Re: [added to the 4.1 stable tree] xfs: Don't wrap growfs AGFL indexes

[Dave Chinner <david@fromorbit.com>]

On Fri, Jun 03, 2016 at 07:10:26PM -0400, Sasha Levin wrote:
> On 06/03/2016 07:05 PM, Dave Chinner wrote:
> > On Fri, Jun 03, 2016 at 05:35:03PM -0400, Sasha Levin wrote:
> >> > From: Dave Chinner <dchinner@redhat.com>
> >> > 
> >> > This patch has been added to the 4.1 stable tree. If you have any
> >> > objections, please let us know.
> > This should not go to the 4.1 tree. Check the stable notification
> > information, please:
> > 
> >> > ===============
> >> > 
> >> > [ Upstream commit ad747e3b299671e1a53db74963cc6c5f6cdb9f6d ]
> > ....
> >> > cc: <stable@vger.kernel.org> # 4.4-4.5
> > It says 4.4 and 4.5 only.
> 
> That's correct, but the commit that this patch fixes was:
> 
> commit 96f859d52bcb1c6ea6f3388d39862bf7143e2f30
> Author: Darrick J. Wong <darrick.wong@oracle.com>
> Date:   Mon Jan 4 16:13:21 2016 +1100
> 
>     libxfs: pack the agfl header structure so XFS_AGFL_SIZE is correct
....
> 
>     cc: <stable@vger.kernel.org> # 3.10 - 4.4
>     Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
>     Reviewed-by: Dave Chinner <dchinner@redhat.com>
>     Signed-off-by: Dave Chinner <david@fromorbit.com>
> 
> Which, as you see, was marked for and backported to -stable versions
> prior to 4.4, which is why I've preferred to queue this commit even though
> it's not supposed to go in and see if anyone objects.

Ugh, which means that you're going to have another major tranche of
fixes to backport once I fix the problem properly and handle the
problems automatically. The stable patxh for 4.4-4.5 was really just
meant as a stop-gap measure (i.e.  prevent the reported vector)
while we fixed the problem once and for all. That means you're
looking at a another set of patches in the hundreds of lines needing
to be backported to the stable kernels.

I get rather concerned about the stable kernel process when this
starts happening - no-one I know of on the XFS side does any testing
on *any* of the stable kernel releases, and now we're in the
dangerous territory of layered on-disk format fixes being backported
by developers without any specific XFS expertise and there's no
real safety net....

Maybe I'm being overly paranoid, but this *scares me*. The chance of
something going wrong and lots of users having problems is much
higher than I'm comfortable with.... 

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com