/*
   * Copyright (C) 2007 Oracle.  All rights reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License v2 as published by the Free Software Foundation.
   *
   * 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; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */
  
  #ifndef __BTRFS_ASYNC_THREAD_
  #define __BTRFS_ASYNC_THREAD_
  
  struct btrfs_worker_thread;
  
  /*
   * This is similar to a workqueue, but it is meant to spread the operations
   * across all available cpus instead of just the CPU that was used to
   * queue the work.  There is also some batching introduced to try and
   * cut down on context switches.
   *
   * By default threads are added on demand up to 2 * the number of cpus.
   * Changing struct btrfs_workers->max_workers is one way to prevent
   * demand creation of kthreads.
   *
   * the basic model of these worker threads is to embed a btrfs_work
   * structure in your own data struct, and use container_of in a
   * work function to get back to your data struct.
   */
  struct btrfs_work {
  	/*

  	 * func should be set to the function you want called

  	 * your work struct is passed as the only arg

  	 *
  	 * ordered_func must be set for work sent to an ordered work queue,
  	 * and it is called to complete a given work item in the same
  	 * order they were sent to the queue.

  	 */
  	void (*func)(struct btrfs_work *work);

  	void (*ordered_func)(struct btrfs_work *work);
  	void (*ordered_free)(struct btrfs_work *work);

  
  	/*
  	 * flags should be set to zero.  It is used to make sure the
  	 * struct is only inserted once into the list.
  	 */
  	unsigned long flags;
  
  	/* don't touch these */
  	struct btrfs_worker_thread *worker;
  	struct list_head list;

  	struct list_head order_list;

  };
  
  struct btrfs_workers {
  	/* current number of running workers */
  	int num_workers;

  	int num_workers_starting;

  	/* max number of workers allowed.  changed by btrfs_start_workers */
  	int max_workers;

  	/* once a worker has this many requests or fewer, it is idle */
  	int idle_thresh;

  	/* force completions in the order they were queued */
  	int ordered;

  	/* more workers required, but in an interrupt handler */
  	int atomic_start_pending;
  
  	/*
  	 * are we allowed to sleep while starting workers or are we required

  	 * to start them at a later time?  If we can't sleep, this indicates
  	 * which queue we need to use to schedule thread creation.

  	 */

  	struct btrfs_workers *atomic_worker_start;

  	/* list with all the work threads.  The workers on the idle thread
  	 * may be actively servicing jobs, but they haven't yet hit the
  	 * idle thresh limit above.
  	 */

  	struct list_head worker_list;

  	struct list_head idle_list;

  	/*
  	 * when operating in ordered mode, this maintains the list
  	 * of work items waiting for completion
  	 */
  	struct list_head order_list;

  	struct list_head prio_order_list;

  	/* lock for finding the next worker thread to queue on */
  	spinlock_t lock;

  	/* lock for the ordered lists */
  	spinlock_t order_lock;

  	/* extra name for this worker, used for current->name */

  	char *name;

  };

  void btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work);
  int btrfs_start_workers(struct btrfs_workers *workers);

  int btrfs_stop_workers(struct btrfs_workers *workers);

  void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max,
  			struct btrfs_workers *async_starter);

  int btrfs_requeue_work(struct btrfs_work *work);

  void btrfs_set_work_high_prio(struct btrfs_work *work);

  #endif