[GitHub/mt8127/android_kernel_alcatel_ttab.git] / fs / notify / mark.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.
 */

/*
 * fsnotify inode mark locking/lifetime/and refcnting
 *
 * REFCNT:
 * The mark->refcnt tells how many "things" in the kernel currently are
 * referencing this object.  The object typically will live inside the kernel
 * with a refcnt of 2, one for each list it is on (i_list, g_list).  Any task
 * which can find this object holding the appropriete locks, can take a reference
 * and the object itself is guaranteed to survive until the reference is dropped.
 *
 * LOCKING:
 * There are 3 spinlocks involved with fsnotify inode marks and they MUST
 * be taken in order as follows:
 *
 * mark->lock
 * group->mark_lock
 * inode->i_lock
 *
 * mark->lock protects 2 things, mark->group and mark->inode.  You must hold
 * that lock to dereference either of these things (they could be NULL even with
 * the lock)
 *
 * group->mark_lock protects the marks_list anchored inside a given group
 * and each mark is hooked via the g_list.  It also sorta protects the
 * free_g_list, which when used is anchored by a private list on the stack of the
 * task which held the group->mark_lock.
 *
 * inode->i_lock protects the i_fsnotify_marks list anchored inside a
 * given inode and each mark is hooked via the i_list. (and sorta the
 * free_i_list)
 *
 *
 * LIFETIME:
 * Inode marks survive between when they are added to an inode and when their
 * refcnt==0.
 *
 * The inode mark can be cleared for a number of different reasons including:
 * - The inode is unlinked for the last time.  (fsnotify_inode_remove)
 * - The inode is being evicted from cache. (fsnotify_inode_delete)
 * - The fs the inode is on is unmounted.  (fsnotify_inode_delete/fsnotify_unmount_inodes)
 * - Something explicitly requests that it be removed.  (fsnotify_destroy_mark)
 * - The fsnotify_group associated with the mark is going away and all such marks
 *   need to be cleaned up. (fsnotify_clear_marks_by_group)
 *
 * Worst case we are given an inode and need to clean up all the marks on that
 * inode.  We take i_lock and walk the i_fsnotify_marks safely.  For each
 * mark on the list we take a reference (so the mark can't disappear under us).
 * We remove that mark form the inode's list of marks and we add this mark to a
 * private list anchored on the stack using i_free_list;  At this point we no
 * longer fear anything finding the mark using the inode's list of marks.
 *
 * We can safely and locklessly run the private list on the stack of everything
 * we just unattached from the original inode.  For each mark on the private list
 * we grab the mark-> and can thus dereference mark->group and mark->inode.  If
 * we see the group and inode are not NULL we take those locks.  Now holding all
 * 3 locks we can completely remove the mark from other tasks finding it in the
 * future.  Remember, 10 things might already be referencing this mark, but they
 * better be holding a ref.  We drop our reference we took before we unhooked it
 * from the inode.  When the ref hits 0 we can free the mark.
 *
 * Very similarly for freeing by group, except we use free_g_list.
 *
 * This has the very interesting property of being able to run concurrently with
 * any (or all) other directions.
 */

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/srcu.h>

#include <asm/atomic.h>

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

struct srcu_struct fsnotify_mark_srcu;
static DEFINE_SPINLOCK(destroy_lock);
static LIST_HEAD(destroy_list);
static DECLARE_WAIT_QUEUE_HEAD(destroy_waitq);

void fsnotify_get_mark(struct fsnotify_mark *mark)
{
	atomic_inc(&mark->refcnt);
}

void fsnotify_put_mark(struct fsnotify_mark *mark)
{
	if (atomic_dec_and_test(&mark->refcnt))
		mark->free_mark(mark);
}

/*
 * Any time a mark is getting freed we end up here.
 * The caller had better be holding a reference to this mark so we don't actually
 * do the final put under the mark->lock
 */
void fsnotify_destroy_mark(struct fsnotify_mark *mark)
{
	struct fsnotify_group *group;
	struct inode *inode = NULL;

	spin_lock(&mark->lock);

	group = mark->group;

	/* something else already called this function on this mark */
	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
		spin_unlock(&mark->lock);
		return;
	}

	mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;

