The following XFS features have been implemented:

  • Support for reflink and deduplication.  Stability fixes and the in-memory extent map redesign for XFS reflink functionality have been backported from the upstream 4.15 kernel. These fixes and enhancements allow for the removal of EXPERIMENTAL warnings that were generated by the kernel at mount time and includes a fix that resolves an issue that was causing file system shutdowns when memory became too fragmented. The support for mapping multiple file logical blocks to the same physical block (reflink/deduplication) that this backport makes available to this release, brings XFS into line with other file systems such as OCFS2 and Btrfs.

    The user space packages for XFS, xfsprogs, have been updated to version 4.14 to properly handle XFS reflinking.

    DAX is disabled on reflink file systems and attempts to mount a reflink file system with DAX are rejected with an error message.

  • Synchronous DAX faults enabled.  UEK R5 enables use of synchronous DAX faults in the XFS file system. This change includes fixes to the libnvdimm code to improve DAX support and to introduce a mechanism to enable a user space flush of persistent memory updates by using file system to DAX mappings. Standard ACPI 6.2 label access and error injection methods are also available. Fixes were also applied to simplify error handling for DAX faults.

  • Realtime subvolume support enabled.  By default, UEK R5 enables XFS realtime subvolume support. This capability makes it possible to mount a realtime subvolume on systems running UEK R5.