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Date:   Tue, 17 May 2022 13:53:22 +0200
From:   Heiko Carstens <hca@linux.ibm.com>
To:     Liam Howlett <liam.howlett@oracle.com>
Cc:     Sven Schnelle <svens@linux.ibm.com>,
        Guenter Roeck <linux@roeck-us.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mapletree-vs-khugepaged
Message-ID: <YoOMsmq24FWsWWyr@osiris>
References: <20220428172040.GA3623323@roeck-us.net>
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 <20220513165955.mkg5wvfi4dwpzoer@revolver>
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On Fri, May 13, 2022 at 05:00:31PM +0000, Liam Howlett wrote:
> * Sven Schnelle <svens@linux.ibm.com> [220513 10:46]:
> > Heiko Carstens <hca@linux.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.