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

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Message-ID: <19877.54035.501749.870641@quad.stoffel.home>
Date:	Wed, 13 Apr 2011 12:45:07 -0400
From:	"John Stoffel" <john@...ffel.org>
To:	"Ted Ts'o" <tytso@....edu>
Cc:	Mark Lord <kernel@...savvy.com>,
	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

>>>>> "Ted" == Ted Ts'o <tytso@....edu> writes:

Ted> 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.

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

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

Should it instead be:  CONFIG_EXT4_MASQUERADE_AS_EXT23 instead, so
it's blindingly obvious what's going on here.

John
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