text: /*
   *  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 <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);
  
  	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_ALL_TYPES);
  
  	/*
  	 * 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->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);
  }
  
  /*
   * 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 */
  	refcount_set(&group->refcnt, 1);
  	atomic_set(&group->num_marks, 0);
  	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;
  
  	return 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;
  }
  