NFSD: Report count of calls to nfsd_file_acquire()

Count the number of successful acquisitions that did not create a
file (ie, acquisitions that do not result in a compulsory cache
miss). This count can be compared directly with the reported hit
count to compute a hit ratio.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/filecache.c

@@ -43,6 +43,7 @@ struct nfsd_fcache_bucket {
 };
 
 static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);
+static DEFINE_PER_CPU(unsigned long, nfsd_file_acquisitions);
 
 struct nfsd_fcache_disposal {
 	struct work_struct work;
@@ -955,6 +956,8 @@ nfsd_do_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	status = nfserrno(nfsd_open_break_lease(file_inode(nf->nf_file), may_flags));
 out:
 	if (status == nfs_ok) {
+		if (open)
+			this_cpu_inc(nfsd_file_acquisitions);
 		*pnf = nf;
 	} else {
 		nfsd_file_put(nf);
@@ -1047,8 +1050,9 @@ nfsd_file_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
  */
 static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
 {
+	unsigned long hits = 0, acquisitions = 0;
 	unsigned int i, count = 0, longest = 0;
-	unsigned long lru = 0, hits = 0;
+	unsigned long lru = 0;
 
 	/*
 	 * No need for spinlocks here since we're not terribly interested in
@@ -1065,13 +1069,16 @@ static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
 	}
 	mutex_unlock(&nfsd_mutex);
 
-	for_each_possible_cpu(i)
+	for_each_possible_cpu(i) {
 		hits += per_cpu(nfsd_file_cache_hits, i);
+		acquisitions += per_cpu(nfsd_file_acquisitions, i);
+	}
 
 	seq_printf(m, "total entries: %u\n", count);
 	seq_printf(m, "longest chain: %u\n", longest);
 	seq_printf(m, "lru entries:   %lu\n", lru);
 	seq_printf(m, "cache hits:    %lu\n", hits);
+	seq_printf(m, "acquisitions:  %lu\n", acquisitions);
 	return 0;
 }