new helper: ihold()

Clones an existing reference to inode; caller must already hold one.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

net/socket.c

@@ -377,7 +377,7 @@ static int sock_alloc_file(struct socket *sock, struct file **f, int flags)
 		  &socket_file_ops);
 	if (unlikely(!file)) {
 		/* drop dentry, keep inode */
-		atomic_inc(&path.dentry->d_inode->i_count);
+		ihold(path.dentry->d_inode);
 		path_put(&path);
 		put_unused_fd(fd);
 		return -ENFILE;