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   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 int bdi_init(struct backing_dev_info *bdi)
   9 {
  10         int i, j;
  11         int err;
  12
  13         for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
  14                 err = percpu_counter_init_irq(&bdi->bdi_stat[i], 0);
  15                 if (err) {
  16                         for (j = 0; j < i; j++)
  17                                 percpu_counter_destroy(&bdi->bdi_stat[i]);
  18                         break;
  19                 }
  20         }
  21
  22         return err;
  23 }
  24 EXPORT_SYMBOL(bdi_init);
  25
  26 void bdi_destroy(struct backing_dev_info *bdi)
  27 {
  28         int i;
  29
  30         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
  31                 percpu_counter_destroy(&bdi->bdi_stat[i]);
  32 }
  33 EXPORT_SYMBOL(bdi_destroy);
  34
  35 static wait_queue_head_t congestion_wqh[2] = {
  36                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
  37                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
  38         };
  39
  40
  41 void clear_bdi_congested(struct backing_dev_info *bdi, int rw)
  42 {
  43         enum bdi_state bit;
  44         wait_queue_head_t *wqh = &congestion_wqh[rw];
  45
  46         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
  47         clear_bit(bit, &bdi->state);
  48         smp_mb__after_clear_bit();
  49         if (waitqueue_active(wqh))
  50                 wake_up(wqh);
  51 }
  52 EXPORT_SYMBOL(clear_bdi_congested);
  53
  54 void set_bdi_congested(struct backing_dev_info *bdi, int rw)
  55 {
  56         enum bdi_state bit;
  57
  58         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
  59         set_bit(bit, &bdi->state);
  60 }
  61 EXPORT_SYMBOL(set_bdi_congested);
  62
  63 /**
  64  * congestion_wait - wait for a backing_dev to become uncongested
  65  * @rw: READ or WRITE
  66  * @timeout: timeout in jiffies
  67  *
  68  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
  69  * write congestion.  If no backing_devs are congested then just wait for the
  70  * next write to be completed.
  71  */
  72 long congestion_wait(int rw, long timeout)
  73 {
  74         long ret;
  75         DEFINE_WAIT(wait);
  76         wait_queue_head_t *wqh = &congestion_wqh[rw];
  77
  78         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
  79         ret = io_schedule_timeout(timeout);
  80         finish_wait(wqh, &wait);
  81         return ret;
  82 }
  83 EXPORT_SYMBOL(congestion_wait);