Message-ID: <Y/0U8tpNkgePu00M@sashalap>
Date:   Mon, 27 Feb 2023 15:39:14 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org
Subject: Re: AUTOSEL process

On Mon, Feb 27, 2023 at 10:06:32AM -0800, Eric Biggers wrote:
>On Mon, Feb 27, 2023 at 09:47:48AM -0800, Eric Biggers wrote:
>> > > > Of course, it's not just me that AUTOSEL isn't working for.  So, you'll still
>> > > > continue backporting random commits that I have to spend hours bisecting, e.g.
>> > > > https://lore.kernel.org/stable/20220921155332.234913-7-sashal@kernel.org.
>> > > >
>> > > > But at least I won't have to deal with this garbage for my own commits.
>> > > >
>> > > > Now, I'm not sure I'll get a response to this --- I received no response to my
>> > > > last AUTOSEL question at
>> > > > https://lore.kernel.org/stable/Y1DTFiP12ws04eOM@sol.localdomain.  So to
>> > > > hopefully entice you to actually do something, I'm also letting you know that I
>> > > > won't be reviewing any AUTOSEL mails for my commits anymore.
>> > > >
>> > >
>> > > The really annoying thing is that someone even replied to your AUTOSEL email for
>> > > that broken patch and told you it is broken
>> > > (https://lore.kernel.org/stable/d91aaff1-470f-cfdf-41cf-031eea9d6aca@mailbox.org),
>> > > and ***you ignored it and applied the patch anyway***.
>> > >
>> > > Why are you even sending these emails if you are ignoring feedback anyway?
>> >
>> > I obviously didn't ignore it on purpose, right?
>> >
>>
>> I don't know, is it obvious?  You've said in the past that sometimes you'd like
>> to backport a commit even if the maintainer objects and/or it is known buggy.
>> https://lore.kernel.org/stable/d91aaff1-470f-cfdf-41cf-031eea9d6aca@mailbox.org
>> also didn't explicitly say "Don't backport this" but instead "This patch has
>> issues", so maybe that made a difference?

 From what I gather I missed the reply - I would not blindly ignore a
maintainer.

>> Anyway, the fact is that it happened.  And if it happened in the one bug that I
>> happened to look at because it personally affected me and I spent hours
>> bisecting, it probably is happening in lots of other cases too.  So it seems the
>> process is not working...

This one is tricky, becuase we also end up taking a lot of commits that
do fix real bugs, and were never tagged for stable or even had a fixes
tag.

Maybe I should run the numbers again, but when we compared regression
rates of stable tagged releases and AUTOSEL ones, it was fairly
identical.

>> Separately from responses to the AUTOSEL email, it also seems that you aren't
>> checking for any reported regressions or pending fixes for a commit before
>> backporting it.  Simply searching lore for the commit title
>> https://lore.kernel.org/all/?q=%22drm%2Famdgpu%3A+use+dirty+framebuffer+helper%22
>> would have turned up the bug report
>> https://lore.kernel.org/dri-devel/20220918120926.10322-1-user@am64/ that
>> bisected a regression to that commit, as well as a patch that Fixes that commit:
>> https://lore.kernel.org/all/20220920130832.2214101-1-alexander.deucher@amd.com/
>> Both of these existed before you even sent the AUTOSEL email!

I would love to have a way to automatically grep lore for reported
issues that are pinpointed to a given commit. I'm hoping that Thorsten's
regression tracker could be used that way soon enough.

>> So to summarize, that buggy commit was backported even though:
>>
>>   * There were no indications that it was a bug fix (and thus potentially
>>     suitable for stable) in the first place.
>>   * On the AUTOSEL thread, someone told you the commit is broken.
>>   * There was already a thread that reported a regression caused by the commit.
>>     Easily findable via lore search.
>>   * There was also already a pending patch that Fixes the commit.  Again easily
>>     findable via lore search.
>>
>> So it seems a *lot* of things went wrong, no?  Why?  If so many things can go
>> wrong, it's not just a "mistake" but rather the process is the problem...
>
>BTW, another cause of this is that the commit (66f99628eb24) was AUTOSEL'd after
>only being in mainline for 4 days, and *released* in all LTS kernels after only
>being in mainline for 12 days.  Surely that's a timeline befitting a critical
>security vulnerability, not some random neural-network-selected commit that
>wasn't even fixing anything?

I would love to have a mechanism that tells me with 100% confidence if a
given commit fixes a bug or not, could you provide me with one?

w.r.t timelines, this is something that was discussed on the mailing
list a few years ago where we decided that giving AUTOSEL commits 7 days
of soaking time is sufficient, if anything changed we can have this
discussion again.

Note, however, that it's not enough to keep pointing at a tiny set and
using it to suggest that the entire process is broken. How many AUTOSEL
commits introduced a regression? How many -stable tagged ones did? How
many bugs did AUTOSEL commits fix?

-- 
Thanks,
Sasha

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