CONFIG_EXT4_USE_FOR_EXT23: rootfs shows as ext2 instead of ext4

From: Mark Lord
Date: Tue Apr 12 2011 - 13:25:18 EST

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.

Eg. I test it by building my own kernel (, with ext4 built-in,
no initramfs required, and boot:

root=/dev/sda1 init=/bin/bash
$ mount /proc
$ cat /proc/mounts
/dev/root / ext2 ro,relatime,barrier=1,data=ordered 0 0

So.. it shows "ext2" instead of "ext4". That really looks like a bug.
Especially since it appears to be using journaling regardless.

Building the kernel without CONFIG_EXT4_USE_FOR_EXT23
results in a proper "ext4" mount entry in /proc/mounts.

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