Re: [PATCH v2 6/9] mm, hwpoison: set PG_hwpoison for busy hugetlb pages

[Miaohe Lin]

On 2022/6/24 7:51, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> 
> If memory_failure() fails to grab page refcount on a hugetlb page
> because it's busy, it returns without setting PG_hwpoison on it.
> This not only loses a chance of error containment, but breaks the rule
> that action_result() should be called only when memory_failure() do
> any of handling work (even if that's just setting PG_hwpoison).
> This inconsistency could harm code maintainability.
> 
> So set PG_hwpoison and call hugetlb_set_page_hwpoison() for such a case.
> 
> Fixes: 405ce051236c ("mm/hwpoison: fix race between hugetlb free/demotion and memory_failure_hugetlb()")
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>

Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>

Thanks!

> ---
>  include/linux/mm.h  | 1 +
>  mm/memory-failure.c | 8 ++++----
>  2 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 4346e51484ba..044dc5a2e361 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3233,6 +3233,7 @@ enum mf_flags {
>  	MF_SOFT_OFFLINE = 1 << 3,
>  	MF_UNPOISON = 1 << 4,
>  	MF_SW_SIMULATED = 1 << 5,
> +	MF_NO_RETRY = 1 << 6,
>  };
>  extern int memory_failure(unsigned long pfn, int flags);
>  extern void memory_failure_queue(unsigned long pfn, int flags);
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 6005e953d011..ce045d0d6115 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1632,7 +1632,8 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
>  			count_increased = true;
>  	} else {
>  		ret = -EBUSY;
> -		goto out;
> +		if (!(flags & MF_NO_RETRY))
> +			goto out;
>  	}
>  
>  	if (hugetlb_set_page_hwpoison(head, page)) {
> @@ -1659,7 +1660,6 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
>  	struct page *p = pfn_to_page(pfn);
>  	struct page *head;
>  	unsigned long page_flags;
> -	bool retry = true;
>  
>  	*hugetlb = 1;
>  retry:
> @@ -1675,8 +1675,8 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
>  		}
>  		return res;
>  	} else if (res == -EBUSY) {
> -		if (retry) {
> -			retry = false;
> +		if (!(flags & MF_NO_RETRY)) {
> +			flags |= MF_NO_RETRY;
>  			goto retry;
>  		}
>  		action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED);
>