linux-kernel - Re: [PATCH v2 7/9] mm, hwpoison: make __page_handle

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Date:   Mon, 27 Jun 2022 17:02:47 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Naoya Horiguchi <nao.horiguchi@...il.com>, <linux-mm@...ck.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 7/9] mm, hwpoison: make __page_handle_poison returns
 int

On 2022/6/24 7:51, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@....com>
> 
> __page_handle_poison() returns bool that shows whether
> take_page_off_buddy() has passed or not now.  But we will want to
> distinguish another case of "dissolve has passed but taking off failed"
> by its return value. So change the type of the return value.
> No functional change.
> 
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
> ---
>  mm/memory-failure.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index ce045d0d6115..db85f644a1e3 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -71,7 +71,13 @@ atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
>  
>  static bool hw_memory_failure __read_mostly = false;
>  
> -static bool __page_handle_poison(struct page *page)
> +/*
> + * Return values:
> + *   1:   the page is dissolved (if needed) and taken off from buddy,
> + *   0:   the page is dissolved (if needed) and not taken off from buddy,
> + *   < 0: failed to dissolve.
> + */
> +static int __page_handle_poison(struct page *page)
>  {
>  	int ret;
>  
> @@ -81,7 +87,7 @@ static bool __page_handle_poison(struct page *page)
>  		ret = take_page_off_buddy(page);
>  	zone_pcp_enable(page_zone(page));
>  
> -	return ret > 0;
> +	return ret;
>  }
>  
>  static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
> @@ -91,7 +97,7 @@ static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, boo
>  		 * Doing this check for free pages is also fine since dissolve_free_huge_page
>  		 * returns 0 for non-hugetlb pages as well.
>  		 */
> -		if (!__page_handle_poison(page))
> +		if (__page_handle_poison(page) <= 0)
>  			/*
>  			 * We could fail to take off the target page from buddy
>  			 * for example due to racy page allocation, but that's
> @@ -1048,7 +1054,7 @@ static int me_huge_page(struct page_state *ps, struct page *p)
>  		 * subpages.
>  		 */
>  		put_page(hpage);
> -		if (__page_handle_poison(p)) {
> +		if (__page_handle_poison(p) > 0) {
>  			page_ref_inc(p);
>  			res = MF_RECOVERED;
>  		}
> @@ -1698,8 +1704,7 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
>  	 */
>  	if (res == 0) {
>  		unlock_page(head);
> -		res = MF_FAILED;

It seems the previous discussion in [1] is missed. But that doesn't matter as pointed out by [1]. :)

Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>

Thanks.

[1]: https://lkml.org/lkml/2022/6/8/10

> -		if (__page_handle_poison(p)) {
> +		if (__page_handle_poison(p) > 0) {
>  			page_ref_inc(p);
>  			res = MF_RECOVERED;
>  		}
>