Re: Proposal: Enhancing Commit Tagging for Stable Kernel Branches

[Dan Carpenter <dan.carpenter@linaro.org>]

On Tue, Jul 16, 2024 at 02:20:42PM +0200, Takashi Iwai wrote:
> > > > The one question I have is for patches which pre-date git.  I was told
> > > > to leave the Fixes tag off in that case, but I think that's out of date.
> > > > It's more useful to say "Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")".
> > > 
> > > If a thing was there since before git and only now is being discovered
> > > it either needs to be explicitly marked for stable with cc: or we can
> > > just keep the fix in newer kernels. IMO this particular "Fixes" tag does
> > > not bring any value.
> > 
> > On the contrary, if I see just a "cc: stable" and no "Fixes:" tag, I do
> > a "best effort" to backport to all current stable/lts trees.  If it
> > fails on 5.15 and older, great, I don't warn anyone about that as there
> > was no Fixes: tag for me to know how far back it should go.
> 
> That's what I expected for the cases I put only Cc-to-stable; they
> have been mostly some trivial quirks only for new devices, and the
> stuff that can be taken safely when applicable -- otherwise just
> skip.
> 

That's the same thing that happens if you add the Fixes: 1da177e4c3f4
("Linux-2.6.12-rc2") tag.  Greg and Sasha aren't manually backporting
patches unless they seem security related.  When a patch doesn't
backport cleanly, the stable maintainers rely on other people to backport
patches they care about.

Eventually, if patches don't apply then they're manually reviewed.  I
find it really frustrating to review stable patches without a Fixes tag.
When I see it I think that probably I wouldn't have had to manually
review the failed patch at all if they had used a Fixes tag.  (I just
naturally start assuming the worst about people after I've spent five
hours backporting patches.  I'm not going to investigate it either
because it's not security related.  I'm just going to assume the worse,
say some curse words, and move on.)

Of course, for security related stuff the Fixes tag is absolutely
essential.  For example, this patch does not backport cleanly to 4.14
kernels.
https://lore.kernel.org/all/20240501125448.896529-1-edumazet@google.com/
It's really nice that Eric Dumazet added a Fixes: 1da177e4c3f4
("Linux-2.6.12-rc2").

As a upstream reviewer, I think the Fixes tag is important as well.  I
don't think I've ever used the Fixes 1da177e4c3f4 ("Linux-2.6.12-rc2")
tag because I know it annoys people but I write that "This bug has been
there since before git" because the information is useful.

regards,
dan carpenter