From: Christoph Hellwig <hch@infradead.org>
To: Vyacheslav Kovalevsky <slava.kovalevskiy.2014@gmail.com>
Cc: tytso@mit.edu, adilger.kernel@dilger.ca,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Writing more than 4096 bytes with O_SYNC flag does not persist all previously written data if system crashes
Date: Tue, 24 Feb 2026 06:47:19 -0800 [thread overview]
Message-ID: <aZ2599dwNuqPQgzB@infradead.org> (raw)
In-Reply-To: <3d8f73f4-3a64-4a86-8fc9-d910d4fa3be1@gmail.com>
A lot of folks have already explained the O_SYNC semantics correctly,
but I have another major question about your test case.
On Wed, Feb 18, 2026 at 04:29:30PM +0300, Vyacheslav Kovalevsky wrote:
> Detailed description
> ====================
>
> Hello, there seems to be an issue with ext4 crash behavior:
>
> 1. Create and sync a new file.
> 2. Open the file and write some data (must be more than 4096 bytes).
> 3. Close the file.
> 4. Open the file with O_SYNC flag and write some data.
>
> After system crash the file will have the wrong size and some previously
> written data will be lost.
The wrong size here seems incorrect. Even if the old data written
through the non-O_SYNC fd wasn't written out I absolutely can't see how
the file would have an incorrect size here. Can you please share your
test case?
next prev parent reply other threads:[~2026-02-24 14:47 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-18 13:29 Writing more than 4096 bytes with O_SYNC flag does not persist all previously written data if system crashes Vyacheslav Kovalevsky
2026-02-18 21:55 ` Andreas Dilger
2026-02-19 13:32 ` Theodore Tso
2026-02-23 12:46 ` Alejandro Colomar
2026-02-23 19:32 ` Theodore Tso
2026-02-24 1:21 ` Andreas Dilger
2026-03-03 13:19 ` Alejandro Colomar
2026-02-24 14:47 ` Christoph Hellwig [this message]
2026-02-24 22:23 ` Darrick J. Wong
2026-02-25 14:20 ` Christoph Hellwig
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