linux-ext4 - Re: with -b N and block count, should mkfs.ext4 fail with dev-too-big?

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Message-ID: <499327D2.8010502@redhat.com>
Date:	Wed, 11 Feb 2009 13:32:34 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Valerie Aurora Henson <vaurora@...hat.com>
CC:	Theodore Tso <tytso@....edu>, Jim Meyering <jim@...ering.net>,
	ext <linux-ext4@...r.kernel.org>
Subject: Re: with -b N and block count, should mkfs.ext4 fail with dev-too-big?

Valerie Aurora Henson wrote:
> On Wed, Feb 11, 2009 at 09:09:05AM -0500, Theodore Tso wrote:
>> On Wed, Feb 11, 2009 at 01:50:39PM +0100, Jim Meyering wrote:
>>> FWIW, I was trying to create an ext4 file system with more than 2^32
>>> blocks to demonstrate a parted bug fix, but with the particular device
>>> I was using, I couldn't even create one with 2^31-1 blocks.
>>>
>>> When I try to create an ext4 file system specifying both block size and
>>> the number of blocks, the size of the underlying device should not matter,
>>> as long as it is large enough.
>> Oops, my fault.  I fixed the case where the device was exactly 16TB
>> (as in created via lvcreate --size 16TB, but the fix was very minimal,
>> since it was just before a maintenance release.  I didn't consider (or
>> test) the case where the device was larger than or equal to 2*32
>> blocks (given a specified blocksize, or 4k if no blocksize was
>> specified), and an explicit block size less than 2*32 was specified.
>>
>> I'll put it on my todo list to fix for e2fsprogs 1.41.5.
> 
> Note that this is fixed in effect by the 64bit patches, since we use
> the 64bit get device size function.
> 
> git://git.kernel.org/pub/scm/fs/ext2/val/e2fsprogs.git
> 
> Branch "shared-64bit".
> 
> -VAL

That won't fix it for ext3 though will it?  (not that I've looked in
detail) but the issue is not whether we can properly get the device
size; it's that the device size, rather than the filesystem size, is
checked for overflow vs. the filesystem's limits...

-Eric
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