SUNRPC: Use RCU to dereference the rpc_clnt.cl_xprt field

A migration event will replace the rpc_xprt used by an rpc_clnt.  To
ensure this can be done safely, all references to cl_xprt must now use
a form of rcu_dereference().

Special care is taken with rpc_peeraddr2str(), which returns a pointer
to memory whose lifetime is the same as the rpc_xprt.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
[ cel: fix lockdep splats and layering violations ]
[ cel: forward ported to 3.4 ]
[ cel: remove rpc_max_reqs(), add rpc_net_ns() ]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 16 insertions, 1 deletions

diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index a4c62e95c720..e3d12b4a0314 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -35,7 +35,7 @@ struct rpc_clnt {
         struct list_head        cl_clients;     /* Global list of clients */
         struct list_head        cl_tasks;       /* List of tasks */
         spinlock_t              cl_lock;        /* spinlock */
-        struct rpc_xprt *       cl_xprt;        /* transport */
+        struct rpc_xprt __rcu * cl_xprt;        /* transport */
         struct rpc_procinfo *   cl_procinfo;    /* procedure info */
         u32                     cl_prog,        /* RPC program number */
                                 cl_vers,        /* RPC version number */
@@ -156,6 +156,8 @@ struct rpc_task *rpc_call_null(struct rpc_clnt *clnt, struct rpc_cred *cred,
 int             rpc_restart_call_prepare(struct rpc_task *);
 int             rpc_restart_call(struct rpc_task *);
 void            rpc_setbufsize(struct rpc_clnt *, unsigned int, unsigned int);
+int             rpc_protocol(struct rpc_clnt *);
+struct net *    rpc_net_ns(struct rpc_clnt *);
 size_t          rpc_max_payload(struct rpc_clnt *);
 void            rpc_force_rebind(struct rpc_clnt *);
 size_t          rpc_peeraddr(struct rpc_clnt *, struct sockaddr *, size_t);
diff --git a/include/linux/sunrpc/debug.h b/include/linux/sunrpc/debug.h
index b506936f4ce6..6cb2517bcf75 100644
--- a/include/linux/sunrpc/debug.h
+++ b/include/linux/sunrpc/debug.h
@@ -50,19 +50,32 @@ extern unsigned int		nlm_debug;
 #endif
 
 #define dprintk(args...)        dfprintk(FACILITY, ## args)
+#define dprintk_rcu(args...)    dfprintk_rcu(FACILITY, ## args)
 
 #undef ifdebug
 #ifdef RPC_DEBUG                        
 # define ifdebug(fac)           if (unlikely(rpc_debug & RPCDBG_##fac))
+
 # define dfprintk(fac, args...) \
         do { \
                 ifdebug(fac) \
                         printk(KERN_DEFAULT args); \
         } while (0)
+
+# define dfprintk_rcu(fac, args...)     \
+        do { \
+                ifdebug(fac) { \
+                        rcu_read_lock(); \
+                        printk(KERN_DEFAULT args); \
+                        rcu_read_unlock(); \
+                } \
+        } while (0)
+
 # define RPC_IFDEBUG(x)         x
 #else
 # define ifdebug(fac)           if (0)
 # define dfprintk(fac, args...) do ; while (0)
+# define dfprintk_rcu(fac, args...)     do ; while (0)
 # define RPC_IFDEBUG(x)
 #endif