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From: Dan Williams <dan.j.williams@intel.com>
Date: Thu, 15 Aug 2019 12:54:51 -0700
Message-ID: <CAPcyv4hxo4HvtqZ-B6JG5iATo_vEAKPzO5EU5Lugs2_edEbW7Q@mail.gmail.com>
Subject: Re: [PATCH v5 1/4] nvdimm: Consider probe return -EOPNOTSUPP as
 success
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
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On Tue, Aug 13, 2019 at 9:22 PM Dan Williams <dan.j.williams@intel.com> wrote:
>
> Hi Aneesh, logic looks correct but there are some cleanups I'd like to
> see and a lead-in patch that I attached.
>
> I've started prefixing nvdimm patches with:
>
>     libnvdimm/$component:
>
> ...since this patch mostly impacts the pmem driver lets prefix it
> "libnvdimm/pmem: "
>
> On Fri, Aug 9, 2019 at 12:45 AM Aneesh Kumar K.V
> <aneesh.kumar@linux.ibm.com> wrote:
> >
> > This patch add -EOPNOTSUPP as return from probe callback to
>
> s/This patch add/Add/
>
> No need to say "this patch" it's obviously a patch.
>
> > indicate we were not able to initialize a namespace due to pfn superblock
> > feature/version mismatch. We want to consider this a probe success so that
> > we can create new namesapce seed and there by avoid marking the failed
> > namespace as the seed namespace.
>
> Please replace usage of "we" with the exact agent involved as which
> "we" is being referred to gets confusing for the reader.
>
> i.e. "indicate that the pmem driver was not..." "The nvdimm core wants
> to consider this...".
>
> >
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> > ---
> >  drivers/nvdimm/bus.c  |  2 +-
> >  drivers/nvdimm/pmem.c | 26 ++++++++++++++++++++++----
> >  2 files changed, 23 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
> > index 798c5c4aea9c..16c35e6446a7 100644
> > --- a/drivers/nvdimm/bus.c
> > +++ b/drivers/nvdimm/bus.c
> > @@ -95,7 +95,7 @@ static int nvdimm_bus_probe(struct device *dev)
> >         rc = nd_drv->probe(dev);
> >         debug_nvdimm_unlock(dev);
> >
> > -       if (rc == 0)
> > +       if (rc == 0 || rc == -EOPNOTSUPP)
> >                 nd_region_probe_success(nvdimm_bus, dev);
>
> This now makes the nd_region_probe_success() helper obviously misnamed
> since it now wants to take actions on non-probe success. I attached a
> lead-in cleanup that you can pull into your series that renames that
> routine to nd_region_advance_seeds().
>
> When you rebase this needs a comment about why EOPNOTSUPP has special handling.
>
> >         else
> >                 nd_region_disable(nvdimm_bus, dev);
> > diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> > index 4c121dd03dd9..3f498881dd28 100644
> > --- a/drivers/nvdimm/pmem.c
> > +++ b/drivers/nvdimm/pmem.c
> > @@ -490,6 +490,7 @@ static int pmem_attach_disk(struct device *dev,
> >
> >  static int nd_pmem_probe(struct device *dev)
> >  {
> > +       int ret;
> >         struct nd_namespace_common *ndns;
> >
> >         ndns = nvdimm_namespace_common_probe(dev);
> > @@ -505,12 +506,29 @@ static int nd_pmem_probe(struct device *dev)
> >         if (is_nd_pfn(dev))
> >                 return pmem_attach_disk(dev, ndns);
> >
> > -       /* if we find a valid info-block we'll come back as that personality */
> > -       if (nd_btt_probe(dev, ndns) == 0 || nd_pfn_probe(dev, ndns) == 0
> > -                       || nd_dax_probe(dev, ndns) == 0)
>
> Similar need for an updated comment here to explain the special
> translation of error codes.
>
> > +       ret = nd_btt_probe(dev, ndns);
> > +       if (ret == 0)
> >                 return -ENXIO;
> > +       else if (ret == -EOPNOTSUPP)
>
> Are there cases where the btt driver needs to return EOPNOTSUPP? I'd
> otherwise like to keep this special casing constrained to the pfn /
> dax info block cases.

In fact I think EOPNOTSUPP is only something that the device-dax case
would be concerned with because that's the only interface that
attempts to guarantee a given mapping granularity.