linux-kernel - Re: [PATCH v4 00/15] mm, swap: introduce swap table as swap cache (phase I)

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Message-ID: <CAMgjq7Dx51gPWfE0eobNQBtMzUDwxuaZrrSDW=q2CsVqBamRZA@mail.gmail.com>
Date: Wed, 17 Sep 2025 11:53:32 +0800
From: Kairui Song <ryncsn@...il.com>
To: Hugh Dickins <hughd@...gle.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Matthew Wilcox <willy@...radead.org>, Chris Li <chrisl@...nel.org>, Barry Song <baohua@...nel.org>, 
	Baoquan He <bhe@...hat.com>, Nhat Pham <nphamcs@...il.com>, 
	Kemeng Shi <shikemeng@...weicloud.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>, 
	Ying Huang <ying.huang@...ux.alibaba.com>, Johannes Weiner <hannes@...xchg.org>, 
	David Hildenbrand <david@...hat.com>, Yosry Ahmed <yosryahmed@...gle.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Zi Yan <ziy@...dia.com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 00/15] mm, swap: introduce swap table as swap cache
 (phase I)

On Wed, Sep 17, 2025 at 5:23 AM Hugh Dickins <hughd@...gle.com> wrote:
>
> On Wed, 17 Sep 2025, Kairui Song wrote:
> > V4 changes:
> > - Patch 14: fix potential cluster leak when attemp a sleep allocation of
> >   swap table: Just remove the logic that check and return the percpu
> >   cluster, it was trying to avoid fragmentation, which wasn't very
> >   successfully and may not work at all if there are multiple devices.
> >   The fragmentation is not a serious issue and given the chance of
> >   hitting that race is extremely low, let's just ignore that [ Chris Meson ].
>
> And in Patch 11 I can see that you've made an important fix to the
> !folio_ref_freeze() block in __folio_migrate_mapping(): there had been a
> swap_cluster_unlock(ci) which you've fixed to swap_cluster_unlock_irq(ci):
> I was going to report that, with the WARNING and "BUG: sleeping function"s
> it caused, but you're ahead of me.

Oh thanks for pointing that out, I fixed that some time ago and forgot
to include it in the change log.

>
> Thanks also for fixing the shmem_replace_folio() locking and stats
> update, which I'd noticed too (but never hit): looks good now.
>
> Hugh
>
> > - Patch 8 & 9: move some changes from Patch 9 to Patch 8 to avoid build
> >   error, no code change. [ Baolin Wang ]
> > - Patch 9: Fix locking section issue, should protect the shmem statistic
> >   update with spin lock irq. Also fix an warn on condition.
> > Link to V3:
> > - https://lore.kernel.org/linux-mm/20250910160833.3464-1-ryncsn@gmail.com/