Commit e42134b5 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'tcp-mem-pressure-fixes' 



Eric Dumazet says:

====================
tcp: final (?) round of mem pressure fixes

While working on prior patch series (e10b02ee "Merge branch
'net-reduce-tcp_memory_allocated-inflation'"), I found that we
could still have frozen TCP flows under memory pressure.

I thought we had solved this in 2015, but the fix was not complete.

v2: deal with zerocopy tx paths.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents e8b03391 f54755f6

net/ipv4/tcp.c

+46 −4
Original line number Diff line number Diff line
@@ -951,6 +951,40 @@ static int tcp_downgrade_zcopy_pure(struct sock *sk, struct sk_buff *skb) 
	return 0;

}



static int tcp_wmem_schedule(struct sock *sk, int copy)

{

	int left;



	if (likely(sk_wmem_schedule(sk, copy)))

		return copy;



	/* We could be in trouble if we have nothing queued.

	 * Use whatever is left in sk->sk_forward_alloc and tcp_wmem[0]

	 * to guarantee some progress.

	 */

	left = sock_net(sk)->ipv4.sysctl_tcp_wmem[0] - sk->sk_wmem_queued;

	if (left > 0)

		sk_forced_mem_schedule(sk, min(left, copy));

	return min(copy, sk->sk_forward_alloc);

}



static int tcp_wmem_schedule(struct sock *sk, int copy)

{

	int left;



	if (likely(sk_wmem_schedule(sk, copy)))

		return copy;



	/* We could be in trouble if we have nothing queued.

	 * Use whatever is left in sk->sk_forward_alloc and tcp_wmem[0]

	 * to guarantee some progress.

	 */

	left = sock_net(sk)->ipv4.sysctl_tcp_wmem[0] - sk->sk_wmem_queued;

	if (left > 0)

		sk_forced_mem_schedule(sk, min(left, copy));

	return min(copy, sk->sk_forward_alloc);

}



static struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags,

				      struct page *page, int offset, size_t *size)

{
@@ -986,7 +1020,11 @@ static struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags, 
		tcp_mark_push(tp, skb);

		goto new_segment;

	}

	if (tcp_downgrade_zcopy_pure(sk, skb) || !sk_wmem_schedule(sk, copy))

	if (tcp_downgrade_zcopy_pure(sk, skb))

		return NULL;



	copy = tcp_wmem_schedule(sk, copy);

	if (!copy)

		return NULL;



	if (can_coalesce) {
@@ -1334,8 +1372,11 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 


			copy = min_t(int, copy, pfrag->size - pfrag->offset);



			if (tcp_downgrade_zcopy_pure(sk, skb) ||

			    !sk_wmem_schedule(sk, copy))

			if (tcp_downgrade_zcopy_pure(sk, skb))

				goto wait_for_space;



			copy = tcp_wmem_schedule(sk, copy);

			if (!copy)

				goto wait_for_space;



			err = skb_copy_to_page_nocache(sk, &msg->msg_iter, skb,
@@ -1362,7 +1403,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) 
				skb_shinfo(skb)->flags |= SKBFL_PURE_ZEROCOPY;



			if (!skb_zcopy_pure(skb)) {

				if (!sk_wmem_schedule(sk, copy))

				copy = tcp_wmem_schedule(sk, copy);

				if (!copy)

					goto wait_for_space;

			}

net/ipv4/tcp_output.c

+4 −3
Original line number Diff line number Diff line
@@ -3362,11 +3362,12 @@ void tcp_xmit_retransmit_queue(struct sock *sk) 
 */

void sk_forced_mem_schedule(struct sock *sk, int size)

{

	int amt;

	int delta, amt;



	if (size <= sk->sk_forward_alloc)

	delta = size - sk->sk_forward_alloc;

	if (delta <= 0)

		return;

	amt = sk_mem_pages(size);

	amt = sk_mem_pages(delta);

	sk->sk_forward_alloc += amt << PAGE_SHIFT;

	sk_memory_allocated_add(sk, amt);