3 files changed, 1149 insertions, 0 deletions

diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index a7a5583d4f68..aeaa2110b699 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -239,6 +239,17 @@ config NET_SCH_CHOKE
           To compile this code as a module, choose M here: the
           module will be called sch_choke.
 
+config NET_SCH_QFQ
+        tristate "Quick Fair Queueing scheduler (QFQ)"
+        help
+          Say Y here if you want to use the Quick Fair Queueing Scheduler (QFQ)
+          packet scheduling algorithm.
+
+          To compile this driver as a module, choose M here: the module
+          will be called sch_qfq.
+
+          If unsure, say N.
+
 config NET_SCH_INGRESS
         tristate "Ingress Qdisc"
         depends on NET_CLS_ACT
diff --git a/net/sched/Makefile b/net/sched/Makefile
index 2e77b8dba22e..dc5889c0a15a 100644
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -35,6 +35,7 @@ obj-$(CONFIG_NET_SCH_NETEM)	+= sch_netem.o
 obj-$(CONFIG_NET_SCH_DRR)       += sch_drr.o
 obj-$(CONFIG_NET_SCH_MQPRIO)    += sch_mqprio.o
 obj-$(CONFIG_NET_SCH_CHOKE)     += sch_choke.o
+obj-$(CONFIG_NET_SCH_QFQ)       += sch_qfq.o
 
 obj-$(CONFIG_NET_CLS_U32)       += cls_u32.o
 obj-$(CONFIG_NET_CLS_ROUTE4)    += cls_route.o
diff --git a/net/sched/sch_qfq.c b/net/sched/sch_qfq.c
new file mode 100644
index 000000000000..103343408593
--- /dev/null
+++ b/net/sched/sch_qfq.c
@@ -0,0 +1,1137 @@
+/*
+ * net/sched/sch_qfq.c         Quick Fair Queueing Scheduler.
+ *
+ * Copyright (c) 2009 Fabio Checconi, Luigi Rizzo, and Paolo Valente.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/bitops.h>
+#include <linux/errno.h>
+#include <linux/netdevice.h>
+#include <linux/pkt_sched.h>
+#include <net/sch_generic.h>
+#include <net/pkt_sched.h>
+#include <net/pkt_cls.h>
+
+
+/*  Quick Fair Queueing
+    ===================
+
+    Sources:
+
+    Fabio Checconi, Luigi Rizzo, and Paolo Valente: "QFQ: Efficient
+    Packet Scheduling with Tight Bandwidth Distribution Guarantees."
+
+    See also:
+    http://retis.sssup.it/~fabio/linux/qfq/
+ */
+
+/*
+
+  Virtual time computations.
+
+  S, F and V are all computed in fixed point arithmetic with
+  FRAC_BITS decimal bits.
+
+  QFQ_MAX_INDEX is the maximum index allowed for a group. We need
+        one bit per index.
+  QFQ_MAX_WSHIFT is the maximum power of two supported as a weight.
+
+  The layout of the bits is as below:
+
+                   [ MTU_SHIFT ][      FRAC_BITS    ]
+                   [ MAX_INDEX    ][ MIN_SLOT_SHIFT ]
+                                 ^.__grp->index = 0
+                                 *.__grp->slot_shift
+
+  where MIN_SLOT_SHIFT is derived by difference from the others.
+
+  The max group index corresponds to Lmax/w_min, where
+  Lmax=1<<MTU_SHIFT, w_min = 1 .
+  From this, and knowing how many groups (MAX_INDEX) we want,
+  we can derive the shift corresponding to each group.
+
+  Because we often need to compute
+        F = S + len/w_i  and V = V + len/wsum
+  instead of storing w_i store the value
+        inv_w = (1<<FRAC_BITS)/w_i
+  so we can do F = S + len * inv_w * wsum.
+  We use W_TOT in the formulas so we can easily move between
+  static and adaptive weight sum.
+
+  The per-scheduler-instance data contain all the data structures
+  for the scheduler: bitmaps and bucket lists.
+
+ */
+
+/*
+ * Maximum number of consecutive slots occupied by backlogged classes
+ * inside a group.
+ */
+#define QFQ_MAX_SLOTS   32
+
+/*
+ * Shifts used for class<->group mapping.  We allow class weights that are
+ * in the range [1, 2^MAX_WSHIFT], and we try to map each class i to the
+ * group with the smallest index that can support the L_i / r_i configured
+ * for the class.
+ *
+ * grp->index is the index of the group; and grp->slot_shift
+ * is the shift for the corresponding (scaled) sigma_i.
+ */
+#define QFQ_MAX_INDEX           19
+#define QFQ_MAX_WSHIFT          16
+
+#define QFQ_MAX_WEIGHT          (1<<QFQ_MAX_WSHIFT)
+#define QFQ_MAX_WSUM            (2*QFQ_MAX_WEIGHT)
+
+#define FRAC_BITS               30      /* fixed point arithmetic */
+#define ONE_FP                  (1UL << FRAC_BITS)
+#define IWSUM                   (ONE_FP/QFQ_MAX_WSUM)
+
+#define QFQ_MTU_SHIFT           11
+#define QFQ_MIN_SLOT_SHIFT      (FRAC_BITS + QFQ_MTU_SHIFT - QFQ_MAX_INDEX)
+
+/*
+ * Possible group states.  These values are used as indexes for the bitmaps
+ * array of struct qfq_queue.
