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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
*/
#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/memcontrol.h>
#include <linux/fsnotify_backend.h>
#include "fsnotify.h"
#include <linux/atomic.h>
/*
* Final freeing of a group
*/
static void fsnotify_final_destroy_group(struct fsnotify_group *group)
{
if (group->ops->free_group_priv)
group->ops->free_group_priv(group);
mem_cgroup_put(group->memcg);
mutex_destroy(&group->mark_mutex);
kfree(group);
}
/*
* Stop queueing new events for this group. Once this function returns
* fsnotify_add_event() will not add any new events to the group's queue.
*/
void fsnotify_group_stop_queueing(struct fsnotify_group *group)
{
spin_lock(&group->notification_lock);
group->shutdown = true;
spin_unlock(&group->notification_lock);
}
/*
* Trying to get rid of a group. Remove all marks, flush all events and release
* the group reference.
* Note that another thread calling fsnotify_clear_marks_by_group() may still
* hold a ref to the group.
*/
void fsnotify_destroy_group(struct fsnotify_group *group)
{
/*
* Stop queueing new events. The code below is careful enough to not
* require this but fanotify needs to stop queuing events even before
* fsnotify_destroy_group() is called and this makes the other callers
* of fsnotify_destroy_group() to see the same behavior.
*/
fsnotify_group_stop_queueing(group);
/* Clear all marks for this group and queue them for destruction */
fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_ANY);
/*
* Some marks can still be pinned when waiting for response from
* userspace. Wait for those now. fsnotify_prepare_user_wait() will
* not succeed now so this wait is race-free.
*/
wait_event(group->notification_waitq, !atomic_read(&group->user_waits));
/*
* Wait until all marks get really destroyed. We could actually destroy
* them ourselves instead of waiting for worker to do it, however that
* would be racy as worker can already be processing some marks before
* we even entered fsnotify_destroy_group().
*/
fsnotify_wait_marks_destroyed();
/*
* Since we have waited for fsnotify_mark_srcu in
* fsnotify_mark_destroy_list() there can be no outstanding event
* notification against this group. So clearing the notification queue
* of all events is reliable now.
*/
fsnotify_flush_notify(group);
/*
* Destroy overflow event (we cannot use fsnotify_destroy_event() as
* that deliberately ignores overflow events.
*/
if (group->overflow_event)
group->ops->free_event(group, group->overflow_event);
fsnotify_put_group(group);
}
/*
* Get reference to a group.
*/
void fsnotify_get_group(struct fsnotify_group *group)
{
refcount_inc(&group->refcnt);
}
/*
* Drop a reference to a group. Free it if it's through.
*/
void fsnotify_put_group(struct fsnotify_group *group)
{
if (refcount_dec_and_test(&group->refcnt))
fsnotify_final_destroy_group(group);
}
EXPORT_SYMBOL_GPL(fsnotify_put_group);
static struct fsnotify_group *__fsnotify_alloc_group(
const struct fsnotify_ops *ops,
int flags, gfp_t gfp)
{
static struct lock_class_key nofs_marks_lock;
struct fsnotify_group *group;
group = kzalloc(sizeof(struct fsnotify_group), gfp);
if (!group)
return ERR_PTR(-ENOMEM);
/* set to 0 when there a no external references to this group */
refcount_set(&group->refcnt, 1);
atomic_set(&group->user_waits, 0);
spin_lock_init(&group->notification_lock);
INIT_LIST_HEAD(&group->notification_list);
init_waitqueue_head(&group->notification_waitq);
group->max_events = UINT_MAX;
mutex_init(&group->mark_mutex);
INIT_LIST_HEAD(&group->marks_list);
group->ops = ops;
group->flags = flags;
/*
* For most backends, eviction of inode with a mark is not expected,
* because marks hold a refcount on the inode against eviction.
*
* Use a different lockdep class for groups that support evictable
* inode marks, because with evictable marks, mark_mutex is NOT
* fs-reclaim safe - the mutex is taken when evicting inodes.
*/
if (flags & FSNOTIFY_GROUP_NOFS)
lockdep_set_class(&group->mark_mutex, &nofs_marks_lock);
return 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,
int flags)
{
gfp_t gfp = (flags & FSNOTIFY_GROUP_USER) ? GFP_KERNEL_ACCOUNT :
GFP_KERNEL;
return __fsnotify_alloc_group(ops, flags, gfp);
}
EXPORT_SYMBOL_GPL(fsnotify_alloc_group);
int fsnotify_fasync(int fd, struct file *file, int on)
{
struct fsnotify_group *group = file->private_data;
return fasync_helper(fd, file, on, &group->fsn_fa) >= 0 ? 0 : -EIO;
}
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