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, 2 insertions, 2 deletions

diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 33f6cc537d08..28f85d950781 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -182,6 +182,7 @@ static struct lc_element *_al_get(struct drbd_conf *mdev, unsigned int enr)
         if (unlikely(tmp != NULL)) {
                 struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
                 if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {
+                        set_bit(BME_PRIORITY, &bm_ext->flags);
                         spin_unlock_irq(&mdev->al_lock);
                         return NULL;
                 }
@@ -1297,8 +1298,7 @@ void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector)
         }
 
         if (lc_put(mdev->resync, &bm_ext->lce) == 0) {
-                clear_bit(BME_LOCKED, &bm_ext->flags);
-                clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                bm_ext->flags = 0; /* clear BME_LOCKED, BME_NO_WRITES and BME_PRIORITY */
                 mdev->resync_locked--;
                 wake_up(&mdev->al_wait);
         }