linux-kernel - Re: [PATCHv2 perf/core 5/7] tools lib bpf: Add bpf_program_

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Message-ID: <CAPWQB7EWFE6DToMwTws6rUpnO49UYV1Rq-=0KV2ZioUf+dTjpg@mail.gmail.com>
Date:   Tue, 24 Jan 2017 17:16:52 -0800
From:   Joe Stringer <joe@....org>
To:     "Wangnan (F)" <wangnan0@...wei.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>, ast@...com,
        Daniel Borkmann <daniel@...earbox.net>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCHv2 perf/core 5/7] tools lib bpf: Add bpf_program__pin()

On 24 January 2017 at 17:06, Wangnan (F) <wangnan0@...wei.com> wrote:
>
>
> On 2017/1/25 9:04, Wangnan (F) wrote:
>>
>>
>>
>> On 2017/1/23 9:11, Joe Stringer wrote:
>>>
>>> Add a new API to pin a BPF program to the filesystem. The user can
>>> specify the path full path within a BPF filesystem to pin the program.
>>> Programs with multiple instances are pinned as 'foo', 'foo_1', 'foo_2',
>>> and so on.
>>>
>>> Signed-off-by: Joe Stringer <joe@....org>
>>> ---
>>> v2: Don't automount BPF filesystem
>>>      Split program, map, object pinning into separate APIs and separate
>>>      patches.
>>> ---
>
>
> [SNIP]
>
>>> +int bpf_program__pin(struct bpf_program *prog, const char *path)
>>
>>
>> In your next patch please let caller select one instance:
>>
>> int bpf_program__pin(struct bpf_program *prog, int instance, const char
>> *path)
>> (please choose a better name)
>>
>> Then your can wrap it with another function to pin all instances,
>> implement
>> naming schema (%s_%d) there.
>>
>> Then implement naming schema in bpf_object__pin like:
>>
>> %s/objectname_mapname
>> %s/objectname_progname_%d
>>
>
> Is it possible to use directory tree instead?
>
> %s/object/mapname
> %s/object/prog/instance

I don't think objects have names, so let's assume an object with two
program instances named foo, and one map named bar.

A call of bpf_object__pin(obj, "/sys/fs/bpf/myobj") would mount with
the following files and directories:
/sys/fs/bpf/myobj/foo/1
/sys/fs/bpf/myobj/foo/2
/sys/fs/bpf/myobj/bar

Alternatively, if you want to control exactly where you want the
progs/maps to be pinned, you can call eg
bpf_program__pin_instance(prog, "/sys/fs/bpf/wherever", 0) and that
instance will be mounted to /sys/fs/bpf/wherever, or alternatively
bpf_program__pin(prog, "/sys/fs/bpf/foo"), and you will end up with
/sys/fs/bpf/foo/{0,1}.

This looks pretty reasonable to me.