block: properly stack underlying max_segment_size to DM device

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@cyfronet.pl>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v3.3+
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-settings.c b/block/blk-settings.c
index c50ecf0ea3b17c652db8c134905de38e56713851..53309333c2f015fff6b6a7ae8a9a01700105b3e8 100644 (file)
--- 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;
 }