nfsd: report per-export stats

Collect some nfsd stats per export in addition to the global stats.

A new nfsdfs export_stats file is created.  It uses the same ops as the
exports file to iterate the export entries and we use the file's name to
determine the reported info per export.  For example:

 $ cat /proc/fs/nfsd/export_stats
 # Version 1.1
 # Path Client Start-time
 #	Stats
 /test	localhost	92
	fh_stale: 0
	io_read: 9
	io_write: 1

Every export entry reports the start time when stats collection
started, so stats collecting scripts can know if stats where reset
between samples.

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

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h
index e7daa1f246f0..ee0e3aba4a6e 100644
--- a/fs/nfsd/export.h
+++ b/fs/nfsd/export.h
@@ -6,6 +6,7 @@
 #define NFSD_EXPORT_H
 
 #include <linux/sunrpc/cache.h>
+#include <linux/percpu_counter.h>
 #include <uapi/linux/nfsd/export.h>
 #include <linux/nfs4.h>
 
@@ -46,6 +47,19 @@ struct exp_flavor_info {
 	u32	flags;
 };
 
+/* Per-export stats */
+enum {
+	EXP_STATS_FH_STALE,
+	EXP_STATS_IO_READ,
+	EXP_STATS_IO_WRITE,
+	EXP_STATS_COUNTERS_NUM
+};
+
+struct export_stats {
+	time64_t		start_time;
+	struct percpu_counter	counter[EXP_STATS_COUNTERS_NUM];
+};
+
 struct svc_export {
 	struct cache_head	h;
 	struct auth_domain *	ex_client;
@@ -62,6 +76,7 @@ struct svc_export {
 	struct nfsd4_deviceid_map *ex_devid_map;
 	struct cache_detail	*cd;
 	struct rcu_head		ex_rcu;
+	struct export_stats	ex_stats;
 };
 
 /* an "export key" (expkey) maps a filehandlefragement to an