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[v2] net: sched: gred: dynamically allocate tc_gred_qopt_offload

Message ID 20211019191544.3063872-1-arnd@kernel.org (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series [v2] net: sched: gred: dynamically allocate tc_gred_qopt_offload | expand

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Commit Message

Arnd Bergmann Oct. 19, 2021, 7:15 p.m. UTC 
From: Arnd Bergmann <arnd@arndb.de>

The tc_gred_qopt_offload structure has grown too big to be on the
stack for 32-bit architectures after recent changes.

net/sched/sch_gred.c:903:13: error: stack frame size (1180) exceeds limit (1024) in 'gred_destroy' [-Werror,-Wframe-larger-than]
net/sched/sch_gred.c:310:13: error: stack frame size (1212) exceeds limit (1024) in 'gred_offload' [-Werror,-Wframe-larger-than]

Use dynamic allocation per qdisc to avoid this.

Fixes: 50dc9a8572aa ("net: sched: Merge Qdisc::bstats and Qdisc::cpu_bstats data types")
Fixes: 67c9e6270f30 ("net: sched: Protect Qdisc::bstats with u64_stats")
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
Hi Jakub,

Not sure if this is what you had in mind, if not it might be easier
if you do it yourself. In particular, adding tc_gred_qopt_offload
to gred_sched directly rather than as a pointer may be easier here,
but that may have other downsides.

Changes in v2:
- allocate structure at init time rather than inside of
  gred_offload()
---
 net/sched/sch_gred.c | 50 ++++++++++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 20 deletions(-)

Comments

Jakub Kicinski Oct. 19, 2021, 10:08 p.m. UTC | #1 
On Tue, 19 Oct 2021 21:15:29 +0200 Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> The tc_gred_qopt_offload structure has grown too big to be on the
> stack for 32-bit architectures after recent changes.
> 
> net/sched/sch_gred.c:903:13: error: stack frame size (1180) exceeds limit (1024) in 'gred_destroy' [-Werror,-Wframe-larger-than]
> net/sched/sch_gred.c:310:13: error: stack frame size (1212) exceeds limit (1024) in 'gred_offload' [-Werror,-Wframe-larger-than]
> 
> Use dynamic allocation per qdisc to avoid this.
> 
> Fixes: 50dc9a8572aa ("net: sched: Merge Qdisc::bstats and Qdisc::cpu_bstats data types")
> Fixes: 67c9e6270f30 ("net: sched: Protect Qdisc::bstats with u64_stats")
> Suggested-by: Jakub Kicinski <kuba@kernel.org>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> Hi Jakub,
> 
> Not sure if this is what you had in mind, if not it might be easier
> if you do it yourself. In particular, adding tc_gred_qopt_offload
> to gred_sched directly rather than as a pointer may be easier here,
> but that may have other downsides.

This is exactly what I had in mind, thanks!

Two minor nits if you're willing to respin, if you feel like you've
spent enough time on this already we can marge as is :)

> -		opt.set.qstats = &sch->qstats;
> +		opt->set.qstats = &sch->qstats;
>  	}
>  
> -	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_GRED, &opt);
> +	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_GRED, opt);
> +
> +	return;

return no longer needed

>  }
>  
>  static int gred_offload_dump_stats(struct Qdisc *sch)

> @@ -754,6 +759,10 @@ static int gred_init(struct Qdisc *sch, struct nlattr *opt,
>  		sch->limit = qdisc_dev(sch)->tx_queue_len
>  		             * psched_mtu(qdisc_dev(sch));

The ops should not change, so I think we can do

	if (qdisc_dev(sch)->netdev_ops->ndo_setup_tc) {

> +	table->opt = kzalloc(sizeof(table->opt), GFP_KERNEL);
> +	if (!table->opt)
> +		return -ENOMEM;
> +
>  	return gred_change_table_def(sch, tb[TCA_GRED_DPS], extack);
>  }
>
Eric Dumazet Oct. 19, 2021, 10:26 p.m. UTC | #2 
On 10/19/21 12:15 PM, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
>  
> @@ -754,6 +759,10 @@ static int gred_init(struct Qdisc *sch, struct nlattr *opt,
>  		sch->limit = qdisc_dev(sch)->tx_queue_len
>  		             * psched_mtu(qdisc_dev(sch));
>  
> +	table->opt = kzalloc(sizeof(table->opt), GFP_KERNEL);

sizeof(*table->opt) ?

