Linux 7.3 Makes Preparations Toward Upstreaming FAMFS File-System

The NVDIMM and direct access (DAX) patches have been merged for the Linux 7.3 cycle. Most of the DAX/NVDIMM activity this cycle is on making preparations for the upcoming submission of Micron's FAMFS file-system. The DAX code with Linux 7.3 saw a number of fixes, code refactoring, and other improvements in preparing for the FAMFS introduction. Micron has been working on FAMFS for years (since at least 2024) as a special purpose file-system for fabric-attached memory (FAM) devices. Micron is hoping to see FAMFS upstreamed in 2026 and the patches for the file-system itself have now undergone thirteen rounds of patch review. This fabric-attached memory file system is going to be quite important for modern CXL servers moving forward. FAMFS is not for any general purpose file-system use but is designed around file-based, byte-level access to very large shared/disaggregated memory applications, in the scope of around 100TB+ memory being common. While there has been concerns over the proliferation of file-systems within the Linux kernel, FAMFS is designed specifically for this use. Micron engineers did experiment with porting to FUSE in user-space but ultimately have found a standalone file-system kernel driver is the best approach. Micron has also committed to maintaining FAMFS with having a clear customer need for it. This pull request landed all the NVDIMM and DAX changes for Linux 7.3. FAMFS has not been submitted yet for upstream inclusion but looks to be nearing the stage of being ready to be accepted. There is no indication though it will attempt to be submitted for the v7.3 merge window. For those interested there are the v13 patches if wanting to check out FAMFS in current form.