Re: [PATCH] mm/memory-failure: call shake_page() when error hits thp tail page

[Andi Kleen]

On Wed, Apr 15, 2015 at 07:25:46AM +0000, Naoya Horiguchi wrote:
> Currently memory_failure() calls shake_page() to sweep pages out from pcplists
> only when the victim page is 4kB LRU page or thp head page. But we should do
> this for a thp tail page too.
> Consider that a memory error hits a thp tail page whose head page is on a
> pcplist when memory_failure() runs. Then, the current kernel skips shake_pages()
> part, so hwpoison_user_mappings() returns without calling split_huge_page() nor
> try_to_unmap() because PageLRU of the thp head is still cleared due to the skip
> of shake_page().
> As a result, me_huge_page() runs for the thp, which is a broken behavior.
> 
> This patch fixes this problem by calling shake_page() for thp tail case.
> 
> Fixes: 385de35722c9 ("thp: allow a hwpoisoned head page to be put back to LRU")
> Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx  # v3.4+

Looks good to me.

Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>

-Andi

> ---
>  mm/memory-failure.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git v4.0.orig/mm/memory-failure.c v4.0/mm/memory-failure.c
> index d487f8dc6d39..2cc1d578144b 100644
> --- v4.0.orig/mm/memory-failure.c
> +++ v4.0/mm/memory-failure.c
> @@ -1141,10 +1141,10 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
>  	 * The check (unnecessarily) ignores LRU pages being isolated and
>  	 * walked by the page reclaim code, however that's not a big loss.
>  	 */
> -	if (!PageHuge(p) && !PageTransTail(p)) {
> -		if (!PageLRU(p))
> -			shake_page(p, 0);
> -		if (!PageLRU(p)) {
> +	if (!PageHuge(p)) {
> +		if (!PageLRU(hpage))
> +			shake_page(hpage, 0);
> +		if (!PageLRU(hpage)) {
>  			/*
>  			 * shake_page could have turned it free.
>  			 */
> -- 
> 2.1.0
> 

-- 
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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