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SubjectRe: [PATCH] libnvdimm: Clarify nd_pfn_init() flow
On Mon, Jan 21, 2019 at 4:26 PM Wei Yang <richardw.yang@linux.intel.com> wrote:
[..]
> >@@ -706,6 +711,22 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
> > sig = DAX_SIG;
> > else
> > sig = PFN_SIG;
> >+
> >+ /*
> >+ * Check for an existing 'pfn' superblock before writing a new
> >+ * one. The intended flow is that on the first probe of an
> >+ * nd_{pfn,dax} device the superblock is calculated and written
> >+ * to the namespace. In this case nd_pfn_validate() returns
> >+ * -ENODEV because no valid superblock exists currently.
>
> As you replied in following mail:
>
> 3/ If present, nd_pfn_validate() returns 0 and nd_dax_probe()
> registers the dax0.1 device (this is a libnvdimm 'personality device).
>
> So at this point, nd_pfn_validate() return 0 or -ENODEV?

In this case 0, because the configuration was successfully validated.

-ENODEV, is only returned for the initial case where we want the
kernel to write the configuration.

All other error codes are an actual failure and the probe procedure stops.

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