[net-next-2.6.git] / fs / notify / notification.c

/*
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 * Basic idea behind the notification queue: An fsnotify group (like inotify)
 * sends the userspace notification about events asyncronously some time after
 * the event happened.  When inotify gets an event it will need to add that
 * event to the group notify queue.  Since a single event might need to be on
 * multiple group's notification queues we can't add the event directly to each
 * queue and instead add a small "event_holder" to each queue.  This event_holder
 * has a pointer back to the original event.  Since the majority of events are
 * going to end up on one, and only one, notification queue we embed one
 * event_holder into each event.  This means we have a single allocation instead
 * of always needing two.  If the embedded event_holder is already in use by
 * another group a new event_holder (from fsnotify_event_holder_cachep) will be
 * allocated and used.
 */

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/mutex.h>
#include <linux/namei.h>
#include <linux/path.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

#include <asm/atomic.h>

#include <linux/fsnotify_backend.h>
#include "fsnotify.h"

static struct kmem_cache *fsnotify_event_cachep;
static struct kmem_cache *fsnotify_event_holder_cachep;
/*
 * This is a magic event we send when the q is too full.  Since it doesn't
 * hold real event information we just keep one system wide and use it any time
 * it is needed.  It's refcnt is set 1 at kernel init time and will never
 * get set to 0 so it will never get 'freed'
 */
static struct fsnotify_event *q_overflow_event;
static atomic_t fsnotify_sync_cookie = ATOMIC_INIT(0);

/**
 * fsnotify_get_cookie - return a unique cookie for use in synchronizing events.
 * Called from fsnotify_move, which is inlined into filesystem modules.
 */
u32 fsnotify_get_cookie(void)
{
	return atomic_inc_return(&fsnotify_sync_cookie);
}
EXPORT_SYMBOL_GPL(fsnotify_get_cookie);

/* return true if the notify queue is empty, false otherwise */
bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group)
{
	BUG_ON(!mutex_is_locked(&group->notification_mutex));
	return list_empty(&group->notification_list) ? true : false;
}

void fsnotify_get_event(struct fsnotify_event *event)
{
	atomic_inc(&event->refcnt);
}

void fsnotify_put_event(struct fsnotify_event *event)
{
	if (!event)
		return;

	if (atomic_dec_and_test(&event->refcnt)) {
		if (event->data_type == FSNOTIFY_EVENT_PATH)
			path_put(&event->path);

		BUG_ON(!list_empty(&event->private_data_list));

		kfree(event->file_name);
		kmem_cache_free(fsnotify_event_cachep, event);
	}
}

struct fsnotify_event_holder *fsnotify_alloc_event_holder(void)
{
	return kmem_cache_alloc(fsnotify_event_holder_cachep, GFP_KERNEL);
}

void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder)
{
	kmem_cache_free(fsnotify_event_holder_cachep, holder);
}

/*
 * Find the private data that the group previously attached to this event when
 * the group added the event to the notification queue (fsnotify_add_notify_event)
 */
struct fsnotify_event_private_data *fsnotify_remove_priv_from_event(struct fsnotify_group *group, struct fsnotify_event *event)
{
	struct fsnotify_event_private_data *lpriv;
	struct fsnotify_event_private_data *priv = NULL;

	assert_spin_locked(&event->lock);

	list_for_each_entry(lpriv, &event->private_data_list, event_list) {
		if (lpriv->group == group) {
			priv = lpriv;
			list_del(&priv->event_list);
			break;
		}
	}
	return priv;
}

/*
 * Check if 2 events contain the same information.  We do not compare private data
 * but at this moment that isn't a problem for any know fsnotify listeners.
 */
static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new)
{
	if ((old->mask == new->mask) &&
	    (old->to_tell == new->to_tell) &&
	    (old->data_type == new->data_type) &&
	    (old->name_len == new->name_len)) {
		switch (old->data_type) {
		case (FSNOTIFY_EVENT_INODE):
			/* remember, after old was put on the wait_q we aren't
			 * allowed to look at the inode any more, only thing
			 * left to check was if the file_name is the same */
			if (!old->name_len ||
			    !strcmp(old->file_name, new->file_name))
				return true;
			break;
		case (FSNOTIFY_EVENT_PATH):
			if ((old->path.mnt == new->path.mnt) &&
			    (old->path.dentry == new->path.dentry))
				return true;
			break;
		case (FSNOTIFY_EVENT_NONE):
			if (old->mask & FS_Q_OVERFLOW)
				return true;
			else if (old->mask & FS_IN_IGNORED)
				return false;
			return false;
		};
	}
	return false;
}

