* [PATCH net v5 1/2] net/sched: Fix backlog accounting in qdisc_dequeue_internal
@ 2025-08-12 23:57 William Liu
2025-08-12 23:58 ` [PATCH net v5 2/2] selftests/tc-testing: Check backlog stats in gso_skb case William Liu
2025-08-15 1:30 ` [PATCH net v5 1/2] net/sched: Fix backlog accounting in qdisc_dequeue_internal patchwork-bot+netdevbpf
0 siblings, 2 replies; 3+ messages in thread
From: William Liu @ 2025-08-12 23:57 UTC (permalink / raw)
To: netdev
Cc: jhs, xiyou.wangcong, pabeni, kuba, jiri, davem, edumazet, horms,
savy, victor, William Liu
This issue applies for the following qdiscs: hhf, fq, fq_codel, and
fq_pie, and occurs in their change handlers when adjusting to the new
limit. The problem is the following in the values passed to the
subsequent qdisc_tree_reduce_backlog call given a tbf parent:
When the tbf parent runs out of tokens, skbs of these qdiscs will
be placed in gso_skb. Their peek handlers are qdisc_peek_dequeued,
which accounts for both qlen and backlog. However, in the case of
qdisc_dequeue_internal, ONLY qlen is accounted for when pulling
from gso_skb. This means that these qdiscs are missing a
qdisc_qstats_backlog_dec when dropping packets to satisfy the
new limit in their change handlers.
One can observe this issue with the following (with tc patched to
support a limit of 0):
export TARGET=fq
tc qdisc del dev lo root
tc qdisc add dev lo root handle 1: tbf rate 8bit burst 100b latency 1ms
tc qdisc replace dev lo handle 3: parent 1:1 $TARGET limit 1000
echo ''; echo 'add child'; tc -s -d qdisc show dev lo
ping -I lo -f -c2 -s32 -W0.001 127.0.0.1 2>&1 >/dev/null
echo ''; echo 'after ping'; tc -s -d qdisc show dev lo
tc qdisc change dev lo handle 3: parent 1:1 $TARGET limit 0
echo ''; echo 'after limit drop'; tc -s -d qdisc show dev lo
tc qdisc replace dev lo handle 2: parent 1:1 sfq
echo ''; echo 'post graft'; tc -s -d qdisc show dev lo
The second to last show command shows 0 packets but a positive
number (74) of backlog bytes. The problem becomes clearer in the
last show command, where qdisc_purge_queue triggers
qdisc_tree_reduce_backlog with the positive backlog and causes an
underflow in the tbf parent's backlog (4096 Mb instead of 0).
To fix this issue, the codepath for all clients of qdisc_dequeue_internal
has been simplified: codel, pie, hhf, fq, fq_pie, and fq_codel.
qdisc_dequeue_internal handles the backlog adjustments for all cases that
do not directly use the dequeue handler.
The old fq_codel_change limit adjustment loop accumulated the arguments to
the subsequent qdisc_tree_reduce_backlog call through the cstats field.
However, this is confusing and error prone as fq_codel_dequeue could also
potentially mutate this field (which qdisc_dequeue_internal calls in the
non gso_skb case), so we have unified the code here with other qdiscs.
