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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Konstantin Ryabitsev <konstantin@linuxfoundation.org>
Cc:     KVM list <kvm@vger.kernel.org>,
        virtualization@lists.linux-foundation.org,
        Netdev <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        mie@igel.co.jp
Subject: Re: [GIT PULL] virtio: last minute fixup
In-Reply-To: <CAHk-=wjPR+bj7P1O=MAQWXp0Mx2hHuNQ1acn6gS+mRo_kbo5Lg@mail.gmail.com>
References: <20220510082351-mutt-send-email-mst@kernel.org>
 <CAHk-=wjPR+bj7P1O=MAQWXp0Mx2hHuNQ1acn6gS+mRo_kbo5Lg@mail.gmail.com>
Date:   Wed, 11 May 2022 20:12:27 +1000
Message-ID: <87czgk8jjo.fsf@mpe.ellerman.id.au>
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Linus Torvalds <torvalds@linux-foundation.org> writes:
> On Tue, May 10, 2022 at 5:24 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>>
>> A last minute fixup of the transitional ID numbers.
>> Important to get these right - if users start to depend on the
>> wrong ones they are very hard to fix.
>
> Hmm. I've pulled this, but those numbers aren't exactly "new".
>
> They've been that way since 5.14, so what makes you think people
> haven't already started depending on them?
>
> And - once again - I want to complain about the "Link:" in that commit.
>
> It points to a completely useless patch submission. It doesn't point
> to anything useful at all.
>
> I think it's a disease that likely comes from "b4", and people decided
> that "hey, I can use the -l parameter to add that Link: field", and it
> looks better that way.

Some folks have been doing it since the early 2010s.

But I think it really took off after the Change-Id discussion a few
years back:

  https://lore.kernel.org/all/CAHk-=whFbgy4RXG11c_=S7O-248oWmwB_aZOcWzWMVh3w7=RCw@mail.gmail.com/

Which I read as you endorsing Link: tags :)

> And then they add it all the time, whether it makes any sense or not.

For me it always makes sense, because it means I can easily go from a
commit back to the original submission. That's useful for automating
various things like replies and patchwork status updates.

It allows me to find the exact patch I applied, even if what I committed
is slightly different (due to fuzz or editing), which would be harder
with a search based approach.

It gives us a way to essentially augment the change log after the fact,
by replying to the original patch with things we didn't know at the time
of commit - eg. this patch was reverted because it caused a bug, etc.

If you follow the Link: and there's nothing useful there explaining
what motivated the change then that's a bug in the patch submission, not
the Link: tag.

Really important information should be in the change log itself, but the
space below the "---" is perfect for added context that would be too
verbose for the committed change log. And anyone can reply to the
original submission to add even more useful information.

cheers