linux-ext4 - Re: File name is not persisted if opened with O_SYNC and O

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Message-ID: <4870d506-e29f-4c68-8d93-03aa3a931fa1@gmail.com>
Date: Fri, 13 Feb 2026 13:25:20 +0300
From: Vyacheslav Kovalevsky <slava.kovalevskiy.2014@...il.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: viro@...iv.linux.org.uk, brauner@...nel.org,
 linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: File name is not persisted if opened with O_SYNC and O_TRUNC
 flags

On 13/02/2026 10:33, Christoph Hellwig wrote:
> On Thu, Feb 12, 2026 at 02:51:47PM +0300, Vyacheslav Kovalevsky wrote:
>> Detailed description ==================== Hello, there seems to be an 
>> issue with O_SYNC flag when used together with O_TRUNC on various 
>> file systems. Opening a file with O_SYNC (or using fsync(fd)) should 
>> persist directory entry. 
> No, it should not. I'm not sure who hallucinated, but O_SYNC has 
> always always applied to persistency semantics after writes and 
> nothing else.
You are right, opening file with O_SYNC does not persist anything and 
ftruncate or O_TRUNC do not count as write I/O it seems. Also found an 
error related to these assumptions in our testing tool. Thanks.