linux-kernel - Re: [PATCH v1 3/5] mm, hwpoison: make __page_handle

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Message-ID: <9d423acb-b671-1cf0-0432-76eb648de95b@huawei.com>
Date:   Tue, 7 Jun 2022 20:54:24 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>
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>, Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH v1 3/5] mm, hwpoison: make __page_handle_poison returns
 int

On 2022/6/2 13:06, 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 fe6a7961dc66..f149a7864c81 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -68,7 +68,13 @@ int sysctl_memory_failure_recovery __read_mostly = 1;
>  
>  atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
>  
> -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;
>  
> @@ -78,7 +84,7 @@ 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)
> @@ -88,7 +94,7 @@ 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
> @@ -1045,7 +1051,7 @@ static int me_huge_page(struct page_state *ps, struct page *p)
>  		 * save healthy subpages.
>  		 */
>  		put_page(hpage);
> -		if (__page_handle_poison(p)) {
> +		if (__page_handle_poison(p) > 0) {
>  			page_ref_inc(p);
>  			res = MF_RECOVERED;
>  		}
> @@ -1595,8 +1601,7 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
>  	 */
>  	if (res == 0) {
>  		unlock_page(head);
> -		res = MF_FAILED;

This looks like an unexpected change. res will be 0 instead of MF_FAILED if __page_handle_poison failed to
dissolve or not taken off from buddy. But this is fixed in later patch in this series. So it should be fine.

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

Thanks!

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