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, 5 insertions, 13 deletions

diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 982d68432a0..4008130f2b2 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -355,7 +355,7 @@ static int read_for_csum(struct drbd_conf *mdev, sector_t sector, int size)
         if (!get_ldev(mdev))
                 return -EIO;
 
-        if (drbd_rs_should_slow_down(mdev))
+        if (drbd_rs_should_slow_down(mdev, sector))
                 goto defer;
 
         /* GFP_TRY, because if there is no memory available right now, this may
@@ -503,16 +503,6 @@ int drbd_rs_number_requests(struct drbd_conf *mdev)
                 number = SLEEP_TIME * mdev->c_sync_rate  / ((BM_BLOCK_SIZE / 1024) * HZ);
         }
 
-        /* Throttle resync on lower level disk activity, which may also be
-         * caused by application IO on Primary/SyncTarget.
-         * Keep this after the call to drbd_rs_controller, as that assumes
-         * to be called as precisely as possible every SLEEP_TIME,
-         * and would be confused otherwise. */
-        if (number && drbd_rs_should_slow_down(mdev)) {
-                mdev->c_sync_rate = 1;
-                number = 0;
-        }
-
         /* ignore the amount of pending requests, the resync controller should
          * throttle down to incoming reply rate soon enough anyways. */
         return number;
@@ -594,7 +584,8 @@ next_sector:
 
                 sector = BM_BIT_TO_SECT(bit);
 
-                if (drbd_try_rs_begin_io(mdev, sector)) {
+                if (drbd_rs_should_slow_down(mdev, sector) ||
+                    drbd_try_rs_begin_io(mdev, sector)) {
                         mdev->bm_resync_fo = bit;
                         goto requeue;
                 }
@@ -719,7 +710,8 @@ static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int ca
 
                 size = BM_BLOCK_SIZE;
 
-                if (drbd_try_rs_begin_io(mdev, sector)) {
+                if (drbd_rs_should_slow_down(mdev, sector) ||
+                    drbd_try_rs_begin_io(mdev, sector)) {
                         mdev->ov_position = sector;
                         goto requeue;
                 }