/*
 * Add an event to the group notification queue.  The group can later pull this
 * event off the queue to deal with.  If the event is successfully added to the
 * group's notification queue, a reference is taken on event.
 */
int fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
			      struct fsnotify_event_private_data *priv)
{
	struct fsnotify_event_holder *holder = NULL;
	struct list_head *list = &group->notification_list;
	struct fsnotify_event_holder *last_holder;
	struct fsnotify_event *last_event;
	int ret = 0;

	/*
	 * There is one fsnotify_event_holder embedded inside each fsnotify_event.
	 * Check if we expect to be able to use that holder.  If not alloc a new
	 * holder.
	 * For the overflow event it's possible that something will use the in
	 * event holder before we get the lock so we may need to jump back and
	 * alloc a new holder, this can't happen for most events...
	 */
	if (!list_empty(&event->holder.event_list)) {
alloc_holder:
		holder = fsnotify_alloc_event_holder();
		if (!holder)
			return -ENOMEM;
	}

	mutex_lock(&group->notification_mutex);

	if (group->q_len >= group->max_events) {
		event = q_overflow_event;
		ret = -EOVERFLOW;
		/* sorry, no private data on the overflow event */
		priv = NULL;
	}

	spin_lock(&event->lock);

	if (list_empty(&event->holder.event_list)) {
		if (unlikely(holder))
			fsnotify_destroy_event_holder(holder);
		holder = &event->holder;
	} else if (unlikely(!holder)) {
		/* between the time we checked above and got the lock the in
		 * event holder was used, go back and get a new one */
		spin_unlock(&event->lock);
		mutex_unlock(&group->notification_mutex);
		goto alloc_holder;
	}

	if (!list_empty(list)) {
		last_holder = list_entry(list->prev, struct fsnotify_event_holder, event_list);
		last_event = last_holder->event;
		if (event_compare(last_event, event)) {
			spin_unlock(&event->lock);
			mutex_unlock(&group->notification_mutex);
			if (holder != &event->holder)
				fsnotify_destroy_event_holder(holder);
			return -EEXIST;
		}
	}

	group->q_len++;
	holder->event = event;

	fsnotify_get_event(event);
	list_add_tail(&holder->event_list, list);
	if (priv)
		list_add_tail(&priv->event_list, &event->private_data_list);
	spin_unlock(&event->lock);
	mutex_unlock(&group->notification_mutex);

	wake_up(&group->notification_waitq);
	return ret;
}

/*
 * Remove and return the first event from the notification list.  There is a
 * reference held on this event since it was on the list.  It is the responsibility
 * of the caller to drop this reference.
 */
struct fsnotify_event *fsnotify_remove_notify_event(struct fsnotify_group *group)
{
	struct fsnotify_event *event;
	struct fsnotify_event_holder *holder;

	BUG_ON(!mutex_is_locked(&group->notification_mutex));

	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);

	event = holder->event;

	spin_lock(&event->lock);
	holder->event = NULL;
	list_del_init(&holder->event_list);
	spin_unlock(&event->lock);

	/* event == holder means we are referenced through the in event holder */
	if (holder != &event->holder)
		fsnotify_destroy_event_holder(holder);

	group->q_len--;

	return event;
}

/*
 * This will not remove the event, that must be done with fsnotify_remove_notify_event()
 */
struct fsnotify_event *fsnotify_peek_notify_event(struct fsnotify_group *group)
{
	struct fsnotify_event *event;
	struct fsnotify_event_holder *holder;

	BUG_ON(!mutex_is_locked(&group->notification_mutex));

	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
	event = holder->event;

	return event;
}

/*
 * Called when a group is being torn down to clean up any outstanding
 * event notifications.
 */
void fsnotify_flush_notify(struct fsnotify_group *group)
{
	struct fsnotify_event *event;
	struct fsnotify_event_private_data *priv;

	mutex_lock(&group->notification_mutex);
	while (!fsnotify_notify_queue_is_empty(group)) {
		event = fsnotify_remove_notify_event(group);
		/* if they don't implement free_event_priv they better not have attached any */
		if (group->ops->free_event_priv) {
			spin_lock(&event->lock);
			priv = fsnotify_remove_priv_from_event(group, event);
			spin_unlock(&event->lock);
			if (priv)
				group->ops->free_event_priv(priv);
		}
		fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
	}
	mutex_unlock(&group->notification_mutex);
}

static void initialize_event(struct fsnotify_event *event)
{
	INIT_LIST_HEAD(&event->holder.event_list);
	atomic_set(&event->refcnt, 1);

	spin_lock_init(&event->lock);

	event->data_type = FSNOTIFY_EVENT_NONE;

