[PATCH 3.13.y-ckt 20/97] md/raid5: Compare apples to apples (or sectors to sectors)

[Kamal Mostafa]

3.13.11-ckt38 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jes Sorensen <Jes.Sorensen at redhat.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 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 bd9f959..c96e0a6 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6171,8 +6171,8 @@ 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