Re: [PATCH] docs: ext4 filesystems can be converted to 64-bit

[Daniel Pereira]

On Wed, Oct 14, 2026, Stephen Kitt wrote:
> Since commit fe12931 ("resize2fs: convert fs to and from 64bit mode")
> in e2fsprogs, which shipped in version 1.43, resize2fs can convert
> filesystems from 32-bit to 64-bit and back, so the mention in the
> checksum documentation that this is impossible is obsolete.

Hi Stephen,

I checked the claims against the e2fsprogs sources: commit fe12931 is
"resize2fs: convert fs to and from 64bit mode" (Darrick J. Wong), the
v1.43 RELEASE-NOTES say that resize2fs can now convert file systems
between 64-bit and 32-bit mode, and resize/main.c at v1.43 accepts -b
(enable 64bit) and -s (disable 64bit), which v1.42.13 does not have. So
the new text is accurate. This was also the only place in
Documentation/filesystems/ext4/ that mentioned the old limitation.

I built the documentation with the patch applied and it adds no new
warnings. checkpatch only complains about the unknown commit id, which
is expected since it is an e2fsprogs commit.

One optional suggestion, which does not change my review: in v1.43
resize2fs refuses to change the 64bit feature while the filesystem is
mounted ("Cannot change the 64bit feature while the filesystem is
mounted."), and enabling it also requires the extents feature. Since
the sentence replaces one that was about a limitation, it might be
worth saying that the conversion is done on an unmounted filesystem,
for example:

``resize2fs`` in ``e2fsprogs`` 1.43 or later can be used to convert
unmounted filesystems from 32-bit to 64-bit and back (using the
``-b`` and ``-s`` options).

Reviewed-by: Daniel Pereira <danielmaraboo@xxxxxxxxx>

Thanks,
Daniel