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>

5 files changed, 110 insertions, 28 deletions

diff --git a/net/sunrpc/auth_gss/auth_gss.c b/net/sunrpc/auth_gss/auth_gss.c
index cb2e56452748..d3ad81f8da5b 100644
--- a/net/sunrpc/auth_gss/auth_gss.c
+++ b/net/sunrpc/auth_gss/auth_gss.c
@@ -799,7 +799,7 @@ err_unlink_pipe_1:
 static void gss_pipes_dentries_destroy_net(struct rpc_clnt *clnt,
                                            struct rpc_auth *auth)
 {
-        struct net *net = clnt->cl_xprt->xprt_net;
+        struct net *net = rpc_net_ns(clnt);
         struct super_block *sb;
 
         sb = rpc_get_sb_net(net);
@@ -813,7 +813,7 @@ static void gss_pipes_dentries_destroy_net(struct rpc_clnt *clnt,
 static int gss_pipes_dentries_create_net(struct rpc_clnt *clnt,
                                          struct rpc_auth *auth)
 {
-        struct net *net = clnt->cl_xprt->xprt_net;
+        struct net *net = rpc_net_ns(clnt);
         struct super_block *sb;
         int err = 0;
 
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 25c3da53fb69..7783fc0e7263 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -31,6 +31,7 @@
 #include <linux/in.h>
 #include <linux/in6.h>
 #include <linux/un.h>
+#include <linux/rcupdate.h>
 
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/rpc_pipe_fs.h>
@@ -81,7 +82,8 @@ static int	rpc_ping(struct rpc_clnt *clnt);
 
 static void rpc_register_client(struct rpc_clnt *clnt)
 {
-        struct sunrpc_net *sn = net_generic(clnt->cl_xprt->xprt_net, sunrpc_net_id);
+        struct net *net = rpc_net_ns(clnt);
+        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
 
         spin_lock(&sn->rpc_client_lock);
         list_add(&clnt->cl_clients, &sn->all_clients);
@@ -90,7 +92,8 @@ static void rpc_register_client(struct rpc_clnt *clnt)
 
 static void rpc_unregister_client(struct rpc_clnt *clnt)
 {
-        struct sunrpc_net *sn = net_generic(clnt->cl_xprt->xprt_net, sunrpc_net_id);
+        struct net *net = rpc_net_ns(clnt);
+        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
 
         spin_lock(&sn->rpc_client_lock);
         list_del(&clnt->cl_clients);
@@ -109,12 +112,13 @@ static void __rpc_clnt_remove_pipedir(struct rpc_clnt *clnt)
 
 static void rpc_clnt_remove_pipedir(struct rpc_clnt *clnt)
 {
+        struct net *net = rpc_net_ns(clnt);
         struct super_block *pipefs_sb;
 
-        pipefs_sb = rpc_get_sb_net(clnt->cl_xprt->xprt_net);
+        pipefs_sb = rpc_get_sb_net(net);
         if (pipefs_sb) {
                 __rpc_clnt_remove_pipedir(clnt);
-                rpc_put_sb_net(clnt->cl_xprt->xprt_net);
+                rpc_put_sb_net(net);
         }
 }
 
@@ -155,17 +159,18 @@ static struct dentry *rpc_setup_pipedir_sb(struct super_block *sb,
 static int
 rpc_setup_pipedir(struct rpc_clnt *clnt, const char *dir_name)
 {
+        struct net *net = rpc_net_ns(clnt);
         struct super_block *pipefs_sb;
         struct dentry *dentry;
 
         clnt->cl_dentry = NULL;
         if (dir_name == NULL)
                 return 0;
-        pipefs_sb = rpc_get_sb_net(clnt->cl_xprt->xprt_net);
+        pipefs_sb = rpc_get_sb_net(net);
         if (!pipefs_sb)
                 return 0;
         dentry = rpc_setup_pipedir_sb(pipefs_sb, clnt, dir_name);
-        rpc_put_sb_net(clnt->cl_xprt->xprt_net);
+        rpc_put_sb_net(net);
         if (IS_ERR(dentry))
                 return PTR_ERR(dentry);
         clnt->cl_dentry = dentry;
@@ -295,7 +300,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
         if (clnt->cl_server == NULL)
                 goto out_no_server;
 
