[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.
 */
struct fsnotify_event *fsnotify_add_notify_event(struct fsnotify_group *group, struct fsnotify_event *event,
						 struct fsnotify_event_private_data *priv,
						 struct fsnotify_event *(*merge)(struct list_head *,
										 struct fsnotify_event *))
{
	struct fsnotify_event *return_event = NULL;
	struct fsnotify_event_holder *holder = NULL;
	struct list_head *list = &group->notification_list;

	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 ERR_PTR(-ENOMEM);
	}

	mutex_lock(&group->notification_mutex);

	if (group->q_len >= group->max_events) {
		event = q_overflow_event;

		/*
		 * we need to return the overflow event
		 * which means we need a ref
		 */
		fsnotify_get_event(event);
		return_event = event;

		/* sorry, no private data on the overflow event */
		priv = NULL;
	}

	if (!list_empty(list) && merge) {
		struct fsnotify_event *tmp;

		tmp = merge(list, event);
		if (tmp) {
			mutex_unlock(&group->notification_mutex);

			if (return_event)
				fsnotify_put_event(return_event);
			if (holder != &event->holder)
				fsnotify_destroy_event_holder(holder);
			return tmp;
		}
	}

	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);

		if (return_event) {
			fsnotify_put_event(return_event);
			return_event = NULL;
		}

