Re: [PATCH 4/5] SUNRPC: track when a client connection is routed to the local host.

[Anna Schumaker]

On 04/22/2014 10:40 PM, NeilBrown wrote:
> If requests are being sent to the local host, then NFS will
> need to take care to avoid deadlocks.
>
> So keep track when accepting a connection or sending a UDP request
> and set a flag in the svc_xprt when the peer connected to is local.
>
> The interface rpc_is_foreign() is provided to check is a given client
> is connected to a foreign server.  When it returns zero it is either
> not connected or connected to a local server and in either case
> greater care is needed.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
> ---
>  include/linux/sunrpc/clnt.h |    1 +
>  include/linux/sunrpc/xprt.h |    1 +
>  net/sunrpc/clnt.c           |   25 +++++++++++++++++++++++++
>  net/sunrpc/xprtsock.c       |   17 +++++++++++++++++
>  4 files changed, 44 insertions(+)
>
> diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
> index 8af2804bab16..5d626cc5ab01 100644
> --- a/include/linux/sunrpc/clnt.h
> +++ b/include/linux/sunrpc/clnt.h
> @@ -173,6 +173,7 @@ void		rpc_force_rebind(struct rpc_clnt *);
>  size_t		rpc_peeraddr(struct rpc_clnt *, struct sockaddr *, size_t);
>  const char	*rpc_peeraddr2str(struct rpc_clnt *, enum rpc_display_format_t);
>  int		rpc_localaddr(struct rpc_clnt *, struct sockaddr *, size_t);
> +int		rpc_is_foreign(struct rpc_clnt *);
>  
>  #endif /* __KERNEL__ */
>  #endif /* _LINUX_SUNRPC_CLNT_H */
> diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
> index 8097b9df6773..318ee37bc358 100644
> --- a/include/linux/sunrpc/xprt.h
> +++ b/include/linux/sunrpc/xprt.h
> @@ -340,6 +340,7 @@ int			xs_swapper(struct rpc_xprt *xprt, int enable);
>  #define XPRT_CONNECTION_ABORT	(7)
>  #define XPRT_CONNECTION_CLOSE	(8)
>  #define XPRT_CONGESTED		(9)
> +#define XPRT_LOCAL		(10)
>  
>  static inline void xprt_set_connected(struct rpc_xprt *xprt)
>  {
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index 0edada973434..454cea69b373 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -1109,6 +1109,31 @@ const char *rpc_peeraddr2str(struct rpc_clnt *clnt,
>  }
>  EXPORT_SYMBOL_GPL(rpc_peeraddr2str);
>  
> +/**
> + * rpc_is_foreign - report is rpc client was recently connected to
> + *                  remote host
> + * @clnt: RPC client structure
> + *
> + * If the client is not connected, or connected to the local host
> + * (any IP address), then return 0.  Only return non-zero if the
> + * most recent state was a connection to a remote host.
> + * For UDP the client always appears to be connected, and the
> + * remoteness of the host is of the destination of the last transmission.
> + */
> +int rpc_is_foreign(struct rpc_clnt *clnt)
> +{
> +	struct rpc_xprt *xprt;
> +	int conn_foreign;
> +
> +	rcu_read_lock();
> +	xprt = rcu_dereference(clnt->cl_xprt);
> +	conn_foreign = (xprt && xprt_connected(xprt)
> +			&& !test_bit(XPRT_LOCAL, &xprt->state));
> +	rcu_read_unlock();
> +	return conn_foreign;
> +}
> +EXPORT_SYMBOL_GPL(rpc_is_foreign);
> +
>  static const struct sockaddr_in rpc_inaddr_loopback = {
>  	.sin_family		= AF_INET,
>  	.sin_addr.s_addr	= htonl(INADDR_ANY),
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index 0addefca8e77..74796cf37d5b 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -642,6 +642,15 @@ static int xs_udp_send_request(struct rpc_task *task)
>  			xdr->len - req->rq_bytes_sent, status);
>  
>  	if (status >= 0) {
> +		struct dst_entry *dst;
> +		rcu_read_lock();
> +		dst = rcu_dereference(transport->sock->sk->sk_dst_cache);
> +		if (dst && dst->dev && (dst->dev->features & NETIF_F_LOOPBACK))
> +			set_bit(XPRT_LOCAL, &xprt->state);
> +		else
> +			clear_bit(XPRT_LOCAL, &xprt->state);
> +		rcu_read_unlock();
> +
You repeat this block of code a bit later.  Can you please make it an inline helper function?

Anna

>  		req->rq_xmit_bytes_sent += status;
>  		if (status >= req->rq_slen)
>  			return 0;
> @@ -1527,6 +1536,7 @@ static void xs_sock_mark_closed(struct rpc_xprt *xprt)
>  static void xs_tcp_state_change(struct sock *sk)
>  {
>  	struct rpc_xprt *xprt;
> +	struct dst_entry *dst;
>  
>  	read_lock_bh(&sk->sk_callback_lock);
>  	if (!(xprt = xprt_from_sock(sk)))
> @@ -1556,6 +1566,13 @@ static void xs_tcp_state_change(struct sock *sk)
>  
>  			xprt_wake_pending_tasks(xprt, -EAGAIN);
>  		}
> +		rcu_read_lock();
> +		dst = rcu_dereference(sk->sk_dst_cache);
> +		if (dst && dst->dev && (dst->dev->features & NETIF_F_LOOPBACK))
> +			set_bit(XPRT_LOCAL, &xprt->state);
> +		else
> +			clear_bit(XPRT_LOCAL, &xprt->state);
> +		rcu_read_unlock();
>  		spin_unlock(&xprt->transport_lock);
>  		break;
>  	case TCP_FIN_WAIT1:
>
>
> --
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