The XFS file-system is ready to declare their online file-system checking “fsck” support in good enough shape for enabling by default in new kernel builds. Plus other XFS alterations ahead of Linux 6.18 that is expected to be this year’s LTS kernel version.
With the Linux 6.18 merge window set to kickoff in just a few weeks and then debut as stable in December, this will more than likely be the 2025 LTS kernel version. Typically it’s the last major released kernel version of a given calendar year that goes on to become the Long Term Support (LTS) version. So with Linux 6.18 likely to be an LTS kernel release, XFS file-system developers have been making preparations for that assumption.
Within the XFS development tree they have queued some Kconfig updates. First up they are now disabling by default two features they had planned to turn off as being previously deprecated: their V4 file-systems support and their long-broken ASCII case insensitive directories support.
The XFS V4 file-system format lacks features like metadata checksumming, better metadata verification, Y2038+ support, etc. The plan has been to disable XFS_SUPPORT_V4 for kernel builds beginning in September 2025 and to then remove the support entirely by September 2030. Most XFS users should have already migrated to new partitions with the V5 file-system format otherwise it should be high priority to do so now. XFS V5 has been around since Linux 5.10 in 2020.
The deprecated case-insensitive ASCII format support has also been known for disabling by default in 2025 and then removing entirely in 2030. This case insensitive code only works using ISO 8859-1, doesn’t work with extended attributes, and isn’t recommended for use.
But the most exciting aspect of these Kconfig updates for XFS in 2025 is enabling online fsck support by default. Carlos Maiolino commented with the updates that no major issues have turned up since the code was introduced 16 months ago and should be deemed good enough for enabling by default.
Darrick Wong commented with the patch to enable XFS_ONLINE_SCRUB by default:
“Online fsck has been a part of upstream for over a year now without any serious problems. Turn it on by default in time for the 2025 LTS kernel, and get rid of the “say N if unsure” messages for the default Y options.”
The XFS online scrub/fsck capability allows checking metadata on a mounted XFS file-system. Problems can be analyzed proactively without having to take the file-system offline.
These and other great changes are lining up ahead of the Linux 6.18 merge window in a few weeks.