	/* 1 from caller and 1 for being on i_list/g_list */
	BUG_ON(atomic_read(&mark->refcnt) < 2);

	spin_lock(&group->mark_lock);

	if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
		inode = mark->i.inode;
		fsnotify_destroy_inode_mark(mark);
	} else if (mark->flags & FSNOTIFY_MARK_FLAG_VFSMOUNT)
		fsnotify_destroy_vfsmount_mark(mark);
	else
		BUG();

	list_del_init(&mark->g_list);

	spin_unlock(&group->mark_lock);
	spin_unlock(&mark->lock);

	spin_lock(&destroy_lock);
	list_add(&mark->destroy_list, &destroy_list);
	spin_unlock(&destroy_lock);
	wake_up(&destroy_waitq);

	/*
	 * Some groups like to know that marks are being freed.  This is a
	 * callback to the group function to let it know that this mark
	 * is being freed.
	 */
	if (group->ops->freeing_mark)
		group->ops->freeing_mark(mark, group);

	/*
	 * __fsnotify_update_child_dentry_flags(inode);
	 *
	 * I really want to call that, but we can't, we have no idea if the inode
	 * still exists the second we drop the mark->lock.
	 *
	 * The next time an event arrive to this inode from one of it's children
	 * __fsnotify_parent will see that the inode doesn't care about it's
	 * children and will update all of these flags then.  So really this
	 * is just a lazy update (and could be a perf win...)
	 */

	if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
		iput(inode);

	/*
	 * it's possible that this group tried to destroy itself, but this
	 * this mark was simultaneously being freed by inode.  If that's the
	 * case, we finish freeing the group here.
	 */
	if (unlikely(atomic_dec_and_test(&group->num_marks)))
		fsnotify_final_destroy_group(group);
}

void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask)
{
	assert_spin_locked(&mark->lock);

	mark->mask = mask;

	if (mark->flags & FSNOTIFY_MARK_FLAG_INODE)
		fsnotify_set_inode_mark_mask_locked(mark, mask);
}

void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask)
{
	assert_spin_locked(&mark->lock);

	mark->ignored_mask = mask;
}

/*
 * Attach an initialized mark to a given group and fs object.
 * These marks may be used for the fsnotify backend to determine which
 * event types should be delivered to which group.
 */
int fsnotify_add_mark(struct fsnotify_mark *mark,
		      struct fsnotify_group *group, struct inode *inode,
		      struct vfsmount *mnt, int allow_dups)
{
	int ret = 0;

	BUG_ON(inode && mnt);
	BUG_ON(!inode && !mnt);

	/*
	 * LOCKING ORDER!!!!
	 * mark->lock
	 * group->mark_lock
	 * inode->i_lock
	 */
	spin_lock(&mark->lock);
	spin_lock(&group->mark_lock);

	mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;

	mark->group = group;
	list_add(&mark->g_list, &group->marks_list);
	atomic_inc(&group->num_marks);
	fsnotify_get_mark(mark); /* for i_list and g_list */

	if (inode) {
		ret = fsnotify_add_inode_mark(mark, group, inode, allow_dups);
		if (ret)
			goto err;
	} else if (mnt) {
		ret = fsnotify_add_vfsmount_mark(mark, group, mnt, allow_dups);
		if (ret)
			goto err;
	} else {
		BUG();
	}

	spin_unlock(&group->mark_lock);

	/* this will pin the object if appropriate */
	fsnotify_set_mark_mask_locked(mark, mark->mask);

	spin_unlock(&mark->lock);

	if (inode)
		__fsnotify_update_child_dentry_flags(inode);

	return ret;
err:
	mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
	list_del_init(&mark->g_list);
	mark->group = NULL;
	atomic_dec(&group->num_marks);

	spin_unlock(&group->mark_lock);
	spin_unlock(&mark->lock);

	spin_lock(&destroy_lock);
	list_add(&mark->destroy_list, &destroy_list);
	spin_unlock(&destroy_lock);
	wake_up(&destroy_waitq);

	return ret;
}

/*
 * clear any marks in a group in which mark->flags & flags is true
 */
void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
					 unsigned int flags)
{
	struct fsnotify_mark *lmark, *mark;
	LIST_HEAD(free_list);

	spin_lock(&group->mark_lock);
	list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
		if (mark->flags & flags) {
			list_add(&mark->free_g_list, &free_list);
			list_del_init(&mark->g_list);
			fsnotify_get_mark(mark);
		}
	}
	spin_unlock(&group->mark_lock);

	list_for_each_entry_safe(mark, lmark, &free_list, free_g_list) {
		fsnotify_destroy_mark(mark);
		fsnotify_put_mark(mark);
	}
}

