From c80794323e82ac6ab45052ebba5757ce47b4b588 Mon Sep 17 00:00:00 2001 From: Maxim Mikityanskiy Date: Tue, 21 Jan 2020 15:09:40 +0000 Subject: net: Fix packet reordering caused by GRO and listified RX cooperation Commit 323ebb61e32b ("net: use listified RX for handling GRO_NORMAL skbs") introduces batching of GRO_NORMAL packets in napi_frags_finish, and commit 6570bc79c0df ("net: core: use listified Rx for GRO_NORMAL in napi_gro_receive()") adds the same to napi_skb_finish. However, dev_gro_receive (that is called just before napi_{frags,skb}_finish) can also pass skbs to the networking stack: e.g., when the GRO session is flushed, napi_gro_complete is called, which passes pp directly to netif_receive_skb_internal, skipping napi->rx_list. It means that the packet stored in pp will be handled by the stack earlier than the packets that arrived before, but are still waiting in napi->rx_list. It leads to TCP reorderings that can be observed in the TCPOFOQueue counter in netstat. This commit fixes the reordering issue by making napi_gro_complete also use napi->rx_list, so that all packets going through GRO will keep their order. In order to keep napi_gro_flush working properly, gro_normal_list calls are moved after the flush to clear napi->rx_list. iwlwifi calls napi_gro_flush directly and does the same thing that is done by gro_normal_list, so the same change is applied there: napi_gro_flush is moved to be before the flush of napi->rx_list. A few other drivers also use napi_gro_flush (brocade/bna/bnad.c, cortina/gemini.c, hisilicon/hns3/hns3_enet.c). The first two also use napi_complete_done afterwards, which performs the gro_normal_list flush, so they are fine. The latter calls napi_gro_receive right after napi_gro_flush, so it can end up with non-empty napi->rx_list anyway. Fixes: 323ebb61e32b ("net: use listified RX for handling GRO_NORMAL skbs") Signed-off-by: Maxim Mikityanskiy Cc: Alexander Lobakin Cc: Edward Cree Acked-by: Alexander Lobakin Acked-by: Saeed Mahameed Acked-by: Edward Cree Signed-off-by: David S. Miller --- drivers/net/wireless/intel/iwlwifi/pcie/rx.c | 4 +- net/core/dev.c | 64 ++++++++++++++-------------- 2 files changed, 35 insertions(+), 33 deletions(-) diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c index 452da44a21e0..f0b8ff67a1bc 100644 --- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c +++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c @@ -1529,13 +1529,13 @@ out: napi = &rxq->napi; if (napi->poll) { + napi_gro_flush(napi, false); + if (napi->rx_count) { netif_receive_skb_list(&napi->rx_list); INIT_LIST_HEAD(&napi->rx_list); napi->rx_count = 0; } - - napi_gro_flush(napi, false); } iwl_pcie_rxq_restock(trans, rxq); diff --git a/net/core/dev.c b/net/core/dev.c index e82e9b82dfd9..cca03914108a 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5491,9 +5491,29 @@ static void flush_all_backlogs(void) put_online_cpus(); } +/* Pass the currently batched GRO_NORMAL SKBs up to the stack. */ +static void gro_normal_list(struct napi_struct *napi) +{ + if (!napi->rx_count) + return; + netif_receive_skb_list_internal(&napi->rx_list); + INIT_LIST_HEAD(&napi->rx_list); + napi->rx_count = 0; +} + +/* Queue one GRO_NORMAL SKB up for list processing. If batch size exceeded, + * pass the whole batch up to the stack. + */ +static void gro_normal_one(struct napi_struct *napi, struct sk_buff *skb) +{ + list_add_tail(&skb->list, &napi->rx_list); + if (++napi->rx_count >= gro_normal_batch) + gro_normal_list(napi); +} + INDIRECT_CALLABLE_DECLARE(int