On Wed, Jun 11, 2014 at 12:04:51AM +0200, Andrea Arcangeli wrote:
> On Tue, Jun 10, 2014 at 11:46:40PM +0300, Kirill A. Shutemov wrote:
> > Agreed. The patchset drops tail page refcounting.
>
> Very possibly I misread something or a later patch fixes this up, I
> just did a basic code review, but from the new code of split_huge_page
> it looks like it returns -EBUSY after checking the individual tail
> page refcounts, so it's not clear how that defines as "dropped".
page_mapcount() here is really mapcount: how many times the page is
mapped, not pins on tail pages as we have it now.
>
> + for (i = 0; i < HPAGE_PMD_NR; i++)
> + tail_count += page_mapcount(page + i);
> + if (tail_count != page_count(page) - 1) {
> + BUG_ON(tail_count > page_count(page) - 1);
> + compound_unlock(page);
> + spin_unlock_irq(&zone->lru_lock);
> + return -EBUSY;
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--
Kirill A. Shutemov
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