[Drbd-dev] [PATCH 2/2] drbd: delay resync start unless source has transferred to L_SYNC_SOURCE

[Zhang Duan]

drbd_start_resync may be rescheduled due to down_trylock failure, leaves a
state of L_WF_BITMAP_S while target state is L_SYNC_TARGET and already has
sent its resync request. Then, resync going on while the source is 
L_WF_BITMAP_S
will lead to data lose by time sequence below:

L_WF_BITMAP_S                   L_SYNC_TARGET
                                 resync request(sector A)
reply old data(A)               read & write old data(A)
new IO(A)
send oos(A)                     set oos(A)
A is at new version             resync write A done
                                 set in sync(A) but A is at old version

Signed-off-by: ZhangDuan <duan.zhang at easystack.cn>
---
  drbd/drbd_receiver.c | 9 +++++++++
  1 file changed, 9 insertions(+)

diff --git drbd/drbd_receiver.c drbd/drbd_receiver.c
index a31e44b2..7a9ce4d0 100644
--- drbd/drbd_receiver.c
+++ drbd/drbd_receiver.c
@@ -3301,6 +3301,15 @@ static int receive_DataRequest(struct 
drbd_connection *connection, struct packet
  		return ignore_remaining_packet(connection, pi->size);
  	}
  +	/* Tell target to have a retry, waiting for the rescheduled
+	 * drbd_start_resync to complete. Otherwise the concurrency
+	 * of send oos and resync may lead to a data lose. */
+	if ((pi->cmd == P_RS_DATA_REQUEST || pi->cmd == P_CSUM_RS_REQUEST) &&
+			peer_device->repl_state[NOW] == L_WF_BITMAP_S) {
+		drbd_send_ack_rp(peer_device, P_RS_CANCEL, p);
+		return ignore_remaining_packet(connection, pi->size);
+	}
+	
  	peer_req = drbd_alloc_peer_req(peer_device, GFP_TRY);
  	err = -ENOMEM;
  	if (!peer_req)
-- 
2.24.0.windows.2


-- 
Sincerely Yours,
Zhang Duan