Fixes: 2d3cbfd6d54a ("net_sched: Flush gso_skb list too during ->change()")
Fixes: 4b549a2ef4be ("fq_codel: Fair Queue Codel AQM")
Fixes: 10239edf86f1 ("net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc")
Signed-off-by: William Liu <will@willsroot.io>
Reviewed-by: Savino Dicanosa <savy@syst3mfailure.io>
---
v4 -> v5:
- address formatting nit, update commit message with additional
clarifications, unify limit adjustment loops to suggested
style from Jakub
v1 -> v2:
- Fix commit formatting
- There was a suggestion to split the patch apart into one for each
qdisc - however, individual qdisc behavior will be further broken
by this split due to the reliance on qdisc_dequeue_internal
---
include/net/sch_generic.h | 11 ++++++++---
net/sched/sch_codel.c | 12 +++++++-----
net/sched/sch_fq.c | 12 +++++++-----
net/sched/sch_fq_codel.c | 12 +++++++-----
net/sched/sch_fq_pie.c | 12 +++++++-----
net/sched/sch_hhf.c | 12 +++++++-----
net/sched/sch_pie.c | 12 +++++++-----
7 files changed, 50 insertions(+), 33 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 638948be4c50..738cd5b13c62 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -1038,12 +1038,17 @@ static inline struct sk_buff *qdisc_dequeue_internal(struct Qdisc *sch, bool dir
skb = __skb_dequeue(&sch->gso_skb);
if (skb) {
sch->q.qlen--;
+ qdisc_qstats_backlog_dec(sch, skb);
return skb;
}
- if (direct)
- return __qdisc_dequeue_head(&sch->q);
- else
+ if (direct) {
+ skb = __qdisc_dequeue_head(&sch->q);
+ if (skb)
+ qdisc_qstats_backlog_dec(sch, skb);
+ return skb;
+ } else {
return sch->dequeue(sch);
+ }
}
static inline struct sk_buff *qdisc_dequeue_head(struct Qdisc *sch)
diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
index c93761040c6e..fa0314679e43 100644
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -101,9 +101,9 @@ static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = {
static int codel_change(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
+ unsigned int dropped_pkts = 0, dropped_bytes = 0;
struct codel_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_CODEL_MAX + 1];
- unsigned int qlen, dropped = 0;
int err;
err = nla_parse_nested_deprecated(tb, TCA_CODEL_MAX, opt,
@@ -142,15 +142,17 @@ static int codel_change(struct Qdisc *sch, struct nlattr *opt,
WRITE_ONCE(q->params.ecn,
!!nla_get_u32(tb[TCA_CODEL_ECN]));
- qlen = sch->q.qlen;
while (sch->q.qlen > sch->limit) {
struct sk_buff *skb = qdisc_dequeue_internal(sch, true);
- dropped += qdisc_pkt_len(skb);
- qdisc_qstats_backlog_dec(sch, skb);
+ if (!skb)
+ break;
+
+ dropped_pkts++;
+ dropped_bytes += qdisc_pkt_len(skb);
rtnl_qdisc_drop(skb, sch);
}
- qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen, dropped);
+ qdisc_tree_reduce_backlog(sch, dropped_pkts, dropped_bytes);
sch_tree_unlock(sch);
return 0;
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index 902ff5470607..fee922da2f99 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -1013,11 +1013,11 @@ static int fq_load_priomap(struct fq_sched_data *q,
static int fq_change(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
+ unsigned int dropped_pkts = 0, dropped_bytes = 0;
struct fq_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_FQ_MAX + 1];
- int err, drop_count = 0;
- unsigned drop_len = 0;
u32 fq_log;
+ int err;
err = nla_parse_nested_deprecated(tb, TCA_FQ_MAX, opt, fq_policy,
NULL);
@@ -1135,16 +1135,18 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt,
