netdev - Re: [PATCH bpf] xdp: Handle device unregister for devmap

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Date:   Thu, 17 Oct 2019 12:28:05 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     daniel@...earbox.net, ast@...com, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH bpf] xdp: Handle device unregister for devmap_hash map type

Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp> writes:

> On 2019/10/16 22:28, Toke Høiland-Jørgensen wrote:
>> It seems I forgot to add handling of devmap_hash type maps to the device
>> unregister hook for devmaps. This omission causes devices to not be
>> properly released, which causes hangs.
>> 
>> Fix this by adding the missing handler.
>> 
>> Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
>> Reported-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
>
> Well, regarding 6f9d451ab1a3, I think that we want explicit "(u64)" cast
>
> @@ -97,6 +123,14 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
>         cost = (u64) dtab->map.max_entries * sizeof(struct bpf_dtab_netdev *);
>         cost += sizeof(struct list_head) * num_possible_cpus();
>
> +       if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
> +               dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);
> +
> +               if (!dtab->n_buckets) /* Overflow check */
> +                       return -EINVAL;
> +               cost += sizeof(struct hlist_head) * dtab->n_buckets;
>
>                                                     ^here
>
> +       }
> +
>         /* if map size is larger than memlock limit, reject it */
>         err = bpf_map_charge_init(&dtab->map.memory, cost);
>         if (err)
>
> like "(u64) dtab->map.max_entries * sizeof(struct bpf_dtab_netdev *)" does.
> Otherwise, on 32bits build, "sizeof(struct hlist_head) * dtab->n_buckets" can become 0.

Oh, right. I kinda assumed the compiler would be smart enough to figure
that out based on the type of the LHS; will send a separate fix for this.

-Toke