From: Daniel Borkmann <daniel@iogearbox.net>
To: Ming Lei <tom.leiming@gmail.com>,
linux-kernel@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org
Subject: Re: [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog
Date: Wed, 16 Dec 2015 00:35:28 +0100 [thread overview]
Message-ID: <5670A3C0.3080209@iogearbox.net> (raw)
In-Reply-To: <1450178464-27721-6-git-send-email-tom.leiming@gmail.com>
On 12/15/2015 12:21 PM, Ming Lei wrote:
...
> +static int htab_init_elems_allocator(struct bpf_htab *htab)
> +{
> + int ret = htab_pre_alloc_elems(htab);
> +
> + if (ret)
> + return ret;
> +
> + ret = percpu_ida_init(&htab->elems_pool, htab->map.max_entries);
> + if (ret)
> + htab_destroy_elems(htab);
> + return ret;
> +}
> +
> +static void htab_deinit_elems_allocator(struct bpf_htab *htab)
> +{
> + htab_destroy_elems(htab);
> + percpu_ida_destroy(&htab->elems_pool);
> +}
> +
> +static struct htab_elem *htab_alloc_elem(struct bpf_htab *htab)
> +{
> + int tag = percpu_ida_alloc(&htab->elems_pool, TASK_RUNNING);
> + struct htab_elem *elem;
> +
> + if (tag < 0)
> + return NULL;
> +
> + elem = htab->elems[tag];
> + elem->tag = tag;
> + return elem;
> +}
....
> @@ -285,12 +424,8 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
> * search will find it before old elem
> */
> hlist_add_head_rcu_lock(&l_new->hash_node, head);
> - if (l_old) {
> - hlist_del_rcu_lock(&l_old->hash_node);
> - kfree_rcu(l_old, rcu);
> - } else {
> - atomic_inc(&htab->count);
> - }
> + if (l_old)
> + htab_free_elem_rcu(htab, l_old);
> bit_spin_unlock(HLIST_LOCK_BIT, (unsigned long *)&head->first);
> raw_local_irq_restore(flags);
On a quick look, you are using the ida to keep track of elements, right? What happens
if you have a hash-table of max_entry size 1, fill that one slot and later on try to
replace it with a different element.
Old behaviour (htab->count) doesn't increase htab count and would allow the replacement
of that element to happen.
Looks like in your case, we'd get -E2BIG from htab_alloc_elem(), no? ... as preallocated
pool is already used up then?
next prev parent reply other threads:[~2015-12-15 23:35 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-15 11:20 [PATCH 0/6] bpf: hash: optimization Ming Lei
2015-12-15 11:20 ` [PATCH 1/6] bpf: hash: use atomic count Ming Lei
2015-12-15 11:21 ` [PATCH 2/6] hlist: prepare for supporting bit spinlock Ming Lei
2015-12-15 11:21 ` [PATCH 3/6] bpf: hash: move select_bucket() out of htab's spinlock Ming Lei
2015-12-15 11:21 ` [PATCH 4/6] bpf: hash: convert per-hashtable lock into per-bucket bit spinlock Ming Lei
2015-12-15 22:51 ` Alexei Starovoitov
2015-12-16 2:57 ` Ming Lei
[not found] ` <CAHbLzkpW_seTrs+WgFqsriH5uhG4LMY_jiYC0iRQ-LAdJFiUjw@mail.gmail.com>
2015-12-16 6:58 ` Ming Lei
2015-12-18 6:20 ` Alexei Starovoitov
2015-12-26 8:58 ` Ming Lei
2015-12-15 11:21 ` [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog Ming Lei
2015-12-15 23:10 ` Alexei Starovoitov
2015-12-15 23:42 ` Daniel Borkmann
2015-12-16 7:13 ` Ming Lei
2015-12-15 23:21 ` Daniel Borkmann
2015-12-15 23:35 ` Daniel Borkmann [this message]
2015-12-16 0:12 ` Daniel Borkmann
2015-12-15 11:21 ` [PATCH 6/6] bpf: hash: reorganize 'struct htab_elem' Ming Lei
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