[PATCH 4/6] scsi-mq: init sg in scsi_init_io.

[PATCH 4/6] scsi-mq: init sg in scsi_init_io.

[majianpeng]

Make scsi-mq support blk-pc-command.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
---
 drivers/scsi/scsi_lib.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index bed596e..679e840 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1059,9 +1059,11 @@ int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
 	/*
 	 * Use pre-allocation of cmd->sdb scatterlists with scsi-mq..
 	 */
-//FIXME: scsi-mq dif descriptor init within scsi_init_io
 	if (rq->mq_ctx) {
 		BUG_ON(rq->nr_phys_segments > SCSI_MAX_SG_SEGMENTS);
+		cmd->sdb.table.sgl = cmd->mq_sgl;
+		cmd->sdb.table.nents = rq->nr_phys_segments;
+		sg_init_table(cmd->sdb.table.sgl, rq->nr_phys_segments);
 		scsi_init_sgtable(rq, &cmd->sdb);
 		return BLKPREP_OK;
 	}
-- 
1.7.10.4

Re: [PATCH 4/6] scsi-mq: init sg in scsi_init_io.

[Nicholas A. Bellinger]

On Fri, 2013-11-29 at 16:42 +0800, majianpeng wrote:
> Make scsi-mq support blk-pc-command.
> 
> Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
> ---
>  drivers/scsi/scsi_lib.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index bed596e..679e840 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1059,9 +1059,11 @@ int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
>  	/*
>  	 * Use pre-allocation of cmd->sdb scatterlists with scsi-mq..
>  	 */
> -//FIXME: scsi-mq dif descriptor init within scsi_init_io
>  	if (rq->mq_ctx) {
>  		BUG_ON(rq->nr_phys_segments > SCSI_MAX_SG_SEGMENTS);
> +		cmd->sdb.table.sgl = cmd->mq_sgl;
> +		cmd->sdb.table.nents = rq->nr_phys_segments;
> +		sg_init_table(cmd->sdb.table.sgl, rq->nr_phys_segments);
>  		scsi_init_sgtable(rq, &cmd->sdb);
>  		return BLKPREP_OK;
>  	}

Doesn't seem to be necessary for TYPE_ROM either..?

So requests of REQ_TYPE_BLOCK_PC for TYPE_ROM with scsi-mq are having
their sc->sdb.table setup from pre-allocated SGLs at the start of
scsi_mq_queue_rq(), before q->prep_rq_fn() -> sr_prep_fn() ->
scsi_setup_blk_pc_cmnd() is called.

--nab