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, 14 insertions, 9 deletions

diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h
index 7346acda9d76..c330f5bd0cf3 100644
--- a/fs/nfsd/netns.h
+++ b/fs/nfsd/netns.h
@@ -10,6 +10,7 @@
 
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
+#include <linux/percpu_counter.h>
 
 /* Hash tables for nfs4_clientid state */
 #define CLIENT_HASH_BITS                 4
@@ -21,6 +22,14 @@
 struct cld_net;
 struct nfsd4_client_tracking_ops;
 
+enum {
+	/* cache misses due only to checksum comparison failures */
+	NFSD_NET_PAYLOAD_MISSES,
+	/* amount of memory (in bytes) currently consumed by the DRC */
+	NFSD_NET_DRC_MEM_USAGE,
+	NFSD_NET_COUNTERS_NUM
+};
+
 /*
  * Represents a nfsd "container". With respect to nfsv4 state tracking, the
  * fields of interest are the *_id_hashtbls and the *_name_tree. These track
@@ -149,20 +158,16 @@ struct nfsd_net {
 
 	/*
 	 * Stats and other tracking of on the duplicate reply cache.
-	 * These fields and the "rc" fields in nfsdstats are modified
-	 * with only the per-bucket cache lock, which isn't really safe
-	 * and should be fixed if we want the statistics to be
-	 * completely accurate.
+	 * The longest_chain* fields are modified with only the per-bucket
+	 * cache lock, which isn't really safe and should be fixed if we want
+	 * these statistics to be completely accurate.
 	 */
 
 	/* total number of entries */
 	atomic_t                 num_drc_entries;
 
-	/* cache misses due only to checksum comparison failures */
-	unsigned int             payload_misses;
-
-	/* amount of memory (in bytes) currently consumed by the DRC */
-	unsigned int             drc_mem_usage;
+	/* Per-netns stats counters */
+	struct percpu_counter    counter[NFSD_NET_COUNTERS_NUM];
 
 	/* longest hash chain seen */
 	unsigned int             longest_chain;