On Wed, 2010-07-21 at 22:31 +0900, KOSAKI Motohiro wrote: > Hi Steven, > if (ac) > trace_ext4_mb_release_group_pa(ac, pa); > > But, I don't think this is proper fix because we don't want any overhead > if the tracepoint is disabled. > > So, How do we check NULL in TP_fast_assign()? You could do: TP_fast_assign( if (ac) { __entry->dev = ac->ac_sb->s_dev; __entry->ino = ac->ac_inode->i_ino; __entry->pa_pstart = pa->pa_pstart; __entry->pa_len = pa->pa_len; } ), But this just makes the __entry null and wastes the ring buffer. I may be able to add a __discard_entry that may help. Then we could do something like this: if (ac) { __entry->dev = ac->ac_sb->s_dev; __entry->ino = ac->ac_inode->i_ino; __entry->pa_pstart = pa->pa_pstart; __entry->pa_len = pa->pa_len; } else __discard_entry; Does this seem reasonable? But for now, the wasting the entry seems to be the only choice we have, or to do as you suggested and have the "if (ac) trace_...", but I don't like that. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html