> +	if (!table->opt)
> +		return -ENOMEM;
> +
>  	return gred_change_table_def(sch, tb[TCA_GRED_DPS], extack);
>  }
>
diff mbox series

Patch

diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
index 72de08ef8335..d44958f3411a 100644
--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c
@@ -56,6 +56,7 @@  struct gred_sched {
 	u32 		DPs;
 	u32 		def;
 	struct red_vars wred_set;
+	struct tc_gred_qopt_offload *opt;
 };
 
 static inline int gred_wred_mode(struct gred_sched *table)
@@ -311,42 +312,45 @@  static void gred_offload(struct Qdisc *sch, enum tc_gred_command command)
 {
 	struct gred_sched *table = qdisc_priv(sch);
 	struct net_device *dev = qdisc_dev(sch);
-	struct tc_gred_qopt_offload opt = {
-		.command	= command,
-		.handle		= sch->handle,
-		.parent		= sch->parent,
-	};
+	struct tc_gred_qopt_offload *opt = table->opt;
 
 	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
 		return;
 
+	memset(opt, 0, sizeof(*opt));
+	opt->command = command;
+	opt->handle = sch->handle;
+	opt->parent = sch->parent;
+
 	if (command == TC_GRED_REPLACE) {
 		unsigned int i;
 
-		opt.set.grio_on = gred_rio_mode(table);
-		opt.set.wred_on = gred_wred_mode(table);
-		opt.set.dp_cnt = table->DPs;
-		opt.set.dp_def = table->def;
+		opt->set.grio_on = gred_rio_mode(table);
+		opt->set.wred_on = gred_wred_mode(table);
+		opt->set.dp_cnt = table->DPs;
+		opt->set.dp_def = table->def;
 
 		for (i = 0; i < table->DPs; i++) {
 			struct gred_sched_data *q = table->tab[i];
 
 			if (!q)
 				continue;
-			opt.set.tab[i].present = true;
-			opt.set.tab[i].limit = q->limit;
-			opt.set.tab[i].prio = q->prio;
-			opt.set.tab[i].min = q->parms.qth_min >> q->parms.Wlog;
-			opt.set.tab[i].max = q->parms.qth_max >> q->parms.Wlog;
-			opt.set.tab[i].is_ecn = gred_use_ecn(q);
-			opt.set.tab[i].is_harddrop = gred_use_harddrop(q);
-			opt.set.tab[i].probability = q->parms.max_P;
-			opt.set.tab[i].backlog = &q->backlog;
+			opt->set.tab[i].present = true;
+			opt->set.tab[i].limit = q->limit;
+			opt->set.tab[i].prio = q->prio;
+			opt->set.tab[i].min = q->parms.qth_min >> q->parms.Wlog;
+			opt->set.tab[i].max = q->parms.qth_max >> q->parms.Wlog;
+			opt->set.tab[i].is_ecn = gred_use_ecn(q);
+			opt->set.tab[i].is_harddrop = gred_use_harddrop(q);
+			opt->set.tab[i].probability = q->parms.max_P;
+			opt->set.tab[i].backlog = &q->backlog;
 		}
-		opt.set.qstats = &sch->qstats;
+		opt->set.qstats = &sch->qstats;
 	}
 
-	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_GRED, &opt);
+	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_GRED, opt);
+
+	return;
 }
 
 static int gred_offload_dump_stats(struct Qdisc *sch)
@@ -731,6 +735,7 @@  static int gred_change(struct Qdisc *sch, struct nlattr *opt,
 static int gred_init(struct Qdisc *sch, struct nlattr *opt,
 		     struct netlink_ext_ack *extack)
 {
+	struct gred_sched *table = qdisc_priv(sch);
 	struct nlattr *tb[TCA_GRED_MAX + 1];
 	int err;
 
@@ -754,6 +759,10 @@  static int gred_init(struct Qdisc *sch, struct nlattr *opt,
 		sch->limit = qdisc_dev(sch)->tx_queue_len
 		             * psched_mtu(qdisc_dev(sch));
 
+	table->opt = kzalloc(sizeof(table->opt), GFP_KERNEL);
+	if (!table->opt)
+		return -ENOMEM;
+
 	return gred_change_table_def(sch, tb[TCA_GRED_DPS], extack);
 }
 
@@ -910,6 +919,7 @@  static void gred_destroy(struct Qdisc *sch)
 			gred_destroy_vq(table->tab[i]);
 	}
 	gred_offload(sch, TC_GRED_DESTROY);
+	kfree(table->opt);
 }
 
 static struct Qdisc_ops gred_qdisc_ops __read_mostly = {