nfsd4: typo logical vs bitwise negate for want_mask
[linux-btrfs-devel.git] / fs / notify / notification.c
blobee188158a224ad45c5d494319bc7158ba75ed06f
1 /*
2 * Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
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.
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.
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.
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.
34 #include <linux/fs.h>
35 #include <linux/init.h>
36 #include <linux/kernel.h>
37 #include <linux/list.h>
38 #include <linux/module.h>
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>
46 #include <linux/atomic.h>
48 #include <linux/fsnotify_backend.h>
49 #include "fsnotify.h"
51 static struct kmem_cache *fsnotify_event_cachep;
52 static struct kmem_cache *fsnotify_event_holder_cachep;
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'
59 static struct fsnotify_event *q_overflow_event;
60 static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0);
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.
66 u32 fsnotify_get_cookie(void)
68 return atomic_inc_return(&fsnotify_sync_cookie);
70 EXPORT_SYMBOL_GPL(fsnotify_get_cookie);
72 /* return true if the notify queue is empty, false otherwise */
73 bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)
75 BUG_ON(!mutex_is_locked(&group->notification_mutex));
76 return list_empty(&group->notification_list) ? true : false;
79 void fsnotify_get_event(struct fsnotify_event *event)
81 atomic_inc(&event->refcnt);
84 void fsnotify_put_event(struct fsnotify_event *event)
86 if (!event)
87 return;
89 if (atomic_dec_and_test(&event->refcnt)) {
90 pr_debug("%s: event=%p\n", __func__, event);
92 if (event->data_type == FSNOTIFY_EVENT_PATH)
93 path_put(&event->path);
95 BUG_ON(!list_empty(&event->private_data_list));
97 kfree(event->file_name);
98 put_pid(event->tgid);
99 kmem_cache_free(fsnotify_event_cachep, event);
103 struct fsnotify_event_holder *fsnotify_alloc_event_holder(void)
105 return kmem_cache_alloc(fsnotify_event_holder_cachep, GFP_KERNEL);
108 void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder)
110 if (holder)
111 kmem_cache_free(fsnotify_event_holder_cachep, holder);
115 * Find the private data that the group previously attached to this event when
116 * the group added the event to the notification queue (fsnotify_add_notify_event)
118 struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group, struct fsnotify_event *event)
120 struct fsnotify_event_private_data *lpriv;
121 struct fsnotify_event_private_data *priv = NULL;
123 assert_spin_locked(&event->lock);
125 list_for_each_entry(lpriv, &event->private_data_list, event_list) {
126 if (lpriv->group == group) {
127 priv = lpriv;
128 list_del(&priv->event_list);
129 break;
132 return priv;
136 * Add an event to the group notification queue. The group can later pull this
137 * event off the queue to deal with. If the event is successfully added to the
138 * group's notification queue, a reference is taken on event.
140 struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
141 struct fsnotify_event_private_data *priv,
142 struct fsnotify_event *(*merge)(struct list_head *,
143 struct fsnotify_event *))
145 struct fsnotify_event *return_event = NULL;
146 struct fsnotify_event_holder *holder = NULL;
147 struct list_head *list = &group->notification_list;
149 pr_debug("%s: group=%p event=%p priv=%p\n", __func__, group, event, priv);
152 * There is one fsnotify_event_holder embedded inside each fsnotify_event.
153 * Check if we expect to be able to use that holder. If not alloc a new
154 * holder.
155 * For the overflow event it's possible that something will use the in
156 * event holder before we get the lock so we may need to jump back and
157 * alloc a new holder, this can't happen for most events...
