[PATCH 3.16.y-ckt 021/170] iser-target: Disable TX completion interrupt coalescing

[Luis Henriques]

3.16.7-ckt1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Bellinger <nab at linux-iscsi.org>

commit 0d0f660d882c1c02748ced13966a2413aa5d6cc2 upstream.

This patch explicitly disables TX completion interrupt coalescing logic
in isert_put_response() and isert_put_datain() that was originally added
as an efficiency optimization in commit 95b60f07.

It has been reported that this change can trigger ABORT_TASK timeouts
under certain small block workloads, where disabling coalescing was
required for stability.  According to Sagi, this doesn't impact
overall performance, so go ahead and disable it for now.

Reported-by: Moussa Ba <moussaba at micron.com>
Reported-by: Sagi Grimberg <sagig at dev.mellanox.co.il>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/infiniband/ulp/isert/ib_isert.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
index 9959cd1faad9..676013a9dd94 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -2183,7 +2183,7 @@ isert_put_response(struct iscsi_conn *conn, struct iscsi_cmd *cmd)
 		isert_cmd->tx_desc.num_sge = 2;
 	}
 
-	isert_init_send_wr(isert_conn, isert_cmd, send_wr, true);
+	isert_init_send_wr(isert_conn, isert_cmd, send_wr, false);
 
 	pr_debug("Posting SCSI Response IB_WR_SEND >>>>>>>>>>>>>>>>>>>>>>\n");
 
@@ -2882,7 +2882,7 @@ isert_put_datain(struct iscsi_conn *conn, struct iscsi_cmd *cmd)
 				     &isert_cmd->tx_desc.iscsi_header);
 		isert_init_tx_hdrs(isert_conn, &isert_cmd->tx_desc);
 		isert_init_send_wr(isert_conn, isert_cmd,
-				   &isert_cmd->tx_desc.send_wr, true);
+				   &isert_cmd->tx_desc.send_wr, false);
 		isert_cmd->rdma_wr.s_send_wr.next = &isert_cmd->tx_desc.send_wr;
 		wr->send_wr_num += 1;
 	}
-- 
2.1.0