Re: [PATCH bpf-next v2 3/7] bpf: add MAP_LOOKUP_AND_DELETE_ELEM syscall

On Wed, Oct 10, 2018 at 05:50:01PM -0500, Mauricio Vasquez wrote:

quoted

quoted

Does it make sense to you?

I reread the other patch, and found it does NOT use the following logic for
queue and stack:

                rcu_read_lock();
                ptr = map->ops->map_lookup_and_delete_elem(map, key);
                if (ptr)
                        memcpy(value, ptr, value_size);

I guess this part is not used at all? Can we just remove it?

Thanks,
Song

This is the base code for map_lookup_and_delete support, it is not used in
queue/stack maps.

I think we can leave it there, so when somebody implements lookup_and_delete
for other maps doesn't have to care about implementing also this.

The code looks useful to me, but I also agree with Song. And in the kernel
we don't typically add 'almost dead code'.
May be provide an implementation of the lookup_and_delete for hash map
so it's actually used ?
imo it would be a useful feature to have for hash map and will clarify
the intent of it for all other maps and for stack/queue in particular.