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    Subject[PATCH 5.4 025/178] sch_cake: don't call diffserv parsing code when it is not needed
    Date
    From: Toke Høiland-Jørgensen <toke@redhat.com>

    [ Upstream commit 8c95eca0bb8c4bd2231a0d581f1ad0d50c90488c ]

    As a further optimisation of the diffserv parsing codepath, we can skip it
    entirely if CAKE is configured to neither use diffserv-based
    classification, nor to zero out the diffserv bits.

    Fixes: c87b4ecdbe8d ("sch_cake: Make sure we can write the IP header before changing DSCP bits")
    Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/sched/sch_cake.c | 13 +++++++++----
    1 file changed, 9 insertions(+), 4 deletions(-)

    diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
    index 8020d0829f1a9..e1b93ff79ab53 100644
    --- a/net/sched/sch_cake.c
    +++ b/net/sched/sch_cake.c
    @@ -1515,7 +1515,7 @@ static unsigned int cake_drop(struct Qdisc *sch, struct sk_buff **to_free)
    return idx + (tin << 16);
    }

    -static u8 cake_handle_diffserv(struct sk_buff *skb, u16 wash)
    +static u8 cake_handle_diffserv(struct sk_buff *skb, bool wash)
    {
    const int offset = skb_network_offset(skb);
    u16 *buf, buf_;
    @@ -1576,14 +1576,17 @@ static struct cake_tin_data *cake_select_tin(struct Qdisc *sch,
    {
    struct cake_sched_data *q = qdisc_priv(sch);
    u32 tin, mark;
    + bool wash;
    u8 dscp;

    /* Tin selection: Default to diffserv-based selection, allow overriding
    - * using firewall marks or skb->priority.
    + * using firewall marks or skb->priority. Call DSCP parsing early if
    + * wash is enabled, otherwise defer to below to skip unneeded parsing.
    */
    - dscp = cake_handle_diffserv(skb,
    - q->rate_flags & CAKE_FLAG_WASH);
    mark = (skb->mark & q->fwmark_mask) >> q->fwmark_shft;
    + wash = !!(q->rate_flags & CAKE_FLAG_WASH);
    + if (wash)
    + dscp = cake_handle_diffserv(skb, wash);

    if (q->tin_mode == CAKE_DIFFSERV_BESTEFFORT)
    tin = 0;
    @@ -1597,6 +1600,8 @@ static struct cake_tin_data *cake_select_tin(struct Qdisc *sch,
    tin = q->tin_order[TC_H_MIN(skb->priority) - 1];

    else {
    + if (!wash)
    + dscp = cake_handle_diffserv(skb, wash);
    tin = q->tin_index[dscp];

    if (unlikely(tin >= q->tin_cnt))
    --
    2.25.1
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