linux-kernel - Re: [PATCH v4 1/4] bpf: Make the bpf_prog_array

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Message-ID: <55B9816B.5020801@plumgrid.com>
Date:	Wed, 29 Jul 2015 18:44:11 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Daniel Borkmann <daniel@...earbox.net>,
	Kaixu Xia <xiakaixu@...wei.com>, davem@...emloft.net,
	acme@...nel.org, mingo@...hat.com, a.p.zijlstra@...llo.nl,
	masami.hiramatsu.pt@...achi.com, jolsa@...nel.org
Cc:	wangnan0@...wei.com, linux-kernel@...r.kernel.org,
	pi3orama@....com, hekuang@...wei.com
Subject: Re: [PATCH v4 1/4] bpf: Make the bpf_prog_array_map more generic

On 7/29/15 4:17 PM, Daniel Borkmann wrote:
>> -    if (map->map_type == BPF_MAP_TYPE_PROG_ARRAY)
>> +    if (map->map_type >= BPF_MAP_TYPE_PROG_ARRAY)
>>           /* prog_array stores refcnt-ed bpf_prog pointers
>>            * release them all when user space closes prog_array_fd
>>            */
>> -        bpf_prog_array_map_clear(map);
>> +        bpf_fd_array_map_clear(map);
>
> When we are going to add a new map type to the eBPF framework that is not
> an fd_array_map thing, this assumption of map->map_type >=
> BPF_MAP_TYPE_PROG_ARRAY
> might not hold then ...

Also I think here changing == to >= is probably unnecessary.
prog_array needs to do it because of circular dependency
whereas perf_event_array cannot have it.
Even when we attach bpf prog to perf_event and then add it to
perf_event_array used by the same prog, right?
Please test such scenario just in case.

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