[PATCH v3] include/linux/skbuff.h: using '(__u16) ~0U' instead of '~0U'

Chen Gang
2013-06-05T02:55:23Z

Both 'transport_header' and 'mac_header' are __u16, which are
never equal to '~0U'.

So need use '(__u16) ~0U' instead of '~0U'.

The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
...

Use meaningful macro instead of hard code number, and better to
initialize 'skb->transport_header' in __alloc_skb_head(), too.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
---
include/linux/skbuff.h | 6 ++++--
net/core/skbuff.c | 11 ++++++-----
2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5f93119..3314911 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -40,6 +40,8 @@
#define CHECKSUM_COMPLETE 2
#define CHECKSUM_PARTIAL 3

+#define SKB_HEADER_OFFSET_UNSET ((__u16) ~0U)
+
#define SKB_DATA_ALIGN(X) (((X) + (SMP_CACHE_BYTES - 1)) & \
~(SMP_CACHE_BYTES - 1))
#define SKB_WITH_OVERHEAD(X) \
@@ -1593,7 +1595,7 @@ 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 != SKB_HEADER_OFFSET_UNSET;
}

static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
@@ -1636,7 +1638,7 @@ 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 != SKB_HEADER_OFFSET_UNSET;
}

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..6808433 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -200,7 +200,8 @@ struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
atomic_set(&skb->users, 1);

#ifdef NET_SKBUFF_DATA_USES_OFFSET
- skb->mac_header = (__u16) ~0U;
+ skb->mac_header = SKB_HEADER_OFFSET_UNSET;
+ skb->transport_header = SKB_HEADER_OFFSET_UNSET;
#endif
out:
return skb;
@@ -276,8 +277,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
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;
+ skb->mac_header = SKB_HEADER_OFFSET_UNSET;
+ skb->transport_header = SKB_HEADER_OFFSET_UNSET;
#endif

/* make sure we initialize shinfo sequentially */
@@ -345,8 +346,8 @@ struct sk_buff *build_skb(void *data, unsigned int frag_size)
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;
+ skb->mac_header = SKB_HEADER_OFFSET_UNSET;
+ skb->transport_header = SKB_HEADER_OFFSET_UNSET;
#endif

/* make sure we initialize shinfo sequentially */
--
1.7.7.6