Linux Turning Off The Light - The LightNVM Subsystem To Be Removed
Merged to the mainline Linux kernel six years ago was the LightNVM subsystem as part of Linux 4.4 LTS around "Open-Channel SSDs". That LightNVM code is now slated for removal with the upcoming Linux 5.15 cycle.
LightNVM was focused on features around predictable latency, I/O isolation, and better memory management. However, LightNVM has been effectively superseded by the Zoned Namespace (ZNS) command set with NVMe.
There hasn't been much happening upstream with LightNVM in the past two years due to the zoned storage support in NVMe succeeding it and needless to say not any real kernel activity as a result. Thus this relatively short-lived LightNVM code is now expected to be removed next kernel merge window with the subsystem now removed in the block subsystem's "for-next" branch.
ZNS SSD details for those interested are outlined on ZonedStorage.io.
Deleting LightNVM from the Linux kernel shrinks the massive open-source kernel by some 13.6k lines of code. Christoph Hellwig wrote for the merge:
Lightnvm supports the OCSSD 1.x and 2.0 specs which were early attempts to produce Open Channel SSDs and never made it into the NVMe spec proper. They have since been superceeded by NVMe enhancements such as ZNS support. Remove the support per the deprecation schedule.