nfsd: Add a tracepoint for errors in nfsd4_clone_file_range()

Since a clone error commit can cause the boot verifier to change,
we should trace those errors.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
[ cel: Addressed a checkpatch.pl splat in fs/nfsd/vfs.h ]
diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h
index b21b76e..9f56dcb 100644
--- a/fs/nfsd/vfs.h
+++ b/fs/nfsd/vfs.h
@@ -57,7 +57,8 @@ __be32          nfsd4_set_nfs4_label(struct svc_rqst *, struct svc_fh *,
 		    struct xdr_netobj *);
 __be32		nfsd4_vfs_fallocate(struct svc_rqst *, struct svc_fh *,
 				    struct file *, loff_t, loff_t, int);
-__be32		nfsd4_clone_file_range(struct nfsd_file *nf_src, u64 src_pos,
+__be32		nfsd4_clone_file_range(struct svc_rqst *rqstp,
+				       struct nfsd_file *nf_src, u64 src_pos,
 				       struct nfsd_file *nf_dst, u64 dst_pos,
 				       u64 count, bool sync);
 #endif /* CONFIG_NFSD_V4 */