linux-kernel - Re: Directory is not persisted after writing to the file within directory if system crashes

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Message-ID: <aP8dBBlWgpGB4OCQ@infradead.org>
Date: Mon, 27 Oct 2025 00:19:32 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Filipe Manana <fdmanana@...nel.org>
Cc: Vyacheslav Kovalevsky <slava.kovalevskiy.2014@...il.com>, clm@...com,
	dsterba@...e.com, linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Directory is not persisted after writing to the file within
 directory if system crashes

On Sun, Oct 26, 2025 at 09:04:13AM +0000, Filipe Manana wrote:
> >
> > The test itself is quite weird (why would `dir` be gone after seemingly
> > unrelated operation?), any detail can matter.
> 
> "dir" should be persisted as well as "dir/file2", according to the
> SOMC (Strictly Ordered Metadata Consistency) that Dave Chinner
> discussed many times in the past in fstests and btrfs mailing lists.
> 
> You should also reach the xfs mailing list and mention that
> "dir/file2" is not persisted.

No.  The fsync is on the root directory.  So the only thing that is
needed to per persisted is transactions touching that.  The transaction
to created dir is persisted because it is an entry in the root directly.
creating and writing to file2 has nothing to do with the root directly
and absolutely should not be effected by an fsync on an unrelated inode.