net/sched: cake: avoid separate allocation of struct cake_sched_config

Paolo pointed out that we can avoid separately allocating struct
cake_sched_config even in the non-mq case, by embedding it into struct
cake_sched_data. This reduces the complexity of the logic that swaps the
pointers and frees the old value, at the cost of adding 56 bytes to the
latter. Since cake_sched_data is already almost 17k bytes, this seems
like a reasonable tradeoff.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Fixes: bc0ce2bad36c ("net/sched: sch_cake: Factor out config variables into separate struct")
Link: https://patch.msgid.link/20260113143157.2581680-1-toke@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
index e30ef7f8ee6862a916acc06e568e37f35fd675b1..fd56b7d883014e834f22a0a7b981bcd48e6a4227 100644 (file)
--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -221,6 +221,7 @@ struct cake_sched_data {
        struct tcf_block *block;
        struct cake_tin_data *tins;
        struct cake_sched_config *config;
+       struct cake_sched_config initial_config;
 
        struct cake_heap_entry overflow_heap[CAKE_QUEUES * CAKE_MAX_TINS];
 
@@ -2798,8 +2799,6 @@ static void cake_destroy(struct Qdisc *sch)
        qdisc_watchdog_cancel(&q->watchdog);
        tcf_block_put(q->block);
        kvfree(q->tins);
-       if (q->config && !q->config->is_shared)
-               kvfree(q->config);
 }
 
 static void cake_config_init(struct cake_sched_config *q, bool is_shared)
@@ -2822,13 +2821,9 @@ static int cake_init(struct Qdisc *sch, struct nlattr *opt,
                     struct netlink_ext_ack *extack)
 {
        struct cake_sched_data *qd = qdisc_priv(sch);
-       struct cake_sched_config *q;
+       struct cake_sched_config *q = &qd->initial_config;
        int i, j, err;
 
-       q = kzalloc(sizeof(*q), GFP_KERNEL);
-       if (!q)
-               return -ENOMEM;
-
        cake_config_init(q, false);
 
        sch->limit = 10240;
@@ -2842,14 +2837,13 @@ static int cake_init(struct Qdisc *sch, struct nlattr *opt,
 
        if (opt) {
                err = cake_change(sch, opt, extack);
-
                if (err)
-                       goto err;
+                       return err;
        }
 
        err = tcf_block_get(&qd->block, &qd->filter_list, sch, extack);
        if (err)
-               goto err;
+               return err;
 
        quantum_div[0] = ~0;
        for (i = 1; i <= CAKE_QUEUES; i++)
@@ -2857,10 +2851,8 @@ static int cake_init(struct Qdisc *sch, struct nlattr *opt,
 
        qd->tins = kvcalloc(CAKE_MAX_TINS, sizeof(struct cake_tin_data),
                            GFP_KERNEL);
-       if (!qd->tins) {
-               err = -ENOMEM;
-               goto err;
-       }
+       if (!qd->tins)
+               return -ENOMEM;
 
        for (i = 0; i < CAKE_MAX_TINS; i++) {
                struct cake_tin_data *b = qd->tins + i;
@@ -2893,22 +2885,13 @@ static int cake_init(struct Qdisc *sch, struct nlattr *opt,
        qd->last_checked_active = 0;
 
        return 0;
-err:
-       kvfree(qd->config);
-       qd->config = NULL;
-       return err;
 }
 
 static void cake_config_replace(struct Qdisc *sch, struct cake_sched_config *cfg)
 {
        struct cake_sched_data *qd = qdisc_priv(sch);
-       struct cake_sched_config *q = qd->config;
 
        qd->config = cfg;
-
-       if (!q->is_shared)
-               kvfree(q);
-
        cake_reconfigure(sch);
 }