+ */
+enum qfq_state { ER, IR, EB, IB, QFQ_MAX_STATE };
+
+struct qfq_group;
+
+struct qfq_class {
+        struct Qdisc_class_common common;
+
+        unsigned int refcnt;
+        unsigned int filter_cnt;
+
+        struct gnet_stats_basic_packed bstats;
+        struct gnet_stats_queue qstats;
+        struct gnet_stats_rate_est rate_est;
+        struct Qdisc *qdisc;
+
+        struct hlist_node next; /* Link for the slot list. */
+        u64 S, F;               /* flow timestamps (exact) */
+
+        /* group we belong to. In principle we would need the index,
+         * which is log_2(lmax/weight), but we never reference it
+         * directly, only the group.
+         */
+        struct qfq_group *grp;
+
+        /* these are copied from the flowset. */
+        u32     inv_w;          /* ONE_FP/weight */
+        u32     lmax;           /* Max packet size for this flow. */
+};
+
+struct qfq_group {
+        u64 S, F;                       /* group timestamps (approx). */
+        unsigned int slot_shift;        /* Slot shift. */
+        unsigned int index;             /* Group index. */
+        unsigned int front;             /* Index of the front slot. */
+        unsigned long full_slots;       /* non-empty slots */
+
+        /* Array of RR lists of active classes. */
+        struct hlist_head slots[QFQ_MAX_SLOTS];
+};
+
+struct qfq_sched {
+        struct tcf_proto *filter_list;
+        struct Qdisc_class_hash clhash;
+
+        u64             V;              /* Precise virtual time. */
+        u32             wsum;           /* weight sum */
+
+        unsigned long bitmaps[QFQ_MAX_STATE];       /* Group bitmaps. */
+        struct qfq_group groups[QFQ_MAX_INDEX + 1]; /* The groups. */
+};
+
+static struct qfq_class *qfq_find_class(struct Qdisc *sch, u32 classid)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct Qdisc_class_common *clc;
+
+        clc = qdisc_class_find(&q->clhash, classid);
+        if (clc == NULL)
+                return NULL;
+        return container_of(clc, struct qfq_class, common);
+}
+
+static void qfq_purge_queue(struct qfq_class *cl)
+{
+        unsigned int len = cl->qdisc->q.qlen;
+
+        qdisc_reset(cl->qdisc);
+        qdisc_tree_decrease_qlen(cl->qdisc, len);
+}
+
+static const struct nla_policy qfq_policy[TCA_QFQ_MAX + 1] = {
+        [TCA_QFQ_WEIGHT] = { .type = NLA_U32 },
+        [TCA_QFQ_LMAX] = { .type = NLA_U32 },
+};
+
+/*
+ * Calculate a flow index, given its weight and maximum packet length.
+ * index = log_2(maxlen/weight) but we need to apply the scaling.
+ * This is used only once at flow creation.
+ */
+static int qfq_calc_index(u32 inv_w, unsigned int maxlen)
+{
+        u64 slot_size = (u64)maxlen * inv_w;
+        unsigned long size_map;
+        int index = 0;
+
+        size_map = slot_size >> QFQ_MIN_SLOT_SHIFT;
+        if (!size_map)
+                goto out;
+
+        index = __fls(size_map) + 1;    /* basically a log_2 */
+        index -= !(slot_size - (1ULL << (index + QFQ_MIN_SLOT_SHIFT - 1)));
+
+        if (index < 0)
+                index = 0;
+out:
+        pr_debug("qfq calc_index: W = %lu, L = %u, I = %d\n",
+                 (unsigned long) ONE_FP/inv_w, maxlen, index);
+
+        return index;
+}
+
+static int qfq_change_class(struct Qdisc *sch, u32 classid, u32 parentid,
+                            struct nlattr **tca, unsigned long *arg)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_class *cl = (struct qfq_class *)*arg;
+        struct nlattr *tb[TCA_QFQ_MAX + 1];
+        u32 weight, lmax, inv_w;
+        int i, err;
+
+        if (tca[TCA_OPTIONS] == NULL) {
+                pr_notice("qfq: no options\n");
+                return -EINVAL;
+        }
+
+        err = nla_parse_nested(tb, TCA_QFQ_MAX, tca[TCA_OPTIONS], qfq_policy);
+        if (err < 0)
+                return err;
+
+        if (tb[TCA_QFQ_WEIGHT]) {
+                weight = nla_get_u32(tb[TCA_QFQ_WEIGHT]);
+                if (!weight || weight > (1UL << QFQ_MAX_WSHIFT)) {
+                        pr_notice("qfq: invalid weight %u\n", weight);
+                        return -EINVAL;
+                }
+        } else
+                weight = 1;
+
+        inv_w = ONE_FP / weight;
+        weight = ONE_FP / inv_w;
+        if (q->wsum + weight > QFQ_MAX_WSUM) {
+                pr_notice("qfq: total weight out of range (%u + %u)\n",
+                          weight, q->wsum);
+                return -EINVAL;
+        }
+
+        if (tb[TCA_QFQ_LMAX]) {
+                lmax = nla_get_u32(tb[TCA_QFQ_LMAX]);
+                if (!lmax || lmax > (1UL << QFQ_MTU_SHIFT)) {
+                        pr_notice("qfq: invalid max length %u\n", lmax);
+                        return -EINVAL;
+                }
+        } else
+                lmax = 1UL << QFQ_MTU_SHIFT;
+
+        if (cl != NULL) {
+                if (tca[TCA_RATE]) {
+                        err = gen_replace_estimator(&cl->bstats, &cl->rate_est,
+                                                    qdisc_root_sleeping_lock(sch),
+                                                    tca[TCA_RATE]);
