linux-kernel - Re: [PATCH next] xen: pcifront: Process failure for pcifront_(re)scan

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Message-ID: <20141015210355.GB6579@laptop.dumpdata.com>
Date:	Wed, 15 Oct 2014 17:03:55 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Chen Gang <gang.chen.5i5j@...il.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, boris.ostrovsky@...cle.com,
	xen-devel@...ts.xenproject.org,
	" linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH next] xen: pcifront: Process failure for
 pcifront_(re)scan_root()

On Wed, Oct 15, 2014 at 08:20:06AM +0800, Chen Gang wrote:
> 
> At least for me, what you said sound OK.

Let me review it - next week.
> 
> Thanks.
> 
> 
> Send from Lenovo A788t.
> 
> Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> 
> >On Mon, Oct 06, 2014 at 11:04:45AM +0800, Chen Gang wrote:
> >> When pcifront_rescan_root() or pcifront_scan_root() fails, need return
> >> error code, neither set XenbusStateConnected state, just like the other
> >> areas have done.
> >>
> >> For pcifront_rescan_root(), it will return error code ("num_roots = 0;",
> >> skip xenbus_switch_state return value).
> >> 
> >> For pcifront_scan_root(), it will return 0 ("num_roots = 0;", set 0 by
> >> the return value of xenbus_switch_state, which always return 0, at
> >> present).
> >
> >The changelog is somewhat confusing because it talks about the patch hunks
> >in reverse order (the pcifront_scan_root() change is first in the patch,
> >but the changelog mentions pcifront_rescan_root() first).  I *think* this
> >means:
> >
> >  When pcifront_try_connect() finds no PCI roots, it falls back to calling
> >  pcifront_scan_root() for 0000:00.  If that fails, it used to switch to
> >  XenbusStateConnected and return success (because xenbus_switch_state()
> >  currently always succeeds).
> >
> >  If pcifront_scan_root() fails, leave the XenbusState unchanged and
> >  return an error code.
> >
> >  Similarly, pcifront_attach_devices() falls back to calling
> >  pcifront_rescan_root() for 0000:00.  If that fails, it used to 
> >  switch to XenbusStateConnected and return an error code.
> >
> >  If pcifront_rescan_root() fails, leave the XenbusState unchanged and
> >  return the error code.
> >
> >The "num_roots" part doesn't seem relevant to me.
> >
> >> Signed-off-by: Chen Gang <gang.chen.5i5j@...il.com>
> >
> >Konrad, if you want to take this, feel free.  Otherwise, if you ack it and
> >you think my changelog understanding makes sense, I can pick it up.
> >
> >It does seem odd that pcifront_attach_devices() ignores the
> >xenbus_switch_state() return value while pcifront_try_connect() does not.
> >But many other callers also ignore the return value, so maybe that's OK.
> >
> >Bjorn
> >
> >> ---
> >>  drivers/pci/xen-pcifront.c | 10 ++++++++++
> >>  1 file changed, 10 insertions(+)
> >> 
> >> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> >> index 53df39a..d78d884 100644
> >> --- a/drivers/pci/xen-pcifront.c
> >> +++ b/drivers/pci/xen-pcifront.c
> >> @@ -866,6 +866,11 @@ static int pcifront_try_connect(struct pcifront_device *pdev)
> >>  		xenbus_dev_error(pdev->xdev, err,
> >>  				 "No PCI Roots found, trying 0000:00");
> >>  		err = pcifront_scan_root(pdev, 0, 0);
> >> +		if (err) {
> >> +			xenbus_dev_fatal(pdev->xdev, err,
> >> +					 "Error scanning PCI root 0000:00");
> >> +			goto out;
> >> +		}
> >>  		num_roots = 0;
> >>  	} else if (err != 1) {
> >>  		if (err == 0)
> >> @@ -947,6 +952,11 @@ static int pcifront_attach_devices(struct pcifront_device *pdev)
> >>  		xenbus_dev_error(pdev->xdev, err,
> >>  				 "No PCI Roots found, trying 0000:00");
> >>  		err = pcifront_rescan_root(pdev, 0, 0);
> >> +		if (err) {
> >> +			xenbus_dev_fatal(pdev->xdev, err,
> >> +					 "Error scanning PCI root 0000:00");
> >> +			goto out;
> >> +		}
> >>  		num_roots = 0;
> >>  	} else if (err != 1) {
> >>  		if (err == 0)
> >> -- 
> >> 1.9.3
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