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

[Mike Christie]

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.