linux-kernel - Re: [PATCH] Revert "mm, swap: avoid redundant swap device pinning"

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Message-ID: <CAMgjq7C5H0rV4tkosUEtwvHTd5bO+jxyQkW4xjP+8-qnjh=oiA@mail.gmail.com>
Date: Mon, 10 Nov 2025 20:33:31 +0800
From: Kairui Song <ryncsn@...il.com>
To: "Huang, Ying" <ying.huang@...ux.alibaba.com>
Cc: Kairui Song via B4 Relay <devnull+kasong.tencent.com@...nel.org>, linux-mm@...ck.org, 
	Andrew Morton <akpm@...ux-foundation.org>, Kemeng Shi <shikemeng@...weicloud.com>, 
	Nhat Pham <nphamcs@...il.com>, Baoquan He <bhe@...hat.com>, Barry Song <baohua@...nel.org>, 
	Chris Li <chrisl@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Yosry Ahmed <yosry.ahmed@...ux.dev>, Chengming Zhou <chengming.zhou@...ux.dev>, 
	Youngjun Park <youngjun.park@....com>, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Subject: Re: [PATCH] Revert "mm, swap: avoid redundant swap device pinning"

On Mon, Nov 10, 2025 at 7:37 PM Kairui Song <ryncsn@...il.com> wrote:
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 3f85a1c4cfd9..4cca4865627f 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -747,6 +747,7 @@ static struct folio
> *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
>
>         blk_start_plug(&plug);
>         for (addr = start; addr < end; ilx++, addr += PAGE_SIZE) {
> +               struct swap_info_struct *si = NULL;
>                 leaf_entry_t entry;
>
>                 if (!pte++) {
> @@ -761,8 +762,12 @@ static struct folio
> *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
>                         continue;
>                 pte_unmap(pte);
>                 pte = NULL;
> +               if (swp_type(entry) != swp_type(targ_entry))
> +                       si = get_swap_device(entry);

Oops I missed a NULL check here.


>                 folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx,
>                                                 &page_allocated, false);
> +               if (si)
> +                       put_swap_device(si);
>                 if (!folio)
>                         continue;
>                 if (page_allocated) {
>
> I'll post a patch if it looks ok.