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Message-ID: <aDkKXOisEB43+i6J@MiWiFi-R3L-srv>
Date: Fri, 30 May 2025 09:31:08 +0800
From: Baoquan He <bhe@...hat.com>
To: Kemeng Shi <shikemeng@...weicloud.com>
Cc: akpm@...ux-foundation.org, kasong@...cent.com, hannes@...xchg.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] mm: swap: move nr_swap_pages counter decrement from
folio_alloc_swap() to swap_range_alloc()
On 05/22/25 at 08:25pm, Kemeng Shi wrote:
> When folio_alloc_swap() encounters a failure in either
> mem_cgroup_try_charge_swap() or add_to_swap_cache(), nr_swap_pages counter
> is not decremented for allocated entry. However, the following
> put_swap_folio() will increase nr_swap_pages counter unpairly and lead to
> an imbalance.
>
> Move nr_swap_pages decrement from folio_alloc_swap() to swap_range_alloc()
> to pair the nr_swap_pages counting.
>
> Fixes: 0ff67f990bd45 ("mm, swap: remove swap slot cache")
> Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
> ---
> mm/swapfile.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
LGTM,
Reviewed-by: Baoquan He <bhe@...hat.com>
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 026090bf3efe..75b69213c2e7 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1115,6 +1115,7 @@ static void swap_range_alloc(struct swap_info_struct *si,
> if (vm_swap_full())
> schedule_work(&si->reclaim_work);
> }
> + atomic_long_sub(nr_entries, &nr_swap_pages);
> }
>
> static void swap_range_free(struct swap_info_struct *si, unsigned long offset,
> @@ -1313,7 +1314,6 @@ int folio_alloc_swap(struct folio *folio, gfp_t gfp)
> if (add_to_swap_cache(folio, entry, gfp | __GFP_NOMEMALLOC, NULL))
> goto out_free;
>
> - atomic_long_sub(size, &nr_swap_pages);
> return 0;
>
> out_free:
> --
> 2.30.0
>
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