NFSD: Add an nfsd_cb_offload tracepoint

Record the arguments of CB_OFFLOAD callbacks so we can better
observe asynchronous copy-offload behavior. For example:

nfsd-995   [008]  7721.934222: nfsd_cb_offload:
        addr=192.168.2.51:0 client 6092a47c:35a43fc1 fh_hash=0x8739113a
        count=116528 status=0
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: Olga Kornievskaia <kolga@netapp.com>
Cc: Dai Ngo <Dai.Ngo@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4proc.c

@@ -1497,6 +1497,8 @@ static int nfsd4_do_async_copy(void *data)
 	memcpy(&cb_copy->fh, &copy->fh, sizeof(copy->fh));
 	nfsd4_init_cb(&cb_copy->cp_cb, cb_copy->cp_clp,
 			&nfsd4_cb_offload_ops, NFSPROC4_CLNT_CB_OFFLOAD);
+	trace_nfsd_cb_offload(copy->cp_clp, &copy->cp_res.cb_stateid,
+			      &copy->fh, copy->cp_count, copy->nfserr);
 	nfsd4_run_cb(&cb_copy->cp_cb);
 out:
 	if (!copy->cp_intra)

fs/nfsd/trace.h

@@ -1053,6 +1053,42 @@ TRACE_EVENT(nfsd_cb_notify_lock,
 		__entry->fh_hash)
 );
 
+TRACE_EVENT(nfsd_cb_offload,
+	TP_PROTO(
+		const struct nfs4_client *clp,
+		const stateid_t *stp,
+		const struct knfsd_fh *fh,
+		u64 count,
+		__be32 status
+	),
+	TP_ARGS(clp, stp, fh, count, status),
+	TP_STRUCT__entry(
+		__field(u32, cl_boot)
+		__field(u32, cl_id)
+		__field(u32, si_id)
+		__field(u32, si_generation)
+		__field(u32, fh_hash)
+		__field(int, status)
+		__field(u64, count)
+		__array(unsigned char, addr, sizeof(struct sockaddr_in6))
+	),
+	TP_fast_assign(
+		__entry->cl_boot = stp->si_opaque.so_clid.cl_boot;
+		__entry->cl_id = stp->si_opaque.so_clid.cl_id;
+		__entry->si_id = stp->si_opaque.so_id;
+		__entry->si_generation = stp->si_generation;
+		__entry->fh_hash = knfsd_fh_hash(fh);
+		__entry->status = be32_to_cpu(status);
+		__entry->count = count;
+		memcpy(__entry->addr, &clp->cl_cb_conn.cb_addr,
+			sizeof(struct sockaddr_in6));
+	),
+	TP_printk("addr=%pISpc client %08x:%08x stateid %08x:%08x fh_hash=0x%08x count=%llu status=%d",
+		__entry->addr, __entry->cl_boot, __entry->cl_id,
+		__entry->si_id, __entry->si_generation,
+		__entry->fh_hash, __entry->count, __entry->status)
+);
+
 #endif /* _NFSD_TRACE_H */
 
 #undef TRACE_INCLUDE_PATH