Re: [PATCHv6 15/37] thp: do not threat slab pages as huge in hpage_{nr_pages,size,mask}

Matthew Wilcox
2017-02-10T22:13:57Z

On Thu, Jan 26, 2017 at 02:57:57PM +0300, Kirill A. Shutemov wrote:
> Slab pages can be compound, but we shouldn't threat them as THP for
> pupose of hpage_* helpers, otherwise it would lead to confusing results.
>
> For instance, ext4 uses slab pages for journal pages and we shouldn't
> confuse them with THPs. The easiest way is to exclude them in hpage_*
> helpers.

Well ... I think we should just deal with compound pages instead of just
huge or regular. So I'm deferring comment on this patch.

> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
> include/linux/huge_mm.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index e5c9c26d2439..5e6c408f5b47 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -137,21 +137,21 @@ static inline spinlock_t *pmd_trans_huge_lock(pmd_t *pmd,
> }
> static inline int hpage_nr_pages(struct page *page)
> {
> - if (unlikely(PageTransHuge(page)))
> + if (unlikely(!PageSlab(page) && PageTransHuge(page)))
> return HPAGE_PMD_NR;
> return 1;
> }
>
> static inline int hpage_size(struct page *page)
> {
> - if (unlikely(PageTransHuge(page)))
> + if (unlikely(!PageSlab(page) && PageTransHuge(page)))
> return HPAGE_PMD_SIZE;
> return PAGE_SIZE;
> }
>
> static inline unsigned long hpage_mask(struct page *page)
> {
> - if (unlikely(PageTransHuge(page)))
> + if (unlikely(!PageSlab(page) && PageTransHuge(page)))
> return HPAGE_PMD_MASK;
> return PAGE_MASK;
> }
> --
> 2.11.0
>
> --
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