From: Ted Ts'o <tytso@mit.edu>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: "Richard W.M. Jones" <rjones@redhat.com>,
Ext4 Developers List <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH 2/2] libext2fs: fix bad cast which causes problems for file systems > 512EB
Date: Tue, 4 Oct 2011 14:05:55 -0400 [thread overview]
Message-ID: <20111004180555.GB10007@thunk.org> (raw)
In-Reply-To: <4E8AF240.7010905@sandeen.net>
On Tue, Oct 04, 2011 at 06:47:12AM -0500, Eric Sandeen wrote:
> On 10/3/11 11:27 PM, Theodore Ts'o wrote:
> > If the number of block groups exceeds 2**32, a bad cast would lead to
> > a bogus "Not enough space to build proposed filesystem while setting
> > up superblock" failure.
>
> It's the proper cast now, but I don't think it fixes the problem, since they
> are both __u32...
Hmm, yes.
And to be quite honest I'm not sure it's worth fixing. 2**32 block
groups gets us up to 2**59 bytes assuming 4k blocks. The theoretical
maximum given the current extent tree format is 2**60 assuming 4k
blocks. So changing dgrp_t to be 64-bits just to get that last power
of two (i.e., from 512EB to a full PB) doesn't seem worth it. Simply
using a bigalloc cluster size of 8k would make the problem go away
(and arguably we'd probably want a large cluster size if someone
wanted to create a file system that big anyway).
So maybe we should just check to see if the required number of block
groups is greater than 2**32, and if so, give an error.
- Ted
next prev parent reply other threads:[~2011-10-04 18:05 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-03 21:55 mkfs'ing a 48-bit fs... or not Eric Sandeen
2011-10-04 4:00 ` Ted Ts'o
2011-10-04 4:26 ` [PATCH 1/2] Add "big" and "huge" types to mke2fs.conf Theodore Ts'o
2011-10-04 4:27 ` [PATCH 2/2] libext2fs: fix bad cast which causes problems for file systems > 512EB Theodore Ts'o
2011-10-04 11:47 ` Eric Sandeen
2011-10-04 18:05 ` Ted Ts'o [this message]
2011-10-04 18:15 ` Eric Sandeen
2011-10-04 5:31 ` mkfs'ing a 48-bit fs... or not Andreas Dilger
2011-10-04 4:03 ` Eric Sandeen
2011-10-04 4:28 ` Ted Ts'o
2011-10-04 7:06 ` Richard W.M. Jones
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