From: "Chris Mason" <mason@kernel.org>
To: "Christoph Hellwig" <hch@lst.de>
Cc: "Theodore Tso" <tytso@mit.edu>,
"Carlos Maiolino" <cem@kernel.org>,
"Dave Chinner" <david@fromorbit.com>, "Jan Kara" <jack@suse.cz>,
"Darrick J. Wong" <djwong@kernel.org>,
"Josef Bacik" <josef@toxicpanda.com>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-ext4@vger.kernel.org, "Tal Zussman" <tz2294@columbia.edu>,
"Christian Brauner" <brauner@kernel.org>
Subject: Re: [PATCH v8 13/15] xfs: resample the extsize hint after taking the ILOCK
Date: Thu, 12 Nov 2026 08:49:26 -0500 [thread overview]
Message-ID: <b1d12342-ea96-4a4e-9049-af5345fe9b30@app.fastmail.com> (raw)
In-Reply-To: <20261112133555.GC22165@lst.de>
On Thu, Nov 12, 2026, at 8:35 AM, Christoph Hellwig wrote:
> On Wed, Nov 11, 2026 at 08:02:42PM -0500, Chris Mason wrote:
>> A write fault on a file with an extent size hint can overrun its block
>> reservation and shut down the filesystem, if it races with a change of
>> the hint or of the realtime flag.
>>
>> xfs_iomap_write_direct() sizes the reservation from the hint and the
>> flag before xfs_trans_alloc_inode() takes the ILOCK, and the allocator
>> reads both again under it. But a write fault only holds the MMAPLOCK,
>> and FS_IOC_FSSETXATTR changes both on a file with no blocks without it:
>>
>
> ... and my previous suggestion of taking the mmlock in fileattr_set
> would take care of this as well.
Yes, it would simplify a lot of this. I went this route because I thought it was
nicer to have just the ILOCK control these things, but it would be easy to respin
with the mmlock.
-chris
next prev parent reply other threads:[~2026-11-12 13:49 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-12 1:02 [PATCH v8 00/15] reflink and atomic write bugs Chris Mason
2026-11-12 1:02 ` [PATCH v8 01/15] xfs: don't skip the flush before shifting extents Chris Mason
2026-11-12 1:02 ` [PATCH v8 02/15] xfs: flush the shifted range before changing the file Chris Mason
2026-11-12 1:02 ` [PATCH v8 03/15] xfs: don't change the block map under a dirty folio Chris Mason
2026-11-12 1:02 ` [PATCH v8 04/15] iomap: don't punch delalloc under a dirty EOF block Chris Mason
2026-11-12 1:02 ` [PATCH v8 05/15] fs: validate atomic writes after O_APPEND and limits Chris Mason
2026-11-12 1:02 ` [PATCH v8 06/15] xfs: recheck direct write alignment after write checks Chris Mason
2026-11-12 1:02 ` [PATCH v8 07/15] xfs: test for reflink after the dio " Chris Mason
2026-11-12 1:02 ` [PATCH v8 08/15] xfs: refuse writes to files racing with realtime inode flag changes Chris Mason
2026-11-12 1:02 ` [PATCH v8 09/15] xfs: test for always COW after the dio write checks Chris Mason
2026-11-12 1:02 ` [PATCH v8 10/15] xfs: refuse fallocate racing with realtime flag changes Chris Mason
2026-11-12 1:02 ` [PATCH v8 11/15] xfs: restart faults " Chris Mason
2026-11-12 13:34 ` Christoph Hellwig
2026-11-12 1:02 ` [PATCH v8 12/15] xfs: test for an extsize hint again under the ILOCK Chris Mason
2026-11-12 13:35 ` Christoph Hellwig
2026-11-12 1:02 ` [PATCH v8 13/15] xfs: resample the extsize hint after taking " Chris Mason
2026-11-12 13:35 ` Christoph Hellwig
2026-11-12 13:49 ` Chris Mason [this message]
2026-11-12 1:02 ` [PATCH v8 14/15] xfs: resample the COW extsize hint after cycling ILOCK Chris Mason
2026-11-12 13:36 ` Christoph Hellwig
2026-11-12 1:02 ` [PATCH v8 15/15] xfs: don't enable DAX on zoned inodes Chris Mason
2026-11-12 13:39 ` Christoph Hellwig
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