[JFFS2] Track parent inode for directories (for NFS export)

To support NFS export, we need to know the parent inode of directories.
Rather than growing the jffs2_inode_cache structure, share space with
the nlink field -- which was always set to 1 for directories anyway.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/fs/jffs2/gc.c b/fs/jffs2/gc.c
index d4db0ef..090c556 100644
--- a/fs/jffs2/gc.c
+++ b/fs/jffs2/gc.c
@@ -161,8 +161,8 @@
 			continue;
 		}
 
-		if (!ic->nlink) {
-			D1(printk(KERN_DEBUG "Skipping check of ino #%d with nlink zero\n",
+		if (!ic->pino_nlink) {
+			D1(printk(KERN_DEBUG "Skipping check of ino #%d with nlink/pino zero\n",
 				  ic->ino));
 			spin_unlock(&c->inocache_lock);
 			jffs2_xattr_delete_inode(c, ic);
@@ -398,7 +398,7 @@
 	   it's vaguely possible. */
 
 	inum = ic->ino;
-	nlink = ic->nlink;
+	nlink = ic->pino_nlink;
 	spin_unlock(&c->inocache_lock);
 
 	f = jffs2_gc_fetch_inode(c, inum, !nlink);