RE: [PATCH 1/1] [SCSI] Fix a bug in deriving the FLUSH_TIMEOUT from the basic I/O timeout

KY Srinivasan
2014-06-04T17:15:21Z

> -----Original Message-----
> From: James Bottomley [mailto:jbottomley@parallels.com]
> Sent: Wednesday, June 4, 2014 10:02 AM
> To: KY Srinivasan
> Cc: linux-kernel@vger.kernel.org; apw@canonical.com;
> devel@linuxdriverproject.org; hch@infradead.org; linux-
> scsi@vger.kernel.org; ohering@suse.com; gregkh@linuxfoundation.org;
> jasowang@redhat.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@microsoft.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