linux-ext4 - Re: Creating a >32bit blocks filesystem.

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Message-ID: <4641E708.1090109@redhat.com>
Date:	Wed, 09 May 2007 10:21:44 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Valerie Clement <valerie.clement@...l.net>
CC:	"Jose R. Santos" <jrs@...ibm.com>, linux-ext4@...r.kernel.org
Subject: Re: Creating a >32bit blocks filesystem.

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 64bit
>> 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 limit 
> on the filesystem size (with 4KB blocksize). So you need a 64-bit system 
> for your test.
>    Valérie

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 EFBIG
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
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