tmpfs: interleave the starting node of /dev/shmem

tmpfs: interleave the starting node of /dev/shmem

The tmpfs superblock grants an offset for each inode as they are created.
Each inode then uses that offset to provide a preferred first node for its
interleave in the newly provided shmem_interleave.

Signed-off-by: Nathan Zimmer <nzimmer@sgi.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>