	INIT_LIST_HEAD(&event->private_data_list);
}

/*
 * fsnotify_create_event - Allocate a new event which will be sent to each
 * group's handle_event function if the group was interested in this
 * particular event.
 *
 * @to_tell the inode which is supposed to receive the event (sometimes a
 *	parent of the inode to which the event happened.
 * @mask what actually happened.
 * @data pointer to the object which was actually affected
 * @data_type flag indication if the data is a file, path, inode, nothing...
 * @name the filename, if available
 */
struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data,
					     int data_type, const char *name, u32 cookie,
					     gfp_t gfp)
{
	struct fsnotify_event *event;

	event = kmem_cache_zalloc(fsnotify_event_cachep, gfp);
	if (!event)
		return NULL;

	initialize_event(event);

	if (name) {
		event->file_name = kstrdup(name, gfp);
		if (!event->file_name) {
			kmem_cache_free(fsnotify_event_cachep, event);
			return NULL;
		}
		event->name_len = strlen(event->file_name);
	}

	event->sync_cookie = cookie;
	event->to_tell = to_tell;

	switch (data_type) {
	case FSNOTIFY_EVENT_FILE: {
		struct file *file = data;
		struct path *path = &file->f_path;
		event->path.dentry = path->dentry;
		event->path.mnt = path->mnt;
		path_get(&event->path);
		event->data_type = FSNOTIFY_EVENT_PATH;
		break;
	}
	case FSNOTIFY_EVENT_PATH: {
		struct path *path = data;
		event->path.dentry = path->dentry;
		event->path.mnt = path->mnt;
		path_get(&event->path);
		event->data_type = FSNOTIFY_EVENT_PATH;
		break;
	}
	case FSNOTIFY_EVENT_INODE:
		event->inode = data;
		event->data_type = FSNOTIFY_EVENT_INODE;
		break;
	case FSNOTIFY_EVENT_NONE:
		event->inode = NULL;
		event->path.dentry = NULL;
		event->path.mnt = NULL;
		break;
	default:
		BUG();
	}

	event->mask = mask;

	return event;
}

__init int fsnotify_notification_init(void)
{
	fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
	fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);

	q_overflow_event = fsnotify_create_event(NULL, FS_Q_OVERFLOW, NULL,
						 FSNOTIFY_EVENT_NONE, NULL, 0,
						 GFP_KERNEL);
	if (!q_overflow_event)
		panic("unable to allocate fsnotify q_overflow_event\n");

