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From: Florian Fainelli <f.fainelli@gmail.com>
To: Stefan Agner <stefan@agner.ch>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: minchan@kernel.org, ngupta@vflare.org,
	sergey.senozhatsky.work@gmail.com, sjenning@linux.vnet.ibm.com,
	gregkh@linuxfoundation.org, arnd@arndb.de, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/zsmalloc: include sparsemem.h for MAX_PHYSMEM_BITS
Date: Sat, 7 Nov 2020 20:54:13 -0800	[thread overview]
Message-ID: <29cb13a4-e10d-a394-3c00-1d7721a2dc0a@gmail.com> (raw)
In-Reply-To: <fb776accd14ddb5ec1251a6147a2ff45@agner.ch>



On 11/7/2020 5:16 PM, Stefan Agner wrote:
> On 2020-11-08 01:56, Andrew Morton wrote:
>> On Sat,  7 Nov 2020 16:22:06 +0100 Stefan Agner <stefan@agner.ch> wrote:
>>
>>> Most architectures define MAX_PHYSMEM_BITS in asm/sparsemem.h and don't
>>> include it in asm/pgtable.h. Include asm/sparsemem.h directly to get
>>> the MAX_PHYSMEM_BITS define on all architectures.
>>>
>>> This fixes a crash when accessing zram on 32-bit ARM platform with LPAE and
>>> more than 4GB of memory:
>>>   Unable to handle kernel NULL pointer dereference at virtual address 00000000
>>
>> Mysterious.  Presumably without this include, some compilation unit is
>> picking up the wrong value of MAX_PHYSMEM_BITS?  But I couldn't
>> actually see where/how this occurs.  Can you please explain further?
> 
> Not sure if I got that right, but from what I understand if
> MAX_PHYSMEM_BITS is not set in mm/zsmalloc.c it will set
> MAX_PHYSMEM_BITS to BITS_PER_LONG. And this is 32-bit, too short when
> LPAE is in use...

You should probably include this in your commit message since that is
describing the bug and then your fix makes complete sense.
-- 
Florian


  reply	other threads:[~2020-11-08  4:54 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-07 15:22 Stefan Agner
2020-11-08  0:56 ` Andrew Morton
2020-11-08  1:16   ` Stefan Agner
2020-11-08  4:54     ` Florian Fainelli [this message]
2020-11-09 17:04     ` Minchan Kim
2020-11-08  6:46 ` Mike Rapoport
2020-11-10  9:29   ` Stefan Agner
2020-11-10  9:58     ` Mike Rapoport
2020-11-10 11:21       ` Arnd Bergmann
2020-11-10 12:22         ` Stefan Agner
2020-11-10 15:19           ` Arnd Bergmann
2020-11-10 16:21         ` Mike Rapoport
2020-11-10 23:36           ` Minchan Kim
2020-11-11  6:52             ` Mike Rapoport
2020-11-12 19:49               ` Minchan Kim
2020-11-11  9:33           ` Arnd Bergmann
2020-11-11 10:26             ` Mike Rapoport
2020-11-11 10:57               ` Arnd Bergmann
2020-11-11 11:04                 ` Mike Rapoport
2020-11-11 13:39                 ` Thomas Bogendoerfer
2020-11-11 14:33                   ` Arnd Bergmann
2020-11-12 19:50                     ` Minchan Kim
2020-11-12 23:46 ` Florian Fainelli

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