linux-ext4 - Re: EXT4 >16TB resize2fs support

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Message-id: <00E93B30-1C92-4185-8E80-B4AD840183B5@sun.com>
Date:	Fri, 30 Oct 2009 09:17:57 -0600
From:	Andreas Dilger <adilger@....com>
To:	Justin Maggard <jmaggard10@...il.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: EXT4 >16TB resize2fs support

On 2009-10-29, at 15:54, Justin Maggard wrote:
> What is the current expected status of resize2fs support with 64-bit
> filesystems?  Specifically, expanding from <16TB to >16TB.  I'm using
> the latest code from pu, and seeing some odd things.  I'm not sure
> what the 64bit feature flag does exactly, but is the transition not
> handled properly?

This isn't supposed to work at all, and in fact should be disabled.
Firstly, the group descriptors are not big enough to hold the 64-bit
block addresses unless the filesystem was originally formatted > 16TB.

Secondly, the resize code has not been made 64-bit clean.

> So... what is expected to work at this point, and what is expected to
> be broken with the resize process?  Any idea why my fs was shrunk down
> to 2.2TB when it was supposed to grow to 18TB?


The filesystem size was truncated to a 32-bit value.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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