On Tue, May 10, 2022 at 03:28:05AM +0100, Matthew Wilcox wrote:
> On Wed, Apr 27, 2022 at 02:32:20PM +0900, Naoya Horiguchi wrote:
> > From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> >
> > The following VM_BUG_ON_FOLIO() is triggered when memory error event
> > happens on the (thp/folio) pages which are about to be freed:
>
> So the real problem is that we're calling dump_page() when we don't
> have a reference to the page, right? Otherwise it wouldn't be freed.
Right, that's the problem.
>
> > out:
> > if (ret == -EIO)
> > - dump_page(p, "hwpoison: unhandlable page");
> > + pr_err("Memory failure: %#lx: unhandlable page.\n", page_to_pfn(p));
>
> It would be nice to get some more information out of the page than that
> ,.. but taking a refcount inside dump_page() conflicts with the other
> "would be nice", which is for dump_page() to take a const struct page *
> so we can (eg) make folio_test_uptodate() take a const struct folio *.
>
> We've had some other problems with inconsistent pages being printed in
> dump_page(). It can be quite confusing when debugging. I still don't
> have a good solution to that either.
>
> I do have a proposal for reforming mapcount which will solve this
> particular problem, but I'm not quite sure when I'll get to it.
> This patch is probably the best thing to do for now.
Thank you for the comment. So I leave this code simple (or some
hwpoison specific dump_page() if someone have good ideas) until some
ultimate solution is ready for upstream.
Thanks,
Naoya Horiguchi