/*
 * Given a group, destroy all of the marks associated with that group.
 */
void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
{
	fsnotify_clear_marks_by_group_flags(group, (unsigned int)-1);
}

void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old)
{
	assert_spin_locked(&old->lock);
	new->i.inode = old->i.inode;
	new->m.mnt = old->m.mnt;
	new->group = old->group;
	new->mask = old->mask;
	new->free_mark = old->free_mark;
}

/*
 * Nothing fancy, just initialize lists and locks and counters.
 */
void fsnotify_init_mark(struct fsnotify_mark *mark,
			void (*free_mark)(struct fsnotify_mark *mark))
{
	memset(mark, 0, sizeof(*mark));
	spin_lock_init(&mark->lock);
	atomic_set(&mark->refcnt, 1);
	mark->free_mark = free_mark;
}

static int fsnotify_mark_destroy(void *ignored)
{
	struct fsnotify_mark *mark, *next;
	LIST_HEAD(private_destroy_list);

	for (;;) {
		spin_lock(&destroy_lock);
		/* exchange the list head */
		list_replace_init(&destroy_list, &private_destroy_list);
		spin_unlock(&destroy_lock);

		synchronize_srcu(&fsnotify_mark_srcu);

		list_for_each_entry_safe(mark, next, &private_destroy_list, destroy_list) {
			list_del_init(&mark->destroy_list);
			fsnotify_put_mark(mark);
		}

		wait_event_interruptible(destroy_waitq, !list_empty(&destroy_list));
	}

	return 0;
}

static int __init fsnotify_mark_init(void)
{
	struct task_struct *thread;

	thread = kthread_run(fsnotify_mark_destroy, NULL,
			     "fsnotify_mark");
	if (IS_ERR(thread))
		panic("unable to start fsnotify mark destruction thread.");

