linux-kernel - Re: [RFC PATCH 0/2] mm: continue using per-VMA lock when retrying page faults after I/O

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Message-ID: <CAGsJ_4wvaieWtTrK+koM3SFu9rDExkVHX5eUwYiEotVqP-ndEQ@mail.gmail.com>
Date: Fri, 28 Nov 2025 05:52:40 +0800
From: Barry Song <21cnbao@...il.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	loongarch@...ts.linux.dev, linuxppc-dev@...ts.ozlabs.org, 
	linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org
Subject: Re: [RFC PATCH 0/2] mm: continue using per-VMA lock when retrying
 page faults after I/O

On Fri, Nov 28, 2025 at 4:29 AM Barry Song <21cnbao@...il.com> wrote:
>
> On Fri, Nov 28, 2025 at 3:43 AM Matthew Wilcox <willy@...radead.org> wrote:
> >
> > [dropping individuals, leaving only mailing lists.  please don't send
> > this kind of thing to so many people in future]

Apologies, I missed this one.

The output comes from ./scripts/get_maintainer.pl. If you think the group is
too large, I guess we should at least include Suren, Lorenzo, David, and
a few others in the discussion?

[...]

>
> >
> > This use case also manages to get utterly hung-up trying to do reclaim
> > today with the mmap_lock held.  SO it manifests somewhat similarly to
> > your problem (everybody ends up blocked on mmap_lock) but it has a
> > rather different root cause.

If I understand the use case correctly, I believe retrying with the per-VMA
lock would also be very helpful. Previously, we always retried using
mmap_lock, which can be difficult to acquire under heavy contention, leading
to long latency while the pages might be reclaimed. With the per-VMA lock, it
is much easier to hold and proceed with the work.

Thanks
Barry