inet_gro_complete(struct sk_buff *, int)); INDIRECT_CALLABLE_DECLARE(int ipv6_gro_complete(struct sk_buff *, int)); -static int napi_gro_complete(struct sk_buff *skb) +static int napi_gro_complete(struct napi_struct *napi, struct sk_buff *skb) { struct packet_offload *ptype; __be16 type = skb->protocol; @@ -5526,7 +5546,8 @@ static int napi_gro_complete(struct sk_buff *skb) } out: - return netif_receive_skb_internal(skb); + gro_normal_one(napi, skb); + return NET_RX_SUCCESS; } static void __napi_gro_flush_chain(struct napi_struct *napi, u32 index, @@ -5539,7 +5560,7 @@ static void __napi_gro_flush_chain(struct napi_struct *napi, u32 index, if (flush_old && NAPI_GRO_CB(skb)->age == jiffies) return; skb_list_del_init(skb); - napi_gro_complete(skb); + napi_gro_complete(napi, skb); napi->gro_hash[index].count--; } @@ -5641,7 +5662,7 @@ static void gro_pull_from_frag0(struct sk_buff *skb, int grow) } } -static void gro_flush_oldest(struct list_head *head) +static void gro_flush_oldest(struct napi_struct *napi, struct list_head *head) { struct sk_buff *oldest; @@ -5657,7 +5678,7 @@ static void gro_flush_oldest(struct list_head *head) * SKB to the chain. */ skb_list_del_init(oldest); - napi_gro_complete(oldest); + napi_gro_complete(napi, oldest); } INDIRECT_CALLABLE_DECLARE(struct sk_buff *inet_gro_receive(struct list_head *, @@ -5733,7 +5754,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff if (pp) { skb_list_del_init(pp); - napi_gro_complete(pp); + napi_gro_complete(napi, pp); napi->gro_hash[hash].count--; } @@ -5744,7 +5765,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff goto normal; if (unlikely(napi->gro_hash[hash].count >= MAX_GRO_SKBS)) { - gro_flush_oldest(gro_head); + gro_flush_oldest(napi, gro_head); } else { napi->gro_hash[hash].count++; } @@ -5802,26 +5823,6 @@ struct packet_offload *gro_find_complete_by_type(__be16 type) } EXPORT_SYMBOL(gro_find_complete_by_type); -/* Pass the currently batched GRO_NORMAL SKBs up to the stack. */ -static void gro_normal_list(struct napi_struct *napi) -{ - if (!napi->rx_count) - return; - netif_receive_skb_list_internal(&napi->rx_list); - INIT_LIST_HEAD(&napi->rx_list); - napi->rx_count = 0; -} - -/* Queue one GRO_NORMAL SKB up for list processing. If batch size exceeded, - * pass the whole batch up to the stack. - */ -static void gro_normal_one(struct napi_struct *napi, struct sk_buff *skb) -{ - list_add_tail(&skb->list, &napi->rx_list); - if (++napi->rx_count >= gro_normal_batch) - gro_normal_list(napi); -} - static void napi_skb_free_stolen_head(struct sk_buff *skb) { skb_dst_drop(skb); @@ -6200,8 +6201,6 @@ bool napi_complete_done(struct napi_struct *n, int work_done) NAPIF_STATE_IN_BUSY_POLL))) return false; - gro_normal_list(n); - if (n->gro_bitmask) { unsigned long timeout = 0; @@ -6217,6 +6216,9 @@ bool napi_complete_done(struct napi_struct *n, int work_done) hrtimer_start(&n->timer, ns_to_ktime(timeout), HRTIMER_MODE_REL_PINNED); } + + gro_normal_list(n); + if (unlikely(!list_empty(&n->poll_list))) { /* If n->poll_list is not empty, we need to mask irqs */ local_irq_save(flags); @@ -6548,8 +6550,6 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll) goto out_unlock; } - gro_normal_list(n); - if (n->gro_bitmask) { /* flush too old packets * If HZ < 1000, flush all packets. @@ -6557,6 +6557,8 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll) napi_gro_flush(n, HZ >= 1000); } + gro_normal_list(n); + /* Some drivers may have called napi_schedule * prior to exhausting their budget. */ -- cgit