NFS: Add tracepoints for debugging NFS rename and sillyrename issues

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index e41dec5..dca7deb 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1909,6 +1909,7 @@
 		 new_dentry->d_parent->d_name.name, new_dentry->d_name.name,
 		 d_count(new_dentry));
 
+	trace_nfs_rename_enter(old_dir, old_dentry, new_dir, new_dentry);
 	/*
 	 * For non-directories, check whether the target is busy and if so,
 	 * make a copy of the dentry and then do a silly-rename. If the
@@ -1955,6 +1956,8 @@
 out:
 	if (rehash)
 		d_rehash(rehash);
+	trace_nfs_rename_exit(old_dir, old_dentry,
+			new_dir, new_dentry, error);
 	if (!error) {
 		if (new_inode != NULL)
 			nfs_drop_nlink(new_inode);