Re: [net-next PATCH 1/5] net: Do not record sender_cpu as napi_id in socket receive paths
From: Eric Dumazet <hidden>
Date: 2017-03-16 22:05:47
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On Thu, 2017-03-16 at 11:32 -0700, Alexander Duyck wrote:
quoted hunk ↗ jump to hunk
From: Sridhar Samudrala <sridhar.samudrala@intel.com> Fix sk_mark_napi_id() and sk_mark_napi_id_once() to set sk_napi_id only if skb->napi_id is a valid value. This happens in loopback paths where skb->napi_id is not updated in rx path and holds sender_cpu that is set in xmit path. Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com> Signed-off-by: Alexander Duyck <redacted> --- include/net/busy_poll.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h index c0452de83086..67991635953e 100644 --- a/include/net/busy_poll.h +++ b/include/net/busy_poll.h@@ -116,7 +116,8 @@ static inline bool sk_busy_loop(struct sock *sk, int nonblock) static inline void sk_mark_napi_id(struct sock *sk, const struct sk_buff *skb) { #ifdef CONFIG_NET_RX_BUSY_POLL - sk->sk_napi_id = skb->napi_id; + if (skb->napi_id > (u32)NR_CPUS) + sk->sk_napi_id = skb->napi_id; #endif }@@ -125,7 +126,7 @@ static inline void sk_mark_napi_id_once(struct sock *sk, const struct sk_buff *skb) { #ifdef CONFIG_NET_RX_BUSY_POLL - if (!sk->sk_napi_id) + if (!sk->sk_napi_id && (skb->napi_id > (u32)NR_CPUS)) sk->sk_napi_id = skb->napi_id; #endif }
It is not clear why this patch is needed . What you describe here is the case we might receive packets for a socket coming from different interfaces ? If skb->napi_id is a sender_cpu, why should we prevent overwriting the sk_napi_id with it, knowing that busy polling will simply ignore the invalid value ? Do not get me wrong : I simply try to understand why the test about napi_id validity is now done twice : 1) At the time we are writing into sk->sk_napi_id 2) At busy polling time when we read sk->sk_napi_id