iser-target: avoid posting a recv buffer twice

We pre-allocate our send-queues and might overflow them
in case we have multi work-request operations which tend
to occur for large RDMA transfers over devices with limited
allowed sg elements. When we get to a queue-full condition
we might retry again later, so track our receive buffers
so we don't repost them for a retry case.
Reported-by: Potnuri Bharat Teja <bharat@chelsio.com>
Tested-by: Potnuri Bharat Teja <bharat@chelsio.com>
Reviewed-by: Potnuri Bharat Teja <bharat@chelsio.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/infiniband/ulp/isert/ib_isert.c

@@ -817,6 +817,7 @@ isert_post_recvm(struct isert_conn *isert_conn, u32 count)
 		rx_wr->sg_list = &rx_desc->rx_sg;
 		rx_wr->num_sge = 1;
 		rx_wr->next = rx_wr + 1;
+		rx_desc->in_use = false;
 	}
 	rx_wr--;
 	rx_wr->next = NULL; /* mark end of work requests list */
@@ -835,6 +836,15 @@ isert_post_recv(struct isert_conn *isert_conn, struct iser_rx_desc *rx_desc)
 	struct ib_recv_wr *rx_wr_failed, rx_wr;
 	int ret;
 
+	if (!rx_desc->in_use) {
+		/*
+		 * if the descriptor is not in-use we already reposted it
+		 * for recv, so just silently return
+		 */
+		return 0;
+	}
+
+	rx_desc->in_use = false;
 	rx_wr.wr_cqe = &rx_desc->rx_cqe;
 	rx_wr.sg_list = &rx_desc->rx_sg;
 	rx_wr.num_sge = 1;
@@ -1397,6 +1407,8 @@ isert_recv_done(struct ib_cq *cq, struct ib_wc *wc)
 		return;
 	}
 
+	rx_desc->in_use = true;
+
 	ib_dma_sync_single_for_cpu(ib_dev, rx_desc->dma_addr,
 			ISER_RX_PAYLOAD_SIZE, DMA_FROM_DEVICE);
 

drivers/infiniband/ulp/isert/ib_isert.h

@@ -60,7 +60,7 @@
 
 #define ISER_RX_PAD_SIZE	(ISCSI_DEF_MAX_RECV_SEG_LEN + 4096 - \
 		(ISER_RX_PAYLOAD_SIZE + sizeof(u64) + sizeof(struct ib_sge) + \
-		 sizeof(struct ib_cqe)))
+		 sizeof(struct ib_cqe) + sizeof(bool)))
 
 #define ISCSI_ISER_SG_TABLESIZE		256
 
@@ -85,6 +85,7 @@ struct iser_rx_desc {
 	u64		dma_addr;
 	struct ib_sge	rx_sg;
 	struct ib_cqe	rx_cqe;
+	bool		in_use;
 	char		pad[ISER_RX_PAD_SIZE];
 } __packed;