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

[Chandra Seetharaman]

Looks good.

Acked by: Chandra Seetharaman <sekharan at us.ibm.com>

On Mon, 2007-07-30 at 15:10 -0400, Dave Wysochanski wrote:
> On Thu, 2007-07-26 at 12:19 -0700, Chandra Seetharaman wrote:
> > 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;
> > >  }
> > > 
> 
> Attached should fix the whitespace issues mentioned.
> 
> 
-- 

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