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SubjectRe: [PATCHv2, RFC 07/30] thp, mm: introduce mapping_can_have_hugepages() predicate
Hi Kirill,
On 03/15/2013 01:50 AM, Kirill A. Shutemov wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>
> Returns true if mapping can have huge pages. Just check for __GFP_COMP
> in gfp mask of the mapping for now.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> ---
> include/linux/pagemap.h | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index e3dea75..3521b0d 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -84,6 +84,16 @@ static inline void mapping_set_gfp_mask(struct address_space *m, gfp_t mask)
> (__force unsigned long)mask;
> }
>
> +static inline bool mapping_can_have_hugepages(struct address_space *m)
> +{
> + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
> + gfp_t gfp_mask = mapping_gfp_mask(m);
> + return !!(gfp_mask & __GFP_COMP);

I always see !! in kernel, but why check directly instead of have !! prefix?

> + }
> +
> + return false;
> +}
> +
> /*
> * The page cache can done in larger chunks than
> * one page, because it allows for more efficient



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