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    Subject[PATCH 5.4 359/434] net: wireless: intel: iwlwifi: fix GRO_NORMAL packet stalling
    Date
    From: Alexander Lobakin <alobakin@dlink.ru>

    [ Upstream commit b167191e2a851cb2e4c6ef8b91c83ff73ef41872 ]

    Commit 6570bc79c0df ("net: core: use listified Rx for GRO_NORMAL in
    napi_gro_receive()") has applied batched GRO_NORMAL packets processing
    to all napi_gro_receive() users, including mac80211-based drivers.

    However, this change has led to a regression in iwlwifi driver [1][2] as
    it is required for NAPI users to call napi_complete_done() or
    napi_complete() and the end of every polling iteration, whilst iwlwifi
    doesn't use NAPI scheduling at all and just calls napi_gro_flush().
    In that particular case, packets which have not been already flushed
    from napi->rx_list stall in it until at least next Rx cycle.

    Fix this by adding a manual flushing of the list to iwlwifi driver right
    before napi_gro_flush() call to mimic napi_complete() logics.

    I prefer to open-code gro_normal_list() rather than exporting it for 2
    reasons:
    * to prevent from using it and napi_gro_flush() in any new drivers,
    as it is the *really* bad way to use NAPI that should be avoided;
    * to keep gro_normal_list() static and don't lose any CC optimizations.

    I also don't add the "Fixes:" tag as the mentioned commit was only a
    trigger that only exposed an improper usage of NAPI in this particular
    driver.

    [1] https://lore.kernel.org/netdev/PSXP216MB04388962C411CD0B17A86F47804A0@PSXP216MB0438.KORP216.PROD.OUTLOOK.COM
    [2] https://bugzilla.kernel.org/show_bug.cgi?id=205647

    Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>
    Acked-by: Luca Coelho <luciano.coelho@intel.com>
    Reported-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
    Tested-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
    Reviewed-by: Edward Cree <ecree@solarflare.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/wireless/intel/iwlwifi/pcie/rx.c | 13 +++++++++++--
    1 file changed, 11 insertions(+), 2 deletions(-)

    diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
    index 19dd075f2f63..041dd75ac72b 100644
    --- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
    +++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
    @@ -1429,6 +1429,7 @@ out_err:
    static void iwl_pcie_rx_handle(struct iwl_trans *trans, int queue)
    {
    struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
    + struct napi_struct *napi;
    struct iwl_rxq *rxq;
    u32 r, i, count = 0;
    bool emergency = false;
    @@ -1534,8 +1535,16 @@ out:
    if (unlikely(emergency && count))
    iwl_pcie_rxq_alloc_rbs(trans, GFP_ATOMIC, rxq);

    - if (rxq->napi.poll)
    - napi_gro_flush(&rxq->napi, false);
    + napi = &rxq->napi;
    + if (napi->poll) {
    + if (napi->rx_count) {
    + netif_receive_skb_list(&napi->rx_list);
    + INIT_LIST_HEAD(&napi->rx_list);
    + napi->rx_count = 0;
    + }
    +
    + napi_gro_flush(napi, false);
    + }

    iwl_pcie_rxq_restock(trans, rxq);
    }
    --
    2.20.1


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