-        clnt->cl_xprt     = xprt;
+        rcu_assign_pointer(clnt->cl_xprt, xprt);
         clnt->cl_procinfo = version->procs;
         clnt->cl_maxproc  = version->nrprocs;
         clnt->cl_protname = program->name;
@@ -310,7 +315,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
         INIT_LIST_HEAD(&clnt->cl_tasks);
         spin_lock_init(&clnt->cl_lock);
 
-        if (!xprt_bound(clnt->cl_xprt))
+        if (!xprt_bound(xprt))
                 clnt->cl_autobind = 1;
 
         clnt->cl_timeout = xprt->timeout;
@@ -477,6 +482,7 @@ struct rpc_clnt *
 rpc_clone_client(struct rpc_clnt *clnt)
 {
         struct rpc_clnt *new;
+        struct rpc_xprt *xprt;
         int err = -ENOMEM;
 
         new = kmemdup(clnt, sizeof(*new), GFP_KERNEL);
@@ -499,18 +505,25 @@ rpc_clone_client(struct rpc_clnt *clnt)
                 if (new->cl_principal == NULL)
                         goto out_no_principal;
         }
+        rcu_read_lock();
+        xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
+        rcu_read_unlock();
+        if (xprt == NULL)
+                goto out_no_transport;
+        rcu_assign_pointer(new->cl_xprt, xprt);
         atomic_set(&new->cl_count, 1);
         err = rpc_setup_pipedir(new, clnt->cl_program->pipe_dir_name);
         if (err != 0)
                 goto out_no_path;
         if (new->cl_auth)
                 atomic_inc(&new->cl_auth->au_count);
-        xprt_get(clnt->cl_xprt);
         atomic_inc(&clnt->cl_count);
         rpc_register_client(new);
         rpciod_up();
         return new;
 out_no_path:
+        xprt_put(xprt);
+out_no_transport:
         kfree(new->cl_principal);
 out_no_principal:
         rpc_free_iostats(new->cl_metrics);
@@ -590,7 +603,7 @@ rpc_free_client(struct rpc_clnt *clnt)
         rpc_free_iostats(clnt->cl_metrics);
         kfree(clnt->cl_principal);
         clnt->cl_metrics = NULL;
-        xprt_put(clnt->cl_xprt);
+        xprt_put(rcu_dereference_raw(clnt->cl_xprt));
         rpciod_down();
         kfree(clnt);
 }
@@ -879,13 +892,18 @@ EXPORT_SYMBOL_GPL(rpc_call_start);
 size_t rpc_peeraddr(struct rpc_clnt *clnt, struct sockaddr *buf, size_t bufsize)
 {
         size_t bytes;
-        struct rpc_xprt *xprt = clnt->cl_xprt;
+        struct rpc_xprt *xprt;
+
+        rcu_read_lock();
+        xprt = rcu_dereference(clnt->cl_xprt);
 
-        bytes = sizeof(xprt->addr);
+        bytes = xprt->addrlen;
         if (bytes > bufsize)
                 bytes = bufsize;
-        memcpy(buf, &clnt->cl_xprt->addr, bytes);
-        return xprt->addrlen;
+        memcpy(buf, &xprt->addr, bytes);
+        rcu_read_unlock();
+
+        return bytes;
 }
 EXPORT_SYMBOL_GPL(rpc_peeraddr);
 
@@ -894,11 +912,16 @@ EXPORT_SYMBOL_GPL(rpc_peeraddr);
  * @clnt: RPC client structure
  * @format: address format
  *
+ * NB: the lifetime of the memory referenced by the returned pointer is
+ * the same as the rpc_xprt itself.  As long as the caller uses this
+ * pointer, it must hold the RCU read lock.
  */
 const char *rpc_peeraddr2str(struct rpc_clnt *clnt,
                              enum rpc_display_format_t format)
 {
-        struct rpc_xprt *xprt = clnt->cl_xprt;
+        struct rpc_xprt *xprt;
+
+        xprt = rcu_dereference(clnt->cl_xprt);
 
