Re: unhandlable pages

[Yang Shi <shy828301@gmail.com>]

On Mon, Mar 21, 2022 at 10:28 AM Luck, Tony <tony.luck@intel.com> wrote:
>
> On Mon, Mar 21, 2022 at 05:21:05PM +0000, Matthew Wilcox wrote:
> > On Mon, Mar 21, 2022 at 10:17:29AM -0700, Luck, Tony wrote:
> > > Validation folks are seeing this on a v5.16 kernel. I don't
> > > see any changes in v5.17 that look like they address it.
> > >
> > > Mar 04 14:05:05 JF5300-07B181T kernel: page:00000000696b0b6a refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x195cda44
> > > Mar 04 14:05:05 JF5300-07B181T kernel: flags: 0x57ffffc0801000(reserved|hwpoison|node=1|zone=2|lastcpupid=0x1fffff)
> > > Mar 04 14:05:05 JF5300-07B181T kernel: raw: 0057ffffc0801000 ffff6ea817369108 ffff6ea817369108 0000000000000000
> > > Mar 04 14:05:05 JF5300-07B181T kernel: raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
> > > Mar 04 14:05:05 JF5300-07B181T kernel: page dumped because: hwpoison: unhandlable page
> > > Mar 04 14:05:05 JF5300-07B181T kernel: Memory failure: 0x195cda44: recovery action for unknown page: Ignored
> > >
> > > Som debugging shows this is an anon page (expected ... that's the
> > > type of page where the error was injected. They see shake_page()
> > > called three times, but it doesn't change anything, so the page
> > > is reported as unhandlable.
> >
> > Uhm, that's not PageAnon.  page->mapping is NULL, and anon pages have
> > the bottom bit set with the rest of the page->mapping pointing to its
> > anon_vma.  Why do you think it's an anon page?
>
> Sorry. I didn't do that decode ... just copied what was in the internal
> report.  If it isn't anon, then does that page dump give info on what
> type the page is?

As Willy said we can't tell what type the page is. Per the dumped
information, the page has:
  - 1 refcount, likely get from hwpoison
  - 0 mapcount, unmapped and not unmapped by hwpoison since
dump_page() is called before that,
  - NULL mapping
  - PG_reserved flag is set and no other flag is set

So I just can say it is very unlikely to be an anonymous page. It is
not slab either. And neither anonymous/page cache nor slab should be
reserved flag set, so it should be some other types.

>
> -Tony