![Vlad Buslov](/assets/img/avatar_default.png)
Recent changes that removed rtnl dependency from rules update path of tc
also made tcf_block_put() function sleeping. This function is called from
ops->destroy() of several Qdisc implementations, which in turn is called by
qdisc_put(). Some Qdiscs call qdisc_put() while holding sch tree spinlock,
which results sleeping-while-atomic BUG.
Steps to reproduce for multiq:
tc qdisc add dev ens1f0 root handle 1: multiq
tc qdisc add dev ens1f0 parent 1:10 handle 50: sfq perturb 10
ethtool -L ens1f0 combined 2
tc qdisc change dev ens1f0 root handle 1: multiq
Resulting dmesg:
[ 5539.419344] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:909
[ 5539.420945] in_atomic(): 1, irqs_disabled(): 0, pid: 27658, name: tc
[ 5539.422435] INFO: lockdep is turned off.
[ 5539.423904] CPU: 21 PID: 27658 Comm: tc Tainted: G W 5.3.0-rc8+ #721
[ 5539.425400] Hardware name: Supermicro SYS-2028TP-DECR/X10DRT-P, BIOS 2.0b 03/30/2017
[ 5539.426911] Call Trace:
[ 5539.428380] dump_stack+0x85/0xc0
[ 5539.429823] ___might_sleep.cold+0xac/0xbc
[ 5539.431262] __mutex_lock+0x5b/0x960
[ 5539.432682] ? tcf_chain0_head_change_cb_del.isra.0+0x1b/0xf0
[ 5539.434103] ? __nla_validate_parse+0x51/0x840
[ 5539.435493] ? tcf_chain0_head_change_cb_del.isra.0+0x1b/0xf0
[ 5539.436903] tcf_chain0_head_change_cb_del.isra.0+0x1b/0xf0
[ 5539.438327] tcf_block_put_ext.part.0+0x21/0x50
[ 5539.439752] tcf_block_put+0x50/0x70
[ 5539.441165] sfq_destroy+0x15/0x50 [sch_sfq]
[ 5539.442570] qdisc_destroy+0x5f/0x160
[ 5539.444000] multiq_tune+0x14a/0x420 [sch_multiq]
[ 5539.445421] tc_modify_qdisc+0x324/0x840
[ 5539.446841] rtnetlink_rcv_msg+0x170/0x4b0
[ 5539.448269] ? netlink_deliver_tap+0x95/0x400
[ 5539.449691] ? rtnl_dellink+0x2d0/0x2d0
[ 5539.451116] netlink_rcv_skb+0x49/0x110
[ 5539.452522] netlink_unicast+0x171/0x200
[ 5539.453914] netlink_sendmsg+0x224/0x3f0
[ 5539.455304] sock_sendmsg+0x5e/0x60
[ 5539.456686] ___sys_sendmsg+0x2ae/0x330
[ 5539.458071] ? ___sys_recvmsg+0x159/0x1f0
[ 5539.459461] ? do_wp_page+0x9c/0x790
[ 5539.460846] ? __handle_mm_fault+0xcd3/0x19e0
[ 5539.462263] __sys_sendmsg+0x59/0xa0
[ 5539.463661] do_syscall_64+0x5c/0xb0
[ 5539.465044] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 5539.466454] RIP: 0033:0x7f1fe08177b8
[ 5539.467863] Code: 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 65 8f 0c 00 8b 00 85 c0 75 17 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 48 83 ec 28 89 5
4
[ 5539.470906] RSP: 002b:00007ffe812de5d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[ 5539.472483] RAX: ffffffffffffffda RBX: 000000005d8135e3 RCX: 00007f1fe08177b8
[ 5539.474069] RDX: 0000000000000000 RSI: 00007ffe812de640 RDI: 0000000000000003
[ 5539.475655] RBP: 0000000000000000 R08: 0000000000000001 R09: 000000000182e9b0
[ 5539.477203] R10: 0000000000404eda R11: 0000000000000246 R12: 0000000000000001
[ 5539.478699] R13: 000000000047f640 R14: 0000000000000000 R15: 0000000000000000
Rearrange locking in multiq_tune() in following ways:
- In loop that removes Qdiscs from disabled queues, call
qdisc_purge_queue() instead of qdisc_tree_flush_backlog() on Qdisc that
is being destroyed. Save the Qdisc in temporary allocated array and call
qdisc_put() on each element of the array after sch tree lock is released.
