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net: sched: shrink struct qdisc_skb_cb to 28 bytes 

We cannot make struct qdisc_skb_cb bigger without impacting IPoIB,
or increasing skb->cb[] size.

Commit e0f31d8498 ("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: e0f31d8498 ("flow_keys: Record IP layer protocol in skb_flow_dissect()")
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2014-09-18 08:02:05 -07:00 committed by David S. Miller
parent 476c18850c
commit 2571178626
2 changed files with 16 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/net/sch_generic.h
View File

@ -231,7 +231,8 @@ struct qdisc_skb_cb {
unsigned int pkt_len; unsigned int pkt_len;
u16 slave_dev_queue_mapping; u16 slave_dev_queue_mapping;
u16 _pad; 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) static inline void qdisc_cb_private_validate(const struct sk_buff *skb, int sz)

18
net/sched/sch_choke.c
View File

@ -133,10 +133,16 @@ static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx)
--sch->q.qlen; --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 { struct choke_skb_cb {
u16 classid; u16 classid;
u8 keys_valid; 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) 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, static bool choke_match_flow(struct sk_buff *skb1,
struct sk_buff *skb2) struct sk_buff *skb2)
{ {
struct flow_keys temp;
if (skb1->protocol != skb2->protocol) if (skb1->protocol != skb2->protocol)
return false; return false;
if (!choke_skb_cb(skb1)->keys_valid) { if (!choke_skb_cb(skb1)->keys_valid) {
choke_skb_cb(skb1)->keys_valid = 1; 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) { if (!choke_skb_cb(skb2)->keys_valid) {
choke_skb_cb(skb2)->keys_valid = 1; 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, return !memcmp(&choke_skb_cb(skb1)->keys,
&choke_skb_cb(skb2)->keys, &choke_skb_cb(skb2)->keys,
sizeof(struct flow_keys)); CHOKE_K_LEN);
} }
/* /*