	return 0;
}
subsys_initcall(fsnotify_notification_init);
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	*/
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));
e4aff117 EP	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) &&
4a148ba9 EP	140	(old->name_len == new->name_len)) {
a2d8bc6c EP	141	switch (old->data_type) {
a2d8bc6c EP	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 */
3de0ef4f	146	if (!old->name_len \|\|
4a148ba9	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	155	case (FSNOTIFY_EVENT_NONE):
cd94c8bb EP	156	if (old->mask & FS_Q_OVERFLOW)
	157	return true;
	158	else if (old->mask & FS_IN_IGNORED)
	159	return false;
f44aebcc	160	return false;
a2d8bc6c EP	161	};
	162	}
	163	return false;
	164	}
	165
90586523	166	/*
a2d8bc6c EP	167	* Add an event to the group notification queue. The group can later pull this
	168	* event off the queue to deal with. If the event is successfully added to the
	169	* group's notification queue, a reference is taken on event.
90586523	170	*/
e4aff117 EP	171	int fsnotify_add_notify_event(struct fsnotify_group group, struct fsnotify_event event,
e4aff117 EP	172	struct fsnotify_event_private_data *priv)
a2d8bc6c EP	173	{
	174	struct fsnotify_event_holder *holder = NULL;
	175	struct list_head *list = &group->notification_list;
	176	struct fsnotify_event_holder *last_holder;
	177	struct fsnotify_event *last_event;
eef3a116	178	int ret = 0;
e4aff117	179
a2d8bc6c EP	180	/*
	181	* There is one fsnotify_event_holder embedded inside each fsnotify_event.
	182	* Check if we expect to be able to use that holder. If not alloc a new
	183	* holder.
	184	* For the overflow event it's possible that something will use the in
	185	* event holder before we get the lock so we may need to jump back and
	186	* alloc a new holder, this can't happen for most events...
	187	*/
	188	if (!list_empty(&event->holder.event_list)) {
	189	alloc_holder:
	190	holder = fsnotify_alloc_event_holder();
	191	if (!holder)
	192	return -ENOMEM;
	193	}
	194
	195	mutex_lock(&group->notification_mutex);
	196
e4aff117	197	if (group->q_len >= group->max_events) {
b4277d3d	198	event = q_overflow_event;
eef3a116	199	ret = -EOVERFLOW;
e4aff117 EP	200	/* sorry, no private data on the overflow event */
	201	priv = NULL;
	202	}
a2d8bc6c EP	203
	204	spin_lock(&event->lock);
	205
	206	if (list_empty(&event->holder.event_list)) {
	207	if (unlikely(holder))
	208	fsnotify_destroy_event_holder(holder);
	209	holder = &event->holder;
	210	} else if (unlikely(!holder)) {
	211	/* between the time we checked above and got the lock the in
	212	* event holder was used, go back and get a new one */
	213	spin_unlock(&event->lock);
	214	mutex_unlock(&group->notification_mutex);
	215	goto alloc_holder;
	216	}
	217
	218	if (!list_empty(list)) {
	219	last_holder = list_entry(list->prev, struct fsnotify_event_holder, event_list);
	220	last_event = last_holder->event;
	221	if (event_compare(last_event, event)) {
	222	spin_unlock(&event->lock);
	223	mutex_unlock(&group->notification_mutex);
	224	if (holder != &event->holder)
	225	fsnotify_destroy_event_holder(holder);
e4aff117	226	return -EEXIST;
a2d8bc6c EP	227	}
	228	}
	229
	230	group->q_len++;
	231	holder->event = event;
	232
	233	fsnotify_get_event(event);
	234	list_add_tail(&holder->event_list, list);
e4aff117 EP	235	if (priv)
e4aff117 EP	236	list_add_tail(&priv->event_list, &event->private_data_list);
a2d8bc6c EP	237	spin_unlock(&event->lock);
	238	mutex_unlock(&group->notification_mutex);
	239
	240	wake_up(&group->notification_waitq);
eef3a116	241	return ret;
a2d8bc6c EP	242	}
	243
	244	/*
	245	* Remove and return the first event from the notification list. There is a
	246	* reference held on this event since it was on the list. It is the responsibility
	247	* of the caller to drop this reference.
	248	*/
	249	struct fsnotify_event fsnotify_remove_notify_event(struct fsnotify_group group)
90586523 EP	250	{
90586523 EP	251	struct fsnotify_event *event;
a2d8bc6c	252	struct fsnotify_event_holder *holder;
90586523	253
a2d8bc6c	254	BUG_ON(!mutex_is_locked(&group->notification_mutex));
90586523	255
a2d8bc6c EP	256	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
	257
	258	event = holder->event;
	259
	260	spin_lock(&event->lock);
	261	holder->event = NULL;
	262	list_del_init(&holder->event_list);
	263	spin_unlock(&event->lock);
	264
	265	/* event == holder means we are referenced through the in event holder */
	266	if (holder != &event->holder)
