[PATCH AUTOSEL 4.18 29/88] block: allow max_discard_segments to be stacked

[Sasha Levin]

From: Mike Snitzer <snit...@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 into 
a single request")
Reviewed-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Mike Snitzer <snit...@redhat.com>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Sasha Levin <alexander.le...@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)
 
        /* Inherit limits from component devices */
        lim->max_segments = USHRT_MAX;
-       lim->max_discard_segments = 1;
+       lim->max_discard_segments = USHRT_MAX;
        lim->max_hw_sectors = UINT_MAX;
        lim->max_segment_size = UINT_MAX;
        lim->max_sectors = UINT_MAX;
-- 
2.17.1