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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	David Miller <davem@davemloft.net>,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH bpf-next 2/3] libbpf: Support configurable pinning of maps from BTF annotations
Date: Wed, 23 Oct 2019 15:05:18 +0200	[thread overview]
Message-ID: <87a79rmx2p.fsf@toke.dk> (raw)
In-Reply-To: <6c0e6ebf-aebc-5e80-0e32-aa81857f3a74@iogearbox.net>

> You are worried about the case where an application should be able to
> unpin the map before loading a new one so it doesn't get reused?

No, I'm worried about the opposite: Someone running (the equivalent of)
'ip link set dev eth0 xdp off', and then wondering why all resources
aren't freed.

I do believe that the common case could be solved by a logic similar to
the one I proposed, though:

>> Hmm, but I guess it could do that anyway; so maybe what we need is just
>> a "try to find all pinned maps of this program" function? That could
>> then to something like:
>> 
>> - Get the maps IDs and names of all maps attached to that program from
>>    the kernel.
>> 
>> - Look for each map name in /sys/fs/bpf
>> 
>> - If a pinned map with the same name exists, compare the IDs, and unlink
>>    if they match
>> 
>> I don't suppose it'll be possible to do all that in a race-free manner,
>> but that would go for any use of unlink() unless I'm missing something?

  reply	other threads:[~2019-10-23 13:05 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-22 15:04 [PATCH bpf-next 0/3] libbpf: Support pinning of maps using 'pinning' BTF attribute Toke Høiland-Jørgensen
2019-10-22 15:04 ` [PATCH bpf-next 1/3] libbpf: Store map pin path in struct bpf_map Toke Høiland-Jørgensen
2019-10-22 17:37   ` Andrii Nakryiko
2019-10-22 18:13     ` Toke Høiland-Jørgensen
2019-10-22 18:23       ` Andrii Nakryiko
2019-10-22 18:45         ` Toke Høiland-Jørgensen
2019-10-22 18:49           ` Andrii Nakryiko
2019-10-22 19:06             ` Toke Høiland-Jørgensen
2019-10-23  4:43               ` Andrii Nakryiko
2019-10-22 15:04 ` [PATCH bpf-next 2/3] libbpf: Support configurable pinning of maps from BTF annotations Toke Høiland-Jørgensen
2019-10-22 18:20   ` Andrii Nakryiko
2019-10-22 18:57     ` Toke Høiland-Jørgensen
2019-10-23  4:40       ` Andrii Nakryiko
2019-10-23  8:53         ` Toke Høiland-Jørgensen
2019-10-23 12:30           ` Daniel Borkmann
2019-10-23 13:05             ` Toke Høiland-Jørgensen [this message]
2019-10-22 15:04 ` [PATCH bpf-next 3/3] libbpf: Add pin option to automount BPF filesystem before pinning Toke Høiland-Jørgensen
2019-10-22 18:28   ` Andrii Nakryiko
2019-10-22 19:04     ` Toke Høiland-Jørgensen
2019-10-23  4:58       ` Andrii Nakryiko
2019-10-23  8:58         ` Toke Høiland-Jørgensen

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