[Virtio-fs] [PATCH] init/do_mounts.c: add virtio_fs root fs support

[Virtio-fs] [PATCH] init/do_mounts.c: add virtio_fs root fs support

[Stefan Hajnoczi]

It is useful to mount the root file system via virtio_fs.  During
testing a monolithic kernel is more convenient than an initramfs but
we'll need to teach the kernel how to boot directly from virtio_fs.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 init/do_mounts.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/init/do_mounts.c b/init/do_mounts.c
index f8c230c77035..b2d9650488d7 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -553,6 +553,16 @@ void __init mount_root(void)
 			change_floppy("root floppy");
 	}
 #endif
+#ifdef CONFIG_VIRTIO_FS
+	if (root_fs_names && !strcmp(root_fs_names, "virtio_fs")) {
+		if (!do_mount_root(root_device_name, "virtio_fs",
+				   root_mountflags, root_mount_data))
+			return;
+
+		panic("VFS: Unable to mount root fs \"%s\" from virtio_fs",
+		      root_device_name);
+	}
+#endif
 #ifdef CONFIG_BLOCK
 	{
 		int err = create_dev("/dev/root", ROOT_DEV);
-- 
2.21.0

Re: [Virtio-fs] [PATCH] init/do_mounts.c: add virtio_fs root fs support

[Dr. David Alan Gilbert]

* Stefan Hajnoczi (stefanha@redhat.com) wrote:
> It is useful to mount the root file system via virtio_fs.  During
> testing a monolithic kernel is more convenient than an initramfs but
> we'll need to teach the kernel how to boot directly from virtio_fs.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  init/do_mounts.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/init/do_mounts.c b/init/do_mounts.c
> index f8c230c77035..b2d9650488d7 100644
> --- a/init/do_mounts.c
> +++ b/init/do_mounts.c
> @@ -553,6 +553,16 @@ void __init mount_root(void)
>  			change_floppy("root floppy");
>  	}
>  #endif
> +#ifdef CONFIG_VIRTIO_FS
> +	if (root_fs_names && !strcmp(root_fs_names, "virtio_fs")) {
> +		if (!do_mount_root(root_device_name, "virtio_fs",
> +				   root_mountflags, root_mount_data))
> +			return;
> +
> +		panic("VFS: Unable to mount root fs \"%s\" from virtio_fs",
> +		      root_device_name);
> +	}
> +#endif

I wonder if it's possible to make this more generic; I see that
filesystems have a flag, FS_REQUIRES_DEV - should this
work for most filesystems that don't have that set?

Dave

>  #ifdef CONFIG_BLOCK
>  	{
>  		int err = create_dev("/dev/root", ROOT_DEV);
> -- 
> 2.21.0
> 
> _______________________________________________
> Virtio-fs mailing list
> Virtio-fs@redhat.com
> https://www.redhat.com/mailman/listinfo/virtio-fs
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Virtio-fs] [PATCH] init/do_mounts.c: add virtio_fs root fs support

[Stefan Hajnoczi]

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On Wed, Jul 31, 2019 at 11:34:08AM +0100, Dr. David Alan Gilbert wrote:
> * Stefan Hajnoczi (stefanha@redhat.com) wrote:
> > It is useful to mount the root file system via virtio_fs.  During
> > testing a monolithic kernel is more convenient than an initramfs but
> > we'll need to teach the kernel how to boot directly from virtio_fs.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> >  init/do_mounts.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/init/do_mounts.c b/init/do_mounts.c
> > index f8c230c77035..b2d9650488d7 100644
> > --- a/init/do_mounts.c
> > +++ b/init/do_mounts.c
> > @@ -553,6 +553,16 @@ void __init mount_root(void)
> >  			change_floppy("root floppy");
> >  	}
> >  #endif
> > +#ifdef CONFIG_VIRTIO_FS
> > +	if (root_fs_names && !strcmp(root_fs_names, "virtio_fs")) {
> > +		if (!do_mount_root(root_device_name, "virtio_fs",
> > +				   root_mountflags, root_mount_data))
> > +			return;
> > +
> > +		panic("VFS: Unable to mount root fs \"%s\" from virtio_fs",
> > +		      root_device_name);
> > +	}
> > +#endif
> 
> I wonder if it's possible to make this more generic; I see that
> filesystems have a flag, FS_REQUIRES_DEV - should this
> work for most filesystems that don't have that set?

I don't know the answer.  We'll have to ask when upstreaming.

Stefan

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