Re: [PATCH 0/2] virtio-fs: Add 'file' mount option

[Hanna Czenczek]

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.

Hanna