Re: [PATCH v2 11/27] ftrace: Allow subops filtering to be modified

Steven Rostedt
2024-06-03T14:51:47Z

On Mon, 3 Jun 2024 11:37:23 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:

> On Sat, 01 Jun 2024 23:37:55 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> [...]
> >
> > +static int ftrace_hash_move_and_update_subops(struct ftrace_ops *subops,
> > + struct ftrace_hash **orig_subhash,
> > + struct ftrace_hash *hash,
> > + int enable)
> > +{
> > + struct ftrace_ops *ops = subops->managed;
> > + struct ftrace_hash **orig_hash;
> > + struct ftrace_hash *save_hash;
> > + struct ftrace_hash *new_hash;
> > + int ret;
> > +
> > + /* Manager ops can not be subops (yet) */
> > + if (WARN_ON_ONCE(!ops || ops->flags & FTRACE_OPS_FL_SUBOP))
> > + return -EINVAL;
>
> This does return if ops->flags & FTRACE_OPS_FL_SUBOP, but --> (1)

Yes, because what is passed in is "subops" and "ops" is subops->managed.

>
> > +
> > + /* Move the new hash over to the subops hash */
> > + save_hash = *orig_subhash;
> > + *orig_subhash = __ftrace_hash_move(hash);
> > + if (!*orig_subhash) {
> > + *orig_subhash = save_hash;
> > + return -ENOMEM;
> > + }
> > +
> > + /* Create a new_hash to hold the ops new functions */
> > + if (enable) {
> > + orig_hash = &ops->func_hash->filter_hash;
> > + new_hash = append_hashes(ops);
> > + } else {
> > + orig_hash = &ops->func_hash->notrace_hash;
> > + new_hash = intersect_hashes(ops);
> > + }
> > +
> > + /* Move the hash over to the new hash */
> > + ret = ftrace_hash_move_and_update_ops(ops, orig_hash, new_hash, enable);
>
> This also a bit wired to me. maybe we need simple version like
>
> `__ftrace_hash_move_and_update_ops()`
>
> And call it from ftrace_hash_move_and_update_ops() and here?

We could do that. I almost did due to other issues but I reworked the code
where I didn't need to.

>
> > +
> > + free_ftrace_hash(new_hash);
> > +
> > + if (ret) {
> > + /* Put back the original hash */
> > + free_ftrace_hash_rcu(*orig_subhash);
> > + *orig_subhash = save_hash;
> > + } else {
> > + free_ftrace_hash_rcu(save_hash);
> > + }
> > + return ret;
> > +}
> > +
> > +
> > static u64 ftrace_update_time;
> > unsigned long ftrace_update_tot_cnt;
> > unsigned long ftrace_number_of_pages;
> > @@ -4770,8 +4823,33 @@ static int ftrace_hash_move_and_update_ops(struct ftrace_ops *ops,
> > {
> > struct ftrace_ops_hash old_hash_ops;
> > struct ftrace_hash *old_hash;
> > + struct ftrace_ops *op;
> > int ret;
> >
> > + if (ops->flags & FTRACE_OPS_FL_SUBOP)
> > + return ftrace_hash_move_and_update_subops(ops, orig_hash, hash, enable);
>
> (1) This calls ftrace_hash_move_and_update_subops() if ops->flags & FTRACE_OPS_FL_SUBOP ?

Yes, because ops turns into subops, and the ops above it is its manager ops.

-- Steve