[3.13.y.z extended stable] Patch "iser-target: Disable TX completion interrupt coalescing" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    iser-target: Disable TX completion interrupt coalescing

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.11.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From fad7769da1897a21a1aa7e0e38306580e9ba0762 Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab at linux-iscsi.org>
Date: Sun, 5 Oct 2014 02:13:03 -0700
Subject: iser-target: Disable TX completion interrupt coalescing

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: Kamal Mostafa <kamal 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 44b883f..9b2a108 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -1909,7 +1909,7 @@ 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");

@@ -2432,7 +2432,7 @@ 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);

 	atomic_add(wr->send_wr_num + 1, &isert_conn->post_send_buf_count);

--
1.9.1