Re: [net-next PATCH 5/5] epoll: Add busy poll support to epoll with socket fds.

On Thu, 2017-03-16 at 11:33 -0700, Alexander Duyck wrote:

From: Sridhar Samudrala <sridhar.samudrala@intel.com>

+/*
+ * If busy polling is on and the file is a socket, return a pointer to
+ * struct sock
+ */
+static inline struct sock *ep_sk_from_file(struct file *file)
+{
+	struct inode *inode = file_inode(file);
+
+	if (!S_ISSOCK(inode->i_mode))
+		return NULL;
+
+	return ((struct socket *)file->private_data)->sk;
+}

I believe a more standard way is to use sock_from_file()

(This does not have to fetch a cache line to read i_mode ))