[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);
		put_pid(event->tgid);
		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)
{
	if (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;
}

/*
 * 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,
			      int (*merge)(struct list_head *, struct fsnotify_event *))
{
	struct fsnotify_event_holder *holder = NULL;
	struct list_head *list = &group->notification_list;
	int rc = 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;
		rc = -EOVERFLOW;
		/* sorry, no private data on the overflow event */
		priv = NULL;
	}

	if (!list_empty(list) && merge) {
		int ret;

		ret = merge(list, event);
		if (ret) {
			mutex_unlock(&group->notification_mutex);
			if (holder != &event->holder)
				fsnotify_destroy_event_holder(holder);
			return ret;
		}
	}

	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;
	}

	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 rc;
}

/*
 * 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);

	INIT_LIST_HEAD(&event->private_data_list);
}

/*
 * Caller damn well better be holding whatever mutex is protecting the
 * old_holder->event_list and the new_event must be a clean event which
 * cannot be found anywhere else in the kernel.
 */
int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
			   struct fsnotify_event *new_event)
{
	struct fsnotify_event *old_event = old_holder->event;
	struct fsnotify_event_holder *new_holder = &new_event->holder;

	enum event_spinlock_class {
		SPINLOCK_OLD,
		SPINLOCK_NEW,
	};

	/*
	 * if the new_event's embedded holder is in use someone
	 * screwed up and didn't give us a clean new event.
	 */
	BUG_ON(!list_empty(&new_holder->event_list));

	spin_lock_nested(&old_event->lock, SPINLOCK_OLD);
	spin_lock_nested(&new_event->lock, SPINLOCK_NEW);

	new_holder->event = new_event;
	list_replace_init(&old_holder->event_list, &new_holder->event_list);

	spin_unlock(&new_event->lock);
	spin_unlock(&old_event->lock);

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

	fsnotify_get_event(new_event); /* on the list take reference */
	fsnotify_put_event(old_event); /* off the list, drop reference */

	return 0;
}

struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event)
{
	struct fsnotify_event *event;

	event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL);
	if (!event)
		return NULL;

	memcpy(event, old_event, sizeof(*event));
	initialize_event(event);

	if (event->name_len) {
		event->file_name = kstrdup(old_event->file_name, GFP_KERNEL);
		if (!event->file_name) {
			kmem_cache_free(fsnotify_event_cachep, event);
			return NULL;
		}
	}
	event->tgid = get_pid(old_event->tgid);
	if (event->data_type == FSNOTIFY_EVENT_PATH)
		path_get(&event->path);

	return event;
}

/*
 * 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->tgid = get_pid(task_tgid(current));
	event->sync_cookie = cookie;
	event->to_tell = to_tell;
	event->data_type = data_type;

