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

On Thu, May 21, 2020 at 4:16 PM Alexei Starovoitov
[off-list ref] wrote:

On Thu, May 21, 2020 at 04:10:36PM -0700, Andrii Nakryiko wrote:

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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.

Consolidation is good, but then we hopefully do it for all aspects of
maps that currently have ad-hoc checks spread across a lot of places.
Just looking at map_lookup_elem in syscall.c makes me wanna cry, for
example :) I'll reply on another thread where Daniel proposed putting
everything into ops, I like that better.

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?