linux-kernel - Re: CONFIG_EXT4_USE_FOR_EXT23: rootfs shows as ext2 instead of ext4

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Message-ID: <20110413004938.GE3682@thunk.org>
Date:	Tue, 12 Apr 2011 20:49:38 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Mark Lord <kernel@...savvy.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-ext4@...r.kernel.org
Subject: Re: CONFIG_EXT4_USE_FOR_EXT23:  rootfs shows as ext2 instead of
 ext4

On Tue, Apr 12, 2011 at 01:25:08PM -0400, Mark Lord wrote:
> Ted et al.
> 
> I've only just noticed this, so I have no idea how long it has been this way.
> 
> When I build a kernel with CONFIG_EXT4_USE_FOR_EXT23=y and boot from it,
> the ext4 root filesystem shows up as "ext2" mode, rather than "ext4".
> 
> This looks very wrong to me, and quite dangerous.

It's a cosemtic bug, I agree, but I'm not sure why you consider it
dangerous.

CONFIG_EXT4_USE_FOR_EXT23 means that ext4 registers itself as ext2
and/or ext3, if ext2 and/or ext3 are not configured into the kernel.
Since the kernel tries to mount the file system as ext2, ext3, and
then ext4, and uses whichever one works first.

						- Ted
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