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[dm-devel] RE: [PATCH] scsi_dh: Adding more debug options for scsi rdac handler



Hi Chandra,
   Thanks for your comments. I will start working on incorporating your comments however I may need some clarifications. Please see my response inline..
- Babu

> -----Original Message-----
> From: Chandra Seetharaman [mailto:sekharan us ibm com]
> Sent: Tuesday, August 18, 2009 9:10 PM
> To: Moger, Babu
> Cc: Linux SCSI Mailing list; device-mapper development; Chauhan, Vijay;
> Stankey, Robert; Dachepalli, Sudhir
> Subject: Re: [PATCH] scsi_dh: Adding more debug options for scsi rdac
> handler
> 
> Hi Babu,
> 
> Code looks good. But I have few comments...
> 
> Generic:
>  - Is that all the debug stuff you want to add ?
>  - I would split this into few patches (since they
>      are can be independent and not related to
>      configurable logging, IMO)
>    1. Add the array_name and index and acquiring it.
>    2. Moving the initialization code to attach()
>    3. removal of SCSI_DH_OK in check_ownership() (more below).
>    4. Logging stuff.
>    (1) and (4) have dependency, but (2) and (3) are
>    totally independent of all this.

I am fine with this proposal. I will try to see if I can do it without creating merging issues.
      I think I can break it into three patches. 
	a) removal of SCSI_DH_OK in check_ownership() (more below).
	b) moving the initialization code to attach()
      c) combining 1 and 4. 
	What do you think?

> 
> Specific comments inline...
> 
> On Mon, 2009-08-17 at 11:46 -0600, Moger, Babu wrote:
> > From: Babu Moger <babu moger lsi com>
> >
> > Hi All,
> > This patch adds more debugging options to scsi rdac device handler.
> This patch can considerably reduce the time taken to debug issues in
> big configurations also very helpful in addressing the support issues.
> > Here are the summary of changes.
> >  - Added a bit mask "module parameter" rdac_logging with 2 bits for
> each type of logging.
> 
> Why 2 bits ? isn't 1 bit sufficient ?

Right now 1 bit is sufficient. We thought it may be necessary in future in case we want to display only some messages(critical or info but not all) in particular category.  

> 
> >  - currently defined only two types of logging(failover and sense
> logging). Can be enhanced later if required.
> >  - Only failover logging is enabled for now which is equivalent of
> current logging.
> by default.

Ok. I will correct it.

> 
> >
> > Signed-off-by: Babu Moger <babu moger lsi com>
> > Reviewed-by: Vijay Chauhan <vijay chauhan lsi com>
> > Reviewed-by: Bob Stankey <Robert stankey lsi com>
> >
> > ---
> > --- linux-2.6.31-rc5/drivers/scsi/device_handler/scsi_dh_rdac.c.orig
> 	2009-08-05 16:30:51.000000000 -0500
> > +++ linux-2.6.31-rc5/drivers/scsi/device_handler/scsi_dh_rdac.c	2009-
> 08-17 09:15:03.000000000 -0500
> > @@ -135,6 +135,8 @@ struct rdac_controller {
> >  		struct rdac_pg_legacy legacy;
> >  		struct rdac_pg_expanded expanded;
> >  	} mode_select;
> > +	u8			index;
> > +	u8			array_name[31];
> 
> Can use a #define ?

If I understood your question correctly,  #define may not work well. Reason is, if we have multiple arrays(which is very common) then we cannot differentiate the two arrays.. So we have to have index and array name separately for each array/controller..

> 
> >  };
> >  struct c8_inquiry {
> >  	u8	peripheral_info;
> > @@ -198,6 +200,31 @@ static const char *lun_state[] =
> >  static LIST_HEAD(ctlr_list);
> >  static DEFINE_SPINLOCK(list_lock);
> >
> > +/*
> > + * module parameter to enable rdac debug logging.
> > + * 2 bits for each type of logging, only two types defined for now
> > + * Can be enhanced if required at later point
> > + */
> > +static int rdac_logging = 1;
> > +module_param(rdac_logging, int, S_IRUGO|S_IWUSR);
> > +MODULE_PARM_DESC(rdac_logging, "A bit mask of rdac logging levels, "
> > +		"Default is 1 - failover logging enabled, "
> > +		"set it to 0xF to enable all the logs");
> > +
> > +#define RDAC_LOG_FAILOVER	0
> > +#define RDAC_LOG_SENSE		2
> > +
> > +#define RDAC_LOG_BITS		2
> > +
> > +#define RDAC_LOG_LEVEL(SHIFT)  \
> > +        ((rdac_logging >> (SHIFT)) & ((1 << (RDAC_LOG_BITS)) - 1))
> > +
> > +#define RDAC_DEBUG(SHIFT, sdev, f, arg...) \
> 
> instead of RDAC_DEBUG, we can say RDAC_LOG ?!

Sure.. I will do that..

> 
> > +do { \
> > +	if (unlikely(RDAC_LOG_LEVEL(SHIFT))) \
> > +		sdev_printk(KERN_INFO, sdev, RDAC_NAME ": " f "\n", ##
> arg); \
> > +} while (0);
> > +
> >  static inline struct rdac_dh_data *get_rdac_data(struct scsi_device
> *sdev)
> >  {
> >  	struct scsi_dh_data *scsi_dh_data = sdev->scsi_dh_data;
> > @@ -324,6 +351,13 @@ static struct rdac_controller *get_contr
> >  	/* initialize fields of controller */
> >  	memcpy(ctlr->subsys_id, subsys_id, SUBSYS_ID_LEN);
> >  	memcpy(ctlr->slot_id, slot_id, SLOT_ID_LEN);
> > +
> > +	/* update the controller index */
> > +	if (slot_id[1] == 0x31)
> > +		ctlr->index = 0;
> > +	else
> > +		ctlr->index = 1;
> > +
> >  	kref_init(&ctlr->kref);
> >  	ctlr->use_ms10 = -1;
> >  	list_add(&ctlr->node, &ctlr_list);
> > @@ -381,6 +415,26 @@ static int get_lun(struct scsi_device *s
> >  	return err;
> >  }
> >
> > +static int get_array_name(struct scsi_device *sdev, struct
> rdac_dh_data *h)
> > +{
> > +	int err, i;
> > +	struct c8_inquiry *inqp;
> > +
> > +	err = submit_inquiry(sdev, 0xC8, sizeof(struct c8_inquiry), h);
> > +	if (err == SCSI_DH_OK) {
> > +		inqp = &h->inq.c8;
> > +		if (inqp->page_code != 0xc8)
> > +			return SCSI_DH_NOSYS;
> > +
> > +		for(i=0; i<30; ++i) {
> > +			h->ctlr->array_name[i] = inqp-
> >array_user_label[(2*i)+1];
> > +		}
> 
> do not have to have { } for a single line loop.

Sure.. I will remove that..

> 
> > +		h->ctlr->array_name[30] = '\0';
> > +	}
> > +
> > +	return err;
> > +}
> > +
> >  static int check_ownership(struct scsi_device *sdev, struct
> rdac_dh_data *h)
> >  {
> >  	int err;
> > @@ -450,13 +504,12 @@ static int mode_select_handle_sense(stru
> >  {
> >  	struct scsi_sense_hdr sense_hdr;
> >  	int err = SCSI_DH_IO, ret;
> > +	struct rdac_dh_data *h = get_rdac_data(sdev);
> >
> >  	ret = scsi_normalize_sense(sensebuf, SCSI_SENSE_BUFFERSIZE,
> &sense_hdr);
> >  	if (!ret)
> >  		goto done;
> >
> > -	err = SCSI_DH_OK;
> > -
> 
> This is a change in behavior.
> 
> Why is this needed ?

Setting the flag by default to SCSI_DH_OK might wrongly report the command as success even though the command had failed. The switch statement here only lists certain check conditions. If the target returns the check conditions other than the listed here then this function will return SCSI_DH_OK which is not correct.

> 
> >  	switch (sense_hdr.sense_key) {
> >  	case NO_SENSE:
> >  	case ABORTED_COMMAND:
> > @@ -478,12 +531,15 @@ static int mode_select_handle_sense(stru
> >  			err = SCSI_DH_RETRY;
> >  		break;
> >  	default:
> > -		sdev_printk(KERN_INFO, sdev,
> > -			    "MODE_SELECT failed with sense
> %02x/%02x/%02x.\n",
> > -			    sense_hdr.sense_key, sense_hdr.asc,
> sense_hdr.ascq);
> > +		break;
> >  	}
> >
> >  done:
> > +	RDAC_DEBUG(RDAC_LOG_FAILOVER, sdev, "array %s, ctlr %d, "
> > +		"MODE_SELECT returned with sense %02x/%02x/%02x",
> > +		(char *) h->ctlr->array_name, h->ctlr->index,
> > +		sense_hdr.sense_key, sense_hdr.asc, sense_hdr.ascq);
> > +
> 
> May need to be moved above "done:", as the control comes to done when
> scsi_normalize_sense() fails.

