linux-kernel - Re: [PATCH -V2 3/5] swap: remove __swp

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Message-ID: <200a094f-7ca9-8a64-1c9b-7cf2e546f3eb@redhat.com>
Date:   Mon, 22 May 2023 14:03:36 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Huang Ying <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        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 -V2 3/5] swap: remove __swp_swapcount()

On 22.05.23 09:09, Huang Ying wrote:
> __swp_swapcount() just encloses the calling to swap_swapcount() with
> get/put_swap_device().  It is called in __read_swap_cache_async()
> only, which encloses the calling with get/put_swap_device() already.
> So, __read_swap_cache_async() can call swap_swapcount() directly.

The previous patch contained the hunk

-		if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
-			return NULL;
+		if (!swap_swapcount(si, entry) && swap_slot_cache_enabled)
+			goto fail;
  

So something is a bit off here. Either that hunk should go here, or
this patch description has to be adjusted.


But I guess patch #2 doesn't compile on its own because this patch
here adds swap_swapcount() to include/linux/swap.h ?

> 
> Signed-off-by: "Huang, Ying" <ying.huang@...el.com>
> Cc: 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>
> ---
>   include/linux/swap.h |  4 ++--
>   mm/swapfile.c        | 20 +-------------------
>   2 files changed, 3 insertions(+), 21 deletions(-)
> 
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 3c69cb653cb9..f6bd51aa05ea 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -512,7 +512,7 @@ int find_first_swap(dev_t *device);
>   extern unsigned int count_swap_pages(int, int);
>   extern sector_t swapdev_block(int, pgoff_t);
>   extern int __swap_count(swp_entry_t entry);
> -extern int __swp_swapcount(swp_entry_t entry);
> +extern int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry);
>   extern int swp_swapcount(swp_entry_t entry);
>   extern struct swap_info_struct *page_swap_info(struct page *);
>   extern struct swap_info_struct *swp_swap_info(swp_entry_t entry);
> @@ -590,7 +590,7 @@ static inline int __swap_count(swp_entry_t entry)
>   	return 0;
>   }
>   
> -static inline int __swp_swapcount(swp_entry_t entry)
> +static inline int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
>   {
>   	return 0;
>   }
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 8419cba9c192..e9cce775fb25 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1443,7 +1443,7 @@ int __swap_count(swp_entry_t entry)
>    * This does not give an exact answer when swap count is continued,
>    * but does include the high COUNT_CONTINUED flag to allow for that.
>    */
> -static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
> +int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
>   {
>   	pgoff_t offset = swp_offset(entry);
>   	struct swap_cluster_info *ci;
> @@ -1455,24 +1455,6 @@ static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry)
>   	return count;
>   }
>   
> -/*
> - * How many references to @entry are currently swapped out?
> - * This does not give an exact answer when swap count is continued,
> - * but does include the high COUNT_CONTINUED flag to allow for that.
> - */
> -int __swp_swapcount(swp_entry_t entry)
> -{
> -	int count = 0;
> -	struct swap_info_struct *si;
> -
> -	si = get_swap_device(entry);
> -	if (si) {
> -		count = swap_swapcount(si, entry);
> -		put_swap_device(si);
> -	}
> -	return count;
> -}
> -
>   /*
>    * How many references to @entry are currently swapped out?
>    * This considers COUNT_CONTINUED so it returns exact answer.

-- 
Thanks,

David / dhildenb