Commit 0544f549 authored by Marta Rybczynska's avatar Marta Rybczynska Committed by Christoph Hellwig
Browse files

nvme-rdma: support devices with queue size < 32 



In the case of small NVMe-oF queue size (<32) we may enter a deadlock
caused by the fact that the IB completions aren't sent waiting for 32
and the send queue will fill up.

The error is seen as (using mlx5):
[ 2048.693355] mlx5_0:mlx5_ib_post_send:3765:(pid 7273):
[ 2048.693360] nvme nvme1: nvme_rdma_post_send failed with error code -12

This patch changes the way the signaling is done so that it depends on
the queue depth now. The magic define has been removed completely.

Cc: stable@vger.kernel.org
Signed-off-by: default avatarMarta Rybczynska <marta.rybczynska@kalray.eu>
Signed-off-by: default avatarSamuel Jones <sjones@kalray.eu>
Acked-by: default avatarSagi Grimberg <sagi@grimberg.me>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 08332893

drivers/nvme/host/rdma.c

+14 −4
Original line number Diff line number Diff line
@@ -1038,6 +1038,19 @@ static void nvme_rdma_send_done(struct ib_cq *cq, struct ib_wc *wc) 
		nvme_rdma_wr_error(cq, wc, "SEND");

}



static inline int nvme_rdma_queue_sig_limit(struct nvme_rdma_queue *queue)

{

	int sig_limit;



	/*

	 * We signal completion every queue depth/2 and also handle the

	 * degenerated case of a  device with queue_depth=1, where we

	 * would need to signal every message.

	 */

	sig_limit = max(queue->queue_size / 2, 1);

	return (++queue->sig_count % sig_limit) == 0;

}



static int nvme_rdma_post_send(struct nvme_rdma_queue *queue,

		struct nvme_rdma_qe *qe, struct ib_sge *sge, u32 num_sge,

		struct ib_send_wr *first, bool flush)
@@ -1065,9 +1078,6 @@ static int nvme_rdma_post_send(struct nvme_rdma_queue *queue, 
	 * Would have been way to obvious to handle this in hardware or

	 * at least the RDMA stack..

	 *

	 * This messy and racy code sniplet is copy and pasted from the iSER

	 * initiator, and the magic '32' comes from there as well.

	 *

	 * Always signal the flushes. The magic request used for the flush

	 * sequencer is not allocated in our driver's tagset and it's

	 * triggered to be freed by blk_cleanup_queue(). So we need to
@@ -1075,7 +1085,7 @@ static int nvme_rdma_post_send(struct nvme_rdma_queue *queue, 
	 * embedded in request's payload, is not freed when __ib_process_cq()

	 * calls wr_cqe->done().

	 */

	if ((++queue->sig_count % 32) == 0 || flush)

	if (nvme_rdma_queue_sig_limit(queue) || flush)

		wr.send_flags |= IB_SEND_SIGNALED;



	if (first)

CRA Git | Maintained and supported by SUSTech CRA and CCSE