Re: [Patch net-next v3] net: clean up skb headers code
flat view
From: Simon Horman <horms@verge.net.au>
Date: 2013-05-31 00:24:33
On Thu, May 30, 2013 at 10:06:15AM +0800, Cong Wang wrote:
From: Cong Wang <redacted> 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 <redacted> Cc: David S. Miller <davem@davemloft.net> Cc: Simon Horman <horms@verge.net.au> Signed-off-by: Cong Wang <redacted>
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.
quoted hunk ↗ jump to hunk
--- v2: use typeof v3: use ~(typeof(X))0diff --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);