+                        if (err)
+                                return err;
+                }
+
+                sch_tree_lock(sch);
+                if (tb[TCA_QFQ_WEIGHT]) {
+                        q->wsum = weight - ONE_FP / cl->inv_w;
+                        cl->inv_w = inv_w;
+                }
+                sch_tree_unlock(sch);
+
+                return 0;
+        }
+
+        cl = kzalloc(sizeof(struct qfq_class), GFP_KERNEL);
+        if (cl == NULL)
+                return -ENOBUFS;
+
+        cl->refcnt = 1;
+        cl->common.classid = classid;
+        cl->lmax = lmax;
+        cl->inv_w = inv_w;
+        i = qfq_calc_index(cl->inv_w, cl->lmax);
+
+        cl->grp = &q->groups[i];
+        q->wsum += weight;
+
+        cl->qdisc = qdisc_create_dflt(sch->dev_queue,
+                                      &pfifo_qdisc_ops, classid);
+        if (cl->qdisc == NULL)
+                cl->qdisc = &noop_qdisc;
+
+        if (tca[TCA_RATE]) {
+                err = gen_new_estimator(&cl->bstats, &cl->rate_est,
+                                        qdisc_root_sleeping_lock(sch),
+                                        tca[TCA_RATE]);
+                if (err) {
+                        qdisc_destroy(cl->qdisc);
+                        kfree(cl);
+                        return err;
+                }
+        }
+
+        sch_tree_lock(sch);
+        qdisc_class_hash_insert(&q->clhash, &cl->common);
+        sch_tree_unlock(sch);
+
+        qdisc_class_hash_grow(sch, &q->clhash);
+
+        *arg = (unsigned long)cl;
+        return 0;
+}
+
+static void qfq_destroy_class(struct Qdisc *sch, struct qfq_class *cl)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+
+        if (cl->inv_w) {
+                q->wsum -= ONE_FP / cl->inv_w;
+                cl->inv_w = 0;
+        }
+
+        gen_kill_estimator(&cl->bstats, &cl->rate_est);
+        qdisc_destroy(cl->qdisc);
+        kfree(cl);
+}
+
+static int qfq_delete_class(struct Qdisc *sch, unsigned long arg)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_class *cl = (struct qfq_class *)arg;
+
+        if (cl->filter_cnt > 0)
+                return -EBUSY;
+
+        sch_tree_lock(sch);
+
+        qfq_purge_queue(cl);
+        qdisc_class_hash_remove(&q->clhash, &cl->common);
+
+        BUG_ON(--cl->refcnt == 0);
+        /*
+         * This shouldn't happen: we "hold" one cops->get() when called
+         * from tc_ctl_tclass; the destroy method is done from cops->put().
+         */
+
+        sch_tree_unlock(sch);
+        return 0;
+}
+
+static unsigned long qfq_get_class(struct Qdisc *sch, u32 classid)
+{
+        struct qfq_class *cl = qfq_find_class(sch, classid);
+
+        if (cl != NULL)
+                cl->refcnt++;
+
+        return (unsigned long)cl;
+}
+
+static void qfq_put_class(struct Qdisc *sch, unsigned long arg)
+{
+        struct qfq_class *cl = (struct qfq_class *)arg;
+
+        if (--cl->refcnt == 0)
+                qfq_destroy_class(sch, cl);
+}
+
+static struct tcf_proto **qfq_tcf_chain(struct Qdisc *sch, unsigned long cl)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+
+        if (cl)
+                return NULL;
+
+        return &q->filter_list;
+}
+
+static unsigned long qfq_bind_tcf(struct Qdisc *sch, unsigned long parent,
+                                  u32 classid)
+{
+        struct qfq_class *cl = qfq_find_class(sch, classid);
+
+        if (cl != NULL)
+                cl->filter_cnt++;
+
+        return (unsigned long)cl;
+}
+
+static void qfq_unbind_tcf(struct Qdisc *sch, unsigned long arg)
+{
+        struct qfq_class *cl = (struct qfq_class *)arg;
+
+        cl->filter_cnt--;
+}
+
+static int qfq_graft_class(struct Qdisc *sch, unsigned long arg,
+                           struct Qdisc *new, struct Qdisc **old)
+{
+        struct qfq_class *cl = (struct qfq_class *)arg;
+
+        if (new == NULL) {
+                new = qdisc_create_dflt(sch->dev_queue,
+                                        &pfifo_qdisc_ops, cl->common.classid);
+                if (new == NULL)
+                        new = &noop_qdisc;
+        }
+
+        sch_tree_lock(sch);
+        qfq_purge_queue(cl);
+        *old = cl->qdisc;
+        cl->qdisc = new;
+        sch_tree_unlock(sch);
+        return 0;
+}
+
+static struct Qdisc *qfq_class_leaf(struct Qdisc *sch, unsigned long arg)
+{
+        struct qfq_class *cl = (struct qfq_class *)arg;
+
+        return cl->qdisc;
+}
+
+static int qfq_dump_class(struct Qdisc *sch, unsigned long arg,
+                          struct sk_buff *skb, struct tcmsg *tcm)
+{
+        struct qfq_class *cl = (struct qfq_class *)arg;
+        struct nlattr *nest;
+
+        tcm->tcm_parent = TC_H_ROOT;
+        tcm->tcm_handle = cl->common.classid;
+        tcm->tcm_info   = cl->qdisc->handle;
+
+        nest = nla_nest_start(skb, TCA_OPTIONS);
+        if (nest == NULL)
+                goto nla_put_failure;
+        NLA_PUT_U32(skb, TCA_QFQ_WEIGHT, ONE_FP/cl->inv_w);
+        NLA_PUT_U32(skb, TCA_QFQ_LMAX, cl->lmax);
+        return nla_nest_end(skb, nest);
+
+nla_put_failure:
