netdev - Re: [PATCH bpf-next 1/2] xsk: store struct xdp_sock as a flexible array member of the XSKMAP

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Message-ID: <20191024131222.70ca703b@cakuba.hsd1.ca.comcast.net>
Date:   Thu, 24 Oct 2019 13:12:22 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Toke Høiland-Jørgensen 
        <toke@...hat.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...com,
        daniel@...earbox.net, magnus.karlsson@...el.com,
        bjorn.topel@...el.com
Subject: Re: [PATCH bpf-next 1/2] xsk: store struct xdp_sock as a flexible
 array member of the XSKMAP

On Thu, 24 Oct 2019 09:19:30 +0200, Maciej Fijalkowski wrote:
> @@ -92,44 +94,36 @@ static struct bpf_map *xsk_map_alloc(union bpf_attr *attr)
>  	    attr->map_flags & ~(BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY))
>  		return ERR_PTR(-EINVAL);
>  
> -	m = kzalloc(sizeof(*m), GFP_USER);
> -	if (!m)
> -		return ERR_PTR(-ENOMEM);
> +	max_entries = attr->max_entries;
>  
> -	bpf_map_init_from_attr(&m->map, attr);
> -	spin_lock_init(&m->lock);
> +	size = sizeof(*m) + max_entries * sizeof(m->xsk_map[0]);

Maybe the array_size() I suggested to Toke was disputable, but this is
such an struct_size()...

Otherwise you probably need an explicit (u64) cast?