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

[ Upstream commit e7597e69dec59b65c5525db1626b9d34afdfa678 ]

'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")
Cc: stable@vger.kernel.org v3.7+
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 5fa7549ba409d29ca90053981347b2e79522185c..cdd8770de1c236d4564ad9483a8cb56df0db1a9c 100644 (file)
--- 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