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From: John Fastabend <john.fastabend@gmail.com>
To: Andrii Nakryiko <andriin@fb.com>,
	bpf@vger.kernel.org, netdev@vger.kernel.org, ast@fb.com,
Cc: andrii.nakryiko@gmail.com, kernel-team@fb.com,
	Andrii Nakryiko <andriin@fb.com>
Subject: RE: [PATCH bpf-next] bpf: add bpf_link_new_file that doesn't install FD
Date: Tue, 10 Mar 2020 14:45:52 -0700	[thread overview]
Message-ID: <5e680a909371e_586d2b10f16785b8c9@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <20200309231051.1270337-1-andriin@fb.com>

Andrii Nakryiko wrote:
> Add bpf_link_new_file() API for cases when we need to ensure anon_inode is
> successfully created before we proceed with expensive BPF program attachment
> procedure, which will require equally (if not more so) expensive and
> potentially failing compensation detachment procedure just because anon_inode
> creation failed. This API allows to simplify code by ensuring first that
> anon_inode is created and after BPF program is attached proceed with
> fd_install() that can't fail.
> After anon_inode file is created, link can't be just kfree()'d anymore,
> because its destruction will be performed by deferred file_operations->release
> call. For this, bpf_link API required specifying two separate operations:
> release() and dealloc(), former performing detachment only, while the latter
> frees memory used by bpf_link itself. dealloc() needs to be specified, because
> struct bpf_link is frequently embedded into link type-specific container
> struct (e.g., struct bpf_raw_tp_link), so bpf_link itself doesn't know how to
> properly free the memory. In case when anon_inode file was successfully
> created, but subsequent BPF attachment failed, bpf_link needs to be marked as
> "defunct", so that file's release() callback will perform only memory
> deallocation, but no detachment.
> Convert raw tracepoint and tracing attachment to new API and eliminate
> detachment from error handling path.
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---


Acked-by: John Fastabend <john.fastabend@gmail.com>

  reply	other threads:[~2020-03-10 21:46 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-09 23:10 [PATCH bpf-next] bpf: add bpf_link_new_file that doesn't install FD Andrii Nakryiko
2020-03-10 21:45 ` John Fastabend [this message]
2020-03-11 13:22 ` Daniel Borkmann
2020-03-11 15:21   ` Andrii Nakryiko

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