drbd: fix potential protocol error

Don't forget to drain the digest in case we cannot satisfy a
checksum based resync or online-verify request.

It would additionally cause a protocoll error,
dropping the connection.

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

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 93106fb92be8..c7285e16b667 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1331,6 +1331,9 @@ static int drbd_drain_block(struct drbd_conf *mdev, int data_size)
         int rr, rv = 1;
         void *data;
 
+        if (!data_size)
+                return TRUE;
+
         page = drbd_pp_alloc(mdev, 1);
 
         data = kmap(page);
@@ -1946,7 +1949,7 @@ static int receive_DataRequest(struct drbd_conf *mdev, struct p_header *h)
                             "no local data.\n");
                 drbd_send_ack_rp(mdev, h->command == P_DATA_REQUEST ? P_NEG_DREPLY :
                                  P_NEG_RS_DREPLY , p);
-                return TRUE;
+                return drbd_drain_block(mdev, h->length - brps);
         }
 
         /* GFP_NOIO, because we must not cause arbitrary write-out: in a DRBD