Re: Proposal: Enhancing Commit Tagging for Stable Kernel Branches

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Sun, 2024-07-14 at 17:35 +0200, Andrew Lunn wrote:
> > One of the big reasons patches get Fixes without cc:stable is
> > simply that it's an -rc fix for a merge window regression (so no
> > released kernel has it in and therefore no stable kernel needs it),
> > so you'd also need to explain that case in the improve docs
> > (because it's a genuine fix, just not a stable candidate).
> 
> There is also the case where a patch which needs fixing has been
> queued into a -next tree by the Maintainer. So it is not even in an
> -rc yet, it is waiting or the next merge window to open.
> 
> So what we seem to be talking about is a Fixes: tag pointing to a
> patch in a released kernel, which does not have a stable: tag.
> 
> Why not simply get 0-day to enforce such patches must have a
> not-stable: tag? Such emails should quickly train developers to do
> the right thing.

Because the not-stable tag seems yet another really hard to use thing.
When Maintainers look at patches, about the first question is where did
this come from (Fixes answers that and we're having good success
tagging most things with it because it's obvious how to apply it---and
not derailing this is another good reason not to split the tag).  The
next question is should this be backported.  This is a bit more
subjective because it's a combination of would anyone actually see any
effects from this or is it a serious enough problem in general that it
might lead to some exploit or bug.  However, this is the judgment call
that can often prove wrong with hindsight, so we have the send
separately to stable channel if this turns out to be the case.  The
not-stable tag seems to be a pejorative statement that only an idiot
would backport this so don't.  I can't see myself tagging any Fixes
tagged commit with that because it's a judgment call as likely to be
wrong as the initial cc:stable decision, so it seems more aimed at
enhancement patches that wouldn't have a Fixes tag anyway and therefore
shouldn't be backported.


I think the actual problem the not-stable tag is meant to solve is some
commits that aren't fixes tagged actually end up in stable when they
shouldn't be there; their presence causes bugs and whoever the
maintainer is gets annoyed that it got backported.

James