[PATCH v8 23/70] mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap()

[Liam Howlett]

* Heiko Carstens <hca at linux.ibm.com> [220502 06:18]:
> On Sun, May 01, 2022 at 05:24:12PM -0700, Andrew Morton wrote:
> > (cc S390 maintainers)
> > (cc stable & Greg)
> > 
> > > I have been porting my patches over and hit a bit of a snag. It looked
> > > like my patches were not booting on the s390 - but not all the time. So
> > > I reverted back to mm-stable (059342d1dd4e) and found that also failed
> > > to boot sometimes on my qemu setup.  When it fails it's ~4-5sec into
> > > booting.  The last thing I see is:
> > > 
> > > "[    4.668916] Spectre V2 mitigation: execute trampolines"
> > > 
> > > I've bisected back to commit e553f62f10d9 (mm, page_alloc: fix
> > > build_zonerefs_node())
> > > 
> > > With the this commit, I am unable to boot one out of three times.  When
> > > using the previous commit I was not able to get it to hang after trying
> > > 10+ times.  This is a qemu s390 install with KASAN on and I see no error
> > > messages.  I think it's likely it is this patch, but no guaranteed.
> > > 
> > 
> > Great, thanks.  So mapletree is absolved.
> > 
> > Unfortunately 059342d1dd4e was cc:stable.  Greg, you might want to pull
> > the plug on that one if it isn't too late.
> > 
> > I'll await input from the S390 team, but from my reading the issues
> > which that patch addresses aren't terribly serious, so perhaps the
> > thing to do is to revert 059342d1dd4e (with a cc:stable) while
> > 059342d1dd4e gets a redo?
> 
> I cannot confirm that Linus' tree currently has problems on s390 with
> commit e553f62f10d9 ("mm, page_alloc: fix build_zonerefs_node()").
> 
> This commit was applied by Linus on 15th of April, and our CI didn't
> report any problems since then. At least nothing that would point to
> this commit. Also I just gave e553f62f10d9 a try (defconfig + KASAN):
> no problems to report.
> 
> Same with 059342d1dd4e (mm-stable): it just works for me.
> 
> Liam, could you share your kernel config?

Sure thing.  See attached.

Thanks,
Liam

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