         if (xprt->address_strings[format] != NULL)
                 return xprt->address_strings[format];
@@ -910,14 +933,51 @@ EXPORT_SYMBOL_GPL(rpc_peeraddr2str);
 void
 rpc_setbufsize(struct rpc_clnt *clnt, unsigned int sndsize, unsigned int rcvsize)
 {
-        struct rpc_xprt *xprt = clnt->cl_xprt;
+        struct rpc_xprt *xprt;
+
+        rcu_read_lock();
+        xprt = rcu_dereference(clnt->cl_xprt);
         if (xprt->ops->set_buffer_size)
                 xprt->ops->set_buffer_size(xprt, sndsize, rcvsize);
+        rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(rpc_setbufsize);
 
-/*
- * Return size of largest payload RPC client can support, in bytes
+/**
+ * rpc_protocol - Get transport protocol number for an RPC client
+ * @clnt: RPC client to query
+ *
+ */
+int rpc_protocol(struct rpc_clnt *clnt)
+{
+        int protocol;
+
+        rcu_read_lock();
+        protocol = rcu_dereference(clnt->cl_xprt)->prot;
+        rcu_read_unlock();
+        return protocol;
+}
+EXPORT_SYMBOL_GPL(rpc_protocol);
+
+/**
+ * rpc_net_ns - Get the network namespace for this RPC client
+ * @clnt: RPC client to query
+ *
+ */
+struct net *rpc_net_ns(struct rpc_clnt *clnt)
+{
+        struct net *ret;
+
+        rcu_read_lock();
+        ret = rcu_dereference(clnt->cl_xprt)->xprt_net;
+        rcu_read_unlock();
+        return ret;
+}
+EXPORT_SYMBOL_GPL(rpc_net_ns);
+
+/**
+ * rpc_max_payload - Get maximum payload size for a transport, in bytes
+ * @clnt: RPC client to query
  *
  * For stream transports, this is one RPC record fragment (see RFC
  * 1831), as we don't support multi-record requests yet.  For datagram
@@ -926,7 +986,12 @@ EXPORT_SYMBOL_GPL(rpc_setbufsize);
  */
 size_t rpc_max_payload(struct rpc_clnt *clnt)
 {
-        return clnt->cl_xprt->max_payload;
+        size_t ret;
+
+        rcu_read_lock();
+        ret = rcu_dereference(clnt->cl_xprt)->max_payload;
+        rcu_read_unlock();
+        return ret;
 }
 EXPORT_SYMBOL_GPL(rpc_max_payload);
 
@@ -937,8 +1002,11 @@ EXPORT_SYMBOL_GPL(rpc_max_payload);
  */
 void rpc_force_rebind(struct rpc_clnt *clnt)
 {
-        if (clnt->cl_autobind)
-                xprt_clear_bound(clnt->cl_xprt);
+        if (clnt->cl_autobind) {
+                rcu_read_lock();
+                xprt_clear_bound(rcu_dereference(clnt->cl_xprt));
+                rcu_read_unlock();
+        }
 }
 EXPORT_SYMBOL_GPL(rpc_force_rebind);
 
diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index ac9ee1590739..3d30943ed6db 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -16,6 +16,7 @@
 #include <linux/namei.h>
 #include <linux/fsnotify.h>
 #include <linux/kernel.h>
+#include <linux/rcupdate.h>
 
 #include <asm/ioctls.h>
 #include <linux/poll.h>
@@ -402,12 +403,14 @@ rpc_show_info(struct seq_file *m, void *v)
 {
         struct rpc_clnt *clnt = m->private;
 
+        rcu_read_lock();
         seq_printf(m, "RPC server: %s\n", clnt->cl_server);
         seq_printf(m, "service: %s (%d) version %d\n", clnt->cl_protname,
                         clnt->cl_prog, clnt->cl_vers);
         seq_printf(m, "address: %s\n", rpc_peeraddr2str(clnt, RPC_DISPLAY_ADDR));
         seq_printf(m, "protocol: %s\n", rpc_peeraddr2str(clnt, RPC_DISPLAY_PROTO));
         seq_printf(m, "port: %s\n", rpc_peeraddr2str(clnt, RPC_DISPLAY_PORT));
+        rcu_read_unlock();
         return 0;
 }
 
