NFSD: Add callback operation lifetime trace points

Help observe the flow of callback operations.

bc_shutdown() records exactly when the backchannel RPC client is
destroyed and cl_cb_client is replaced with NULL.

Examples include:

         nfsd-955   [004]   650.013997: nfsd_cb_queue:        addr=192.168.122.6:0 client 65b3c5b8:f541f749 cb=0xffff8881134b02f8 (first try)
kworker/u21:4-497   [004]   650.014050: nfsd_cb_seq_status:   task:00000001@00000001 sessionid=65b3c5b8:f541f749:00000001:00000000 tk_status=-107 seq_status=1
kworker/u21:4-497   [004]   650.014051: nfsd_cb_restart:      addr=192.168.122.6:0 client 65b3c5b8:f541f749 cb=0xffff88810e39f400 (first try)
kworker/u21:4-497   [004]   650.014066: nfsd_cb_queue:        addr=192.168.122.6:0 client 65b3c5b8:f541f749 cb=0xffff88810e39f400 (need restart)


kworker/u16:0-10    [006]   650.065750: nfsd_cb_start:        addr=192.168.122.6:0 client 65b3c5b8:f541f749 state=UNKNOWN
kworker/u16:0-10    [006]   650.065752: nfsd_cb_bc_update:    addr=192.168.122.6:0 client 65b3c5b8:f541f749 cb=0xffff8881134b02f8 (first try)
kworker/u16:0-10    [006]   650.065754: nfsd_cb_bc_shutdown:  addr=192.168.122.6:0 client 65b3c5b8:f541f749 cb=0xffff8881134b02f8 (first try)
kworker/u16:0-10    [006]   650.065810: nfsd_cb_new_state:    addr=192.168.122.6:0 client 65b3c5b8:f541f749 state=DOWN
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

@@ -887,12 +887,14 @@ static struct workqueue_struct *callback_wq;
 
 static bool nfsd4_queue_cb(struct nfsd4_callback *cb)
 {
+	trace_nfsd_cb_queue(cb->cb_clp, cb);
 	return queue_delayed_work(callback_wq, &cb->cb_work, 0);
 }
 
 static void nfsd4_queue_cb_delayed(struct nfsd4_callback *cb,
 				   unsigned long msecs)
 {
+	trace_nfsd_cb_queue(cb->cb_clp, cb);
 	queue_delayed_work(callback_wq, &cb->cb_work,
 			   msecs_to_jiffies(msecs));
 }
@@ -1113,6 +1115,7 @@ static void nfsd41_destroy_cb(struct nfsd4_callback *cb)
 {
 	struct nfs4_client *clp = cb->cb_clp;
 
+	trace_nfsd_cb_destroy(clp, cb);
 	nfsd41_cb_release_slot(cb);
 	if (cb->cb_ops && cb->cb_ops->release)
 		cb->cb_ops->release(cb);
@@ -1227,6 +1230,7 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
 	goto out;
 need_restart:
 	if (!test_bit(NFSD4_CLIENT_CB_KILL, &clp->cl_flags)) {
+		trace_nfsd_cb_restart(clp, cb);
 		task->tk_status = 0;
 		cb->cb_need_restart = true;
 	}
@@ -1340,11 +1344,14 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
 	struct nfsd4_conn *c;
 	int err;
 
+	trace_nfsd_cb_bc_update(clp, cb);
+
 	/*
 	 * This is either an update, or the client dying; in either case,
 	 * kill the old client:
 	 */
 	if (clp->cl_cb_client) {
+		trace_nfsd_cb_bc_shutdown(clp, cb);
 		rpc_shutdown_client(clp->cl_cb_client);
 		clp->cl_cb_client = NULL;
 		put_cred(clp->cl_cb_cred);
@@ -1356,6 +1363,7 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
 	}
 	if (test_bit(NFSD4_CLIENT_CB_KILL, &clp->cl_flags))
 		return;
+
 	spin_lock(&clp->cl_lock);
 	/*
 	 * Only serialized callback code is allowed to clear these

fs/nfsd/trace.h

@@ -1443,6 +1443,48 @@ TRACE_EVENT(nfsd_cb_setup_err,
 		__entry->error)
 );
 
