netdev - Re: [PATCH bpf-next 0/3] bpf: Allow inner map with different max

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Date:   Thu, 21 May 2020 16:16:18 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Martin KaFai Lau <kafai@...com>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next 0/3] bpf: Allow inner map with different
 max_entries

On Thu, May 21, 2020 at 04:10:36PM -0700, Andrii Nakryiko wrote:
> > > 4. Then for size check change, again, it's really much simpler and
> > > cleaner just to have a special case in check in bpf_map_meta_equal for
> > > cases where map size matters.
> > It may be simpler but not necessary less fragile for future map type.
> >
> > I am OK for removing patch 1 and just check for a specific
> > type in patch 2 but I think it is fragile for future map
> > type IMO.
> 
> Well, if we think that the good default needs to be to check size,
> then similar to above, explicitly list stuff that *does not* follow
> the default, i.e., maps that don't want max_elements verification. My
> point still stands.

I think consoldating map properties in bpf_types.h is much cleaner
and less error prone.
I'd only like to tweak the macro in patch 1 to avoid explicit ", 0)".
Can BPF_MAP_TYPE() macro stay as-is and additional macro introduced
for maps with properties ? BPF_MAP_TYPE_FL() ?
Or do some macro magic that the same macro can be used with 2 and 3 args?