159 if (!list_empty(&event->holder.event_list)) {
160 alloc_holder:
161 holder = fsnotify_alloc_event_holder();
162 if (!holder)
163 return ERR_PTR(-ENOMEM);
166 mutex_lock(&group->notification_mutex);
168 if (group->q_len >= group->max_events) {
169 event = q_overflow_event;
172 * we need to return the overflow event
173 * which means we need a ref
175 fsnotify_get_event(event);
176 return_event = event;
178 /* sorry, no private data on the overflow event */
179 priv = NULL;
182 if (!list_empty(list) && merge) {
183 struct fsnotify_event *tmp;
185 tmp = merge(list, event);
186 if (tmp) {
187 mutex_unlock(&group->notification_mutex);
189 if (return_event)
190 fsnotify_put_event(return_event);
191 if (holder != &event->holder)
192 fsnotify_destroy_event_holder(holder);
193 return tmp;
197 spin_lock(&event->lock);
199 if (list_empty(&event->holder.event_list)) {
200 if (unlikely(holder))
201 fsnotify_destroy_event_holder(holder);
202 holder = &event->holder;
203 } else if (unlikely(!holder)) {
204 /* between the time we checked above and got the lock the in
205 * event holder was used, go back and get a new one */
206 spin_unlock(&event->lock);
207 mutex_unlock(&group->notification_mutex);
209 if (return_event) {
210 fsnotify_put_event(return_event);
211 return_event = NULL;
214 goto alloc_holder;
217 group->q_len++;
218 holder->event = event;
220 fsnotify_get_event(event);
221 list_add_tail(&holder->event_list, list);
222 if (priv)
223 list_add_tail(&priv->event_list, &event->private_data_list);
224 spin_unlock(&event->lock);
225 mutex_unlock(&group->notification_mutex);
227 wake_up(&group->notification_waitq);
228 return return_event;
232 * Remove and return the first event from the notification list. There is a
233 * reference held on this event since it was on the list. It is the responsibility
234 * of the caller to drop this reference.
236 struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group)
238 struct fsnotify_event *event;
239 struct fsnotify_event_holder *holder;
241 BUG_ON(!mutex_is_locked(&group->notification_mutex));
243 pr_debug("%s: group=%p\n", __func__, group);
245 holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
247 event = holder->event;
249 spin_lock(&event->lock);
250 holder->event = NULL;
251 list_del_init(&holder->event_list);
252 spin_unlock(&event->lock);
254 /* event == holder means we are referenced through the in event holder */
255 if (holder != &event->holder)
256 fsnotify_destroy_event_holder(holder);
258 group->q_len--;
260 return event;
264 * This will not remove the event, that must be done with fsnotify_remove_notify_event()
266 struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group)
268 struct fsnotify_event *event;
269 struct fsnotify_event_holder *holder;
271 BUG_ON(!mutex_is_locked(&group->notification_mutex));
273 holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
274 event = holder->event;
276 return event;
280 * Called when a group is being torn down to clean up any outstanding
281 * event notifications.
283 void fsnotify_flush_notify(struct fsnotify_group *group)
285 struct fsnotify_event *event;
286 struct fsnotify_event_private_data *priv;
288 mutex_lock(&group->notification_mutex);
289 while (!fsnotify_notify_queue_is_empty(group)) {
290 event = fsnotify_remove_notify_event(group);
291 /* if they don't implement free_event_priv they better not have attached any */
292 if (group->ops->free_event_priv) {
293 spin_lock(&event->lock);
294 priv = fsnotify_remove_priv_from_event(group, event);
295 spin_unlock(&event->lock);
296 if (priv)
297 group->ops->free_event_priv(priv);
299 fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
301 mutex_unlock(&group->notification_mutex);
304 static void initialize_event(struct fsnotify_event *event)
306 INIT_LIST_HEAD(&event->holder.event_list);
307 atomic_set(&event->refcnt, 1);
309 spin_lock_init(&event->lock);
311 INIT_LIST_HEAD(&event->private_data_list);
315 * Caller damn well better be holding whatever mutex is protecting the
316 * old_holder->event_list and the new_event must be a clean event which
317 * cannot be found anywhere else in the kernel.
