On Wed, Dec 12, 2018 at 03:30:49PM -0500, Konrad Rzeszutek Wilk wrote: > On Mon, Dec 10, 2018 at 12:12:26PM -0500, Vivek Goyal wrote: > > Hi, > > > > Here are RFC patches for virtio-fs. Looking for feedback on this approach. > > > > These patches should apply on top of 4.20-rc5. We have also put code for > > various components here. > > > > https://gitlab.com/virtio-fs > > > > Problem Description > > =================== > > We want to be able to take a directory tree on the host and share it with > > guest[s]. Our goal is to be able to do it in a fast, consistent and secure > > manner. Our primary use case is kata containers, but it should be usable in > > other scenarios as well. > > > > Containers may rely on local file system semantics for shared volumes, > > read-write mounts that multiple containers access simultaneously. File > > system changes must be visible to other containers with the same consistency > > expected of a local file system, including mmap MAP_SHARED. > > > > Existing Solutions > > ================== > > We looked at existing solutions and virtio-9p already provides basic shared > > file system functionality although does not offer local file system semantics, > > causing some workloads and test suites to fail. In addition, virtio-9p > > performance has been an issue for Kata Containers and we believe this cannot > > be alleviated without major changes that do not fit into the 9P protocol. > > > > Design Overview > > =============== > > With the goal of designing something with better performance and local file > > system semantics, a bunch of ideas were proposed. > > > > - Use fuse protocol (instead of 9p) for communication between guest > > and host. Guest kernel will be fuse client and a fuse server will > > run on host to serve the requests. Benchmark results (see below) are > > encouraging and show this approach performs well (2x to 8x improvement > > depending on test being run). > > > > - For data access inside guest, mmap portion of file in QEMU address > > space and guest accesses this memory using dax. That way guest page > > cache is bypassed and there is only one copy of data (on host). This > > will also enable mmap(MAP_SHARED) between guests. > > > > - For metadata coherency, there is a shared memory region which contains > > version number associated with metadata and any guest changing metadata > > updates version number and other guests refresh metadata on next > > access. This is still experimental and implementation is not complete. > > What about Windows guests or BSD ones? Is there a plan to make that work with them as well? Hi Konrad, I have not thought much about making it work on Windows or BSD yet. Does Fuse work with windows. I am assuming it does with BSD. As long as FUSE works, I am assuming that atleast basic mode can be made to work. > > What about the Virtio spec? Plans to make changes there as well? There are plans to change that. Stefan posted a proposal here. https://lists.oasis-open.org/archives/virtio-dev/201812/msg00073.html Thanks Vivek
