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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 | */ | |
b4277d3d | 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 | { | |
74766bbf EP |
107 | if (holder) |
108 | kmem_cache_free(fsnotify_event_holder_cachep, holder); | |
a2d8bc6c EP |
109 | } |
110 | ||
111 | /* | |
e4aff117 EP |
112 | * Find the private data that the group previously attached to this event when |
113 | * the group added the event to the notification queue (fsnotify_add_notify_event) | |
114 | */ | |
115 | struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group, struct fsnotify_event *event) | |
116 | { | |
117 | struct fsnotify_event_private_data *lpriv; | |
118 | struct fsnotify_event_private_data *priv = NULL; | |
119 | ||
120 | assert_spin_locked(&event->lock); | |
121 | ||
122 | list_for_each_entry(lpriv, &event->private_data_list, event_list) { | |
123 | if (lpriv->group == group) { | |
124 | priv = lpriv; | |
125 | list_del(&priv->event_list); | |
126 | break; | |
127 | } | |
128 | } | |
129 | return priv; | |
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 | */ |
e4aff117 | 137 | int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event, |
74766bbf EP |
138 | struct fsnotify_event_private_data *priv, |
139 | int (*merge)(struct list_head *, struct fsnotify_event *)) | |
a2d8bc6c EP |
140 | { |
141 | struct fsnotify_event_holder *holder = NULL; | |
142 | struct list_head *list = &group->notification_list; | |
74766bbf | 143 | int rc = 0; |
e4aff117 | 144 | |
a2d8bc6c EP |
145 | /* |
146 | * There is one fsnotify_event_holder embedded inside each fsnotify_event. | |
147 | * Check if we expect to be able to use that holder. If not alloc a new | |
148 | * holder. | |
149 | * For the overflow event it's possible that something will use the in | |
150 | * event holder before we get the lock so we may need to jump back and | |
151 | * alloc a new holder, this can't happen for most events... | |
152 | */ | |
153 | if (!list_empty(&event->holder.event_list)) { | |
154 | alloc_holder: | |
155 | holder = fsnotify_alloc_event_holder(); | |
156 | if (!holder) | |
157 | return -ENOMEM; | |
158 | } | |
159 | ||
160 | mutex_lock(&group->notification_mutex); | |
161 | ||
e4aff117 | 162 | if (group->q_len >= group->max_events) { |
b4277d3d | 163 | event = q_overflow_event; |
74766bbf | 164 | rc = -EOVERFLOW; |
e4aff117 EP |
165 | /* sorry, no private data on the overflow event */ |
166 | priv = NULL; | |
167 | } | |
a2d8bc6c | 168 | |
74766bbf EP |
169 | if (!list_empty(list) && merge) { |
170 | int ret; | |
171 | ||
172 | ret = merge(list, event); | |
173 | if (ret) { | |
174 | mutex_unlock(&group->notification_mutex); | |
175 | if (holder != &event->holder) | |
176 | fsnotify_destroy_event_holder(holder); | |
177 | return ret; | |
178 | } | |
179 | } | |
180 | ||
a2d8bc6c EP |
181 | spin_lock(&event->lock); |
182 | ||
183 | if (list_empty(&event->holder.event_list)) { | |
184 | if (unlikely(holder)) | |
185 | fsnotify_destroy_event_holder(holder); | |
186 | holder = &event->holder; | |
187 | } else if (unlikely(!holder)) { | |
188 | /* between the time we checked above and got the lock the in | |
189 | * event holder was used, go back and get a new one */ | |
190 | spin_unlock(&event->lock); | |
191 | mutex_unlock(&group->notification_mutex); | |
192 | goto alloc_holder; | |
193 | } | |
194 | ||
a2d8bc6c EP |
195 | group->q_len++; |
196 | holder->event = event; | |
197 | ||
198 | fsnotify_get_event(event); | |
199 | list_add_tail(&holder->event_list, list); | |
e4aff117 EP |
200 | if (priv) |
201 | list_add_tail(&priv->event_list, &event->private_data_list); | |
a2d8bc6c EP |
202 | spin_unlock(&event->lock); |
203 | mutex_unlock(&group->notification_mutex); | |
204 | ||
205 | wake_up(&group->notification_waitq); | |
74766bbf | 206 | return rc; |
a2d8bc6c EP |
207 | } |
208 | ||
209 | /* | |
210 | * Remove and return the first event from the notification list. There is a | |
211 | * reference held on this event since it was on the list. It is the responsibility | |
212 | * of the caller to drop this reference. | |
213 | */ | |
214 | struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group) | |
90586523 EP |
215 | { |
216 | struct fsnotify_event *event; | |
a2d8bc6c | 217 | struct fsnotify_event_holder *holder; |
90586523 | 218 | |
a2d8bc6c | 219 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); |
90586523 | 220 | |
a2d8bc6c EP |
221 | holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list); |
222 | ||
223 | event = holder->event; | |
224 | ||
225 | spin_lock(&event->lock); | |
226 | holder->event = NULL; | |
227 | list_del_init(&holder->event_list); | |
228 | spin_unlock(&event->lock); | |
229 | ||
230 | /* event == holder means we are referenced through the in event holder */ | |
231 | if (holder != &event->holder) | |
232 | fsnotify_destroy_event_holder(holder); | |
233 | ||
234 | group->q_len--; | |
235 | ||
236 | return event; | |
237 | } | |
238 | ||
239 | /* | |
240 | * This will not remove the event, that must be done with fsnotify_remove_notify_event() | |
241 | */ | |
242 | struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group) | |
243 | { | |
244 | struct fsnotify_event *event; | |
245 | struct fsnotify_event_holder *holder; | |
246 | ||
247 | BUG_ON(!mutex_is_locked(&group->notification_mutex)); | |
248 | ||
249 | holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list); | |
250 | event = holder->event; | |
251 | ||
252 | return event; | |
253 | } | |
254 | ||
255 | /* | |
256 | * Called when a group is being torn down to clean up any outstanding | |
257 | * event notifications. | |
258 | */ | |
259 | void fsnotify_flush_notify(struct fsnotify_group *group) | |
260 | { | |
261 | struct fsnotify_event *event; | |
e4aff117 | 262 | struct fsnotify_event_private_data *priv; |
a2d8bc6c EP |
263 | |
264 | mutex_lock(&group->notification_mutex); | |
265 | while (!fsnotify_notify_queue_is_empty(group)) { | |
266 | event = fsnotify_remove_notify_event(group); | |
e4aff117 EP |
267 | /* if they don't implement free_event_priv they better not have attached any */ |
268 | if (group->ops->free_event_priv) { | |
269 | spin_lock(&event->lock); | |
270 | priv = fsnotify_remove_priv_from_event(group, event); | |
271 | spin_unlock(&event->lock); | |
272 | if (priv) | |
273 | group->ops->free_event_priv(priv); | |
274 | } | |
a2d8bc6c EP |
275 | fsnotify_put_event(event); /* matches fsnotify_add_notify_event */ |
276 | } | |
277 | mutex_unlock(&group->notification_mutex); | |
278 | } | |
279 | ||
280 | static void initialize_event(struct fsnotify_event *event) | |
281 | { | |
a2d8bc6c | 282 | INIT_LIST_HEAD(&event->holder.event_list); |
90586523 EP |
283 | atomic_set(&event->refcnt, 1); |
284 | ||
285 | spin_lock_init(&event->lock); | |
286 | ||
e4aff117 | 287 | INIT_LIST_HEAD(&event->private_data_list); |
a2d8bc6c EP |
288 | } |
289 | ||
1201a536 EP |
290 | /* |
291 | * Caller damn well better be holding whatever mutex is protecting the | |
cac69dad EP |
292 | * old_holder->event_list and the new_event must be a clean event which |
293 | * cannot be found anywhere else in the kernel. | |
1201a536 EP |
294 | */ |
295 | int fsnotify_replace_event(struct fsnotify_event_holder *old_holder, | |
296 | struct fsnotify_event *new_event) | |
297 | { | |
298 | struct fsnotify_event *old_event = old_holder->event; | |
cac69dad EP |
299 | struct fsnotify_event_holder *new_holder = &new_event->holder; |
300 | ||
301 | enum event_spinlock_class { | |
302 | SPINLOCK_OLD, | |
303 | SPINLOCK_NEW, | |
304 | }; | |
1201a536 EP |
305 | |
306 | /* | |
cac69dad EP |
307 | * if the new_event's embedded holder is in use someone |
308 | * screwed up and didn't give us a clean new event. | |
1201a536 | 309 | */ |
cac69dad | 310 | BUG_ON(!list_empty(&new_holder->event_list)); |
1201a536 | 311 | |
cac69dad EP |
312 | spin_lock_nested(&old_event->lock, SPINLOCK_OLD); |
313 | spin_lock_nested(&new_event->lock, SPINLOCK_NEW); | |
1201a536 EP |
314 | |
315 | new_holder->event = new_event; | |
316 | list_replace_init(&old_holder->event_list, &new_holder->event_list); | |
317 | ||
318 | spin_unlock(&new_event->lock); | |
319 | spin_unlock(&old_event->lock); | |
320 | ||
321 | /* event == holder means we are referenced through the in event holder */ | |