This is safe to do because Qdiscs have already been reset by
qdisc_purge_queue() inside sch tree lock critical section.
- Do the same change for second loop that initializes Qdiscs for newly
enabled queues in multiq_tune() function. Since sch tree lock is obtained
and released on each iteration of this loop, just call qdisc_put()
directly outside of critical section. Don't verify that old Qdisc is not
noop_qdisc before releasing reference to it because such check is already
performed by qdisc_put*() functions.
Fixes: c266f64dbf
("net: sched: protect block state with mutex")
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
422 lines
8.8 KiB
C
422 lines
8.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) 2008, Intel Corporation.
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*
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* Author: Alexander Duyck <alexander.h.duyck@intel.com>
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*/
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/errno.h>
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#include <linux/skbuff.h>
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#include <net/netlink.h>
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#include <net/pkt_sched.h>
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#include <net/pkt_cls.h>
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struct multiq_sched_data {
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u16 bands;
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u16 max_bands;
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u16 curband;
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struct tcf_proto __rcu *filter_list;
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struct tcf_block *block;
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struct Qdisc **queues;
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};
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static struct Qdisc *
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multiq_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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u32 band;
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struct tcf_result res;
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struct tcf_proto *fl = rcu_dereference_bh(q->filter_list);
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int err;
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*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
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err = tcf_classify(skb, fl, &res, false);
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#ifdef CONFIG_NET_CLS_ACT
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switch (err) {
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case TC_ACT_STOLEN:
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case TC_ACT_QUEUED:
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case TC_ACT_TRAP:
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*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
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/* fall through */
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case TC_ACT_SHOT:
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return NULL;
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}
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#endif
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band = skb_get_queue_mapping(skb);
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if (band >= q->bands)
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return q->queues[0];
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return q->queues[band];
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}
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static int
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multiq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
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struct sk_buff **to_free)
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{
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struct Qdisc *qdisc;
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int ret;
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qdisc = multiq_classify(skb, sch, &ret);
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#ifdef CONFIG_NET_CLS_ACT
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if (qdisc == NULL) {
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if (ret & __NET_XMIT_BYPASS)
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qdisc_qstats_drop(sch);
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__qdisc_drop(skb, to_free);
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return ret;
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}
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#endif
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ret = qdisc_enqueue(skb, qdisc, to_free);
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if (ret == NET_XMIT_SUCCESS) {
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sch->q.qlen++;
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return NET_XMIT_SUCCESS;
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}
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if (net_xmit_drop_count(ret))
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qdisc_qstats_drop(sch);
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return ret;
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}
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static struct sk_buff *multiq_dequeue(struct Qdisc *sch)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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struct Qdisc *qdisc;
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struct sk_buff *skb;
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int band;
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for (band = 0; band < q->bands; band++) {
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/* cycle through bands to ensure fairness */
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q->curband++;
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if (q->curband >= q->bands)
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q->curband = 0;
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/* Check that target subqueue is available before
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* pulling an skb to avoid head-of-line blocking.
