Re: oomkiller over-ambitious after "vmscan: make mapped executablepages the first class citizen" (bisected)

[Rik van Riel]

Wu Fengguang wrote:

> vmscan: limit VM_EXEC protection to file pages
>
> It is possible to have !Anon but SwapBacked pages, and some apps could
> create huge number of such pages with MAP_SHARED|MAP_ANONYMOUS. These
> pages go into the ANON lru list, and hence shall not be protected: we
> only care mapped executable files. Failing to do so may trigger OOM.

Good catch!  The MAP_SHARED|MAP_ANONYMOUS segments may
be backed by anonymous tmpfs files, instead of by
actual anonymous memory!

If this patch solves Christian's problem, I believe
it should get merged into Linus's tree ASAP.

> Reported-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

>  mm/vmscan.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- linux.orig/mm/vmscan.c	2009-10-13 09:49:05.000000000 +0800
> +++ linux/mm/vmscan.c	2009-10-13 09:49:37.000000000 +0800
> @@ -1356,7 +1356,7 @@ static void shrink_active_list(unsigned 
>  			 * IO, plus JVM can create lots of anon VM_EXEC pages,
>  			 * so we ignore them here.
>  			 */
> -			if ((vm_flags & VM_EXEC) && !PageAnon(page)) {
> +			if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
>  				list_add(&page->lru, &l_active);
>  				continue;
>  			}


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