Date: Tue, 24 May 2011 09:28:51 +0400 From: "Andrey V. Elsukov" <bu7cher@yandex.ru> To: Warner Losh <imp@bsdimp.com> Cc: Marcel Moolenaar <marcel@freebsd.org>, Poul-Henning Kamp <phk@freebsd.org>, freebsd-geom@freebsd.org Subject: Re: [RFC] Remove requirement of alignment to track from MBR scheme Message-ID: <4DDB4213.1030008@yandex.ru> In-Reply-To: <AAB1B614-149F-49E3-9A9C-79B121E1B719@bsdimp.com> References: <4DDA2F0B.2040203@yandex.ru> <6DF62987-141B-4BB3-8E8D-9966EBAC828B@bsdimp.com> <4DDA9046.8050902@yandex.ru> <AAB1B614-149F-49E3-9A9C-79B121E1B719@bsdimp.com>
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On 23.05.2011 21:39, Warner Losh wrote:
>>> In any event, I'd be tempted to use a #define for 4096 like
>>> MBR_MAX_SECTOR_SIZE.
>>>
>>> -msize =3D MIN(pp->mediasize / pp->sectorsize, UINT32_MAX);
>>> +msize =3D MIN(pp->mediasize / pp->sectorsize, 2 * UINT32_MAX);
>>>
>>> Why this change? I think that it is in two places.
>>
>> Currently we have limit to msize =3D UINT32_MAX, but partition in MBR =
has
>> start offset and size (not end offset). Theoretically it can have size=
>> that is up to UINT32_MAX sectors, also start offset can be UINT32_MAX.=
>> And for example, for 4T disk we can have 2 partitions with 2TB size.
>=20
> Are there any extant examples of this? The CW is that the maximum size=
for an MBR device is 2TB.
I tried with 6T md(4) device and it is possible to create 2 partitions
with 2T size, but it is inconvenient to do:
# gpart show md0
=3D> 1 8589934589 md0 MBR (5.5T)
1 8589934589 - free - (4T)
# gpart add -t freebsd -s 2T md0
gpart: Invalid argument
# gpart add -t freebsd -s `printf %d 0xFFFFFFFE` md0
md0s1 added
# gpart add -t freebsd md0
md0s2 added
# gpart show md0
=3D> 1 8589934589 md0 MBR (5.5T)
1 4294967294 1 freebsd (2T)
4294967295 4294967295 2 freebsd (2T)
So, i updated the patch and removed this support. Also i removed some
checks that scheme independent code does.
--=20
WBR, Andrey V. Elsukov
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