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

[Dave Wysochanski]

On Mon, 2007-07-30 at 16:08 -0500, Mike Christie wrote:
> 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.
> > 
> 
> That seems more odd with the other code. Please do not just use tabs for 
> spacing on those places. Keep it consistent with the rest of the dm code.
> 

Ok - see attached.


-------------- next part --------------
A non-text attachment was scrubbed...
Name: dm-hp-sw-add-retries-handle-not-ready.patch
Type: text/x-patch
Size: 3953 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/dm-devel/attachments/20070730/0e7e8808/attachment.bin>