From: Matthew Wilcox <willy@infradead.org>
To: Gregg Leventhal <gleventhal@janestreet.com>
Cc: "To: Alexander Viro" <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>,
"Cc: Jan Kara" <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Song Liu <song@kernel.org>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Eric Hagberg <ehagberg@janestreet.com>
Subject: Re: Subject: [BUG/RFC] write-open file THP cache purge can discard dirty page cache
Date: Tue, 30 Jun 2026 19:36:59 +0100 [thread overview]
Message-ID: <akQMy54dxVTVkMJ6@casper.infradead.org> (raw)
In-Reply-To: <CAFN_u7H_0ECF3jixP=T=U7AH5=Q3wQNvJMo8an3VqUDMerQfUw@mail.gmail.com>
On Tue, Jun 30, 2026 at 01:01:53PM -0400, Gregg Leventhal wrote:
> On an affected 6.12 kernel with CONFIG_READ_ONLY_THP_FOR_FS=y, a file can
> contain read-only file THPs installed by khugepaged / MADV_COLLAPSE. When that
> same file is later opened for write, do_dentry_open() notices
> filemap_nr_thps() and drops the page cache:
[...]
>
> This is unsafe if the mapping also contains dirty folios.
But there shouldn't be any. It should not be possible to have
dirty folios and THPs in the same file unless the filesystem
supports large folios natively.
If the file is open for writing, the attempt to create THPs should fail.
next prev parent reply other threads:[~2026-06-30 18:37 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-30 17:01 Subject: [BUG/RFC] write-open file THP cache purge can discard dirty page cache Gregg Leventhal
2026-06-30 17:18 ` Gregg Leventhal
2026-06-30 18:31 ` Pedro Falcato
2026-06-30 18:49 ` Pedro Falcato
2026-06-30 19:55 ` Pedro Falcato
2026-06-30 22:34 ` Matthew Wilcox
2026-06-30 22:48 ` Zi Yan
2026-07-01 12:05 ` Pedro Falcato
2026-07-01 11:54 ` Matthew Wilcox
2026-07-01 12:04 ` Pedro Falcato
2026-07-01 12:48 ` Pedro Falcato
2026-07-01 13:07 ` Gregg Leventhal
2026-07-01 14:23 ` Pedro Falcato
2026-06-30 18:36 ` Matthew Wilcox [this message]
2026-06-30 19:05 ` Zi Yan
2026-06-30 19:07 ` Matthew Wilcox
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