[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)) {
		pr_debug("%s: event=%p\n", __func__, event);

		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 *,
					   void **arg),
			      void **arg)
{
	struct fsnotify_event_holder *holder = NULL;
	struct list_head *list = &group->notification_list;
	int rc = 0;

	pr_debug("%s: group=%p event=%p priv=%p\n", __func__, group, event, priv);

	/*
	 * 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, arg);
		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));

	pr_debug("%s: group=%p\n", __func__, group);

	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,
	};

	pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, new_event);

	/*
	 * 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;

	pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, event);

	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 unsigned char *name,
					     u32 cookie, gfp_t gfp)
{
	struct fsnotify_event *event;

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

	pr_debug("%s: event=%p to_tell=%p mask=%x data=%p data_type=%d\n",
		 __func__, event, to_tell, mask, data, data_type);

	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)) {
5ba08e2e EP	90	pr_debug("%s: event=%p\n", __func__, event);
5ba08e2e EP	91
90586523 EP	92	if (event->data_type == FSNOTIFY_EVENT_PATH)
	93	path_put(&event->path);
	94
e4aff117 EP	95	BUG_ON(!list_empty(&event->private_data_list));
e4aff117 EP	96
62ffe5df	97	kfree(event->file_name);
32c32632	98	put_pid(event->tgid);
90586523 EP	99	kmem_cache_free(fsnotify_event_cachep, event);
	100	}
	101	}
	102
a2d8bc6c EP	103	struct fsnotify_event_holder *fsnotify_alloc_event_holder(void)
	104	{
	105	return kmem_cache_alloc(fsnotify_event_holder_cachep, GFP_KERNEL);
	106	}
	107
	108	void fsnotify_destroy_event_holder(struct fsnotify_event_holder *holder)
	109	{
74766bbf EP	110	if (holder)
74766bbf EP	111	kmem_cache_free(fsnotify_event_holder_cachep, holder);
a2d8bc6c EP	112	}
	113
	114	/*
e4aff117 EP	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)
	117	*/
	118	struct fsnotify_event_private_data fsnotify_remove_priv_from_event(struct fsnotify_group group, struct fsnotify_event *event)
	119	{
	120	struct fsnotify_event_private_data *lpriv;
	121	struct fsnotify_event_private_data *priv = NULL;
	122
	123	assert_spin_locked(&event->lock);
	124
	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;
	130	}
	131	}
	132	return priv;
	133	}
	134
90586523	135	/*
a2d8bc6c EP	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.
90586523	139	*/
e4aff117	140	int fsnotify_add_notify_event(struct fsnotify_group group, struct fsnotify_event event,
74766bbf	141	struct fsnotify_event_private_data *priv,
6e5f77b3 EP	142	int (merge)(struct list_head ,
	143	struct fsnotify_event *,
	144	void **arg),
	145	void **arg)
a2d8bc6c EP	146	{
	147	struct fsnotify_event_holder *holder = NULL;
	148	struct list_head *list = &group->notification_list;
74766bbf	149	int rc = 0;
e4aff117	150
5ba08e2e EP	151	pr_debug("%s: group=%p event=%p priv=%p\n", __func__, group, event, priv);
5ba08e2e EP	152
a2d8bc6c EP	153	/*
	154	* There is one fsnotify_event_holder embedded inside each fsnotify_event.
	155	* Check if we expect to be able to use that holder. If not alloc a new
	156	* holder.
	157	* For the overflow event it's possible that something will use the in
	158	* event holder before we get the lock so we may need to jump back and
	159	* alloc a new holder, this can't happen for most events...
	160	*/
	161	if (!list_empty(&event->holder.event_list)) {
	162	alloc_holder:
	163	holder = fsnotify_alloc_event_holder();
	164	if (!holder)
	165	return -ENOMEM;
	166	}
	167
	168	mutex_lock(&group->notification_mutex);
	169
e4aff117	170	if (group->q_len >= group->max_events) {
b4277d3d	171	event = q_overflow_event;
74766bbf	172	rc = -EOVERFLOW;
e4aff117 EP	173	/* sorry, no private data on the overflow event */
	174	priv = NULL;
	175	}
a2d8bc6c	176
74766bbf EP	177	if (!list_empty(list) && merge) {
	178	int ret;
	179
6e5f77b3	180	ret = merge(list, event, arg);
74766bbf EP	181	if (ret) {
	182	mutex_unlock(&group->notification_mutex);
	183	if (holder != &event->holder)
	184	fsnotify_destroy_event_holder(holder);
	185	return ret;
	186	}
	187	}
	188
a2d8bc6c EP	189	spin_lock(&event->lock);
	190
	191	if (list_empty(&event->holder.event_list)) {