	switch (data_type) {
	case FSNOTIFY_EVENT_PATH: {
		struct path *path = data;
		event->path.dentry = path->dentry;
		event->path.mnt = path->mnt;
		path_get(&event->path);
		break;
	}
	case FSNOTIFY_EVENT_INODE:
		event->inode = data;
		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);
32c32632	96	put_pid(event->tgid);
90586523 EP	97	kmem_cache_free(fsnotify_event_cachep, event);
	98	}
	99	}
	100
a2d8bc6c EP	101	struct fsnotify_event_holder *fsnotify_alloc_event_holder(void)
	102	{
	103	return kmem_cache_alloc(fsnotify_event_holder_cachep, GFP_KERNEL);
	104	}
	105
	106	void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder)
	107	{
74766bbf EP	108	if (holder)
74766bbf EP	109	kmem_cache_free(fsnotify_event_holder_cachep, holder);
a2d8bc6c EP	110	}
	111
	112	/*
e4aff117 EP	113	* Find the private data that the group previously attached to this event when
	114	* the group added the event to the notification queue (fsnotify_add_notify_event)
	115	*/
	116	struct fsnotify_event_private_data fsnotify_remove_priv_from_event(struct fsnotify_group group, struct fsnotify_event *event)
	117	{
	118	struct fsnotify_event_private_data *lpriv;
	119	struct fsnotify_event_private_data *priv = NULL;
	120
	121	assert_spin_locked(&event->lock);
	122
	123	list_for_each_entry(lpriv, &event->private_data_list, event_list) {
	124	if (lpriv->group == group) {
	125	priv = lpriv;
	126	list_del(&priv->event_list);
	127	break;
	128	}
	129	}
	130	return priv;
	131	}
	132
90586523	133	/*
a2d8bc6c EP	134	* Add an event to the group notification queue. The group can later pull this
	135	* event off the queue to deal with. If the event is successfully added to the
	136	* group's notification queue, a reference is taken on event.
90586523	137	*/
e4aff117	138	int fsnotify_add_notify_event(struct fsnotify_group group, struct fsnotify_event event,
74766bbf EP	139	struct fsnotify_event_private_data *priv,
74766bbf EP	140	int (merge)(struct list_head , struct fsnotify_event *))
a2d8bc6c EP	141	{
	142	struct fsnotify_event_holder *holder = NULL;
	143	struct list_head *list = &group->notification_list;
74766bbf	144	int rc = 0;
e4aff117	145
a2d8bc6c EP	146	/*
	147	* There is one fsnotify_event_holder embedded inside each fsnotify_event.
	148	* Check if we expect to be able to use that holder. If not alloc a new
	149	* holder.
	150	* For the overflow event it's possible that something will use the in
	151	* event holder before we get the lock so we may need to jump back and
	152	* alloc a new holder, this can't happen for most events...
	153	*/
	154	if (!list_empty(&event->holder.event_list)) {
	155	alloc_holder:
	156	holder = fsnotify_alloc_event_holder();
	157	if (!holder)
	158	return -ENOMEM;
	159	}
	160
	161	mutex_lock(&group->notification_mutex);
	162
e4aff117	163	if (group->q_len >= group->max_events) {
b4277d3d	164	event = q_overflow_event;
74766bbf	165	rc = -EOVERFLOW;
e4aff117 EP	166	/* sorry, no private data on the overflow event */
	167	priv = NULL;
	168	}
a2d8bc6c	169
74766bbf EP	170	if (!list_empty(list) && merge) {
	171	int ret;
	172
	173	ret = merge(list, event);
	174	if (ret) {
	175	mutex_unlock(&group->notification_mutex);
	176	if (holder != &event->holder)
	177	fsnotify_destroy_event_holder(holder);
	178	return ret;
	179	}
	180	}
	181
a2d8bc6c EP	182	spin_lock(&event->lock);
	183
	184	if (list_empty(&event->holder.event_list)) {
	185	if (unlikely(holder))
	186	fsnotify_destroy_event_holder(holder);
	187	holder = &event->holder;
	188	} else if (unlikely(!holder)) {
	189	/* between the time we checked above and got the lock the in
	190	* event holder was used, go back and get a new one */
	191	spin_unlock(&event->lock);
	192	mutex_unlock(&group->notification_mutex);
	193	goto alloc_holder;
	194	}
	195
a2d8bc6c EP	196	group->q_len++;
	197	holder->event = event;
	198
	199	fsnotify_get_event(event);
	200	list_add_tail(&holder->event_list, list);
