linux-kernel - Re: [PATCH] ext4: remove obsolete EXT3 config options

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Message-ID: <20250827120237.GE1603531@mit.edu>
Date: Wed, 27 Aug 2025 08:02:37 -0400
From: "Theodore Ts'o" <tytso@....edu>
To: Lukas Bulwahn <lbulwahn@...hat.com>
Cc: Andreas Dilger <adilger.kernel@...ger.ca>, linux-ext4@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lukas Bulwahn <lukas.bulwahn@...hat.com>
Subject: Re: [PATCH] ext4: remove obsolete EXT3 config options

On Wed, Aug 27, 2025 at 11:08:08AM +0200, Lukas Bulwahn wrote:
> From: Lukas Bulwahn <lukas.bulwahn@...hat.com>
> 
> In June 2015, commit c290ea01abb7 ("fs: Remove ext3 filesystem driver")
> removed the historic ext3 filesystem support as ext3 partitions are fully
> supported with the ext4 filesystem support. To simplify updating the kernel
> build configuration, which had only EXT3 support but not EXT4 support
> enabled, the three config options EXT3_{FS,FS_POSIX_ACL,FS_SECURITY} were
> kept, instead of immediately removing them. The three options just enable
> the corresponding EXT4 counterparts when configs from older kernel versions
> are used to build on later kernel versions. This ensures that the kernels
> from those kernel build configurations would then continue to have EXT4
> enabled for supporting booting from ext3 and ext4 file systems, to avoid
> potential unexpected surprises.
> 
> Given that the kernel build configuration has no backwards-compatibility
> guarantee and this transition phase for such build configurations has been
> in place for a decade, we can reasonably expect all such users to have
> transitioned to use the EXT4 config options in their config files at this
> point in time. With that in mind, the three EXT3 config options are
> obsolete by now.

Do we need to worry about what happens if someone uses an oldconfig
from an RHEL 7/8/9 kernel (or equivalent SuSE kernel) to try to build
the latest upstream kernel?

I don't really care because I don't use enterprise distros, and I
haven't worked for a company that supports enterprise customers for
over a decade, but I thought I should just check.

Cheers,

					- Ted