On Thu, Jan 31, 2013 at 11:34:16AM -0800, Andrew Morton wrote:
> On Thu, 31 Jan 2013 10:25:58 -0500
> Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> wrote:
>
> > num_poisoned_pages counts up the number of pages isolated by memory errors.
> > But for thp, only one subpage is isolated because memory error handler
> > splits it, so it's wrong to add (1 << compound_trans_order).
> >
> > ...
> >
> > --- mmotm-2013-01-23-17-04.orig/mm/memory-failure.c
> > +++ mmotm-2013-01-23-17-04/mm/memory-failure.c
> > @@ -1039,7 +1039,14 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
> > return 0;
> > }
> >
> > - nr_pages = 1 << compound_trans_order(hpage);
> > + /*
> > + * If a thp is hit by a memory failure, it's supposed to be split.
> > + * So we should add only one to num_poisoned_pages for that case.
> > + */
> > + if (PageHuge(p))
>
> /*
> * PageHuge() only returns true for hugetlbfs pages, but not for normal or
> * transparent huge pages. See the PageTransHuge() documentation for more
> * details.
> */
> int PageHuge(struct page *page)
> {
Do you mean that my comment refers to thp but this if-condition uses
PageHuge so it's confusing, right?
And yes, that's right, so I want to change this comment like this:
/*
* Currently errors on hugetlbfs pages are contained in hugepage
* unit, so nr_pages should be 1 << compound_order. OTOH when
* errors are on transparent hugepages, they are supposed to be
* split and error containment is done in normal page unit.
* So nr_pages should be one in this case.
*/
>
> > + nr_pages = 1 << compound_trans_order(hpage);
I should've used compound_order because this code is run only for
hugetlbfs pages.
> > + else /* normal page or thp */
> > + nr_pages = 1;
> > atomic_long_add(nr_pages, &num_poisoned_pages);
> >
> > /*
Thanks,
Naoya
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