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.
Signed-off-by: Marta Rybczynska <marta.rybczynska@xxxxxxxxx>
Signed-off-by: Samuel Jones <sjones@xxxxxxxxx>
---
Changes from v1:
* signal by queue size/2, remove hardcoded 32
* support queue depth of 1
drivers/nvme/host/rdma.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 47a479f..4de1b92 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -1029,6 +1029,18 @@ static void nvme_rdma_send_done(struct ib_cq *cq, struct ib_wc *wc)
nvme_rdma_wr_error(cq, wc, "SEND");
}
+static inline nvme_rdma_queue_sig_limit(struct nvme_rdma_queue *queue)
+{
+ int sig_limit;
+
+ /* We signal completion every queue depth/2 and also
+ * handle the case of possible 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)
@@ -1056,9 +1068,6 @@ 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
@@ -1066,7 +1075,7 @@ 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)
--
1.8.3.1
--
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