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From: "Huang, Ying" <ying.huang@intel.com>
To: Barry Song <21cnbao@gmail.com>
Cc: akpm@linux-foundation.org,  linux-mm@kvack.org,
  baolin.wang@linux.alibaba.com,  chrisl@kernel.org,  david@redhat.com,
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  linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/5] mm: swap: make should_try_to_free_swap() support
 large-folio
In-Reply-To: <20240409082631.187483-3-21cnbao@gmail.com> (Barry Song's message
	of "Tue, 9 Apr 2024 20:26:28 +1200")
References: <20240409082631.187483-1-21cnbao@gmail.com>
	<20240409082631.187483-3-21cnbao@gmail.com>
Date: Mon, 15 Apr 2024 15:11:03 +0800
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Barry Song <21cnbao@gmail.com> writes:

> From: Chuanhua Han <hanchuanhua@oppo.com>
>
> The function should_try_to_free_swap() operates under the assumption that
> swap-in always occurs at the normal page granularity, i.e., folio_nr_pages
                                                              ~~~~~~~~~~~~~~

nits: folio_nr_pages() is better for understanding.

Otherwise, LGTM, Thanks!

Reviewed-by: "Huang, Ying" <ying.huang@intel.com>

> = 1. However, in reality, for large folios, add_to_swap_cache() will
> invoke folio_ref_add(folio, nr). To accommodate large folio swap-in,
> this patch eliminates this assumption.
>
> Signed-off-by: Chuanhua Han <hanchuanhua@oppo.com>
> Co-developed-by: Barry Song <v-songbaohua@oppo.com>
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> Acked-by: Chris Li <chrisl@kernel.org>
> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>

> ---
>  mm/memory.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 78422d1c7381..2702d449880e 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3856,7 +3856,7 @@ static inline bool should_try_to_free_swap(struct folio *folio,
>  	 * reference only in case it's likely that we'll be the exlusive user.
>  	 */
>  	return (fault_flags & FAULT_FLAG_WRITE) && !folio_test_ksm(folio) &&
> -		folio_ref_count(folio) == 2;
> +		folio_ref_count(folio) == (1 + folio_nr_pages(folio));
>  }
>  
>  static vm_fault_t pte_marker_clear(struct vm_fault *vmf)