[PATCH 07/17] xfrm: state: don't use lock anymore unless acquire operation is needed

[Steffen Klassert]

From: Florian Westphal <f...@strlen.de>

push the lock down, after earlier patches we can rely on rcu to
make sure state struct won't go away.

Signed-off-by: Florian Westphal <f...@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klass...@secunet.com>
---
 include/net/netns/xfrm.h | 6 +++---
 net/xfrm/xfrm_state.c    | 6 ++++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
index 24cd394..1ab51d1 100644
--- a/include/net/netns/xfrm.h
+++ b/include/net/netns/xfrm.h
@@ -38,9 +38,9 @@ struct netns_xfrm {
         * mode. Also, it can be used by ah/esp icmp error handler to find
         * offending SA.
         */
-       struct hlist_head       *state_bydst;
-       struct hlist_head       *state_bysrc;
-       struct hlist_head       *state_byspi;
+       struct hlist_head       __rcu *state_bydst;
+       struct hlist_head       __rcu *state_bysrc;
+       struct hlist_head       __rcu *state_byspi;
        unsigned int            state_hmask;
        unsigned int            state_num;
        struct work_struct      state_hash_work;
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 53e7867..1a15b65 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -799,7 +799,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const 
xfrm_address_t *saddr,
 
        sequence = read_seqcount_begin(&xfrm_state_hash_generation);
 
-       spin_lock_bh(&net->xfrm.xfrm_state_lock);
+       rcu_read_lock();
        h = xfrm_dst_hash(net, daddr, saddr, tmpl->reqid, encap_family);
        hlist_for_each_entry_rcu(x, net->xfrm.state_bydst + h, bydst) {
                if (x->props.family == encap_family &&
@@ -870,6 +870,7 @@ found:
                }
 
                if (km_query(x, tmpl, pol) == 0) {
+                       spin_lock_bh(&net->xfrm.xfrm_state_lock);
                        x->km.state = XFRM_STATE_ACQ;
                        list_add(&x->km.all, &net->xfrm.state_all);
                        hlist_add_head_rcu(&x->bydst, net->xfrm.state_bydst + 
h);
@@ -883,6 +884,7 @@ found:
                        tasklet_hrtimer_start(&x->mtimer, 
ktime_set(net->xfrm.sysctl_acq_expires, 0), HRTIMER_MODE_REL);
                        net->xfrm.state_num++;
                        xfrm_hash_grow_check(net, x->bydst.next != NULL);
+                       spin_unlock_bh(&net->xfrm.xfrm_state_lock);
                } else {
                        x->km.state = XFRM_STATE_DEAD;
                        to_put = x;
@@ -899,7 +901,7 @@ out:
        } else {
                *err = acquire_in_progress ? -EAGAIN : error;
        }
-       spin_unlock_bh(&net->xfrm.xfrm_state_lock);
+       rcu_read_unlock();
        if (to_put)
                xfrm_state_put(to_put);
 
-- 
1.9.1