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SubjectRe: [PATCH v3 1/3] mm: don't call __page_cache_release for hugetlb
On Tue 31-03-15 08:50:45, Naoya Horiguchi wrote:
> __put_compound_page() calls __page_cache_release() to do some freeing works,
> but it's obviously for thps, not for hugetlb. We didn't care it because PageLRU
> is always cleared and page->mem_cgroup is always NULL for hugetlb.
> But it's not correct and has potential risks, so let's make it conditional.
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

Reviewed-by: Michal Hocko <mhocko@suse.cz>

> ---
> mm/swap.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git v4.0-rc6.orig/mm/swap.c v4.0-rc6/mm/swap.c
> index cd3a5e64cea9..8e46823c3319 100644
> --- v4.0-rc6.orig/mm/swap.c
> +++ v4.0-rc6/mm/swap.c
> @@ -31,6 +31,7 @@
> #include <linux/memcontrol.h>
> #include <linux/gfp.h>
> #include <linux/uio.h>
> +#include <linux/hugetlb.h>
>
> #include "internal.h"
>
> @@ -75,7 +76,14 @@ static void __put_compound_page(struct page *page)
> {
> compound_page_dtor *dtor;
>
> - __page_cache_release(page);
> + /*
> + * __page_cache_release() is supposed to be called for thp, not for
> + * hugetlb. This is because hugetlb page does never have PageLRU set
> + * (it's never listed to any LRU lists) and no memcg routines should
> + * be called for hugetlb (it has a separate hugetlb_cgroup.)
> + */
> + if (!PageHuge(page))
> + __page_cache_release(page);
> dtor = get_compound_page_dtor(page);
> (*dtor)(page);
> }
> --
> 1.9.3

--
Michal Hocko
SUSE Labs


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