Re: [RFC PATCH 9/9] libfc: adds queue_depth ramp up to libfc

[Christof Schmitt <christof.schmitt@de.ibm.com>]

On Wed, Aug 26, 2009 at 11:04:03AM -0700, Vasu Dev wrote:
> Increases queue_depth by one on fc_change_queue_depth call back
> with reason SCSI_QDEPTH_RAMP_UP.
> 
> Signed-off-by: Vasu Dev <vasu.dev@intel.com>
> ---
> 
>  drivers/scsi/libfc/fc_fcp.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/scsi/libfc/fc_fcp.c b/drivers/scsi/libfc/fc_fcp.c
> index dda4162..92e8a1b 100644
> --- a/drivers/scsi/libfc/fc_fcp.c
> +++ b/drivers/scsi/libfc/fc_fcp.c
> @@ -2054,6 +2054,11 @@ int fc_change_queue_depth(struct scsi_device *sdev, int qdepth, int reason)
>  	case SCSI_QDEPTH_QFULL:
>  		scsi_track_queue_full(sdev, qdepth);
>  		break;
> +	case SCSI_QDEPTH_RAMP_UP:
> +		if (qdepth + 1 <= FC_FCP_DFLT_QUEUE_DEPTH)
> +			scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev),
> +						qdepth + 1);
> +		break;
>  	default:
>  		return -EOPNOTSUPP;
>  	}

Overall the approach looks good to me.

I am trying to find out how this applies to the zfcp driver. Is the
approach in fc_change_queue_depth a good example for a driver that
does not have to adjust internal resources when changing the queue
depth?

--
Christof Schmitt