[PATCH net-next v5 0/3] udp: refactor memory accounting

[PATCH net-next v5 0/3] udp: refactor memory accounting

[Paolo Abeni]

This patch series refactor the udp memory accounting, replacing the
generic implementation with a custom one, in order to remove the needs for
locking the socket on the enqueue and dequeue operations. The socket backlog
usage is dropped, as well.

The first patch factor out pieces of some queue and memory management
socket helpers, so that they can later be used by the udp memory accounting
functions.
The second patch adds the memory account helpers, without using them.
The third patch replacse the old rx memory accounting path for udp over ipv4 and
udp over ipv6. In kernel UDP users are updated, as well.

The memory accounting schema is described in detail in the individual patch
commit message.

The performance gain depends on the specific scenario; with few flows (and
little contention in the original code) the differences are in the noise range,
while with several flows contending the same socket, the measured speed-up
is relevant (e.g. even over 100% in case of extreme contention)

v4 -> v5:
 - use the receive queue spin lock to protect the memory accounting
 - several minor clean-up

v3 -> v4:
 - simplified the locking schema, always use a plain spinlock

v2 -> v3:
 - do not set the now unsed backlog_rcv callback

v1 -> v2:
 - changed slighly the memory accounting schema, we now perform lazy reclaim
 - fixed forward_alloc updating issue
 - fixed memory counter integer overflows

Paolo Abeni (3):
  net/socket: factor out helpers for memory and queue manipulation
  udp: implement memory accounting helpers
  udp: use it's own memory accounting schema

 include/net/sock.h    |   4 ++
 include/net/udp.h     |   4 ++
 net/core/datagram.c   |  36 +++++++-----
 net/core/sock.c       |  64 ++++++++++++++-------
 net/ipv4/udp.c        | 151 ++++++++++++++++++++++++++++++++++++++------------
 net/ipv6/udp.c        |  34 +++---------
 net/sunrpc/svcsock.c  |  20 +++++--
 net/sunrpc/xprtsock.c |   2 +-
 8 files changed, 216 insertions(+), 99 deletions(-)

-- 
1.8.3.1

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[PATCH net-next v5 1/3] net/socket: factor out helpers for memory and queue manipulation

[Paolo Abeni]

Basic sock operations that udp code can use with its own
memory accounting schema. No functional change is introduced
in the existing APIs.

v4 -> v5:
  - avoid whitespace changes

v2 -> v4:
  - avoid exporting __sock_enqueue_skb

v1 -> v2:
  - avoid export sock_rmem_free

Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 include/net/sock.h  |  4 ++++
 net/core/datagram.c | 36 ++++++++++++++++++------------
 net/core/sock.c     | 64 +++++++++++++++++++++++++++++++++++++----------------
 3 files changed, 71 insertions(+), 33 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index ebf75db..2764895 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1274,7 +1274,9 @@ static inline struct inode *SOCK_INODE(struct socket *socket)
 /*
  * Functions for memory accounting
  */
+int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind);
 int __sk_mem_schedule(struct sock *sk, int size, int kind);
+void __sk_mem_reduce_allocated(struct sock *sk, int amount);
 void __sk_mem_reclaim(struct sock *sk, int amount);
 
 #define SK_MEM_QUANTUM ((int)PAGE_SIZE)
@@ -1950,6 +1952,8 @@ void sk_reset_timer(struct sock *sk, struct timer_list *timer,
 
 void sk_stop_timer(struct sock *sk, struct timer_list *timer);
 
+int __sk_queue_drop_skb(struct sock *sk, struct sk_buff *skb,
+			unsigned int flags);
 int __sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
 int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
 
diff --git a/net/core/datagram.c b/net/core/datagram.c
index b7de71f..bfb973a 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -323,6 +323,27 @@ void __skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb, int len)
 }
 EXPORT_SYMBOL(__skb_free_datagram_locked);
 
