[PATCH] hfsplus: don't modify journaled volume

Access to a journaled HFS+ volume is not officially supported under Linux, so
mount such a volume read-only, but users can override this behaviour using the
"force" mount option.

The minimum requirement to relax this check is to at least check that the
journal is empty and so nothing needs to be replayed to make sure the volume
is consistent.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>