+        nla_nest_cancel(skb, nest);
+        return -EMSGSIZE;
+}
+
+static int qfq_dump_class_stats(struct Qdisc *sch, unsigned long arg,
+                                struct gnet_dump *d)
+{
+        struct qfq_class *cl = (struct qfq_class *)arg;
+        struct tc_qfq_stats xstats;
+
+        memset(&xstats, 0, sizeof(xstats));
+        cl->qdisc->qstats.qlen = cl->qdisc->q.qlen;
+
+        xstats.weight = ONE_FP/cl->inv_w;
+        xstats.lmax = cl->lmax;
+
+        if (gnet_stats_copy_basic(d, &cl->bstats) < 0 ||
+            gnet_stats_copy_rate_est(d, &cl->bstats, &cl->rate_est) < 0 ||
+            gnet_stats_copy_queue(d, &cl->qdisc->qstats) < 0)
+                return -1;
+
+        return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
+}
+
+static void qfq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_class *cl;
+        struct hlist_node *n;
+        unsigned int i;
+
+        if (arg->stop)
+                return;
+
+        for (i = 0; i < q->clhash.hashsize; i++) {
+                hlist_for_each_entry(cl, n, &q->clhash.hash[i], common.hnode) {
+                        if (arg->count < arg->skip) {
+                                arg->count++;
+                                continue;
+                        }
+                        if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
+                                arg->stop = 1;
+                                return;
+                        }
+                        arg->count++;
+                }
+        }
+}
+
+static struct qfq_class *qfq_classify(struct sk_buff *skb, struct Qdisc *sch,
+                                      int *qerr)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_class *cl;
+        struct tcf_result res;
+        int result;
+
+        if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
+                pr_debug("qfq_classify: found %d\n", skb->priority);
+                cl = qfq_find_class(sch, skb->priority);
+                if (cl != NULL)
+                        return cl;
+        }
+
+        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
+        result = tc_classify(skb, q->filter_list, &res);
+        if (result >= 0) {
+#ifdef CONFIG_NET_CLS_ACT
+                switch (result) {
+                case TC_ACT_QUEUED:
+                case TC_ACT_STOLEN:
+                        *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
+                case TC_ACT_SHOT:
+                        return NULL;
+                }
+#endif
+                cl = (struct qfq_class *)res.class;
+                if (cl == NULL)
+                        cl = qfq_find_class(sch, res.classid);
+                return cl;
+        }
+
+        return NULL;
+}
+
+/* Generic comparison function, handling wraparound. */
+static inline int qfq_gt(u64 a, u64 b)
+{
+        return (s64)(a - b) > 0;
+}
+
+/* Round a precise timestamp to its slotted value. */
+static inline u64 qfq_round_down(u64 ts, unsigned int shift)
+{
+        return ts & ~((1ULL << shift) - 1);
+}
+
+/* return the pointer to the group with lowest index in the bitmap */
+static inline struct qfq_group *qfq_ffs(struct qfq_sched *q,
+                                        unsigned long bitmap)
+{
+        int index = __ffs(bitmap);
+        return &q->groups[index];
+}
+/* Calculate a mask to mimic what would be ffs_from(). */
+static inline unsigned long mask_from(unsigned long bitmap, int from)
+{
+        return bitmap & ~((1UL << from) - 1);
+}
+
+/*
+ * The state computation relies on ER=0, IR=1, EB=2, IB=3
+ * First compute eligibility comparing grp->S, q->V,
+ * then check if someone is blocking us and possibly add EB
+ */
+static int qfq_calc_state(struct qfq_sched *q, const struct qfq_group *grp)
+{
+        /* if S > V we are not eligible */
+        unsigned int state = qfq_gt(grp->S, q->V);
+        unsigned long mask = mask_from(q->bitmaps[ER], grp->index);
+        struct qfq_group *next;
+
+        if (mask) {
+                next = qfq_ffs(q, mask);
+                if (qfq_gt(grp->F, next->F))
+                        state |= EB;
+        }
+
+        return state;
+}
+
+
+/*
+ * In principle
+ *      q->bitmaps[dst] |= q->bitmaps[src] & mask;
+ *      q->bitmaps[src] &= ~mask;
+ * but we should make sure that src != dst
+ */
+static inline void qfq_move_groups(struct qfq_sched *q, unsigned long mask,
+                                   int src, int dst)
+{
+        q->bitmaps[dst] |= q->bitmaps[src] & mask;
+        q->bitmaps[src] &= ~mask;
+}
+
+static void qfq_unblock_groups(struct qfq_sched *q, int index, u64 old_F)
+{
+        unsigned long mask = mask_from(q->bitmaps[ER], index + 1);
+        struct qfq_group *next;
+
+        if (mask) {
+                next = qfq_ffs(q, mask);
+                if (!qfq_gt(next->F, old_F))
+                        return;
+        }
+
+        mask = (1UL << index) - 1;
+        qfq_move_groups(q, mask, EB, ER);
+        qfq_move_groups(q, mask, IB, IR);
+}
+
+/*
+ * perhaps
+ *
+        old_V ^= q->V;
+        old_V >>= QFQ_MIN_SLOT_SHIFT;
+        if (old_V) {
+                ...
