Message-ID: <CAL+tcoAgNyOb0vRzJBvzoSH2NrxZyWBWfnOV0D5KJL8jBJ=vAw@mail.gmail.com>
Date: Mon, 12 May 2025 15:34:58 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, corbet@....net, linux-doc@...r.kernel.org, 
	LKML <linux-kernel@...r.kernel.org>, linux@...blig.org, viro@...iv.linux.org.uk, 
	Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH] relay: Remove unused relay_late_setup_files

On Mon, May 12, 2025 at 3:22 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Mon, May 12, 2025 at 02:53:56PM +0800, Jason Xing wrote:
> > On Mon, May 12, 2025 at 2:15 PM Andy Shevchenko
> > <andriy.shevchenko@...ux.intel.com> wrote:
> > > On Mon, May 12, 2025 at 09:12:56AM +0800, Jason Xing wrote:
> > > >
> > > > 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.
> > > >
> > > > 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.
> > > >
> > > > 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.
> > >
> > > Jason, with all of the respect, if you are interested in keeping things going
> > > on, please add yourself to the MAINTAINERS. It will makes the users of the
> > > legacy code, Andrew and others, who are doing maintainer's/reviewer's job,
> > > and you happy.
> >
> > I didn't subscribe to LKML because they're too many emails everyday.
> > Because of this, I missed most of changes in relayfs.
>
> And how is this relevant to my proposal?

Well, I was just murmuring.

>
> Moreover with `lei` you can filter out from time to time the lore archive for
> these, no need to be subscribed and read LKML in full.

Oh, thanks for the guidance.

>
> > Sure, I'm happy to do so, but I'm not sure how/what the detailed
> > process is here. I would like to ask the core maintainers/developers
> > in advance.
> >
> > Any thoughts on this? Andrew, Jens.
>
> Just send a patch to the LKML which adds a relevant record into MAINTAINERS.
> I believe all stakeholders here will be happy to accept that kind of change.
>
> At least you can get my Ack, FWIW (I am not a stakeholder here).

Got it. I think I'm going add like this with you acked-by tag:
diff --git a/MAINTAINERS b/MAINTAINERS
index 890699d937b6..208c46416760 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -20481,6 +20481,15 @@ L:     linux-wireless@...r.kernel.org
 S:     Orphan
 F:     drivers/net/wireless/rsi/

+RELAY SUBSYSTEM
+M:     Andrew Morton <akpm@...ux-foundation.org>
+M:     Jens Axboe <axboe@...nel.dk>
+M:     Jason Xing <kernelxing@...cent.com>
+S:      Maintained
+F:     Documentation/filesystems/relay.rst
+F:     include/linux/relay.h
+F:     kernel/relay.c
+
 REGISTER MAP ABSTRACTION
 M:     Mark Brown <broonie@...nel.org>
 L:     linux-kernel@...r.kernel.org

It would be good if Andrew and Jens approve this first.

>
> > > Also note, we usually do not care about the out-of-tree users. The main Q here
> > > why are they out-of-tree for so long time?
> >
> > It's due to the history problem. Back then, developers were trying to
> > develop various file systems to add more debuginfo. As you may notice,
> > blktrace is the one which manifests the answer.
>
> Then provide a roadmap on the upstreaming the necessary parts. Otherwise
> there is no room for a dead code in the Linux kernel. This is the rule:
> we do not add one, and we do not leave it dangling after removing the last
> user.

Got it. Will do that. Thanks for the reminder.

Thanks,
Jason


>
> > > > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?h=mm-everything&id=46aa76118ee365c25911806e34d28fc2aa5ef997
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

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