blob: 521368574e97b5841ec90c52ae8b4215ddc36dd4 [file] [log] [blame]
Eric Paris90586522009-05-21 17:01:20 -04001/*
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
Eric Parisa2d8bc62009-05-21 17:01:37 -040019/*
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
Eric Paris90586522009-05-21 17:01:20 -040034#include <linux/fs.h>
35#include <linux/init.h>
36#include <linux/kernel.h>
37#include <linux/list.h>
Eric Paris47882c62009-05-21 17:01:47 -040038#include <linux/module.h>
Eric Paris90586522009-05-21 17:01:20 -040039#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
51static struct kmem_cache *fsnotify_event_cachep;
Eric Parisa2d8bc62009-05-21 17:01:37 -040052static 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 */
59static struct fsnotify_event q_overflow_event;
Eric Paris47882c62009-05-21 17:01:47 -040060static 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 */
66u32 fsnotify_get_cookie(void)
67{
68 return atomic_inc_return(&fsnotify_sync_cookie);
69}
70EXPORT_SYMBOL_GPL(fsnotify_get_cookie);
Eric Parisa2d8bc62009-05-21 17:01:37 -040071
72/* return true if the notify queue is empty, false otherwise */
73bool 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}
Eric Paris90586522009-05-21 17:01:20 -040078
79void fsnotify_get_event(struct fsnotify_event *event)
80{
81 atomic_inc(&event->refcnt);
82}
83
84void 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
Eric Parise4aff112009-05-21 17:01:50 -040093 BUG_ON(!list_empty(&event->private_data_list));
94
Eric Paris62ffe5d2009-05-21 17:01:43 -040095 kfree(event->file_name);
Eric Paris90586522009-05-21 17:01:20 -040096 kmem_cache_free(fsnotify_event_cachep, event);
97 }
98}
99
Eric Parisa2d8bc62009-05-21 17:01:37 -0400100struct fsnotify_event_holder *fsnotify_alloc_event_holder(void)
101{
102 return kmem_cache_alloc(fsnotify_event_holder_cachep, GFP_KERNEL);
103}
104
105void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder)
106{
107 kmem_cache_free(fsnotify_event_holder_cachep, holder);
108}
109
Eric Paris90586522009-05-21 17:01:20 -0400110/*
Eric Parise4aff112009-05-21 17:01:50 -0400111 * 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 */
114struct 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.
Eric Parisa2d8bc62009-05-21 17:01:37 -0400134 */
135static 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) &&
Eric Paris4a148ba2009-07-13 15:56:55 -0400139 (old->data_type == new->data_type) &&
140 (old->name_len == new->name_len)) {
Eric Parisa2d8bc62009-05-21 17:01:37 -0400141 switch (old->data_type) {
142 case (FSNOTIFY_EVENT_INODE):
Eric Paris4a148ba2009-07-13 15:56:55 -0400143 /* 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))
Eric Parisa2d8bc62009-05-21 17:01:37 -0400148 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;
Eric Parisc05594b2009-07-13 15:56:55 -0400154 break;
Eric Parisa2d8bc62009-05-21 17:01:37 -0400155 case (FSNOTIFY_EVENT_NONE):
Eric Parisf44aebc2009-07-15 15:49:52 -0400156 return false;
Eric Parisa2d8bc62009-05-21 17:01:37 -0400157 };
158 }
159 return false;
160}
161
162/*
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.
166 */
Eric Parise4aff112009-05-21 17:01:50 -0400167int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
168 struct fsnotify_event_private_data *priv)
Eric Parisa2d8bc62009-05-21 17:01:37 -0400169{
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
Eric Parise4aff112009-05-21 17:01:50 -0400175 /* easy to tell if priv was attached to the event */
176 INIT_LIST_HEAD(&priv->event_list);
177
Eric Parisa2d8bc62009-05-21 17:01:37 -0400178 /*
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)) {
187alloc_holder:
188 holder = fsnotify_alloc_event_holder();
189 if (!holder)
190 return -ENOMEM;
191 }
192
193 mutex_lock(&group->notification_mutex);
194
Eric Parise4aff112009-05-21 17:01:50 -0400195 if (group->q_len >= group->max_events) {
Eric Parisa2d8bc62009-05-21 17:01:37 -0400196 event = &q_overflow_event;
Eric Parise4aff112009-05-21 17:01:50 -0400197 /* sorry, no private data on the overflow event */
198 priv = NULL;
199 }
Eric Parisa2d8bc62009-05-21 17:01:37 -0400200
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);
Eric Parise4aff112009-05-21 17:01:50 -0400223 return -EEXIST;
Eric Parisa2d8bc62009-05-21 17:01:37 -0400224 }
225 }
226
227 group->q_len++;
228 holder->event = event;
229
230 fsnotify_get_event(event);
