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

[Eric Dumazet]

On Thu, 2017-03-16 at 11:33 -0700, Alexander Duyck wrote:
> From: Sridhar Samudrala <sridhar.samudrala@xxxxxxxxx>

> +/*
> + * 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 ))