[uml-user] udev "No space left on device" when mem= option not specified

[Chris B. <chr...@gm...>]

On boot Gentoo mounts a udev tmpfs to /dev and does tar -x of a device
tarball. This should only take about 450k, but with uml I have to
specify upto mem=3D50M otherwise it runs out of memory doing tar -x. Is
that normal? What's going on?

 * Configuring system to use udev ...
 *   Populating /dev with device nodes ...
/sbin/rc: line 25: cannot redirect standard input from /dev/null: No
such file or directory
[ oops ]

 * The "tar" command failed with error:

ttyp4: Cannot mknod: No space left on device
tar: ttyp5: Cannot mknod: No space left on device
tar: ttyp6: Cannot mknod: No space left on device
tar: ttyp7: Cannot mknod: No space left on device
tar: ttyp8: Cannot mknod: No space left on device
...

Thanks,
Chris