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From: SeongJae Park <sj@kernel.org>
To: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: SeongJae Park <sj@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	damon@lists.linux.dev
Subject: Re: [PATCH v2 2/3] mm/damon/paddr: minor refactor of damon_pa_young()
Date: Fri,  3 Mar 2023 18:39:25 +0000
Message-Id: <20230303183925.113520-1-sj@kernel.org>
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In-Reply-To: <20230303084343.171958-3-wangkefeng.wang@huawei.com>
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Hi Kefeng,

On Fri, 3 Mar 2023 16:43:42 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote:

> Omit three lines by unified folio_put(), and make code more clear.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  mm/damon/paddr.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
> index 3fda00a0f786..2ef9db0189ca 100644
> --- a/mm/damon/paddr.c
> +++ b/mm/damon/paddr.c
> @@ -130,24 +130,21 @@ static bool damon_pa_young(unsigned long paddr, unsigned long *folio_sz)
>  			accessed = false;
>  		else
>  			accessed = true;
> -		folio_put(folio);
>  		goto out;

Because you moved 'out' label to not include *folio_sz setting, folio_sz will
not set in this case.  It should be set.

>  	}
>  
>  	need_lock = !folio_test_anon(folio) || folio_test_ksm(folio);
> -	if (need_lock && !folio_trylock(folio)) {
> -		folio_put(folio);
> -		return false;
> -	}
> +	if (need_lock && !folio_trylock(folio))
> +		goto out;
>  
>  	rmap_walk(folio, &rwc);
>  
>  	if (need_lock)
>  		folio_unlock(folio);
> -	folio_put(folio);
>  
> -out:
>  	*folio_sz = folio_size(folio);
> +out:
> +	folio_put(folio);

Before this change, folio_size() is called after folio_put().  Shouldn't it be
called before folio_put()?  If so, could we make a separate fix for that first,
and then make this change on top of it, so that it can be easily applied to
relevant stable kernels?


Thanks,
SJ

>  	return accessed;
>  }
>  
> -- 
> 2.35.3
> 
>