void fsnotify_put_event(struct fsnotify_event *event) | |
85 | { | |
86 | if (!event) | |
87 | return; | |
88 | ||
89 | if (atomic_dec_and_test(&event->refcnt)) { | |
90 | if (event->data_type == FSNOTIFY_EVENT_PATH) | |
91 | path_put(&event->path); | |
92 | ||
62ffe5df | 93 | kfree(event->file_name); |
90586523 EP |
94 | kmem_cache_free(fsnotify_event_cachep, event); |
95 | } | |
96 | } | |
97 | ||
a2d8bc6c EP |
98 | struct fsnotify_event_holder *fsnotify_alloc_event_holder(void) |
99 | { | |
100 | return kmem_cache_alloc(fsnotify_event_holder_cachep, GFP_KERNEL); | |
101 | } | |
102 | ||
103 | void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder) | |
104 | { | |
105 | kmem_cache_free(fsnotify_event_holder_cachep, holder); | |
106 | } | |
107 | ||
108 | /* | |
109 | * check if 2 events contain the same information. | |
110 | */ | |
111 | static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new) | |
112 | { | |
113 | if ((old->mask == new->mask) && | |
114 | (old->to_tell == new->to_tell) && | |
115 | (old->data_type == new->data_type)) { | |
116 | switch (old->data_type) { | |
117 | case (FSNOTIFY_EVENT_INODE): | |
118 | if (old->inode == new->inode) | |
119 | return true; | |
120 | break; | |
121 | case (FSNOTIFY_EVENT_PATH): | |
122 | if ((old->path.mnt == new->path.mnt) && | |
123 | (old->path.dentry == new->path.dentry)) | |
124 | return true; | |
125 | case (FSNOTIFY_EVENT_NONE): | |
126 | return true; | |
127 | }; | |
128 | } | |
129 | return false; | |
130 | } | |
131 | ||
90586523 | 132 | /* |
a2d8bc6c EP |
133 | * Add an event to the group notification queue. The group can later pull this |
134 | * event off the queue to deal with. If the event is successfully added to the | |
135 | * group's notification queue, a reference is taken on event. | |
90586523 | 136 | */ |
a2d8bc6c EP |
137 | int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event) |
138 | { | |
139 | struct fsnotify_event_holder *holder = NULL; | |
140 | struct list_head *list = &group->notification_list; | |
141 | struct fsnotify_event_holder *last_holder; | |
142 | struct fsnotify_event *last_event; | |
143 | ||
144 | /* | |
145 | * There is one fsnotify_event_holder embedded inside each fsnotify_event. | |
146 | * Check if we expect to be able to use that holder. If not alloc a new | |
147 | * holder. | |
148 | * For the overflow event it's possible that something will use the in | |
149 | * event holder before we get the lock so we may need to jump back and | |
150 | * alloc a new holder, this can't happen for most events... | |
151 | */ | |
152 | if (!list_empty(&event->holder.event_list)) { | |
153 | alloc_holder: | |
154 | holder = fsnotify_alloc_event_holder(); | |
155 | if (!holder) | |
156 | return -ENOMEM; | |
157 | } | |
158 | ||
159 | mutex_lock(&group->notification_mutex); | |
160 | ||
161 | if (group->q_len >= group->max_events) | |
162 | event = &q_overflow_event; | |
163 | ||
164 | spin_lock(&event->lock); | |
165 | ||
166 | if (list_empty(&event->holder.event_list)) { | |
167 | if (unlikely(holder)) | |
168 | fsnotify_destroy_event_holder(holder); | |
169 | holder = &event->holder; | |
170 | } else if (unlikely(!holder)) { | |
171 | /* between the time we checked above and got the lock the in | |
172 | * event holder was used, go back and get a new one */ | |
173 | spin_unlock(&event->lock); | |
174 | mutex_unlock(&group->notification_mutex); | |
175 | goto alloc_holder; | |
176 | } | |
177 | ||
178 | if (!list_empty(list)) { | |
179 | last_holder = list_entry(list->prev, struct fsnotify_event_holder, event_list); | |
180 | last_event = last_holder->event; | |
181 | if (event_compare(last_event, event)) { | |
182 | spin_unlock(&event->lock); | |
183 | mutex_unlock(&group->notification_mutex); | |
184 | if (holder != &event->holder) | |
185 | fsnotify_destroy_event_holder(holder); | |
186 | return 0; | |
187 | } | |
188 | } | |
189 | ||
190 | group->q_len++; | |
191 | holder->event = event; | |
192 | ||
193 | fsnotify_get_event(event); | |
194 | list_add_tail(&holder->event_list, list); | |
195 | spin_unlock(&event->lock); | |
196 | mutex_unlock(&group->notification_mutex); | |
197 | ||
198 | wake_up(&group->notification_waitq); | |
199 | return 0; | |
200 | } | |
201 | ||
202 | /* | |
203 | * Remove and return the first event from the notification list. There is a | |
204 | * reference held on this event since it was on the list. It is the responsibility | |
205 | * of the caller to drop this reference. | |
206 | */ | |
207 | struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group) | |
90586523 EP |
208 | { |
209 | struct fsnotify_event *event; | |
a2d8bc6c | 210 | struct fsnotify_event_holder *holder; |
90586523 | 211 | |
a2d8bc6c | 212 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); |
90586523 | 213 | |
a2d8bc6c EP |
214 | holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list); |
215 | ||
216 | event = holder->event; | |
217 | ||
218 | spin_lock(&event->lock); | |
219 | holder->event = NULL; | |
