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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) | |
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 | ||
e4aff117 EP |
93 | BUG_ON(!list_empty(&event->private_data_list)); |
94 | ||
62ffe5df | 95 | kfree(event->file_name); |
90586523 EP |
96 | kmem_cache_free(fsnotify_event_cachep, event); |
97 | } | |
98 | } | |
99 | ||
a2d8bc6c EP |
100 | struct fsnotify_event_holder *fsnotify_alloc_event_holder(void) |
101 | { | |
102 | return kmem_cache_alloc(fsnotify_event_holder_cachep, GFP_KERNEL); | |
103 | } | |
104 | ||
105 | void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder) | |
106 | { | |
107 | kmem_cache_free(fsnotify_event_holder_cachep, holder); | |
108 | } | |
109 | ||
110 | /* | |
e4aff117 EP |
111 | * Find the private data that the group previously attached to this event when |
112 | * the group added the event to the notification queue (fsnotify_add_notify_event) | |
113 | */ | |
114 | struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group, struct fsnotify_event *event) | |
115 | { | |
116 | struct fsnotify_event_private_data *lpriv; | |
117 | struct fsnotify_event_private_data *priv = NULL; | |
118 | ||
119 | assert_spin_locked(&event->lock); | |
120 | ||
121 | list_for_each_entry(lpriv, &event->private_data_list, event_list) { | |
122 | if (lpriv->group == group) { | |
123 | priv = lpriv; | |
124 | list_del(&priv->event_list); | |
125 | break; | |
126 | } | |
127 | } | |
128 | return priv; | |
129 | } | |
130 | ||
131 | /* | |
132 | * Check if 2 events contain the same information. We do not compare private data | |
133 | * but at this moment that isn't a problem for any know fsnotify listeners. | |
a2d8bc6c EP |
134 | */ |
135 | static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new) | |
136 | { | |
137 | if ((old->mask == new->mask) && | |
138 | (old->to_tell == new->to_tell) && | |
4a148ba9 EP |
139 | (old->data_type == new->data_type) && |
140 | (old->name_len == new->name_len)) { | |
a2d8bc6c EP |
141 | switch (old->data_type) { |
142 | case (FSNOTIFY_EVENT_INODE): | |
4a148ba9 EP |
143 | /* remember, after old was put on the wait_q we aren't |
144 | * allowed to look at the inode any more, only thing | |
145 | * left to check was if the file_name is the same */ | |
146 | if (old->name_len && | |
147 | !strcmp(old->file_name, new->file_name)) | |
a2d8bc6c EP |
148 | return true; |
149 | break; | |
150 | case (FSNOTIFY_EVENT_PATH): | |
151 | if ((old->path.mnt == new->path.mnt) && | |
152 | (old->path.dentry == new->path.dentry)) | |
153 | return true; | |
c05594b6 | 154 | break; |
a2d8bc6c EP |
155 | case (FSNOTIFY_EVENT_NONE): |
156 | return true; | |
157 | }; | |
158 | } | |
159 | return false; | |
160 | } | |
161 | ||
90586523 | 162 | /* |
a2d8bc6c EP |
163 | * Add an event to the group notification queue. The group can later pull this |
164 | * event off the queue to deal with. If the event is successfully added to the | |
165 | * group's notification queue, a reference is taken on event. | |
90586523 | 166 | */ |
e4aff117 EP |
167 | int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event, |
168 | struct fsnotify_event_private_data *priv) | |
a2d8bc6c EP |
169 | { |
170 | struct fsnotify_event_holder *holder = NULL; | |
171 | struct list_head *list = &group->notification_list; | |
172 | struct fsnotify_event_holder *last_holder; | |
173 | struct fsnotify_event *last_event; | |
174 | ||
e4aff117 EP |
175 | /* easy to tell if priv was attached to the event */ |
176 | INIT_LIST_HEAD(&priv->event_list); | |
177 | ||
a2d8bc6c EP |
178 | /* |
179 | * There is one fsnotify_event_holder embedded inside each fsnotify_event. | |
180 | * Check if we expect to be able to use that holder. If not alloc a new | |
181 | * holder. | |
182 | * For the overflow event it's possible that something will use the in | |
183 | * event holder before we get the lock so we may need to jump back and | |
184 | * alloc a new holder, this can't happen for most events... | |
185 | */ | |
186 | if (!list_empty(&event->holder.event_list)) { | |
187 | alloc_holder: | |