+int __sk_queue_drop_skb(struct sock *sk, struct sk_buff *skb,
+			unsigned int flags)
+{
+	int err = 0;
+
+	if (flags & MSG_PEEK) {
+		err = -ENOENT;
+		spin_lock_bh(&sk->sk_receive_queue.lock);
+		if (skb == skb_peek(&sk->sk_receive_queue)) {
+			__skb_unlink(skb, &sk->sk_receive_queue);
+			atomic_dec(&skb->users);
+			err = 0;
+		}
+		spin_unlock_bh(&sk->sk_receive_queue.lock);
+	}
+
+	atomic_inc(&sk->sk_drops);
+	return err;
+}
+EXPORT_SYMBOL(__sk_queue_drop_skb);
+
 /**
  *	skb_kill_datagram - Free a datagram skbuff forcibly
  *	@sk: socket
@@ -346,23 +367,10 @@ void __skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb, int len)
 
 int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
 {
-	int err = 0;
-
-	if (flags & MSG_PEEK) {
-		err = -ENOENT;
-		spin_lock_bh(&sk->sk_receive_queue.lock);
-		if (skb == skb_peek(&sk->sk_receive_queue)) {
-			__skb_unlink(skb, &sk->sk_receive_queue);
-			atomic_dec(&skb->users);
-			err = 0;
-		}
-		spin_unlock_bh(&sk->sk_receive_queue.lock);
-	}
+	int err = __sk_queue_drop_skb(sk, skb, flags);
 
 	kfree_skb(skb);
-	atomic_inc(&sk->sk_drops);
 	sk_mem_reclaim_partial(sk);
-
 	return err;
 }
 EXPORT_SYMBOL(skb_kill_datagram);
diff --git a/net/core/sock.c b/net/core/sock.c
index c73e28f..d8e4532e 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2091,24 +2091,18 @@ int sk_wait_data(struct sock *sk, long *timeo, const struct sk_buff *skb)
 EXPORT_SYMBOL(sk_wait_data);
 
 /**
- *	__sk_mem_schedule - increase sk_forward_alloc and memory_allocated
+ *	__sk_mem_raise_allocated - increase memory_allocated
  *	@sk: socket
  *	@size: memory size to allocate
+ *	@amt: pages to allocate
  *	@kind: allocation type
  *
- *	If kind is SK_MEM_SEND, it means wmem allocation. Otherwise it means
- *	rmem allocation. This function assumes that protocols which have
- *	memory_pressure use sk_wmem_queued as write buffer accounting.
+ *	Similar to __sk_mem_schedule(), but does not update sk_forward_alloc
  */
-int __sk_mem_schedule(struct sock *sk, int size, int kind)
+int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)
 {
 	struct proto *prot = sk->sk_prot;
-	int amt = sk_mem_pages(size);
-	long allocated;
-
-	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
-
-	allocated = sk_memory_allocated_add(sk, amt);
+	long allocated = sk_memory_allocated_add(sk, amt);
 
 	if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
 	    !mem_cgroup_charge_skmem(sk->sk_memcg, amt))
@@ -2169,9 +2163,6 @@ int __sk_mem_schedule(struct sock *sk, int size, int kind)
 
 	trace_sock_exceed_buf_limit(sk, prot, allocated);
 
-	/* Alas. Undo changes. */
-	sk->sk_forward_alloc -= amt * SK_MEM_QUANTUM;
-
 	sk_memory_allocated_sub(sk, amt);
 
 	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
@@ -2179,18 +2170,40 @@ int __sk_mem_schedule(struct sock *sk, int size, int kind)
 
 	return 0;
 }
+EXPORT_SYMBOL(__sk_mem_raise_allocated);
+
+/**
+ *	__sk_mem_schedule - increase sk_forward_alloc and memory_allocated
+ *	@sk: socket
+ *	@size: memory size to allocate
+ *	@kind: allocation type
+ *
+ *	If kind is SK_MEM_SEND, it means wmem allocation. Otherwise it means
+ *	rmem allocation. This function assumes that protocols which have
+ *	memory_pressure use sk_wmem_queued as write buffer accounting.
+ */
+int __sk_mem_schedule(struct sock *sk, int size, int kind)
+{
+	int ret, amt = sk_mem_pages(size);
+
+	sk->sk_forward_alloc += amt << SK_MEM_QUANTUM_SHIFT;
+	ret = __sk_mem_raise_allocated(sk, size, amt, kind);
+	if (!ret)
+		sk->sk_forward_alloc -= amt << SK_MEM_QUANTUM_SHIFT;
+	return ret;
+}
 EXPORT_SYMBOL(__sk_mem_schedule);
 
