NFSD: Trace filecache opens

Instrument calls to nfsd_open_verified() to get a sense of the
filecache hit rate.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/filecache.c

@@ -995,10 +995,11 @@ nfsd_do_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
 
 	nf->nf_mark = nfsd_file_mark_find_or_create(nf);
 	if (nf->nf_mark) {
-		if (open)
+		if (open) {
 			status = nfsd_open_verified(rqstp, fhp, may_flags,
 						    &nf->nf_file);
-		else
+			trace_nfsd_file_open(nf, status);
+		} else
 			status = nfs_ok;
 	} else
 		status = nfserr_jukebox;

fs/nfsd/trace.h

@@ -784,6 +784,34 @@ TRACE_EVENT(nfsd_file_acquire,
 			__entry->nf_file, __entry->status)
 );
 
+TRACE_EVENT(nfsd_file_open,
+	TP_PROTO(struct nfsd_file *nf, __be32 status),
+	TP_ARGS(nf, status),
+	TP_STRUCT__entry(
+		__field(unsigned int, nf_hashval)
+		__field(void *, nf_inode)	/* cannot be dereferenced */
+		__field(int, nf_ref)
+		__field(unsigned long, nf_flags)
+		__field(unsigned long, nf_may)
+		__field(void *, nf_file)	/* cannot be dereferenced */
+	),
+	TP_fast_assign(
+		__entry->nf_hashval = nf->nf_hashval;
+		__entry->nf_inode = nf->nf_inode;
+		__entry->nf_ref = refcount_read(&nf->nf_ref);
+		__entry->nf_flags = nf->nf_flags;
+		__entry->nf_may = nf->nf_may;
+		__entry->nf_file = nf->nf_file;
+	),
+	TP_printk("hash=0x%x inode=%p ref=%d flags=%s may=%s file=%p",
+		__entry->nf_hashval,
+		__entry->nf_inode,
+		__entry->nf_ref,
+		show_nf_flags(__entry->nf_flags),
+		show_nfsd_may_flags(__entry->nf_may),
+		__entry->nf_file)
+)
+
 DECLARE_EVENT_CLASS(nfsd_file_search_class,
 	TP_PROTO(struct inode *inode, unsigned int hash, int found),
 	TP_ARGS(inode, hash, found),