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