drbd: Implemented priority inheritance for resync requests

We only issue resync requests if there is no significant application IO
going on. = Application IO has higher priority than resnyc IO.

If application IO can not be started because the resync process locked
an resync_lru entry, start the IO operations necessary to release the
lock ASAP.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 18 insertions, 4 deletions

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index ee9238e5932..0630a2e122d 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1862,10 +1862,11 @@ out_interrupted:
  * The current sync rate used here uses only the most recent two step marks,
  * to have a short time average so we can react faster.
  */
-int drbd_rs_should_slow_down(struct drbd_conf *mdev)
+int drbd_rs_should_slow_down(struct drbd_conf *mdev, sector_t sector)
 {
         struct gendisk *disk = mdev->ldev->backing_bdev->bd_contains->bd_disk;
         unsigned long db, dt, dbdt;
+        struct lc_element *tmp;
         int curr_events;
         int throttle = 0;
 
@@ -1873,9 +1874,22 @@ int drbd_rs_should_slow_down(struct drbd_conf *mdev)
         if (mdev->sync_conf.c_min_rate == 0)
                 return 0;
 
+        spin_lock_irq(&mdev->al_lock);
+        tmp = lc_find(mdev->resync, BM_SECT_TO_EXT(sector));
+        if (tmp) {
+                struct bm_extent *bm_ext = lc_entry(tmp, struct bm_extent, lce);
+                if (test_bit(BME_PRIORITY, &bm_ext->flags)) {
+                        spin_unlock_irq(&mdev->al_lock);
+                        return 0;
+                }
+                /* Do not slow down if app IO is already waiting for this extent */
+        }
+        spin_unlock_irq(&mdev->al_lock);
+
         curr_events = (int)part_stat_read(&disk->part0, sectors[0]) +
                       (int)part_stat_read(&disk->part0, sectors[1]) -
                         atomic_read(&mdev->rs_sect_ev);
+
         if (!mdev->rs_last_events || curr_events - mdev->rs_last_events > 64) {
                 unsigned long rs_left;
                 int i;
@@ -2060,9 +2074,9 @@ static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, un
          * we would also throttle its application reads.
          * In that case, throttling is done on the SyncTarget only.
          */
-        if (mdev->state.peer != R_PRIMARY && drbd_rs_should_slow_down(mdev))
-                msleep(100);
-        if (drbd_rs_begin_io(mdev, e->sector))
+        if (mdev->state.peer != R_PRIMARY && drbd_rs_should_slow_down(mdev, sector))
+                schedule_timeout_uninterruptible(HZ/10);
+        if (drbd_rs_begin_io(mdev, sector))
                 goto out_free_e;
 
 submit_for_resync: