linux-kernel - Re: [PATCH] Correctly release and allocate a new request on TUR retries

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Message-ID: <20081205180851.GA9671@linux.vnet.ibm.com>
Date:	Fri, 5 Dec 2008 10:08:51 -0800
From:	Mike Anderson <andmike@...ux.vnet.ibm.com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	"Alan D. Brunelle" <Alan.Brunelle@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	LKML-scsi <linux-scsi@...r.kernel.org>,
	James.Bottomley@...senPartnership.com
Subject: Re: [PATCH] Correctly release and allocate a new request on TUR
	retries

Jens Axboe <jens.axboe@...cle.com> wrote:
> On Fri, Dec 05 2008, Alan D. Brunelle wrote:
> > 
> 
> > 
> > Commands needing to be retried (TUR in this case) would result in a block
> > I/O request being re-used, without being re-initialized properly. This
> > patch ensures that the requests are correctly re-initialized via
> > standard allocation means.
> > 
> > Prior to this patch, boots were failing consistently as in:
> > http://lkml.org/lkml/2008/12/5/161
> > 
> > With this patch in place, the system is booting reliably.
> > 
> > Signed-off-by: Alan D. Brunelle <alan.brunelle@...com>
> > Cc: Jens Axboe <jens.axboe@...cle.com>
> 
> Looks good.
> 
> Acked-by: Jens Axboe <jens.axboe@...cle.com>
> 
> Perhaps James can push it in, I'm about to shutdown for the day...
> 

I know a failure was not detected in the hp_sw_start_stop function, but it
uses the same retry method as hp_sw_tur we should update this function
also.

I made a quick scope of callers of blk_get_request and I did not see a
repeated of this retry usage model. I will make another pass to see if I
missed something.

> 
> > ---
> >  drivers/scsi/device_handler/scsi_dh_hp_sw.c |    6 ++++--
> >  1 files changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/scsi/device_handler/scsi_dh_hp_sw.c b/drivers/scsi/device_handler/scsi_dh_hp_sw.c
> > index 9aec4ca..1f6b6a8 100644
> > --- a/drivers/scsi/device_handler/scsi_dh_hp_sw.c
> > +++ b/drivers/scsi/device_handler/scsi_dh_hp_sw.c
> > @@ -107,6 +107,7 @@ static int hp_sw_tur(struct scsi_device *sdev, struct hp_sw_dh_data *h)
> >  	struct request *req;
> >  	int ret;
> >  
> > +retry:
> >  	req = blk_get_request(sdev->request_queue, WRITE, GFP_NOIO);
> >  	if (!req)
> >  		return SCSI_DH_RES_TEMP_UNAVAIL;
> > @@ -121,7 +122,6 @@ static int hp_sw_tur(struct scsi_device *sdev, struct hp_sw_dh_data *h)
> >  	memset(req->sense, 0, SCSI_SENSE_BUFFERSIZE);
> >  	req->sense_len = 0;
> >  
> > -retry:
> >  	ret = blk_execute_rq(req->q, NULL, req, 1);
> >  	if (ret == -EIO) {
> >  		if (req->sense_len > 0) {
> > @@ -136,8 +136,10 @@ retry:
> >  		h->path_state = HP_SW_PATH_ACTIVE;
> >  		ret = SCSI_DH_OK;
> >  	}
> > -	if (ret == SCSI_DH_IMM_RETRY)
> > +	if (ret == SCSI_DH_IMM_RETRY) {
> > +		blk_put_request(req);
> >  		goto retry;
> > +	}
> >  	if (ret == SCSI_DH_DEV_OFFLINED) {
> >  		h->path_state = HP_SW_PATH_PASSIVE;
> >  		ret = SCSI_DH_OK;
> > -- 
> > 1.5.6.3
> > 
> 
> 
> -- 
> Jens Axboe
> 
> --
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-andmike
--
Michael Anderson
andmike@...ux.vnet.ibm.com
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