netdev - Re: [PATCH][net-next][v2] net: convert gro

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Date:   Mon, 16 Jul 2018 16:40:52 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Li RongQing <lirongqing@...du.com>, netdev@...r.kernel.org
Cc:     edumazet@...gle.com, sbrivio@...hat.com
Subject: Re: [PATCH][net-next][v2] net: convert gro_count to bitmask



On 07/12/2018 11:41 PM, Li RongQing wrote:
> gro_hash size is 192 bytes, and uses 3 cache lines, if there is few

		 */
> @@ -9264,6 +9273,9 @@ static struct hlist_head * __net_init netdev_create_hash(void)
>  /* Initialize per network namespace state */
>  static int __net_init netdev_init(struct net *net)
>  {
> +	BUILD_BUG_ON(GRO_HASH_BUCKETS >
> +			FIELD_SIZEOF(struct napi_struct, gro_bitmask));
> +

Sorry for the delay (patch is already merged)

This looks wrong to me. 

FIELD_SIZEOF() is in bytes not bits.

I guess we could either use BITS_PER_LONG or :

diff --git a/net/core/dev.c b/net/core/dev.c
index c883b17ee0fe2c8a7ca2f2867560ba74004790a7..4f8b92d81d107fc9acd2499297435cbd9e9b5c67 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9282,7 +9282,7 @@ static struct hlist_head * __net_init netdev_create_hash(void)
 static int __net_init netdev_init(struct net *net)
 {
        BUILD_BUG_ON(GRO_HASH_BUCKETS >
-                       FIELD_SIZEOF(struct napi_struct, gro_bitmask));
+                    8 * FIELD_SIZEOF(struct napi_struct, gro_bitmask));
 
        if (net != &init_net)
                INIT_LIST_HEAD(&net->dev_base_head);