Date:   Tue, 17 May 2022 09:28:32 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Liam Howlett <liam.howlett@...cle.com>
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

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.

Guenter

---
# bad: [47c1c54d1bcd0a69a56b49473bc20f17b70e5242] Add linux-next specific files for 20220517
# good: [42226c989789d8da4af1de0c31070c96726d990c] Linux 5.18-rc7
git bisect start 'HEAD' 'v5.18-rc7'
# good: [27d9fca0814b912f762dd5adeb81d9ab250705a9] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git
git bisect good 27d9fca0814b912f762dd5adeb81d9ab250705a9
# good: [c57a4cecd8f02b365109fc326c7cde5ec6020a54] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
git bisect good c57a4cecd8f02b365109fc326c7cde5ec6020a54
# good: [0389ffdcdd4eacf5cfcef2a5e25b49a1662f8a8b] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git
git bisect good 0389ffdcdd4eacf5cfcef2a5e25b49a1662f8a8b
# good: [c506c5c327711f8bb522c10262ec3a932fe91cd2] Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux.git
git bisect good c506c5c327711f8bb522c10262ec3a932fe91cd2
# bad: [b24964a75c5c0129fd6a0d9bcb0fb6e84fbac126] mm/mmap: drop range_has_overlap() function
git bisect bad b24964a75c5c0129fd6a0d9bcb0fb6e84fbac126
# good: [3cbab4ca1ea8752912d8719d72059869b4c18045] mm/damon/sysfs: use enum for 'state' input handling
git bisect good 3cbab4ca1ea8752912d8719d72059869b4c18045
# good: [9113eaf331bf44579882c001867773cf1b3364fd] mm/memory-failure.c: add hwpoison_filter for soft offline
git bisect good 9113eaf331bf44579882c001867773cf1b3364fd
# good: [2b2adc303cebc213072520eb2e86e4beb65e9499] mm: remove rb tree.
git bisect good 2b2adc303cebc213072520eb2e86e4beb65e9499
# bad: [bbd9f664c351fbe61afa949abaaa03aed5c84af9] fs/proc/task_mmu: stop using linked list and highest_vm_end
git bisect bad bbd9f664c351fbe61afa949abaaa03aed5c84af9
# bad: [3b150cc8ab608f7a7da76b036b0ba7513628b0be] arm64: remove mmap linked list from vdso
git bisect bad 3b150cc8ab608f7a7da76b036b0ba7513628b0be
# good: [282a3e65bd1dece042bb8cf3a1666d79af1553b0] mm: use maple tree operations for find_vma_intersection()
git bisect good 282a3e65bd1dece042bb8cf3a1666d79af1553b0
# good: [d175d2cc268623e3e68181235a4aa068b50a8213] mm: convert vma_lookup() to use mtree_load()
git bisect good d175d2cc268623e3e68181235a4aa068b50a8213
# bad: [f1297d3a2cb77261c10fbbd69d92bbca700108e0] mm/mmap: reorganize munmap to use maple states
git bisect bad f1297d3a2cb77261c10fbbd69d92bbca700108e0
# good: [a897bb88e1e61df70f350a51f51cade3930adc3c] mm/mmap: move mmap_region() below do_munmap()
git bisect good a897bb88e1e61df70f350a51f51cade3930adc3c
# first bad commit: [f1297d3a2cb77261c10fbbd69d92bbca700108e0] mm/mmap: reorganize munmap to use maple states

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