Re: [PATCHv5 bpf-next 5/9] ftrace: Add update_ftrace_direct_del function

Jiri Olsa
2025-12-19T09:27:48Z

On Wed, Dec 17, 2025 at 08:48:14PM -0500, Steven Rostedt wrote:
> On Mon, 15 Dec 2025 22:13:58 +0100
> Jiri Olsa <jolsa@kernel.org> wrote:
> > +/**
> > + * hash_sub - substracts @b from @a and returns the result
> > + * @a: struct ftrace_hash object
> > + * @b: struct ftrace_hash object
> > + *
> > + * Returns struct ftrace_hash object on success, NULL on error.
> > + */
> > +static struct ftrace_hash *hash_sub(struct ftrace_hash *a, struct ftrace_hash *b)
> > +{
> > + struct ftrace_func_entry *entry, *del;
> > + struct ftrace_hash *sub;
> > + int size, i;
> > +
> > + sub = alloc_and_copy_ftrace_hash(a->size_bits, a);
> > + if (!sub)
> > + goto error;
>
> Again, this can be just return NULL;

ok

>
> > +
> > + size = 1 << b->size_bits;
> > + for (i = 0; i < size; i++) {
>
> You can make this for (int i = 0; ...) too.

ok

>
> > + hlist_for_each_entry(entry, &b->buckets[i], hlist) {
> > + del = __ftrace_lookup_ip(sub, entry->ip);
> > + if (WARN_ON_ONCE(!del))
> > + goto error;
>
> And you can remove the error label here too:

ok

>
> if (WARN_ON_ONCE(!del)) {
> free_ftrace_hash(sub);
> return NULL;
> }
>
>
> > + remove_hash_entry(sub, del);
> > + kfree(del);
> > + }
> > + }
> > + return sub;
> > +
> > + error:
> > + free_ftrace_hash(sub);
> > + return NULL;
> > +}
> > +
> > +int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)
> > +{
> > + struct ftrace_hash *old_direct_functions = NULL, *new_direct_functions;
> > + struct ftrace_hash *old_filter_hash, *new_filter_hash = NULL;
> > + struct ftrace_func_entry *del, *entry;
>
> One variable per line.

ok

>
> > + unsigned long size, i;
> > + int err = -EINVAL;
> > +
> > + if (!hash_count(hash))
> > + return -EINVAL;
> > + if (check_direct_multi(ops))
> > + return -EINVAL;
> > + if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
> > + return -EINVAL;
> > + if (direct_functions == EMPTY_HASH)
> > + return -EINVAL;
> > +
> > + mutex_lock(&direct_mutex);
> > +
> > + old_filter_hash = ops->func_hash ? ops->func_hash->filter_hash : NULL;
> > +
> > + if (!hash_count(old_filter_hash))
> > + goto out_unlock;
> > +
> > + /* Make sure requested entries are already registered. */
> > + size = 1 << hash->size_bits;
> > + for (i = 0; i < size; i++) {
>
> for (int i = 0; ...)

ack

thanks,
jirka