e4aff117 EP	201	if (priv)
e4aff117 EP	202	list_add_tail(&priv->event_list, &event->private_data_list);
a2d8bc6c EP	203	spin_unlock(&event->lock);
	204	mutex_unlock(&group->notification_mutex);
	205
	206	wake_up(&group->notification_waitq);
74766bbf	207	return rc;
a2d8bc6c EP	208	}
	209
	210	/*
	211	* Remove and return the first event from the notification list. There is a
	212	* reference held on this event since it was on the list. It is the responsibility
	213	* of the caller to drop this reference.
	214	*/
	215	struct fsnotify_event fsnotify_remove_notify_event(struct fsnotify_group group)
90586523 EP	216	{
90586523 EP	217	struct fsnotify_event *event;
a2d8bc6c	218	struct fsnotify_event_holder *holder;
90586523	219
a2d8bc6c	220	BUG_ON(!mutex_is_locked(&group->notification_mutex));
90586523	221
a2d8bc6c EP	222	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
	223
	224	event = holder->event;
	225
	226	spin_lock(&event->lock);
	227	holder->event = NULL;
	228	list_del_init(&holder->event_list);
	229	spin_unlock(&event->lock);
	230
	231	/* event == holder means we are referenced through the in event holder */
	232	if (holder != &event->holder)
	233	fsnotify_destroy_event_holder(holder);
	234
	235	group->q_len--;
	236
	237	return event;
	238	}
	239
	240	/*
	241	* This will not remove the event, that must be done with fsnotify_remove_notify_event()
	242	*/
	243	struct fsnotify_event fsnotify_peek_notify_event(struct fsnotify_group group)
	244	{
	245	struct fsnotify_event *event;
	246	struct fsnotify_event_holder *holder;
	247
	248	BUG_ON(!mutex_is_locked(&group->notification_mutex));
	249
	250	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
	251	event = holder->event;
	252
	253	return event;
	254	}
	255
	256	/*
	257	* Called when a group is being torn down to clean up any outstanding
	258	* event notifications.
	259	*/
	260	void fsnotify_flush_notify(struct fsnotify_group *group)
	261	{
	262	struct fsnotify_event *event;
e4aff117	263	struct fsnotify_event_private_data *priv;
a2d8bc6c EP	264
	265	mutex_lock(&group->notification_mutex);
	266	while (!fsnotify_notify_queue_is_empty(group)) {
	267	event = fsnotify_remove_notify_event(group);
e4aff117 EP	268	/* if they don't implement free_event_priv they better not have attached any */
	269	if (group->ops->free_event_priv) {
	270	spin_lock(&event->lock);
	271	priv = fsnotify_remove_priv_from_event(group, event);
	272	spin_unlock(&event->lock);
	273	if (priv)
	274	group->ops->free_event_priv(priv);
	275	}
a2d8bc6c EP	276	fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
	277	}
	278	mutex_unlock(&group->notification_mutex);
	279	}
	280
	281	static void initialize_event(struct fsnotify_event *event)
	282	{
a2d8bc6c	283	INIT_LIST_HEAD(&event->holder.event_list);
90586523 EP	284	atomic_set(&event->refcnt, 1);
	285
	286	spin_lock_init(&event->lock);
	287
e4aff117	288	INIT_LIST_HEAD(&event->private_data_list);
a2d8bc6c EP	289	}
a2d8bc6c EP	290
1201a536 EP	291	/*
1201a536 EP	292	* Caller damn well better be holding whatever mutex is protecting the
cac69dad EP	293	* old_holder->event_list and the new_event must be a clean event which
cac69dad EP	294	* cannot be found anywhere else in the kernel.
1201a536 EP	295	*/
	296	int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
	297	struct fsnotify_event *new_event)
	298	{
	299	struct fsnotify_event *old_event = old_holder->event;
cac69dad EP	300	struct fsnotify_event_holder *new_holder = &new_event->holder;
	301
	302	enum event_spinlock_class {
	303	SPINLOCK_OLD,
	304	SPINLOCK_NEW,
	305	};
1201a536 EP	306
1201a536 EP	307	/*
cac69dad EP	308	* if the new_event's embedded holder is in use someone
cac69dad EP	309	* screwed up and didn't give us a clean new event.
1201a536	310	*/
cac69dad	311	BUG_ON(!list_empty(&new_holder->event_list));
1201a536	312
cac69dad EP	313	spin_lock_nested(&old_event->lock, SPINLOCK_OLD);