+        }
+ *
+ */
+static void qfq_make_eligible(struct qfq_sched *q, u64 old_V)
+{
+        unsigned long vslot = q->V >> QFQ_MIN_SLOT_SHIFT;
+        unsigned long old_vslot = old_V >> QFQ_MIN_SLOT_SHIFT;
+
+        if (vslot != old_vslot) {
+                unsigned long mask = (1UL << fls(vslot ^ old_vslot)) - 1;
+                qfq_move_groups(q, mask, IR, ER);
+                qfq_move_groups(q, mask, IB, EB);
+        }
+}
+
+
+/*
+ * XXX we should make sure that slot becomes less than 32.
+ * This is guaranteed by the input values.
+ * roundedS is always cl->S rounded on grp->slot_shift bits.
+ */
+static void qfq_slot_insert(struct qfq_group *grp, struct qfq_class *cl,
+                            u64 roundedS)
+{
+        u64 slot = (roundedS - grp->S) >> grp->slot_shift;
+        unsigned int i = (grp->front + slot) % QFQ_MAX_SLOTS;
+
+        hlist_add_head(&cl->next, &grp->slots[i]);
+        __set_bit(slot, &grp->full_slots);
+}
+
+/* Maybe introduce hlist_first_entry?? */
+static struct qfq_class *qfq_slot_head(struct qfq_group *grp)
+{
+        return hlist_entry(grp->slots[grp->front].first,
+                           struct qfq_class, next);
+}
+
+/*
+ * remove the entry from the slot
+ */
+static void qfq_front_slot_remove(struct qfq_group *grp)
+{
+        struct qfq_class *cl = qfq_slot_head(grp);
+
+        BUG_ON(!cl);
+        hlist_del(&cl->next);
+        if (hlist_empty(&grp->slots[grp->front]))
+                __clear_bit(0, &grp->full_slots);
+}
+
+/*
+ * Returns the first full queue in a group. As a side effect,
+ * adjust the bucket list so the first non-empty bucket is at
+ * position 0 in full_slots.
+ */
+static struct qfq_class *qfq_slot_scan(struct qfq_group *grp)
+{
+        unsigned int i;
+
+        pr_debug("qfq slot_scan: grp %u full %#lx\n",
+                 grp->index, grp->full_slots);
+
+        if (grp->full_slots == 0)
+                return NULL;
+
+        i = __ffs(grp->full_slots);  /* zero based */
+        if (i > 0) {
+                grp->front = (grp->front + i) % QFQ_MAX_SLOTS;
+                grp->full_slots >>= i;
+        }
+
+        return qfq_slot_head(grp);
+}
+
+/*
+ * adjust the bucket list. When the start time of a group decreases,
+ * we move the index down (modulo QFQ_MAX_SLOTS) so we don't need to
+ * move the objects. The mask of occupied slots must be shifted
+ * because we use ffs() to find the first non-empty slot.
+ * This covers decreases in the group's start time, but what about
+ * increases of the start time ?
+ * Here too we should make sure that i is less than 32
+ */
+static void qfq_slot_rotate(struct qfq_group *grp, u64 roundedS)
+{
+        unsigned int i = (grp->S - roundedS) >> grp->slot_shift;
+
+        grp->full_slots <<= i;
+        grp->front = (grp->front - i) % QFQ_MAX_SLOTS;
+}
+
+static void qfq_update_eligible(struct qfq_sched *q, u64 old_V)
+{
+        struct qfq_group *grp;
+        unsigned long ineligible;
+
+        ineligible = q->bitmaps[IR] | q->bitmaps[IB];
+        if (ineligible) {
+                if (!q->bitmaps[ER]) {
+                        grp = qfq_ffs(q, ineligible);
+                        if (qfq_gt(grp->S, q->V))
+                                q->V = grp->S;
+                }
+                qfq_make_eligible(q, old_V);
+        }
+}
+
+/* What is length of next packet in queue (0 if queue is empty) */
+static unsigned int qdisc_peek_len(struct Qdisc *sch)
+{
+        struct sk_buff *skb;
+
+        skb = sch->ops->peek(sch);
+        return skb ? qdisc_pkt_len(skb) : 0;
+}
+
+/*
+ * Updates the class, returns true if also the group needs to be updated.
