netdev - Re: [PATCH bpf-next v4 3/4] bpf: cgroup: properly use bpf_prog

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Message-ID: <20190528214823.GC27847@tower.DHCP.thefacebook.com>
Date:   Tue, 28 May 2019 21:48:29 +0000
From:   Roman Gushchin <guro@...com>
To:     Stanislav Fomichev <sdf@...gle.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next v4 3/4] bpf: cgroup: properly use bpf_prog_array
 api

On Tue, May 28, 2019 at 02:14:43PM -0700, Stanislav Fomichev wrote:
> Now that we don't have __rcu markers on the bpf_prog_array helpers,
> let's use proper rcu_dereference_protected to obtain array pointer
> under mutex.
> 
> We also don't need __rcu annotations on cgroup_bpf.inactive since
> it's not read/updated concurrently.
> 
> v4:
> * drop cgroup_rcu_xyz wrappers and use rcu APIs directly; presumably
>   should be more clear to understand which mutex/refcount protects
>   each particular place
> 
> v3:
> * amend cgroup_rcu_dereference to include percpu_ref_is_dying;
>   cgroup_bpf is now reference counted and we don't hold cgroup_mutex
>   anymore in cgroup_bpf_release
> 
> v2:
> * replace xchg with rcu_swap_protected
> 
> Cc: Roman Gushchin <guro@...com>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>

Yeah, the looks even better.

Acked-by: Roman Gushchin <guro@...com>

Thanks!