+DECLARE_EVENT_CLASS(nfsd_cb_lifetime_class,
+	TP_PROTO(
+		const struct nfs4_client *clp,
+		const struct nfsd4_callback *cb
+	),
+	TP_ARGS(clp, cb),
+	TP_STRUCT__entry(
+		__field(u32, cl_boot)
+		__field(u32, cl_id)
+		__field(const void *, cb)
+		__field(bool, need_restart)
+		__sockaddr(addr, clp->cl_cb_conn.cb_addrlen)
+	),
+	TP_fast_assign(
+		__entry->cl_boot = clp->cl_clientid.cl_boot;
+		__entry->cl_id = clp->cl_clientid.cl_id;
+		__entry->cb = cb;
+		__entry->need_restart = cb->cb_need_restart;
+		__assign_sockaddr(addr, &clp->cl_cb_conn.cb_addr,
+				  clp->cl_cb_conn.cb_addrlen)
+	),
+	TP_printk("addr=%pISpc client %08x:%08x cb=%p%s",
+		__get_sockaddr(addr), __entry->cl_boot, __entry->cl_id,
+		__entry->cb, __entry->need_restart ?
+			" (need restart)" : " (first try)"
+	)
+);
+
+#define DEFINE_NFSD_CB_LIFETIME_EVENT(name)		\
+DEFINE_EVENT(nfsd_cb_lifetime_class, nfsd_cb_##name,	\
+	TP_PROTO(					\
+		const struct nfs4_client *clp,		\
+		const struct nfsd4_callback *cb		\
+	),						\
+	TP_ARGS(clp, cb))
+
+DEFINE_NFSD_CB_LIFETIME_EVENT(queue);
+DEFINE_NFSD_CB_LIFETIME_EVENT(destroy);
+DEFINE_NFSD_CB_LIFETIME_EVENT(restart);
+DEFINE_NFSD_CB_LIFETIME_EVENT(bc_update);
+DEFINE_NFSD_CB_LIFETIME_EVENT(bc_shutdown);
+
 TRACE_EVENT(nfsd_cb_seq_status,
 	TP_PROTO(
 		const struct rpc_task *task,

include/trace/misc/nfs.h

@@ -385,3 +385,37 @@ TRACE_DEFINE_ENUM(IOMODE_ANY);
 		{ SEQ4_STATUS_RESTART_RECLAIM_NEEDED,	"RESTART_RECLAIM_NEEDED" }, \
 		{ SEQ4_STATUS_CB_PATH_DOWN_SESSION,	"CB_PATH_DOWN_SESSION" }, \
 		{ SEQ4_STATUS_BACKCHANNEL_FAULT,	"BACKCHANNEL_FAULT" })
+
+TRACE_DEFINE_ENUM(OP_CB_GETATTR);
+TRACE_DEFINE_ENUM(OP_CB_RECALL);
+TRACE_DEFINE_ENUM(OP_CB_LAYOUTRECALL);
+TRACE_DEFINE_ENUM(OP_CB_NOTIFY);
+TRACE_DEFINE_ENUM(OP_CB_PUSH_DELEG);
+TRACE_DEFINE_ENUM(OP_CB_RECALL_ANY);
+TRACE_DEFINE_ENUM(OP_CB_RECALLABLE_OBJ_AVAIL);
+TRACE_DEFINE_ENUM(OP_CB_RECALL_SLOT);
+TRACE_DEFINE_ENUM(OP_CB_SEQUENCE);
+TRACE_DEFINE_ENUM(OP_CB_WANTS_CANCELLED);
+TRACE_DEFINE_ENUM(OP_CB_NOTIFY_LOCK);
+TRACE_DEFINE_ENUM(OP_CB_NOTIFY_DEVICEID);
+TRACE_DEFINE_ENUM(OP_CB_OFFLOAD);
+TRACE_DEFINE_ENUM(OP_CB_ILLEGAL);
+
+#define show_nfs4_cb_op(x) \
+	__print_symbolic(x, \
+		{ 0,				"CB_NULL" }, \
+		{ 1,				"CB_COMPOUND" }, \
+		{ OP_CB_GETATTR,		"CB_GETATTR" }, \
+		{ OP_CB_RECALL,			"CB_RECALL" }, \
+		{ OP_CB_LAYOUTRECALL,		"CB_LAYOUTRECALL" }, \
+		{ OP_CB_NOTIFY,			"CB_NOTIFY" }, \
+		{ OP_CB_PUSH_DELEG,		"CB_PUSH_DELEG" }, \
+		{ OP_CB_RECALL_ANY,		"CB_RECALL_ANY" }, \
+		{ OP_CB_RECALLABLE_OBJ_AVAIL,	"CB_RECALLABLE_OBJ_AVAIL" }, \
+		{ OP_CB_RECALL_SLOT,		"CB_RECALL_SLOT" }, \
+		{ OP_CB_SEQUENCE,		"CB_SEQUENCE" }, \
+		{ OP_CB_WANTS_CANCELLED,	"CB_WANTS_CANCELLED" }, \
+		{ OP_CB_NOTIFY_LOCK,		"CB_NOTIFY_LOCK" }, \
+		{ OP_CB_NOTIFY_DEVICEID,	"CB_NOTIFY_DEVICEID" }, \
+		{ OP_CB_OFFLOAD,		"CB_OFFLOAD" }, \
+		{ OP_CB_ILLEGAL,		"CB_ILLEGAL" })