From: Eric Sandeen <sandeen@redhat.com>
Subject: Re: Creating a >32bit blocks filesystem.
Date: Wed, 09 May 2007 10:21:44 -0500
Message-ID: <4641E708.1090109@redhat.com>
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Cc: "Jose R. Santos" <jrs@us.ibm.com>, linux-ext4@vger.kernel.org
To: Valerie Clement <valerie.clement@bull.net>
In-Reply-To: <4641E13D.906@bull.net>
Sender: linux-ext4-owner@vger.kernel.org

Valerie Clement wrote:
> Jose R. Santos wrote:
>> I think this has more to do with the fact that I'm on a 32bit
>> architecture and there are still a couple places where blocks are
>> represented using "unsigned long".  I'm trying to get access to a 64=
bit
>> arch to confirm this.
>>
>> -JRS
>>
> Oh, I didn't catch that you use a 32-bit system.
> On 32-bit architectures, the page cache index size imposes a 16TB lim=
it=20
> on the filesystem size (with 4KB blocksize). So you need a 64-bit sys=
tem=20
> for your test.
>    Val=C3=A9rie

hm, the mount never should have gotten far enough to fail due to this,
should it have?

Jose, what exactly failed?  I see references to debugfs failing, but
also kernel logs...

Things like debugfs will have issues with very large block devices due
to maximum file size restrictions on 32-bit platforms, due to the page
cache issue Valerie mentions...  But trying to open it should give EFBI=
G
I'd think?

And mounting such a filesystem on a 32-bit system should also get
rejected early (and cleanly).

Jose, you mentioned that some blocks are still "unsigned long" on
32-bits... they shouldn't be, the LBD work should have fixed all those
long ago.  But there is still the 16TB page cache limit in force.

-Eric