- We should never unlock a buf before we've cleared B_REMFREE. I believe

this is happening at the moment and sometimes causing panics later on the
   package cluster when we bremfree() a buf whose delayed bremfree() did not
   previously happen.

Sponsored by:	Isilon Systems, Inc.

sys/sys/buf.h

@@ -309,6 +309,8 @@ BUF_UNLOCK(struct buf *bp)
 	int s;
 
 	s = splbio();
+	KASSERT((bp->b_flags & B_REMFREE) == 0,
+	    ("BUF_UNLOCK %p while B_REMFREE is still set.", bp));
 	lockmgr(&(bp)->b_lock, LK_RELEASE, NULL, curthread);
 	splx(s);
 }