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Date: Tue, 26 Jun 2012 22:07:56 +0200
From: Oliver Hartkopp <socketcan@...tkopp.net>
To: Rostislav Lisovy <lisovy@...il.com>,
Eric Dumazet <eric.dumazet@...il.com>
CC: netdev@...r.kernel.org, linux-can@...r.kernel.org,
lartc@...r.kernel.org, pisa@....felk.cvut.cz, sojkam1@....cvut.cz
Subject: Re: [PATCH net-next] em_canid: Ematch rule to match CAN frames according
to their CAN IDs
Hello Rostislav,
thanks for the new patch. It got indeed pretty short now :-)
I found some time for a review. See details inline ...
On 18.06.2012 14:22, Rostislav Lisovy wrote:
>
> With no extra filter/qdisc configured, median of the time spent in can_send()
> was about 27 us -- with prio qdisc with 5 bands and 5 appropriate cls_can
> filters (previous patch), it was about 30 us -- with prio qdisc with 5 bands
> and 5 appropriate em_can filters (this patch), it was about 34 us.
Hm that's more than twice the time consumed for classification ...
cls_can: 3 us more
em_can: 7 us more
@Eric: Is this still the better approach then?
> diff --git a/net/sched/Kconfig b/net/sched/Kconfig
> index 75b58f8..bc0ceab 100644
> --- a/net/sched/Kconfig
> +++ b/net/sched/Kconfig
> @@ -485,6 +485,16 @@ config NET_EMATCH_TEXT
> To compile this code as a module, choose M here: the
> module will be called em_text.
>
> +config NET_EMATCH_CANID
> + tristate "CAN ID"
i would prefer
tristate "Controller Area Network Identifier"
or at least
tristate "CAN Identifier"
> + depends on NET_EMATCH && CAN
> + ---help---
> + Say Y here if you want to be able to classify CAN frames based
> + on CAN ID.
"on the CAN Identifier."
(..)
> +#include <net/pkt_cls.h>
> +#include <linux/can.h>
> +
> +#define EM_CAN_RULES_SIZE 32
Reduce the gap before '32' to one single space.
(..)
> +static int em_canid_match(struct sk_buff *skb, struct tcf_ematch *m,
> + struct tcf_pkt_info *info)
> +{
> + struct canid_match *cm = em_canid_priv(m);
> + canid_t can_id;
> + unsigned int match = false;
You use test_bit() below which returns an int.
Better use int instead of unsigned int ...
int match = 0;
> + int i;
> +
> + can_id = em_canid_get_id(skb);
> +
> + if (can_id & CAN_EFF_FLAG) {
> + can_id &= CAN_EFF_MASK;
> +
> + for (i = 0; i < cm->eff_rules_count; i++) {
> + if (!(((cm->rules_raw[i].can_id ^ can_id) &
> + cm->rules_raw[i].can_mask) & CAN_EFF_MASK)) {
Looks really tricky. I'm still pondering if it does what it should do ...
> + match = true;
match = 1;
> + break;
> + }
> + }
> + } else { /* SFF */
> + can_id &= CAN_SFF_MASK;
> + match = test_bit(can_id, cm->match_sff);
> + }
> +
return match;
> + if (match)
> + return 1;
> +
> + return 0;
> +}
> +
> +static int em_canid_change(struct tcf_proto *tp, void *data, int len,
> + struct tcf_ematch *m)
> +{
> + struct can_filter *conf = data; /* Array with rules,
> + * fixed size EM_CAN_RULES_SIZE
> + */
> + struct canid_match *cm;
> + int err;
> + int i;
> +
> + if (len < sizeof(struct can_filter))
> + return -EINVAL;
if (len % sizeof(struct can_filter))
return -EINVAL;
if (len > sizeof(struct can_filter) * EM_CAN_RULES_SIZE)
return -EINVAL;
All checks done before kzalloc() => no need for error cleanups at the end of
the function.
> +
> + err = -ENOBUFS;
remove
> + cm = kzalloc(sizeof(*cm), GFP_KERNEL);
> + if (cm == NULL)
if (!cm)
return -ENOMEM;
> + goto errout;
The only user of errout - to be removed.
