[dm-devel] [patch 3/3] Add retries to hp hardware handler if path initialization command completes with a check condition.

[Chandra Seetharaman]

On Thu, 2007-07-26 at 00:44 -0400, dwysocha at redhat.com wrote:
> plain text document attachment (dm-hp-sw-add-retries-handle-not-
> ready.patch)
> This patch adds retries to the hp hardware handler, and utilizes the 
> MP_RETRY flag of dm-multipath.  For now in the hp handler, if we get a 
> pg_init completed with a check condition we just assume we can retry the
> pg_init command.  We make this assumption because of incomplete data on
> specific check condition code of the HP hardware, and because testing
> has shown the HP path initialization command to be idempotent.
> The number of times we retry is settable via the "pg_init_retries"
> multipath map feature.
> 
> 
> Index: linux-2.6.23-rc1/drivers/md/dm-hp-sw.c
> ===================================================================
> --- linux-2.6.23-rc1.orig/drivers/md/dm-hp-sw.c
> +++ linux-2.6.23-rc1/drivers/md/dm-hp-sw.c
> @@ -18,6 +18,7 @@
>  #include <linux/types.h>
>  #include <scsi/scsi.h>
>  #include <scsi/scsi_cmnd.h>
> +#include <scsi/scsi_dbg.h>
> 
>  #include "dm.h"
>  #include "dm-hw-handler.h"
> @@ -26,8 +27,42 @@
> 
>  struct hp_sw_context {
>  	unsigned char sense[SCSI_SENSE_BUFFERSIZE];
> +	unsigned argc;
>  };
> 
> +/**
> + * hp_sw_error_is_retryable - Is an HP-specific check condition retryable?
> + * @req: path activation request
> + *
> + * Examine error codes of request and determine whether the error is retryable.
> + * Some error codes are already retried by scsi-ml (see
> + * scsi_decide_disposition), but some HP specific codes are not.
> + * The intent of this routine is to supply the logic for the HP specific
> + * check conditions.
> + *
> + * Returns:
> + *  1 - command completed with retryable error
> + *  0 - command completed with non-retryable error
> + *
> + * Possible optimizations
> + * 1. More hardware-specific error codes
> + */
> +static int hp_sw_error_is_retryable(struct request *req)
> +{
> +	/*
> +	 * NOT_READY is known to be retryable
> +	 * For now we just dump out the sense data and call it retryable
> +	 */
> +	if (status_byte(req->errors) == CHECK_CONDITION)
> +		__scsi_print_sense("hp_sw", req->sense, req->sense_len);
> +
> +	/*
> +	 * At this point we don't have complete information about all the error
> +	 * codes from this hardware, so we are just conservative and retry
> +	 * when in doubt.
> +	 */
> +	return 1;
> +}
> 
>  /**
>   * hp_sw_end_io - Completion handler for HP path activation.
> @@ -39,8 +74,6 @@ struct hp_sw_context {
>   *
>   * Context: scsi-ml softirq
>   *
> - * Possible optimizations
> - * 1. Actually check sense data for retryable error (e.g. NOT_READY)
>   */
>  static void hp_sw_end_io(struct request *req, int error)
>  {
> @@ -52,11 +85,17 @@ static void hp_sw_end_io(struct request 
>  		DMDEBUG("%s path activation command - success",
>  		       	path->dev->name);
>  	} else {
> -		DMWARN("path activation command on %s - error=0x%x",
> -		       path->dev->name, error);
> +		if (hp_sw_error_is_retryable(req)) {
> +			DMDEBUG("%s path activation command retry",
> +			       path->dev->name);

mixed use of space and tabs
> +			err_flags = MP_RETRY;
> +			goto out;
> +		}
> +		DMWARN("%s path activation fail - error=0x%x",
> +			path->dev->name, error);
>  		err_flags = MP_FAIL_PATH;
>  	}
> -
> + out:

space in front of label

>  	req->end_io_data = NULL;
>  	__blk_put_request(req->q, req);
>  	dm_pg_init_complete(path, err_flags);
> @@ -134,17 +173,16 @@ static void hp_sw_pg_init(struct hw_hand
>  	if (!req) {
>  		DMERR("%s path activation command allocation fail ",
>  		      path->dev->name);
> -		goto fail;
> +		goto retry;
>  	}
> 
> -	DMDEBUG("path activation command sent on %s",
> -		path->dev->name);
> +	DMDEBUG("%s path activation command sent", path->dev->name);
> 
>  	blk_execute_rq_nowait(req->q, NULL, req, 1, hp_sw_end_io);
>  	return;
> 
> - fail:
> -	dm_pg_init_complete(path, MP_FAIL_PATH);
> + retry:
> +	dm_pg_init_complete(path, MP_RETRY);
>  }
> 
>  static int hp_sw_create(struct hw_handler *hwh, unsigned argc, char **argv)
> @@ -181,7 +219,7 @@ static int __init hp_sw_init(void)
>  	if (r < 0)
>  		DMERR("register failed %d", r);
>  	else
> -		DMINFO("version 0.0.2 loaded");
> +		DMINFO("version 0.0.3 loaded");
> 
>  	return r;
>  }
> 
-- 

----------------------------------------------------------------------
    Chandra Seetharaman               | Be careful what you choose....
              - sekharan at us.ibm.com   |      .......you may get it.
----------------------------------------------------------------------