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Subject: Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and
 PTE tables
To:     Will Deacon <will@kernel.org>
Cc:     linux-kernel@vger.kernel.org, elver@google.com, tglx@linutronix.de,
        paulmck@kernel.org, mingo@kernel.org, peterz@infradead.org,
        "David S. Miller" <davem@davemloft.net>, rppt@kernel.org
References: <20200511204150.27858-1-will@kernel.org>
 <20200511204150.27858-5-will@kernel.org>
 <20200517000050.GA87467@roeck-us.net> <20200517000750.GA157503@roeck-us.net>
 <20200518083715.GA31383@willie-the-truck>
From:   Guenter Roeck <linux@roeck-us.net>
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Message-ID: <418aa44b-6fb3-c3d8-a920-1a26e5edec62@roeck-us.net>
Date:   Mon, 18 May 2020 02:48:18 -0700
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On 5/18/20 1:37 AM, Will Deacon wrote:
> On Sat, May 16, 2020 at 05:07:50PM -0700, Guenter Roeck wrote:
>> On Sat, May 16, 2020 at 05:00:50PM -0700, Guenter Roeck wrote:
>>> On Mon, May 11, 2020 at 09:41:36PM +0100, Will Deacon wrote:
>>>> Now that the page table allocator can free page table allocations
>>>> smaller than PAGE_SIZE, reduce the size of the PMD and PTE allocations
>>>> to avoid needlessly wasting memory.
>>>>
>>>> Cc: "David S. Miller" <davem@davemloft.net>
>>>> Cc: Peter Zijlstra <peterz@infradead.org>
>>>> Signed-off-by: Will Deacon <will@kernel.org>
>>>
>>> Something in the sparc32 patches in linux-next causes all my sparc32 emulations
>>> to crash. bisect points to this patch, but reverting it doesn't help, and neither
>>> does reverting the rest of the series.
>>>
>> Actually, turns out I see the same pattern (lots of scheduling while atomic
>> followed by 'killing interrupt handler' in cryptomgr_test) with several
>> powerpc boot tests.  I am currently bisecting those crashes. I'll report
>> the results here as well as soon as I have it.
> 
> FWIW, I retested my sparc32 patches with PREEMPT=y and I don't see any
> issues. However, linux-next is a different story, where I don't get very far
> at all:
> 
> BUG: Bad page state in process swapper  pfn:005b4
> 
> If you're seeing this on powerpc too, I wonder if it's related to:
> 
> https://lore.kernel.org/r/20200514170327.31389-1-rppt@kernel.org
> 
> since I think it just hit -next and the diffstat is all over the place. I've
> added Mike to CC just in case.
> 

Here are the bisect results for ppc:

# bad: [bdecf38f228bcca73b31ada98b5b7ba1215eb9c9] Add linux-next specific files for 20200515
# good: [2ef96a5bb12be62ef75b5828c0aab838ebb29cb8] Linux 5.7-rc5
git bisect start 'HEAD' 'v5.7-rc5'
# good: [3674d7aa7a8e61d993886c2fb7c896c5ef85e988] Merge remote-tracking branch 'crypto/master'
git bisect good 3674d7aa7a8e61d993886c2fb7c896c5ef85e988
# good: [87f6f21783522e6d62127cf33ae5e95f50874beb] Merge remote-tracking branch 'spi/for-next'
git bisect good 87f6f21783522e6d62127cf33ae5e95f50874beb
# good: [5c428e8277d5d97c85126387d4e00aa5adde4400] Merge remote-tracking branch 'staging/staging-next'
git bisect good 5c428e8277d5d97c85126387d4e00aa5adde4400
# good: [f68de67ed934e7bdef4799fd7777c86f33f14982] Merge remote-tracking branch 'hyperv/hyperv-next'
git bisect good f68de67ed934e7bdef4799fd7777c86f33f14982
# bad: [54acd2dc52b069da59639eea0d0c92726f32fb01] mm/memblock: fix a typo in comment "implict"->"implicit"
git bisect bad 54acd2dc52b069da59639eea0d0c92726f32fb01
# good: [784a17aa58a529b84f7cc50f351ed4acf3bd11f3] mm: remove the pgprot argument to __vmalloc
git bisect good 784a17aa58a529b84f7cc50f351ed4acf3bd11f3
# good: [6cd8137ff37e9a37aee2d2a8889c8beb8eab192f] khugepaged: replace the usage of system(3) in the test
git bisect good 6cd8137ff37e9a37aee2d2a8889c8beb8eab192f
# bad: [6987da379826ed01b8a1cf046b67cc8cc10117cc] sparc: remove unnecessary includes
git bisect bad 6987da379826ed01b8a1cf046b67cc8cc10117cc
# good: [bc17b545388f64c09e83e367898e28f60277c584] mm/hugetlb: define a generic fallback for is_hugepage_only_range()
git bisect good bc17b545388f64c09e83e367898e28f60277c584
# good: [9b5aa5b43f957f03a1f4a9aff5f7924e2ebbc011] arch-kmap_atomic-consolidate-duplicate-code-checkpatch-fixes
git bisect good 9b5aa5b43f957f03a1f4a9aff5f7924e2ebbc011
# bad: [89194ba5ee31567eeee9c81101b334c8e3248198] arch/kmap: define kmap_atomic_prot() for all arch's
git bisect bad 89194ba5ee31567eeee9c81101b334c8e3248198
# good: [022785d2bea99f8bc2a37b7b6c525eea26f6ac59] arch-kunmap_atomic-consolidate-duplicate-code-checkpatch-fixes
git bisect good 022785d2bea99f8bc2a37b7b6c525eea26f6ac59
# good: [a13c2f39e3f0519ddee57d26cc66ec70e3546106] arch/kmap: don't hard code kmap_prot values
git bisect good a13c2f39e3f0519ddee57d26cc66ec70e3546106
# first bad commit: [89194ba5ee31567eeee9c81101b334c8e3248198] arch/kmap: define kmap_atomic_prot() for all arch's

I don't know if that is accurate either. Maybe things are so broken
that bisect gets confused, or the problem is due to interaction
between different patch series.

Guenter