new helper: inode_wrong_type()

commit 6e3e2c4362 upstream.

inode_wrong_type(inode, mode) returns true if setting inode->i_mode
to given value would've changed the inode type.  We have enough of
those checks open-coded to make a helper worthwhile.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/overlayfs/namei.c

@@ -366,7 +366,7 @@ int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
 		return PTR_ERR(origin);
 
 	if (upperdentry && !ovl_is_whiteout(upperdentry) &&
-	    ((d_inode(origin)->i_mode ^ d_inode(upperdentry)->i_mode) & S_IFMT))
+	    inode_wrong_type(d_inode(upperdentry), d_inode(origin)->i_mode))
 		goto invalid;
 
 	if (!*stackp)
@@ -724,7 +724,7 @@ struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
 		index = ERR_PTR(-ESTALE);
 		goto out;
 	} else if (ovl_dentry_weird(index) || ovl_is_whiteout(index) ||
-		   ((inode->i_mode ^ d_inode(origin)->i_mode) & S_IFMT)) {
+		   inode_wrong_type(inode, d_inode(origin)->i_mode)) {
 		/*
 		 * Index should always be of the same file type as origin
 		 * except for the case of a whiteout index. A whiteout