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

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

[Stewart, Sean]

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>

---
--- 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
 	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
 	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:
--

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

[James Bottomley]

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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