Re: [patch 4/4] mm: return boolean from page_has_private()

[Christoph Lameter <cl@linux-foundation.org>]

On Tue, 21 Jul 2009, Johannes Weiner wrote:

> Make page_has_private() return a true boolean value and remove the
> double negations from the two callsites using it for arithmetic.

page_has_private_data()?

Also note that you are adding unecessary double negation to the other
callers. Does the compiler catch that?

> +static inline int page_has_private(struct page *page)
> +{
> +	return !!(page->flags & ((1 << PG_private) | (1 << PG_private_2)));
> +}

Two private bits? How did that happen?

Could we define a PAGE_FLAGS_PRIVATE in page-flags.h?

> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 6b368d3..67e2824 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -286,7 +286,7 @@ static inline int page_mapping_inuse(struct page *page)
>
>  static inline int is_page_cache_freeable(struct page *page)
>  {
> -	return page_count(page) - !!page_has_private(page) == 2;
> +	return page_count(page) - page_has_private(page) == 2;

That looks funky and in need of comments.

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