Re: [PATCH v2 04/12] scsi_tcq.h: Add support for multiple hardware queues

[Sagi Grimberg <sagig@dev.mellanox.co.il>]

On 10/7/2014 4:04 PM, Bart Van Assche wrote:
> Modify scsi_find_tag() and scsi_host_find_tag() such that these
> fuctions can translate a tag generated by blk_mq_unique_tag().
>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Sagi Grimberg <sagig@mellanox.com>
> ---
>   include/scsi/scsi_tcq.h | 19 +++++++++++--------
>   1 file changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/include/scsi/scsi_tcq.h b/include/scsi/scsi_tcq.h
> index e645835..ea1ca9c 100644
> --- a/include/scsi/scsi_tcq.h
> +++ b/include/scsi/scsi_tcq.h
> @@ -111,18 +111,21 @@ static inline int scsi_populate_tag_msg(struct scsi_cmnd *cmd, char *msg)
>   }
>
>   static inline struct scsi_cmnd *scsi_mq_find_tag(struct Scsi_Host *shost,
> -		unsigned int hw_ctx, int tag)
> +						 int unique_tag)
>   {
> -	struct request *req;
> +	u16 hwq = blk_mq_unique_tag_to_hwq(unique_tag);
> +	struct request *req = NULL;
>
> -	req = blk_mq_tag_to_rq(shost->tag_set.tags[hw_ctx], tag);
> +	if (hwq < shost->tag_set.nr_hw_queues)
> +		req = blk_mq_tag_to_rq(shost->tag_set.tags[hwq],
> +				       blk_mq_unique_tag_to_tag(unique_tag));
>   	return req ? (struct scsi_cmnd *)req->special : NULL;
>   }
>
>   /**
>    * scsi_find_tag - find a tagged command by device
>    * @SDpnt:	pointer to the ScSI device
> - * @tag:	the tag number
> + * @tag:	tag generated by blk_mq_unique_tag()
>    *
>    * Notes:
>    *	Only works with tags allocated by the generic blk layer.
> @@ -133,9 +136,9 @@ static inline struct scsi_cmnd *scsi_find_tag(struct scsi_device *sdev, int tag)
>
>           if (tag != SCSI_NO_TAG) {
>   		if (shost_use_blk_mq(sdev->host))
> -			return scsi_mq_find_tag(sdev->host, 0, tag);
> +			return scsi_mq_find_tag(sdev->host, tag);
>
> -        	req = blk_queue_find_tag(sdev->request_queue, tag);
> +		req = blk_queue_find_tag(sdev->request_queue, tag);

Why is this line different?

>   	        return req ? (struct scsi_cmnd *)req->special : NULL;
>   	}
>
> @@ -174,7 +177,7 @@ static inline int scsi_init_shared_tag_map(struct Scsi_Host *shost, int depth)
>   /**
>    * scsi_host_find_tag - find the tagged command by host
>    * @shost:	pointer to scsi_host
> - * @tag:	tag of the scsi_cmnd
> + * @tag:	tag generated by blk_mq_unique_tag()
>    *
>    * Notes:
>    *	Only works with tags allocated by the generic blk layer.
> @@ -186,7 +189,7 @@ static inline struct scsi_cmnd *scsi_host_find_tag(struct Scsi_Host *shost,
>
>   	if (tag != SCSI_NO_TAG) {
>   		if (shost_use_blk_mq(shost))
> -			return scsi_mq_find_tag(shost, 0, tag);
> +			return scsi_mq_find_tag(shost, tag);
>   		req = blk_map_queue_find_tag(shost->bqt, tag);
>   		return req ? (struct scsi_cmnd *)req->special : NULL;
>   	}
>