[PATCH 3.8 079/152] block: properly stack underlying max_segment_size to DM device

[Kamal Mostafa]

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

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

From: Mike Snitzer <snitzer at redhat.com>

commit d82ae52e68892338068e7559a0c0657193341ce4 upstream.

Without this patch all DM devices will default to BLK_MAX_SEGMENT_SIZE
(65536) even if the underlying device(s) have a larger value -- this is
due to blk_stack_limits() using min_not_zero() when stacking the
max_segment_size limit.

1073741824

before patch:
65536

after patch:
1073741824

Reported-by: Lukasz Flis <l.flis at cyfronet.pl>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
Signed-off-by: Jens Axboe <axboe at kernel.dk>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 block/blk-settings.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index c50ecf0..5330933 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -144,6 +144,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
 	lim->discard_zeroes_data = 1;
 	lim->max_segments = USHRT_MAX;
 	lim->max_hw_sectors = UINT_MAX;
+	lim->max_segment_size = UINT_MAX;
 	lim->max_sectors = UINT_MAX;
 	lim->max_write_same_sectors = UINT_MAX;
 }
-- 
1.8.3.2