err = fq_resize(sch, fq_log);
sch_tree_lock(sch);
}
+
while (sch->q.qlen > sch->limit) {
struct sk_buff *skb = qdisc_dequeue_internal(sch, false);
if (!skb)
break;
- drop_len += qdisc_pkt_len(skb);
+
+ dropped_pkts++;
+ dropped_bytes += qdisc_pkt_len(skb);
rtnl_kfree_skbs(skb, skb);
- drop_count++;
}
- qdisc_tree_reduce_backlog(sch, drop_count, drop_len);
+ qdisc_tree_reduce_backlog(sch, dropped_pkts, dropped_bytes);
sch_tree_unlock(sch);
return err;
diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index 2a0f3a513bfa..a14142392939 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -366,6 +366,7 @@ static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = {
static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
+ unsigned int dropped_pkts = 0, dropped_bytes = 0;
struct fq_codel_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_FQ_CODEL_MAX + 1];
u32 quantum = 0;
@@ -443,13 +444,14 @@ static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt,
q->memory_usage > q->memory_limit) {
struct sk_buff *skb = qdisc_dequeue_internal(sch, false);
- q->cstats.drop_len += qdisc_pkt_len(skb);
+ if (!skb)
+ break;
+
+ dropped_pkts++;
+ dropped_bytes += qdisc_pkt_len(skb);
rtnl_kfree_skbs(skb, skb);
- q->cstats.drop_count++;
}
- qdisc_tree_reduce_backlog(sch, q->cstats.drop_count, q->cstats.drop_len);
- q->cstats.drop_count = 0;
- q->cstats.drop_len = 0;
+ qdisc_tree_reduce_backlog(sch, dropped_pkts, dropped_bytes);
sch_tree_unlock(sch);
return 0;
diff --git a/net/sched/sch_fq_pie.c b/net/sched/sch_fq_pie.c
index b0e34daf1f75..7b96bc3ff891 100644
--- a/net/sched/sch_fq_pie.c
+++ b/net/sched/sch_fq_pie.c
@@ -287,10 +287,9 @@ static struct sk_buff *fq_pie_qdisc_dequeue(struct Qdisc *sch)
static int fq_pie_change(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
+ unsigned int dropped_pkts = 0, dropped_bytes = 0;
struct fq_pie_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_FQ_PIE_MAX + 1];
- unsigned int len_dropped = 0;
- unsigned int num_dropped = 0;
int err;
err = nla_parse_nested(tb, TCA_FQ_PIE_MAX, opt, fq_pie_policy, extack);
@@ -368,11 +367,14 @@ static int fq_pie_change(struct Qdisc *sch, struct nlattr *opt,
while (sch->q.qlen > sch->limit) {
struct sk_buff *skb = qdisc_dequeue_internal(sch, false);
- len_dropped += qdisc_pkt_len(skb);
- num_dropped += 1;
+ if (!skb)
+ break;
+
+ dropped_pkts++;
+ dropped_bytes += qdisc_pkt_len(skb);
rtnl_kfree_skbs(skb, skb);
}
- qdisc_tree_reduce_backlog(sch, num_dropped, len_dropped);
+ qdisc_tree_reduce_backlog(sch, dropped_pkts, dropped_bytes);
sch_tree_unlock(sch);
return 0;
diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c
index 5aa434b46707..2d4855e28a28 100644
--- a/net/sched/sch_hhf.c
+++ b/net/sched/sch_hhf.c
@@ -508,9 +508,9 @@ static const struct nla_policy hhf_policy[TCA_HHF_MAX + 1] = {
static int hhf_change(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
+ unsigned int dropped_pkts = 0, dropped_bytes = 0;
struct hhf_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_HHF_MAX + 1];
- unsigned int qlen, prev_backlog;
int err;
u64 non_hh_quantum;
u32 new_quantum = q->quantum;
@@ -561,15 +561,17 @@ static int hhf_change(struct Qdisc *sch, struct nlattr *opt,
usecs_to_jiffies(us));
}
- qlen = sch->q.qlen;
- prev_backlog = sch->qstats.backlog;
while (sch->q.qlen > sch->limit) {
struct sk_buff *skb = qdisc_dequeue_internal(sch, false);
+ if (!skb)
+ break;
+
+ dropped_pkts++;
+ dropped_bytes += qdisc_pkt_len(skb);
