Re: [RESEND v2 PATCH] init/do_mounts.c: add virtiofs root fs support

[David Heidelberg]

Thank you all!

We'll drop this patch in next MesaCI kernel uprev without this patch!

David

On 27/02/2023 19:06, Vivek Goyal wrote:
> On Mon, Feb 27, 2023 at 10:53:45AM -0500, Stefan Hajnoczi wrote:
> > On Fri, Feb 24, 2023 at 03:37:51PM +0100, David Heidelberg wrote:
> > > From: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> > >
> > > Make it possible to boot directly from a virtiofs file system with tag
> > > 'myfs' using the following kernel parameters:
> > >
> > >    rootfstype=virtiofs root=myfs rw
> > >
> > > Booting directly from virtiofs makes it possible to use a directory on
> > > the host as the root file system.  This is convenient for testing and
> > > situations where manipulating disk image files is cumbersome.
> > >
> > > Reviewed-by: Helen Koike <helen.koike@xxxxxxxxxxxxx>
> > > Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> > > Signed-off-by: David Heidelberg <david@xxxxxxx>
> > > ---
> > > v2: added Reviewed-by and CCed everyone interested.
> > >
> > > We have used this option in Mesa3D CI for testing crosvm for
> > > more than one years and it's proven to work reliably.
> > >
> > > We are working on effort to removing custom patches to be able to do
> > > automated apply and test of patches from any tree.
> > >
> > > https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/.gitlab-ci/crosvm-runner.sh#L85
> > >   init/do_mounts.c | 10 ++++++++++
> > >   1 file changed, 10 insertions(+)
> > Vivek, do you remember where we ended up with boot from virtiofs? I
> > thought a different solution was merged some time ago.
> We merged a patch from Christoph Hellwig to support this.
>
> commit f9259be6a9e7c22d92e5a5000913147ae17e8321
> Author: Christoph Hellwig <hch@xxxxxx>
> Date:   Wed Jul 14 16:23:20 2021 -0400
>
>      init: allow mounting arbitrary non-blockdevice filesystems as root
>
> Now one should be able to mount virtiofs using following syntax.
>
> "root=myfs rootfstype=virtiofs rw"
>
> IIUC, this patch should not be required anymore.
>
> Thanks
> Vivek
>
> > There is documentation from the virtiofs community here:
> > https://virtio-fs.gitlab.io/howto-boot.html
> >
> > Stefan
> >
> > > diff --git a/init/do_mounts.c b/init/do_mounts.c
> > > index 811e94daf0a8..11c11abe23d7 100644
> > > --- a/init/do_mounts.c
> > > +++ b/init/do_mounts.c
> > > @@ -578,6 +578,16 @@ void __init mount_root(void)
> > >   			printk(KERN_ERR "VFS: Unable to mount root fs via SMB.\n");
> > >   		return;
> > >   	}
> > > +#endif
> > > +#ifdef CONFIG_VIRTIO_FS
> > > +	if (root_fs_names && !strcmp(root_fs_names, "virtiofs")) {
> > > +		if (!do_mount_root(root_device_name, "virtiofs",
> > > +				   root_mountflags, root_mount_data))
> > > +			return;
> > > +
> > > +		panic("VFS: Unable to mount root fs \"%s\" from virtiofs",
> > > +		      root_device_name);
> > > +	}
> > >   #endif
> > >   	if (ROOT_DEV == 0 && root_device_name && root_fs_names) {
> > >   		if (mount_nodev_root() == 0)
> > > --
> > > 2.39.1
--
David Heidelberg
Consultant Software Engineer