tcp: do_tcp_sendpages() must try to push data out on oom conditions
Since recent changes on TCP splicing (starting with commits2f533844
"tcp: allow splice() to build full TSO packets" and35f9c09f
"tcp: tcp_sendpages() should call tcp_push() once"), I started seeing massive stalls when forwarding traffic between two sockets using splice() when pipe buffers were larger than socket buffers. Latest changes (net: netdev_alloc_skb() use build_skb()) made the problem even more apparent. The reason seems to be that if do_tcp_sendpages() fails on out of memory condition without being able to send at least one byte, tcp_push() is not called and the buffers cannot be flushed. After applying the attached patch, I cannot reproduce the stalls at all and the data rate it perfectly stable and steady under any condition which previously caused the problem to be permanent. The issue seems to have been there since before the kernel migrated to git, which makes me think that the stalls I occasionally experienced with tux during stress-tests years ago were probably related to the same issue. This issue was first encountered on 3.0.31 and 3.2.17, so please backport to -stable. Signed-off-by: Willy Tarreau <w@1wt.eu> Acked-by: Eric Dumazet <edumazet@google.com> Cc: <stable@vger.kernel.org>
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@ -851,8 +851,7 @@ new_segment:
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wait_for_sndbuf:
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wait_for_sndbuf:
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set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
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set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
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wait_for_memory:
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wait_for_memory:
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if (copied)
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tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);
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tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);
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if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
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if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
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goto do_error;
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goto do_error;
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