NFSD: Trace delegation revocations

Delegation revocation is an exceptional event that is not otherwise
visible externally (eg, no network traffic is emitted). Generate a
trace record when it occurs so that revocation can be observed or
other activity can be triggered. Example:

nfsd-1104  [005]  1912.002544: nfsd_stid_revoke:        client 633c9343:4e82788d stateid 00000003:00000001 ref=2 type=DELEG

Trace infrastructure is provided for subsequent additional tracing
related to nfs4_stid activity.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>

fs/nfsd/nfs4state.c

@@ -1366,6 +1366,8 @@ static void revoke_delegation(struct nfs4_delegation *dp)
 
 	WARN_ON(!list_empty(&dp->dl_recall_lru));
 
+	trace_nfsd_stid_revoke(&dp->dl_stid);
+
 	if (clp->cl_minorversion) {
 		dp->dl_stid.sc_type = NFS4_REVOKED_DELEG_STID;
 		refcount_inc(&dp->dl_stid.sc_count);

fs/nfsd/trace.h

@@ -637,6 +637,61 @@ DEFINE_EVENT(nfsd_stateseqid_class, nfsd_##name, \
 DEFINE_STATESEQID_EVENT(preprocess);
 DEFINE_STATESEQID_EVENT(open_confirm);
 
+TRACE_DEFINE_ENUM(NFS4_OPEN_STID);
+TRACE_DEFINE_ENUM(NFS4_LOCK_STID);
+TRACE_DEFINE_ENUM(NFS4_DELEG_STID);
+TRACE_DEFINE_ENUM(NFS4_CLOSED_STID);
+TRACE_DEFINE_ENUM(NFS4_REVOKED_DELEG_STID);
+TRACE_DEFINE_ENUM(NFS4_CLOSED_DELEG_STID);
+TRACE_DEFINE_ENUM(NFS4_LAYOUT_STID);
+
+#define show_stid_type(x)						\
+	__print_flags(x, "|",						\
+		{ NFS4_OPEN_STID,		"OPEN" },		\
+		{ NFS4_LOCK_STID,		"LOCK" },		\
+		{ NFS4_DELEG_STID,		"DELEG" },		\
+		{ NFS4_CLOSED_STID,		"CLOSED" },		\
+		{ NFS4_REVOKED_DELEG_STID,	"REVOKED" },		\
+		{ NFS4_CLOSED_DELEG_STID,	"CLOSED_DELEG" },	\
+		{ NFS4_LAYOUT_STID,		"LAYOUT" })
+
+DECLARE_EVENT_CLASS(nfsd_stid_class,
+	TP_PROTO(
+		const struct nfs4_stid *stid
+	),
+	TP_ARGS(stid),
+	TP_STRUCT__entry(
+		__field(unsigned long, sc_type)
+		__field(int, sc_count)
+		__field(u32, cl_boot)
+		__field(u32, cl_id)
+		__field(u32, si_id)
+		__field(u32, si_generation)
+	),
+	TP_fast_assign(
+		const stateid_t *stp = &stid->sc_stateid;
+
+		__entry->sc_type = stid->sc_type;
+		__entry->sc_count = refcount_read(&stid->sc_count);
+		__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;
+	),
+	TP_printk("client %08x:%08x stateid %08x:%08x ref=%d type=%s",
+		__entry->cl_boot, __entry->cl_id,
+		__entry->si_id, __entry->si_generation,
+		__entry->sc_count, show_stid_type(__entry->sc_type)
+	)
+);
+
+#define DEFINE_STID_EVENT(name)					\
+DEFINE_EVENT(nfsd_stid_class, nfsd_stid_##name,			\
+	TP_PROTO(const struct nfs4_stid *stid),			\
+	TP_ARGS(stid))
+
+DEFINE_STID_EVENT(revoke);
+
 DECLARE_EVENT_CLASS(nfsd_clientid_class,
 	TP_PROTO(const clientid_t *clid),
 	TP_ARGS(clid),