Linux block layer

* Re: [PATCHv6 15/37] thp: do not threat slab pages as huge in hpage_{nr_pages,size,mask}
From: Matthew Wilcox @ 2017-02-10 22:13 UTC (permalink / raw)
  To: Kirill A. Shutemov
  Cc: Theodore Ts'o, Andreas Dilger, Jan Kara, Andrew Morton,
	Alexander Viro, Hugh Dickins, Andrea Arcangeli, Dave Hansen,
	Vlastimil Babka, Ross Zwisler, linux-ext4, linux-fsdevel,
	linux-kernel, linux-mm, linux-block
In-Reply-To: <20170126115819.58875-16-kirill.shutemov@linux.intel.com>

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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