On Mon, Nov 20 2017 at 11:54am -0500,
Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
> DM appears to be the only block driver that doesn't lean on the block
> core's bio splitting. My hope is to fix that but in the meantime it
> doesn't make sense for a device that doesn't need blk_queue_split() to
> go through the associated work.
>
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> ---
> block/blk-merge.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index f5dedd5..212004c 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -186,6 +186,9 @@ void blk_queue_split(struct request_queue *q, struct bio **bio)
> struct bio *split, *res;
> unsigned nsegs;
>
> + if (!q->bio_split)
> + return;
> +
> switch (bio_op(*bio)) {
> case REQ_OP_DISCARD:
> case REQ_OP_SECURE_ERASE:
> --
> 2.10.1
>
Please ignore this patch. While the patch is perfectly valid, it
doesn't have an existing consumer. Ming pointed out that, in constrat
to blk_queue_bio(), bio-based DM's dm_make_request() makes it so that
DM never calls blk_queue_split().
Mike
