/*
   *  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
   */

  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);
  }
  
  /*

   * Drop a reference to a group.  Free it if it's through.
   */
  void fsnotify_put_group(struct fsnotify_group *group)
  {

  	if (atomic_dec_and_test(&group->refcnt))
  		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;

  	spin_lock_init(&group->mark_lock);

  	INIT_LIST_HEAD(&group->marks_list);

  	group->ops = ops;

  	return group;
  }