 /**
- *	__sk_mem_reclaim - reclaim memory_allocated
+ *	__sk_mem_reduce_allocated - reclaim memory_allocated
  *	@sk: socket
- *	@amount: number of bytes (rounded down to a SK_MEM_QUANTUM multiple)
+ *	@amount: number of quanta
+ *
+ *	Similar to __sk_mem_reclaim(), but does not update sk_forward_alloc
  */
-void __sk_mem_reclaim(struct sock *sk, int amount)
+void __sk_mem_reduce_allocated(struct sock *sk, int amount)
 {
-	amount >>= SK_MEM_QUANTUM_SHIFT;
 	sk_memory_allocated_sub(sk, amount);
-	sk->sk_forward_alloc -= amount << SK_MEM_QUANTUM_SHIFT;
 
 	if (mem_cgroup_sockets_enabled && sk->sk_memcg)
 		mem_cgroup_uncharge_skmem(sk->sk_memcg, amount);
@@ -2199,6 +2212,19 @@ void __sk_mem_reclaim(struct sock *sk, int amount)
 	    (sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)))
 		sk_leave_memory_pressure(sk);
 }
+EXPORT_SYMBOL(__sk_mem_reduce_allocated);
+
+/**
+ *	__sk_mem_reclaim - reclaim sk_forward_alloc and memory_allocated
+ *	@sk: socket
+ *	@amount: number of bytes (rounded down to a SK_MEM_QUANTUM multiple)
+ */
+void __sk_mem_reclaim(struct sock *sk, int amount)
+{
+	amount >>= SK_MEM_QUANTUM_SHIFT;
+	sk->sk_forward_alloc -= amount << SK_MEM_QUANTUM_SHIFT;
+	__sk_mem_reduce_allocated(sk, amount);
+}
 EXPORT_SYMBOL(__sk_mem_reclaim);
 
 int sk_set_peek_off(struct sock *sk, int val)
-- 
1.8.3.1

[PATCH net-next v5 2/3] udp: implement memory accounting helpers

[Paolo Abeni]

Avoid using the generic helpers.
Use the receive queue spin lock 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().

v4 -> v5:
  - replace the mem_lock with the receive queue spin lock
  - ensure that the bh is always allowed to enqueue at least
    a skb, even if sk_rcvbuf is exceeded

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-tFNcAqjVMyqKXQKiL6tip0B+6BGkLq7r@public.gmane.org>
Signed-off-by: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 include/net/udp.h |   4 ++
 net/ipv4/udp.c    | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 112 insertions(+)