rtnl_kfree_skbs(skb, skb);
}
- qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen,
- prev_backlog - sch->qstats.backlog);
+ qdisc_tree_reduce_backlog(sch, dropped_pkts, dropped_bytes);
sch_tree_unlock(sch);
return 0;
diff --git a/net/sched/sch_pie.c b/net/sched/sch_pie.c
index ad46ee3ed5a9..0a377313b6a9 100644
--- a/net/sched/sch_pie.c
+++ b/net/sched/sch_pie.c
@@ -141,9 +141,9 @@ static const struct nla_policy pie_policy[TCA_PIE_MAX + 1] = {
static int pie_change(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
+ unsigned int dropped_pkts = 0, dropped_bytes = 0;
struct pie_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_PIE_MAX + 1];
- unsigned int qlen, dropped = 0;
int err;
err = nla_parse_nested_deprecated(tb, TCA_PIE_MAX, opt, pie_policy,
@@ -193,15 +193,17 @@ static int pie_change(struct Qdisc *sch, struct nlattr *opt,
nla_get_u32(tb[TCA_PIE_DQ_RATE_ESTIMATOR]));
/* Drop excess packets if new limit is lower */
- qlen = sch->q.qlen;
while (sch->q.qlen > sch->limit) {
struct sk_buff *skb = qdisc_dequeue_internal(sch, true);
- dropped += qdisc_pkt_len(skb);
- qdisc_qstats_backlog_dec(sch, skb);
+ if (!skb)
+ break;
+
+ dropped_pkts++;
+ dropped_bytes += qdisc_pkt_len(skb);
rtnl_qdisc_drop(skb, sch);
}
- qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen, dropped);
+ qdisc_tree_reduce_backlog(sch, dropped_pkts, dropped_bytes);
sch_tree_unlock(sch);
return 0;
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH net v5 2/2] selftests/tc-testing: Check backlog stats in gso_skb case
2025-08-12 23:57 [PATCH net v5 1/2] net/sched: Fix backlog accounting in qdisc_dequeue_internal William Liu
@ 2025-08-12 23:58 ` William Liu
2025-08-15 1:30 ` [PATCH net v5 1/2] net/sched: Fix backlog accounting in qdisc_dequeue_internal patchwork-bot+netdevbpf
1 sibling, 0 replies; 3+ messages in thread
From: William Liu @ 2025-08-12 23:58 UTC (permalink / raw)
To: netdev
Cc: jhs, xiyou.wangcong, pabeni, kuba, jiri, davem, edumazet, horms,
savy, victor, William Liu
Add tests to ensure proper backlog accounting in hhf, codel, pie, fq,
fq_pie, and fq_codel qdiscs. We check for the bug pattern originally
found in fq, fq_pie, and fq_codel, which was an underflow in the tbf
parent backlog stats upon child qdisc removal.
Signed-off-by: William Liu <will@willsroot.io>
Reviewed-by: Savino Dicanosa <savy@syst3mfailure.io>
---
v3 -> v4:
- Unify tests to check against underflow in tbf stats on purge
v2 -> v3:
- Simplify ping command in test cases
- Remove scapyPlugin dependency
---
.../tc-testing/tc-tests/infra/qdiscs.json | 198 ++++++++++++++++++
1 file changed, 198 insertions(+)
diff --git a/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json b/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json
index 23a61e5b99d0..998e5a2f4579 100644
--- a/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json
+++ b/tools/testing/selftests/tc-testing/tc-tests/infra/qdiscs.json
@@ -185,6 +185,204 @@
"$IP addr del 10.10.10.10/24 dev $DUMMY || true"
]
},
+ {
+ "id": "34c0",
+ "name": "Test TBF with HHF Backlog Accounting in gso_skb case against underflow",
+ "category": [
+ "qdisc",
+ "tbf",
+ "hhf"
+ ],
+ "plugins": {
+ "requires": [
+ "nsPlugin"
+ ]
+ },
+ "setup": [
+ "$IP link set dev $DUMMY up || true",
+ "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+ "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+ "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 hhf limit 1000",
