On Thu, May 21, 2020 at 03:39:10PM -0700, Andrii Nakryiko wrote: > On Thu, May 21, 2020 at 12:18 PM Martin KaFai Lau <kafai@xxxxxx> wrote: > > > > This series allows the outer map to be updated with inner map in different > > size as long as it is safe (meaning the max_entries is not used in the > > verification time during prog load). > > > > Please see individual patch for details. > > > > Few thoughts: > > 1. You describe WHAT, but not necessarily WHY. Can you please > elaborate in descriptions what motivates these changes? There are cases where people want to update a bigger size inner map. I will update the cover letter. > 2. IMO, "capabilities" is word that way too strongly correlates with > Linux capabilities framework, it's just confusing. It's also more of a > property of a map type, than what map is capable of, but it's more > philosophical distinction, of course :) Sure. I can rename it to "property" > 3. I'm honestly not convinced that patch #1 qualifies as a clean up. I > think one specific check for types of maps that are not compatible > with map-in-map is just fine. Instead you are spreading this bit flags > into a long list of maps, most of which ARE compatible. but in one place and at the same time a new map type is added to bpf_types.h > It's just hard > to even see which ones are not compatible. I like current way better. There are multiple cases that people forgot to exclude a new map type from map-in-map in the first attempt and fix it up later. During the map-in-map implementation, this same concern was raised also about how to better exclude future map type from map-in-map since not all people has used map-in-map and it is easy to forget during review. Having it in one place in bpf_types.h will make this more obvious in my opinion. Patch 1 is an attempt to address this earlier concern in the map-in-map implementation. > 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. > 5. I also wonder if for those inner maps for which size doesn't > matter, maybe we should set max_elements to zero when setting > inner_meta to show that size doesn't matter? This is minor, though. > > > > Martin KaFai Lau (3): > > bpf: Clean up inner map type check > > bpf: Relax the max_entries check for inner map > > bpf: selftests: Add test for different inner map size > > > > include/linux/bpf.h | 18 +++++- > > include/linux/bpf_types.h | 64 +++++++++++-------- > > kernel/bpf/btf.c | 2 +- > > kernel/bpf/map_in_map.c | 12 ++-- > > kernel/bpf/syscall.c | 19 +++++- > > kernel/bpf/verifier.c | 2 +- > > .../selftests/bpf/prog_tests/btf_map_in_map.c | 12 ++++ > > .../selftests/bpf/progs/test_btf_map_in_map.c | 31 +++++++++ > > 8 files changed, 119 insertions(+), 41 deletions(-) > > > > -- > > 2.24.1 > >
