4.19-stable review patch. If anyone has any objections, please let me know.
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From: Paolo Abeni pabeni@redhat.com
[ Upstream commit 605108acfe6233b72e2f803aa1cb59a2af3001ca ]
Eric noted that with UDP GRO and NAPI timeout, we could keep a single UDP packet inside the GRO hash forever, if the related NAPI instance calls napi_gro_complete() at an higher frequency than the NAPI timeout. Willem noted that even TCP packets could be trapped there, till the next retransmission. This patch tries to address the issue, flushing the old packets - those with a NAPI_GRO_CB age before the current jiffy - before scheduling the NAPI timeout. The rationale is that such a timeout should be well below a jiffy and we are not flushing packets eligible for sane GRO.
v1 -> v2: - clarified the commit message and comment
RFC -> v1: - added 'Fixes tags', cleaned-up the wording.
Reported-by: Eric Dumazet eric.dumazet@gmail.com Fixes: 3b47d30396ba ("net: gro: add a per device gro flush timer") Signed-off-by: Paolo Abeni pabeni@redhat.com Acked-by: Willem de Bruijn willemb@google.com Acked-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/dev.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/net/core/dev.c +++ b/net/core/dev.c @@ -5945,11 +5945,14 @@ bool napi_complete_done(struct napi_stru if (work_done) timeout = n->dev->gro_flush_timeout;
+ /* When the NAPI instance uses a timeout and keeps postponing + * it, we need to bound somehow the time packets are kept in + * the GRO layer + */ + napi_gro_flush(n, !!timeout); if (timeout) hrtimer_start(&n->timer, ns_to_ktime(timeout), HRTIMER_MODE_REL_PINNED); - else - napi_gro_flush(n, false); } if (unlikely(!list_empty(&n->poll_list))) { /* If n->poll_list is not empty, we need to mask irqs */