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..5e79992 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1172,6 +1172,114 @@ 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)
+{
+	int amt;
+
+	atomic_sub(size, &sk->sk_rmem_alloc);
+
+	spin_lock_bh(&sk->sk_receive_queue.lock);
+	sk->sk_forward_alloc += size;
+	amt = (sk->sk_forward_alloc - partial) & ~(SK_MEM_QUANTUM - 1);
+	sk->sk_forward_alloc -= amt;
+	spin_unlock_bh(&sk->sk_receive_queue.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;
+	int size = skb->truesize;
+
+	/* try to avoid the costly atomic add/sub pair when the receive
+	 * queue is full; always allow at least a packet
+	 */
+	rmem = atomic_read(&sk->sk_rmem_alloc);
+	if (rmem && (rmem + size > sk->sk_rcvbuf))
+		goto drop;
+
+	/* we drop only if the receive buf is full and the receive
+	 * queue contains some other skb
+	 */
+	rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
+	if ((rmem > sk->sk_rcvbuf) && (rmem > size))
+		goto uncharge_drop;
+
+	skb_orphan(skb);
+
+	spin_lock(&list->lock);
+	if (size >= sk->sk_forward_alloc) {
+		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(&list->lock);
+			goto uncharge_drop;
+		}
+
+		sk->sk_forward_alloc += delta;
+	}
+
+	sk->sk_forward_alloc -= size;
+
+	/* the skb owner in now the udp socket */
+	skb->sk = sk;
+	skb->destructor = udp_rmem_free;
+	skb->dev = NULL;
+	sock_skb_set_dropcount(sk, skb);
+
+	__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;
+	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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[PATCH net-next v5 3/3] udp: use it's own memory accounting schema

[Paolo Abeni]

Completely avoid default sock memory accounting and replace it
with udp-specific accounting.

Since the new memory accounting model encapsulates completely
the required locking, remove the socket lock on both enqueue and
dequeue, and avoid using the backlog on enqueue.

Be sure to clean-up rx queue memory on socket destruction, using
udp its own sk_destruct.

Tested using pktgen with random src port, 64 bytes packet,
wire-speed on a 10G link as sender and udp_sink as the receiver,
using an l4 tuple rxhash to stress the contention, and one or more
udp_sink instances with reuseport.

nr readers      Kpps (vanilla)  Kpps (patched)
1               170             440
3               1250            2150
6               3000            3650
9               4200            4450
12              5700            6250

v4 -> v5:
  - avoid unneeded test in first_packet_length

v3 -> v4:
  - remove useless sk_rcvqueues_full() call

v2 -> v3:
  - do not set the now unsed backlog_rcv callback

v1 -> v2:
  - add memory pressure support
  - fixed dropwatch accounting for ipv6

Acked-by: Hannes Frederic Sowa <hannes-tFNcAqjVMyqKXQKiL6tip0B+6BGkLq7r@public.gmane.org>
Signed-off-by: Paolo Abeni <pabeni-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 net/ipv4/udp.c        | 43 ++++++++-----------------------------------
 net/ipv6/udp.c        | 34 ++++++++--------------------------
 net/sunrpc/svcsock.c  | 20 ++++++++++++++++----
 net/sunrpc/xprtsock.c |  2 +-
 4 files changed, 33 insertions(+), 66 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 5e79992..73d33a8 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1309,13 +1309,7 @@ static int first_packet_length(struct sock *sk)
 	res = skb ? skb->len : -1;
 	spin_unlock_bh(&rcvq->lock);
 
-	if (!skb_queue_empty(&list_kill)) {
-		bool slow = lock_sock_fast(sk);
-
-		__skb_queue_purge(&list_kill);
-		sk_mem_reclaim_partial(sk);
-		unlock_sock_fast(sk, slow);
-	}
+	__skb_queue_purge(&list_kill);
 	return res;
 }
 
@@ -1364,7 +1358,6 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 	int err;
 	int is_udplite = IS_UDPLITE(sk);
 	bool checksum_valid = false;
-	bool slow;
 
 	if (flags & MSG_ERRQUEUE)
 		return ip_recv_error(sk, msg, len, addr_len);
@@ -1405,13 +1398,12 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 	}
 
 	if (unlikely(err)) {
-		trace_kfree_skb(skb, udp_recvmsg);
 		if (!peeked) {
 			atomic_inc(&sk->sk_drops);
 			UDP_INC_STATS(sock_net(sk),
 				      UDP_MIB_INERRORS, is_udplite);
 		}
-		skb_free_datagram_locked(sk, skb);
+		kfree_skb(skb);
 		return err;
 	}
 
@@ -1436,16 +1428,15 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
 	if (flags & MSG_TRUNC)
 		err = ulen;
 