220 | list_del_init(&holder->event_list); | |
221 | spin_unlock(&event->lock); | |
222 | ||
223 | /* event == holder means we are referenced through the in event holder */ | |
224 | if (holder != &event->holder) | |
225 | fsnotify_destroy_event_holder(holder); | |
226 | ||
227 | group->q_len--; | |
228 | ||
229 | return event; | |
230 | } | |
231 | ||
232 | /* | |
233 | * This will not remove the event, that must be done with fsnotify_remove_notify_event() | |
234 | */ | |
235 | struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group) | |
236 | { | |
237 | struct fsnotify_event *event; | |
238 | struct fsnotify_event_holder *holder; | |
239 | ||
240 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); | |
241 | ||
242 | holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list); | |
243 | event = holder->event; | |
244 | ||
245 | return event; | |
246 | } | |
247 | ||
248 | /* | |
249 | * Called when a group is being torn down to clean up any outstanding | |
250 | * event notifications. | |
251 | */ | |
252 | void fsnotify_flush_notify(struct fsnotify_group *group) | |
253 | { | |
254 | struct fsnotify_event *event; | |
255 | ||
256 | mutex_lock(&group->notification_mutex); | |
257 | while (!fsnotify_notify_queue_is_empty(group)) { | |
258 | event = fsnotify_remove_notify_event(group); | |
259 | fsnotify_put_event(event); /* matches fsnotify_add_notify_event */ | |
260 | } | |
261 | mutex_unlock(&group->notification_mutex); | |
262 | } | |
263 | ||
264 | static void initialize_event(struct fsnotify_event *event) | |
265 | { | |
266 | event->holder.event = NULL; | |
267 | INIT_LIST_HEAD(&event->holder.event_list); | |
90586523 EP |
268 | atomic_set(&event->refcnt, 1); |
269 | ||
270 | spin_lock_init(&event->lock); | |
271 | ||
272 | event->path.dentry = NULL; | |
273 | event->path.mnt = NULL; | |
274 | event->inode = NULL; | |
a2d8bc6c | 275 | event->data_type = FSNOTIFY_EVENT_NONE; |
90586523 | 276 | |
a2d8bc6c | 277 | event->to_tell = NULL; |
62ffe5df EP |
278 | |
279 | event->file_name = NULL; | |
280 | event->name_len = 0; | |
47882c6f EP |
281 | |
282 | event->sync_cookie = 0; | |
a2d8bc6c EP |
283 | } |
284 | ||
285 | /* | |
286 | * fsnotify_create_event - Allocate a new event which will be sent to each | |
287 | * group's handle_event function if the group was interested in this | |
288 | * particular event. | |
289 | * | |
290 | * @to_tell the inode which is supposed to receive the event (sometimes a | |
291 | * parent of the inode to which the event happened. | |
292 | * @mask what actually happened. | |
293 | * @data pointer to the object which was actually affected | |
294 | * @data_type flag indication if the data is a file, path, inode, nothing... | |
62ffe5df | 295 | * @name the filename, if available |
a2d8bc6c | 296 | */ |
47882c6f EP |
297 | struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data, |
298 | int data_type, const char *name, u32 cookie) | |
a2d8bc6c EP |
299 | { |
300 | struct fsnotify_event *event; | |
301 | ||
302 | event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL); | |
303 | if (!event) | |
304 | return NULL; | |
305 | ||
306 | initialize_event(event); | |
62ffe5df EP |
307 | |
308 | if (name) { | |
309 | event->file_name = kstrdup(name, GFP_KERNEL); | |
310 | if (!event->file_name) { | |
311 | kmem_cache_free(fsnotify_event_cachep, event); | |
312 | return NULL; | |
313 | } | |
314 | event->name_len = strlen(event->file_name); | |
315 | } | |
47882c6f EP |
316 | |
317 | event->sync_cookie = cookie; | |
90586523 EP |
318 | event->to_tell = to_tell; |
319 | ||
320 | switch (data_type) { | |
321 | case FSNOTIFY_EVENT_FILE: { | |
322 | struct file *file = data; | |
323 | struct path *path = &file->f_path; | |
324 | event->path.dentry = path->dentry; | |
325 | event->path.mnt = path->mnt; | |
326 | path_get(&event->path); | |
327 | event->data_type = FSNOTIFY_EVENT_PATH; | |
328 | break; | |
329 | } | |
330 | case FSNOTIFY_EVENT_PATH: { | |
331 | struct path *path = data; | |
332 | event->path.dentry = path->dentry; | |
333 | event->path.mnt = path->mnt; | |
334 | path_get(&event->path); | |
335 | event->data_type = FSNOTIFY_EVENT_PATH; | |
336 | break; | |
337 | } | |
338 | case FSNOTIFY_EVENT_INODE: | |
339 | event->inode = data; | |
340 | event->data_type = FSNOTIFY_EVENT_INODE; | |
341 | break; | |
342 | case FSNOTIFY_EVENT_NONE: | |
343 | event->inode = NULL; | |
344 | event->path.dentry = NULL; | |
345 | event->path.mnt = NULL; | |
346 | break; | |
347 | default: | |
348 | BUG(); | |
349 | } | |
350 | ||
351 | event->mask = mask; | |
352 | ||
353 | return event; | |
354 | } | |
355 | ||
356 | __init int fsnotify_notification_init(void) | |
357 | { | |
358 | fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC); | |
a2d8bc6c EP |
359 | fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC); |
360 | ||
361 | initialize_event(&q_overflow_event); | |
362 | q_overflow_event.mask = FS_Q_OVERFLOW; | |
90586523 EP |
363 | |
364 | return 0; | |
365 | } | |
366 | subsys_initcall(fsnotify_notification_init); | |
367 |