nfsd: protect concurrent access to nfsd stats counters

nfsd stats counters can be updated by concurrent nfsd threads without any
protection.

Convert some nfsd_stats and nfsd_net struct members to use percpu counters.

The longest_chain* members of struct nfsd_net remain unprotected.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 64 insertions, 13 deletions

diff --git a/fs/nfsd/stats.c b/fs/nfsd/stats.c
index e928e224205a..1d3b881e7382 100644
--- a/fs/nfsd/stats.c
+++ b/fs/nfsd/stats.c
@@ -36,13 +36,13 @@ static int nfsd_proc_show(struct seq_file *seq, void *v)
 {
 	int i;
 
-	seq_printf(seq, "rc %u %u %u\nfh %u 0 0 0 0\nio %u %u\n",
-		      nfsdstats.rchits,
-		      nfsdstats.rcmisses,
-		      nfsdstats.rcnocache,
-		      nfsdstats.fh_stale,
-		      nfsdstats.io_read,
-		      nfsdstats.io_write);
+	seq_printf(seq, "rc %lld %lld %lld\nfh %lld 0 0 0 0\nio %lld %lld\n",
+		   percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_HITS]),
+		   percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_MISSES]),
+		   percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_NOCACHE]),
+		   percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_FH_STALE]),
+		   percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_IO_READ]),
+		   percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_IO_WRITE]));
 
 	/* thread usage: */
 	seq_printf(seq, "th %u 0", nfsdstats.th_cnt);
@@ -61,8 +61,10 @@ static int nfsd_proc_show(struct seq_file *seq, void *v)
 	/* Show count for individual nfsv4 operations */
 	/* Writing operation numbers 0 1 2 also for maintaining uniformity */
 	seq_printf(seq,"proc4ops %u", LAST_NFS4_OP + 1);
-	for (i = 0; i <= LAST_NFS4_OP; i++)
-		seq_printf(seq, " %u", nfsdstats.nfs4_opcount[i]);
+	for (i = 0; i <= LAST_NFS4_OP; i++) {
+		seq_printf(seq, " %lld",
+			   percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_NFS4_OP(i)]));
+	}
 
 	seq_putc(seq, '\n');
 #endif
@@ -82,14 +84,63 @@ static const struct proc_ops nfsd_proc_ops = {
 	.proc_release	= single_release,
 };
 
-void
-nfsd_stat_init(void)
+int nfsd_percpu_counters_init(struct percpu_counter counters[], int num)
 {
+	int i, err = 0;
+
+	for (i = 0; !err && i < num; i++)
+		err = percpu_counter_init(&counters[i], 0, GFP_KERNEL);
+
+	if (!err)
+		return 0;
+
+	for (; i > 0; i--)
+		percpu_counter_destroy(&counters[i-1]);
+
+	return err;
+}
+
+void nfsd_percpu_counters_reset(struct percpu_counter counters[], int num)
+{
+	int i;
+
+	for (i = 0; i < num; i++)
+		percpu_counter_set(&counters[i], 0);
+}
+
+void nfsd_percpu_counters_destroy(struct percpu_counter counters[], int num)
+{
+	int i;
+
+	for (i = 0; i < num; i++)
+		percpu_counter_destroy(&counters[i]);
+}
+
+static int nfsd_stat_counters_init(void)
+{
+	return nfsd_percpu_counters_init(nfsdstats.counter, NFSD_STATS_COUNTERS_NUM);
+}
+
+static void nfsd_stat_counters_destroy(void)
+{
+	nfsd_percpu_counters_destroy(nfsdstats.counter, NFSD_STATS_COUNTERS_NUM);
+}
+
+int nfsd_stat_init(void)
+{
+	int err;
+
+	err = nfsd_stat_counters_init();
+	if (err)
+		return err;
+
 	svc_proc_register(&init_net, &nfsd_svcstats, &nfsd_proc_ops);
+
+	return 0;
 }
 
-void
-nfsd_stat_shutdown(void)
+void nfsd_stat_shutdown(void)
 {
+	nfsd_stat_counters_destroy();
 	svc_proc_unregister(&init_net, "nfsd");
 }