From: Yonghong Song <yhs@fb.com>
To: Andrii Nakryiko <andrii@kernel.org>,
bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net
Cc: kernel-team@fb.com
Subject: Re: [PATCH v2 bpf-next 1/2] libbpf: make RINGBUF map size adjustments more eagerly
Date: Fri, 15 Jul 2022 16:38:33 -0700 [thread overview]
Message-ID: <ca57e143-5e4d-f915-9256-71481d97d81b@fb.com> (raw)
In-Reply-To: <20220715230952.2219271-1-andrii@kernel.org>
On 7/15/22 4:09 PM, Andrii Nakryiko wrote:
> Make libbpf adjust RINGBUF map size (rounding it up to closest power-of-2
> of page_size) more eagerly: during open phase when initializing the map
> and on explicit calls to bpf_map__set_max_entries().
>
> Such approach allows user to check actual size of BPF ringbuf even
> before it's created in the kernel, but also it prevents various edge
> case scenarios where BPF ringbuf size can get out of sync with what it
> would be in kernel. One of them (reported in [0]) is during an attempt
> to pin/reuse BPF ringbuf.
>
> Move adjust_ringbuf_sz() helper closer to its first actual use. The
> implementation of the helper is unchanged.
>
> Also make detection of whether bpf_object is already loaded more robust
> by checking obj->loaded explicitly, given that map->fd can be < 0 even
> if bpf_object is already loaded due to ability to disable map creation
> with bpf_map__set_autocreate(map, false).
>
> [0] Closes: https://github.com/libbpf/libbpf/pull/530
>
> Fixes: 0087a681fa8c ("libbpf: Automatically fix up BPF_MAP_TYPE_RINGBUF size, if necessary")
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
next prev parent reply other threads:[~2022-07-15 23:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-15 23:09 [PATCH v2 bpf-next 1/2] libbpf: make RINGBUF map size adjustments more eagerly Andrii Nakryiko
2022-07-15 23:09 ` [PATCH v2 bpf-next 2/2] selftests/bpf: test eager BPF ringbuf size adjustment logic Andrii Nakryiko
2022-07-15 23:39 ` Yonghong Song
2022-07-15 23:38 ` Yonghong Song [this message]
2022-07-19 17:10 ` [PATCH v2 bpf-next 1/2] libbpf: make RINGBUF map size adjustments more eagerly patchwork-bot+netdevbpf
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