linux-kernel - Re: [PATCH 2/3] proc: kpagecount: use snapshot

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Message-Id: <20250627183056.52582-1-sj@kernel.org>
Date: Fri, 27 Jun 2025 11:30:56 -0700
From: SeongJae Park <sj@...nel.org>
To: Luiz Capitulino <luizcap@...hat.com>
Cc: SeongJae Park <sj@...nel.org>,
	david@...hat.com,
	willy@...radead.org,
	akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	lcapitulino@...il.com,
	shivankg@....com
Subject: Re: [PATCH 2/3] proc: kpagecount: use snapshot_page()

On Thu, 26 Jun 2025 14:16:52 -0400 Luiz Capitulino <luizcap@...hat.com> wrote:

> Currently, the call to folio_precise_page_mapcount() from kpage_read()
> can race with a folio split. When the race happens we trigger a
> VM_BUG_ON_FOLIO() in folio_entire_mapcount() (see splat below).
> 
> This commit fixes this race by using snapshot_page() so that we
> retreive the folio mapcount using a folio snapshot.
[...]
> Signed-off-by: Luiz Capitulino <luizcap@...hat.com>

Acked-by: SeongJae Park <sj@...nel.org>


Thanks,
SJ

[...]