	192	if (unlikely(holder))
	193	fsnotify_destroy_event_holder(holder);
	194	holder = &event->holder;
	195	} else if (unlikely(!holder)) {
	196	/* between the time we checked above and got the lock the in
	197	* event holder was used, go back and get a new one */
	198	spin_unlock(&event->lock);
	199	mutex_unlock(&group->notification_mutex);
	200	goto alloc_holder;
	201	}
	202
a2d8bc6c EP	203	group->q_len++;
	204	holder->event = event;
	205
	206	fsnotify_get_event(event);
	207	list_add_tail(&holder->event_list, list);
e4aff117 EP	208	if (priv)
e4aff117 EP	209	list_add_tail(&priv->event_list, &event->private_data_list);
a2d8bc6c EP	210	spin_unlock(&event->lock);
	211	mutex_unlock(&group->notification_mutex);
	212
	213	wake_up(&group->notification_waitq);
74766bbf	214	return rc;
a2d8bc6c EP	215	}
	216
	217	/*
	218	* Remove and return the first event from the notification list. There is a
	219	* reference held on this event since it was on the list. It is the responsibility
	220	* of the caller to drop this reference.
	221	*/
	222	struct fsnotify_event fsnotify_remove_notify_event(struct fsnotify_group group)
90586523 EP	223	{
90586523 EP	224	struct fsnotify_event *event;
a2d8bc6c	225	struct fsnotify_event_holder *holder;
90586523	226
a2d8bc6c	227	BUG_ON(!mutex_is_locked(&group->notification_mutex));
90586523	228
5ba08e2e EP	229	pr_debug("%s: group=%p\n", __func__, group);
5ba08e2e EP	230
a2d8bc6c EP	231	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
	232
	233	event = holder->event;
	234
	235	spin_lock(&event->lock);
	236	holder->event = NULL;
	237	list_del_init(&holder->event_list);
	238	spin_unlock(&event->lock);
	239
	240	/* event == holder means we are referenced through the in event holder */
	241	if (holder != &event->holder)
	242	fsnotify_destroy_event_holder(holder);
	243
	244	group->q_len--;
	245
	246	return event;
	247	}
	248
	249	/*
	250	* This will not remove the event, that must be done with fsnotify_remove_notify_event()
	251	*/
	252	struct fsnotify_event fsnotify_peek_notify_event(struct fsnotify_group group)
	253	{
	254	struct fsnotify_event *event;
	255	struct fsnotify_event_holder *holder;
	256
	257	BUG_ON(!mutex_is_locked(&group->notification_mutex));
	258
	259	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
	260	event = holder->event;
	261
	262	return event;
	263	}
	264
	265	/*
	266	* Called when a group is being torn down to clean up any outstanding
	267	* event notifications.
	268	*/
	269	void fsnotify_flush_notify(struct fsnotify_group *group)
	270	{
	271	struct fsnotify_event *event;
e4aff117	272	struct fsnotify_event_private_data *priv;
a2d8bc6c EP	273
	274	mutex_lock(&group->notification_mutex);
	275	while (!fsnotify_notify_queue_is_empty(group)) {
	276	event = fsnotify_remove_notify_event(group);
e4aff117 EP	277	/* if they don't implement free_event_priv they better not have attached any */
	278	if (group->ops->free_event_priv) {
	279	spin_lock(&event->lock);
	280	priv = fsnotify_remove_priv_from_event(group, event);
	281	spin_unlock(&event->lock);
	282	if (priv)
	283	group->ops->free_event_priv(priv);
	284	}
a2d8bc6c EP	285	fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
	286	}
	287	mutex_unlock(&group->notification_mutex);
	288	}
	289
	290	static void initialize_event(struct fsnotify_event *event)
	291	{
a2d8bc6c	292	INIT_LIST_HEAD(&event->holder.event_list);
90586523 EP	293	atomic_set(&event->refcnt, 1);
	294
	295	spin_lock_init(&event->lock);
	296
e4aff117	297	INIT_LIST_HEAD(&event->private_data_list);
a2d8bc6c EP	298	}
a2d8bc6c EP	299
1201a536 EP	300	/*
1201a536 EP	301	* Caller damn well better be holding whatever mutex is protecting the
cac69dad EP	302	* old_holder->event_list and the new_event must be a clean event which
cac69dad EP	303	* cannot be found anywhere else in the kernel.
1201a536 EP	304	*/
	305	int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
	306	struct fsnotify_event *new_event)
	307	{
	308	struct fsnotify_event *old_event = old_holder->event;
cac69dad EP	309	struct fsnotify_event_holder *new_holder = &new_event->holder;
	310
	311	enum event_spinlock_class {
	312	SPINLOCK_OLD,
	313	SPINLOCK_NEW,
	314	};
1201a536	315
5ba08e2e EP	316	pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, new_event);
5ba08e2e EP	317
1201a536	318	/*
cac69dad EP	319	* if the new_event's embedded holder is in use someone
