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>
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 25c3da5..7783fc0 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 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_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)
{
+ 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 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 @@
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 @@
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 @@
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 @@
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_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 @@
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;
- bytes = sizeof(xprt->addr);
+ rcu_read_lock();
+ xprt = rcu_dereference(clnt->cl_xprt);
+
+ 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 @@
* @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 @@
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 @@
*/
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 @@
*/
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);