fs/btrfs/async-thread.h

   1 /*
   2  * Copyright (C) 2007 Oracle.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #ifndef __BTRFS_ASYNC_THREAD_
  20 #define __BTRFS_ASYNC_THREAD_
  21
  22 struct btrfs_worker_thread;
  23
  24 /*
  25  * This is similar to a workqueue, but it is meant to spread the operations
  26  * across all available cpus instead of just the CPU that was used to
  27  * queue the work.  There is also some batching introduced to try and
  28  * cut down on context switches.
  29  *
  30  * By default threads are added on demand up to 2 * the number of cpus.
  31  * Changing struct btrfs_workers->max_workers is one way to prevent
  32  * demand creation of kthreads.
  33  *
  34  * the basic model of these worker threads is to embed a btrfs_work
  35  * structure in your own data struct, and use container_of in a
  36  * work function to get back to your data struct.
  37  */
  38 struct btrfs_work {
  39         /*
  40          * only func should be set to the function you want called
  41          * your work struct is passed as the only arg
  42          */
  43         void (*func)(struct btrfs_work *work);
  44
  45         /*
  46          * flags should be set to zero.  It is used to make sure the
  47          * struct is only inserted once into the list.
  48          */
  49         unsigned long flags;
  50
  51         /* don't touch these */
  52         struct btrfs_worker_thread *worker;
  53         struct list_head list;
  54 };
  55
  56 struct btrfs_workers {
  57         /* current number of running workers */
  58         int num_workers;
  59
  60         /* max number of workers allowed.  changed by btrfs_start_workers */
  61         int max_workers;
  62
  63         /* once a worker has this many requests or fewer, it is idle */
  64         int idle_thresh;
  65
  66         /* list with all the work threads */
  67         struct list_head worker_list;
  68         struct list_head idle_list;
  69
  70         /* lock for finding the next worker thread to queue on */
  71         spinlock_t lock;
  72
  73         /* extra name for this worker */
  74         char *name;
  75 };
  76
  77 int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work);
  78 int btrfs_start_workers(struct btrfs_workers *workers, int num_workers);
  79 int btrfs_stop_workers(struct btrfs_workers *workers);
  80 void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max);
  81 int btrfs_requeue_work(struct btrfs_work *work);
  82 #endif