backing-dev.c revision 3fcfab16c5b86eaa3db3a9a31adba550c5b67141 
1
2#include <linux/wait.h>
3#include <linux/backing-dev.h>
4#include <linux/fs.h>
5#include <linux/sched.h>
6#include <linux/module.h>
7
8static wait_queue_head_t congestion_wqh[2] = {
9		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
10		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
11	};
12
13
14void clear_bdi_congested(struct backing_dev_info *bdi, int rw)
15{
16	enum bdi_state bit;
17	wait_queue_head_t *wqh = &congestion_wqh[rw];
18
19	bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
20	clear_bit(bit, &bdi->state);
21	smp_mb__after_clear_bit();
22	if (waitqueue_active(wqh))
23		wake_up(wqh);
24}
25EXPORT_SYMBOL(clear_bdi_congested);
26
27void set_bdi_congested(struct backing_dev_info *bdi, int rw)
28{
29	enum bdi_state bit;
30
31	bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
32	set_bit(bit, &bdi->state);
33}
34EXPORT_SYMBOL(set_bdi_congested);
35
36/**
37 * congestion_wait - wait for a backing_dev to become uncongested
38 * @rw: READ or WRITE
39 * @timeout: timeout in jiffies
40 *
41 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
42 * write congestion.  If no backing_devs are congested then just wait for the
43 * next write to be completed.
44 */
45long congestion_wait(int rw, long timeout)
46{
47	long ret;
48	DEFINE_WAIT(wait);
49	wait_queue_head_t *wqh = &congestion_wqh[rw];
50
51	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
52	ret = io_schedule_timeout(timeout);
53	finish_wait(wqh, &wait);
54	return ret;
55}
56EXPORT_SYMBOL(congestion_wait);
57
58/**
59 * congestion_end - wake up sleepers on a congested backing_dev_info
60 * @rw: READ or WRITE
61 */
62void congestion_end(int rw)
63{
64	wait_queue_head_t *wqh = &congestion_wqh[rw];
65
66	if (waitqueue_active(wqh))
67		wake_up(wqh);
68}
69EXPORT_SYMBOL(congestion_end);
70