cac69dad EP	320	* screwed up and didn't give us a clean new event.
1201a536	321	*/
cac69dad	322	BUG_ON(!list_empty(&new_holder->event_list));
1201a536	323
cac69dad EP	324	spin_lock_nested(&old_event->lock, SPINLOCK_OLD);
cac69dad EP	325	spin_lock_nested(&new_event->lock, SPINLOCK_NEW);
1201a536 EP	326
	327	new_holder->event = new_event;
	328	list_replace_init(&old_holder->event_list, &new_holder->event_list);
	329
	330	spin_unlock(&new_event->lock);
	331	spin_unlock(&old_event->lock);
	332
	333	/* event == holder means we are referenced through the in event holder */
	334	if (old_holder != &old_event->holder)
	335	fsnotify_destroy_event_holder(old_holder);
	336
	337	fsnotify_get_event(new_event); /* on the list take reference */
	338	fsnotify_put_event(old_event); /* off the list, drop reference */
	339
	340	return 0;
	341	}
	342
b4e4e140 EP	343	struct fsnotify_event fsnotify_clone_event(struct fsnotify_event old_event)
	344	{
	345	struct fsnotify_event *event;
	346
	347	event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL);
	348	if (!event)
	349	return NULL;
	350
5ba08e2e EP	351	pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, event);
5ba08e2e EP	352
b4e4e140 EP	353	memcpy(event, old_event, sizeof(*event));
	354	initialize_event(event);
	355
	356	if (event->name_len) {
	357	event->file_name = kstrdup(old_event->file_name, GFP_KERNEL);
	358	if (!event->file_name) {
	359	kmem_cache_free(fsnotify_event_cachep, event);
	360	return NULL;
	361	}
	362	}
32c32632	363	event->tgid = get_pid(old_event->tgid);
b4e4e140 EP	364	if (event->data_type == FSNOTIFY_EVENT_PATH)
	365	path_get(&event->path);
	366
	367	return event;
	368	}
	369
a2d8bc6c EP	370	/*
	371	* fsnotify_create_event - Allocate a new event which will be sent to each
	372	* group's handle_event function if the group was interested in this
	373	* particular event.
	374	*
	375	* @to_tell the inode which is supposed to receive the event (sometimes a
	376	* parent of the inode to which the event happened.
	377	* @mask what actually happened.
	378	* @data pointer to the object which was actually affected
	379	* @data_type flag indication if the data is a file, path, inode, nothing...
62ffe5df	380	* @name the filename, if available
a2d8bc6c	381	*/
47882c6f	382	struct fsnotify_event fsnotify_create_event(struct inode to_tell, __u32 mask, void *data,
59b0df21 EP	383	int data_type, const unsigned char *name,
59b0df21 EP	384	u32 cookie, gfp_t gfp)
a2d8bc6c EP	385	{
	386	struct fsnotify_event *event;
	387
6f3a539e	388	event = kmem_cache_zalloc(fsnotify_event_cachep, gfp);
a2d8bc6c EP	389	if (!event)
	390	return NULL;
	391
5ba08e2e EP	392	pr_debug("%s: event=%p to_tell=%p mask=%x data=%p data_type=%d\n",
	393	__func__, event, to_tell, mask, data, data_type);
	394
a2d8bc6c	395	initialize_event(event);
62ffe5df EP	396
62ffe5df EP	397	if (name) {
f44aebcc	398	event->file_name = kstrdup(name, gfp);
62ffe5df EP	399	if (!event->file_name) {
	400	kmem_cache_free(fsnotify_event_cachep, event);
	401	return NULL;
	402	}
	403	event->name_len = strlen(event->file_name);
	404	}
47882c6f	405
32c32632	406	event->tgid = get_pid(task_tgid(current));
47882c6f	407	event->sync_cookie = cookie;
90586523	408	event->to_tell = to_tell;
b4e4e140	409	event->data_type = data_type;
90586523 EP	410
90586523 EP	411	switch (data_type) {
90586523 EP	412	case FSNOTIFY_EVENT_PATH: {
	413	struct path *path = data;
	414	event->path.dentry = path->dentry;
	415	event->path.mnt = path->mnt;
	416	path_get(&event->path);
90586523 EP	417	break;
	418	}
	419	case FSNOTIFY_EVENT_INODE:
	420	event->inode = data;
90586523 EP	421	break;
	422	case FSNOTIFY_EVENT_NONE:
	423	event->inode = NULL;
	424	event->path.dentry = NULL;
	425	event->path.mnt = NULL;
	426	break;
	427	default:
	428	BUG();
	429	}
	430
	431	event->mask = mask;
	432
	433	return event;
	434	}
	435
	436	__init int fsnotify_notification_init(void)
	437	{
	438	fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
a2d8bc6c EP	439	fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);
a2d8bc6c EP	440
b4277d3d EP	441	q_overflow_event = fsnotify_create_event(NULL, FS_Q_OVERFLOW, NULL,
	442	FSNOTIFY_EVENT_NONE, NULL, 0,
	443	GFP_KERNEL);
	444	if (!q_overflow_event)
	445	panic("unable to allocate fsnotify q_overflow_event\n");
90586523 EP	446
	447	return 0;
	448	}
	449	subsys_initcall(fsnotify_notification_init);
	450