linux-ext4 - Re: [PATCH 0/7] ext4 fast-commit fixes

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Message-ID: <Y4+ua2XftbAYd8xq@mit.edu>
Date:   Tue, 6 Dec 2022 16:04:43 -0500
From:   "Theodore Ts'o" <tytso@....edu>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-ext4@...r.kernel.org, linux-fscrypt@...r.kernel.org,
        Harshad Shirwadkar <harshadshirwadkar@...il.com>
Subject: Re: [PATCH 0/7] ext4 fast-commit fixes

On Sun, Nov 06, 2022 at 02:48:34PM -0800, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...nel.org
> 
> This series fixes several bugs in the fast-commit feature.
> 
> Patch 6 may be the most controversial patch of this series, since it
> would make old kernels unable to replay fast-commit journals created by
> new kernels.  I'd appreciate any thoughts on whether that's okay.  I can
> drop that patch if needed.

Mumble.  Normally, it's something we would avoid, since there aren't
that many users using fast commit, since it's not enabled by default.
And given that the off-by-one errors are bugs, an it's a question of
old kernels requiring a pretty buggy layout, the question is whether
it's worth it to do an explicit version / feature flag and support
both for some period of time.

I'm inclined to say no, and just let things slide, and instead make
sure that e2fsck can handle both the old and the new format, and let
that handle the fast commit replay if necessary.

Harshad, what do you think?

						- Ted