NFSD: Replace dprintks in nfsd4_cb_sequence_done()

Improve observability of backchannel session operation.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4callback.c

@@ -1165,6 +1165,8 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
 	if (!cb->cb_holds_slot)
 		goto need_restart;
 
+	/* This is the operation status code for CB_SEQUENCE */
+	trace_nfsd_cb_seq_status(task, cb);
 	switch (cb->cb_seq_status) {
 	case 0:
 		/*
@@ -1210,13 +1212,10 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
 		break;
 	default:
 		nfsd4_mark_cb_fault(cb->cb_clp, cb->cb_seq_status);
-		dprintk("%s: unprocessed error %d\n", __func__,
-			cb->cb_seq_status);
 	}
-
 	nfsd41_cb_release_slot(cb);
-	dprintk("%s: freed slot, new seqid=%d\n", __func__,
-		clp->cl_cb_session->se_cb_seq_nr);
+
+	trace_nfsd_cb_free_slot(task, cb);
 
 	if (RPC_SIGNALLED(task))
 		goto need_restart;

fs/nfsd/trace.h

@@ -9,8 +9,10 @@
 #define _NFSD_TRACE_H
 
 #include <linux/tracepoint.h>
+#include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/xprt.h>
 #include <trace/misc/nfs.h>
+#include <trace/misc/sunrpc.h>
 
 #include "export.h"
 #include "nfsfh.h"
@@ -1440,6 +1442,86 @@ TRACE_EVENT(nfsd_cb_setup_err,
 		__entry->error)
 );
 
+TRACE_EVENT(nfsd_cb_seq_status,
+	TP_PROTO(
+		const struct rpc_task *task,
+		const struct nfsd4_callback *cb
+	),
+	TP_ARGS(task, cb),
+	TP_STRUCT__entry(
+		__field(unsigned int, task_id)
+		__field(unsigned int, client_id)
+		__field(u32, cl_boot)
+		__field(u32, cl_id)
+		__field(u32, seqno)
+		__field(u32, reserved)
+		__field(int, tk_status)
+		__field(int, seq_status)
+	),
+	TP_fast_assign(
+		const struct nfs4_client *clp = cb->cb_clp;
+		const struct nfsd4_session *session = clp->cl_cb_session;
+		const struct nfsd4_sessionid *sid =
+			(struct nfsd4_sessionid *)&session->se_sessionid;
+
+		__entry->task_id = task->tk_pid;
+		__entry->client_id = task->tk_client ?
+				     task->tk_client->cl_clid : -1;
+		__entry->cl_boot = sid->clientid.cl_boot;
+		__entry->cl_id = sid->clientid.cl_id;
+		__entry->seqno = sid->sequence;
+		__entry->reserved = sid->reserved;
+		__entry->tk_status = task->tk_status;
+		__entry->seq_status = cb->cb_seq_status;
+	),
+	TP_printk(SUNRPC_TRACE_TASK_SPECIFIER
+		" sessionid=%08x:%08x:%08x:%08x tk_status=%d seq_status=%d\n",
+		__entry->task_id, __entry->client_id,
+		__entry->cl_boot, __entry->cl_id,
+		__entry->seqno, __entry->reserved,
+		__entry->tk_status, __entry->seq_status
+	)
+);
+
+TRACE_EVENT(nfsd_cb_free_slot,
+	TP_PROTO(
+		const struct rpc_task *task,
+		const struct nfsd4_callback *cb
+	),
+	TP_ARGS(task, cb),
+	TP_STRUCT__entry(
+		__field(unsigned int, task_id)
+		__field(unsigned int, client_id)
+		__field(u32, cl_boot)
+		__field(u32, cl_id)
+		__field(u32, seqno)
+		__field(u32, reserved)
+		__field(u32, slot_seqno)
+	),
+	TP_fast_assign(
+		const struct nfs4_client *clp = cb->cb_clp;
+		const struct nfsd4_session *session = clp->cl_cb_session;
+		const struct nfsd4_sessionid *sid =
+			(struct nfsd4_sessionid *)&session->se_sessionid;
+
+		__entry->task_id = task->tk_pid;
+		__entry->client_id = task->tk_client ?
+				     task->tk_client->cl_clid : -1;
+		__entry->cl_boot = sid->clientid.cl_boot;
+		__entry->cl_id = sid->clientid.cl_id;
+		__entry->seqno = sid->sequence;
+		__entry->reserved = sid->reserved;
+		__entry->slot_seqno = session->se_cb_seq_nr;
+	),
+	TP_printk(SUNRPC_TRACE_TASK_SPECIFIER
+		" sessionid=%08x:%08x:%08x:%08x new slot seqno=%u\n",
+		__entry->task_id, __entry->client_id,
+		__entry->cl_boot, __entry->cl_id,
+		__entry->seqno, __entry->reserved,
+		__entry->slot_seqno
+	)
+);
+
 TRACE_EVENT_CONDITION(nfsd_cb_recall,
 	TP_PROTO(
 		const struct nfs4_stid *stid