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>

fs/nfs/callback_proc.c

@@ -8,6 +8,7 @@
 #include <linux/nfs4.h>
 #include <linux/nfs_fs.h>
 #include <linux/slab.h>
+#include <linux/rcupdate.h>
 #include "nfs4_fs.h"
 #include "callback.h"
 #include "delegation.h"
@@ -33,7 +34,7 @@ __be32 nfs4_callback_getattr(struct cb_getattrargs *args,
 	res->bitmap[0] = res->bitmap[1] = 0;
 	res->status = htonl(NFS4ERR_BADHANDLE);
 
-	dprintk("NFS: GETATTR callback request from %s\n",
+	dprintk_rcu("NFS: GETATTR callback request from %s\n",
 		rpc_peeraddr2str(cps->clp->cl_rpcclient, RPC_DISPLAY_ADDR));
 
 	inode = nfs_delegation_find_inode(cps->clp, &args->fh);
@@ -73,7 +74,7 @@ __be32 nfs4_callback_recall(struct cb_recallargs *args, void *dummy,
 	if (!cps->clp) /* Always set for v4.0. Set in cb_sequence for v4.1 */
 		goto out;
 
-	dprintk("NFS: RECALL callback request from %s\n",
+	dprintk_rcu("NFS: RECALL callback request from %s\n",
 		rpc_peeraddr2str(cps->clp->cl_rpcclient, RPC_DISPLAY_ADDR));
 
 	res = htonl(NFS4ERR_BADHANDLE);
@@ -533,7 +534,7 @@ __be32 nfs4_callback_recallany(struct cb_recallanyargs *args, void *dummy,
 	if (!cps->clp) /* set in cb_sequence */
 		goto out;
 
-	dprintk("NFS: RECALL_ANY callback request from %s\n",
+	dprintk_rcu("NFS: RECALL_ANY callback request from %s\n",
 		rpc_peeraddr2str(cps->clp->cl_rpcclient, RPC_DISPLAY_ADDR));
 
 	status = cpu_to_be32(NFS4ERR_INVAL);
@@ -568,7 +569,7 @@ __be32 nfs4_callback_recallslot(struct cb_recallslotargs *args, void *dummy,
 	if (!cps->clp) /* set in cb_sequence */
 		goto out;
 
-	dprintk("NFS: CB_RECALL_SLOT request from %s target max slots %d\n",
+	dprintk_rcu("NFS: CB_RECALL_SLOT request from %s target max slots %d\n",
 		rpc_peeraddr2str(cps->clp->cl_rpcclient, RPC_DISPLAY_ADDR),
 		args->crsa_target_max_slots);
 

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;
 }
@@ -1993,13 +1997,15 @@ 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),
 		   rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_HEX_PORT),
 		   dev,
 		   fsid,
 		   nfs_server_fscache_state(server));
+	rcu_read_unlock();
 
 	return 0;
 }

fs/nfs/nfs4namespace.c

@@ -96,8 +96,8 @@ static int nfs4_validate_fspath(struct dentry *dentry,
 static size_t nfs_parse_server_name(char *string, size_t len,
 		struct sockaddr *sa, size_t salen, struct nfs_server *server)
 {
+	struct net *net = rpc_net_ns(server->client);
 	ssize_t ret;
-	struct net *net = server->client->cl_xprt->xprt_net;
 
 	ret = rpc_pton(net, string, len, sa, salen);
 	if (ret == 0) {

fs/nfs/nfs4proc.c

@@ -3833,6 +3833,7 @@ int nfs4_proc_setclientid(struct nfs_client *clp, u32 program,
 	*p = htonl((u32)clp->cl_boot_time.tv_nsec);
 
 	for(;;) {
+		rcu_read_lock();
 		setclientid.sc_name_len = scnprintf(setclientid.sc_name,
 				sizeof(setclientid.sc_name), "%s/%s %s %s %u",
 				clp->cl_ipaddr,
@@ -3849,6 +3850,7 @@ int nfs4_proc_setclientid(struct nfs_client *clp, u32 program,
 		setclientid.sc_uaddr_len = scnprintf(setclientid.sc_uaddr,
 				sizeof(setclientid.sc_uaddr), "%s.%u.%u",
 				clp->cl_ipaddr, port >> 8, port & 255);
+		rcu_read_unlock();
 
