linux/fs/btrfs/async-thread.h
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   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
  22struct 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 */
  38struct btrfs_work {
  39        /*
  40         * func should be set to the function you want called
  41         * your work struct is passed as the only arg
  42         *
  43         * ordered_func must be set for work sent to an ordered work queue,
  44         * and it is called to complete a given work item in the same
  45         * order they were sent to the queue.
  46         */
  47        void (*func)(struct btrfs_work *work);
  48        void (*ordered_func)(struct btrfs_work *work);
  49        void (*ordered_free)(struct btrfs_work *work);
  50
  51        /*
  52         * flags should be set to zero.  It is used to make sure the
  53         * struct is only inserted once into the list.
  54         */
  55        unsigned long flags;
  56
  57        /* don't touch these */
  58        struct btrfs_worker_thread *worker;
  59        struct list_head list;
  60        struct list_head order_list;
  61};
  62
  63struct btrfs_workers {
  64        /* current number of running workers */
  65        int num_workers;
  66
  67        int num_workers_starting;
  68
  69        /* max number of workers allowed.  changed by btrfs_start_workers */
  70        int max_workers;
  71
  72        /* once a worker has this many requests or fewer, it is idle */
  73        int idle_thresh;
  74
  75        /* force completions in the order they were queued */
  76        int ordered;
  77
  78        /* more workers required, but in an interrupt handler */
  79        int atomic_start_pending;
  80
  81        /*
  82         * are we allowed to sleep while starting workers or are we required
  83         * to start them at a later time?  If we can't sleep, this indicates
  84         * which queue we need to use to schedule thread creation.
  85         */
  86        struct btrfs_workers *atomic_worker_start;
  87
  88        /* list with all the work threads.  The workers on the idle thread
  89         * may be actively servicing jobs, but they haven't yet hit the
  90         * idle thresh limit above.
  91         */
  92        struct list_head worker_list;
  93        struct list_head idle_list;
  94
  95        /*
  96         * when operating in ordered mode, this maintains the list
  97         * of work items waiting for completion
  98         */
  99        struct list_head order_list;
 100        struct list_head prio_order_list;
 101
 102        /* lock for finding the next worker thread to queue on */
 103        spinlock_t lock;
 104
 105        /* lock for the ordered lists */
 106        spinlock_t order_lock;
 107
 108        /* extra name for this worker, used for current->name */
 109        char *name;
 110};
 111
 112void btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work);
 113int btrfs_start_workers(struct btrfs_workers *workers);
 114void btrfs_stop_workers(struct btrfs_workers *workers);
 115void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max,
 116                        struct btrfs_workers *async_starter);
 117void btrfs_requeue_work(struct btrfs_work *work);
 118void btrfs_set_work_high_prio(struct btrfs_work *work);
 119#endif
 120
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