linux-kernel - Re: [PATCH] mapletree-vs-khugepaged

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Date:   Tue, 17 May 2022 15:03:28 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     Heiko Carstens <hca@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mapletree-vs-khugepaged

* Guenter Roeck <linux@...ck-us.net> [220517 09:23]:
> On 5/17/22 04:53, Heiko Carstens wrote:
> > On Fri, May 13, 2022 at 05:00:31PM +0000, Liam Howlett wrote:
> > > * Sven Schnelle <svens@...ux.ibm.com> [220513 10:46]:
> > > > Heiko Carstens <hca@...ux.ibm.com> writes:
> > > > > FWIW, same on s390 - linux-next is completely broken. Note: I didn't
> > > > > bisect, but given that the call trace, and even the failing address
> > > > > match, I'm quite confident it is the same reason.
> > > > IS that issue supposed to be fixed? git bisect pointed me to
> > > > 
> > > > # bad: [76535d42eb53485775a8c54ea85725812b75543f] Merge branch
> > > >    'mm-everything' of
> > > >    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> > > > 
> > > > which isn't really helpful.
> > > > 
> > > > Anything we could help with debugging this?
> > > 
> > > I tested the maple tree on top of the s390 as it was the same crash and
> > > it was okay.  I haven't tested the mm-everything branch though.  Can you
> > > test mm-unstable?
> > > 
> > > I'll continue setting up a sparc VM for testing here and test
> > > mm-everything on that and the s390
> > 
> > So due to reports here I did some sort of "special bisect": with today's
> > linux-next I did a hard reset to commit 562340595cbb ("Merge branch
> > 'for-next/kspp' of
> > git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git"),
> > started a bisect on Andrew's tree between mm-stable and mm-unstable, and
> > merged whatever commit was about to be bisected into 562340595cbb.
> > 
> > This lead finally to commit f1297d3a2cb7 ("mm/mmap: reorganize munmap to
> > use maple states") as "first bad commit".
> > 
> > So given that we are shortly before the merge window and linux-next is
> > completely broken for s390, how do we proceed? Right now I have no idea if
> > there is anything else in linux-next that would break s390 because of this.
> > 
> > Even though I'm sure you won't like to hear this, but I'd appreciate if
> > this code could be removed from linux-next again.
> 
> I finally found some time to bisect the alpha boot failures in -next.
> Bisect results below.
> 
> Guenter
> 
> ---
...
> # first bad commit: [f1297d3a2cb77261c10fbbd69d92bbca700108e0] mm/mmap: reorganize munmap to use maple states

Thanks for all the work on this.

I was able to reproduce on a sparc64 VM.  I was returning node metadata
in a rare case.  I just CC'ed you all on a patch [1].  It should apply
cleanly to whatever branch you want since it only changes
lib/maple_tree.c

1. https://lore.kernel.org/linux-mm/20220517145913.3480729-1-Liam.Howlett@oracle.com/

Thanks,
Liam