XFS In Linux 4.12 Adds GETFSMAP Support

The XFS file-system changes have been submitted for Linux 4.12 and includes one main feature change.

The prominent new feature for XFS in Linux 4.12 is support for the GETFSMAP ioctl. This new ioctl has been under discussion since last year's Linux Storage summit and is the first Linux file-system seeing mainline support for it. GETFSMAP is used for returning all known space mapping details for that file-system.

In terms of its use-case as described in earlier versions of the GETFSMAP patches, "Space mapping information can be dumped via the xfs_io 'fsmap' command, and the upcoming xfs_spaceman utility analyzes the free extent data to produce free space fragmentations reports. Further in the future, the xfs_scrub utility will use GETFSMAP to assist in data block read verification."

Besides GETFSMAP support, XFS in Linux 4.12 has a number of fixes, code clean-ups, some code refactoring, and other changes. More details via this pull request.