linux-kernel - RE: [PATCH 1/1] [SCSI] Fix a bug in deriving the FLUSH

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Date:	Wed, 4 Jun 2014 17:15:15 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	James Bottomley <jbottomley@...allels.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"apw@...onical.com" <apw@...onical.com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"hch@...radead.org" <hch@...radead.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"ohering@...e.com" <ohering@...e.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"jasowang@...hat.com" <jasowang@...hat.com>
Subject: RE: [PATCH 1/1] [SCSI] Fix a bug in deriving the FLUSH_TIMEOUT from
 the basic I/O timeout



> -----Original Message-----
> From: James Bottomley [mailto:jbottomley@...allels.com]
> Sent: Wednesday, June 4, 2014 10:02 AM
> To: KY Srinivasan
> Cc: linux-kernel@...r.kernel.org; apw@...onical.com;
> devel@...uxdriverproject.org; hch@...radead.org; linux-
> scsi@...r.kernel.org; ohering@...e.com; gregkh@...uxfoundation.org;
> jasowang@...hat.com
> Subject: Re: [PATCH 1/1] [SCSI] Fix a bug in deriving the FLUSH_TIMEOUT
> from the basic I/O timeout
> 
> On Wed, 2014-06-04 at 09:33 -0700, K. Y. Srinivasan wrote:
> > Commit ID: 7e660100d85af860e7ad763202fff717adcdaacd added code to
> > derive the FLUSH_TIMEOUT from the basic I/O timeout. However, this
> > patch did not use the basic I/O timeout of the device. Fix this bug.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> > ---
> >  drivers/scsi/sd.c |    4 +++-
> >  1 files changed, 3 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index
> > e9689d5..54150b1 100644
> > --- a/drivers/scsi/sd.c
> > +++ b/drivers/scsi/sd.c
> > @@ -832,7 +832,9 @@ static int sd_setup_write_same_cmnd(struct
> > scsi_device *sdp, struct request *rq)
> >
> >  static int scsi_setup_flush_cmnd(struct scsi_device *sdp, struct
> > request *rq)  {
> > -	rq->timeout *= SD_FLUSH_TIMEOUT_MULTIPLIER;
> > +	int timeout = sdp->request_queue->rq_timeout;
> > +
> > +	rq->timeout = (timeout * SD_FLUSH_TIMEOUT_MULTIPLIER);
> 
> Could you share where you found this to be a problem?  It looks like a bug in
> block because all inbound requests being prepared should have a timeout
> set, so block would be the place to fix it.

Perhaps; what I found was that the value in rq->timeout was 0 coming into
this function and thus multiplying obviously has no effect.

> 
> I can't see how this can happen because we definitely add the timer after the
> request is prepared in my reading of the block code, unless I'm missing some
> path in block that violates this.
> 
> James

K. Y

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