On Wed, 23 Apr 2014 09:44:12 -0400 Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
wrote:
> 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?
Thanks for the suggestion.
I've put
static inline int sock_is_loopback(struct sock *sk)
{
struct dst_entry *dst;
int loopback = 0;
rcu_read_lock();
dst = rcu_dereference(sk->sk_dst_cache);
if (dst && dst->dev &&
(dst->dev->features & NETIF_F_LOOPBACK))
loopback = 1;
rcu_read_unlock();
return loopback;
}
in sunrpc.h, and used it for both the server-side and the client side.
NeilBrown
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