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net: Fix packet reordering caused by GRO and listified RX cooperation 

Commit 323ebb61e3 ("net: use listified RX for handling GRO_NORMAL
skbs") introduces batching of GRO_NORMAL packets in napi_frags_finish,
and commit 6570bc79c0 ("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: 323ebb61e3 ("net: use listified RX for handling GRO_NORMAL skbs")
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Cc: Alexander Lobakin <alobakin@dlink.ru>
Cc: Edward Cree <ecree@solarflare.com>
Acked-by: Alexander Lobakin <alobakin@dlink.ru>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Maxim Mikityanskiy 2020-01-21 15:09:40 +00:00 committed by David S. Miller
parent 0ace17d568
commit c80794323e
2 changed files with 35 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/net/wireless/intel/iwlwifi/pcie/rx.c
View File

@ -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);

64
net/core/dev.c
View File

@ -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.
*/