[PATCH] reiserfs: zero b_private when allocating buffer heads

The b_private field in buffer heads needs to be zero filled when the
buffers are allocated.  Thanks to Nathan Scott for finding this.  It was
causing problems on systems with both XFS and reiserfs.

Signed-off-by: Chris Mason <mason@suse.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>