[PATCH 3.12 81/98] md/raid5: Compare apples to apples (or sectors to sectors)

[Jiri Slaby]

From: Jes Sorensen <Jes.Sorensen@xxxxxxxxxx>

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

===============

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@xxxxxxxxxx>
Signed-off-by: Shaohua Li <shli@xxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 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 4881851c4b42..9fbc77c6e132 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5985,8 +5985,8 @@ 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
-- 
2.8.1