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Commit 4eb9b3cb authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Philipp Reisner
Browse files

drbd: don't send out P_BARRIER with stale information 



We must only send P_BARRIER for epochs we actually sent P_DATA in.

If we (re-)establish a connection, we reinitialized the
send.current_epoch_nr, but forgot to reset send.current_epoch_writes.

This could result in a spurious P_BARRIER with stale epoch information,
and a disconnect/reconnect cycle once the then "unexpected"
P_BARRIER_ACK is received:
  BAD! BarrierAck #28823 received, expected #28829!

Introduce re_init_if_first_write() and maybe_send_barrier() helpers,
and call them appropriately for read/write/set-out-of-sync requests.

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent 08332d73

drivers/block/drbd/drbd_worker.c

+25 −24
Original line number Diff line number Diff line
@@ -1265,6 +1265,27 @@ int w_send_write_hint(struct drbd_work *w, int cancel) 
	return drbd_send_command(mdev, sock, P_UNPLUG_REMOTE, 0, NULL, 0);

}



static void re_init_if_first_write(struct drbd_tconn *tconn, unsigned int epoch)

{

	if (!tconn->send.seen_any_write_yet) {

		tconn->send.seen_any_write_yet = true;

		tconn->send.current_epoch_nr = epoch;

		tconn->send.current_epoch_writes = 0;

	}

}



static void maybe_send_barrier(struct drbd_tconn *tconn, unsigned int epoch)

{

	/* re-init if first write on this connection */

	if (!tconn->send.seen_any_write_yet)

		return;

	if (tconn->send.current_epoch_nr != epoch) {

		if (tconn->send.current_epoch_writes)

			drbd_send_barrier(tconn);

		tconn->send.current_epoch_nr = epoch;

	}

}



int w_send_out_of_sync(struct drbd_work *w, int cancel)

{

	struct drbd_request *req = container_of(w, struct drbd_request, w);
@@ -1277,19 +1298,11 @@ int w_send_out_of_sync(struct drbd_work *w, int cancel) 
		return 0;

	}



	if (!tconn->send.seen_any_write_yet) {

		tconn->send.seen_any_write_yet = true;

		tconn->send.current_epoch_nr = req->epoch;

	}

	if (tconn->send.current_epoch_nr != req->epoch) {

		if (tconn->send.current_epoch_writes)

			drbd_send_barrier(tconn);

		tconn->send.current_epoch_nr = req->epoch;

	}

	/* this time, no tconn->send.current_epoch_writes++;

	 * If it was sent, it was the closing barrier for the last

	 * replicated epoch, before we went into AHEAD mode.

	 * No more barriers will be sent, until we leave AHEAD mode again. */

	maybe_send_barrier(tconn, req->epoch);



	err = drbd_send_out_of_sync(mdev, req);

	req_mod(req, OOS_HANDED_TO_NETWORK);
@@ -1315,15 +1328,8 @@ int w_send_dblock(struct drbd_work *w, int cancel) 
		return 0;

	}



	if (!tconn->send.seen_any_write_yet) {

		tconn->send.seen_any_write_yet = true;

		tconn->send.current_epoch_nr = req->epoch;

	}

	if (tconn->send.current_epoch_nr != req->epoch) {

		if (tconn->send.current_epoch_writes)

			drbd_send_barrier(tconn);

		tconn->send.current_epoch_nr = req->epoch;

	}

	re_init_if_first_write(tconn, req->epoch);

	maybe_send_barrier(tconn, req->epoch);

	tconn->send.current_epoch_writes++;



	err = drbd_send_dblock(mdev, req);
@@ -1352,12 +1358,7 @@ int w_send_read_req(struct drbd_work *w, int cancel) 


	/* Even read requests may close a write epoch,

	 * if there was any yet. */

	if (tconn->send.seen_any_write_yet &&

	    tconn->send.current_epoch_nr != req->epoch) {

		if (tconn->send.current_epoch_writes)

			drbd_send_barrier(tconn);

		tconn->send.current_epoch_nr = req->epoch;

	}

	maybe_send_barrier(tconn, req->epoch);



	err = drbd_send_drequest(mdev, P_DATA_REQUEST, req->i.sector, req->i.size,

				 (unsigned long)req);