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>

1 files changed, 11 insertions, 5 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 1506adf4d4ed..d038dc5916e5 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -1284,16 +1284,18 @@ static int nfs4_init_callback(struct nfs_client *clp)
         int error;
 
         if (clp->rpc_ops->version == 4) {
+                struct rpc_xprt *xprt;
+
+                xprt = rcu_dereference_raw(clp->cl_rpcclient->cl_xprt);
+
                 if (nfs4_has_session(clp)) {
-                        error = xprt_setup_backchannel(
-                                                clp->cl_rpcclient->cl_xprt,
+                        error = xprt_setup_backchannel(xprt,
                                                 NFS41_BC_MIN_CALLBACKS);
                         if (error < 0)
                                 return error;
                 }
 
-                error = nfs_callback_up(clp->cl_mvops->minor_version,
-                                        clp->cl_rpcclient->cl_xprt);
+                error = nfs_callback_up(clp->cl_mvops->minor_version, xprt);
                 if (error < 0) {
                         dprintk("%s: failed to start callback. Error = %d\n",
                                 __func__, error);
@@ -1678,7 +1680,7 @@ struct nfs_server *nfs4_create_referral_server(struct nfs_clone_mount *data,
                                 data->addrlen,
                                 parent_client->cl_ipaddr,
                                 data->authflavor,
-                                parent_server->client->cl_xprt->prot,
+                                rpc_protocol(parent_server->client),
                                 parent_server->client->cl_timeout,
                                 parent_client->cl_mvops->minor_version,
                                 parent_client->net);
@@ -1905,12 +1907,14 @@ static int nfs_server_list_show(struct seq_file *m, void *v)
         if (clp->cl_cons_state != NFS_CS_READY)
                 return 0;
 
+        rcu_read_lock();
         seq_printf(m, "v%u %s %s %3d %s\n",
                    clp->rpc_ops->version,
                    rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_ADDR),
                    rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_PORT),
                    atomic_read(&clp->cl_count),
                    clp->cl_hostname);
+        rcu_read_unlock();
 
         return 0;
 }
@@ -1993,6 +1997,7 @@ static int nfs_volume_list_show(struct seq_file *m, void *v)
                  (unsigned long long) server->fsid.major,
                  (unsigned long long) server->fsid.minor);
 
+        rcu_read_lock();
         seq_printf(m, "v%u %s %s %-7s %-17s %s\n",
                    clp->rpc_ops->version,
                    rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_ADDR),
@@ -2000,6 +2005,7 @@ static int nfs_volume_list_show(struct seq_file *m, void *v)
                    dev,
                    fsid,
                    nfs_server_fscache_state(server));
+        rcu_read_unlock();
 
         return 0;
 }