From b3b73b8e6df685ba61476b256f98eff1d650c199 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 5 Jan 2017 13:23:58 +0100 Subject: [PATCH] xfrm: state: do not acquire lock in get_mtu helpers Once flow cache gets removed the mtu initialisation happens for every skb that gets an xfrm attached, so this lock starts to show up in perf. It is not obvious why this lock is required -- the caller holds reference on the state struct, type->destructor is only called from the state gc worker (all state structs on gc list must have refcount 0). xfrm_init_state already has been called (else private data accessed by type->get_mtu() would not be set up). So just remove the lock -- the race on the state (DEAD?) doesn't matter (could change right after dropping the lock too). Signed-off-by: Florian Westphal Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_state.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index c5cf4d611aab..6b3366fef019 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -2000,16 +2000,13 @@ EXPORT_SYMBOL(xfrm_state_delete_tunnel); int xfrm_state_mtu(struct xfrm_state *x, int mtu) { - int res; + const struct xfrm_type *type = READ_ONCE(x->type); - spin_lock_bh(&x->lock); if (x->km.state == XFRM_STATE_VALID && - x->type && x->type->get_mtu) - res = x->type->get_mtu(x, mtu); - else - res = mtu - x->props.header_len; - spin_unlock_bh(&x->lock); - return res; + type && type->get_mtu) + return type->get_mtu(x, mtu); + + return mtu - x->props.header_len; } int __xfrm_init_state(struct xfrm_state *x, bool init_replay)