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authorPaolo Abeni <pabeni@redhat.com>2018-07-30 14:30:43 +0200
committerDavid S. Miller <davem@davemloft.net>2018-07-30 09:31:13 -0700
commit7fd4b288ea6a3e45ad8afbcd5ec39554d57f1ae0 (patch)
tree6d839e231aeb7764681d03ef13732b0fd408ff72 /net/sched/act_skbmod.c
parentnet/sched: user-space can't set unknown tcfa_action values (diff)
downloadlinux-dev-7fd4b288ea6a3e45ad8afbcd5ec39554d57f1ae0.tar.xz
linux-dev-7fd4b288ea6a3e45ad8afbcd5ec39554d57f1ae0.zip
tc/act: remove unneeded RCU lock in action callback
Each lockless action currently does its own RCU locking in ->act(). This allows using plain RCU accessor, even if the context is really RCU BH. This change drops the per action RCU lock, replace the accessors with the _bh variant, cleans up a bit the surrounding code and documents the RCU status in the relevant header. No functional nor performance change is intended. The goal of this patch is clarifying that the RCU critical section used by the tc actions extends up to the classifier's caller. v1 -> v2: - preserve rcu lock in act_bpf: it's needed by eBPF helpers, as pointed out by Daniel v3 -> v4: - fixed some typos in the commit message (JiriP) Signed-off-by: Paolo Abeni <pabeni@redhat.com> Acked-by: Jiri Pirko <jiri@mellanox.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/act_skbmod.c')
-rw-r--r--net/sched/act_skbmod.c21
1 files changed, 9 insertions, 12 deletions
diff --git a/net/sched/act_skbmod.c b/net/sched/act_skbmod.c
index cdc6bacfb190..c437c6d51a71 100644
--- a/net/sched/act_skbmod.c
+++ b/net/sched/act_skbmod.c
@@ -41,20 +41,14 @@ static int tcf_skbmod_run(struct sk_buff *skb, const struct tc_action *a,
* then MAX_EDIT_LEN needs to change appropriately
*/
err = skb_ensure_writable(skb, MAX_EDIT_LEN);
- if (unlikely(err)) { /* best policy is to drop on the floor */
- qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
- return TC_ACT_SHOT;
- }
+ if (unlikely(err)) /* best policy is to drop on the floor */
+ goto drop;
- rcu_read_lock();
action = READ_ONCE(d->tcf_action);
- if (unlikely(action == TC_ACT_SHOT)) {
- qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
- rcu_read_unlock();
- return action;
- }
+ if (unlikely(action == TC_ACT_SHOT))
+ goto drop;
- p = rcu_dereference(d->skbmod_p);
+ p = rcu_dereference_bh(d->skbmod_p);
flags = p->flags;
if (flags & SKBMOD_F_DMAC)
ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
@@ -62,7 +56,6 @@ static int tcf_skbmod_run(struct sk_buff *skb, const struct tc_action *a,
ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
if (flags & SKBMOD_F_ETYPE)
eth_hdr(skb)->h_proto = p->eth_type;
- rcu_read_unlock();
if (flags & SKBMOD_F_SWAPMAC) {
u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
@@ -73,6 +66,10 @@ static int tcf_skbmod_run(struct sk_buff *skb, const struct tc_action *a,
}
return action;
+
+drop:
+ qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
+ return TC_ACT_SHOT;
}
static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {