Re: [PATCH v2 2/3] nvme-rdma: don't complete requests before a send work request has completed

[Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>]

Btw, I think we can avoid 2 atomic ops for the remote invalidation
path with a simple update like the one below:


diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 5627d81735d2..2032cd8ad431 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -1141,7 +1141,6 @@ static int nvme_rdma_map_sg_fr(struct nvme_rdma_queue *queue,
 			     IB_ACCESS_REMOTE_WRITE;
 
 	req->mr->need_inval = true;
-	atomic_inc(&req->ref);
 
 	sg->addr = cpu_to_le64(req->mr->iova);
 	put_unaligned_le24(req->mr->length, sg->length);
@@ -1328,10 +1327,9 @@ static int nvme_rdma_process_nvme_rsp(struct nvme_rdma_queue *queue,
 	req->cqe.status = cqe->status;
 	req->cqe.result = cqe->result;
 
-	if ((wc->wc_flags & IB_WC_WITH_INVALIDATE) &&
-	    wc->ex.invalidate_rkey == req->mr->rkey) {
-		atomic_dec(&req->ref);
-	} else if (req->mr->need_inval) {
+	if (req->mr->need_inval &&
+	    (!(wc->wc_flags & IB_WC_WITH_INVALIDATE) ||
+	     wc->ex.invalidate_rkey != req->mr->rkey)) {
 		ret = nvme_rdma_inv_rkey(queue, req);
 		if (unlikely(ret < 0)) {
 			dev_err(queue->ctrl->ctrl.device,
@@ -1339,12 +1337,12 @@ static int nvme_rdma_process_nvme_rsp(struct nvme_rdma_queue *queue,
 				req->mr->rkey, ret);
 			nvme_rdma_error_recovery(queue->ctrl);
 		}
-	}
-
-	if (atomic_dec_and_test(&req->ref)) {
-		if (rq->tag == tag)
-			ret = 1;
-		nvme_end_request(rq, req->cqe.status, req->cqe.result);
+	} else {
+		if (atomic_dec_and_test(&req->ref)) {
+			if (rq->tag == tag)
+				ret = 1;
+			nvme_end_request(rq, req->cqe.status, req->cqe.result);
+		}
 	}
 
 	return ret;
--
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