RE: [PATCH] msdos: add support for large disks

From: Daniel Taylor
Date: Wed Mar 03 2010 - 17:59:59 EST

-----Original Message-----
From: OGAWA Hirofumi [mailto:hirofumi@xxxxxxxxxxxxxxxxxx]
Sent: Wednesday, March 03, 2010 6:02 AM
To: Andrew Morton
Cc: Daniel Taylor; linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: [PATCH] msdos: add support for large disks

Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:

>> On Wed, 24 Feb 2010 19:17:47 -0800
>> "Daniel Taylor" <Daniel.Taylor@xxxxxxx> wrote:
>>> In order to use disks larger than 2TiB on Windows XP, it is necessary
>>> to use 4096-byte logical sectors in an MBR.

> BTW, you can use GPT instead?

Windows XP does not support GPT, although Vista/7 do.

> And to make sure, "4096-byte logical sectors in an MBR" is meaning, the
storage must be supporting 4096B and is using it?

The drives report physical/logical sector sizes of 4096 bytes, which the
kernel correctly detects. 32-bit fields in the MBR are then sufficient for
storage capacites >2TiB (up to 16 TiB), and the storage in struct
parsed_partitions is already sector_t.

>>> Although the kernel storage and functions called from msdos.c used
>>> "sector_t" internally, msdos.c still used u32 variables, which
>>> results in the ability to handle XP-compatible large disks.
>>> This patch changes the internal variables to "sector_t".
>> Please Cc OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> and myself on
>> this work.

>> BTW, to make sure, this is fs/partitions/, not fs/fat/. So, I'm not sure,
my knowledge is enough or not, and/or you just missed fs/partitions/.

This is definitely a change in fs/partitions (fs/partitions/msdos.c). I
could not find a maintainer for fs/partitions, but FAT and MBR are vaguely
related. Andrew Morton asked me to copy you on the change, also.

> Well, I'll make time to check. BTW, basically it sounds good to me except
implementation details. But, I'd like to compare > and check other implement
a bit if possible. IIRC, this is not a well defined specification.

Sanity checking patches is a good idea, particularly from someone who has no
other significant change in place.

> Thanks.
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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