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net: add skb_recycle_check() to enable netdriver skb recycling

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This patch adds skb_recycle_check(), which can be used by a network
driver after transmitting an skb to check whether this skb can be
recycled as a receive buffer.

skb_recycle_check() checks that the skb is not shared or cloned, and
that it is linear and its head portion large enough (as determined by
the driver) to be recycled as a receive buffer.  If these conditions
are met, it does any necessary reference count dropping and cleans
up the skbuff as if it just came from __alloc_skb().

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Lennert Buytenhek 2008-10-01 02:33:12 -07:00 committed by David S. Miller
parent 788df7322a
commit 04a4bb55bc
2 changed files with 41 additions and 2 deletions
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2
include/linux/skbuff.h
View file

@ -383,6 +383,8 @@ static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
return __alloc_skb(size, priority, 1, -1);
}
extern int skb_recycle_check(struct sk_buff *skb, int skb_size);
extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
extern struct sk_buff *skb_clone(struct sk_buff *skb,
gfp_t priority);

41
net/core/skbuff.c
View file

@ -363,8 +363,7 @@ static void kfree_skbmem(struct sk_buff *skb)
}
}
/* Free everything but the sk_buff shell. */
static void skb_release_all(struct sk_buff *skb)
static void skb_release_head_state(struct sk_buff *skb)
{
dst_release(skb->dst);
#ifdef CONFIG_XFRM
@ -388,6 +387,12 @@ static void skb_release_all(struct sk_buff *skb)
skb->tc_verd = 0;
#endif
#endif
}
/* Free everything but the sk_buff shell. */
static void skb_release_all(struct sk_buff *skb)
{
skb_release_head_state(skb);
skb_release_data(skb);
}
@ -424,6 +429,38 @@ void kfree_skb(struct sk_buff *skb)
__kfree_skb(skb);
}
int skb_recycle_check(struct sk_buff *skb, int skb_size)
{
struct skb_shared_info *shinfo;
if (skb_is_nonlinear(skb) || skb->fclone != SKB_FCLONE_UNAVAILABLE)
return 0;
skb_size = SKB_DATA_ALIGN(skb_size + NET_SKB_PAD);
if (skb_end_pointer(skb) - skb->head < skb_size)
return 0;
if (skb_shared(skb) || skb_cloned(skb))
return 0;
skb_release_head_state(skb);
shinfo = skb_shinfo(skb);
atomic_set(&shinfo->dataref, 1);
shinfo->nr_frags = 0;
shinfo->gso_size = 0;
shinfo->gso_segs = 0;
shinfo->gso_type = 0;
shinfo->ip6_frag_id = 0;
shinfo->frag_list = NULL;
memset(skb, 0, offsetof(struct sk_buff, tail));
skb_reset_tail_pointer(skb);
skb->data = skb->head + NET_SKB_PAD;
return 1;
}
EXPORT_SYMBOL(skb_recycle_check);
static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
{
new->tstamp = old->tstamp;