NFSv4.2: Add a tracepoint for listxattr

This can be defined as simply an NFS4_INODE_EVENT() since we don't have
the name of a specific xattr to list. This roughly matches readdir,
which also uses an NFS4_INODE_EVENT() tracepoint.
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs42proc.c

@@ -1320,6 +1320,7 @@ static ssize_t _nfs42_proc_listxattrs(struct inode *inode, void *buf,
 
 	ret = nfs4_call_sync(server->client, server, &msg, &arg.seq_args,
 	    &res.seq_res, 0);
+	trace_nfs4_listxattr(inode, ret);
 
 	if (ret >= 0) {
 		ret = res.copied;

fs/nfs/nfs4trace.h

@@ -2542,6 +2542,8 @@ DECLARE_EVENT_CLASS(nfs4_xattr_event,
 DEFINE_NFS4_XATTR_EVENT(nfs4_getxattr);
 DEFINE_NFS4_XATTR_EVENT(nfs4_setxattr);
 DEFINE_NFS4_XATTR_EVENT(nfs4_removexattr);
+
+DEFINE_NFS4_INODE_EVENT(nfs4_listxattr);
 #endif /* CONFIG_NFS_V4_2 */
 
 #endif /* CONFIG_NFS_V4_1 */