Hi Kris,
On 01/11/2019 06:08 AM, Kris Van Hees wrote:
> Maybe I am missing something trivial here, but it looks to me that there is
> a leak of htab elements in htab_map_update_elem when you are updating an
> existing element. After the new element is linked into the bucket list, the
> following code snippet is found:
>
> if (l_old) {
> hlist_nulls_del_rcu(&l_old->hash_node);
> if (!htab_is_prealloc(htab))
> free_htab_elem(htab, l_old);
> }
>
> Nothing is done with l_old in the remainder of the function, and to me this
> looks like that element is be leaked if the htab is preallocated because we
> never add it to the free list. In fact, free_htab_elem() contains the very
> conditional that handles the two cases (preallocated vs non-preallocated.
In this case in alloc_htab_elem() we are swapping out the per-cpu extra element
with the existing one to avoid freelist_pop/push combination in order to have
a fast replace, meaning we cannot call free_htab_elem() on it like in plain
htab_map_delete_elem() case.
Thanks,
Daniel
