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[PATCH net 5/6] net/sched: Refactor qdisc_graft() for ingress and clsact Qdiscs

Peilin Ye posted 6 patches 2 years, 9 months ago
There is a newer version of this series
[PATCH net 5/6] net/sched: Refactor qdisc_graft() for ingress and clsact Qdiscs
Posted by Peilin Ye 2 years, 9 months ago 
Grafting ingress and clsact Qdiscs does not need a for-loop in
qdisc_graft().  Refactor it.  No functional changes intended.

Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
---
 net/sched/sch_api.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 49b9c1bbfdd9..f72a581666a2 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1073,12 +1073,12 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
 
 	if (parent == NULL) {
 		unsigned int i, num_q, ingress;
+		struct netdev_queue *dev_queue;
 
 		ingress = 0;
 		num_q = dev->num_tx_queues;
 		if ((q && q->flags & TCQ_F_INGRESS) ||
 		    (new && new->flags & TCQ_F_INGRESS)) {
-			num_q = 1;
 			ingress = 1;
 			if (!dev_ingress_queue(dev)) {
 				NL_SET_ERR_MSG(extack, "Device does not have an ingress queue");
@@ -1094,18 +1094,18 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
 		if (new && new->ops->attach && !ingress)
 			goto skip;
 
-		for (i = 0; i < num_q; i++) {
-			struct netdev_queue *dev_queue = dev_ingress_queue(dev);
-
-			if (!ingress)
+		if (!ingress) {
+			for (i = 0; i < num_q; i++) {
 				dev_queue = netdev_get_tx_queue(dev, i);
+				old = dev_graft_qdisc(dev_queue, new);
 
-			old = dev_graft_qdisc(dev_queue, new);
-			if (new && i > 0)
-				qdisc_refcount_inc(new);
-
-			if (!ingress)
+				if (new && i > 0)
+					qdisc_refcount_inc(new);
 				qdisc_put(old);
+			}
+		} else {
+			dev_queue = dev_ingress_queue(dev);
+			old = dev_graft_qdisc(dev_queue, new);
 		}
 
 skip:
-- 
2.20.1
Re: [PATCH net 5/6] net/sched: Refactor qdisc_graft() for ingress and clsact Qdiscs
Posted by Pedro Tammela 2 years, 9 months ago 
On 05/05/2023 21:15, Peilin Ye wrote:
> Grafting ingress and clsact Qdiscs does not need a for-loop in
> qdisc_graft().  Refactor it.  No functional changes intended.
> 
> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>

Just a FYI:
If you decide to keep this refactoring, it will need to be back ported
together with the subsequent fix.
I would personally leave it to net-next.

Thanks for chasing this!

Tested-by: Pedro Tammela <pctammela@mojatatu.com>

> ---
>   net/sched/sch_api.c | 20 ++++++++++----------
>   1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> index 49b9c1bbfdd9..f72a581666a2 100644
> --- a/net/sched/sch_api.c
> +++ b/net/sched/sch_api.c
> @@ -1073,12 +1073,12 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
>   
>   	if (parent == NULL) {
>   		unsigned int i, num_q, ingress;
> +		struct netdev_queue *dev_queue;
>   
>   		ingress = 0;
>   		num_q = dev->num_tx_queues;
>   		if ((q && q->flags & TCQ_F_INGRESS) ||
>   		    (new && new->flags & TCQ_F_INGRESS)) {
> -			num_q = 1;
>   			ingress = 1;
>   			if (!dev_ingress_queue(dev)) {
>   				NL_SET_ERR_MSG(extack, "Device does not have an ingress queue");
> @@ -1094,18 +1094,18 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
>   		if (new && new->ops->attach && !ingress)
>   			goto skip;
>   
> -		for (i = 0; i < num_q; i++) {
> -			struct netdev_queue *dev_queue = dev_ingress_queue(dev);
> -
> -			if (!ingress)
> +		if (!ingress) {
> +			for (i = 0; i < num_q; i++) {
>   				dev_queue = netdev_get_tx_queue(dev, i);
> +				old = dev_graft_qdisc(dev_queue, new);
>   
> -			old = dev_graft_qdisc(dev_queue, new);
> -			if (new && i > 0)
> -				qdisc_refcount_inc(new);
> -
> -			if (!ingress)
> +				if (new && i > 0)
> +					qdisc_refcount_inc(new);
>   				qdisc_put(old);
> +			}
> +		} else {
> +			dev_queue = dev_ingress_queue(dev);
> +			old = dev_graft_qdisc(dev_queue, new);
>   		}
>   
>   skip:
Re: [PATCH net 5/6] net/sched: Refactor qdisc_graft() for ingress and clsact Qdiscs
Posted by Jamal Hadi Salim 2 years, 9 months ago 
On Fri, May 5, 2023 at 8:15 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>
> Grafting ingress and clsact Qdiscs does not need a for-loop in
> qdisc_graft().  Refactor it.  No functional changes intended.
>
> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>

Fixed John's email address.