231 list_add_tail(&holder->event_list, list);
Eric Parise4aff112009-05-21 17:01:50 -0400232 if (priv)
233 list_add_tail(&priv->event_list, &event->private_data_list);
Eric Parisa2d8bc62009-05-21 17:01:37 -0400234 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 */
246struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group)
247{
248 struct fsnotify_event *event;
249 struct fsnotify_event_holder *holder;
250
251 BUG_ON(!mutex_is_locked(&group->notification_mutex));
252
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 */
274struct 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 */
291void fsnotify_flush_notify(struct fsnotify_group *group)
292{
293 struct fsnotify_event *event;
Eric Parise4aff112009-05-21 17:01:50 -0400294 struct fsnotify_event_private_data *priv;
Eric Parisa2d8bc62009-05-21 17:01:37 -0400295
296 mutex_lock(&group->notification_mutex);
297 while (!fsnotify_notify_queue_is_empty(group)) {
298 event = fsnotify_remove_notify_event(group);
Eric Parise4aff112009-05-21 17:01:50 -0400299 /* 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 }
Eric Parisa2d8bc62009-05-21 17:01:37 -0400307 fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
308 }
309 mutex_unlock(&group->notification_mutex);
310}
311
312static void initialize_event(struct fsnotify_event *event)
313{
314 event->holder.event = NULL;
315 INIT_LIST_HEAD(&event->holder.event_list);
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;
323 event->data_type = FSNOTIFY_EVENT_NONE;
324
Eric Parise4aff112009-05-21 17:01:50 -0400325 INIT_LIST_HEAD(&event->private_data_list);
326
Eric Parisa2d8bc62009-05-21 17:01:37 -0400327 event->to_tell = NULL;
Eric Paris62ffe5d2009-05-21 17:01:43 -0400328
329 event->file_name = NULL;
330 event->name_len = 0;
Eric Paris47882c62009-05-21 17:01:47 -0400331
332 event->sync_cookie = 0;
Eric Parisa2d8bc62009-05-21 17:01:37 -0400333}
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...
Eric Paris62ffe5d2009-05-21 17:01:43 -0400345 * @name the filename, if available
Eric Paris90586522009-05-21 17:01:20 -0400346 */
Eric Paris47882c62009-05-21 17:01:47 -0400347struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data,
Eric Parisf44aebc2009-07-15 15:49:52 -0400348 int data_type, const char *name, u32 cookie,
349 gfp_t gfp)
Eric Paris90586522009-05-21 17:01:20 -0400350{
351 struct fsnotify_event *event;
352
Eric Parisf44aebc2009-07-15 15:49:52 -0400353 event = kmem_cache_alloc(fsnotify_event_cachep, gfp);
Eric Paris90586522009-05-21 17:01:20 -0400354 if (!event)
355 return NULL;
356
Eric Parisa2d8bc62009-05-21 17:01:37 -0400357 initialize_event(event);
Eric Paris62ffe5d2009-05-21 17:01:43 -0400358
359 if (name) {
Eric Parisf44aebc2009-07-15 15:49:52 -0400360 event->file_name = kstrdup(name, gfp);
Eric Paris62ffe5d2009-05-21 17:01:43 -0400361 if (!event->file_name) {
362 kmem_cache_free(fsnotify_event_cachep, event);
363 return NULL;
364 }
365 event->name_len = strlen(event->file_name);
366 }
Eric Paris47882c62009-05-21 17:01:47 -0400367
368 event->sync_cookie = cookie;
Eric Paris90586522009-05-21 17:01:20 -0400369 event->to_tell = to_tell;
370
371 switch (data_type) {
372 case FSNOTIFY_EVENT_FILE: {
373 struct file *file = data;
374 struct path *path = &file->f_path;
375 event->path.dentry = path->dentry;
376 event->path.mnt = path->mnt;
377 path_get(&event->path);
378 event->data_type = FSNOTIFY_EVENT_PATH;
379 break;
380 }
381 case FSNOTIFY_EVENT_PATH: {
382 struct path *path = data;
383 event->path.dentry = path->dentry;
384 event->path.mnt = path->mnt;
385 path_get(&event->path);
386 event->data_type = FSNOTIFY_EVENT_PATH;
387 break;
388 }
389 case FSNOTIFY_EVENT_INODE:
390 event->inode = data;
391 event->data_type = FSNOTIFY_EVENT_INODE;
392 break;
393 case FSNOTIFY_EVENT_NONE:
394 event->inode = NULL;
395 event->path.dentry = NULL;
396 event->path.mnt = NULL;
397 break;
398 default:
399 BUG();
400 }
401
402 event->mask = mask;
403
404 return event;
405}
406
407__init int fsnotify_notification_init(void)
408{
409 fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
Eric Parisa2d8bc62009-05-21 17:01:37 -0400410 fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);
411
412 initialize_event(&q_overflow_event);
413 q_overflow_event.mask = FS_Q_OVERFLOW;
Eric Paris90586522009-05-21 17:01:20 -0400414
415 return 0;
416}
417subsys_initcall(fsnotify_notification_init);
418