fs/btrfs/async-thread.h

   1 /*
   2  * Copyright (C) 2007 Oracle.  All rights reserved.
   3  * Copyright (C) 2014 Fujitsu.  All rights reserved.
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public
   7  * License v2 as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public
  15  * License along with this program; if not, write to the
  16  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17  * Boston, MA 021110-1307, USA.
  18  */
  19
  20 #ifndef __BTRFS_ASYNC_THREAD_
  21 #define __BTRFS_ASYNC_THREAD_
  22
  23 struct btrfs_worker_thread;
  24
  25 /*
  26  * This is similar to a workqueue, but it is meant to spread the operations
  27  * across all available cpus instead of just the CPU that was used to
  28  * queue the work.  There is also some batching introduced to try and
  29  * cut down on context switches.
  30  *
  31  * By default threads are added on demand up to 2 * the number of cpus.
  32  * Changing struct btrfs_workers->max_workers is one way to prevent
  33  * demand creation of kthreads.
  34  *
  35  * the basic model of these worker threads is to embed a btrfs_work
  36  * structure in your own data struct, and use container_of in a
  37  * work function to get back to your data struct.
  38  */
  39 struct btrfs_work {
  40         /*
  41          * func should be set to the function you want called
  42          * your work struct is passed as the only arg
  43          *
  44          * ordered_func must be set for work sent to an ordered work queue,
  45          * and it is called to complete a given work item in the same
  46          * order they were sent to the queue.
  47          */
  48         void (*func)(struct btrfs_work *work);
  49         void (*ordered_func)(struct btrfs_work *work);
  50         void (*ordered_free)(struct btrfs_work *work);
  51
  52         /*
  53          * flags should be set to zero.  It is used to make sure the
  54          * struct is only inserted once into the list.
  55          */
  56         unsigned long flags;
  57
  58         /* don't touch these */
  59         struct btrfs_worker_thread *worker;
  60         struct list_head list;
  61         struct list_head order_list;
  62 };
  63
  64 struct btrfs_workers {
  65         /* current number of running workers */
  66         int num_workers;
  67
  68         int num_workers_starting;
  69
  70         /* max number of workers allowed.  changed by btrfs_start_workers */
  71         int max_workers;
  72
  73         /* once a worker has this many requests or fewer, it is idle */
  74         int idle_thresh;
  75
  76         /* force completions in the order they were queued */
  77         int ordered;
  78
  79         /* more workers required, but in an interrupt handler */
  80         int atomic_start_pending;
  81
  82         /*
  83          * are we allowed to sleep while starting workers or are we required
  84          * to start them at a later time?  If we can't sleep, this indicates
  85          * which queue we need to use to schedule thread creation.
  86          */
  87         struct btrfs_workers *atomic_worker_start;
  88
  89         /* list with all the work threads.  The workers on the idle thread
  90          * may be actively servicing jobs, but they haven't yet hit the
  91          * idle thresh limit above.
  92          */
  93         struct list_head worker_list;
  94         struct list_head idle_list;
  95
  96         /*
  97          * when operating in ordered mode, this maintains the list
  98          * of work items waiting for completion
  99          */
 100         struct list_head order_list;
 101         struct list_head prio_order_list;
 102
 103         /* lock for finding the next worker thread to queue on */
 104         spinlock_t lock;
 105
 106         /* lock for the ordered lists */
 107         spinlock_t order_lock;
 108
 109         /* extra name for this worker, used for current->name */
 110         char *name;
 111
 112         int stopping;
 113 };
 114
 115 void btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work);
 116 int btrfs_start_workers(struct btrfs_workers *workers);
 117 void btrfs_stop_workers(struct btrfs_workers *workers);
 118 void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max,
 119                         struct btrfs_workers *async_starter);
 120 void btrfs_requeue_work(struct btrfs_work *work);
 121 void btrfs_set_work_high_prio(struct btrfs_work *work);
 122
 123 struct btrfs_workqueue_struct;
 124 /* Internal use only */
 125 struct __btrfs_workqueue_struct;
 126
 127 struct btrfs_work_struct {
 128         void (*func)(struct btrfs_work_struct *arg);
 129         void (*ordered_func)(struct btrfs_work_struct *arg);
 130         void (*ordered_free)(struct btrfs_work_struct *arg);
 131
 132         /* Don't touch things below */
 133         struct work_struct normal_work;
 134         struct list_head ordered_list;
 135         struct __btrfs_workqueue_struct *wq;
 136         unsigned long flags;
 137 };
 138
 139 struct btrfs_workqueue_struct *btrfs_alloc_workqueue(char *name,
 140                                                      int flags,
 141                                                      int max_active);
 142 void btrfs_init_work(struct btrfs_work_struct *work,
 143                      void (*func)(struct btrfs_work_struct *),
 144                      void (*ordered_func)(struct btrfs_work_struct *),
 145                      void (*ordered_free)(struct btrfs_work_struct *));
 146 void btrfs_queue_work(struct btrfs_workqueue_struct *wq,
 147                       struct btrfs_work_struct *work);
 148 void btrfs_destroy_workqueue(struct btrfs_workqueue_struct *wq);
 149 void btrfs_workqueue_set_max(struct btrfs_workqueue_struct *wq, int max);
 150 void btrfs_set_work_high_priority(struct btrfs_work_struct *work);
 151 #endif