		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 return_event;
}

/*
 * 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
2069601b LT	92	if (event->data_type == FSNOTIFY_EVENT_PATH)
2069601b LT	93	path_put(&event->path);
90586523	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	*/
f70ab54c EP	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 *))
a2d8bc6c	144	{
f70ab54c	145	struct fsnotify_event *return_event = NULL;
a2d8bc6c EP	146	struct fsnotify_event_holder *holder = NULL;
a2d8bc6c EP	147	struct list_head *list = &group->notification_list;
e4aff117	148
5ba08e2e EP	149	pr_debug("%s: group=%p event=%p priv=%p\n", __func__, group, event, priv);
5ba08e2e EP	150
a2d8bc6c EP	151	/*
	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...
	158	*/
	159	if (!list_empty(&event->holder.event_list)) {
	160	alloc_holder:
	161	holder = fsnotify_alloc_event_holder();
	162	if (!holder)
f70ab54c	163	return ERR_PTR(-ENOMEM);
a2d8bc6c EP	164	}
	165
	166	mutex_lock(&group->notification_mutex);
	167
e4aff117	168	if (group->q_len >= group->max_events) {
b4277d3d	169	event = q_overflow_event;
f70ab54c EP	170
	171	/*
	172	* we need to return the overflow event
	173	* which means we need a ref
	174	*/
	175	fsnotify_get_event(event);
	176	return_event = event;
	177
e4aff117 EP	178	/* sorry, no private data on the overflow event */
	179	priv = NULL;
	180	}
a2d8bc6c	181
74766bbf	182	if (!list_empty(list) && merge) {
f70ab54c	183	struct fsnotify_event *tmp;
74766bbf	184
f70ab54c EP	185	tmp = merge(list, event);
f70ab54c EP	186	if (tmp) {
74766bbf	187	mutex_unlock(&group->notification_mutex);
f70ab54c EP	188
	189	if (return_event)
	190	fsnotify_put_event(return_event);
74766bbf EP	191	if (holder != &event->holder)
74766bbf EP	192	fsnotify_destroy_event_holder(holder);
f70ab54c	193	return tmp;
74766bbf EP	194	}
	195	}
	196
a2d8bc6c EP	197	spin_lock(&event->lock);
	198
	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);
f70ab54c EP	208
	209	if (return_event) {
	210	fsnotify_put_event(return_event);
	211	return_event = NULL;
	212	}
	213
a2d8bc6c EP	214	goto alloc_holder;
	215	}
	216
a2d8bc6c EP	217	group->q_len++;
	218	holder->event = event;
	219
	220	fsnotify_get_event(event);
	221	list_add_tail(&holder->event_list, list);
e4aff117 EP	222	if (priv)
e4aff117 EP	223	list_add_tail(&priv->event_list, &event->private_data_list);
a2d8bc6c EP	224	spin_unlock(&event->lock);
	225	mutex_unlock(&group->notification_mutex);
	226
	227	wake_up(&group->notification_waitq);
f70ab54c	228	return return_event;
a2d8bc6c EP	229	}
	230
	231	/*
	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.
	235	*/
	236	struct fsnotify_event fsnotify_remove_notify_event(struct fsnotify_group group)
90586523 EP	237	{
90586523 EP	238	struct fsnotify_event *event;
a2d8bc6c	239	struct fsnotify_event_holder *holder;
90586523	240
a2d8bc6c	241	BUG_ON(!mutex_is_locked(&group->notification_mutex));
90586523	242
5ba08e2e EP	243	pr_debug("%s: group=%p\n", __func__, group);
5ba08e2e EP	244
a2d8bc6c EP	245	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
	246
	247	event = holder->event;
	248
	249	spin_lock(&event->lock);
	250	holder->event = NULL;
	251	list_del_init(&holder->event_list);
	252	spin_unlock(&event->lock);
	253
	254	/* event == holder means we are referenced through the in event holder */
	255	if (holder != &event->holder)
	256	fsnotify_destroy_event_holder(holder);
	257
	258	group->q_len--;
	259
	260	return event;
	261	}
	262
	263	/*
	264	* This will not remove the event, that must be done with fsnotify_remove_notify_event()
	265	*/
	266	struct fsnotify_event fsnotify_peek_notify_event(struct fsnotify_group group)
	267	{
	268	struct fsnotify_event *event;
	269	struct fsnotify_event_holder *holder;
	270
	271	BUG_ON(!mutex_is_locked(&group->notification_mutex));
	272
	273	holder = list_first_entry(&group->notification_list, struct fsnotify_event_holder, event_list);
	274	event = holder->event;
	275
	276	return event;
	277	}
	278
	279	/*
	280	* Called when a group is being torn down to clean up any outstanding
	281	* event notifications.
	282	*/
	283	void fsnotify_flush_notify(struct fsnotify_group *group)
	284	{
	285	struct fsnotify_event *event;
e4aff117	286	struct fsnotify_event_private_data *priv;
a2d8bc6c EP	287
	288	mutex_lock(&group->notification_mutex);
	289	while (!fsnotify_notify_queue_is_empty(group)) {
	290	event = fsnotify_remove_notify_event(group);
e4aff117 EP	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);
	298	}
a2d8bc6c EP	299	fsnotify_put_event(event); /* matches fsnotify_add_notify_event */
	300	}
	301	mutex_unlock(&group->notification_mutex);
