linux-kernel - [RFC PATCHv2 net-next 1/3] net/udp: Add a new struct for hash2 slot

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Message-ID: <20240924123017.1688277-1-gur.stavi@huawei.com>
Date: Tue, 24 Sep 2024 15:30:17 +0300
From: Gur Stavi <gur.stavi@...wei.com>
To: <lulie@...ux.alibaba.com>
CC: <antony.antony@...unet.com>, <davem@...emloft.net>, <dsahern@...nel.org>,
	<dust.li@...ux.alibaba.com>, <edumazet@...gle.com>,
	<fred.cc@...baba-inc.com>, <jakub@...udflare.com>, <kuba@...nel.org>,
	<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
	<pabeni@...hat.com>, <steffen.klassert@...unet.com>,
	<willemdebruijn.kernel@...il.com>, <yubing.qiuyubing@...baba-inc.com>
Subject: [RFC PATCHv2 net-next 1/3] net/udp: Add a new struct for hash2 slot

> + *	@hslot:	basic hash slot
> + *	@hash4_cnt: number of sockets in hslot4 of the same (local port, local address)
> + */
> +struct udp_hslot_main {
> +	struct udp_hslot	hslot; /* must be the first member */
> +	u32			hash4_cnt;
> +} __aligned(2 * sizeof(long));
> +#define UDP_HSLOT_MAIN(__hslot) ((struct udp_hslot_main *)(__hslot))

Wouldn't container_of be more suitable than brutal cast?

> @@ -91,7 +110,7 @@ static inline struct udp_hslot *udp_hashslot(struct udp_table *table,
>  static inline struct udp_hslot *udp_hashslot2(struct udp_table *table,
>  					      unsigned int hash)
>  {
> -	return &table->hash2[hash & table->mask];
> +	return (struct udp_hslot *)udp_hashslot2_main(table, hash);

Why cast and not use ->hslot. Preferably with a local variable?

> @@ -3438,16 +3436,17 @@ void __init udp_table_init(struct udp_table *table, const char *name)
>  					      UDP_HTABLE_SIZE_MIN,
>  					      UDP_HTABLE_SIZE_MAX);
>
> -	table->hash2 = table->hash + (table->mask + 1);
> +	table->hash2 = UDP_HSLOT_MAIN(table->hash + (table->mask + 1));

Wouldn't it be simpler to just cast to void? It is pure pointer
arithmetic where type checking is meaningless.
(void *)(table->hash + (table->mask + 1))
I realize now why UDP_HSLOT_MAIN couldn't use container_of but it
just demonstrates how convoluted this is.