	return 0;
}
device_initcall(fsnotify_mark_init);
Commit	Line	Data
5444e298 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
	19	/*
	20	* fsnotify inode mark locking/lifetime/and refcnting
	21	*
	22	* REFCNT:
	23	* The mark->refcnt tells how many "things" in the kernel currently are
	24	* referencing this object. The object typically will live inside the kernel
	25	* with a refcnt of 2, one for each list it is on (i_list, g_list). Any task
	26	* which can find this object holding the appropriete locks, can take a reference
25985edc	27	* and the object itself is guaranteed to survive until the reference is dropped.
5444e298 EP	28	*
	29	* LOCKING:
	30	* There are 3 spinlocks involved with fsnotify inode marks and they MUST
	31	* be taken in order as follows:
	32	*
	33	* mark->lock
	34	* group->mark_lock
	35	* inode->i_lock
	36	*
	37	* mark->lock protects 2 things, mark->group and mark->inode. You must hold
	38	* that lock to dereference either of these things (they could be NULL even with
	39	* the lock)
	40	*
	41	* group->mark_lock protects the marks_list anchored inside a given group
	42	* and each mark is hooked via the g_list. It also sorta protects the
	43	* free_g_list, which when used is anchored by a private list on the stack of the
	44	* task which held the group->mark_lock.
	45	*
	46	* inode->i_lock protects the i_fsnotify_marks list anchored inside a
	47	* given inode and each mark is hooked via the i_list. (and sorta the
	48	* free_i_list)
	49	*
	50	*
	51	* LIFETIME:
	52	* Inode marks survive between when they are added to an inode and when their
	53	* refcnt==0.
	54	*
	55	* The inode mark can be cleared for a number of different reasons including:
	56	* - The inode is unlinked for the last time. (fsnotify_inode_remove)
	57	* - The inode is being evicted from cache. (fsnotify_inode_delete)
	58	* - The fs the inode is on is unmounted. (fsnotify_inode_delete/fsnotify_unmount_inodes)
	59	* - Something explicitly requests that it be removed. (fsnotify_destroy_mark)
	60	* - The fsnotify_group associated with the mark is going away and all such marks
	61	* need to be cleaned up. (fsnotify_clear_marks_by_group)
	62	*
	63	* Worst case we are given an inode and need to clean up all the marks on that
	64	* inode. We take i_lock and walk the i_fsnotify_marks safely. For each
	65	* mark on the list we take a reference (so the mark can't disappear under us).
	66	* We remove that mark form the inode's list of marks and we add this mark to a
	67	* private list anchored on the stack using i_free_list; At this point we no
	68	* longer fear anything finding the mark using the inode's list of marks.
	69	*
	70	* We can safely and locklessly run the private list on the stack of everything
	71	* we just unattached from the original inode. For each mark on the private list
	72	* we grab the mark-> and can thus dereference mark->group and mark->inode. If
	73	* we see the group and inode are not NULL we take those locks. Now holding all
	74	* 3 locks we can completely remove the mark from other tasks finding it in the
	75	* future. Remember, 10 things might already be referencing this mark, but they
	76	* better be holding a ref. We drop our reference we took before we unhooked it
	77	* from the inode. When the ref hits 0 we can free the mark.
	78	*
	79	* Very similarly for freeing by group, except we use free_g_list.
	80	*
	81	* This has the very interesting property of being able to run concurrently with
	82	* any (or all) other directions.
	83	*/
	84
	85	#include <linux/fs.h>
	86	#include <linux/init.h>
	87	#include <linux/kernel.h>
75c1be48	88	#include <linux/kthread.h>
5444e298 EP	89	#include <linux/module.h>
	90	#include <linux/mutex.h>
	91	#include <linux/slab.h>
	92	#include <linux/spinlock.h>
75c1be48	93	#include <linux/srcu.h>
5444e298 EP	94
	95	#include <asm/atomic.h>
	96
	97	#include <linux/fsnotify_backend.h>
	98	#include "fsnotify.h"
	99
75c1be48 EP	100	struct srcu_struct fsnotify_mark_srcu;
	101	static DEFINE_SPINLOCK(destroy_lock);
	102	static LIST_HEAD(destroy_list);
	103	static DECLARE_WAIT_QUEUE_HEAD(destroy_waitq);
