Bug 15391

Summary:	EXT4_USE_FOR_EXT23 causes ext4 partition to be mounted as ext2
Product:	File System	Reporter:	Alec Moskvin (alecm)
Component:	ext4	Assignee:	fs_ext4 (fs_ext4)
Status:	RESOLVED CODE_FIX
Severity:	normal	CC:	alan, cruzki123, geogriffin, tytso
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.35	Subsystem:
Regression:	No	Bisected commit-id:

Description Alec Moskvin 2010-02-25 03:05:23 UTC

After setting "Use ext4 for ext2/ext3 file systems" and rebooting, my root filesystem gets mounted as ext2. When the option is disabled, everything works as expected.

Here are some relevant output:

$ grep ext[24] /etc/fstab
/dev/sda1       /boot  ext2    noauto,noatime      1 2
/dev/sda5       /      ext4    noatime             0 1

$ mount | grep ext[24]
/dev/root on / type ext2 (rw,noatime,barrier=1,data=ordered)
/dev/sda1 on /boot type ext2 (rw,noatime)

$ dmesg | grep -i ext[24]
EXT4-fs (sda5): mounted filesystem with ordered data mode
VFS: Mounted root (ext2 filesystem) readonly on device 259:131072.
EXT4-fs (sda1): mounted filesystem without journal

$ uname -a
Linux tux 2.6.33 #1 SMP PREEMPT Wed Feb 24 16:00:09 EST 2010 x86_64 Intel(R) Core(TM)2 CPU T5300 @ 1.73GHz GenuineIntel GNU/Linux

Comment 1 Alec Moskvin 2010-08-12 16:27:54 UTC

This bug is still present in Linux 2.6.35.1, but it can be easily worked-around by appending "rootfstype=ext4" to the boot options.

Comment 2 Theodore Tso 2010-08-13 03:57:35 UTC

It's actually getting mounted using the ext4 file system driver.  It's just that is getting identified as ext2 in /proc/mounts.  Whether or not users see this depends on their init scripts, and especially whether they have an initrd.   It is only a cosmetic issue, so it's low priority, but I do agree we should try to fix it.