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Date: Wed, 19 Oct 2016 14:47:01 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
James Morris <jmorris@...ei.org>,
Trond Myklebust <trond.myklebust@...marydata.com>,
Alexander Duyck <aduyck@...antis.com>,
Daniel Borkmann <daniel@...earbox.net>,
Eric Dumazet <edumazet@...gle.com>,
Tom Herbert <tom@...bertland.com>,
Hannes Frederic Sowa <hannes@...essinduktion.org>,
Edward Cree <ecree@...arflare.com>, linux-nfs@...r.kernel.org
Subject: [PATCH net-next v4 2/3] udp: implement memory accounting helpers
Avoid using the generic helpers.
Adds a new spinlock_t to the udp_sock structure and use
it to protect the memory accounting operation, both on
enqueue and on dequeue.
On dequeue perform partial memory reclaiming, trying to
leave a quantum of forward allocated memory.
On enqueue use a custom helper, to allow some optimizations:
- use a plain spin_lock() variant instead of the slightly
costly spin_lock_irqsave(),
- avoid dst_force check, since the calling code has already
dropped the skb dst
The above needs custom memory reclaiming on shutdown, provided
by the udp_destruct_sock().
v3 -> v4:
- reworked memory accunting, simplifying the schema
- provide an helper for both memory scheduling and enqueuing
v1 -> v2:
- use a udp specific destrctor to perform memory reclaiming
- remove a couple of helpers, unneeded after the above cleanup
- do not reclaim memory on dequeue if not under memory
pressure
- reworked the fwd accounting schema to avoid potential
integer overflow
Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
include/linux/udp.h | 1 +
include/net/udp.h | 4 ++
net/ipv4/udp.c | 111 ++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 116 insertions(+)
diff --git a/include/linux/udp.h b/include/linux/udp.h
index d1fd8cd..8ea7f8b 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -66,6 +66,7 @@ struct udp_sock {
#define UDPLITE_RECV_CC 0x4 /* set via udplite setsocktopt */
__u8 pcflag; /* marks socket as UDP-Lite if > 0 */
__u8 unused[3];
+ spinlock_t mem_lock; /* protects memory accounting */
/*
* For encapsulation sockets.
*/
diff --git a/include/net/udp.h b/include/net/udp.h
index ea53a87..18f1e6b 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -246,6 +246,9 @@ static inline __be16 udp_flow_src_port(struct net *net, struct sk_buff *skb,
}
/* net/ipv4/udp.c */
+void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len);
+int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb);
+
void udp_v4_early_demux(struct sk_buff *skb);
int udp_get_port(struct sock *sk, unsigned short snum,
int (*saddr_cmp)(const struct sock *,
@@ -258,6 +261,7 @@ int udp_get_port(struct sock *sk, unsigned short snum,
void udp4_hwcsum(struct sk_buff *skb, __be32 src, __be32 dst);
int udp_rcv(struct sk_buff *skb);
int udp_ioctl(struct sock *sk, int cmd, unsigned long arg);
+int udp_init_sock(struct sock *sk);
int udp_disconnect(struct sock *sk, int flags);
unsigned int udp_poll(struct file *file, struct socket *sock, poll_table *wait);
struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 7d96dc2..7047bb3 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1172,6 +1172,117 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset,
return ret;
}
+static void udp_rmem_release(struct sock *sk, int size, int partial)
+{
+ struct udp_sock *up = udp_sk(sk);
+ int amt;
+
+ atomic_sub(size, &sk->sk_rmem_alloc);
+
+ spin_lock_bh(&up->mem_lock);
+ sk->sk_forward_alloc += size;
+ amt = (sk->sk_forward_alloc - partial) & ~(SK_MEM_QUANTUM - 1);
+ sk->sk_forward_alloc -= amt;
+ spin_unlock_bh(&up->mem_lock);
+
+ if (amt)
+ __sk_mem_reduce_allocated(sk, amt >> SK_MEM_QUANTUM_SHIFT);
+}
+
+static void udp_rmem_free(struct sk_buff *skb)
+{
+ udp_rmem_release(skb->sk, skb->truesize, 1);
+}
+
+int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
+{
+ struct sk_buff_head *list = &sk->sk_receive_queue;
+ int rmem, delta, amt, err = -ENOMEM;
+ struct udp_sock *up = udp_sk(sk);
+ int size = skb->truesize;
+
+ /* try to avoid the costly atomic add/sub pair when the receive
+ * queue is full
+ */
+ if (atomic_read(&sk->sk_rmem_alloc) + size > sk->sk_rcvbuf)
+ goto drop;
+
+ rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
+ if (rmem > sk->sk_rcvbuf)
+ goto uncharge_drop;
+
+ spin_lock(&up->mem_lock);
+ if (size < sk->sk_forward_alloc)
+ goto unlock;
+
+ amt = sk_mem_pages(size);
+ delta = amt << SK_MEM_QUANTUM_SHIFT;
+ if (!__sk_mem_raise_allocated(sk, delta, amt, SK_MEM_RECV)) {
+ err = -ENOBUFS;
+ spin_unlock(&up->mem_lock);
+ goto uncharge_drop;
+ }
+
+ sk->sk_forward_alloc += delta;
+
+unlock:
+ sk->sk_forward_alloc -= size;
+ spin_unlock(&up->mem_lock);
+
+ /* the skb owner in now the udp socket */
+ skb_orphan(skb);
+ skb->sk = sk;
+ skb->destructor = udp_rmem_free;
+
+ skb->dev = NULL;
+ sock_skb_set_dropcount(sk, skb);
+
+ spin_lock(&list->lock);
+ __skb_queue_tail(list, skb);
+ spin_unlock(&list->lock);
+
+ if (!sock_flag(sk, SOCK_DEAD))
+ sk->sk_data_ready(sk);
+
+ return 0;
+
+uncharge_drop:
+ atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
+
+drop:
+ atomic_inc(&sk->sk_drops);
+ return err;
+}
+EXPORT_SYMBOL_GPL(__udp_enqueue_schedule_skb);
+
+static void udp_destruct_sock(struct sock *sk)
+{
+ /* reclaim completely the forward allocated memory */
+ __skb_queue_purge(&sk->sk_receive_queue);
+ udp_rmem_release(sk, 0, 0);
+ inet_sock_destruct(sk);
+}
+
+int udp_init_sock(struct sock *sk)
+{
+ sk->sk_destruct = udp_destruct_sock;
+ spin_lock_init(&udp_sk(sk)->mem_lock);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(udp_init_sock);
+
+void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len)
+{
+ if (unlikely(READ_ONCE(sk->sk_peek_off) >= 0)) {
+ bool slow = lock_sock_fast(sk);
+
+ sk_peek_offset_bwd(sk, len);
+ unlock_sock_fast(sk, slow);
+ }
+ consume_skb(skb);
+}
+EXPORT_SYMBOL_GPL(skb_consume_udp);
+
/**
* first_packet_length - return length of first packet in receive queue
* @sk: socket
--
1.8.3.1
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