2013-10-18 14:23:36

by Mike Snitzer

Subject: [PATCH] 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.

# cat /sys/block/sda/queue/max_segment_size
1073741824

# cat /sys/block/dm-0/queue/max_segment_size
before patch:
65536

after patch:
1073741824

Reported-by: Lukasz Flis <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Cc: [email protected] # v3.3+
---
block/blk-settings.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index c50ecf0..29f28bb 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -143,6 +143,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
/* Inherit limits from component devices */
lim->discard_zeroes_data = 1;
lim->max_segments = USHRT_MAX;
+ lim->max_segment_size = UINT_MAX;
lim->max_hw_sectors = UINT_MAX;
lim->max_sectors = UINT_MAX;
lim->max_write_same_sectors = UINT_MAX;
--
1.7.4.4

2013-10-18 15:46:16

by Jens Axboe

Subject: Re: [PATCH] block: properly stack underlying max_segment_size to DM device

On Fri, Oct 18 2013, Mike Snitzer wrote:
> 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.
>
> # cat /sys/block/sda/queue/max_segment_size
> 1073741824
>
> # cat /sys/block/dm-0/queue/max_segment_size
> before patch:
> 65536
>
> after patch:
> 1073741824
>
> Reported-by: Lukasz Flis <[email protected]>
> Signed-off-by: Mike Snitzer <[email protected]>
> Cc: [email protected] # v3.3+
> ---
> block/blk-settings.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index c50ecf0..29f28bb 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -143,6 +143,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
> /* Inherit limits from component devices */
> lim->discard_zeroes_data = 1;
> lim->max_segments = USHRT_MAX;
> + lim->max_segment_size = UINT_MAX;
> lim->max_hw_sectors = UINT_MAX;
> lim->max_sectors = UINT_MAX;
> lim->max_write_same_sectors = UINT_MAX;

Thanks, applied for 3.13.

--
Jens Axboe