nfsd: Add tracing to nfsd_set_fh_dentry()

Add tracing to allow us to figure out where any stale filehandle issues
may be originating from.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfsfh.c

@@ -14,6 +14,7 @@
 #include "nfsd.h"
 #include "vfs.h"
 #include "auth.h"
+#include "trace.h"
 
 #define NFSDDBG_FACILITY		NFSDDBG_FH
 
@@ -209,11 +210,14 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
 	}
 
 	error = nfserr_stale;
-	if (PTR_ERR(exp) == -ENOENT)
-		return error;
+	if (IS_ERR(exp)) {
+		trace_nfsd_set_fh_dentry_badexport(rqstp, fhp, PTR_ERR(exp));
+
+		if (PTR_ERR(exp) == -ENOENT)
+			return error;
 
-	if (IS_ERR(exp))
 		return nfserrno(PTR_ERR(exp));
+	}
 
 	if (exp->ex_flags & NFSEXP_NOSUBTREECHECK) {
 		/* Elevate privileges so that the lack of 'r' or 'x'
@@ -267,6 +271,9 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
 		dentry = exportfs_decode_fh(exp->ex_path.mnt, fid,
 				data_left, fileid_type,
 				nfsd_acceptable, exp);
+		if (IS_ERR_OR_NULL(dentry))
+			trace_nfsd_set_fh_dentry_badhandle(rqstp, fhp,
+					dentry ?  PTR_ERR(dentry) : -ESTALE);
 	}
 	if (dentry == NULL)
 		goto out;

fs/nfsd/trace.h

@@ -50,6 +50,36 @@ TRACE_EVENT(nfsd_compound_status,
 		__get_str(name), __entry->status)
 )
 
+DECLARE_EVENT_CLASS(nfsd_fh_err_class,
+	TP_PROTO(struct svc_rqst *rqstp,
+		 struct svc_fh	*fhp,
+		 int		status),
+	TP_ARGS(rqstp, fhp, status),
+	TP_STRUCT__entry(
+		__field(u32, xid)
+		__field(u32, fh_hash)
+		__field(int, status)
+	),
+	TP_fast_assign(
+		__entry->xid = be32_to_cpu(rqstp->rq_xid);
+		__entry->fh_hash = knfsd_fh_hash(&fhp->fh_handle);
+		__entry->status = status;
+	),
+	TP_printk("xid=0x%08x fh_hash=0x%08x status=%d",
+		  __entry->xid, __entry->fh_hash,
+		  __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_NFSD_FH_ERR_EVENT(set_fh_dentry_badexport);
+DEFINE_NFSD_FH_ERR_EVENT(set_fh_dentry_badhandle);
+
 DECLARE_EVENT_CLASS(nfsd_io_class,
 	TP_PROTO(struct svc_rqst *rqstp,
 		 struct svc_fh	*fhp,