cac69dad EP	314	spin_lock_nested(&new_event->lock, SPINLOCK_NEW);
1201a536 EP	315
	316	new_holder->event = new_event;
	317	list_replace_init(&old_holder->event_list, &new_holder->event_list);
	318
	319	spin_unlock(&new_event->lock);
	320	spin_unlock(&old_event->lock);
	321
	322	/* event == holder means we are referenced through the in event holder */
	323	if (old_holder != &old_event->holder)
	324	fsnotify_destroy_event_holder(old_holder);
	325
	326	fsnotify_get_event(new_event); /* on the list take reference */
	327	fsnotify_put_event(old_event); /* off the list, drop reference */
	328
	329	return 0;
	330	}
	331
b4e4e140 EP	332	struct fsnotify_event fsnotify_clone_event(struct fsnotify_event old_event)
	333	{
	334	struct fsnotify_event *event;
	335
	336	event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL);
	337	if (!event)
	338	return NULL;
	339
	340	memcpy(event, old_event, sizeof(*event));
	341	initialize_event(event);
	342
	343	if (event->name_len) {
	344	event->file_name = kstrdup(old_event->file_name, GFP_KERNEL);
	345	if (!event->file_name) {
	346	kmem_cache_free(fsnotify_event_cachep, event);
	347	return NULL;
	348	}
	349	}
32c32632	350	event->tgid = get_pid(old_event->tgid);
b4e4e140 EP	351	if (event->data_type == FSNOTIFY_EVENT_PATH)
	352	path_get(&event->path);
	353
	354	return event;
	355	}
	356
a2d8bc6c EP	357	/*
	358	* fsnotify_create_event - Allocate a new event which will be sent to each
	359	* group's handle_event function if the group was interested in this
	360	* particular event.
	361	*
	362	* @to_tell the inode which is supposed to receive the event (sometimes a
	363	* parent of the inode to which the event happened.
	364	* @mask what actually happened.
	365	* @data pointer to the object which was actually affected
	366	* @data_type flag indication if the data is a file, path, inode, nothing...
62ffe5df	367	* @name the filename, if available
a2d8bc6c	368	*/
47882c6f	369	struct fsnotify_event fsnotify_create_event(struct inode to_tell, __u32 mask, void *data,
f44aebcc EP	370	int data_type, const char *name, u32 cookie,
f44aebcc EP	371	gfp_t gfp)
a2d8bc6c EP	372	{
	373	struct fsnotify_event *event;
	374
6f3a539e	375	event = kmem_cache_zalloc(fsnotify_event_cachep, gfp);
a2d8bc6c EP	376	if (!event)
	377	return NULL;
	378
	379	initialize_event(event);
62ffe5df EP	380
62ffe5df EP	381	if (name) {
f44aebcc	382	event->file_name = kstrdup(name, gfp);
62ffe5df EP	383	if (!event->file_name) {
	384	kmem_cache_free(fsnotify_event_cachep, event);
	385	return NULL;
	386	}
	387	event->name_len = strlen(event->file_name);
	388	}
47882c6f	389
32c32632	390	event->tgid = get_pid(task_tgid(current));
47882c6f	391	event->sync_cookie = cookie;
90586523	392	event->to_tell = to_tell;
b4e4e140	393	event->data_type = data_type;
90586523 EP	394
90586523 EP	395	switch (data_type) {
90586523 EP	396	case FSNOTIFY_EVENT_PATH: {
	397	struct path *path = data;
	398	event->path.dentry = path->dentry;
	399	event->path.mnt = path->mnt;
	400	path_get(&event->path);
90586523 EP	401	break;
	402	}
	403	case FSNOTIFY_EVENT_INODE:
	404	event->inode = data;
90586523 EP	405	break;
	406	case FSNOTIFY_EVENT_NONE:
	407	event->inode = NULL;
	408	event->path.dentry = NULL;
	409	event->path.mnt = NULL;
	410	break;
	411	default:
	412	BUG();
	413	}
	414
	415	event->mask = mask;
	416
	417	return event;
	418	}
	419
	420	__init int fsnotify_notification_init(void)
	421	{
	422	fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
a2d8bc6c EP	423	fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);
a2d8bc6c EP	424
b4277d3d EP	425	q_overflow_event = fsnotify_create_event(NULL, FS_Q_OVERFLOW, NULL,
	426	FSNOTIFY_EVENT_NONE, NULL, 0,
	427	GFP_KERNEL);
	428	if (!q_overflow_event)
	429	panic("unable to allocate fsnotify q_overflow_event\n");
90586523 EP	430
	431	return 0;
	432	}
	433	subsys_initcall(fsnotify_notification_init);
	434