+ */
+static bool qfq_update_class(struct qfq_group *grp, struct qfq_class *cl)
+{
+        unsigned int len = qdisc_peek_len(cl->qdisc);
+
+        cl->S = cl->F;
+        if (!len)
+                qfq_front_slot_remove(grp);     /* queue is empty */
+        else {
+                u64 roundedS;
+
+                cl->F = cl->S + (u64)len * cl->inv_w;
+                roundedS = qfq_round_down(cl->S, grp->slot_shift);
+                if (roundedS == grp->S)
+                        return false;
+
+                qfq_front_slot_remove(grp);
+                qfq_slot_insert(grp, cl, roundedS);
+        }
+
+        return true;
+}
+
+static struct sk_buff *qfq_dequeue(struct Qdisc *sch)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_group *grp;
+        struct qfq_class *cl;
+        struct sk_buff *skb;
+        unsigned int len;
+        u64 old_V;
+
+        if (!q->bitmaps[ER])
+                return NULL;
+
+        grp = qfq_ffs(q, q->bitmaps[ER]);
+
+        cl = qfq_slot_head(grp);
+        skb = qdisc_dequeue_peeked(cl->qdisc);
+        if (!skb) {
+                WARN_ONCE(1, "qfq_dequeue: non-workconserving leaf\n");
+                return NULL;
+        }
+
+        sch->q.qlen--;
+        qdisc_bstats_update(sch, skb);
+
+        old_V = q->V;
+        len = qdisc_pkt_len(skb);
+        q->V += (u64)len * IWSUM;
+        pr_debug("qfq dequeue: len %u F %lld now %lld\n",
+                 len, (unsigned long long) cl->F, (unsigned long long) q->V);
+
+        if (qfq_update_class(grp, cl)) {
+                u64 old_F = grp->F;
+
+                cl = qfq_slot_scan(grp);
+                if (!cl)
+                        __clear_bit(grp->index, &q->bitmaps[ER]);
+                else {
+                        u64 roundedS = qfq_round_down(cl->S, grp->slot_shift);
+                        unsigned int s;
+
+                        if (grp->S == roundedS)
+                                goto skip_unblock;
+                        grp->S = roundedS;
+                        grp->F = roundedS + (2ULL << grp->slot_shift);
+                        __clear_bit(grp->index, &q->bitmaps[ER]);
+                        s = qfq_calc_state(q, grp);
+                        __set_bit(grp->index, &q->bitmaps[s]);
+                }
+
+                qfq_unblock_groups(q, grp->index, old_F);
+        }
+
+skip_unblock:
+        qfq_update_eligible(q, old_V);
+
+        return skb;
+}
+
+/*
+ * Assign a reasonable start time for a new flow k in group i.
+ * Admissible values for \hat(F) are multiples of \sigma_i
+ * no greater than V+\sigma_i . Larger values mean that
+ * we had a wraparound so we consider the timestamp to be stale.
+ *
+ * If F is not stale and F >= V then we set S = F.
+ * Otherwise we should assign S = V, but this may violate
+ * the ordering in ER. So, if we have groups in ER, set S to
+ * the F_j of the first group j which would be blocking us.
+ * We are guaranteed not to move S backward because
+ * otherwise our group i would still be blocked.
+ */
+static void qfq_update_start(struct qfq_sched *q, struct qfq_class *cl)
+{
+        unsigned long mask;
+        uint32_t limit, roundedF;
+        int slot_shift = cl->grp->slot_shift;
+
+        roundedF = qfq_round_down(cl->F, slot_shift);
+        limit = qfq_round_down(q->V, slot_shift) + (1UL << slot_shift);
+
+        if (!qfq_gt(cl->F, q->V) || qfq_gt(roundedF, limit)) {
+                /* timestamp was stale */
+                mask = mask_from(q->bitmaps[ER], cl->grp->index);
+                if (mask) {
+                        struct qfq_group *next = qfq_ffs(q, mask);
+                        if (qfq_gt(roundedF, next->F)) {
+                                cl->S = next->F;
+                                return;
+                        }
+                }
+                cl->S = q->V;
+        } else  /* timestamp is not stale */
+                cl->S = cl->F;
+}
+
+static int qfq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_group *grp;
+        struct qfq_class *cl;
+        int err;
+        u64 roundedS;
+        int s;
+
+        cl = qfq_classify(skb, sch, &err);
+        if (cl == NULL) {
+                if (err & __NET_XMIT_BYPASS)
+                        sch->qstats.drops++;
+                kfree_skb(skb);
+                return err;
+        }
+        pr_debug("qfq_enqueue: cl = %x\n", cl->common.classid);
+
+        err = qdisc_enqueue(skb, cl->qdisc);
+        if (unlikely(err != NET_XMIT_SUCCESS)) {
+                pr_debug("qfq_enqueue: enqueue failed %d\n", err);
+                if (net_xmit_drop_count(err)) {
+                        cl->qstats.drops++;
+                        sch->qstats.drops++;
+                }
+                return err;
+        }
+
+        bstats_update(&cl->bstats, skb);
+        ++sch->q.qlen;
+
+        /* If the new skb is not the head of queue, then done here. */
+        if (cl->qdisc->q.qlen != 1)
+                return err;
+
+        /* If reach this point, queue q was idle */
+        grp = cl->grp;
+        qfq_update_start(q, cl);
+
+        /* compute new finish time and rounded start. */
+        cl->F = cl->S + (u64)qdisc_pkt_len(skb) * cl->inv_w;
+        roundedS = qfq_round_down(cl->S, grp->slot_shift);
+
+        /*
+         * insert cl in the correct bucket.