	104
5444e298 EP	105	void fsnotify_get_mark(struct fsnotify_mark *mark)
	106	{
	107	atomic_inc(&mark->refcnt);
	108	}
	109
	110	void fsnotify_put_mark(struct fsnotify_mark *mark)
	111	{
	112	if (atomic_dec_and_test(&mark->refcnt))
	113	mark->free_mark(mark);
	114	}
	115
	116	/*
	117	* Any time a mark is getting freed we end up here.
	118	* The caller had better be holding a reference to this mark so we don't actually
	119	* do the final put under the mark->lock
	120	*/
	121	void fsnotify_destroy_mark(struct fsnotify_mark *mark)
	122	{
	123	struct fsnotify_group *group;
0d48b7f0	124	struct inode *inode = NULL;
5444e298 EP	125
	126	spin_lock(&mark->lock);
	127
	128	group = mark->group;
5444e298	129
700307a2 EP	130	/* something else already called this function on this mark */
700307a2 EP	131	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
5444e298 EP	132	spin_unlock(&mark->lock);
	133	return;
	134	}
	135
700307a2 EP	136	mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
700307a2 EP	137
5444e298 EP	138	/* 1 from caller and 1 for being on i_list/g_list */
	139	BUG_ON(atomic_read(&mark->refcnt) < 2);
	140
	141	spin_lock(&group->mark_lock);
	142
0d48b7f0	143	if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
0d48b7f0	144	inode = mark->i.inode;
b31d397e	145	fsnotify_destroy_inode_mark(mark);
0d48b7f0 EP	146	} else if (mark->flags & FSNOTIFY_MARK_FLAG_VFSMOUNT)
0d48b7f0 EP	147	fsnotify_destroy_vfsmount_mark(mark);
5444e298 EP	148	else
	149	BUG();
	150
	151	list_del_init(&mark->g_list);
5444e298	152
5444e298 EP	153	spin_unlock(&group->mark_lock);
	154	spin_unlock(&mark->lock);
	155
75c1be48 EP	156	spin_lock(&destroy_lock);
	157	list_add(&mark->destroy_list, &destroy_list);
	158	spin_unlock(&destroy_lock);
	159	wake_up(&destroy_waitq);
	160
5444e298 EP	161	/*
	162	* Some groups like to know that marks are being freed. This is a
	163	* callback to the group function to let it know that this mark
	164	* is being freed.
	165	*/
	166	if (group->ops->freeing_mark)
	167	group->ops->freeing_mark(mark, group);
	168
	169	/*
	170	* __fsnotify_update_child_dentry_flags(inode);
	171	*
	172	* I really want to call that, but we can't, we have no idea if the inode
	173	* still exists the second we drop the mark->lock.
	174	*
	175	* The next time an event arrive to this inode from one of it's children
	176	* __fsnotify_parent will see that the inode doesn't care about it's
	177	* children and will update all of these flags then. So really this
	178	* is just a lazy update (and could be a perf win...)
	179	*/
	180
90b1e7a5	181	if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
0d48b7f0	182	iput(inode);
5444e298 EP	183
	184	/*
	185	* it's possible that this group tried to destroy itself, but this
	186	* this mark was simultaneously being freed by inode. If that's the
	187	* case, we finish freeing the group here.
	188	*/
	189	if (unlikely(atomic_dec_and_test(&group->num_marks)))
	190	fsnotify_final_destroy_group(group);
	191	}
	192
90b1e7a5 EP	193	void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask)
	194	{
	195	assert_spin_locked(&mark->lock);
	196
	197	mark->mask = mask;
	198
	199	if (mark->flags & FSNOTIFY_MARK_FLAG_INODE)
	200	fsnotify_set_inode_mark_mask_locked(mark, mask);
	201	}
	202
33af5e32 EP	203	void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask)
	204	{
	205	assert_spin_locked(&mark->lock);
	206
	207	mark->ignored_mask = mask;
	208	}
90b1e7a5	209
5444e298 EP	210	/*
	211	* Attach an initialized mark to a given group and fs object.
	212	* These marks may be used for the fsnotify backend to determine which
	213	* event types should be delivered to which group.
	214	*/
	215	int fsnotify_add_mark(struct fsnotify_mark *mark,
	216	struct fsnotify_group group, struct inode inode,
	217	struct vfsmount *mnt, int allow_dups)
	218	{
	219	int ret = 0;
	220
5444e298 EP	221	BUG_ON(inode && mnt);
	222	BUG_ON(!inode && !mnt);
	223
5444e298 EP	224	/*
	225	* LOCKING ORDER!!!!
	226	* mark->lock
	227	* group->mark_lock
	228	* inode->i_lock
	229	*/
	230	spin_lock(&mark->lock);
	231	spin_lock(&group->mark_lock);
	232
