Re: [dm-devel] [PATCH] [RESEND] scsi_dh_alua: Add module parameter to allow failover to non preferred path without STPG

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Thu, 2013-04-04 at 14:54 +0000, Stewart, Sean wrote:
> Resending with requested rewording of the parameter description.
> Currently ALUA device handler sends STPG command during failover and failback.
> Failover can be optimized by implicit failover (by not to sending STPG command), when 1 is passed as hwhandler parameter in multipath.conf. ex "2 alua 1". We may need to pass the parameter through module param for alua device handler to optimize failover if incase retain_attached_hwhandler set in multipath.conf and hwhandler is set with non-tpgs device handler ex: '1 rdac'.
> 
> Signed-off-by: Vijay Chauhan <vijay.chauhan@netapp.com>
> Signed-off-by: Sean Stewart <Sean.Stewart@netapp.com>

Growl, next time don't hand edit the patch.  Humans rarely understand
patch language well enough to get it right.  I fixed it this time, but
this is the last time ...

> ---
> --- a/drivers/scsi/device_handler/scsi_dh_alua.c.orig	2013-03-27 12:18:35.000000000 +0530
> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c	2013-03-27 13:23:16.000000000 +0530
> @@ -710,6 +710,10 @@ static int alua_set_params(struct scsi_d

You actually added an extra line, so the second has to become +710,11

>  	return result;
>  }
>  
> +static uint optimize_stpg;
> +module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR); 
> +MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, 
> +rather than sending a STPG, when implicit TPGS is supported (0=No,1=Yes). Default is 0.");
> +
>  /*
>   * alua_activate - activate a path
>   * @sdev: device on the path to be activated @@ -731,6 +735,9 @@ static int alua_activate(struct scsi_dev


This is mangled, I think ...

James


>  	if (err != SCSI_DH_OK)
>  		goto out;
>  
> +	if (optimize_stpg)
> +		h->flags |= ALUA_OPTIMIZE_STPG;
> +
>  	if (h->tpgs & TPGS_MODE_EXPLICIT) {
>  		switch (h->state) {
>  		case TPGS_STATE_NONOPTIMIZED:
> --
> --
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