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/*
* 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.
*/
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/srcu.h>
#include <linux/rculist.h>
#include <linux/wait.h>
#include <linux/fsnotify_backend.h>
#include "fsnotify.h"
#include <asm/atomic.h>
/* protects writes to fsnotify_groups and fsnotify_mask */
static DEFINE_MUTEX(fsnotify_grp_mutex);
/* all groups registered to receive inode filesystem notifications */
LIST_HEAD(fsnotify_inode_groups);
/* all groups registered to receive mount point filesystem notifications */
LIST_HEAD(fsnotify_vfsmount_groups);
void fsnotify_add_vfsmount_group(struct fsnotify_group *group)
{
struct fsnotify_group *group_iter;
mutex_lock(&fsnotify_grp_mutex);
if (!group->on_vfsmount_group_list) {
list_for_each_entry(group_iter, &fsnotify_vfsmount_groups,
vfsmount_group_list) {
/* insert in front of this one? */
if (group < group_iter) {
/* list_add_tail() insert in front of group_iter */
list_add_tail_rcu(&group->inode_group_list,
&group_iter->inode_group_list);
goto out;
}
}
/* apparently we need to be the last entry */
list_add_tail_rcu(&group->vfsmount_group_list, &fsnotify_vfsmount_groups);
}
out:
group->on_vfsmount_group_list = 1;
mutex_unlock(&fsnotify_grp_mutex);
}
void fsnotify_add_inode_group(struct fsnotify_group *group)
{
struct fsnotify_group *group_iter;
mutex_lock(&fsnotify_grp_mutex);
/* add to global group list */
if (!group->on_inode_group_list) {
list_for_each_entry(group_iter, &fsnotify_inode_groups,
inode_group_list) {
if (group < group_iter) {
/* list_add_tail() insert in front of group_iter */
list_add_tail_rcu(&group->inode_group_list,
&group_iter->inode_group_list);
goto out;
}
}
/* apparently we need to be the last entry */
list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups);
}
out:
group->on_inode_group_list = 1;
mutex_unlock(&fsnotify_grp_mutex);
}
/*
* Final freeing of a group
*/
void fsnotify_final_destroy_group(struct fsnotify_group *group)
{
/* clear the notification queue of all events */
fsnotify_flush_notify(group);
if (group->ops->free_group_priv)
group->ops->free_group_priv(group);
kfree(group);
}
/*
* Trying to get rid of a group. We need to first get rid of any outstanding
* allocations and then free the group. Remember that fsnotify_clear_marks_by_group
* could miss marks that are being freed by inode and those marks could still
* hold a reference to this group (via group->num_marks) If we get into that
* situtation, the fsnotify_final_destroy_group will get called when that final
* mark is freed.
*/
static void fsnotify_destroy_group(struct fsnotify_group *group)
{
/* clear all inode marks for this group */
fsnotify_clear_marks_by_group(group);
synchronize_srcu(&fsnotify_mark_srcu);
/* past the point of no return, matches the initial value of 1 */
if (atomic_dec_and_test(&group->num_marks))
fsnotify_final_destroy_group(group);
}
/*
* Remove this group from the global list of groups that will get events
* this can be done even if there are still references and things still using
* this group. This just stops the group from getting new events.
*/
static void __fsnotify_evict_group(struct fsnotify_group *group)
{
BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex));
if (group->on_inode_group_list)
list_del_rcu(&group->inode_group_list);
group->on_inode_group_list = 0;
if (group->on_vfsmount_group_list)
list_del_rcu(&group->vfsmount_group_list);
group->on_vfsmount_group_list = 0;
}
/*
* Called when a group is no longer interested in getting events. This can be
* used if a group is misbehaving or if for some reason a group should no longer
* get any filesystem events.
*/
void fsnotify_evict_group(struct fsnotify_group *group)
{
mutex_lock(&fsnotify_grp_mutex);
__fsnotify_evict_group(group);
mutex_unlock(&fsnotify_grp_mutex);
}
/*
* Drop a reference to a group. Free it if it's through.
*/
void fsnotify_put_group(struct fsnotify_group *group)
{
if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex))
return;
/*
* OK, now we know that there's no other users *and* we hold mutex,
* so no new references will appear
*/
__fsnotify_evict_group(group);
mutex_unlock(&fsnotify_grp_mutex);
fsnotify_destroy_group(group);
}
/*
* Create a new fsnotify_group and hold a reference for the group returned.
*/
struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
{
struct fsnotify_group *group;
group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
if (!group)
return ERR_PTR(-ENOMEM);
/* set to 0 when there a no external references to this group */
atomic_set(&group->refcnt, 1);
/*
* hits 0 when there are no external references AND no marks for
* this group
*/
atomic_set(&group->num_marks, 1);
mutex_init(&group->notification_mutex);
INIT_LIST_HEAD(&group->notification_list);
init_waitqueue_head(&group->notification_waitq);
group->max_events = UINT_MAX;
INIT_LIST_HEAD(&group->inode_group_list);
INIT_LIST_HEAD(&group->vfsmount_group_list);
spin_lock_init(&group->mark_lock);
INIT_LIST_HEAD(&group->marks_list);
group->ops = ops;
return group;
}
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