Patch "scsi: megaraid_sas: Fix data integrity failure for JBOD (passthrough) devices" has been added to the 4.8-stable tree

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

scsi: megaraid_sas: Fix data integrity failure for JBOD (passthrough) devices

to the 4.8-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-megaraid_sas-fix-data-integrity-failure-for-jbod-passthrough-devices.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Kashyap Desai <[email protected]>
Date: Fri, 21 Oct 2016 06:33:32 -0700
Subject: scsi: megaraid_sas: Fix data integrity failure for JBOD (passthrough) devices

From: Kashyap Desai <[email protected]>

commit 1e793f6fc0db920400574211c48f9157a37e3945 upstream.

Commit 02b01e010afe ("megaraid_sas: return sync cache call with success") modified the driver to successfully complete SYNCHRONIZE_CACHE commands without passing them to the controller. Disk drive caches are only explicitly managed by controller firmware when operating in RAID mode. So this commit effectively disabled writeback cache flushing for any drives used in JBOD mode, leading to data integrity failures.

[mkp: clarified patch description]

---
 drivers/scsi/megaraid/megaraid_sas_base.c |   13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

@@ -1713,16 +1713,13 @@ megasas_queue_command(struct Scsi_Host *
 		goto out_done;
 	}
 
-	switch (scmd->cmnd[0]) {
-	case SYNCHRONIZE_CACHE:
-		/*
-		 * FW takes care of flush cache on its own
-		 * No need to send it down
-		 */
+	/*
+	 * FW takes care of flush cache on its own for Virtual Disk.
+	 * No need to send it down for VD. For JBOD send SYNCHRONIZE_CACHE to FW.
+	 */
+	if ((scmd->cmnd[0] == SYNCHRONIZE_CACHE) && MEGASAS_IS_LOGICAL(scmd)) {
 		scmd->result = DID_OK << 16;
 		goto out_done;
-	default:
-		break;
 	}
 
 	return instance->instancet->build_and_issue_cmd(instance, scmd);

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/scsi-megaraid_sas-fix-macro-megasas_is_logical-to-avoid-regression.patch queue-4.8/scsi-megaraid_sas-fix-data-integrity-failure-for-jbod-passthrough-devices.patch