Re: [PATCH 13/19] mm, swap: remove workaround for unsynchronized swap map cache state

[Barry Song <21cnbao@gmail.com>]

>  struct folio *swap_cache_alloc_folio(swp_entry_t entry, gfp_t gfp_mask,
>                                      struct mempolicy *mpol, pgoff_t ilx,
> -                                    bool *new_page_allocated,
> -                                    bool skip_if_exists)
> +                                    bool *new_page_allocated)
>  {
>         struct swap_info_struct *si = __swap_entry_to_info(entry);
>         struct folio *folio;
> @@ -548,8 +542,7 @@ struct folio *swap_cache_alloc_folio(swp_entry_t entry, gfp_t gfp_mask,
>         if (!folio)
>                 return NULL;
>         /* Try add the new folio, returns existing folio or NULL on failure. */
> -       result = __swap_cache_prepare_and_add(entry, folio, gfp_mask,
> -                                             false, skip_if_exists);
> +       result = __swap_cache_prepare_and_add(entry, folio, gfp_mask, false);
>         if (result == folio)
>                 *new_page_allocated = true;
>         else
> @@ -578,7 +571,7 @@ struct folio *swapin_folio(swp_entry_t entry, struct folio *folio)
>         unsigned long nr_pages = folio_nr_pages(folio);
>
>         entry = swp_entry(swp_type(entry), round_down(offset, nr_pages));
> -       swapcache = __swap_cache_prepare_and_add(entry, folio, 0, true, false);
> +       swapcache = __swap_cache_prepare_and_add(entry, folio, 0, true);
>         if (swapcache == folio)
>                 swap_read_folio(folio, NULL);
>         return swapcache;

I wonder if we could also drop the "charged" — it doesn’t seem
difficult to move the charging step before
__swap_cache_prepare_and_add(), even for swap_cache_alloc_folio()?

Thanks
Barry