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authorFlorian Westphal <fw@strlen.de>2016-08-11 15:17:53 +0200
committerSteffen Klassert <steffen.klassert@secunet.com>2016-08-12 08:07:11 +0200
commite1e551bc56302b80ff930c966f9985095fb1b70d (patch)
treebabb24413c09e1ab5ca3a6d690320b05d499204f /net/xfrm
parenta5eefc1df641f3c99fe54b309e7b79c18cec4a1e (diff)
downloadop-kernel-dev-e1e551bc56302b80ff930c966f9985095fb1b70d.zip
op-kernel-dev-e1e551bc56302b80ff930c966f9985095fb1b70d.tar.gz
xfrm: policy: prepare policy_bydst hash for rcu lookups
Since commit 56f047305dd4b6b617 ("xfrm: add rcu grace period in xfrm_policy_destroy()") xfrm policy objects are already free'd via rcu. In order to make more places lockless (i.e. use rcu_read_lock instead of grabbing read-side of policy rwlock) we only need to: - use rcu_assign_pointer to store address of new hash table backend memory - add rcu barrier so that freeing of old memory is delayed (expansion and free happens from system workqueue, so synchronize_rcu is fine) - use rcu_dereference to fetch current address of the hash table. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Diffstat (limited to 'net/xfrm')
-rw-r--r--net/xfrm/xfrm_policy.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 93b8ff7..4a8d90a 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -385,9 +385,11 @@ static struct hlist_head *policy_hash_bysel(struct net *net,
__get_hash_thresh(net, family, dir, &dbits, &sbits);
hash = __sel_hash(sel, family, hmask, dbits, sbits);
- return (hash == hmask + 1 ?
- &net->xfrm.policy_inexact[dir] :
- net->xfrm.policy_bydst[dir].table + hash);
+ if (hash == hmask + 1)
+ return &net->xfrm.policy_inexact[dir];
+
+ return rcu_dereference_check(net->xfrm.policy_bydst[dir].table,
+ lockdep_is_held(&net->xfrm.xfrm_policy_lock)) + hash;
}
static struct hlist_head *policy_hash_direct(struct net *net,
@@ -403,7 +405,8 @@ static struct hlist_head *policy_hash_direct(struct net *net,
__get_hash_thresh(net, family, dir, &dbits, &sbits);
hash = __addr_hash(daddr, saddr, family, hmask, dbits, sbits);
- return net->xfrm.policy_bydst[dir].table + hash;
+ return rcu_dereference_check(net->xfrm.policy_bydst[dir].table,
+ lockdep_is_held(&net->xfrm.xfrm_policy_lock)) + hash;
}
static void xfrm_dst_hash_transfer(struct net *net,
@@ -468,8 +471,8 @@ static void xfrm_bydst_resize(struct net *net, int dir)
unsigned int hmask = net->xfrm.policy_bydst[dir].hmask;
unsigned int nhashmask = xfrm_new_hash_mask(hmask);
unsigned int nsize = (nhashmask + 1) * sizeof(struct hlist_head);
- struct hlist_head *odst = net->xfrm.policy_bydst[dir].table;
struct hlist_head *ndst = xfrm_hash_alloc(nsize);
+ struct hlist_head *odst;
int i;
if (!ndst)
@@ -477,14 +480,19 @@ static void xfrm_bydst_resize(struct net *net, int dir)
write_lock_bh(&net->xfrm.xfrm_policy_lock);
+ odst = rcu_dereference_protected(net->xfrm.policy_bydst[dir].table,
+ lockdep_is_held(&net->xfrm.xfrm_policy_lock));
+
for (i = hmask; i >= 0; i--)
xfrm_dst_hash_transfer(net, odst + i, ndst, nhashmask, dir);
- net->xfrm.policy_bydst[dir].table = ndst;
+ rcu_assign_pointer(net->xfrm.policy_bydst[dir].table, ndst);
net->xfrm.policy_bydst[dir].hmask = nhashmask;
write_unlock_bh(&net->xfrm.xfrm_policy_lock);
+ synchronize_rcu();
+
xfrm_hash_free(odst, (hmask + 1) * sizeof(struct hlist_head));
}
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