Since Linux 4.17, I have been working on an online filesystem checking feature for XFS. As I mentioned in the previous update, the online fsck tool (named xfs_scrub) walks all internal filesystem metadata records. Each record is checked for obvious corruptions before being cross-referenced with all other metadata in the filesystem. If problems are found, they are reported to the system administrator through both xfs_scrub and the health reporting system.
As of Linux 5.3 and xfsprogs 5.3, online checking is feature complete and has entered the stabilization and performance optimization stage. For the moment it remains tagged experimental, though it should be stable. We seek early adopters to try out this new functionality and give us feedback.