Strange! Cannot use JFFS2 as root

["colin" <colin@realtek.com.tw>]

Hi all,
I had booted up Linux with nfs root, and write a JFFS2 image to /dev/mtd1.
Here is my cmdline for Kernel:
     go 0x80305018 root=/dev/nfs rw nfsroot=172.19.26.145:/nfs/rootfs
ip=172.19.27.193::172.19.27.254:255.255.254.0:::
mtdparts=maltaflash:1536k(ldr),2048k(root)

After writing the JFFS2 image to /dev/mtd1, I can mount /dev/mtdblcok1 to
some directory.
    mount -t jffs2 /dev/mtdblock1 /mnt

Next, I hope to boot up Linux with JFFS2 root, and try to give this cmdline
to Kernel:
    go 0x80305018 rootfstype=jffs2
mtdparts=maltaflash:1536k(ldr),2048k(root) root=/dev/mtdblock1

and the Kernel would complain me about no root:
    VFS: Unable to mount root fs via NFS, trying floppy.
    Kernel panic: VFS: Unable to mount root fs on unknown-block(2,0)

I traced the code and found that when passing "/dev/mtdblock1" to
name_to_dev_t() in do_mounts.c, it would return 0 at every try_name(), which
will fail at open() with the path "/sys/block/%s/dev".

What's the problem? Could anyone tell me?

Thanks and regards,
Colin