netdev - [Patch net v5 1/9] Revert "net/sched: Restrict conditions for adding duplicating netems to qdisc tree"

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Message-Id: <20251126195244.88124-2-xiyou.wangcong@gmail.com>
Date: Wed, 26 Nov 2025 11:52:36 -0800
From: Cong Wang <xiyou.wangcong@...il.com>
To: netdev@...r.kernel.org
Cc: stephen@...workplumber.org,
	kuba@...nel.org,
	Cong Wang <cwang@...tikernel.io>,
	Ji-Soo Chung <jschung2@...ton.me>,
	Gerlinde <lrGerlinde@...lfence.com>
Subject: [Patch net v5 1/9] Revert "net/sched: Restrict conditions for adding duplicating netems to qdisc tree"

From: Cong Wang <cwang@...tikernel.io>

This reverts commit ec8e0e3d7adef940cdf9475e2352c0680189d14e since it
breaks mq+netem.

Reported-by: Ji-Soo Chung <jschung2@...ton.me>
Reported-by: Gerlinde <lrGerlinde@...lfence.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220774
Signed-off-by: Cong Wang <cwang@...tikernel.io>
---
 net/sched/sch_netem.c | 40 ----------------------------------------
 1 file changed, 40 deletions(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index eafc316ae319..fdd79d3ccd8c 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -973,41 +973,6 @@ static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
 	return 0;
 }
 
-static const struct Qdisc_class_ops netem_class_ops;
-
-static int check_netem_in_tree(struct Qdisc *sch, bool duplicates,
-			       struct netlink_ext_ack *extack)
-{
-	struct Qdisc *root, *q;
-	unsigned int i;
-
-	root = qdisc_root_sleeping(sch);
-
-	if (sch != root && root->ops->cl_ops == &netem_class_ops) {
-		if (duplicates ||
-		    ((struct netem_sched_data *)qdisc_priv(root))->duplicate)
-			goto err;
-	}
-
-	if (!qdisc_dev(root))
-		return 0;
-
-	hash_for_each(qdisc_dev(root)->qdisc_hash, i, q, hash) {
-		if (sch != q && q->ops->cl_ops == &netem_class_ops) {
-			if (duplicates ||
-			    ((struct netem_sched_data *)qdisc_priv(q))->duplicate)
-				goto err;
-		}
-	}
-
-	return 0;
-
-err:
-	NL_SET_ERR_MSG(extack,
-		       "netem: cannot mix duplicating netems with other netems in tree");
-	return -EINVAL;
-}
-
 /* Parse netlink message to set options */
 static int netem_change(struct Qdisc *sch, struct nlattr *opt,
 			struct netlink_ext_ack *extack)
@@ -1066,11 +1031,6 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt,
 	q->gap = qopt->gap;
 	q->counter = 0;
 	q->loss = qopt->loss;
-
-	ret = check_netem_in_tree(sch, qopt->duplicate, extack);
-	if (ret)
-		goto unlock;
-
 	q->duplicate = qopt->duplicate;
 
 	/* for compatibility with earlier versions.
-- 
2.34.1