Re: [PATCH] mm, hugetlb: correct missing private flag clearing

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 30 Sep 2013 16:59:44 +0900 Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:

> We should clear the page's private flag when returing the page to
> the page allocator or the hugepage pool. This patch fixes it.
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> ---
> Hello, Andrew.
> 
> I sent the new version of commit ('07443a8') before you did pull request,
> but it isn't included. It may be losted :)
> So I send this fix. IMO, this is good for v3.12.
> 
> Thanks.
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index b49579c..691f226 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -653,6 +653,7 @@ static void free_huge_page(struct page *page)
>  	BUG_ON(page_count(page));
>  	BUG_ON(page_mapcount(page));
>  	restore_reserve = PagePrivate(page);
> +	ClearPagePrivate(page);
>  

You describe it as a fix, but what does it fix?  IOW, what are the
user-visible effects of the change?

update_and_free_page() already clears PG_private, but afaict the bit
remains unaltered if free_huge_page() takes the enqueue_huge_page()
route.

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