[SPDK] RDMA QP leak on spdk nvmf target

[Potnuri Bharat Teja <bharat at chelsio.com>]

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Hi All,
With recent spdk code, RDMA QPs are not destroyed on the nvmf target after each 
spdk perf run until target is cleared/stopped.

SPDK nvmf target is using drain WR completion logic to destroy the RDMA QP. But 
even after send/recv drain completions are received RDMA QP is not destroyed as 
the rqpair->refcnt is 0 in spdk_nvmf_rdma_qpair_destroy().

I believe rqpair refcnt needs to be incremented before spdk_nvmf_rdma_qpair_destroy().
Here is my experimental patch that fixes the issue, Please let me know if this 
qualifies for a patch.
--- a/lib/nvmf/rdma.c
+++ b/lib/nvmf/rdma.c
@@ -2586,9 +2595,10 @@ spdk_nvmf_rdma_poller_poll(struct spdk_nvmf_rdma_transport *rtransport,
	case RDMA_WR_TYPE_DRAIN_RECV:
		rqpair = SPDK_CONTAINEROF(rdma_wr, struct spdk_nvmf_rdma_qpair, drain_recv_wr);
		assert(rqpair->disconnect_flags & RDMA_QP_DISCONNECTING);
		SPDK_DEBUGLOG(SPDK_LOG_RDMA, "Drained QP RECV %u (%p)\n", rqpair->qpair.qid, rqpair);
		              rqpair->disconnect_flags |= RDMA_QP_RECV_DRAINED;
		if (rqpair->disconnect_flags & RDMA_QP_SEND_DRAINED) {
+			spdk_nvmf_rdma_qpair_inc_refcnt(rqpair);
			spdk_nvmf_rdma_qpair_destroy(rqpair);
		}
		/* Continue so that this does not trigger the disconnect path below. */
@@ -2596,9 +2606,10 @@ spdk_nvmf_rdma_poller_poll(struct spdk_nvmf_rdma_transport *rtransport,
	case RDMA_WR_TYPE_DRAIN_SEND:
		rqpair = SPDK_CONTAINEROF(rdma_wr, struct spdk_nvmf_rdma_qpair, drain_send_wr);
		assert(rqpair->disconnect_flags & RDMA_QP_DISCONNECTING);
		SPDK_DEBUGLOG(SPDK_LOG_RDMA, "Drained QP SEND %u (%p)\n", rqpair->qpair.qid, rqpair);
		              rqpair->disconnect_flags |= RDMA_QP_SEND_DRAINED;
		if (rqpair->disconnect_flags & RDMA_QP_RECV_DRAINED) {
+			spdk_nvmf_rdma_qpair_inc_refcnt(rqpair);
			spdk_nvmf_rdma_qpair_destroy(rqpair);
		}
		/* Continue so that this does not trigger the disconnect path below. */
----

Thanks,
Bharat.