From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Horman Subject: Re: [Patch net-next v3] net: clean up skb headers code Date: Fri, 31 May 2013 09:25:17 +0900 Message-ID: <20130531002517.GC26684@verge.net.au> References: <1369879575-18701-1-git-send-email-amwang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, Ben Hutchings , "David S. Miller" To: Cong Wang Return-path: Received: from kirsty.vergenet.net ([202.4.237.240]:41307 "EHLO kirsty.vergenet.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751505Ab3EaAYd (ORCPT ); Thu, 30 May 2013 20:24:33 -0400 Content-Disposition: inline In-Reply-To: <1369879575-18701-1-git-send-email-amwang@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, May 30, 2013 at 10:06:15AM +0800, Cong Wang wrote: > From: Cong Wang > > commit 1a37e412a0225fcba5587 (net: Use 16bits for *_headers > fields of struct skbuff) converts skb->*_header to u16, > some #if NET_SKBUFF_DATA_USES_OFFSET are now useless, > and to be safe, we could just use "X = ~(typeof(X))0;" > as suggested by David and Ben. > > Cc: Ben Hutchings > Cc: David S. Miller > Cc: Simon Horman > Signed-off-by: Cong Wang FWIW, I would prefer to see a patch that just removes the instances of #ifdef NET_SKBUFF_DATA_USES_OFFSET below, and then a separate patch to clean-up the use of ~0U once some consensus is reached on the best approach. The reason is that I suspect that the #ifdef NET_SKBUFF_DATA_USES_OFFSET is a bug fix for cases where it is not defined. Whereas the ~0 discussion is more cosmetic. > > --- > v2: use typeof > v3: use ~(typeof(X))0 > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > index 5f93119..f3c18a0 100644 > --- a/include/linux/skbuff.h > +++ b/include/linux/skbuff.h > @@ -1593,7 +1593,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb, > } > static inline bool skb_transport_header_was_set(const struct sk_buff *skb) > { > - return skb->transport_header != ~0U; > + return skb->transport_header != ~(typeof(skb->transport_header))0; > } > > static inline unsigned char *skb_transport_header(const struct sk_buff *skb) > @@ -1636,7 +1636,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb) > > static inline int skb_mac_header_was_set(const struct sk_buff *skb) > { > - return skb->mac_header != ~0U; > + return skb->mac_header != ~(typeof(skb->mac_header))0; > } > > static inline void skb_reset_mac_header(struct sk_buff *skb) > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index f45de07..e121c4b 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -199,9 +199,7 @@ struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node) > skb->truesize = sizeof(struct sk_buff); > atomic_set(&skb->users, 1); > > -#ifdef NET_SKBUFF_DATA_USES_OFFSET > - skb->mac_header = (__u16) ~0U; > -#endif > + skb->mac_header = ~(typeof(skb->mac_header))0; > out: > return skb; > } > @@ -275,10 +273,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, > skb->data = data; > skb_reset_tail_pointer(skb); > skb->end = skb->tail + size; > -#ifdef NET_SKBUFF_DATA_USES_OFFSET > - skb->mac_header = (__u16) ~0U; > - skb->transport_header = (__u16) ~0U; > -#endif > + skb->mac_header = ~(typeof(skb->mac_header))0; > + skb->transport_header = ~(typeof(skb->transport_header))0; > > /* make sure we initialize shinfo sequentially */ > shinfo = skb_shinfo(skb); > @@ -344,10 +340,8 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size) > skb->data = data; > skb_reset_tail_pointer(skb); > skb->end = skb->tail + size; > -#ifdef NET_SKBUFF_DATA_USES_OFFSET > - skb->mac_header = (__u16) ~0U; > - skb->transport_header = (__u16) ~0U; > -#endif > + skb->mac_header = ~(typeof(skb->mac_header))0; > + skb->transport_header = ~(typeof(skb->transport_header))0; > > /* make sure we initialize shinfo sequentially */ > shinfo = skb_shinfo(skb); >