Commit 8e4d980a authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller

tcp: fix behavior for epoll edge trigger

Under memory pressure, tcp_sendmsg() can fail to queue a packet
while no packet is present in write queue. If we return -EAGAIN
with no packet in write queue, no ACK packet will ever come
to raise EPOLLOUT.

We need to allow one skb per TCP socket, and make sure that
tcp sockets can release their forward allocations under pressure.

This is a followup to commit 790ba456 ("tcp: set SOCK_NOSPACE
under memory pressure")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b8da51eb
...@@ -815,9 +815,20 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp) ...@@ -815,9 +815,20 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp)
/* The TCP header must be at least 32-bit aligned. */ /* The TCP header must be at least 32-bit aligned. */
size = ALIGN(size, 4); size = ALIGN(size, 4);
if (unlikely(tcp_under_memory_pressure(sk)))
sk_mem_reclaim_partial(sk);
skb = alloc_skb_fclone(size + sk->sk_prot->max_header, gfp); skb = alloc_skb_fclone(size + sk->sk_prot->max_header, gfp);
if (skb) { if (likely(skb)) {
if (sk_wmem_schedule(sk, skb->truesize)) { bool mem_schedule;
if (skb_queue_len(&sk->sk_write_queue) == 0) {
mem_schedule = true;
sk_forced_mem_schedule(sk, skb->truesize);
} else {
mem_schedule = sk_wmem_schedule(sk, skb->truesize);
}
if (likely(mem_schedule)) {
skb_reserve(skb, sk->sk_prot->max_header); skb_reserve(skb, sk->sk_prot->max_header);
/* /*
* Make sure that we have exactly size bytes * Make sure that we have exactly size bytes
......
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