NFSD: Add tracepoints in nfsd_dispatch()

For troubleshooting purposes, record GARBAGE_ARGS and CANT_ENCODE
failures.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfssvc.c

@@ -29,6 +29,8 @@
 #include "netns.h"
 #include "filecache.h"
 
+#include "trace.h"
+
 #define NFSDDBG_FACILITY	NFSDDBG_SVC
 
 bool inter_copy_offload_enable;
@@ -1009,11 +1011,8 @@ int nfsd_dispatch(struct svc_rqst *rqstp, __be32 *statp)
 	struct kvec *resv = &rqstp->rq_res.head[0];
 	__be32 *p;
 
-	dprintk("nfsd_dispatch: vers %d proc %d\n",
-				rqstp->rq_vers, rqstp->rq_proc);
-
 	if (nfs_request_too_big(rqstp, proc))
-		goto out_too_large;
+		goto out_decode_err;
 
 	/*
 	 * Give the xdr decoder a chance to change this if it wants
@@ -1052,24 +1051,18 @@ int nfsd_dispatch(struct svc_rqst *rqstp, __be32 *statp)
 out_cached_reply:
 	return 1;
 
-out_too_large:
-	dprintk("nfsd: NFSv%d argument too large\n", rqstp->rq_vers);
-	*statp = rpc_garbage_args;
-	return 1;
-
 out_decode_err:
-	dprintk("nfsd: failed to decode arguments!\n");
+	trace_nfsd_garbage_args_err(rqstp);
 	*statp = rpc_garbage_args;
 	return 1;
 
 out_update_drop:
-	dprintk("nfsd: Dropping request; may be revisited later\n");
 	nfsd_cache_update(rqstp, RC_NOCACHE, NULL);
 out_dropit:
 	return 0;
 
 out_encode_err:
-	dprintk("nfsd: failed to encode result!\n");
+	trace_nfsd_cant_encode_err(rqstp);
 	nfsd_cache_update(rqstp, RC_NOCACHE, NULL);
 	*statp = rpc_system_err;
 	return 1;

fs/nfsd/trace.h

@@ -12,6 +12,66 @@
 #include "export.h"
 #include "nfsfh.h"
 
+#define NFSD_TRACE_PROC_ARG_FIELDS \
+		__field(unsigned int, netns_ino) \
+		__field(u32, xid) \
+		__array(unsigned char, server, sizeof(struct sockaddr_in6)) \
+		__array(unsigned char, client, sizeof(struct sockaddr_in6))
+
+#define NFSD_TRACE_PROC_ARG_ASSIGNMENTS \
+		do { \
+			__entry->netns_ino = SVC_NET(rqstp)->ns.inum; \
+			__entry->xid = be32_to_cpu(rqstp->rq_xid); \
+			memcpy(__entry->server, &rqstp->rq_xprt->xpt_local, \
+			       rqstp->rq_xprt->xpt_locallen); \
+			memcpy(__entry->client, &rqstp->rq_xprt->xpt_remote, \
+			       rqstp->rq_xprt->xpt_remotelen); \
+		} while (0);
+
+TRACE_EVENT(nfsd_garbage_args_err,
+	TP_PROTO(
+		const struct svc_rqst *rqstp
+	),
+	TP_ARGS(rqstp),
+	TP_STRUCT__entry(
+		NFSD_TRACE_PROC_ARG_FIELDS
+
+		__field(u32, vers)
+		__field(u32, proc)
+	),
+	TP_fast_assign(
+		NFSD_TRACE_PROC_ARG_ASSIGNMENTS
+
+		__entry->vers = rqstp->rq_vers;
+		__entry->proc = rqstp->rq_proc;
+	),
+	TP_printk("xid=0x%08x vers=%u proc=%u",
+		__entry->xid, __entry->vers, __entry->proc
+	)
+);
+
+TRACE_EVENT(nfsd_cant_encode_err,
+	TP_PROTO(
+		const struct svc_rqst *rqstp
+	),
+	TP_ARGS(rqstp),
+	TP_STRUCT__entry(
+		NFSD_TRACE_PROC_ARG_FIELDS
+
+		__field(u32, vers)
+		__field(u32, proc)
+	),
+	TP_fast_assign(
+		NFSD_TRACE_PROC_ARG_ASSIGNMENTS
+
+		__entry->vers = rqstp->rq_vers;
+		__entry->proc = rqstp->rq_proc;
+	),
+	TP_printk("xid=0x%08x vers=%u proc=%u",
+		__entry->xid, __entry->vers, __entry->proc
+	)
+);
+
 #define show_nfsd_may_flags(x)						\
 	__print_flags(x, "|",						\
 		{ NFSD_MAY_EXEC,		"EXEC" },		\