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net: add function to allocate sk_buff head without data area

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Add a function to allocate a sk_buff head without any data. This will
be used by memory mapped netlink to attach data from the mmaped area
to the skb.

Additionally change skb_release_all() to check whether the skb has a
data area to allow the skb destructor to clear the data pointer in case
only a head has been allocated.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick McHardy 2013-04-17 06:46:58 +00:00 committed by David S. Miller
parent e32123e598
commit 0ebd0ac5ff
2 changed files with 35 additions and 1 deletions
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6
include/linux/skbuff.h
View File

@ -651,6 +651,12 @@ static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
return __alloc_skb(size, priority, SKB_ALLOC_FCLONE, NUMA_NO_NODE);
}
extern struct sk_buff *__alloc_skb_head(gfp_t priority, int node);
static inline struct sk_buff *alloc_skb_head(gfp_t priority)
{
return __alloc_skb_head(priority, -1);
}
extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
extern int skb_copy_ubufs(struct sk_buff *skb, gfp_t gfp_mask);
extern struct sk_buff *skb_clone(struct sk_buff *skb,

30
net/core/skbuff.c
View File

@ -179,6 +179,33 @@ out:
*
*/
struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
{
struct sk_buff *skb;
/* Get the HEAD */
skb = kmem_cache_alloc_node(skbuff_head_cache,
gfp_mask & ~__GFP_DMA, node);
if (!skb)
goto out;
/*
* Only clear those fields we need to clear, not those that we will
* actually initialise below. Hence, don't put any more fields after
* the tail pointer in struct sk_buff!
*/
memset(skb, 0, offsetof(struct sk_buff, tail));
skb->data = NULL;
skb->truesize = sizeof(struct sk_buff);
atomic_set(&skb->users, 1);
#ifdef NET_SKBUFF_DATA_USES_OFFSET
skb->mac_header = ~0U;
#endif
out:
return skb;
}
/**
* __alloc_skb - allocate a network buffer
* @size: size to allocate
@ -584,7 +611,8 @@ static void skb_release_head_state(struct sk_buff *skb)
static void skb_release_all(struct sk_buff *skb)
{
skb_release_head_state(skb);
skb_release_data(skb);
if (likely(skb->data))
skb_release_data(skb);
}
/**