On Tue, 2018-09-18 at 13:53 -0700, Dan Williams wrote:
> On Tue, Sep 18, 2018 at 1:08 PM Vishal Verma <[email protected]> wrote:
> >
> > If there are badblocks present in the 'struct page' area for pfn
> > namespaces, until now, the only way to clear them has been to force the
> > namespace into raw mode, clear the errors, and re-enable the fsdax mode.
> > This is clunky, given that it should be easy enough for the pfn driver
> > to do the same.
> >
> > Add a new helper that uses the most recently available badblocks list to
> > check whether there are any badblocks that lie in the volatile struct
> > page area. If so, before initializing the struct pages, send down
> > targeted writes via nvdimm_write_bytes to write zeroes to the affected
> > blocks, and thus clear errors.
> >
> > Cc: Dan Williams <[email protected]>
> > Signed-off-by: Vishal Verma <[email protected]>
> > ---
> > drivers/nvdimm/pfn_devs.c | 57
> > +++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 57 insertions(+)
> >
> > diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
> > index 3f7ad5bc443e..04b341758cd6 100644
> > --- a/drivers/nvdimm/pfn_devs.c
> > +++ b/drivers/nvdimm/pfn_devs.c
> > @@ -361,8 +361,59 @@ struct device *nd_pfn_create(struct nd_region
> > *nd_region)
> > return dev;
> > }
> >
>
> Perhaps a comment here about the fact that we are clearing the
> volatile memmap metadata space associated with a pfn instance.
>
> > +static int nd_pfn_clear_meta_errors(struct nd_pfn *nd_pfn)
>
> Let's just say "memmap" rather than "meta" to be more explicit.
>
> > +{
> > + struct nd_region *nd_region = to_nd_region(nd_pfn->dev.parent);
> > + struct nd_namespace_common *ndns = nd_pfn->ndns;
> > + void *zero_page = page_address(ZERO_PAGE(0));
> > + struct nd_pfn_sb *pfn_sb = nd_pfn->pfn_sb;
> > + sector_t first_bad, meta_start;
> > + struct nd_namespace_io *nsio;
> > + int num_bad, meta_num, rc;
> > + bool bb_present;
> > +
> > + nsio = to_nd_namespace_io(&ndns->dev);
> > + meta_start = (SZ_4K + sizeof(*pfn_sb)) >> 9;
> > + meta_num = (le64_to_cpu(pfn_sb->dataoff) >> 9) - meta_start;
> > +
> > + do {
> > + unsigned long zero_len;
> > + u64 nsoff;
> > +
> > + bb_present = !!badblocks_check(&nd_region->bb, meta_start,
> > + meta_num, &first_bad, &num_bad);
>
> The !! throws me off, I don't think it's necessary. You could just
> make bb_present an int.
I was following the precedent of is_bad_pmem(), but int works too.
>
> > + if (bb_present) {
> > + dev_dbg(&nd_pfn->dev, "meta: %x badblocks at %lx\n",
> > + num_bad, first_bad);
> > + nsoff = (nd_region->ndr_start + (first_bad << 9)) -
> > + nsio->res.start;
>
> Perhaps this should be ALIGN_DOWN((nd_region->ndr_start + (first_bad
> << 9)) - nsio->res.start, PAGE_SIZE)...
>
> > + zero_len = num_bad << 9;
>
> ...and then make this ALIGN(num_bad << 9, PAGE_SIZE), or otherwise a
> comment about zero_len being zero...
>
> > + while (zero_len) {
> > + unsigned long chunk = min(zero_len,
> > PAGE_SIZE);
>
> ...because the min(x, PAGE_SIZE) seems arbitrary.
>
> Aligned clearing may be preferable considering we may be needing to
> fixup page protections.
The min() is because our source of zeroes is PAGE_SIZE. zero_len
*should* never be zero as a badblocks entry with a 'count' of zero
would be a bug.. But aligned clearing makes sense too - we just
potentially end up writing more than we absolutely need to.
What do you mean by fixup page protections?
I agree with the rest of the comment, and will fix those up.
>
> > +
> > + rc = nvdimm_write_bytes(ndns, nsoff,
> > zero_page,
> > + chunk, 0);
> > + if (rc)
> > + break;
> > +
> > + zero_len -= chunk;
> > + nsoff += chunk;
> > + }
> > + if (rc) {
> > + dev_err(&nd_pfn->dev,
> > + "error clearing %x badblocks at
> > %lx\n",
> > + num_bad, first_bad);
> > + return rc;
> > + }
> > + }
> > + } while (bb_present);
> > +
> > + return 0;
> > +}
> > +
> > int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
> > {
> > + int rc;
> > u64 checksum, offset;
> > enum nd_pfn_mode mode;
> > struct nd_namespace_io *nsio;
> > @@ -477,6 +528,12 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char
> > *sig)
> > return -ENXIO;
> > }
> >
> > + if (mode == PFN_MODE_PMEM) {
> > + rc = nd_pfn_clear_meta_errors(nd_pfn);
> > + if (rc)
> > + return rc;
>
> I think this can just be "return nd_pfn_clear_meta_errors()", and
> maybe move the mode check inside nd_pfn_clear_meta_errors() to return
> early if no volatile metadata to clear.
>
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