From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Westphal Subject: [RFC 1/3] xfrm: state: do not acquire lock in get_mtu helpers Date: Tue, 27 Sep 2016 18:05:21 +0200 Message-ID: <1474992323-11327-2-git-send-email-fw@strlen.de> References: <1474992323-11327-1-git-send-email-fw@strlen.de> Cc: Florian Westphal To: Return-path: Received: from Chamillionaire.breakpoint.cc ([146.0.238.67]:53292 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934325AbcI0QFd (ORCPT ); Tue, 27 Sep 2016 12:05:33 -0400 In-Reply-To: <1474992323-11327-1-git-send-email-fw@strlen.de> Sender: netdev-owner@vger.kernel.org List-ID: Once flow cache is removed the mtu initialisation happens for every skb that gets an xfrm attached to it. It is not obvious why this lock is required -- the caller holds reference on the state struct. 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 --- 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 f9a255457a1d..bf5969aa7dc2 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -2008,16 +2008,13 @@ 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) -- 2.7.3