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*/
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if (!netif_xmit_stopped(
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netdev_get_tx_queue(qdisc_dev(sch), q->curband))) {
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qdisc = q->queues[q->curband];
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skb = qdisc->dequeue(qdisc);
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if (skb) {
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qdisc_bstats_update(sch, skb);
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sch->q.qlen--;
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return skb;
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}
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}
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}
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return NULL;
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}
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static struct sk_buff *multiq_peek(struct Qdisc *sch)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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unsigned int curband = q->curband;
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struct Qdisc *qdisc;
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struct sk_buff *skb;
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int band;
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for (band = 0; band < q->bands; band++) {
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/* cycle through bands to ensure fairness */
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curband++;
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if (curband >= q->bands)
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curband = 0;
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/* Check that target subqueue is available before
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* pulling an skb to avoid head-of-line blocking.
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*/
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if (!netif_xmit_stopped(
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netdev_get_tx_queue(qdisc_dev(sch), curband))) {
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qdisc = q->queues[curband];
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skb = qdisc->ops->peek(qdisc);
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if (skb)
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return skb;
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}
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}
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return NULL;
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}
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static void
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multiq_reset(struct Qdisc *sch)
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{
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u16 band;
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struct multiq_sched_data *q = qdisc_priv(sch);
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for (band = 0; band < q->bands; band++)
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qdisc_reset(q->queues[band]);
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sch->q.qlen = 0;
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q->curband = 0;
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}
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static void
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multiq_destroy(struct Qdisc *sch)
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{
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int band;
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struct multiq_sched_data *q = qdisc_priv(sch);
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tcf_block_put(q->block);
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for (band = 0; band < q->bands; band++)
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qdisc_put(q->queues[band]);
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kfree(q->queues);
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}
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static int multiq_tune(struct Qdisc *sch, struct nlattr *opt,
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struct netlink_ext_ack *extack)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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struct tc_multiq_qopt *qopt;
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struct Qdisc **removed;
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int i, n_removed = 0;
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if (!netif_is_multiqueue(qdisc_dev(sch)))
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return -EOPNOTSUPP;
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if (nla_len(opt) < sizeof(*qopt))
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return -EINVAL;
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qopt = nla_data(opt);
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qopt->bands = qdisc_dev(sch)->real_num_tx_queues;
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removed = kmalloc(sizeof(*removed) * (q->max_bands - q->bands),
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GFP_KERNEL);
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if (!removed)
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return -ENOMEM;
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sch_tree_lock(sch);
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q->bands = qopt->bands;
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for (i = q->bands; i < q->max_bands; i++) {
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if (q->queues[i] != &noop_qdisc) {
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struct Qdisc *child = q->queues[i];
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q->queues[i] = &noop_qdisc;
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qdisc_purge_queue(child);
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removed[n_removed++] = child;
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}
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}
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sch_tree_unlock(sch);
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for (i = 0; i < n_removed; i++)
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qdisc_put(removed[i]);
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kfree(removed);
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for (i = 0; i < q->bands; i++) {
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if (q->queues[i] == &noop_qdisc) {
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struct Qdisc *child, *old;
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child = qdisc_create_dflt(sch->dev_queue,
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&pfifo_qdisc_ops,
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TC_H_MAKE(sch->handle,
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i + 1), extack);
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if (child) {
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sch_tree_lock(sch);
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old = q->queues[i];
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q->queues[i] = child;
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if (child != &noop_qdisc)
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qdisc_hash_add(child, true);
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if (old != &noop_qdisc)
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qdisc_purge_queue(old);
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sch_tree_unlock(sch);
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qdisc_put(old);
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}
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}
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}
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return 0;
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}
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static int multiq_init(struct Qdisc *sch, struct nlattr *opt,
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struct netlink_ext_ack *extack)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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int i, err;
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q->queues = NULL;
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if (!opt)
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return -EINVAL;
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err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
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if (err)
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return err;
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q->max_bands = qdisc_dev(sch)->num_tx_queues;
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q->queues = kcalloc(q->max_bands, sizeof(struct Qdisc *), GFP_KERNEL);
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if (!q->queues)
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return -ENOBUFS;
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for (i = 0; i < q->max_bands; i++)
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q->queues[i] = &noop_qdisc;
