[3.19.y-ckt stable] Patch "md/raid5: Compare apples to apples (or sectors to sectors)" has been added to the 3.19.y-ckt tree

[Kamal Mostafa]

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

    md/raid5: Compare apples to apples (or sectors to sectors)

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt18.

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

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 494e9feb6997e3e84a26904458a9a08b7ddd96ac Mon Sep 17 00:00:00 2001
From: Jes Sorensen <Jes.Sorensen at redhat.com>
Date: Tue, 16 Feb 2016 16:44:24 -0500
Subject: md/raid5: Compare apples to apples (or sectors to sectors)

commit e7597e69dec59b65c5525db1626b9d34afdfa678 upstream.

'max_discard_sectors' is in sectors, while 'stripe' is in bytes.

This fixes the problem where DISCARD would get disabled on some larger
RAID5 configurations (6 or more drives in my testing), while it worked
as expected with smaller configurations.

Fixes: 620125f2bf8 ("MD: raid5 trim support")
Signed-off-by: Jes Sorensen <Jes.Sorensen at redhat.com>
Signed-off-by: Shaohua Li <shli at fb.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/md/raid5.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 5fa7549..cdd8770 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6245,8 +6245,8 @@ static int run(struct mddev *mddev)
 		}

 		if (discard_supported &&
-		   mddev->queue->limits.max_discard_sectors >= stripe &&
-		   mddev->queue->limits.discard_granularity >= stripe)
+		    mddev->queue->limits.max_discard_sectors >= (stripe >> 9) &&
+		    mddev->queue->limits.discard_granularity >= stripe)
 			queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
 						mddev->queue);
 		else
--
2.7.4