[PATCH 21/21] net: sched: drop all special handling of tx_queue_len == 0

[Phil Sutter]

Those were all workarounds for the formerly double meaning of
tx_queue_len, which broke scheduling algorithms if untreated.

Now that all in-tree drivers have been converted away from setting
tx_queue_len = 0, it should be safe to drop these workarounds for
categorically broken setups.

Signed-off-by: Phil Sutter <p...@nwl.cc>
Cc: Jamal Hadi Salim <j...@mojatatu.com>
---
 net/sched/sch_fifo.c | 2 +-
 net/sched/sch_gred.c | 8 +++-----
 net/sched/sch_htb.c  | 6 ++----
 net/sched/sch_plug.c | 8 ++------
 net/sched/sch_sfb.c  | 2 +-
 5 files changed, 9 insertions(+), 17 deletions(-)

diff --git a/net/sched/sch_fifo.c b/net/sched/sch_fifo.c
index 2e2398c..2177eac 100644
--- a/net/sched/sch_fifo.c
+++ b/net/sched/sch_fifo.c
@@ -54,7 +54,7 @@ static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
        bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
 
        if (opt == NULL) {
-               u32 limit = qdisc_dev(sch)->tx_queue_len ? : 1;
+               u32 limit = qdisc_dev(sch)->tx_queue_len;
 
                if (is_bfifo)
                        limit *= psched_mtu(qdisc_dev(sch));
diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
index abb9f2f..8010510 100644
--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c
@@ -512,11 +512,9 @@ static int gred_init(struct Qdisc *sch, struct nlattr *opt)
 
        if (tb[TCA_GRED_LIMIT])
                sch->limit = nla_get_u32(tb[TCA_GRED_LIMIT]);
-       else {
-               u32 qlen = qdisc_dev(sch)->tx_queue_len ? : 1;
-
-               sch->limit = qlen * psched_mtu(qdisc_dev(sch));
-       }
+       else
+               sch->limit = qdisc_dev(sch)->tx_queue_len
+                            * psched_mtu(qdisc_dev(sch));
 
        return gred_change_table_def(sch, tb[TCA_GRED_DPS]);
 }
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index f1acb0f..cf4b0f8 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1048,11 +1048,9 @@ static int htb_init(struct Qdisc *sch, struct nlattr 
*opt)
 
        if (tb[TCA_HTB_DIRECT_QLEN])
                q->direct_qlen = nla_get_u32(tb[TCA_HTB_DIRECT_QLEN]);
-       else {
+       else
                q->direct_qlen = qdisc_dev(sch)->tx_queue_len;
-               if (q->direct_qlen < 2) /* some devices have zero tx_queue_len 
*/
-                       q->direct_qlen = 2;
-       }
+
        if ((q->rate2quantum = gopt->rate2quantum) < 1)
                q->rate2quantum = 1;
        q->defcls = gopt->defcls;
diff --git a/net/sched/sch_plug.c b/net/sched/sch_plug.c
index ade9445..5abfe44 100644
--- a/net/sched/sch_plug.c
+++ b/net/sched/sch_plug.c
@@ -130,12 +130,8 @@ static int plug_init(struct Qdisc *sch, struct nlattr *opt)
        q->unplug_indefinite = false;
 
        if (opt == NULL) {
-               /* We will set a default limit of 100 pkts (~150kB)
-                * in case tx_queue_len is not available. The
-                * default value is completely arbitrary.
-                */
-               u32 pkt_limit = qdisc_dev(sch)->tx_queue_len ? : 100;
-               q->limit = pkt_limit * psched_mtu(qdisc_dev(sch));
+               q->limit = qdisc_dev(sch)->tx_queue_len
+                          * psched_mtu(qdisc_dev(sch));
        } else {
                struct tc_plug_qopt *ctl = nla_data(opt);
 
diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c
index 4b81519..dcdff5c 100644
--- a/net/sched/sch_sfb.c
+++ b/net/sched/sch_sfb.c
@@ -502,7 +502,7 @@ static int sfb_change(struct Qdisc *sch, struct nlattr *opt)
 
        limit = ctl->limit;
        if (limit == 0)
-               limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);
+               limit = qdisc_dev(sch)->tx_queue_len;
 
        child = fifo_create_dflt(sch, &pfifo_qdisc_ops, limit);
        if (IS_ERR(child))
-- 
2.1.2

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