This one i am not so sure;  num_q = 1 implies it will run on the for
loop only once. I am not sure it improves readability either. Anyways
for the effort you put into it i am tossing a coin and saying:
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>

cheers,
jamal


>  net/sched/sch_api.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> index 49b9c1bbfdd9..f72a581666a2 100644
> --- a/net/sched/sch_api.c
> +++ b/net/sched/sch_api.c
> @@ -1073,12 +1073,12 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
>
>         if (parent == NULL) {
>                 unsigned int i, num_q, ingress;
> +               struct netdev_queue *dev_queue;
>
>                 ingress = 0;
>                 num_q = dev->num_tx_queues;
>                 if ((q && q->flags & TCQ_F_INGRESS) ||
>                     (new && new->flags & TCQ_F_INGRESS)) {
> -                       num_q = 1;
>                         ingress = 1;
>                         if (!dev_ingress_queue(dev)) {
>                                 NL_SET_ERR_MSG(extack, "Device does not have an ingress queue");
> @@ -1094,18 +1094,18 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
>                 if (new && new->ops->attach && !ingress)
>                         goto skip;
>
> -               for (i = 0; i < num_q; i++) {
> -                       struct netdev_queue *dev_queue = dev_ingress_queue(dev);
> -
> -                       if (!ingress)
> +               if (!ingress) {
> +                       for (i = 0; i < num_q; i++) {
>                                 dev_queue = netdev_get_tx_queue(dev, i);
> +                               old = dev_graft_qdisc(dev_queue, new);
>
> -                       old = dev_graft_qdisc(dev_queue, new);
> -                       if (new && i > 0)
> -                               qdisc_refcount_inc(new);
> -
> -                       if (!ingress)
> +                               if (new && i > 0)
> +                                       qdisc_refcount_inc(new);
>                                 qdisc_put(old);
> +                       }
> +               } else {
> +                       dev_queue = dev_ingress_queue(dev);
> +                       old = dev_graft_qdisc(dev_queue, new);
>                 }
>
>  skip:
> --
> 2.20.1
>
Re: [PATCH net 5/6] net/sched: Refactor qdisc_graft() for ingress and clsact Qdiscs
Posted by Peilin Ye 2 years, 9 months ago 
On Mon, May 08, 2023 at 07:29:26AM -0400, Jamal Hadi Salim wrote:
> On Fri, May 5, 2023 at 8:15 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
> >
> > Grafting ingress and clsact Qdiscs does not need a for-loop in
> > qdisc_graft().  Refactor it.  No functional changes intended.
> 
> This one i am not so sure;  num_q = 1 implies it will run on the for
> loop only once. I am not sure it improves readability either. Anyways
> for the effort you put into it i am tossing a coin and saying:
> Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>

Yeah, it doesn't make much difference itself.  I'm just afraid that,
without [5/6], [6/6] would look like:

		for (i = 0; i < num_q; i++) {
			if (!ingress) {
				dev_queue = netdev_get_tx_queue(dev, i);
				old = dev_graft_qdisc(dev_queue, new);
			else {
				old = dev_graft_qdisc(dev_queue, NULL);
			}

			if (new && i > 0)
				qdisc_refcount_inc(new);

			if (!ingress) {
				qdisc_put(old);
			} else {
                                /* {ingress,clsact}_destroy() "old" before grafting "new" to avoid
                                 * unprotected concurrent accesses to net_device::miniq_{in,e}gress
                                 * pointer(s) in mini_qdisc_pair_swap().
                                 */
				qdisc_notify(net, skb, n, classid, old, new, extack);
				qdisc_destroy(old);
			}

			if (ingress)
				dev_graft_qdisc(dev_queue, new);
		}

The "!ingress" path doesn't share a single line with "ingress", which
looks a bit weird to me.  Personally I'd like to keep [5/6].

Thanks,
Peilin Ye

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