linux-kernel - Re: [PATCH] relay: Remove unused relay_late_setup

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Message-ID: <aCFPRhfxKUeRu1Qh@gallifrey>
Date: Mon, 12 May 2025 01:30:46 +0000
From: "Dr. David Alan Gilbert" <linux@...blig.org>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	andriy.shevchenko@...ux.intel.com, corbet@....net,
	linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	viro@...iv.linux.org.uk, Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH] relay: Remove unused relay_late_setup_files

* Jason Xing (kerneljasonxing@...il.com) wrote:
> Hi All,

Hi Jason,

> I noticed this patch "relay: Remove unused relay_late_setup_files"
> appears in the mm branch already[1], which I totally missed. Sorry for
> joining the party late.
> 
> I have a different opinion on this. For me, I'm very cautious about
> what those so-called legacy interfaces are and how they can work in
> different cases and what the use case might be... There are still a
> small number of out-of-tree users like me heavily relying on relayfs
> mechanism. So my humble opinion is that if you want to remove
> so-called dead code, probably clearly state why it cannot be used
> anymore in the future.

We've got lots of deadcode, why it's dead varies a lot; for example
people forgetting to clean it up after other patches etc - so this
_could_ be used but hasn't been for well over 7 years.

> Dr. David, I appreciate your patch, but please do not simply do the
> random cleanup work __here__. If you take a deep look at the relayfs,
> you may find there are other interfaces/functions no one uses in the
> kernel tree.

Actually, that was the only interface in relay that I found unused.

> I'm now checking this kind of patch in relayfs one by one to avoid
> such a thing happening. I'm trying to maintain it as much as possible
> since we internally use it in the networking area to output useful
> information in the hot paths, a little bit like blktrace. BTW, relayfs
> is really a wonderful one that helps kernel modules communicate with
> userspace very efficiently. I'm trying to revive it if I can.

If you've got a use for that function, then I'm more than happy to suggest
just dropping my patch.

However, it is a fairly chunky function that is built into distro
kernels - so I think it should have a little thought put to it.

As I say, if you are using it, it's fine by me just to drop this patch.

Dave

> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?h=mm-everything&id=46aa76118ee365c25911806e34d28fc2aa5ef997
> 
> Thanks,
> Jason
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\        dave @ treblig.org |                               | In Hex /
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