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

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Message-ID: <20220517203820.6hqasgwn27go6ltv@revolver>
Date:   Tue, 17 May 2022 20:38:27 +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 12:28]:
> On 5/17/22 08:03, Liam Howlett wrote:
> > * 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
> > 
> 
> FWIW, below is my bisect log for the sparc64 problem. It looks like your patch
> does fix this problem.
> 

Thanks, yes.  I actually tested on my sparc64 VM since I still cannot
get the s390 to crash.