-	__skb_free_datagram_locked(sk, skb, peeking ? -err : err);
+	skb_consume_udp(sk, skb, peeking ? -err : err);
 	return err;
 
 csum_copy_err:
-	slow = lock_sock_fast(sk);
-	if (!skb_kill_datagram(sk, skb, flags)) {
+	if (!__sk_queue_drop_skb(sk, skb, flags)) {
 		UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
 		UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
 	}
-	unlock_sock_fast(sk, slow);
+	kfree_skb(skb);
 
 	/* starting over for a new packet, but check if we need to yield */
 	cond_resched();
@@ -1564,7 +1555,7 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		sk_incoming_cpu_update(sk);
 	}
 
-	rc = __sock_queue_rcv_skb(sk, skb);
+	rc = __udp_enqueue_schedule_skb(sk, skb);
 	if (rc < 0) {
 		int is_udplite = IS_UDPLITE(sk);
 
@@ -1579,7 +1570,6 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	}
 
 	return 0;
-
 }
 
 static struct static_key udp_encap_needed __read_mostly;
@@ -1601,7 +1591,6 @@ void udp_encap_enable(void)
 int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
 	struct udp_sock *up = udp_sk(sk);
-	int rc;
 	int is_udplite = IS_UDPLITE(sk);
 
 	/*
@@ -1688,25 +1677,9 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		goto drop;
 
 	udp_csum_pull_header(skb);
-	if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {
-		__UDP_INC_STATS(sock_net(sk), UDP_MIB_RCVBUFERRORS,
-				is_udplite);
-		goto drop;
-	}
-
-	rc = 0;
 
 	ipv4_pktinfo_prepare(sk, skb);
-	bh_lock_sock(sk);
-	if (!sock_owned_by_user(sk))
-		rc = __udp_queue_rcv_skb(sk, skb);
-	else if (sk_add_backlog(sk, skb, sk->sk_rcvbuf)) {
-		bh_unlock_sock(sk);
-		goto drop;
-	}
-	bh_unlock_sock(sk);
-
-	return rc;
+	return __udp_queue_rcv_skb(sk, skb);
 
 csum_error:
 	__UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
@@ -2316,13 +2289,13 @@ struct proto udp_prot = {
 	.connect	   = ip4_datagram_connect,
 	.disconnect	   = udp_disconnect,
 	.ioctl		   = udp_ioctl,
+	.init		   = udp_init_sock,
 	.destroy	   = udp_destroy_sock,
 	.setsockopt	   = udp_setsockopt,
 	.getsockopt	   = udp_getsockopt,
 	.sendmsg	   = udp_sendmsg,
 	.recvmsg	   = udp_recvmsg,
 	.sendpage	   = udp_sendpage,
-	.backlog_rcv	   = __udp_queue_rcv_skb,
 	.release_cb	   = ip4_datagram_release_cb,
 	.hash		   = udp_lib_hash,
 	.unhash		   = udp_lib_unhash,
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 9aa7c1c..71963b2 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -334,7 +334,6 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 	int is_udplite = IS_UDPLITE(sk);
 	bool checksum_valid = false;
 	int is_udp4;
-	bool slow;
 
 	if (flags & MSG_ERRQUEUE)
 		return ipv6_recv_error(sk, msg, len, addr_len);
@@ -378,7 +377,6 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 			goto csum_copy_err;
 	}
 	if (unlikely(err)) {
-		trace_kfree_skb(skb, udpv6_recvmsg);
 		if (!peeked) {
 			atomic_inc(&sk->sk_drops);
 			if (is_udp4)
@@ -388,7 +386,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 				UDP6_INC_STATS(sock_net(sk), UDP_MIB_INERRORS,
 					       is_udplite);
 		}
-		skb_free_datagram_locked(sk, skb);
+		kfree_skb(skb);
 		return err;
 	}
 	if (!peeked) {
@@ -437,12 +435,11 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 	if (flags & MSG_TRUNC)
 		err = ulen;
 
