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>

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 7907fb562388b1d7c341982808008d93bcad414c..2255dcfebd2b514d2373424718e1ad4831a0c3ab 100644 (file)
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -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);
        }