Re: [PATCH -V2 3/5] swap: remove __swp_swapcount()

[David Hildenbrand]

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@xxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> Cc: Yang Shi <shy828301@xxxxxxxxx>
> Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
> ---
>   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