The EXT2 file-system’s direct access “DAX” mode is being deprecated and expected for removal at the end of 2025, after this year’s Long Term Support (LTS) kernel version.
Jan Kara of SUSE has queued ahead of the Linux 6.16 merge window is the patch deprecating the EXT2 DAX mode:
“Since PMEM didn’t quite lift off, DAX isn’t as widely used as we originally hoped. Thus it doesn’t seem warranted to support implementation of DAX in ext2 driver when the same filesystem can be accessed through ext4 driver as a “simple implementation”. Just deprecate DAX support in ext2 targetting completely dropping the code at the end of 2025.”
This is only about using EXT2 in DAX mode and not the EXT2 file-system driver itself. EXT2 DAX was intended for use with the likes of Intel Optane DC Persistent Memory that didn’t pan out and the products cancelled long ago. In DAX mode, the file-system avoids copies into the page cache and instead reads/writes directly to the memory-like storage device.
The EXT2 driver could operate in direct access mode with the “-o dax” mount option. The EXT2 driver’s DAX support only ever reached an experimental state and will now report:
“DAX enabled. Warning: DAX support in ext2 driver is deprecated and will be removed at the end of 2025. Please use ext4 driver instead.”
That removal at the end of 2025 for likely being the cycle after this year’s Long Term Support kernel version as the last kernel release of the calendar year. As noted, the EXT4 driver can still be used with DAX mode. XFS and EROFS also support DAX modes too for those with relevant persistent memory devices.