322 | if (old_holder != &old_event->holder) | |
323 | fsnotify_destroy_event_holder(old_holder); | |
324 | ||
325 | fsnotify_get_event(new_event); /* on the list take reference */ | |
326 | fsnotify_put_event(old_event); /* off the list, drop reference */ | |
327 | ||
328 | return 0; | |
329 | } | |
330 | ||
b4e4e140 EP |
331 | struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event) |
332 | { | |
333 | struct fsnotify_event *event; | |
334 | ||
335 | event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL); | |
336 | if (!event) | |
337 | return NULL; | |
338 | ||
339 | memcpy(event, old_event, sizeof(*event)); | |
340 | initialize_event(event); | |
341 | ||
342 | if (event->name_len) { | |
343 | event->file_name = kstrdup(old_event->file_name, GFP_KERNEL); | |
344 | if (!event->file_name) { | |
345 | kmem_cache_free(fsnotify_event_cachep, event); | |
346 | return NULL; | |
347 | } | |
348 | } | |
349 | if (event->data_type == FSNOTIFY_EVENT_PATH) | |
350 | path_get(&event->path); | |
351 | ||
352 | return event; | |
353 | } | |
354 | ||
a2d8bc6c EP |
355 | /* |
356 | * fsnotify_create_event - Allocate a new event which will be sent to each | |
357 | * group's handle_event function if the group was interested in this | |
358 | * particular event. | |
359 | * | |
360 | * @to_tell the inode which is supposed to receive the event (sometimes a | |
361 | * parent of the inode to which the event happened. | |
362 | * @mask what actually happened. | |
363 | * @data pointer to the object which was actually affected | |
364 | * @data_type flag indication if the data is a file, path, inode, nothing... | |
62ffe5df | 365 | * @name the filename, if available |
a2d8bc6c | 366 | */ |
47882c6f | 367 | struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data, |
f44aebcc EP |
368 | int data_type, const char *name, u32 cookie, |
369 | gfp_t gfp) | |
a2d8bc6c EP |
370 | { |
371 | struct fsnotify_event *event; | |
372 | ||
6f3a539e | 373 | event = kmem_cache_zalloc(fsnotify_event_cachep, gfp); |
a2d8bc6c EP |
374 | if (!event) |
375 | return NULL; | |
376 | ||
377 | initialize_event(event); | |
62ffe5df EP |
378 | |
379 | if (name) { | |
f44aebcc | 380 | event->file_name = kstrdup(name, gfp); |
62ffe5df EP |
381 | if (!event->file_name) { |
382 | kmem_cache_free(fsnotify_event_cachep, event); | |
383 | return NULL; | |
384 | } | |
385 | event->name_len = strlen(event->file_name); | |
386 | } | |
47882c6f EP |
387 | |
388 | event->sync_cookie = cookie; | |
90586523 | 389 | event->to_tell = to_tell; |
b4e4e140 | 390 | event->data_type = data_type; |
90586523 EP |
391 | |
392 | switch (data_type) { | |
393 | case FSNOTIFY_EVENT_FILE: { | |
394 | struct file *file = data; | |
395 | struct path *path = &file->f_path; | |
396 | event->path.dentry = path->dentry; | |
397 | event->path.mnt = path->mnt; | |
398 | path_get(&event->path); | |
399 | event->data_type = FSNOTIFY_EVENT_PATH; | |
400 | break; | |
401 | } | |
402 | case FSNOTIFY_EVENT_PATH: { | |
403 | struct path *path = data; | |
404 | event->path.dentry = path->dentry; | |
405 | event->path.mnt = path->mnt; | |
406 | path_get(&event->path); | |
90586523 EP |
407 | break; |
408 | } | |
409 | case FSNOTIFY_EVENT_INODE: | |
410 | event->inode = data; | |
90586523 EP |
411 | break; |
412 | case FSNOTIFY_EVENT_NONE: | |
413 | event->inode = NULL; | |
414 | event->path.dentry = NULL; | |
415 | event->path.mnt = NULL; | |
416 | break; | |
417 | default: | |
418 | BUG(); | |
419 | } | |
420 | ||
421 | event->mask = mask; | |
422 | ||
423 | return event; | |
424 | } | |
425 | ||
426 | __init int fsnotify_notification_init(void) | |
427 | { | |
428 | fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC); | |
a2d8bc6c EP |
429 | fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC); |
430 | ||
b4277d3d EP |
431 | q_overflow_event = fsnotify_create_event(NULL, FS_Q_OVERFLOW, NULL, |
432 | FSNOTIFY_EVENT_NONE, NULL, 0, | |
433 | GFP_KERNEL); | |
434 | if (!q_overflow_event) | |
435 | panic("unable to allocate fsnotify q_overflow_event\n"); | |
90586523 EP |
436 | |
437 | return 0; | |
438 | } | |
439 | subsys_initcall(fsnotify_notification_init); | |
440 |