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
next prev parent reply other threads:[~2020-11-08 5:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-07 15:22 [PATCH] mm/zsmalloc: include sparsemem.h for MAX_PHYSMEM_BITS 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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