F2FS Brings Interesting "Device Aliasing" Feature To Linux 6.13 To Carve Out Partition

The Flash Friendly File-System (F2FS) updates were sent out on Monday for Linux 6.13 and include one very interesting new feature for this file-system: device aliasing as a means of being able to temporarily carve out a portion of the partition for other purposes.

At the start of the month I wrote about the F2FS device aliasing feature in development that with the "device aliasing file" can be even used to temporarily have another file-system within the F2FS partition. The documentation describes the device aliasing feature as:

"f2fs can utilize a special file called a "device aliasing file." This file allows the entire storage device to be mapped with a single, large extent, not using the usual f2fs node structures. This mapped area is pinned and primarily intended for holding the space.

Essentially, this mechanism allows a portion of the f2fs area to be temporarily reserved and used by another filesystem or for different purposes. Once that external usage is complete, the device aliasing file can be deleted, releasing the reserved space back to F2FS for its own use."

The F2FS device aliasing files can be created using mkfs.f2fs and could be used for holding another file-system for a VM/container, testing, or other purposes.

F2FS maintainer Jaegeuk Kim sums up the device aliasing support in the 6.13 pull request as "device aliasing feature where user can carve out partitions but reclaim the space back by deleting aliased file in root dir." The F2FS updates for Linux 6.13 alsoo include bug fixes, new multi-device stats in DebugFS, a sysfs node to limit the max read extent count per-inode, and decreasing the spare area for pinned files on zoned devices.