[JFFS2] When retiring nextblock, allocate a node_ref for the wasted space

Failing to do so makes the calculated length of the last node incorrect,
when we're not using eraseblock summaries.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

fs/jffs2/nodemgmt.c

@@ -317,6 +317,8 @@ static int jffs2_do_reserve_space(struct jffs2_sb_info *c, uint32_t minsize,
 		}
 	} else {
 		if (jeb && minsize > jeb->free_size) {
+			uint32_t waste;
+
 			/* Skip the end of this block and file it as having some dirty space */
 			/* If there's a pending write to it, flush now */
 
@@ -329,10 +331,26 @@ static int jffs2_do_reserve_space(struct jffs2_sb_info *c, uint32_t minsize,
 				goto restart;
 			}
 
-			c->wasted_size += jeb->free_size;
-			c->free_size -= jeb->free_size;
-			jeb->wasted_size += jeb->free_size;
-			jeb->free_size = 0;
+			spin_unlock(&c->erase_completion_lock);
+
+			ret = jffs2_prealloc_raw_node_refs(c, jeb, 1);
+			if (ret)
+				return ret;
+			/* Just lock it again and continue. Nothing much can change because
+			   we hold c->alloc_sem anyway. In fact, it's not entirely clear why
+			   we hold c->erase_completion_lock in the majority of this function...
+			   but that's a question for another (more caffeine-rich) day. */
+			spin_lock(&c->erase_completion_lock);
+
+			waste = jeb->free_size;
+			jffs2_link_node_ref(c, jeb,
+					    (jeb->offset + c->sector_size - waste) | REF_OBSOLETE,
+					    waste, NULL);
+			/* FIXME: that made it count as dirty. Convert to wasted */
+			jeb->dirty_size -= waste;
+			c->dirty_size -= waste;
+			jeb->wasted_size += waste;
+			c->wasted_size += waste;
 
 			jffs2_close_nextblock(c, jeb);
 			jeb = NULL;