319 int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
320 struct fsnotify_event *new_event)
322 struct fsnotify_event *old_event = old_holder->event;
323 struct fsnotify_event_holder *new_holder = &new_event->holder;
325 enum event_spinlock_class {
326 SPINLOCK_OLD,
327 SPINLOCK_NEW,
330 pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, new_event);
333 * if the new_event's embedded holder is in use someone
334 * screwed up and didn't give us a clean new event.
336 BUG_ON(!list_empty(&new_holder->event_list));
338 spin_lock_nested(&old_event->lock, SPINLOCK_OLD);
339 spin_lock_nested(&new_event->lock, SPINLOCK_NEW);
341 new_holder->event = new_event;
342 list_replace_init(&old_holder->event_list, &new_holder->event_list);
344 spin_unlock(&new_event->lock);
345 spin_unlock(&old_event->lock);
347 /* event == holder means we are referenced through the in event holder */
348 if (old_holder != &old_event->holder)
349 fsnotify_destroy_event_holder(old_holder);
351 fsnotify_get_event(new_event); /* on the list take reference */
352 fsnotify_put_event(old_event); /* off the list, drop reference */
354 return 0;
357 struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event)
359 struct fsnotify_event *event;
361 event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL);
362 if (!event)
363 return NULL;
365 pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, event);
367 memcpy(event, old_event, sizeof(*event));
368 initialize_event(event);
370 if (event->name_len) {
371 event->file_name = kstrdup(old_event->file_name, GFP_KERNEL);
372 if (!event->file_name) {
373 kmem_cache_free(fsnotify_event_cachep, event);
374 return NULL;
377 event->tgid = get_pid(old_event->tgid);
378 if (event->data_type == FSNOTIFY_EVENT_PATH)
379 path_get(&event->path);
381 return event;
385 * fsnotify_create_event - Allocate a new event which will be sent to each
386 * group's handle_event function if the group was interested in this
387 * particular event.
389 * @to_tell the inode which is supposed to receive the event (sometimes a
390 * parent of the inode to which the event happened.
391 * @mask what actually happened.
392 * @data pointer to the object which was actually affected
393 * @data_type flag indication if the data is a file, path, inode, nothing...
394 * @name the filename, if available
396 struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data,
397 int data_type, const unsigned char *name,
398 u32 cookie, gfp_t gfp)
400 struct fsnotify_event *event;
402 event = kmem_cache_zalloc(fsnotify_event_cachep, gfp);
403 if (!event)
404 return NULL;
406 pr_debug("%s: event=%p to_tell=%p mask=%x data=%p data_type=%d\n",
407 __func__, event, to_tell, mask, data, data_type);
409 initialize_event(event);
411 if (name) {
412 event->file_name = kstrdup(name, gfp);
413 if (!event->file_name) {
414 kmem_cache_free(fsnotify_event_cachep, event);
415 return NULL;
417 event->name_len = strlen(event->file_name);
420 event->tgid = get_pid(task_tgid(current));
421 event->sync_cookie = cookie;
422 event->to_tell = to_tell;
423 event->data_type = data_type;
425 switch (data_type) {
426 case FSNOTIFY_EVENT_PATH: {
427 struct path *path = data;
428 event->path.dentry = path->dentry;
429 event->path.mnt = path->mnt;
430 path_get(&event->path);
431 break;
433 case FSNOTIFY_EVENT_INODE:
434 event->inode = data;
435 break;
436 case FSNOTIFY_EVENT_NONE:
437 event->inode = NULL;
438 event->path.dentry = NULL;
439 event->path.mnt = NULL;
440 break;
441 default:
442 BUG();
445 event->mask = mask;
447 return event;
450 __init int fsnotify_notification_init(void)
452 fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
453 fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);
455 q_overflow_event = fsnotify_create_event(NULL, FS_Q_OVERFLOW, NULL,
456 FSNOTIFY_EVENT_NONE, NULL, 0,
457 GFP_KERNEL);
458 if (!q_overflow_event)
459 panic("unable to allocate fsnotify q_overflow_event\n");
461 return 0;
463 subsys_initcall(fsnotify_notification_init);