linux-kernel - Re: [PATCH -V3 1/5] swap: Remove get/put_swap_device() in __swap

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Date:   Thu, 1 Jun 2023 22:53:16 -0700
From:   Chris Li <chrisl@...nel.org>
To:     Huang Ying <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Yosry Ahmed <yosryahmed@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        Minchan Kim <minchan@...nel.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>, Yu Zhao <yuzhao@...gle.com>
Subject: Re: [PATCH -V3 1/5] swap: Remove get/put_swap_device() in
 __swap_count()

On Mon, May 29, 2023 at 02:13:51PM +0800, Huang Ying wrote:
> get/put_swap_device() are added to __swap_count() in commit
> eb085574a752 ("mm, swap: fix race between swapoff and some swap
> operations").  Later, in commit 2799e77529c2 ("swap: fix
> do_swap_page() race with swapoff"), get/put_swap_device() are added to
> do_swap_page().  And they enclose the only call site of
> __swap_count().  So, it's safe to remove get/put_swap_device() in
> __swap_count() now.
> 
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Reviewed-by: Yosry Ahmed <yosryahmed@...gle.com>
> Reviewed-by: David Hildenbrand <david@...hat.com>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Tim Chen <tim.c.chen@...ux.intel.com>
> Cc: Yang Shi <shy828301@...il.com>
> Cc: Yu Zhao <yuzhao@...gle.com>
> Cc: Chris Li <chrisl@...nel.org>

Reviewed-By: Chris Li (Google) <chrisl@...nel.org>

Chris

> ---
>  mm/swapfile.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 274bbf797480..8419cba9c192 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1432,16 +1432,10 @@ void swapcache_free_entries(swp_entry_t *entries, int n)
>  
>  int __swap_count(swp_entry_t entry)
>  {
> -	struct swap_info_struct *si;
> +	struct swap_info_struct *si = swp_swap_info(entry);
>  	pgoff_t offset = swp_offset(entry);
> -	int count = 0;
>  
> -	si = get_swap_device(entry);
> -	if (si) {
> -		count = swap_count(si->swap_map[offset]);
> -		put_swap_device(si);
> -	}
> -	return count;
> +	return swap_count(si->swap_map[offset]);
>  }
>  
>  /*
> -- 
> 2.39.2
>