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return multiq_tune(sch, opt, extack);
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}
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static int multiq_dump(struct Qdisc *sch, struct sk_buff *skb)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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unsigned char *b = skb_tail_pointer(skb);
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struct tc_multiq_qopt opt;
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opt.bands = q->bands;
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opt.max_bands = q->max_bands;
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if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
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goto nla_put_failure;
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return skb->len;
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nla_put_failure:
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nlmsg_trim(skb, b);
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return -1;
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}
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static int multiq_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
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struct Qdisc **old, struct netlink_ext_ack *extack)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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unsigned long band = arg - 1;
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if (new == NULL)
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new = &noop_qdisc;
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*old = qdisc_replace(sch, new, &q->queues[band]);
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return 0;
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}
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static struct Qdisc *
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multiq_leaf(struct Qdisc *sch, unsigned long arg)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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unsigned long band = arg - 1;
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return q->queues[band];
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}
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static unsigned long multiq_find(struct Qdisc *sch, u32 classid)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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unsigned long band = TC_H_MIN(classid);
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if (band - 1 >= q->bands)
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return 0;
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return band;
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}
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static unsigned long multiq_bind(struct Qdisc *sch, unsigned long parent,
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u32 classid)
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{
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return multiq_find(sch, classid);
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}
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static void multiq_unbind(struct Qdisc *q, unsigned long cl)
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{
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}
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static int multiq_dump_class(struct Qdisc *sch, unsigned long cl,
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struct sk_buff *skb, struct tcmsg *tcm)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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tcm->tcm_handle |= TC_H_MIN(cl);
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tcm->tcm_info = q->queues[cl - 1]->handle;
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return 0;
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}
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static int multiq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
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struct gnet_dump *d)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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struct Qdisc *cl_q;
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cl_q = q->queues[cl - 1];
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if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
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d, NULL, &cl_q->bstats) < 0 ||
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qdisc_qstats_copy(d, cl_q) < 0)
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return -1;
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return 0;
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}
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static void multiq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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int band;
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if (arg->stop)
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return;
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for (band = 0; band < q->bands; band++) {
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if (arg->count < arg->skip) {
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arg->count++;
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continue;
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}
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if (arg->fn(sch, band + 1, arg) < 0) {
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arg->stop = 1;
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break;
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}
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arg->count++;
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}
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}
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static struct tcf_block *multiq_tcf_block(struct Qdisc *sch, unsigned long cl,
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struct netlink_ext_ack *extack)
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{
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struct multiq_sched_data *q = qdisc_priv(sch);
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if (cl)
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return NULL;
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return q->block;
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}
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static const struct Qdisc_class_ops multiq_class_ops = {
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.graft = multiq_graft,
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.leaf = multiq_leaf,
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.find = multiq_find,
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.walk = multiq_walk,
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.tcf_block = multiq_tcf_block,
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.bind_tcf = multiq_bind,
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.unbind_tcf = multiq_unbind,
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.dump = multiq_dump_class,
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.dump_stats = multiq_dump_class_stats,
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};
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static struct Qdisc_ops multiq_qdisc_ops __read_mostly = {
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.next = NULL,
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.cl_ops = &multiq_class_ops,
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.id = "multiq",
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.priv_size = sizeof(struct multiq_sched_data),
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.enqueue = multiq_enqueue,
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.dequeue = multiq_dequeue,
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.peek = multiq_peek,
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.init = multiq_init,
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.reset = multiq_reset,
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.destroy = multiq_destroy,
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.change = multiq_tune,
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.dump = multiq_dump,
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.owner = THIS_MODULE,
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};
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static int __init multiq_module_init(void)
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{
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return register_qdisc(&multiq_qdisc_ops);
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}
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static void __exit multiq_module_exit(void)
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{
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unregister_qdisc(&multiq_qdisc_ops);
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}
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module_init(multiq_module_init)
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module_exit(multiq_module_exit)
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MODULE_LICENSE("GPL");
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