[JFFS2] Introduce jffs2_link_node_ref() function to reduce code duplication

The same sequence of code was repeated in many places, to add a new
struct jffs2_raw_node_ref to an eraseblock and adjust the space accounting
accordingly. Move it out-of-line.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/fs/jffs2/nodemgmt.c b/fs/jffs2/nodemgmt.c
index 0e1f58a..d6eab1b 100644
--- a/fs/jffs2/nodemgmt.c
+++ b/fs/jffs2/nodemgmt.c
@@ -403,21 +403,7 @@
 #endif
 	spin_lock(&c->erase_completion_lock);
 
-	if (!jeb->first_node)
-		jeb->first_node = new;
-	if (jeb->last_node)
-		jeb->last_node->next_phys = new;
-	jeb->last_node = new;
-
-	jeb->free_size -= len;
-	c->free_size -= len;
-	if (ref_obsolete(new)) {
-		jeb->dirty_size += len;
-		c->dirty_size += len;
-	} else {
-		jeb->used_size += len;
-		c->used_size += len;
-	}
+	jffs2_link_node_ref(c, jeb, new, len);
 
 	if (!jeb->free_size && !jeb->dirty_size && !ISDIRTY(jeb->wasted_size)) {
 		/* If it lives on the dirty_list, jffs2_reserve_space will put it there */