> +
> + cm->sff_rules_count = 0;
> + cm->eff_rules_count = 0;
> + cm->rules_count = len/sizeof(struct can_filter);
> + err = -EINVAL;
remove
> +
> + /* Be sure to fit into the array */
> + if (cm->rules_count > EM_CAN_RULES_SIZE)
> + goto errout_free;
already checked before => remove
> +
> + /*
> + * We need two for() loops for copying rules into
> + * two contiguous areas in rules_raw
> + */
> +
> + /* Process EFF frame rules*/
> + for (i = 0; i < cm->rules_count; i++) {
> + if ((conf[i].can_id & CAN_EFF_FLAG) &&
> + (conf[i].can_mask & CAN_EFF_FLAG)) {
> + memcpy(cm->rules_raw + cm->eff_rules_count,
Oops. Shouldn't this be
cm->rules_raw + cm->eff_rules_count * sizeof(struct can_filter),
???
> + &conf[i],
> + sizeof(struct can_filter));
> +
> + cm->eff_rules_count++;
> + } else {
> + continue;
> + }
omit { } around continue
> + }
> +
> + /* Process SFF frame rules */
> + for (i = 0; i < cm->rules_count; i++) {
> + if ((conf[i].can_id & CAN_EFF_FLAG) &&
> + (conf[i].can_mask & CAN_EFF_FLAG)) {
What if CAN_EFF_FLAG is set in can_id but not in can_mask ?
> + continue;
> + } else {
> + memcpy(cm->rules_raw
> + + cm->eff_rules_count
> + + cm->sff_rules_count,
dito
cm->rules_raw + (cm->eff_rules_count + cm->sff_rules_count) * sizeof(struct
can_filter),
???
> + &conf[i], sizeof(struct can_filter));
> +
> + cm->sff_rules_count++;
> +
> + em_canid_sff_match_add(cm,
> + conf[i].can_id, conf[i].can_mask);
> + }
> + }
> +
> + m->datalen = sizeof(*cm);
> + m->data = (unsigned long) cm;
> +
> + return 0;
> +
> +errout_free:
> + kfree(cm);
> +errout:
> + return err;
error handling can be removed with the above changes.
> +}
> +
> +static void em_canid_destroy(struct tcf_proto *tp, struct tcf_ematch *m)
> +{
> + struct canid_match *cm = em_canid_priv(m);
> +
Check for cm == NULL not needed ?
> + kfree(cm);
> +}
> +
> +static int em_canid_dump(struct sk_buff *skb, struct tcf_ematch *m)
> +{
> + struct canid_match *cm = em_canid_priv(m);
> +
Check for cm == NULL not needed ?
Can a dump happen before the matches are added??
> + /*
> + * When configuring this ematch 'rules_count' is set not to exceed
> + * 'rules_raw' array size
> + */
> + if (nla_put_nohdr(skb, sizeof(cm->rules_raw[0]) * cm->rules_count,
better sizeof(struct can_filter) instead of sizeof(cm->rules_raw[0]) ??
> + &cm->rules_raw) < 0)
> + goto nla_put_failure;
> +
> + return 0;
> +
> +nla_put_failure:
> + return -1;
> +}
> +
> +static struct tcf_ematch_ops em_canid_ops = {
> + .kind = TCF_EM_CANID,
> + .change = em_canid_change,
> + .match = em_canid_match,
> + .destroy = em_canid_destroy,
> + .dump = em_canid_dump,
> + .owner = THIS_MODULE,
> + .link = LIST_HEAD_INIT(em_canid_ops.link)
> +};
> +
> +static int __init init_em_canid(void)
> +{
> + return tcf_em_register(&em_canid_ops);
> +}
> +
> +static void __exit exit_em_canid(void)
> +{
> + tcf_em_unregister(&em_canid_ops);
> +}
> +
> +MODULE_LICENSE("GPL");
> +
> +module_init(init_em_canid);
> +module_exit(exit_em_canid);
> +
> +MODULE_ALIAS_TCF_EMATCH(TCF_EM_CANID);
Regards,
Oliver
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