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 /**
  59  * congestion_end - wake up sleepers on a congested backing_dev_info
  60  * @rw: READ or WRITE
  61  */
  62 void 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 }
  69 EXPORT_SYMBOL(congestion_end);