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Date:   Wed, 5 Jul 2023 16:35:41 -0700
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     Jiaqi Yan <jiaqiyan@google.com>
Cc:     naoya.horiguchi@nec.com, songmuchun@bytedance.com,
        shy828301@gmail.com, linmiaohe@huawei.com,
        akpm@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, duenwen@google.com,
        axelrasmussen@google.com, jthoughton@google.com
Subject: Re: [PATCH v2 1/4] mm/hwpoison: delete all entries before traversal
 in __folio_free_raw_hwp
Message-ID: <20230705233541.GC41006@monkey>
References: <20230623164015.3431990-1-jiaqiyan@google.com>
 <20230623164015.3431990-2-jiaqiyan@google.com>
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On 06/23/23 16:40, Jiaqi Yan wrote:
> Traversal on llist (e.g. llist_for_each_safe) is only safe AFTER entries
> are deleted from the llist.
> 
> llist_del_all are lock free with itself. folio_clear_hugetlb_hwpoison()s
> from __update_and_free_hugetlb_folio and memory_failure won't need
> explicit locking when freeing the raw_hwp_list.
> 
> Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> ---
>  mm/memory-failure.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)

After updating the reason for patch in commit message as suggested by Naoya,

Acked-by: Mike Kravetz <mike.kravetz@oracle.com>

-- 
Mike Kravetz

> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 004a02f44271..c415c3c462a3 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1825,12 +1825,11 @@ static inline struct llist_head *raw_hwp_list_head(struct folio *folio)
>  
>  static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
>  {
> -	struct llist_head *head;
> -	struct llist_node *t, *tnode;
> +	struct llist_node *t, *tnode, *head;
>  	unsigned long count = 0;
>  
> -	head = raw_hwp_list_head(folio);
> -	llist_for_each_safe(tnode, t, head->first) {
> +	head = llist_del_all(raw_hwp_list_head(folio));
> +	llist_for_each_safe(tnode, t, head) {
>  		struct raw_hwp_page *p = container_of(tnode, struct raw_hwp_page, node);
>  
>  		if (move_flag)
> @@ -1840,7 +1839,6 @@ static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag)
>  		kfree(p);
>  		count++;
>  	}
> -	llist_del_all(head);
>  	return count;
>  }
>  
> -- 
> 2.41.0.162.gfafddb0af9-goog
>