Commit fd9ea57f authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

net: add napi_get_frags_check() helper 



This is a follow up of commit 3226b158
("net: avoid 32 x truesize under-estimation for tiny skbs")

When/if we increase MAX_SKB_FRAGS, we better make sure
the old bug will not come back.

Adding a check in napi_get_frags() would be costly,
even if using DEBUG_NET_WARN_ON_ONCE().

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent ee2640df

net/core/dev.c

+18 −0
Original line number Diff line number Diff line
@@ -6351,6 +6351,23 @@ int dev_set_threaded(struct net_device *dev, bool threaded) 
}

EXPORT_SYMBOL(dev_set_threaded);



/* Double check that napi_get_frags() allocates skbs with

 * skb->head being backed by slab, not a page fragment.

 * This is to make sure bug fixed in 3226b158e67c

 * ("net: avoid 32 x truesize under-estimation for tiny skbs")

 * does not accidentally come back.

 */

static void napi_get_frags_check(struct napi_struct *napi)

{

	struct sk_buff *skb;



	local_bh_disable();

	skb = napi_get_frags(napi);

	WARN_ON_ONCE(skb && skb->head_frag);

	napi_free_frags(napi);

	local_bh_enable();

}



void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,

			   int (*poll)(struct napi_struct *, int), int weight)

{
@@ -6378,6 +6395,7 @@ void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi, 
	set_bit(NAPI_STATE_NPSVC, &napi->state);

	list_add_rcu(&napi->dev_list, &dev->napi_list);

	napi_hash_add(napi);

	napi_get_frags_check(napi);

	/* Create kthread for this napi if dev->threaded is set.

	 * Clear dev->threaded if kthread creation failed so that

	 * threaded mode will not be enabled in napi_enable().