Re: [PATCH] dm mpath: delay retry activate_path on SCSI_DH_RETRY

[Chandra Seetharaman <sekharan@us.ibm.com>]

On Thu, 2009-02-19 at 12:40 +0530, Nikanth Karthikesan wrote:

<snip>

> @@ -431,6 +432,7 @@ static void process_queued_ios(struct work_struct *work)
>  	struct pgpath *pgpath = NULL;
>  	unsigned init_required = 0, must_queue = 1;
>  	unsigned long flags;
> +	unsigned long delay = 0;

I do not see the reason for this variable, you can as well put the delay
in pg_init_delay and use it directly (and set it to zero after using
it) ?
> 
>  	spin_lock_irqsave(&m->lock, flags);
> 
> @@ -452,13 +454,15 @@ static void process_queued_ios(struct work_struct *work)
>  		m->pg_init_required = 0;
>  		m->pg_init_in_progress = 1;
>  		init_required = 1;
> +		if (m->pg_init_delay)
> +			delay = SCSI_DH_RETRY_DELAY;
>  	}
> 
>  out:
>  	spin_unlock_irqrestore(&m->lock, flags);
> 
>  	if (init_required)
> -		queue_work(kmpath_handlerd, &m->activate_path);
> +		queue_delayed_work(kmpath_handlerd, &m->activate_path, delay);
> 
>  	if (!must_queue)
>  		dispatch_queued_ios(m);
> @@ -1060,6 +1064,7 @@ static void pg_init_done(struct dm_path *path, int errors)
>  	struct priority_group *pg = pgpath->pg;
>  	struct multipath *m = pg->m;
>  	unsigned long flags;
> +	unsigned delay = 0;

You can get rid of this variable also and set it directly under
SCSI_DH_RETRY.
> 
>  	/* device or driver problems */
>  	switch (errors) {
> @@ -1084,8 +1089,11 @@ static void pg_init_done(struct dm_path *path, int errors)
>  		 */
>  		bypass_pg(m, pg, 1);
>  		break;
> -	/* TODO: For SCSI_DH_RETRY we should wait a couple seconds */
> +	/*
> +	 * For SCSI_DH_RETRY we wait before retrying.
> +	 */
>  	case SCSI_DH_RETRY:
> +		delay = 1;
>  	case SCSI_DH_IMM_RETRY:
>  	case SCSI_DH_RES_TEMP_UNAVAIL:
>  		if (pg_init_limit_reached(m, pgpath))
> @@ -1112,6 +1120,7 @@ static void pg_init_done(struct dm_path *path, int errors)
>  	}
> 
>  	m->pg_init_in_progress = 0;
> +	m->pg_init_delay = delay;
>  	queue_work(kmultipathd, &m->process_queued_ios);
>  	spin_unlock_irqrestore(&m->lock, flags);
>  }
> @@ -1120,7 +1129,7 @@ static void activate_path(struct work_struct *work)
>  {
>  	int ret;
>  	struct multipath *m =
> -		container_of(work, struct multipath, activate_path);
> +		container_of(work, struct multipath, activate_path.work);
>  	struct dm_path *path;
>  	unsigned long flags;
> 
> diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
> index 33efce2..f099d86 100644
> --- a/include/scsi/scsi_dh.h
> +++ b/include/scsi/scsi_dh.h
> @@ -55,6 +55,10 @@ enum {
>  	SCSI_DH_NOSYS,
>  	SCSI_DH_DRIVER_MAX,
>  };
> +
> +/* Time to wait before retry in case of SCSI_DH_RETRY */
> +#define SCSI_DH_RETRY_DELAY ((HZ * 2))
> +
>  #if defined(CONFIG_SCSI_DH) || defined(CONFIG_SCSI_DH_MODULE)
>  extern int scsi_dh_activate(struct request_queue *);
>  extern int scsi_dh_handler_exist(const char *);
>