	302	}
	303
	304	static void initialize_event(struct fsnotify_event *event)
	305	{
a2d8bc6c	306	INIT_LIST_HEAD(&event->holder.event_list);
90586523 EP	307	atomic_set(&event->refcnt, 1);
	308
	309	spin_lock_init(&event->lock);
	310
e4aff117	311	INIT_LIST_HEAD(&event->private_data_list);
a2d8bc6c EP	312	}
a2d8bc6c EP	313
1201a536 EP	314	/*
1201a536 EP	315	* Caller damn well better be holding whatever mutex is protecting the
cac69dad EP	316	* old_holder->event_list and the new_event must be a clean event which
cac69dad EP	317	* cannot be found anywhere else in the kernel.
1201a536 EP	318	*/
	319	int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
	320	struct fsnotify_event *new_event)
	321	{
	322	struct fsnotify_event *old_event = old_holder->event;
cac69dad EP	323	struct fsnotify_event_holder *new_holder = &new_event->holder;
	324
	325	enum event_spinlock_class {
	326	SPINLOCK_OLD,
	327	SPINLOCK_NEW,
	328	};
1201a536	329
5ba08e2e EP	330	pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, new_event);
5ba08e2e EP	331
1201a536	332	/*
cac69dad EP	333	* if the new_event's embedded holder is in use someone
cac69dad EP	334	* screwed up and didn't give us a clean new event.
1201a536	335	*/
cac69dad	336	BUG_ON(!list_empty(&new_holder->event_list));
1201a536	337
cac69dad EP	338	spin_lock_nested(&old_event->lock, SPINLOCK_OLD);
cac69dad EP	339	spin_lock_nested(&new_event->lock, SPINLOCK_NEW);
1201a536 EP	340
	341	new_holder->event = new_event;
	342	list_replace_init(&old_holder->event_list, &new_holder->event_list);
	343
	344	spin_unlock(&new_event->lock);
	345	spin_unlock(&old_event->lock);
	346
	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);
	350
	351	fsnotify_get_event(new_event); /* on the list take reference */
	352	fsnotify_put_event(old_event); /* off the list, drop reference */
	353
	354	return 0;
	355	}
	356
b4e4e140 EP	357	struct fsnotify_event fsnotify_clone_event(struct fsnotify_event old_event)
	358	{
	359	struct fsnotify_event *event;
	360
	361	event = kmem_cache_alloc(fsnotify_event_cachep, GFP_KERNEL);
	362	if (!event)
	363	return NULL;
	364
5ba08e2e EP	365	pr_debug("%s: old_event=%p new_event=%p\n", __func__, old_event, event);
5ba08e2e EP	366
b4e4e140 EP	367	memcpy(event, old_event, sizeof(*event));
	368	initialize_event(event);
	369
	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;
	375	}
	376	}
32c32632	377	event->tgid = get_pid(old_event->tgid);
2069601b LT	378	if (event->data_type == FSNOTIFY_EVENT_PATH)
2069601b LT	379	path_get(&event->path);
b4e4e140 EP	380
	381	return event;
	382	}
	383
a2d8bc6c EP	384	/*
	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.
	388	*
	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...
62ffe5df	394	* @name the filename, if available
a2d8bc6c	395	*/
47882c6f	396	struct fsnotify_event fsnotify_create_event(struct inode to_tell, __u32 mask, void *data,
59b0df21 EP	397	int data_type, const unsigned char *name,
59b0df21 EP	398	u32 cookie, gfp_t gfp)
a2d8bc6c EP	399	{
	400	struct fsnotify_event *event;
	401
6f3a539e	402	event = kmem_cache_zalloc(fsnotify_event_cachep, gfp);
a2d8bc6c EP	403	if (!event)
	404	return NULL;
	405
5ba08e2e EP	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);
	408
a2d8bc6c	409	initialize_event(event);
62ffe5df EP	410
62ffe5df EP	411	if (name) {
f44aebcc	412	event->file_name = kstrdup(name, gfp);
62ffe5df EP	413	if (!event->file_name) {
	414	kmem_cache_free(fsnotify_event_cachep, event);
	415	return NULL;
	416	}
	417	event->name_len = strlen(event->file_name);
	418	}
47882c6f	419
32c32632	420	event->tgid = get_pid(task_tgid(current));
47882c6f	421	event->sync_cookie = cookie;
90586523	422	event->to_tell = to_tell;
b4e4e140	423	event->data_type = data_type;
90586523 EP	424
90586523 EP	425	switch (data_type) {
2069601b LT	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);
90586523 EP	431	break;
	432	}
	433	case FSNOTIFY_EVENT_INODE:
	434	event->inode = data;
90586523 EP	435	break;
	436	case FSNOTIFY_EVENT_NONE:
	437	event->inode = NULL;
2069601b LT	438	event->path.dentry = NULL;
2069601b LT	439	event->path.mnt = NULL;
90586523 EP	440	break;
	441	default:
	442	BUG();
	443	}
	444
	445	event->mask = mask;
	446
	447	return event;
	448	}
	449
	450	__init int fsnotify_notification_init(void)
	451	{
	452	fsnotify_event_cachep = KMEM_CACHE(fsnotify_event, SLAB_PANIC);
a2d8bc6c EP	453	fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);
a2d8bc6c EP	454
b4277d3d EP	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");
90586523 EP	460
	461	return 0;
	462	}
	463	subsys_initcall(fsnotify_notification_init);
	464