linux-kernel - Re: [PATCH v2 net-next 1/7] bpf: add 'flags' attribute to BPF_MAP_UPDATE

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Date:	Fri, 14 Nov 2014 13:11:11 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Alexei Starovoitov <ast@...mgrid.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Daniel Borkmann <dborkman@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>, linux-api@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next 1/7] bpf: add 'flags' attribute to
 BPF_MAP_UPDATE_ELEM command

On Do, 2014-11-13 at 17:36 -0800, Alexei Starovoitov wrote:
> the current meaning of BPF_MAP_UPDATE_ELEM syscall command is:
> either update existing map element or create a new one.
> Initially the plan was to add a new command to handle the case of
> 'create new element if it didn't exist', but 'flags' style looks
> cleaner and overall diff is much smaller (more code reused), so add 'flags'
> attribute to BPF_MAP_UPDATE_ELEM command with the following meaning:
>  #define BPF_ANY	0 /* create new element or update existing */
>  #define BPF_NOEXIST	1 /* create new element if it didn't exist */
>  #define BPF_EXIST	2 /* update existing element */

Would a cmpxchg-alike function be handy here?

Bye,
Hannes


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