v4.19.13 snapshot.
diff --git a/net/sched/sch_fifo.c b/net/sched/sch_fifo.c
new file mode 100644
index 0000000..24893d3
--- /dev/null
+++ b/net/sched/sch_fifo.c
@@ -0,0 +1,187 @@
+/*
+ * net/sched/sch_fifo.c The simplest FIFO queue.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/skbuff.h>
+#include <net/pkt_sched.h>
+
+/* 1 band FIFO pseudo-"scheduler" */
+
+static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+ struct sk_buff **to_free)
+{
+ if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
+ return qdisc_enqueue_tail(skb, sch);
+
+ return qdisc_drop(skb, sch, to_free);
+}
+
+static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+ struct sk_buff **to_free)
+{
+ if (likely(sch->q.qlen < sch->limit))
+ return qdisc_enqueue_tail(skb, sch);
+
+ return qdisc_drop(skb, sch, to_free);
+}
+
+static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+ struct sk_buff **to_free)
+{
+ unsigned int prev_backlog;
+
+ if (likely(sch->q.qlen < sch->limit))
+ return qdisc_enqueue_tail(skb, sch);
+
+ prev_backlog = sch->qstats.backlog;
+ /* queue full, remove one skb to fulfill the limit */
+ __qdisc_queue_drop_head(sch, &sch->q, to_free);
+ qdisc_qstats_drop(sch);
+ qdisc_enqueue_tail(skb, sch);
+
+ qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
+ return NET_XMIT_CN;
+}
+
+static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
+ struct netlink_ext_ack *extack)
+{
+ bool bypass;
+ bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
+
+ if (opt == NULL) {
+ u32 limit = qdisc_dev(sch)->tx_queue_len;
+
+ if (is_bfifo)
+ limit *= psched_mtu(qdisc_dev(sch));
+
+ sch->limit = limit;
+ } else {
+ struct tc_fifo_qopt *ctl = nla_data(opt);
+
+ if (nla_len(opt) < sizeof(*ctl))
+ return -EINVAL;
+
+ sch->limit = ctl->limit;
+ }
+
+ if (is_bfifo)
+ bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
+ else
+ bypass = sch->limit >= 1;
+
+ if (bypass)
+ sch->flags |= TCQ_F_CAN_BYPASS;
+ else
+ sch->flags &= ~TCQ_F_CAN_BYPASS;
+ return 0;
+}
+
+static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+ struct tc_fifo_qopt opt = { .limit = sch->limit };
+
+ if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
+ goto nla_put_failure;
+ return skb->len;
+
+nla_put_failure:
+ return -1;
+}
+
+struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
+ .id = "pfifo",
+ .priv_size = 0,
+ .enqueue = pfifo_enqueue,
+ .dequeue = qdisc_dequeue_head,
+ .peek = qdisc_peek_head,
+ .init = fifo_init,
+ .reset = qdisc_reset_queue,
+ .change = fifo_init,
+ .dump = fifo_dump,
+ .owner = THIS_MODULE,
+};
+EXPORT_SYMBOL(pfifo_qdisc_ops);
+
+struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
+ .id = "bfifo",
+ .priv_size = 0,
+ .enqueue = bfifo_enqueue,
+ .dequeue = qdisc_dequeue_head,
+ .peek = qdisc_peek_head,
+ .init = fifo_init,
+ .reset = qdisc_reset_queue,
+ .change = fifo_init,
+ .dump = fifo_dump,
+ .owner = THIS_MODULE,
+};
+EXPORT_SYMBOL(bfifo_qdisc_ops);
+
+struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
+ .id = "pfifo_head_drop",
+ .priv_size = 0,
+ .enqueue = pfifo_tail_enqueue,
+ .dequeue = qdisc_dequeue_head,
+ .peek = qdisc_peek_head,
+ .init = fifo_init,
+ .reset = qdisc_reset_queue,
+ .change = fifo_init,
+ .dump = fifo_dump,
+ .owner = THIS_MODULE,
+};
+
+/* Pass size change message down to embedded FIFO */
+int fifo_set_limit(struct Qdisc *q, unsigned int limit)
+{
+ struct nlattr *nla;
+ int ret = -ENOMEM;
+
+ /* Hack to avoid sending change message to non-FIFO */
+ if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
+ return 0;
+
+ nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
+ if (nla) {
+ nla->nla_type = RTM_NEWQDISC;
+ nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
+ ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
+
+ ret = q->ops->change(q, nla, NULL);
+ kfree(nla);
+ }
+ return ret;
+}
+EXPORT_SYMBOL(fifo_set_limit);
+
+struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
+ unsigned int limit,
+ struct netlink_ext_ack *extack)
+{
+ struct Qdisc *q;
+ int err = -ENOMEM;
+
+ q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
+ extack);
+ if (q) {
+ err = fifo_set_limit(q, limit);
+ if (err < 0) {
+ qdisc_destroy(q);
+ q = NULL;
+ }
+ }
+
+ return q ? : ERR_PTR(err);
+}
+EXPORT_SYMBOL(fifo_create_dflt);