-	__skb_free_datagram_locked(sk, skb, peeking ? -err : err);
+	skb_consume_udp(sk, skb, peeking ? -err : err);
 	return err;
 
 csum_copy_err:
-	slow = lock_sock_fast(sk);
-	if (!skb_kill_datagram(sk, skb, flags)) {
+	if (!__sk_queue_drop_skb(sk, skb, flags)) {
 		if (is_udp4) {
 			UDP_INC_STATS(sock_net(sk),
 				      UDP_MIB_CSUMERRORS, is_udplite);
@@ -455,7 +452,7 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 				       UDP_MIB_INERRORS, is_udplite);
 		}
 	}
-	unlock_sock_fast(sk, slow);
+	kfree_skb(skb);
 
 	/* starting over for a new packet, but check if we need to yield */
 	cond_resched();
@@ -523,7 +520,7 @@ static int __udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		sk_incoming_cpu_update(sk);
 	}
 
-	rc = __sock_queue_rcv_skb(sk, skb);
+	rc = __udp_enqueue_schedule_skb(sk, skb);
 	if (rc < 0) {
 		int is_udplite = IS_UDPLITE(sk);
 
@@ -535,6 +532,7 @@ static int __udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		kfree_skb(skb);
 		return -1;
 	}
+
 	return 0;
 }
 
@@ -556,7 +554,6 @@ void udpv6_encap_enable(void)
 int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
 	struct udp_sock *up = udp_sk(sk);
-	int rc;
 	int is_udplite = IS_UDPLITE(sk);
 
 	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
@@ -622,25 +619,10 @@ int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		goto drop;
 
 	udp_csum_pull_header(skb);
-	if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) {
-		__UDP6_INC_STATS(sock_net(sk),
-				 UDP_MIB_RCVBUFERRORS, is_udplite);
-		goto drop;
-	}
 
 	skb_dst_drop(skb);
 
-	bh_lock_sock(sk);
-	rc = 0;
-	if (!sock_owned_by_user(sk))
-		rc = __udpv6_queue_rcv_skb(sk, skb);
-	else if (sk_add_backlog(sk, skb, sk->sk_rcvbuf)) {
-		bh_unlock_sock(sk);
-		goto drop;
-	}
-	bh_unlock_sock(sk);
-
-	return rc;
+	return __udpv6_queue_rcv_skb(sk, skb);
 
 csum_error:
 	__UDP6_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
@@ -1433,12 +1415,12 @@ struct proto udpv6_prot = {
 	.connect	   = ip6_datagram_connect,
 	.disconnect	   = udp_disconnect,
 	.ioctl		   = udp_ioctl,
+	.init		   = udp_init_sock,
 	.destroy	   = udpv6_destroy_sock,
 	.setsockopt	   = udpv6_setsockopt,
 	.getsockopt	   = udpv6_getsockopt,
 	.sendmsg	   = udpv6_sendmsg,
 	.recvmsg	   = udpv6_recvmsg,
-	.backlog_rcv	   = __udpv6_queue_rcv_skb,
 	.release_cb	   = ip6_datagram_release_cb,
 	.hash		   = udp_lib_hash,
 	.unhash		   = udp_lib_unhash,
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 57625f6..e2a55dc 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -39,6 +39,7 @@
 #include <net/checksum.h>
 #include <net/ip.h>
 #include <net/ipv6.h>
+#include <net/udp.h>
 #include <net/tcp.h>
 #include <net/tcp_states.h>
 #include <asm/uaccess.h>
@@ -129,6 +130,18 @@ static void svc_release_skb(struct svc_rqst *rqstp)
 	}
 }
 