 		status = rpc_call_sync(clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
 		if (status != -NFS4ERR_CLID_INUSE)
@@ -5244,11 +5246,16 @@ struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp)
 
 void nfs4_destroy_session(struct nfs4_session *session)
 {
+	struct rpc_xprt *xprt;
+
 	nfs4_proc_destroy_session(session);
+
+	rcu_read_lock();
+	xprt = rcu_dereference(session->clp->cl_rpcclient->cl_xprt);
+	rcu_read_unlock();
 	dprintk("%s Destroy backchannel for xprt %p\n",
-		__func__, session->clp->cl_rpcclient->cl_xprt);
-	xprt_destroy_backchannel(session->clp->cl_rpcclient->cl_xprt,
-				NFS41_BC_MIN_CALLBACKS);
+		__func__, xprt);
+	xprt_destroy_backchannel(xprt, NFS41_BC_MIN_CALLBACKS);
 	nfs4_destroy_slot_tables(session);
 	kfree(session);
 }

fs/nfs/nfs4state.c

@@ -1037,19 +1037,28 @@ static void nfs4_clear_state_manager_bit(struct nfs_client *clp)
 void nfs4_schedule_state_manager(struct nfs_client *clp)
 {
 	struct task_struct *task;
+	char buf[INET6_ADDRSTRLEN + sizeof("-manager") + 1];
 
 	if (test_and_set_bit(NFS4CLNT_MANAGER_RUNNING, &clp->cl_state) != 0)
 		return;
 	__module_get(THIS_MODULE);
 	atomic_inc(&clp->cl_count);
-	task = kthread_run(nfs4_run_state_manager, clp, "%s-manager",
-				rpc_peeraddr2str(clp->cl_rpcclient,
-							RPC_DISPLAY_ADDR));
-	if (!IS_ERR(task))
-		return;
-	nfs4_clear_state_manager_bit(clp);
-	nfs_put_client(clp);
-	module_put(THIS_MODULE);
+
+	/* The rcu_read_lock() is not strictly necessary, as the state
+	 * manager is the only thread that ever changes the rpc_xprt
+	 * after it's initialized.  At this point, we're single threaded. */
+	rcu_read_lock();
+	snprintf(buf, sizeof(buf), "%s-manager",
+			rpc_peeraddr2str(clp->cl_rpcclient, RPC_DISPLAY_ADDR));
+	rcu_read_unlock();
+	task = kthread_run(nfs4_run_state_manager, clp, buf);
+	if (IS_ERR(task)) {
+		printk(KERN_ERR "%s: kthread_run: %ld\n",
+			__func__, PTR_ERR(task));
+		nfs4_clear_state_manager_bit(clp);
+		nfs_put_client(clp);
+		module_put(THIS_MODULE);
+	}
 }
 
 /*

fs/nfs/super.c

@@ -53,6 +53,7 @@
 #include <linux/magic.h>
 #include <linux/parser.h>
 #include <linux/nsproxy.h>
+#include <linux/rcupdate.h>
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
@@ -701,8 +702,10 @@ static void nfs_show_mount_options(struct seq_file *m, struct nfs_server *nfss,
 		else
 			seq_puts(m, nfs_infop->nostr);
 	}
+	rcu_read_lock();
 	seq_printf(m, ",proto=%s",
 		   rpc_peeraddr2str(nfss->client, RPC_DISPLAY_NETID));
+	rcu_read_unlock();
 	if (version == 4) {
 		if (nfss->port != NFS_PORT)
 			seq_printf(m, ",port=%u", nfss->port);
@@ -751,9 +754,11 @@ static int nfs_show_options(struct seq_file *m, struct dentry *root)
 
 	nfs_show_mount_options(m, nfss, 0);
 
+	rcu_read_lock();
 	seq_printf(m, ",addr=%s",
 			rpc_peeraddr2str(nfss->nfs_client->cl_rpcclient,
 							RPC_DISPLAY_ADDR));
+	rcu_read_unlock();
 
 	return 0;
 }

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);

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
 

net/sunrpc/auth_gss/auth_gss.c

@@ -799,7 +799,7 @@ static int gss_pipes_dentries_create(struct rpc_auth *auth)
 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;