netdev - Re: [Patch bpf-next v4 1/3] bpf: introduce timeout hash map

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Date:   Mon, 18 Jan 2021 11:10:09 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Cc:     bpf <bpf@...r.kernel.org>, Cong Wang <cong.wang@...edance.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Dongdong Wang <wangdongdong.6@...edance.com>
Subject: Re: [Patch bpf-next v4 1/3] bpf: introduce timeout hash map

On Sat, Jan 16, 2021 at 8:22 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
> +static void htab_gc(struct work_struct *work)
> +{
> +       struct htab_elem *e, *tmp;
> +       struct llist_node *lhead;
> +       struct bpf_htab *htab;
> +       int i, count;
> +
> +       htab = container_of(work, struct bpf_htab, gc_work.work);
> +       lhead = llist_del_all(&htab->gc_list);
> +
> +       llist_for_each_entry_safe(e, tmp, lhead, gc_node) {
> +               unsigned long flags;
> +               struct bucket *b;
> +               u32 hash;
> +
> +               hash = e->hash;
> +               b = __select_bucket(htab, hash);
> +               if (htab_lock_bucket(htab, b, hash, &flags))
> +                       continue;
> +               hlist_nulls_del_rcu(&e->hash_node);
> +               atomic_set(&e->pending, 0);
> +               free_htab_elem(htab, e);
> +               htab_unlock_bucket(htab, b, hash, flags);
> +
> +               cond_resched();
> +       }
> +
> +       for (count = 0, i = 0; i < htab->n_buckets; i++) {

I just realized a followup fix is not folded into this patch, I
actually added a timestamp check here to avoid scanning the whole
table more frequently than once per second. It is clearly my mistake
to miss it when formatting this patchset.

I will send v5 after waiting for other feedback.

Thanks!