linux-kernel - [PATCH 3.19.y-ckt 045/170] md/raid5: Compare apples to apples (or sectors to sectors)

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Date:	Fri,  1 Apr 2016 17:52:11 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jes Sorensen <Jes.Sorensen@...hat.com>, Shaohua Li <shli@...com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 045/170] md/raid5: Compare apples to apples (or sectors to sectors)

3.19.8-ckt18 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jes Sorensen <Jes.Sorensen@...hat.com>

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@...hat.com>
Signed-off-by: Shaohua Li <shli@...com>
Signed-off-by: Kamal Mostafa <kamal@...onical.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