From: Eric Dumazet <edumazet@google.com>

If tcp_send_ack() can not allocate skb, we properly handle this
and setup a timer to try later.

Use __GFP_NOWARN to avoid polluting syslog in the case host is
under memory pressure, so that pertinent messages are not lost under
a flood of useless information.

sk_gfp_atomic() can use its gfp_mask argument (all callers currently
were using GFP_ATOMIC before this patch)

Note that when tcp_transmit_skb() is called with clone_it set to false,
we do not attempt memory allocations, so can pass a 0 gfp_mask, which
most compilers can emit faster than a non zero value.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/sock.h    |    2 +-
 net/ipv4/tcp_output.c |   12 +++++++-----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 7f89e4ba18d1..ead514332ae8 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h

@@ -776,7 +776,7 @@ static inline int sk_memalloc_socks(void)
 
 static inline gfp_t sk_gfp_atomic(const struct sock *sk, gfp_t gfp_mask)
 {
-	return GFP_ATOMIC | (sk->sk_allocation & __GFP_MEMALLOC);
+	return gfp_mask | (sk->sk_allocation & __GFP_MEMALLOC);
 }