linux-kernel - Re: [PATCH 14/19] mm, swap: sanitize swap entry management workflow

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Message-ID: <aQXOESm58xvqS7sx@yjaykim-PowerEdge-T330>
Date: Sat, 1 Nov 2025 18:08:33 +0900
From: YoungJun Park <youngjun.park@....com>
To: Kairui Song <ryncsn@...il.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Baoquan He <bhe@...hat.com>, Barry Song <baohua@...nel.org>,
	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>,
	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
Subject: Re: [PATCH 14/19] mm, swap: sanitize swap entry management workflow

On Sat, Nov 01, 2025 at 04:59:05PM +0800, Kairui Song wrote:
> On Sat, Nov 1, 2025 at 12:51 PM YoungJun Park <youngjun.park@....com> wrote:
> >
> > On Wed, Oct 29, 2025 at 11:58:40PM +0800, Kairui Song wrote:
> > > From: Kairui Song <kasong@...cent.com>

> > During the code review, I found something to be verified.
> > It is not directly releavant your patch,
> > I send the email for checking it right and possible fix on this patch.
> >
> > on the swap_alloc_hibernation_slot function
> > nr_swap_pages is decreased. but as I think it is decreased on swap_range_alloc.
> >
> > The nr_swap_pages are decremented as the callflow as like the below.
> >
> > cluster_alloc_swap_entry -> alloc_swap_scan_cluster
> > -> closter_alloc_range -> swap_range_alloc
> >
> > Introduced on
> > 4f78252da887ee7e9d1875dd6e07d9baa936c04f
> > mm: swap: move nr_swap_pages counter decrement  from folio_alloc_swap() to swap_range_alloc()
> >
> 
> Yeah, you are right, that's a bug introduced by 4f78252da887, will you
> send a patch to fix that ? Or I can send one, just remove the
> atomic_long_dec(&nr_swap_pages) in get_swap_page_of_type then we are
> fine.

Thank you for double check. I will send a patch soon.

Regards,
Youngjun Park