[ 3.8.y.z extended stable ] Patch "md/raid1, 5, 10: Disable WRITE SAME until a recovery strategy is in" has been added to staging queue

[Kamal Mostafa]

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

    md/raid1,5,10: Disable WRITE SAME until a recovery strategy is in

to the linux-3.8.y-queue branch of the 3.8.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-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.3.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 30410bc50edf2acad3ad3fefe5f49021e0f24b79 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa at zytor.com>
Date: Wed, 12 Jun 2013 07:37:43 -0700
Subject: md/raid1,5,10: Disable WRITE SAME until a recovery strategy is in
 place

commit 5026d7a9b2f3eb1f9bda66c18ac6bc3036ec9020 upstream.

There are cases where the kernel will believe that the WRITE SAME
command is supported by a block device which does not, in fact,
support WRITE SAME.  This currently happens for SATA drivers behind a
SAS controller, but there are probably a hundred other ways that can
happen, including drive firmware bugs.

After receiving an error for WRITE SAME the block layer will retry the
request as a plain write of zeroes, but mdraid will consider the
failure as fatal and consider the drive failed.  This has the effect
that all the mirrors containing a specific set of data are each
offlined in very rapid succession resulting in data loss.

However, just bouncing the request back up to the block layer isn't
ideal either, because the whole initial request-retry sequence should
be inside the write bitmap fence, which probably means that md needs
to do its own conversion of WRITE SAME to write zero.

Until the failure scenario has been sorted out, disable WRITE SAME for
raid1, raid5, and raid10.

[neilb: added raid5]

This patch is appropriate for any -stable since 3.7 when write_same
support was added.

Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>
Signed-off-by: NeilBrown <neilb at suse.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/md/raid1.c  | 4 ++--
 drivers/md/raid10.c | 3 +--
 drivers/md/raid5.c  | 4 +++-
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 3dab5bb..7116798 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -2837,8 +2837,8 @@ static int run(struct mddev *mddev)
 		return PTR_ERR(conf);

 	if (mddev->queue)
-		blk_queue_max_write_same_sectors(mddev->queue,
-						 mddev->chunk_sectors);
+		blk_queue_max_write_same_sectors(mddev->queue, 0);
+
 	rdev_for_each(rdev, mddev) {
 		if (!mddev->gendisk)
 			continue;
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index fa1e11c..2f4be3c 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3588,8 +3588,7 @@ static int run(struct mddev *mddev)
 	if (mddev->queue) {
 		blk_queue_max_discard_sectors(mddev->queue,
 					      mddev->chunk_sectors);
-		blk_queue_max_write_same_sectors(mddev->queue,
-						 mddev->chunk_sectors);
+		blk_queue_max_write_same_sectors(mddev->queue, 0);
 		blk_queue_io_min(mddev->queue, chunk_size);
 		if (conf->geo.raid_disks % conf->geo.near_copies)
 			blk_queue_io_opt(mddev->queue, chunk_size * conf->geo.raid_disks);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 94ce78e..9a6ff72 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5494,7 +5494,7 @@ static int run(struct mddev *mddev)
 		if (mddev->major_version == 0 &&
 		    mddev->minor_version > 90)
 			rdev->recovery_offset = reshape_offset;
-
+
 		if (rdev->recovery_offset < reshape_offset) {
 			/* We need to check old and new layout */
 			if (!only_parity(rdev->raid_disk,
@@ -5617,6 +5617,8 @@ static int run(struct mddev *mddev)
 		 */
 		mddev->queue->limits.discard_zeroes_data = 0;

+		blk_queue_max_write_same_sectors(mddev->queue, 0);
+
 		rdev_for_each(rdev, mddev) {
 			disk_stack_limits(mddev->gendisk, rdev->bdev,
 					  rdev->data_offset << 9);
--
1.8.1.2