On Fri, 6 Oct 2023 at 20:12, John Groves <john@xxxxxxxxxxxxxx> wrote: > > I see that there is some limited support for dax mapping of fuse files, but > it seems to be specifically for virtiofs. I admit I barely understand that > use case, but there is another fuse/dax use case that I’d like to explore. > I would appreciate feedback on this, including pointers to RTFM material, > etc. > > I’m interested in creating a file system interface to fabric-attached shared > memory (cxl). Think of a fuse file system that receives metadata (how MD is > distributed is orthogonal) and instantiates files that are backed by dax > memory (S_DAX files), such that the same ‘data sets’ can be visible as > mmap-able files on more than one server. I’d like feedback as to whether > this is (or could be) doable via fuse. > > Here is the main rub though. For this to perform adequately, I don’t think > it would be acceptable for each fault to call up to user space to resolve > the dax device & offset. So the kernel side of fuse would need to cache a > dax extent list for each file to TLB/page-table misses. > > I would appreciate any questions, pointers or feedback. I think the passthrough patches should take care of this use case as well: https://lore.kernel.org/all/20230519125705.598234-1-amir73il@xxxxxxxxx/ Thanks, Miklos
