From: John Fastabend <john.fastabend@gmail.com>
To: Martynas Pumputis <m@lambda.lt>, bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, m@lambda.lt
Subject: RE: [PATCH v2 bpf-next] libbpf: fix reuse of pinned map on older kernel
Date: Mon, 12 Jul 2021 12:19:52 -0700 [thread overview]
Message-ID: <60ec95d89c590_50e1d208fc@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <20210712125552.58705-1-m@lambda.lt>
Martynas Pumputis wrote:
> When loading a BPF program with a pinned map, the loader checks whether
> the pinned map can be reused, i.e. their properties match. To derive
> such of the pinned map, the loader invokes BPF_OBJ_GET_INFO_BY_FD and
> then does the comparison.
>
> Unfortunately, on < 4.12 kernels the BPF_OBJ_GET_INFO_BY_FD is not
> available, so loading the program fails with the following error:
>
> libbpf: failed to get map info for map FD 5: Invalid argument
> libbpf: couldn't reuse pinned map at
> '/sys/fs/bpf/tc/globals/cilium_call_policy': parameter
> mismatch"
> libbpf: map 'cilium_call_policy': error reusing pinned map
> libbpf: map 'cilium_call_policy': failed to create:
> Invalid argument(-22)
> libbpf: failed to load object 'bpf_overlay.o'
>
> To fix this, fallback to derivation of the map properties via
> /proc/$PID/fdinfo/$MAP_FD if BPF_OBJ_GET_INFO_BY_FD fails with EINVAL,
> which can be used as an indicator that the kernel doesn't support
> the latter.
>
> Signed-off-by: Martynas Pumputis <m@lambda.lt>
> ---
LGTM.
Acked-by: John Fastabend <john.fastabend@gmail.com>
prev parent reply other threads:[~2021-07-12 19:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-12 12:55 [PATCH v2 bpf-next] libbpf: fix reuse of pinned map on older kernel Martynas Pumputis
2021-07-12 19:19 ` John Fastabend [this message]
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