[PATCH] ReiserFS: Make sure all dentries refs are released before calling kill_block_super()

Make sure all dentries refs are released before calling kill_block_super()
so that the assumption that generic_shutdown_super() can completely destroy
the dentry tree for there will be no external references holds true.

What was being done in the put_super() superblock op, is now done in the
kill_sb() filesystem op instead, prior to calling kill_block_super().

Changes made in [try #2]:

 (*) reiserfs_kill_sb() now checks that the superblock FS info pointer is set
     before trying to dereference it.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: <reiserfs-dev@namesys.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>