nfsd: expose /proc/net/sunrpc/nfsd in net namespaces

We are running nfsd servers inside of containers with their own network
namespace, and we want to monitor these services using the stats found
in /proc.  However these are not exposed in the proc inside of the
container, so we have to bind mount the host /proc into our containers
to get at this information.

Separate out the stat counters init and the proc registration, and move
the proc registration into the pernet operations entry and exit points
so that these stats can be exposed inside of network namespaces.

This is an intermediate step, this just exposes the global counters in
the network namespace.  Subsequent patches will move these counters into
the per-network namespace container.
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfsctl.c

@@ -1679,6 +1679,7 @@ static __net_init int nfsd_net_init(struct net *net)
 	nfsd4_init_leases_net(nn);
 	get_random_bytes(&nn->siphash_key, sizeof(nn->siphash_key));
 	seqlock_init(&nn->writeverf_lock);
+	nfsd_proc_stat_init(net);
 
 	return 0;
 
@@ -1699,6 +1700,7 @@ static __net_exit void nfsd_net_exit(struct net *net)
 {
 	struct nfsd_net *nn = net_generic(net, nfsd_net_id);
 
+	nfsd_proc_stat_shutdown(net);
 	nfsd_net_reply_cache_destroy(nn);
 	nfsd_idmap_shutdown(net);
 	nfsd_export_shutdown(net);
@@ -1722,7 +1724,7 @@ static int __init init_nfsd(void)
 	retval = nfsd4_init_pnfs();
 	if (retval)
 		goto out_free_slabs;
-	retval = nfsd_stat_init();	/* Statistics */
+	retval = nfsd_stat_counters_init();	/* Statistics */
 	if (retval)
 		goto out_free_pnfs;
 	retval = nfsd_drc_slab_create();
@@ -1762,7 +1764,7 @@ static int __init init_nfsd(void)
 	nfsd_lockd_shutdown();
 	nfsd_drc_slab_free();
 out_free_stat:
-	nfsd_stat_shutdown();
+	nfsd_stat_counters_destroy();
 out_free_pnfs:
 	nfsd4_exit_pnfs();
 out_free_slabs:
@@ -1780,7 +1782,7 @@ static void __exit exit_nfsd(void)
 	nfsd_drc_slab_free();
 	remove_proc_entry("fs/nfs/exports", NULL);
 	remove_proc_entry("fs/nfs", NULL);
-	nfsd_stat_shutdown();
+	nfsd_stat_counters_destroy();
 	nfsd_lockd_shutdown();
 	nfsd4_free_slabs();
 	nfsd4_exit_pnfs();

fs/nfsd/stats.c

@@ -108,31 +108,22 @@ void nfsd_percpu_counters_destroy(struct percpu_counter counters[], int num)
 		percpu_counter_destroy(&counters[i]);
 }
 
-static int nfsd_stat_counters_init(void)
+int nfsd_stat_counters_init(void)
 {
 	return nfsd_percpu_counters_init(nfsdstats.counter, NFSD_STATS_COUNTERS_NUM);
 }
 
-static void nfsd_stat_counters_destroy(void)
+void nfsd_stat_counters_destroy(void)
 {
 	nfsd_percpu_counters_destroy(nfsdstats.counter, NFSD_STATS_COUNTERS_NUM);
 }
 
-int nfsd_stat_init(void)
+void nfsd_proc_stat_init(struct net *net)
 {
-	int err;
-
-	err = nfsd_stat_counters_init();
-	if (err)
-		return err;
-
-	svc_proc_register(&init_net, &nfsd_svcstats, &nfsd_proc_ops);
-
-	return 0;
+	svc_proc_register(net, &nfsd_svcstats, &nfsd_proc_ops);
 }
 
-void nfsd_stat_shutdown(void)
+void nfsd_proc_stat_shutdown(struct net *net)
 {
-	nfsd_stat_counters_destroy();
-	svc_proc_unregister(&init_net, "nfsd");
+	svc_proc_unregister(net, "nfsd");
 }

fs/nfsd/stats.h

@@ -40,8 +40,10 @@ extern struct svc_stat		nfsd_svcstats;
 int nfsd_percpu_counters_init(struct percpu_counter *counters, int num);
 void nfsd_percpu_counters_reset(struct percpu_counter *counters, int num);
 void nfsd_percpu_counters_destroy(struct percpu_counter *counters, int num);
-int nfsd_stat_init(void);
-void nfsd_stat_shutdown(void);
+int nfsd_stat_counters_init(void);
+void nfsd_stat_counters_destroy(void);
+void nfsd_proc_stat_init(struct net *net);
+void nfsd_proc_stat_shutdown(struct net *net);
 
 static inline void nfsd_stats_rc_hits_inc(void)
 {