Re: [PATCH 06/10] sd: don't use scsi_setup_blk_pc_cmnd for discard requests

[Hannes Reinecke <hare@suse.de>]

On 06/29/2014 03:34 PM, Christoph Hellwig wrote:
> Simplify handling of discard requests by setting up the command directly
> instead of initializing request fields and then calling
> scsi_setup_blk_pc_cmnd to propagate the information into the command.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   drivers/scsi/sd.c |   43 ++++++++++++++++++++++++-------------------
>   1 file changed, 24 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 25f25dd..9737e78 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -691,8 +691,10 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
>    * Will issue either UNMAP or WRITE SAME(16) depending on preference
>    * indicated by target device.
>    **/
> -static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)
> +static int sd_setup_discard_cmnd(struct scsi_cmnd *cmd)
>   {
> +	struct request *rq = cmd->request;
> +	struct scsi_device *sdp = cmd->device;
>   	struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
>   	sector_t sector = blk_rq_pos(rq);
>   	unsigned int nr_sectors = blk_rq_sectors(rq);
> @@ -704,9 +706,6 @@ static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)
>
>   	sector >>= ilog2(sdp->sector_size) - 9;
>   	nr_sectors >>= ilog2(sdp->sector_size) - 9;
> -	rq->timeout = SD_TIMEOUT;
> -
> -	memset(rq->cmd, 0, rq->cmd_len);
>
>   	page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
>   	if (!page)
> @@ -716,9 +715,9 @@ static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)
>   	case SD_LBP_UNMAP:
>   		buf = page_address(page);
>
> -		rq->cmd_len = 10;
> -		rq->cmd[0] = UNMAP;
> -		rq->cmd[8] = 24;
> +		cmd->cmd_len = 10;
> +		cmd->cmnd[0] = UNMAP;
> +		cmd->cmnd[8] = 24;
>
>   		put_unaligned_be16(6 + 16, &buf[0]);
>   		put_unaligned_be16(16, &buf[2]);
> @@ -729,23 +728,23 @@ static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)
>   		break;
>
>   	case SD_LBP_WS16:
> -		rq->cmd_len = 16;
> -		rq->cmd[0] = WRITE_SAME_16;
> -		rq->cmd[1] = 0x8; /* UNMAP */
> -		put_unaligned_be64(sector, &rq->cmd[2]);
> -		put_unaligned_be32(nr_sectors, &rq->cmd[10]);
> +		cmd->cmd_len = 16;
> +		cmd->cmnd[0] = WRITE_SAME_16;
> +		cmd->cmnd[1] = 0x8; /* UNMAP */
> +		put_unaligned_be64(sector, &cmd->cmnd[2]);
> +		put_unaligned_be32(nr_sectors, &cmd->cmnd[10]);
>
>   		len = sdkp->device->sector_size;
>   		break;
>
>   	case SD_LBP_WS10:
>   	case SD_LBP_ZERO:
> -		rq->cmd_len = 10;
> -		rq->cmd[0] = WRITE_SAME;
> +		cmd->cmd_len = 10;
> +		cmd->cmnd[0] = WRITE_SAME;
>   		if (sdkp->provisioning_mode == SD_LBP_WS10)
> -			rq->cmd[1] = 0x8; /* UNMAP */
> -		put_unaligned_be32(sector, &rq->cmd[2]);
> -		put_unaligned_be16(nr_sectors, &rq->cmd[7]);
> +			cmd->cmnd[1] = 0x8; /* UNMAP */
> +		put_unaligned_be32(sector, &cmd->cmnd[2]);
> +		put_unaligned_be16(nr_sectors, &cmd->cmnd[7]);
>
>   		len = sdkp->device->sector_size;
>   		break;
> @@ -756,8 +755,14 @@ static int sd_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)
>   	}
>
>   	rq->completion_data = page;
> +	rq->timeout = SD_TIMEOUT;
> +
>   	blk_add_request_payload(rq, page, len);
> -	ret = scsi_setup_blk_pc_cmnd(sdp, rq);
> +
> +	cmd->transfersize = len;
> +	cmd->allowed = rq->retries;
> +
> +	ret = scsi_init_io(cmd, GFP_ATOMIC);
>   	rq->__data_len = nr_bytes;
>
>   out:
Ah. Here it's done properly.

> @@ -903,7 +908,7 @@ static int sd_init_command(struct scsi_cmnd *SCpnt)
>   	 * block PC requests to make life easier.
>   	 */
>   	if (rq->cmd_flags & REQ_DISCARD) {
> -		ret = sd_setup_discard_cmnd(sdp, rq);
> +		ret = sd_setup_discard_cmnd(SCpnt);
>   		goto out;
>   	} else if (rq->cmd_flags & REQ_WRITE_SAME) {
>   		ret = sd_setup_write_same_cmnd(SCpnt);
>
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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