linux-kernel - Re: [mm-unstable PATCH v6 4/8] mm, hwpoison: make unpoison aware of raw error info in hwpoisoned hugepage

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Date:   Wed, 13 Jul 2022 12:24:46 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>, <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: [mm-unstable PATCH v6 4/8] mm, hwpoison: make unpoison aware of
 raw error info in hwpoisoned hugepage

On 2022/7/12 11:28, Naoya Horiguchi wrote:
> From: Naoya Horiguchi <naoya.horiguchi@....com>
> 
> Raw error info list needs to be removed when hwpoisoned hugetlb is
> unpoisoned.  And unpoison handler needs to know how many errors there
> are in the target hugepage. So add them.
> 
> HPageVmemmapOptimized(hpage) and HPageRawHwpUnreliable(hpage)) can't be
> unpoisoned, so let's skip them.
> 
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
> Reported-by: kernel test robot <lkp@...el.com>

This patch looks good to me with some nits below.

> ---
...
>  
> -void hugetlb_clear_page_hwpoison(struct page *hpage)
> +static unsigned long free_raw_hwp_pages(struct page *hpage, bool move_flag)
>  {
>  	struct llist_head *head;
>  	struct llist_node *t, *tnode;
> +	unsigned long count = 0;
>  
> -	if (!HPageRawHwpUnreliable(hpage))
> -		ClearPageHWPoison(hpage);
> +	/*
> +	 * HPageVmemmapOptimized hugepages can't be unpoisoned because
> +	 * struct pages for tail pages are required to free hwpoisoned
> +	 * hugepages.  HPageRawHwpUnreliable hugepages shouldn't be
> +	 * unpoisoned by definition.
> +	 */
> +	if (HPageVmemmapOptimized(hpage) || HPageRawHwpUnreliable(hpage))

If move_flag == false, i.e. in unpoison case, tail pages are not touched. So HPageVmemmapOptimized
can be ignored in this case? Or leave it as above to keep the code simple?

> +		return 0;
>  	head = raw_hwp_list_head(hpage);
>  	llist_for_each_safe(tnode, t, head->first) {
>  		struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
>  
> -		SetPageHWPoison(p->page);
> +		if (move_flag)
> +			SetPageHWPoison(p->page);
>  		kfree(p);
> +		count++;
>  	}
>  	llist_del_all(head);
> +	return count;
> +}
> +
> +void hugetlb_clear_page_hwpoison(struct page *hpage)
> +{
> +	if (!HPageRawHwpUnreliable(hpage))

It seems we can return here if HPageRawHwpUnreliable as there's nothing to do?

Anyway, for what it worth,

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

Thanks.

> +		ClearPageHWPoison(hpage);
> +	free_raw_hwp_pages(hpage, true);
>  }
>  
>  /*