+         * If cl->S >= grp->S we don't need to adjust the
+         * bucket list and simply go to the insertion phase.
+         * Otherwise grp->S is decreasing, we must make room
+         * in the bucket list, and also recompute the group state.
+         * Finally, if there were no flows in this group and nobody
+         * was in ER make sure to adjust V.
+         */
+        if (grp->full_slots) {
+                if (!qfq_gt(grp->S, cl->S))
+                        goto skip_update;
+
+                /* create a slot for this cl->S */
+                qfq_slot_rotate(grp, roundedS);
+                /* group was surely ineligible, remove */
+                __clear_bit(grp->index, &q->bitmaps[IR]);
+                __clear_bit(grp->index, &q->bitmaps[IB]);
+        } else if (!q->bitmaps[ER] && qfq_gt(roundedS, q->V))
+                q->V = roundedS;
+
+        grp->S = roundedS;
+        grp->F = roundedS + (2ULL << grp->slot_shift);
+        s = qfq_calc_state(q, grp);
+        __set_bit(grp->index, &q->bitmaps[s]);
+
+        pr_debug("qfq enqueue: new state %d %#lx S %lld F %lld V %lld\n",
+                 s, q->bitmaps[s],
+                 (unsigned long long) cl->S,
+                 (unsigned long long) cl->F,
+                 (unsigned long long) q->V);
+
+skip_update:
+        qfq_slot_insert(grp, cl, roundedS);
+
+        return err;
+}
+
+
+static void qfq_slot_remove(struct qfq_sched *q, struct qfq_group *grp,
+                            struct qfq_class *cl)
+{
+        unsigned int i, offset;
+        u64 roundedS;
+
+        roundedS = qfq_round_down(cl->S, grp->slot_shift);
+        offset = (roundedS - grp->S) >> grp->slot_shift;
+        i = (grp->front + offset) % QFQ_MAX_SLOTS;
+
+        hlist_del(&cl->next);
+        if (hlist_empty(&grp->slots[i]))
+                __clear_bit(offset, &grp->full_slots);
+}
+
+/*
+ * called to forcibly destroy a queue.
+ * If the queue is not in the front bucket, or if it has
+ * other queues in the front bucket, we can simply remove
+ * the queue with no other side effects.
+ * Otherwise we must propagate the event up.
+ */
+static void qfq_deactivate_class(struct qfq_sched *q, struct qfq_class *cl)
+{
+        struct qfq_group *grp = cl->grp;
+        unsigned long mask;
+        u64 roundedS;
+        int s;
+
+        cl->F = cl->S;
+        qfq_slot_remove(q, grp, cl);
+
+        if (!grp->full_slots) {
+                __clear_bit(grp->index, &q->bitmaps[IR]);
+                __clear_bit(grp->index, &q->bitmaps[EB]);
+                __clear_bit(grp->index, &q->bitmaps[IB]);
+
+                if (test_bit(grp->index, &q->bitmaps[ER]) &&
+                    !(q->bitmaps[ER] & ~((1UL << grp->index) - 1))) {
+                        mask = q->bitmaps[ER] & ((1UL << grp->index) - 1);
+                        if (mask)
+                                mask = ~((1UL << __fls(mask)) - 1);
+                        else
+                                mask = ~0UL;
+                        qfq_move_groups(q, mask, EB, ER);
+                        qfq_move_groups(q, mask, IB, IR);
+                }
+                __clear_bit(grp->index, &q->bitmaps[ER]);
+        } else if (hlist_empty(&grp->slots[grp->front])) {
+                cl = qfq_slot_scan(grp);
+                roundedS = qfq_round_down(cl->S, grp->slot_shift);
+                if (grp->S != roundedS) {
+                        __clear_bit(grp->index, &q->bitmaps[ER]);
+                        __clear_bit(grp->index, &q->bitmaps[IR]);
+                        __clear_bit(grp->index, &q->bitmaps[EB]);
+                        __clear_bit(grp->index, &q->bitmaps[IB]);
+                        grp->S = roundedS;
+                        grp->F = roundedS + (2ULL << grp->slot_shift);
+                        s = qfq_calc_state(q, grp);
+                        __set_bit(grp->index, &q->bitmaps[s]);
+                }
+        }
+
+        qfq_update_eligible(q, q->V);
+}
+
+static void qfq_qlen_notify(struct Qdisc *sch, unsigned long arg)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_class *cl = (struct qfq_class *)arg;
+
+        if (cl->qdisc->q.qlen == 0)
+                qfq_deactivate_class(q, cl);
+}
+
+static unsigned int qfq_drop(struct Qdisc *sch)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_group *grp;
+        unsigned int i, j, len;