Sometimes we have seen target returning invalid sense. We need to catch that as well. That is the reason we moved this after done.

> 
> >
> >  	return err;
> >  }
> >
> > @@ -499,7 +555,9 @@ retry:
> >  	if (!rq)
> >  		goto done;
> >
> > -	sdev_printk(KERN_INFO, sdev, "%s MODE_SELECT command.\n",
> > +	RDAC_DEBUG(RDAC_LOG_FAILOVER, sdev, "array %s, ctlr %d, "
> > +		"%s MODE_SELECT command",
> > +		(char *) h->ctlr->array_name, h->ctlr->index,
> >  		(retry_cnt == RDAC_RETRY_COUNT) ? "queueing" : "retrying");
> >
> >  	err = blk_execute_rq(q, NULL, rq, 1);
> > @@ -509,8 +567,12 @@ retry:
> >  		if (err == SCSI_DH_RETRY && retry_cnt--)
> >  			goto retry;
> >  	}
> > -	if (err == SCSI_DH_OK)
> > +	if (err == SCSI_DH_OK) {
> >  		h->state = RDAC_STATE_ACTIVE;
> > +		RDAC_DEBUG(RDAC_LOG_FAILOVER, sdev, "array %s, ctlr %d, "
> > +				"MODE_SELECT completed",
> > +				(char *) h->ctlr->array_name, h->ctlr->index);
> > +	}
> Don;t you think we need to have failure also reported ?

Failure will be anyway reported by the function mode_select_handle_sense. Did not want to print that again.

> 
> >
> >  done:
> >  	return err;
> > @@ -525,12 +587,6 @@ static int rdac_activate(struct scsi_dev
> >  	if (err != SCSI_DH_OK)
> >  		goto done;
> >
> > -	if (!h->ctlr) {
> > -		err = initialize_controller(sdev, h);
> > -		if (err != SCSI_DH_OK)
> > -			goto done;
> > -	}
> > -
> 
> You can also move the set_mode_select block below.

Sure.. I will do that..

> 
> >  	if (h->ctlr->use_ms10 == -1) {
> >  		err = set_mode_select(sdev, h);
> >  		if (err != SCSI_DH_OK)
> > @@ -559,6 +615,12 @@ static int rdac_check_sense(struct scsi_
> >  				struct scsi_sense_hdr *sense_hdr)
> >  {
> >  	struct rdac_dh_data *h = get_rdac_data(sdev);
> > +
> > +	RDAC_DEBUG(RDAC_LOG_SENSE, sdev, "array %s, ctlr %d, "
> > +			"command returned with sense %02x/%02x/%02x",
> > +			(char *) h->ctlr->array_name, h->ctlr->index,
> > +			sense_hdr->sense_key, sense_hdr->asc, sense_hdr-
> >ascq);
> > +
> 
> It is not a "command", right ? Code comes here for any I/O failure.
> cut-n-paste problem :)

I was in a confusion about what will be the right word here. Ok.. I will use "I/O"

> 
> 
> >  	switch (sense_hdr->sense_key) {
> >  	case NOT_READY:
> >  		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x01)
> > @@ -678,6 +740,16 @@ static int rdac_bus_attach(struct scsi_d
> >  	if (err != SCSI_DH_OK)
> >  		goto failed;
> >
> > +	if (!h->ctlr) {
> 
> I do not think we need this check here.

You are right.. We don’t need this check here..

> > +		err = initialize_controller(sdev, h);
> > +		if (err != SCSI_DH_OK)
> > +			goto failed;
> > +
> > +		err = get_array_name(sdev, h);
> > +		if (err != SCSI_DH_OK)
> > +			goto failed;
> > +	}
> > +
> >  	if (!try_module_get(THIS_MODULE))
> >  		goto failed;
> >
> >
> >
> >
> > --
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> in
> > the body of a message to majordomo vger kernel org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html



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