IB/ipoib: move back IB LL address into the hard header
After the commit 9207f9d4 ("net: preserve IP control block during GSO segmentation"), the GSO CB and the IPoIB CB conflict. That destroy the IPoIB address information cached there, causing a severe performance regression, as better described here: http://marc.info/?l=linux-kernel&m=146787279825501&w=2 This change moves the data cached by the IPoIB driver from the skb control lock into the IPoIB hard header, as done before the commit 936d7de3 ("IPoIB: Stop lying about hard_header_len and use skb->cb to stash LL addresses"). In order to avoid GRO issue, on packet reception, the IPoIB driver stash into the skb a dummy pseudo header, so that the received packets have actually a hard header matching the declared length. To avoid changing the connected mode maximum mtu, the allocated head buffer size is increased by the pseudo header length. After this commit, IPoIB performances are back to pre-regression value. v2 -> v3: rebased v1 -> v2: avoid changing the max mtu, increasing the head buf size Fixes: 9207f9d4 ("net: preserve IP control block during GSO segmentation") Signed-off-by: NPaolo Abeni <pabeni@redhat.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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