+ [
+ "ping -I $DUMMY -c2 10.10.11.11",
+ 1
+ ],
+ "$TC qdisc change dev $DUMMY handle 2: parent 1:1 hhf limit 1"
+ ],
+ "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+ "expExitCode": "0",
+ "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+ "matchPattern": "backlog 0b 0p",
+ "matchCount": "1",
+ "teardown": [
+ "$TC qdisc del dev $DUMMY handle 1: root"
+ ]
+ },
+ {
+ "id": "fd68",
+ "name": "Test TBF with CODEL Backlog Accounting in gso_skb case against underflow",
+ "category": [
+ "qdisc",
+ "tbf",
+ "codel"
+ ],
+ "plugins": {
+ "requires": [
+ "nsPlugin"
+ ]
+ },
+ "setup": [
+ "$IP link set dev $DUMMY up || true",
+ "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+ "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+ "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 codel limit 1000",
+ [
+ "ping -I $DUMMY -c2 10.10.11.11",
+ 1
+ ],
+ "$TC qdisc change dev $DUMMY handle 2: parent 1:1 codel limit 1"
+ ],
+ "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+ "expExitCode": "0",
+ "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+ "matchPattern": "backlog 0b 0p",
+ "matchCount": "1",
+ "teardown": [
+ "$TC qdisc del dev $DUMMY handle 1: root"
+ ]
+ },
+ {
+ "id": "514e",
+ "name": "Test TBF with PIE Backlog Accounting in gso_skb case against underflow",
+ "category": [
+ "qdisc",
+ "tbf",
+ "pie"
+ ],
+ "plugins": {
+ "requires": [
+ "nsPlugin"
+ ]
+ },
+ "setup": [
+ "$IP link set dev $DUMMY up || true",
+ "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+ "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+ "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 pie limit 1000",
+ [
+ "ping -I $DUMMY -c2 10.10.11.11",
+ 1
+ ],
+ "$TC qdisc change dev $DUMMY handle 2: parent 1:1 pie limit 1"
+ ],
+ "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+ "expExitCode": "0",
+ "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+ "matchPattern": "backlog 0b 0p",
+ "matchCount": "1",
+ "teardown": [
+ "$TC qdisc del dev $DUMMY handle 1: root"
+ ]
+ },
+ {
+ "id": "6c97",
+ "name": "Test TBF with FQ Backlog Accounting in gso_skb case against underflow",
+ "category": [
+ "qdisc",
+ "tbf",
+ "fq"
+ ],
+ "plugins": {
+ "requires": [
+ "nsPlugin"
+ ]
+ },
+ "setup": [
+ "$IP link set dev $DUMMY up || true",
+ "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+ "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+ "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 fq limit 1000",
+ [
+ "ping -I $DUMMY -c2 10.10.11.11",
+ 1
+ ],
+ "$TC qdisc change dev $DUMMY handle 2: parent 1:1 fq limit 1"
+ ],
+ "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+ "expExitCode": "0",
+ "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+ "matchPattern": "backlog 0b 0p",
+ "matchCount": "1",
+ "teardown": [
+ "$TC qdisc del dev $DUMMY handle 1: root"
+ ]
+ },
+ {
+ "id": "5d0b",
+ "name": "Test TBF with FQ_CODEL Backlog Accounting in gso_skb case against underflow",
+ "category": [
+ "qdisc",
+ "tbf",
+ "fq_codel"
+ ],
+ "plugins": {
+ "requires": [
+ "nsPlugin"
+ ]
+ },
+ "setup": [
+ "$IP link set dev $DUMMY up || true",
+ "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+ "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+ "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 fq_codel limit 1000",
+ [
+ "ping -I $DUMMY -c2 10.10.11.11",
+ 1
+ ],
+ "$TC qdisc change dev $DUMMY handle 2: parent 1:1 fq_codel limit 1"
+ ],
