linux-ext4 - Re: ext4 v6.15-rc2 baseline

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Message-ID: <20250419182249.GC210438@mit.edu>
Date: Sat, 19 Apr 2025 13:22:49 -0500
From: "Theodore Ts'o" <tytso@....edu>
To: Luis Chamberlain <mcgrof@...nel.org>
Cc: "Darrick J. Wong" <djwong@...nel.org>, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, kdevops@...ts.linux.dev, dave@...olabs.net,
        jack@...e.cz
Subject: Re: ext4 v6.15-rc2 baseline

On Thu, Apr 17, 2025 at 01:56:29PM -0700, Luis Chamberlain wrote:
> 
> Perhaps something like (not tested):
> 
> From a9386348701e387942e3eaaef8ee9daac8ace16a Mon Sep 17 00:00:00 2001
> From: Luis Chamberlain <mcgrof@...nel.org>
> Date: Thu, 17 Apr 2025 13:54:25 -0700
> Subject: [PATCH] ext4: add ordered requirement for generic/04[456]
> 
> generic/04[456] tests how truncate and delayed allocation works.
> ext4 uses the data=ordered to avoid exposing stale data, and
> so it uses a different mechanism than xfs. So these tests will fail
> on it.

No, you misunderstand the problem.  The generic/04[456] tests are
checking for a specific implementation detail in how xfs works to
prevent stale data from being exposing data after a crash.  Ext4 has a
different method for achieving the same goal, using data=ordered,
which is the default.  So checking for data=ordered isn't necessary,
because it is the default.  But how it achieves thinigs means that
these tests, which tests for a specific implementation, doesn't work.

Fundamentally, these tests check what happens when you are writing to
a file and the file system is shutdown (simulating a power failure).
Exaclty how this handled is not guaranteed by POSIX, so testing for a
specific behaviour is in my opinion, not really that great of an idea.
In any case, the fact that we don't do exactly what these tests are
expecting is not a problem as far as I'm concerned, and so we skip
them.

Cheers,

						- Ted