Commit f85d9f2d authored May 18, 2015 by Lars Ellenberg Committed by Jens Axboe Nov 25, 2015

drbd: fix "endless" transfer log walk in protocol A

Don't remember a DRBD request as ack_pending, if it is not.

In protocol A, we usually clear RQ_NET_PENDING at the same time we set
RQ_NET_SENT, so when deciding to remember it as ack_pending,
mod_rq_state needs to look at the current request state,
not at the previous state before the current modification was applied.

This should prevent advance_conn_req_ack_pending() from walking the full
transfer log just to find NULL in protocol A, which would cause serious
performance degradation with many "in-flight" requests, e.g. when
working via DRBD-proxy, or with a huge bandwidth-delay product.

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

parent 70644786

drivers/block/drbd/drbd_req.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -458,7 +458,7 @@ static void mod_rq_state(struct drbd_request req, struct bio_and_error m,
		atomic_add(req->i.size >> 9, &device->ap_in_flight);
		set_if_null_req_not_net_done(peer_device, req);
		}
		if (s & RQ_NET_PENDING)
		if (req->rq_state & RQ_NET_PENDING)
		set_if_null_req_ack_pending(peer_device, req);
		}