On Wed, Nov 29, 2023 at 7:17 AM Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
>
> On Mon, Nov 27, 2023 at 03:45:57PM -0800, Nhat Pham wrote:
> > static void shrink_worker(struct work_struct *w)
> > {
> > struct zswap_pool *pool = container_of(w, typeof(*pool),
> > shrink_work);
> > + struct mem_cgroup *memcg;
> > int ret, failures = 0;
> >
> > + /* global reclaim will select cgroup in a round-robin fashion. */
> > do {
> > - ret = zswap_reclaim_entry(pool);
> > - if (ret) {
> > - zswap_reject_reclaim_fail++;
> > - if (ret != -EAGAIN)
> > - break;
> > + spin_lock(&zswap_pools_lock);
> > + memcg = pool->next_shrink =
> > + mem_cgroup_iter_online(NULL, pool->next_shrink, NULL, true);
> > +
> > + /* full round trip */
> > + if (!memcg) {
> > + spin_unlock(&zswap_pools_lock);
> > if (++failures == MAX_RECLAIM_RETRIES)
> > break;
> > +
> > + goto resched;
> > }
> > +
> > + /*
> > + * Acquire an extra reference to the iterated memcg in case the
> > + * original reference is dropped by the zswap offlining callback.
> > + */
> > + css_get(&memcg->css);
>
> struct mem_cgroup isn't defined when !CONFIG_MEMCG. This needs a
> mem_cgroup_get() wrapper and a dummy function for no-memcg builds.
I got this exact same issue a couple of versions ago, but it was
hidden behind another helper function which can be implemented as a
no-op in the case of !CONFIG_MEMCG, so I forgot about it until now. It
always strikes me a bit weird that we have mem_cgroup_put() but not an
equivalent get - let me correct that.
>
> With that fixed, though, everything else looks good to me:
>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Thanks for the review, Johannes!