700307a2 EP	233	mark->flags \|= FSNOTIFY_MARK_FLAG_ALIVE;
700307a2 EP	234
5444e298 EP	235	mark->group = group;
	236	list_add(&mark->g_list, &group->marks_list);
	237	atomic_inc(&group->num_marks);
	238	fsnotify_get_mark(mark); /* for i_list and g_list */
	239
	240	if (inode) {
	241	ret = fsnotify_add_inode_mark(mark, group, inode, allow_dups);
	242	if (ret)
	243	goto err;
0d48b7f0 EP	244	} else if (mnt) {
	245	ret = fsnotify_add_vfsmount_mark(mark, group, mnt, allow_dups);
	246	if (ret)
	247	goto err;
5444e298 EP	248	} else {
	249	BUG();
	250	}
	251
	252	spin_unlock(&group->mark_lock);
90b1e7a5 EP	253
	254	/* this will pin the object if appropriate */
	255	fsnotify_set_mark_mask_locked(mark, mark->mask);
	256
5444e298 EP	257	spin_unlock(&mark->lock);
	258
	259	if (inode)
	260	__fsnotify_update_child_dentry_flags(inode);
	261
	262	return ret;
	263	err:
700307a2	264	mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
5444e298	265	list_del_init(&mark->g_list);
75c1be48	266	mark->group = NULL;
5444e298	267	atomic_dec(&group->num_marks);
5444e298 EP	268
	269	spin_unlock(&group->mark_lock);
	270	spin_unlock(&mark->lock);
	271
75c1be48 EP	272	spin_lock(&destroy_lock);
	273	list_add(&mark->destroy_list, &destroy_list);
	274	spin_unlock(&destroy_lock);
	275	wake_up(&destroy_waitq);
	276
5444e298 EP	277	return ret;
	278	}
	279
	280	/*
4d92604c	281	* clear any marks in a group in which mark->flags & flags is true
5444e298	282	*/
4d92604c EP	283	void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
4d92604c EP	284	unsigned int flags)
5444e298 EP	285	{
	286	struct fsnotify_mark lmark, mark;
	287	LIST_HEAD(free_list);
	288
	289	spin_lock(&group->mark_lock);
	290	list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
4d92604c EP	291	if (mark->flags & flags) {
	292	list_add(&mark->free_g_list, &free_list);
	293	list_del_init(&mark->g_list);
	294	fsnotify_get_mark(mark);
	295	}
5444e298 EP	296	}
	297	spin_unlock(&group->mark_lock);
	298
	299	list_for_each_entry_safe(mark, lmark, &free_list, free_g_list) {
	300	fsnotify_destroy_mark(mark);
	301	fsnotify_put_mark(mark);
	302	}
	303	}
	304
4d92604c EP	305	/*
	306	* Given a group, destroy all of the marks associated with that group.
	307	*/
	308	void fsnotify_clear_marks_by_group(struct fsnotify_group *group)
	309	{
	310	fsnotify_clear_marks_by_group_flags(group, (unsigned int)-1);
	311	}
	312
5444e298 EP	313	void fsnotify_duplicate_mark(struct fsnotify_mark new, struct fsnotify_mark old)
	314	{
	315	assert_spin_locked(&old->lock);
	316	new->i.inode = old->i.inode;
	317	new->m.mnt = old->m.mnt;
	318	new->group = old->group;
	319	new->mask = old->mask;
	320	new->free_mark = old->free_mark;
	321	}
	322
	323	/*
	324	* Nothing fancy, just initialize lists and locks and counters.
	325	*/
	326	void fsnotify_init_mark(struct fsnotify_mark *mark,
	327	void (free_mark)(struct fsnotify_mark mark))
	328	{
ba643f04	329	memset(mark, 0, sizeof(*mark));
5444e298 EP	330	spin_lock_init(&mark->lock);
5444e298 EP	331	atomic_set(&mark->refcnt, 1);
5444e298 EP	332	mark->free_mark = free_mark;
5444e298 EP	333	}
75c1be48 EP	334
	335	static int fsnotify_mark_destroy(void *ignored)
	336	{
	337	struct fsnotify_mark mark, next;
	338	LIST_HEAD(private_destroy_list);
	339
	340	for (;;) {
	341	spin_lock(&destroy_lock);
8778abb9 AG	342	/* exchange the list head */
8778abb9 AG	343	list_replace_init(&destroy_list, &private_destroy_list);
75c1be48 EP	344	spin_unlock(&destroy_lock);
	345
	346	synchronize_srcu(&fsnotify_mark_srcu);
	347
	348	list_for_each_entry_safe(mark, next, &private_destroy_list, destroy_list) {
	349	list_del_init(&mark->destroy_list);
	350	fsnotify_put_mark(mark);
	351	}
	352
	353	wait_event_interruptible(destroy_waitq, !list_empty(&destroy_list));
	354	}
	355
	356	return 0;
	357	}
	358
	359	static int __init fsnotify_mark_init(void)
	360	{
	361	struct task_struct *thread;
	362
	363	thread = kthread_run(fsnotify_mark_destroy, NULL,
	364	"fsnotify_mark");
	365	if (IS_ERR(thread))
	366	panic("unable to start fsnotify mark destruction thread.");
	367
	368	return 0;
	369	}
	370	device_initcall(fsnotify_mark_init);