	267	fsnotify_destroy_event_holder(holder);
	268
	269	group->q_len--;
	270
	271	return event;
	272	}
	273
	274	/*
	275	* This will not remove the event, that must be done with fsnotify_remove_notify_event()
	276	*/
	277	struct fsnotify_event fsnotify_peek_notify_event(struct fsnotify_group group)
	278	{
	279	struct fsnotify_event *event;
	280	struct fsnotify_event_holder *holder;
	281
	282	BUG_ON(!mutex_is_locked(&group->notification_mutex));
	283
	284	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
	285	event = holder->event;
	286
	287	return event;
	288	}
	289
	290	/*
	291	* Called when a group is being torn down to clean up any outstanding
	292	* event notifications.
	293	*/
	294	void fsnotify_flush_notify(struct fsnotify_group *group)
	295	{
	296	struct fsnotify_event *event;
e4aff117	297	struct fsnotify_event_private_data *priv;
a2d8bc6c EP	298
	299	mutex_lock(&group->notification_mutex);
	300	while (!fsnotify_notify_queue_is_empty(group)) {
	301	event = fsnotify_remove_notify_event(group);
e4aff117 EP	302	/* if they don't implement free_event_priv they better not have attached any */
	303	if (group->ops->free_event_priv) {
	304	spin_lock(&event->lock);
	305	priv = fsnotify_remove_priv_from_event(group, event);
	306	spin_unlock(&event->lock);
	307	if (priv)
	308	group->ops->free_event_priv(priv);
	309	}
a2d8bc6c EP	310	fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
	311	}
	312	mutex_unlock(&group->notification_mutex);
	313	}
	314
	315	static void initialize_event(struct fsnotify_event *event)
	316	{
a2d8bc6c	317	INIT_LIST_HEAD(&event->holder.event_list);
90586523 EP	318	atomic_set(&event->refcnt, 1);
	319
	320	spin_lock_init(&event->lock);
	321
a2d8bc6c	322	event->data_type = FSNOTIFY_EVENT_NONE;
90586523	323
e4aff117	324	INIT_LIST_HEAD(&event->private_data_list);
a2d8bc6c EP	325	}
	326
	327	/*
	328	* fsnotify_create_event - Allocate a new event which will be sent to each
	329	* group's handle_event function if the group was interested in this
	330	* particular event.
	331	*
	332	* @to_tell the inode which is supposed to receive the event (sometimes a
	333	* parent of the inode to which the event happened.
	334	* @mask what actually happened.
	335	* @data pointer to the object which was actually affected
	336	* @data_type flag indication if the data is a file, path, inode, nothing...
62ffe5df	337	* @name the filename, if available
a2d8bc6c	338	*/
47882c6f	339	struct fsnotify_event fsnotify_create_event(struct inode to_tell, __u32 mask, void *data,
f44aebcc EP	340	int data_type, const char *name, u32 cookie,
f44aebcc EP	341	gfp_t gfp)
a2d8bc6c EP	342	{
	343	struct fsnotify_event *event;
	344
6f3a539e	345	event = kmem_cache_zalloc(fsnotify_event_cachep, gfp);
a2d8bc6c EP	346	if (!event)
	347	return NULL;
	348
	349	initialize_event(event);
62ffe5df EP	350
62ffe5df EP	351	if (name) {
f44aebcc	352	event->file_name = kstrdup(name, gfp);
62ffe5df EP	353	if (!event->file_name) {
	354	kmem_cache_free(fsnotify_event_cachep, event);
	355	return NULL;
	356	}
	357	event->name_len = strlen(event->file_name);
	358	}
47882c6f EP	359
47882c6f EP	360	event->sync_cookie = cookie;
90586523 EP	361	event->to_tell = to_tell;
	362
	363	switch (data_type) {
	364	case FSNOTIFY_EVENT_FILE: {
	365	struct file *file = data;
	366	struct path *path = &file->f_path;
	367	event->path.dentry = path->dentry;
	368	event->path.mnt = path->mnt;
	369	path_get(&event->path);
	370	event->data_type = FSNOTIFY_EVENT_PATH;
	371	break;
	372	}
	373	case FSNOTIFY_EVENT_PATH: {
	374	struct path *path = data;
	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_INODE:
	382	event->inode = data;
	383	event->data_type = FSNOTIFY_EVENT_INODE;
	384	break;
	385	case FSNOTIFY_EVENT_NONE:
	386	event->inode = NULL;
	387	event->path.dentry = NULL;
	388	event->path.mnt = NULL;
	389	break;
	390	default:
	391	BUG();
	392	}
	393
	394	event->mask = mask;
	395
	396	return event;
	397	}
	398
	399	__init int fsnotify_notification_init(void)
	400	{
	401	fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
a2d8bc6c EP	402	fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);
a2d8bc6c EP	403
b4277d3d EP	404	q_overflow_event = fsnotify_create_event(NULL, FS_Q_OVERFLOW, NULL,
	405	FSNOTIFY_EVENT_NONE, NULL, 0,
	406	GFP_KERNEL);
	407	if (!q_overflow_event)
	408	panic("unable to allocate fsnotify q_overflow_event\n");
90586523 EP	409
	410	return 0;
	411	}
	412	subsys_initcall(fsnotify_notification_init);
	413