[Virtio-fs] [RFC][PATCH] init: Allow mounting virtio_fs instance as rootfs

[Stefan Hajnoczi]

On Thu, Jul 25, 2019 at 04:49:34PM -0400, Vivek Goyal wrote:
> Hi Stefan,
> 
> I think following patch might allow you to mount virtio_fs as rootfs
> with new syntax.

Thanks, I've sent a similar patch too.  My patch changes mount_root()
(where the nfs root code also lives) and uses do_mount_root() instead of
mount_block_root() to avoid block/partition error messages.  But I think
they are very similar in terms of functionality.

> I have only compiled it and not tested it. Plase have a look.
> 
> Thanks
> Vivek
> 
> virtio_fs passes root=<fs-instance-name> as identifier of virtio_fs instance
> to be mounted. None of the existing primitives seems to fit virito_fs needs.
> 
> So check rootfstype and if it is "virtio_fs", do not parse root= further
> and call mount_block_root().
> 
> This is similar to carving out special paths for ubifs. Now virtio_fs
> users should be able to pass "root=myfs rootfstype=virtio_fs" and be
> able to mount that particular instance of virtio_fs as rootfs.
>  
> Yet-To-Be-Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
> ---
>  init/do_mounts.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> Index: rhvgoyal-linux-fuse/init/do_mounts.c
> ===================================================================
> --- rhvgoyal-linux-fuse.orig/init/do_mounts.c	2019-04-09 15:42:17.096602971 -0400
> +++ rhvgoyal-linux-fuse/init/do_mounts.c	2019-07-25 16:40:29.226348627 -0400
> @@ -595,6 +595,10 @@ void __init prepare_namespace(void)
>  			mount_block_root(root_device_name, root_mountflags);
>  			goto out;
>  		}
> +		if (root_fs_names && !strncmp(root_fs_names, "virtio_fs", 3)) {

The entire string, not just the first 3 characters:

  !strcmp(root_fs_names, "virtio_fs")
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 488 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/virtio-fs/attachments/20190729/e5ee429b/attachment.sig>