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From:   Sasha Levin <Alexander.Levin@microsoft.com>
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CC:     Mike Snitzer <snitzer@redhat.com>, Jens Axboe <axboe@kernel.dk>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.18 29/88] block: allow max_discard_segments to be
 stacked
Thread-Topic: [PATCH AUTOSEL 4.18 29/88] block: allow max_discard_segments to
 be stacked
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Date:   Fri, 7 Sep 2018 00:36:12 +0000
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From: Mike Snitzer <snitzer@redhat.com>

[ Upstream commit 42c9cdfe1e11e083dceb0f0c4977b758cf7403b9 ]

Set max_discard_segments to USHRT_MAX in blk_set_stacking_limits() so
that blk_stack_limits() can stack up this limit for stacked devices.

before:

$ cat /sys/block/nvme0n1/queue/max_discard_segments
256
$ cat /sys/block/dm-0/queue/max_discard_segments
1

after:

$ cat /sys/block/nvme0n1/queue/max_discard_segments
256
$ cat /sys/block/dm-0/queue/max_discard_segments
256

Fixes: 1e739730c5b9e ("block: optionally merge discontiguous discard bios i=
nto a single request")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 block/blk-settings.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index d1de71124656..24fff4a3d08a 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -128,7 +128,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
=20
 	/* Inherit limits from component devices */
 	lim->max_segments =3D USHRT_MAX;
-	lim->max_discard_segments =3D 1;
+	lim->max_discard_segments =3D USHRT_MAX;
 	lim->max_hw_sectors =3D UINT_MAX;
 	lim->max_segment_size =3D UINT_MAX;
 	lim->max_sectors =3D UINT_MAX;
--=20
2.17.1