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Date:   Mon, 4 Apr 2022 10:55:35 +0200
From:   Jan Kara <jack@suse.cz>
To:     Pavel Machek <pavel@ucw.cz>
Cc:     Jan Kara <jack@suse.cz>, Matthew Wilcox <willy@infradead.org>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        reiserfs-devel@vger.kernel.org
Subject: Re: Is it time to remove reiserfs?
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 <20220402105454.GA16346@amd>
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Hello!

On Sat 02-04-22 12:54:55, Pavel Machek wrote:
> > > Keeping reiserfs in the tree has certain costs.  For example, I would
> > > very much like to remove the 'flags' argument to ->write_begin.  We have
> > > the infrastructure in place to handle AOP_FLAG_NOFS differently, but
> > > AOP_FLAG_CONT_EXPAND is still around, used only by reiserfs.
> > > 
> > > Looking over the patches to reiserfs over the past couple of years, there
> > > are fixes for a few syzbot reports and treewide changes.  There don't
> > > seem to be any fixes for user-spotted bugs since 2019.  Does reiserfs
> > > still have a large install base that is just very happy with an old
> > > stable filesystem?  Or have all its users migrated to new and exciting
> > > filesystems with active feature development?
> > > 
> > > We've removed support for senescent filesystems before (ext, xiafs), so
> > > it's not unprecedented.  But while I have a clear idea of the benefits to
> > > other developers of removing reiserfs, I don't have enough information to
> > > weigh the costs to users.  Maybe they're happy with having 5.15 support
> > > for their reiserfs filesystems and can migrate to another filesystem
> > > before they upgrade their kernel after 5.15.
> > > 
> > > Another possibility beyond outright removal would be to trim the kernel
> > > code down to read-only support for reiserfs.  Most of the quirks of
> > > reiserfs have to do with write support, so this could be a useful way
> > > forward.  Again, I don't have a clear picture of how people actually
> > > use reiserfs, so I don't know whether it is useful or not.
> > > 
> > > NB: Please don't discuss the personalities involved.  This is purely a
> > > "we have old code using old APIs" discussion.
> > 
> > So from my distro experience installed userbase of reiserfs is pretty small
> > and shrinking. We still do build reiserfs in openSUSE / SLES kernels but
> > for enterprise offerings it is unsupported (for like 3-4 years) and the module
> > is not in the default kernel rpm anymore.
> 
> I believe I've seen reiserfs in recent Arch Linux ARM installation on
> PinePhone. I don't really think you can remove a feature people are
> using.

Well, if someone uses Reiserfs they better either migrate to some other
filesystem or start maintaining it. It is as simple as that because
currently there's nobody willing to invest resources in it for quite a few
years and so it is just a question of time before it starts eating people's
data (probably it already does in some cornercases, as an example there are
quite some syzbot reports for it)...

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR