Re: [PATCH v3 4/4] mm, swap: drop the swap cache guard and reclaim in swap_free_hibernation_slot()

[Kairui Song]

On Tue, Aug 11, 2026 at 10:22:09PM +0800, Youngjun Park wrote:
> Both are there for a folio that readahead might have put on the slot.  A
> hibernation entry is not a shadow and has no swap count, so the swap cache
> turns it away and no such folio can exist.
> 
> Signed-off-by: Youngjun Park <youngjun.park@xxxxxxx>
> ---
>  mm/swapfile.c | 12 +-----------
>  1 file changed, 1 insertion(+), 11 deletions(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index a337387f7431..4fba1770ce61 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -2203,18 +2203,8 @@ void swap_free_hibernation_slot(swp_entry_t entry)
>  	pgoff_t offset = swp_offset(entry);
>  
>  	ci = swap_cluster_lock(si, offset);
> -	/*
> -	 * A slot with a folio in the swap cache is freed when the folio
> -	 * leaves the cache, the same rule swap_put_entries_cluster() follows.
> -	 * Readahead can put a folio here, and freeing the slot now would
> -	 * leave that folio with no entry behind it.
> -	 */
> -	if (!swp_tb_is_folio(__swap_table_get(ci, offset % SWAPFILE_CLUSTER)))
> -		__swap_cluster_free_entries(si, ci, offset % SWAPFILE_CLUSTER, 1);
> +	__swap_cluster_free_entries(si, ci, offset % SWAPFILE_CLUSTER, 1);
>  	swap_cluster_unlock(ci);
> -
> -	/* In theory readahead might add it to the swap cache by accident */
> -	__try_to_reclaim_swap(si, offset, TTRS_ANYWAY);

Nice to see this gets cleaned up.

Acked-by: Kairui Song <kasong@xxxxxxxxxxx>