Patch "scsi_lib: correctly retry failed zero length REQ_TYPE_FS commands" has been added to the 4.6-stable tree

This is a note to let you know that I've just added the patch titled

    scsi_lib: correctly retry failed zero length REQ_TYPE_FS commands

to the 4.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     scsi_lib-correctly-retry-failed-zero-length-req_type_fs-commands.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let [off-list ref] know about it.

From a621bac3044ed6f7ec5fa0326491b2d4838bfa93 Mon Sep 17 00:00:00 2001

From: James Bottomley <James.Bottomley@HansenPartnership.com>
Date: Fri, 13 May 2016 12:04:06 -0700
Subject: scsi_lib: correctly retry failed zero length REQ_TYPE_FS commands

From: James Bottomley <James.Bottomley@HansenPartnership.com>

commit a621bac3044ed6f7ec5fa0326491b2d4838bfa93 upstream.

When SCSI was written, all commands coming from the filesystem
(REQ_TYPE_FS commands) had data.  This meant that our signal for needing
to complete the command was the number of bytes completed being equal to
the number of bytes in the request.  Unfortunately, with the advent of
flush barriers, we can now get zero length REQ_TYPE_FS commands, which
confuse this logic because they satisfy the condition every time.  This
means they never get retried even for retryable conditions, like UNIT
ATTENTION because we complete them early assuming they're done.  Fix
this by special casing the early completion condition to recognise zero
length commands with errors and let them drop through to the retry code.

Reported-by: Sebastian Parschauer <redacted>
Signed-off-by: James E.J. Bottomley <redacted>
Tested-by: Jack Wang <redacted>
Signed-off-by: Martin K. Petersen <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/scsi/scsi_lib.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c

@@ -911,9 +911,12 @@ void scsi_io_completion(struct scsi_cmnd
 	}
 
 	/*
-	 * If we finished all bytes in the request we are done now.
+	 * special case: failed zero length commands always need to
+	 * drop down into the retry code. Otherwise, if we finished
+	 * all bytes in the request we are done now.
 	 */
-	if (!scsi_end_request(req, error, good_bytes, 0))
+	if (!(blk_rq_bytes(req) == 0 && error) &&
+	    !scsi_end_request(req, error, good_bytes, 0))
 		return;
 
 	/*

Patches currently in stable-queue which might be from James.Bottomley@HansenPartnership.com are

queue-4.6/scsi_lib-correctly-retry-failed-zero-length-req_type_fs-commands.patch