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

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Message-ID: <CAGsJ_4xquj2Kbc2qu0vtY6Q+-q3sg56BgKEdPs8eHtKxLBk0gQ@mail.gmail.com>
Date: Fri, 7 Nov 2025 11:07:38 +0800
From: Barry Song <21cnbao@...il.com>
To: Kairui Song <ryncsn@...il.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Baoquan He <bhe@...hat.com>, Chris Li <chrisl@...nel.org>, Nhat Pham <nphamcs@...il.com>, 
	Johannes Weiner <hannes@...xchg.org>, Yosry Ahmed <yosry.ahmed@...ux.dev>, 
	David Hildenbrand <david@...hat.com>, Youngjun Park <youngjun.park@....com>, 
	Hugh Dickins <hughd@...gle.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>, 
	"Huang, Ying" <ying.huang@...ux.alibaba.com>, Kemeng Shi <shikemeng@...weicloud.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	"Matthew Wilcox (Oracle)" <willy@...radead.org>, linux-kernel@...r.kernel.org, 
	Kairui Song <kasong@...cent.com>
Subject: Re: [PATCH 13/19] mm, swap: remove workaround for unsynchronized swap
 map cache state

>  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