Re: arm32: panic in move_freepages (Was [PATCH v2 0/4] arm64: drop pfn_valid_within() and simplify pfn_valid())

From: Kefeng Wang <wangkefeng.wang@huawei.com>
To: Mike Rapoport <rppt@kernel.org>
Cc: David Hildenbrand <david@redhat.com>,
	<linux-arm-kernel@lists.infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Anshuman Khandual <anshuman.khandual@arm.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	"Mike Rapoport" <rppt@linux.ibm.com>,
	Will Deacon <will@kernel.org>, <kvmarm@lists.cs.columbia.edu>,
	<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: arm32: panic in move_freepages (Was [PATCH v2 0/4] arm64: drop pfn_valid_within() and simplify pfn_valid())
Date: Wed, 12 May 2021 11:08:14 +0800	[thread overview]
Message-ID: <c3006cd0-fff6-ab45-da83-a216d40388f2@huawei.com> (raw)
In-Reply-To: <YJpEwF2cGjS5mKma@kernel.org>

On 2021/5/11 16:48, Mike Rapoport wrote:
> On Mon, May 10, 2021 at 11:10:20AM +0800, Kefeng Wang wrote:
>>
>>>> The memory is not continuous, see MEMBLOCK:
>>>>    memory size = 0x4c0fffff reserved size = 0x027ef058
>>>>    memory.cnt  = 0xa
>>>>    memory[0x0]    [0x80a00000-0x855fffff], 0x04c00000 bytes flags: 0x0
>>>>    memory[0x1]    [0x86a00000-0x87dfffff], 0x01400000 bytes flags: 0x0
>>>>    memory[0x2]    [0x8bd00000-0x8c4fffff], 0x00800000 bytes flags: 0x0
>>>>    memory[0x3]    [0x8e300000-0x8ecfffff], 0x00a00000 bytes flags: 0x0
>>>>    memory[0x4]    [0x90d00000-0xbfffffff], 0x2f300000 bytes flags: 0x0
>>>>    memory[0x5]    [0xcc000000-0xdc9fffff], 0x10a00000 bytes flags: 0x0
>>>>    memory[0x6]    [0xde700000-0xde9fffff], 0x00300000 bytes flags: 0x0
>>>> ...
>>>>
>>>> The pfn_range [0xde600,0xde700] => addr_range [0xde600000,0xde700000]
>>>> is not available memory, and we won't create memmap , so with or without
>>>> your patch, we can't see the range in free_memmap(), right?
>>>
>>> This is not available memory and we won't see the reange in free_memmap(),
>>> but we still should create memmap for it and that's what my patch tried to
>>> do.
>>>
>>> There are a lot of places in core mm that operate on pageblocks and
>>> free_unused_memmap() should make sure that any pageblock has a valid memory
>>> map.
>>>
>>> Currently, that's not the case when SPARSEMEM=y and my patch tried to fix
>>> it.
>>>
>>> Can you please send log with my patch applied and with the printing of
>>> ranges that are freed in free_unused_memmap() you've used in previous
>>> mails?
> 
>> with your patch[1] and debug print in free_memmap,
>> ----> free_memmap, start_pfn = 85800,  85800000 end_pfn = 86800, 86800000
>> ----> free_memmap, start_pfn = 8c800,  8c800000 end_pfn = 8e000, 8e000000
>> ----> free_memmap, start_pfn = 8f000,  8f000000 end_pfn = 90000, 90000000
>> ----> free_memmap, start_pfn = dcc00,  dcc00000 end_pfn = de400, de400000
>> ----> free_memmap, start_pfn = dec00,  dec00000 end_pfn = e0000, e0000000
>> ----> free_memmap, start_pfn = e0c00,  e0c00000 end_pfn = e4000, e4000000
>> ----> free_memmap, start_pfn = f7000,  f7000000 end_pfn = f8000, f8000000
> 
> It seems that freeing of the memory map is suboptimal still because that
> code was not designed for memory layout that has more holes than Swiss
> cheese.
> 
> Still, the range [0xde600,0xde700] is not freed and there should be struct
> pages for this range.
> 
> Can you add
> 
> 	dump_page(pfn_to_page(0xde600), "");
> 
> say, in the end of memblock_free_all()?
>   
> 
The range [0xde600,0xde700] is not memory, so it won't create struct 
page for it when sparse_init?

After apply patch[1], the dump_page log,

page:ef3cc000 is uninitialized and poisoned
raw: ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff
page dumped because:

[1] 
https://lore.kernel.org/linux-mm/20210512031057.13580-3-wangkefeng.wang@huawei.com/T/#u