diff --git a/net/sunrpc/rpcb_clnt.c b/net/sunrpc/rpcb_clnt.c
index b1f08bd67883..4f8af63798a2 100644
--- a/net/sunrpc/rpcb_clnt.c
+++ b/net/sunrpc/rpcb_clnt.c
@@ -620,9 +620,10 @@ static struct rpc_task *rpcb_call_async(struct rpc_clnt *rpcb_clnt, struct rpcbi
 static struct rpc_clnt *rpcb_find_transport_owner(struct rpc_clnt *clnt)
 {
         struct rpc_clnt *parent = clnt->cl_parent;
+        struct rpc_xprt *xprt = rcu_dereference(clnt->cl_xprt);
 
         while (parent != clnt) {
-                if (parent->cl_xprt != clnt->cl_xprt)
+                if (rcu_dereference(parent->cl_xprt) != xprt)
                         break;
                 if (clnt->cl_autobind)
                         break;
@@ -653,8 +654,12 @@ void rpcb_getport_async(struct rpc_task *task)
         size_t salen;
         int status;
 
-        clnt = rpcb_find_transport_owner(task->tk_client);
-        xprt = clnt->cl_xprt;
+        rcu_read_lock();
+        do {
+                clnt = rpcb_find_transport_owner(task->tk_client);
+                xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
+        } while (xprt == NULL);
+        rcu_read_unlock();
 
         dprintk("RPC: %5u %s(%s, %u, %u, %d)\n",
                 task->tk_pid, __func__,
@@ -667,6 +672,7 @@ void rpcb_getport_async(struct rpc_task *task)
         if (xprt_test_and_set_binding(xprt)) {
                 dprintk("RPC: %5u %s: waiting for another binder\n",
                         task->tk_pid, __func__);
+                xprt_put(xprt);
                 return;
         }
 
@@ -734,7 +740,7 @@ void rpcb_getport_async(struct rpc_task *task)
         switch (bind_version) {
         case RPCBVERS_4:
         case RPCBVERS_3:
-                map->r_netid = rpc_peeraddr2str(clnt, RPC_DISPLAY_NETID);
+                map->r_netid = xprt->address_strings[RPC_DISPLAY_NETID];
                 map->r_addr = rpc_sockaddr2uaddr(sap, GFP_ATOMIC);
                 map->r_owner = "";
                 break;
@@ -763,6 +769,7 @@ bailout_release_client:
 bailout_nofree:
         rpcb_wake_rpcbind_waiters(xprt, status);
         task->tk_status = status;
+        xprt_put(xprt);
 }
 EXPORT_SYMBOL_GPL(rpcb_getport_async);
 
diff --git a/net/sunrpc/stats.c b/net/sunrpc/stats.c
index 1eb3304bc105..bc2068ee795b 100644
--- a/net/sunrpc/stats.c
+++ b/net/sunrpc/stats.c
@@ -22,6 +22,7 @@
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/svcsock.h>
 #include <linux/sunrpc/metrics.h>
+#include <linux/rcupdate.h>
 
 #include "netns.h"
 
@@ -179,7 +180,7 @@ static void _print_name(struct seq_file *seq, unsigned int op,
 void rpc_print_iostats(struct seq_file *seq, struct rpc_clnt *clnt)
 {
         struct rpc_iostats *stats = clnt->cl_metrics;
-        struct rpc_xprt *xprt = clnt->cl_xprt;
+        struct rpc_xprt *xprt;
         unsigned int op, maxproc = clnt->cl_maxproc;
 
         if (!stats)
@@ -189,8 +190,11 @@ void rpc_print_iostats(struct seq_file *seq, struct rpc_clnt *clnt)
         seq_printf(seq, "p/v: %u/%u (%s)\n",
                         clnt->cl_prog, clnt->cl_vers, clnt->cl_protname);
 
+        rcu_read_lock();
+        xprt = rcu_dereference(clnt->cl_xprt);
         if (xprt)
                 xprt->ops->print_stats(xprt, seq);
+        rcu_read_unlock();
 
         seq_printf(seq, "\tper-op statistics\n");
         for (op = 0; op < maxproc; op++) {