188 | holder = fsnotify_alloc_event_holder(); | |
189 | if (!holder) | |
190 | return -ENOMEM; | |
191 | } | |
192 | ||
193 | mutex_lock(&group->notification_mutex); | |
194 | ||
e4aff117 | 195 | if (group->q_len >= group->max_events) { |
a2d8bc6c | 196 | event = &q_overflow_event; |
e4aff117 EP |
197 | /* sorry, no private data on the overflow event */ |
198 | priv = NULL; | |
199 | } | |
a2d8bc6c EP |
200 | |
201 | spin_lock(&event->lock); | |
202 | ||
203 | if (list_empty(&event->holder.event_list)) { | |
204 | if (unlikely(holder)) | |
205 | fsnotify_destroy_event_holder(holder); | |
206 | holder = &event->holder; | |
207 | } else if (unlikely(!holder)) { | |
208 | /* between the time we checked above and got the lock the in | |
209 | * event holder was used, go back and get a new one */ | |
210 | spin_unlock(&event->lock); | |
211 | mutex_unlock(&group->notification_mutex); | |
212 | goto alloc_holder; | |
213 | } | |
214 | ||
215 | if (!list_empty(list)) { | |
216 | last_holder = list_entry(list->prev, struct fsnotify_event_holder, event_list); | |
217 | last_event = last_holder->event; | |
218 | if (event_compare(last_event, event)) { | |
219 | spin_unlock(&event->lock); | |
220 | mutex_unlock(&group->notification_mutex); | |
221 | if (holder != &event->holder) | |
222 | fsnotify_destroy_event_holder(holder); | |
e4aff117 | 223 | return -EEXIST; |
a2d8bc6c EP |
224 | } |
225 | } | |
226 | ||
227 | group->q_len++; | |
228 | holder->event = event; | |
229 | ||
230 | fsnotify_get_event(event); | |
231 | list_add_tail(&holder->event_list, list); | |
e4aff117 EP |
232 | if (priv) |
233 | list_add_tail(&priv->event_list, &event->private_data_list); | |
a2d8bc6c EP |
234 | spin_unlock(&event->lock); |
235 | mutex_unlock(&group->notification_mutex); | |
236 | ||
237 | wake_up(&group->notification_waitq); | |
238 | return 0; | |
239 | } | |
240 | ||
241 | /* | |
242 | * Remove and return the first event from the notification list. There is a | |
243 | * reference held on this event since it was on the list. It is the responsibility | |
244 | * of the caller to drop this reference. | |
245 | */ | |
246 | struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group) | |
90586523 EP |
247 | { |
248 | struct fsnotify_event *event; | |
a2d8bc6c | 249 | struct fsnotify_event_holder *holder; |
90586523 | 250 | |
a2d8bc6c | 251 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); |
90586523 | 252 | |
a2d8bc6c EP |
253 | holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list); |
254 | ||
255 | event = holder->event; | |
256 | ||
257 | spin_lock(&event->lock); | |
258 | holder->event = NULL; | |
259 | list_del_init(&holder->event_list); | |
260 | spin_unlock(&event->lock); | |
261 | ||
262 | /* event == holder means we are referenced through the in event holder */ | |
263 | if (holder != &event->holder) | |
264 | fsnotify_destroy_event_holder(holder); | |
265 | ||
266 | group->q_len--; | |
267 | ||
268 | return event; | |
269 | } | |
270 | ||
271 | /* | |
272 | * This will not remove the event, that must be done with fsnotify_remove_notify_event() | |
273 | */ | |
274 | struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group) | |
275 | { | |
276 | struct fsnotify_event *event; | |
277 | struct fsnotify_event_holder *holder; | |
278 | ||
279 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); | |
280 | ||
281 | holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list); | |
282 | event = holder->event; | |
283 | ||
284 | return event; | |
285 | } | |
286 | ||
287 | /* | |
288 | * Called when a group is being torn down to clean up any outstanding | |
289 | * event notifications. | |
290 | */ | |
291 | void fsnotify_flush_notify(struct fsnotify_group *group) | |
292 | { | |
293 | struct fsnotify_event *event; | |
e4aff117 | 294 | struct fsnotify_event_private_data *priv; |
a2d8bc6c EP |
295 | |
296 | mutex_lock(&group->notification_mutex); | |
297 | while (!fsnotify_notify_queue_is_empty(group)) { | |
298 | event = fsnotify_remove_notify_event(group); | |
e4aff117 EP |
299 | /* if they don't implement free_event_priv they better not have attached any */ |
