Re: [PATCH stable 6.1] devlink: Fix RCU stall when unregistering a devlink instance

[Ido Schimmel <idosch@nvidia.com>]

On Tue, Oct 01, 2024 at 03:39:53PM -0700, Jakub Kicinski wrote:
> On Tue, 1 Oct 2024 16:38:39 +0300 Ido Schimmel wrote:
> > > You need to document the heck out of why this is only relevant for this
> > > one specific kernel branch IN the changelog text, so that we understand
> > > what is going on, AND you need to get acks from the relevant maintainers
> > > of this area of the kernel to accept something that is not in Linus's
> > > tree.
> > > 
> > > But first of, why?  Why not just take the upstrema commits instead?  
> > 
> > There were a lot of changes as part of the 6.3 cycle to completely
> > rework the semantics of the devlink instance reference count. As part of
> > these changes, commit d77278196441 ("devlink: bump the instance index
> > directly when iterating") inadvertently fixed the bug mentioned in this
> > patch. This commit cannot be applied to 6.1.y as-is because a prior
> > commit (also in 6.3) moved the code to a different file (leftover.c ->
> > core.c). There might be more dependencies that I'm currently unaware of.
> > 
> > The alternative, proposed in this patch, is to provide a minimal and
> > contained fix for the bug introduced in upstream commit c2368b19807a
> > ("net: devlink: introduce "unregistering" mark and use it during
> > devlinks iteration") as part of the 6.0 cycle.
> > 
> > The above explains why the patch is only relevant to 6.1.y.
> > 
> > Jakub / Jiri, what is your preference here? This patch or cherry picking
> > a lot of code from 6.3?
> 
> No preference here. The fix as posted looks correct. The backport of
> the upstream commit should be correct too (I don't see any
> incompatibilities) but as you said the code has moved and got exposed
> via a header, so the diff will look quite different.
> 
> I think Greg would still prefer to use the bastardized upstream commit
> in such cases.

Greg, if I augment the commit message with the necessary information,
would you be willing to take this patch instead of a much larger patch?