XFS update in Linux 5.19 brings ‘a lot of new code’

An update to the XFS filesystem was made during the Linux 5.19 merge window. 

According to the presentation , this is a big update with a lot of new code; two of the main new features are support for Large Extent Counts and Logged Attribute Replay. 

Developer Dave Chinner said his plan will be to build “more complex future features” on top of the two new foundational features.

Dave Chinner explained:

For upcoming features, we need to be able to store hundreds of millions of xattrs on each node. The Large Extent Count feature removes the limitation preventing xattr storage of this size, and when we modify the on-disk extent count format, we also increase the number of data extents supported per node from 2^32 to 2^47.

We also need to be able to modify xattrs as part of larger atomic transactions, not as standalone transactions. The Logged Attribute Replay feature introduces infrastructure that allows us to use intents to log attribute modifications before initiating attribute modifications, thus allowing other atomic transactions to log attribute modification intents and then defer the actual modification to a later time. In the event of a crash, log recovery guarantees that attributes are replayed in the context of the atomic transaction that logged the intent.

A large portion of the commits in this merge are for basic attribute replay functionality, as well as fixes, improvements, and cleanups related to this new feature. Allison deserves thanks for her work on getting this feature into XFS.

There are many other smaller changes and improvements, so overall this is one of the larger XFS merge requests in a while.

In addition to XFS will be able to scale to 4 billion data extensions and billions of xattrs per node, there are improvements to real-time range accounting, improvements to rmap btree searches, and a 30% reduction in overhead, as well as a reduction in the xfs_scrub runtime about 15%. 

There are various other improvements visible in Git merge .