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Date: Thu, 24 Apr 2014 08:46:16 -0400
From: Anna Schumaker <Anna.Schumaker@...app.com>
To: NeilBrown <neilb@...e.de>
CC: Jan Kara <jack@...e.cz>, Jeff Layton <jlayton@...hat.com>,
Trond Myklebust <trond.myklebust@...marydata.com>,
Dave Chinner <david@...morbit.com>,
"J. Bruce Fields" <bfields@...ldses.org>,
Mel Gorman <mgorman@...e.com>,
"Andrew Morton" <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
<linux-nfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] SUNRPC: track when a client connection is routed
to the local host.
On 04/23/2014 07:14 PM, NeilBrown wrote:
> On Wed, 23 Apr 2014 09:44:12 -0400 Anna Schumaker <Anna.Schumaker@...app.com>
> 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@...e.de>
>>> ---
>>> 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.
Awesome, thanks!
Anna
>
> NeilBrown
>
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