Re: [PATCH 7/9] mm: swap: free each cluster individually in swap_entries_put_map_nr()

[Tim Chen <tim.c.chen@linux.intel.com>]

On Fri, 2025-03-14 at 05:05 +0800, Kemeng Shi wrote:
> 1. Factor out general swap_entries_put_map() helper to drop entries belong
> to one cluster. If entries are last map, free entries in batch, otherwise
> put entries with cluster lock acquired and released only once.
> 2. Iterate and call swap_entries_put_map() for each cluster in
> swap_entries_put_nr() to leverage batch-remove for last map belong to one
> cluster and reduce lock acquire/release in fallback case.
> 3. As swap_entries_put_nr() won't handle SWAP_HSA_CACHE drop, rename it to
> swap_entries_put_map_nr().
> 
> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
> ---
>  mm/swapfile.c | 58 +++++++++++++++++++++++++--------------------------
>  1 file changed, 29 insertions(+), 29 deletions(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 2d0f5d630211..ebac9ff74ba7 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1473,25 +1473,10 @@ struct swap_info_struct *get_swap_device(swp_entry_t entry)
>  	return NULL;
>  }
>  
> -static unsigned char swap_entry_put(struct swap_info_struct *si,
> -				    swp_entry_t entry)

Need to update comment in free_swap_and_cache_nr() now that swap_entry_put() goes away.

         * the swap once per folio in the common case. If we do
         * swap_entry_put() and __try_to_reclaim_swap() in the same loop, the
         * latter will get a reference and lock the folio for every individual ...


> +static bool swap_entries_put_map(struct swap_info_struct *si,
> +				 swp_entry_t entry, int nr)
>  {
> -	struct swap_cluster_info *ci;
>  	unsigned long offset = swp_offset(entry);
> -	unsigned char usage;
> -
> -	ci = lock_cluster(si, offset);
> -	usage = swap_entry_put_locked(si, ci, entry, 1);
> -	unlock_cluster(ci);
> -
> -	return usage;
> -}
> -