From e1e551bc56302b80ff930c966f9985095fb1b70d Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 11 Aug 2016 15:17:53 +0200 Subject: 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 Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_policy.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) (limited to 'net/xfrm') diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 93b8ff74001f..4a8d90a88c83 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)); } -- cgit