NFSD: Short-circuit fh_verify tracepoints for LOCALIO

LOCALIO will be able to call fh_verify() with a NULL rqstp. In this
case, the existing trace points need to be skipped because they
want to dereference the address fields in the passed-in rqstp.

Temporarily make these trace points conditional to avoid a seg
fault in this case. Putting the "rqstp != NULL" check in the trace
points themselves makes the check more efficient.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Acked-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

fs/nfsd/trace.h

@@ -193,7 +193,7 @@ TRACE_EVENT(nfsd_compound_encode_err,
 		{ S_IFIFO,		"FIFO" }, \
 		{ S_IFSOCK,		"SOCK" })
 
-TRACE_EVENT(nfsd_fh_verify,
+TRACE_EVENT_CONDITION(nfsd_fh_verify,
 	TP_PROTO(
 		const struct svc_rqst *rqstp,
 		const struct svc_fh *fhp,
@@ -201,6 +201,7 @@ TRACE_EVENT(nfsd_fh_verify,
 		int access
 	),
 	TP_ARGS(rqstp, fhp, type, access),
+	TP_CONDITION(rqstp != NULL),
 	TP_STRUCT__entry(
 		__field(unsigned int, netns_ino)
 		__sockaddr(server, rqstp->rq_xprt->xpt_remotelen)
@@ -239,7 +240,7 @@ TRACE_EVENT_CONDITION(nfsd_fh_verify_err,
 		__be32 error
 	),
 	TP_ARGS(rqstp, fhp, type, access, error),
-	TP_CONDITION(error),
+	TP_CONDITION(rqstp != NULL && error),
 	TP_STRUCT__entry(
 		__field(unsigned int, netns_ino)
 		__sockaddr(server, rqstp->rq_xprt->xpt_remotelen)
@@ -295,12 +296,13 @@ DECLARE_EVENT_CLASS(nfsd_fh_err_class,
 		  __entry->status)
 )
 
-#define DEFINE_NFSD_FH_ERR_EVENT(name)		\
-DEFINE_EVENT(nfsd_fh_err_class, nfsd_##name,	\
-	TP_PROTO(struct svc_rqst *rqstp,	\
-		 struct svc_fh	*fhp,		\
-		 int		status),	\
-	TP_ARGS(rqstp, fhp, status))
+#define DEFINE_NFSD_FH_ERR_EVENT(name)			\
+DEFINE_EVENT_CONDITION(nfsd_fh_err_class, nfsd_##name,	\
+	TP_PROTO(struct svc_rqst *rqstp,		\
+		 struct svc_fh	*fhp,			\
+		 int		status),		\
+	TP_ARGS(rqstp, fhp, status),			\
+	TP_CONDITION(rqstp != NULL))
 
 DEFINE_NFSD_FH_ERR_EVENT(set_fh_dentry_badexport);
 DEFINE_NFSD_FH_ERR_EVENT(set_fh_dentry_badhandle);