[PATCH 3.16 045/217] md/raid5: Compare apples to apples (or sectors to sectors)

From	Ben Hutchings <ben@decadent.org.uk>
Newsgroups	linux.kernel
Subject	[PATCH 3.16 045/217] md/raid5: Compare apples to apples (or sectors to sectors)
Date	2016-04-27 02:00 +0200
Message-ID	<rsl3C-89z-57@gated-at.bofh.it> (permalink)
References	<rskqR-7Qj-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jes Sorensen <Jes.Sorensen@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@redhat.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/md/raid5.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6264,8 +6264,8 @@ 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

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[PATCH 3.16 045/217] md/raid5: Compare apples to apples (or  sectors to sectors) Ben Hutchings <ben@decadent.org.uk> - 2016-04-27 02:00 +0200

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