+ "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+ "expExitCode": "0",
+ "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+ "matchPattern": "backlog 0b 0p",
+ "matchCount": "1",
+ "teardown": [
+ "$TC qdisc del dev $DUMMY handle 1: root"
+ ]
+ },
+ {
+ "id": "21c3",
+ "name": "Test TBF with FQ_PIE Backlog Accounting in gso_skb case against underflow",
+ "category": [
+ "qdisc",
+ "tbf",
+ "fq_pie"
+ ],
+ "plugins": {
+ "requires": [
+ "nsPlugin"
+ ]
+ },
+ "setup": [
+ "$IP link set dev $DUMMY up || true",
+ "$IP addr add 10.10.11.10/24 dev $DUMMY || true",
+ "$TC qdisc add dev $DUMMY root handle 1: tbf rate 8bit burst 100b latency 100ms",
+ "$TC qdisc replace dev $DUMMY handle 2: parent 1:1 fq_pie limit 1000",
+ [
+ "ping -I $DUMMY -c2 10.10.11.11",
+ 1
+ ],
+ "$TC qdisc change dev $DUMMY handle 2: parent 1:1 fq_pie limit 1"
+ ],
+ "cmdUnderTest": "$TC qdisc del dev $DUMMY handle 2: parent 1:1",
+ "expExitCode": "0",
+ "verifyCmd": "$TC -s qdisc show dev $DUMMY",
+ "matchPattern": "backlog 0b 0p",
+ "matchCount": "1",
+ "teardown": [
+ "$TC qdisc del dev $DUMMY handle 1: root"
+ ]
+ },
{
"id": "a4bb",
"name": "Test FQ_CODEL with HTB parent - force packet drop with empty queue",
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net v5 1/2] net/sched: Fix backlog accounting in qdisc_dequeue_internal
2025-08-12 23:57 [PATCH net v5 1/2] net/sched: Fix backlog accounting in qdisc_dequeue_internal William Liu
2025-08-12 23:58 ` [PATCH net v5 2/2] selftests/tc-testing: Check backlog stats in gso_skb case William Liu
@ 2025-08-15 1:30 ` patchwork-bot+netdevbpf
1 sibling, 0 replies; 3+ messages in thread
From: patchwork-bot+netdevbpf @ 2025-08-15 1:30 UTC (permalink / raw)
To: William Liu
Cc: netdev, jhs, xiyou.wangcong, pabeni, kuba, jiri, davem, edumazet,
horms, savy, victor
Hello:
This series was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:
On Tue, 12 Aug 2025 23:57:57 +0000 you wrote:
> This issue applies for the following qdiscs: hhf, fq, fq_codel, and
> fq_pie, and occurs in their change handlers when adjusting to the new
> limit. The problem is the following in the values passed to the
> subsequent qdisc_tree_reduce_backlog call given a tbf parent:
>
> When the tbf parent runs out of tokens, skbs of these qdiscs will
> be placed in gso_skb. Their peek handlers are qdisc_peek_dequeued,
> which accounts for both qlen and backlog. However, in the case of
> qdisc_dequeue_internal, ONLY qlen is accounted for when pulling
> from gso_skb. This means that these qdiscs are missing a
> qdisc_qstats_backlog_dec when dropping packets to satisfy the
> new limit in their change handlers.
>
> [...]
Here is the summary with links:
- [net,v5,1/2] net/sched: Fix backlog accounting in qdisc_dequeue_internal
https://git.kernel.org/netdev/net/c/52bf272636bd
- [net,v5,2/2] selftests/tc-testing: Check backlog stats in gso_skb case
https://git.kernel.org/netdev/net/c/8c06cbdcbaea
You are awesome, thank you!
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-- links below jump to the message on this page --
2025-08-12 23:57 [PATCH net v5 1/2] net/sched: Fix backlog accounting in qdisc_dequeue_internal William Liu
2025-08-12 23:58 ` [PATCH net v5 2/2] selftests/tc-testing: Check backlog stats in gso_skb case William Liu
2025-08-15 1:30 ` [PATCH net v5 1/2] net/sched: Fix backlog accounting in qdisc_dequeue_internal patchwork-bot+netdevbpf
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