On Wed, Jul 10, 2024 at 09:28:08AM +0200, Hanna Czenczek wrote: > On 09.07.24 19:56, Josef Bacik wrote: > > On Tue, Jul 09, 2024 at 01:19:16PM +0200, Hanna Czenczek wrote: > > > Hi, > > > > > > We want to be able to mount filesystems that just consist of one regular > > > file via virtio-fs, i.e. no root directory, just a file as the root > > > node. > > > > > > While that is possible via FUSE itself (through the 'rootmode' mount > > > option, which is automatically set by the fusermount help program to > > > match the mount point's inode mode), there is no virtio-fs option yet > > > that would allow changing the rootmode from S_IFDIR to S_IFREG. > > > > > > To do that, this series introduces a new 'file' mount option that does > > > precisely that. Alternatively, we could provide the same 'rootmode' > > > option that FUSE has, but as laid out in patch 1's commit description, > > > that option is a bit cumbersome for virtio-fs (in a way that it is not > > > for FUSE), and its usefulness as a more general option is limited. > > > > > All this does is make file an alias for something a little easier for users > > to > > read, which can easily be done in libfuse. Add the code to lib/mount.c to > > alias > > 'file' to turn it into rootmode=S_IFREG when it sends it to the kernel, > > it's not > > necessary to do this in the kernel. Thanks, > > This series is not about normal FUSE filesystems (file_system_type > fuse_fs_type, “fuse”), but about virtio-fs (file_system_type virtio_fs_type, > “virtiofs”), i.e. a case where libfuse and fusermount are not involved at > all. As far as I’m aware, mounting a virtio-fs filesystem with a > non-directory root inode is currently not possible at all.
Ok so I think I had it backwards in my head, my apologies. That being said I still don't understand why this requires a change to virtiofs at all. I have a virtiofs thing attached to my VM. Inside the vm I do mount -t virtiofs <name of thing I've attached to the vm> /directory and then on the host machine, virtiofsd is a "normal" FUSE driver, except it's talking over the socket you setup between the guest and the host. I assume this is all correct? So then the question is, why does it matter what virtiofsd is exposing? I guess that's the better question. The guest shouldn't have to care if it's a directory or a file right? The mountpoint is going to be a directory, whatever is backing it shouldn't matter. Could you describe the exact thing you're trying to accomplish? Thanks, Josef
