On Mon, Apr 29, 2024 at 07:32:55PM +0100, Matthew Wilcox wrote: > On Mon, Apr 29, 2024 at 12:04:16PM -0500, John Groves wrote: > > This patch set introduces famfs[1] - a special-purpose fs-dax file system > > for sharable disaggregated or fabric-attached memory (FAM). Famfs is not > > CXL-specific in anyway way. > > > > * Famfs creates a simple access method for storing and sharing data in > > sharable memory. The memory is exposed and accessed as memory-mappable > > dax files. > > * Famfs supports multiple hosts mounting the same file system from the > > same memory (something existing fs-dax file systems don't do). > > Yes, but we do already have two filesystems that support shared storage, > and are rather more advanced than famfs -- GFS2 and OCFS2. What are > the pros and cons of improving either of those to support DAX rather > than starting again with a new filesystem? I could see a shared memory filesystem as being a completely different beast than a shared block storage filesystem - and I've never heard anyone talking about gfs2 or ocfs2 as codebases we particularly liked. This looks like it might not even be persistent? Does it survive a reboot? If not, that means it'll be much smaller than a conventional filesystem. But yeah, a bit more on where this is headed would be nice. Another concern is that every filesystem tends to be another huge monolithic codebase without a lot of code sharing between them - how much are we going to be adding in the end? Can we start looking for more code sharing, more library code to factor out? Some description of the internal data structures would really help here.
