[JFFS2] Add some preemptive BUG checks for XATTR code

In a couple of places, we assume that what's at the end of the
->next_in_ino list is a struct jffs2_inode_cache. Let's check
for that, since we expect it to change soon.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

fs/jffs2/erase.c

@@ -230,6 +230,7 @@ static inline void jffs2_remove_node_refs_from_ino_list(struct jffs2_sb_info *c,
 			   at the end of the linked list. Stash it and continue
 			   from the beginning of the list */
 			ic = (struct jffs2_inode_cache *)(*prev);
+			BUG_ON(ic->class != RAWNODE_CLASS_INODE_CACHE);
 			prev = &ic->nodes;
 			continue;
 		}

fs/jffs2/nodemgmt.c

@@ -661,6 +661,10 @@ void jffs2_mark_node_obsolete(struct jffs2_sb_info *c, struct jffs2_raw_node_ref
 		spin_lock(&c->erase_completion_lock);
 
 		ic = jffs2_raw_ref_to_ic(ref);
+		/* It seems we should never call jffs2_mark_node_obsolete() for
+		   XATTR nodes.... yet. Make sure we notice if/when we change
+		   that :) */
+		BUG_ON(ic->class != RAWNODE_CLASS_INODE_CACHE);
 		for (p = &ic->nodes; (*p) != ref; p = &((*p)->next_in_ino))
 			;