[PATCH net] net: sched: shrink struct qdisc_skb_cb to 28 bytes
From: Eric Dumazet <hidden>
Date: 2014-09-18 15:02:08
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
From: Eric Dumazet <edumazet@google.com>
We cannot make struct qdisc_skb_cb bigger without impacting IPoIB,
or increasing skb->cb[] size.
Commit e0f31d849867 ("flow_keys: Record IP layer protocol in
skb_flow_dissect()") broke IPoIB.
Only current offender is sch_choke, and this one do not need an
absolutely precise flow key.
If we store 17 bytes of flow key, its more than enough. (Its the actual
size of flow_keys if it was a packed structure, but we might add new
fields at the end of it later)
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: e0f31d849867 ("flow_keys: Record IP layer protocol in skb_flow_dissect()")
---
include/net/sch_generic.h | 3 ++-
net/sched/sch_choke.c | 18 ++++++++++++++----
2 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index a3cfb8ebeb53..620e086c0cbe 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h@@ -231,7 +231,8 @@ struct qdisc_skb_cb { unsigned int pkt_len; u16 slave_dev_queue_mapping; u16 _pad; - unsigned char data[24]; +#define QDISC_CB_PRIV_LEN 20 + unsigned char data[QDISC_CB_PRIV_LEN]; }; static inline void qdisc_cb_private_validate(const struct sk_buff *skb, int sz)
diff --git a/net/sched/sch_choke.c b/net/sched/sch_choke.c
index ed30e436128b..fb666d1e4de3 100644
--- a/net/sched/sch_choke.c
+++ b/net/sched/sch_choke.c@@ -133,10 +133,16 @@ static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx) --sch->q.qlen; } +/* private part of skb->cb[] that a qdisc is allowed to use + * is limited to QDISC_CB_PRIV_LEN bytes. + * As a flow key might be too large, we store a part of it only. + */ +#define CHOKE_K_LEN min_t(u32, sizeof(struct flow_keys), QDISC_CB_PRIV_LEN - 3) + struct choke_skb_cb { u16 classid; u8 keys_valid; - struct flow_keys keys; + u8 keys[QDISC_CB_PRIV_LEN - 3]; }; static inline struct choke_skb_cb *choke_skb_cb(const struct sk_buff *skb)
@@ -163,22 +169,26 @@ static u16 choke_get_classid(const struct sk_buff *skb) static bool choke_match_flow(struct sk_buff *skb1, struct sk_buff *skb2) { + struct flow_keys temp; + if (skb1->protocol != skb2->protocol) return false; if (!choke_skb_cb(skb1)->keys_valid) { choke_skb_cb(skb1)->keys_valid = 1; - skb_flow_dissect(skb1, &choke_skb_cb(skb1)->keys); + skb_flow_dissect(skb1, &temp); + memcpy(&choke_skb_cb(skb1)->keys, &temp, CHOKE_K_LEN); } if (!choke_skb_cb(skb2)->keys_valid) { choke_skb_cb(skb2)->keys_valid = 1; - skb_flow_dissect(skb2, &choke_skb_cb(skb2)->keys); + skb_flow_dissect(skb2, &temp); + memcpy(&choke_skb_cb(skb2)->keys, &temp, CHOKE_K_LEN); } return !memcmp(&choke_skb_cb(skb1)->keys, &choke_skb_cb(skb2)->keys, - sizeof(struct flow_keys)); + CHOKE_K_LEN); } /*