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 int bdi_init(struct backing_dev_info *bdi)
   9 {
  10         int i;
  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                         goto err;
  17         }
  18
  19         bdi->dirty_exceeded = 0;
  20         err = prop_local_init_percpu(&bdi->completions);
  21
  22         if (err) {
  23 err:
  24                 while (i--)
  25                         percpu_counter_destroy(&bdi->bdi_stat[i]);
  26         }
  27
  28         return err;
  29 }
  30 EXPORT_SYMBOL(bdi_init);
  31
  32 void bdi_destroy(struct backing_dev_info *bdi)
  33 {
  34         int i;
  35
  36         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
  37                 percpu_counter_destroy(&bdi->bdi_stat[i]);
  38
  39         prop_local_destroy_percpu(&bdi->completions);
  40 }
  41 EXPORT_SYMBOL(bdi_destroy);
  42
  43 static wait_queue_head_t congestion_wqh[2] = {
  44                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
  45                 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
  46         };
  47
  48
  49 void clear_bdi_congested(struct backing_dev_info *bdi, int rw)
  50 {
  51         enum bdi_state bit;
  52         wait_queue_head_t *wqh = &congestion_wqh[rw];
  53
  54         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
  55         clear_bit(bit, &bdi->state);
  56         smp_mb__after_clear_bit();
  57         if (waitqueue_active(wqh))
  58                 wake_up(wqh);
  59 }
  60 EXPORT_SYMBOL(clear_bdi_congested);
  61
  62 void set_bdi_congested(struct backing_dev_info *bdi, int rw)
  63 {
  64         enum bdi_state bit;
  65
  66         bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
  67         set_bit(bit, &bdi->state);
  68 }
  69 EXPORT_SYMBOL(set_bdi_congested);
  70
  71 /**
  72  * congestion_wait - wait for a backing_dev to become uncongested
  73  * @rw: READ or WRITE
  74  * @timeout: timeout in jiffies
  75  *
  76  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
  77  * write congestion.  If no backing_devs are congested then just wait for the
  78  * next write to be completed.
  79  */
  80 long congestion_wait(int rw, long timeout)
  81 {
  82         long ret;
  83         DEFINE_WAIT(wait);
  84         wait_queue_head_t *wqh = &congestion_wqh[rw];
  85
  86         prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
  87         ret = io_schedule_timeout(timeout);
  88         finish_wait(wqh, &wait);
  89         return ret;
  90 }
  91 EXPORT_SYMBOL(congestion_wait);
  92