300 | if (group->ops->free_event_priv) { | |
301 | spin_lock(&event->lock); | |
302 | priv = fsnotify_remove_priv_from_event(group, event); | |
303 | spin_unlock(&event->lock); | |
304 | if (priv) | |
305 | group->ops->free_event_priv(priv); | |
306 | } | |
a2d8bc6c EP |
307 | fsnotify_put_event(event); /* matches fsnotify_add_notify_event */ |
308 | } | |
309 | mutex_unlock(&group->notification_mutex); | |
310 | } | |
311 | ||
312 | static void initialize_event(struct fsnotify_event *event) | |
313 | { | |
314 | event->holder.event = NULL; | |
315 | INIT_LIST_HEAD(&event->holder.event_list); | |
90586523 EP |
316 | atomic_set(&event->refcnt, 1); |
317 | ||
318 | spin_lock_init(&event->lock); | |
319 | ||
320 | event->path.dentry = NULL; | |
321 | event->path.mnt = NULL; | |
322 | event->inode = NULL; | |
a2d8bc6c | 323 | event->data_type = FSNOTIFY_EVENT_NONE; |
90586523 | 324 | |
e4aff117 EP |
325 | INIT_LIST_HEAD(&event->private_data_list); |
326 | ||
a2d8bc6c | 327 | event->to_tell = NULL; |
62ffe5df EP |
328 | |
329 | event->file_name = NULL; | |
330 | event->name_len = 0; | |
47882c6f EP |
331 | |
332 | event->sync_cookie = 0; | |
a2d8bc6c EP |
333 | } |
334 | ||
335 | /* | |
336 | * fsnotify_create_event - Allocate a new event which will be sent to each | |
337 | * group's handle_event function if the group was interested in this | |
338 | * particular event. | |
339 | * | |
340 | * @to_tell the inode which is supposed to receive the event (sometimes a | |
341 | * parent of the inode to which the event happened. | |
342 | * @mask what actually happened. | |
343 | * @data pointer to the object which was actually affected | |
344 | * @data_type flag indication if the data is a file, path, inode, nothing... | |
62ffe5df | 345 | * @name the filename, if available |
a2d8bc6c | 346 | */ |
47882c6f EP |
347 | struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data, |
348 | int data_type, const char *name, u32 cookie) | |
a2d8bc6c EP |
349 | { |
350 | struct fsnotify_event *event; | |
351 | ||
352 | event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL); | |
353 | if (!event) | |
354 | return NULL; | |
355 | ||
356 | initialize_event(event); | |
62ffe5df EP |
357 | |
358 | if (name) { | |
359 | event->file_name = kstrdup(name, GFP_KERNEL); | |
360 | if (!event->file_name) { | |
361 | kmem_cache_free(fsnotify_event_cachep, event); | |
362 | return NULL; | |
363 | } | |
364 | event->name_len = strlen(event->file_name); | |
365 | } | |
47882c6f EP |
366 | |
367 | event->sync_cookie = cookie; | |
90586523 EP |
368 | event->to_tell = to_tell; |
369 | ||
370 | switch (data_type) { | |
371 | case FSNOTIFY_EVENT_FILE: { | |
372 | struct file *file = data; | |
373 | struct path *path = &file->f_path; | |
374 | event->path.dentry = path->dentry; | |
375 | event->path.mnt = path->mnt; | |
376 | path_get(&event->path); | |
377 | event->data_type = FSNOTIFY_EVENT_PATH; | |
378 | break; | |
379 | } | |
380 | case FSNOTIFY_EVENT_PATH: { | |
381 | struct path *path = data; | |
382 | event->path.dentry = path->dentry; | |
383 | event->path.mnt = path->mnt; | |
384 | path_get(&event->path); | |
385 | event->data_type = FSNOTIFY_EVENT_PATH; | |
386 | break; | |
387 | } | |
388 | case FSNOTIFY_EVENT_INODE: | |
389 | event->inode = data; | |
390 | event->data_type = FSNOTIFY_EVENT_INODE; | |
391 | break; | |
392 | case FSNOTIFY_EVENT_NONE: | |
393 | event->inode = NULL; | |
394 | event->path.dentry = NULL; | |
395 | event->path.mnt = NULL; | |
396 | break; | |
397 | default: | |
398 | BUG(); | |
399 | } | |
400 | ||
401 | event->mask = mask; | |
402 | ||
403 | return event; | |
404 | } | |
405 | ||
406 | __init int fsnotify_notification_init(void) | |
407 | { | |
408 | fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC); | |
a2d8bc6c EP |
409 | fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC); |
410 | ||
411 | initialize_event(&q_overflow_event); | |
412 | q_overflow_event.mask = FS_Q_OVERFLOW; | |
90586523 EP |
413 | |
414 | return 0; | |
415 | } | |
416 | subsys_initcall(fsnotify_notification_init); | |
417 |