From: "Zi Yan" <ziy@nvidia.com>
To: "Matthew Wilcox" <willy@infradead.org>,
"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 15:05:16 -0400 [thread overview]
Message-ID: <DJMM9V4Z58QP.2DXAKKZ4YE6HA@nvidia.com> (raw)
In-Reply-To: <akQMy54dxVTVkMJ6@casper.infradead.org>
On Tue Jun 30, 2026 at 2:36 PM EDT, Matthew Wilcox wrote:
> 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.
Maybe he means order-0 dirty folios?
--
Best Regards,
Yan, Zi
next prev parent reply other threads:[~2026-06-30 19:05 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
2026-06-30 19:05 ` Zi Yan [this message]
2026-06-30 19:07 ` Matthew Wilcox
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