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net: add napi_get_frags_check() helper

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This is a follow up of commit 3226b158e6
("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: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2022-06-08 09:04:38 -07:00 committed by Jakub Kicinski
parent ee2640df23
commit fd9ea57f4e
1 changed files with 18 additions and 0 deletions
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18
net/core/dev.c
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@ -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().