[parted-devel] [PATCH] Detect Ext4 (Parted Alioth #188)

[Debarshi Ray]

> Here ([1] and below) is the 'git format-patch ...' with an added test case.
>
> [...]
>
> [1] http://rishi.fedorapeople.org/gnu/0001-Differentiate-between-Ext4-and-Ext3-file-systems.-Fi.patch

I have updated the patch at the above URL as per some of Jim
Meyering's suggestions on IRC.

While looking at the way TestDisk [2] does the same thing, I found
that they look for the following features in src/ext2.c:
EXT4_FEATURE_RO_COMPAT_HUGE_FILE
EXT4_FEATURE_RO_COMPAT_GDT_CSUM
EXT4_FEATURE_RO_COMPAT_DIR_NLINK
EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE
EXT4_FEATURE_INCOMPAT_64BIT
EXT4_FEATURE_INCOMPAT_MMP

Interestingly, they don't look for EXT4_FEATURE_INCOMPAT_EXTENTS. Must
be a mistake on their part since they have defined the constant and
not used it. Looking at the Ext4 wiki [3], I added checks for the
following features in Parted:
EXT4_FEATURE_RO_COMPAT_HUGE_FILE
EXT4_FEATURE_RO_COMPAT_DIR_NLINK
EXT4_FEATURE_INCOMPAT_EXTENTS
EXT4_FEATURE_INCOMPAT_64BIT

What do you think?

Happy hacking,
Debarshi

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[2] http://www.cgsecurity.org/wiki/TestDisk
[3] http://ext4.wiki.kernel.org/index.php/Frequently_Asked_Questions#What_are_the_key_differences_between_ext3_and_ext4.3F