Currently the only non-blockdevice filesystems that can be used as the initial root filesystem are NFS and CIFS, which use the magic "root=/dev/nfs" and "root=/dev/cifs" syntax that requires the root device file system details to come from filesystem specific kernel command line options.
Add a little bit of new code that allows to just pass arbitrary string mount options to any non-blockdevice filesystems so that it can be mounted as the root file system. For example a virtiofs root file system can be mounted using the following syntax: "root=myfs rootfstype=virtiofs rw" Based on an earlier patch from Vivek Goyal <[email protected]>. Signed-off-by: Christoph Hellwig <[email protected]> --- init/do_mounts.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/init/do_mounts.c b/init/do_mounts.c index ec32de3ad52b..64c60cb72ecb 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -534,6 +534,44 @@ static int __init mount_cifs_root(void) } #endif +static int __init try_mount_nodev(char *fstype) +{ + struct file_system_type *fs = get_fs_type(fstype); + int err = -EINVAL; + + if (!fs) + return -EINVAL; + if (!(fs->fs_flags & (FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA))) + err = do_mount_root(root_device_name, fstype, root_mountflags, + root_mount_data); + put_filesystem(fs); + + if (err != -EACCES && err != -EINVAL) + panic("VFS: Unable to mount root \"%s\" (%s), err=%d\n", + root_device_name, fstype, err); + return err; +} + +static int __init mount_nodev_root(void) +{ + char *fs_names, *p; + int err = -EINVAL; + + fs_names = (void *)__get_free_page(GFP_KERNEL); + if (!fs_names) + return -EINVAL; + split_fs_names(fs_names, root_fs_names); + + for (p = fs_names; *p; p += strlen(p) + 1) { + err = try_mount_nodev(p); + if (!err) + break; + } + + free_page((unsigned long)fs_names); + return err; +} + void __init mount_root(void) { #ifdef CONFIG_ROOT_NFS @@ -550,6 +588,8 @@ void __init mount_root(void) return; } #endif + if (ROOT_DEV == 0 && mount_nodev_root() == 0) + return; #ifdef CONFIG_BLOCK { int err = create_dev("/dev/root", ROOT_DEV); -- 2.30.2 _______________________________________________ Virtio-fs mailing list [email protected] https://listman.redhat.com/mailman/listinfo/virtio-fs
