Re: [PATCH] mapletree-vs-khugepaged

From: Heiko Carstens <hca@linux.ibm.com>
To: Heiko Carstens <hca@linux.ibm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>,
	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
Date: Tue, 17 May 2022 14:26:14 +0200	[thread overview]
Message-ID: <YoOUZnmsCkq5JkCl@osiris> (raw)
In-Reply-To: <YoOMsmq24FWsWWyr@osiris>

On Tue, May 17, 2022 at 01:53:22PM +0200, Heiko Carstens wrote:
> 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"),

Forgot to mention: this is the last merge commit before the akpm
trees were merged, which again come last in linux-next.

> 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.