From: Felix Fietkau <nbd@nbd.name>
Subject: jffs2: use .rename2 and add RENAME_WHITEOUT support

It is required for renames on overlayfs

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---

--- a/fs/jffs2/dir.c
+++ b/fs/jffs2/dir.c
@@ -752,6 +752,24 @@ static int jffs2_mknod (struct inode *di
 	return ret;
 }
 
+static int jffs2_whiteout (struct inode *old_dir, struct dentry *old_dentry)
+{
+	struct dentry *wh;
+	int err;
+
+	wh = d_alloc(old_dentry->d_parent, &old_dentry->d_name);
+	if (!wh)
+		return -ENOMEM;
+
+	err = jffs2_mknod(old_dir, wh, S_IFCHR | WHITEOUT_MODE,
+			  WHITEOUT_DEV);
+	if (err)
+		return err;
+
+	d_rehash(wh);
+	return 0;
+}
+
 static int jffs2_rename (struct inode *old_dir_i, struct dentry *old_dentry,
 			 struct inode *new_dir_i, struct dentry *new_dentry,
 			 unsigned int flags)
@@ -762,7 +780,7 @@ static int jffs2_rename (struct inode *o
 	uint8_t type;
 	uint32_t now;
 
-	if (flags & ~RENAME_NOREPLACE)
+	if (flags & ~(RENAME_NOREPLACE|RENAME_WHITEOUT))
 		return -EINVAL;
 
 	/* The VFS will check for us and prevent trying to rename a
@@ -828,9 +846,14 @@ static int jffs2_rename (struct inode *o
 	if (d_is_dir(old_dentry) && !victim_f)
 		inc_nlink(new_dir_i);
 
-	/* Unlink the original */
-	ret = jffs2_do_unlink(c, JFFS2_INODE_INFO(old_dir_i),
-			      old_dentry->d_name.name, old_dentry->d_name.len, NULL, now);
+	if (flags & RENAME_WHITEOUT)
+		/* Replace with whiteout */
+		ret = jffs2_whiteout(old_dir_i, old_dentry);
+	else
+		/* Unlink the original */
+		ret = jffs2_do_unlink(c, JFFS2_INODE_INFO(old_dir_i),
+				      old_dentry->d_name.name,
+				      old_dentry->d_name.len, NULL, now);
 
 	/* We don't touch inode->i_nlink */