GNU bug report logs - #77887
libparted detects ext4 without journal as ext2

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Pascal Hambourg <pascal <at> plouf.fr.eu.org>
To: bug-parted <at> gnu.org
Subject: libparted detects ext4 without journal as ext2
Date: Thu, 17 Apr 2025 22:06:30 +0200

[Message part 1 (text/plain, inline)]

Package: parted
Version: 3.6
Severity: minor
Tags: patch easy

Reference: <https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1103454>

Dear maintainers,

libparted wrongly detects ext4 without journal as ext2 instead of ext4.
Steps to reproduce:

truncate -s 1G blob
mkfs.ext4 -O ^has_journal blob
blkid blob -> ext4
parted blob print -> ext2
mount -t ext2 blob /mnt -> "couldn't mount as ext2 due to feature 
incompatibilities"
mount -t ext4 blob /mnt -> ok

In libparted/fs/ext2/interface.c, _ext2_generic_probe() considers ext4 
as a subset of ext3 which is ext2 with journal. IMO this is wrong 
because ext4 without journal may have other incompatible features.

Please consider the attached trivial patch (untested).

[detect-ext4-nojournal.patch (text/x-patch, attachment)]

Message #8 received at 77887 <at> debbugs.gnu.org (full text, mbox):

From: Pascal Hambourg <pascal <at> plouf.fr.eu.org>
To: 77887 <at> debbugs.gnu.org
Subject: Re: bug#77887: libparted detects ext4 without journal as ext2
Date: Fri, 18 Apr 2025 18:03:09 +0200

FWIW I did very basic testing with the patch applied on Debian, now 
parted detects ext* filesystems as expected:

mkfs.ext2 -> ext2
mkfs.ext3 -> ext3
mkfs.ext4 -> ext4
mkfs.ext4 -O ^has_journal -> ext4

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