+
+        for (i = 0; i <= QFQ_MAX_INDEX; i++) {
+                grp = &q->groups[i];
+                for (j = 0; j < QFQ_MAX_SLOTS; j++) {
+                        struct qfq_class *cl;
+                        struct hlist_node *n;
+
+                        hlist_for_each_entry(cl, n, &grp->slots[j], next) {
+
+                                if (!cl->qdisc->ops->drop)
+                                        continue;
+
+                                len = cl->qdisc->ops->drop(cl->qdisc);
+                                if (len > 0) {
+                                        sch->q.qlen--;
+                                        if (!cl->qdisc->q.qlen)
+                                                qfq_deactivate_class(q, cl);
+
+                                        return len;
+                                }
+                        }
+                }
+        }
+
+        return 0;
+}
+
+static int qfq_init_qdisc(struct Qdisc *sch, struct nlattr *opt)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_group *grp;
+        int i, j, err;
+
+        err = qdisc_class_hash_init(&q->clhash);
+        if (err < 0)
+                return err;
+
+        for (i = 0; i <= QFQ_MAX_INDEX; i++) {
+                grp = &q->groups[i];
+                grp->index = i;
+                grp->slot_shift = QFQ_MTU_SHIFT + FRAC_BITS
+                                   - (QFQ_MAX_INDEX - i);
+                for (j = 0; j < QFQ_MAX_SLOTS; j++)
+                        INIT_HLIST_HEAD(&grp->slots[j]);
+        }
+
+        return 0;
+}
+
+static void qfq_reset_qdisc(struct Qdisc *sch)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_group *grp;
+        struct qfq_class *cl;
+        struct hlist_node *n, *tmp;
+        unsigned int i, j;
+
+        for (i = 0; i <= QFQ_MAX_INDEX; i++) {
+                grp = &q->groups[i];
+                for (j = 0; j < QFQ_MAX_SLOTS; j++) {
+                        hlist_for_each_entry_safe(cl, n, tmp,
+                                                  &grp->slots[j], next) {
+                                qfq_deactivate_class(q, cl);
+                        }
+                }
+        }
+
+        for (i = 0; i < q->clhash.hashsize; i++) {
+                hlist_for_each_entry(cl, n, &q->clhash.hash[i], common.hnode)
+                        qdisc_reset(cl->qdisc);
+        }
+        sch->q.qlen = 0;
+}
+
+static void qfq_destroy_qdisc(struct Qdisc *sch)
+{
+        struct qfq_sched *q = qdisc_priv(sch);
+        struct qfq_class *cl;
+        struct hlist_node *n, *next;
+        unsigned int i;
+
+        tcf_destroy_chain(&q->filter_list);
+
+        for (i = 0; i < q->clhash.hashsize; i++) {
+                hlist_for_each_entry_safe(cl, n, next, &q->clhash.hash[i],
+                                          common.hnode) {
+                        qfq_destroy_class(sch, cl);
+                }
+        }
+        qdisc_class_hash_destroy(&q->clhash);
+}
+
+static const struct Qdisc_class_ops qfq_class_ops = {
+        .change         = qfq_change_class,
+        .delete         = qfq_delete_class,
+        .get            = qfq_get_class,
+        .put            = qfq_put_class,
+        .tcf_chain      = qfq_tcf_chain,
+        .bind_tcf       = qfq_bind_tcf,
+        .unbind_tcf     = qfq_unbind_tcf,
+        .graft          = qfq_graft_class,
+        .leaf           = qfq_class_leaf,
+        .qlen_notify    = qfq_qlen_notify,
+        .dump           = qfq_dump_class,
+        .dump_stats     = qfq_dump_class_stats,
+        .walk           = qfq_walk,
+};
+
+static struct Qdisc_ops qfq_qdisc_ops __read_mostly = {
+        .cl_ops         = &qfq_class_ops,
+        .id             = "qfq",
+        .priv_size      = sizeof(struct qfq_sched),
+        .enqueue        = qfq_enqueue,
+        .dequeue        = qfq_dequeue,
+        .peek           = qdisc_peek_dequeued,
+        .drop           = qfq_drop,
+        .init           = qfq_init_qdisc,
+        .reset          = qfq_reset_qdisc,
+        .destroy        = qfq_destroy_qdisc,
+        .owner          = THIS_MODULE,
+};
+
+static int __init qfq_init(void)
+{
+        return register_qdisc(&qfq_qdisc_ops);
+}
+
+static void __exit qfq_exit(void)
+{
+        unregister_qdisc(&qfq_qdisc_ops);
+}
+
+module_init(qfq_init);
+module_exit(qfq_exit);
+MODULE_LICENSE("GPL");