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Commit 04a4bb55 authored by Lennert Buytenhek's avatar Lennert Buytenhek Committed by David S. Miller
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net: add skb_recycle_check() to enable netdriver skb recycling 



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: default avatarLennert Buytenhek <buytenh@marvell.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 788df732

include/linux/skbuff.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

net/core/skbuff.c

+39 −2
Original line number Diff line number Diff line
@@ -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;