Root/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
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
112int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work);
113int btrfs_start_workers(struct btrfs_workers *workers, int num_workers);
114int 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);
117int btrfs_requeue_work(struct btrfs_work *work);
118void btrfs_set_work_high_prio(struct btrfs_work *work);
119#endif
120

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