From: Eric Dumazet edumazet@google.com
[ Upstream commit ef8d8ccdc216f797e66cb4a1372f5c4c285ce1e4 ]
As Jason Baron explained in commit 790ba4566c1a ("tcp: set SOCK_NOSPACE under memory pressure"), it is crucial we properly set SOCK_NOSPACE when needed.
However, Jason patch had a bug, because the 'nonblocking' status as far as sk_stream_wait_memory() is concerned is governed by MSG_DONTWAIT flag passed at sendmsg() time :
long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
So it is very possible that tcp sendmsg() calls sk_stream_wait_memory(), and that sk_stream_wait_memory() returns -EAGAIN with SOCK_NOSPACE cleared, if sk->sk_sndtimeo has been set to a small (but not zero) value.
This patch removes the 'noblock' variable since we must always set SOCK_NOSPACE if -EAGAIN is returned.
It also renames the do_nonblock label since we might reach this code path even if we were in blocking mode.
Fixes: 790ba4566c1a ("tcp: set SOCK_NOSPACE under memory pressure") Signed-off-by: Eric Dumazet edumazet@google.com Cc: Jason Baron jbaron@akamai.com Reported-by: Vladimir Rutsky rutsky@google.com Acked-by: Soheil Hassas Yeganeh soheil@google.com Acked-by: Neal Cardwell ncardwell@google.com Acked-by: Jason Baron jbaron@akamai.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/stream.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)
--- a/net/core/stream.c +++ b/net/core/stream.c @@ -118,7 +118,6 @@ int sk_stream_wait_memory(struct sock *s int err = 0; long vm_wait = 0; long current_timeo = *timeo_p; - bool noblock = (*timeo_p ? false : true); DEFINE_WAIT(wait);
if (sk_stream_memory_free(sk)) @@ -131,11 +130,8 @@ int sk_stream_wait_memory(struct sock *s
if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)) goto do_error; - if (!*timeo_p) { - if (noblock) - set_bit(SOCK_NOSPACE, &sk->sk_socket->flags); - goto do_nonblock; - } + if (!*timeo_p) + goto do_eagain; if (signal_pending(current)) goto do_interrupted; sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk); @@ -167,7 +163,13 @@ out: do_error: err = -EPIPE; goto out; -do_nonblock: +do_eagain: + /* Make sure that whenever EAGAIN is returned, EPOLLOUT event can + * be generated later. + * When TCP receives ACK packets that make room, tcp_check_space() + * only calls tcp_new_space() if SOCK_NOSPACE is set. + */ + set_bit(SOCK_NOSPACE, &sk->sk_socket->flags); err = -EAGAIN; goto out; do_interrupted: