netdev - Re: [PATCH v3 net-next 12/14] af

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Date: Tue, 27 Feb 2024 12:25:56 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>, "David S. Miller"
	 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	 <kuba@...nel.org>
Cc: Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v3 net-next 12/14] af_unix: Detect dead SCC.

On Fri, 2024-02-23 at 13:40 -0800, Kuniyuki Iwashima wrote:
> When iterating SCC, we call unix_vertex_dead() for each vertex
> to check if the vertex is close()d and has no bridge to another
> SCC.
> 
> If both conditions are true for every vertex in SCC, we can
> execute garbage collection for all skb in the SCC.
> 
> The actual garbage collection is done in the following patch,
> replacing the old implementation.
> 
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---
>  net/unix/garbage.c | 37 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/net/unix/garbage.c b/net/unix/garbage.c
> index 0eb1610c96d7..060e81be3614 100644
> --- a/net/unix/garbage.c
> +++ b/net/unix/garbage.c
> @@ -288,6 +288,32 @@ void unix_destroy_fpl(struct scm_fp_list *fpl)
>  	unix_free_vertices(fpl);
>  }
>  
> +static bool unix_vertex_dead(struct unix_vertex *vertex)
> +{
> +	struct unix_edge *edge;
> +	struct unix_sock *u;
> +	long total_ref;
> +
> +	list_for_each_entry(edge, &vertex->edges, vertex_entry) {
> +		struct unix_vertex *next_vertex = unix_edge_successor(edge);
> +
> +		if (!next_vertex)
> +			return false;
> +
> +		if (next_vertex->scc_index != vertex->scc_index)
> +			return false;
> +	}
> +
> +	edge = list_first_entry(&vertex->edges, typeof(*edge), vertex_entry);
> +	u = edge->predecessor;
> +	total_ref = file_count(u->sk.sk_socket->file);
> +
> +	if (total_ref != vertex->out_degree)
> +		return false;
> +
> +	return true;
> +}
> +
>  static bool unix_scc_cyclic(struct list_head *scc)
>  {
>  	struct unix_vertex *vertex;
> @@ -350,6 +376,7 @@ static void __unix_walk_scc(struct unix_vertex *vertex)
>  
>  	if (vertex->index == vertex->scc_index) {
>  		struct list_head scc;
> +		bool dead = true;

Very minor nit: the above variable 'sounds' alike referring to the
current vertex, while instead it tracks a global status, what about
'all_dead' or 'gc_all'?

Thanks,

Paolo