+static void svc_release_udp_skb(struct svc_rqst *rqstp)
+{
+	struct sk_buff *skb = rqstp->rq_xprt_ctxt;
+
+	if (skb) {
+		rqstp->rq_xprt_ctxt = NULL;
+
+		dprintk("svc: service %p, releasing skb %p\n", rqstp, skb);
+		consume_skb(skb);
+	}
+}
+
 union svc_pktinfo_u {
 	struct in_pktinfo pkti;
 	struct in6_pktinfo pkti6;
@@ -575,7 +588,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 			goto out_free;
 		}
 		local_bh_enable();
-		skb_free_datagram_locked(svsk->sk_sk, skb);
+		consume_skb(skb);
 	} else {
 		/* we can use it in-place */
 		rqstp->rq_arg.head[0].iov_base = skb->data;
@@ -602,8 +615,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 
 	return len;
 out_free:
-	trace_kfree_skb(skb, svc_udp_recvfrom);
-	skb_free_datagram_locked(svsk->sk_sk, skb);
+	kfree_skb(skb);
 	return 0;
 }
 
@@ -660,7 +672,7 @@ static struct svc_xprt *svc_udp_create(struct svc_serv *serv,
 	.xpo_create = svc_udp_create,
 	.xpo_recvfrom = svc_udp_recvfrom,
 	.xpo_sendto = svc_udp_sendto,
-	.xpo_release_rqst = svc_release_skb,
+	.xpo_release_rqst = svc_release_udp_skb,
 	.xpo_detach = svc_sock_detach,
 	.xpo_free = svc_sock_free,
 	.xpo_prep_reply_hdr = svc_udp_prep_reply_hdr,
diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index bf16883..8e04a43 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1074,7 +1074,7 @@ static void xs_udp_data_receive(struct sock_xprt *transport)
 		skb = skb_recv_datagram(sk, 0, 1, &err);
 		if (skb != NULL) {
 			xs_udp_data_read_skb(&transport->xprt, sk, skb);
-			skb_free_datagram_locked(sk, skb);
+			consume_skb(skb);
 			continue;
 		}
 		if (!test_and_clear_bit(XPRT_SOCK_DATA_READY, &transport->sock_state))
-- 
1.8.3.1

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Re: [PATCH net-next v5 2/3] udp: implement memory accounting helpers

[Eric Dumazet]

On Thu, 2016-10-20 at 22:31 +0200, Paolo Abeni wrote:

> +
> +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;
> +	int size = skb->truesize;
> +
> +	/* try to avoid the costly atomic add/sub pair when the receive
> +	 * queue is full; always allow at least a packet
> +	 */
> +	rmem = atomic_read(&sk->sk_rmem_alloc);
> +	if (rmem && (rmem + size > sk->sk_rcvbuf))
> +		goto drop;
> +
> +	/* we drop only if the receive buf is full and the receive
> +	 * queue contains some other skb
> +	 */
> +	rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
> +	if ((rmem > sk->sk_rcvbuf) && (rmem > size))
> +		goto uncharge_drop;
> +
> +	skb_orphan(skb);

Minor point :

UDP should already have orphaned skbs ? (it uses skb_steal_sock())



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Re: [PATCH net-next v5 2/3] udp: implement memory accounting helpers

[Paolo Abeni]

On Thu, 2016-10-20 at 14:10 -0700, Eric Dumazet wrote:
> On Thu, 2016-10-20 at 22:31 +0200, Paolo Abeni wrote:
> 
> > +
> > +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;
> > +	int size = skb->truesize;
> > +
> > +	/* try to avoid the costly atomic add/sub pair when the receive
> > +	 * queue is full; always allow at least a packet
> > +	 */
> > +	rmem = atomic_read(&sk->sk_rmem_alloc);
> > +	if (rmem && (rmem + size > sk->sk_rcvbuf))
> > +		goto drop;
> > +
> > +	/* we drop only if the receive buf is full and the receive
> > +	 * queue contains some other skb
> > +	 */
> > +	rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
> > +	if ((rmem > sk->sk_rcvbuf) && (rmem > size))
> > +		goto uncharge_drop;
> > +
> > +	skb_orphan(skb);
> 
> Minor point :
> 
> UDP should already have orphaned skbs ? (it uses skb_steal_sock())

You are right, the skb_orphan() call is redundant. 

I'll send the v6 soon.

Thank you,

Paolo


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