[PATCH] nfs: fix congestion control
[linux-2.6.git] / mm / backing-dev.c
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
8 static 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
14 void 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 }
25 EXPORT_SYMBOL(clear_bdi_congested);
26
27 void 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 }
34 EXPORT_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  */
45 long 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 }
56 EXPORT_SYMBOL(congestion_wait);
57
58 long congestion_wait_interruptible(int rw, long timeout)
59 {
60         long ret;
61         DEFINE_WAIT(wait);
62         wait_queue_head_t *wqh = &congestion_wqh[rw];
63
64         prepare_to_wait(wqh, &wait, TASK_INTERRUPTIBLE);
65         if (signal_pending(current))
66                 ret = -ERESTARTSYS;
67         else
68                 ret = io_schedule_timeout(timeout);
69         finish_wait(wqh, &wait);
70         return ret;
71 }
72 EXPORT_SYMBOL(congestion_wait_interruptible);
73
74 /**
75  * congestion_end - wake up sleepers on a congested backing_dev_info
76  * @rw: READ or WRITE
77  */
78 void congestion_end(int rw)
79 {
80         wait_queue_head_t *wqh = &congestion_wqh[rw];
81
82         if (waitqueue_active(wqh))
83                 wake_up(wqh);
84 }
85 EXPORT_SYMBOL(congestion_end);