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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: Lennert Buytenhek <buytenh@marvell.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -383,6 +383,8 @@ static inline struct sk_buff *alloc_skb_fclone(unsigned int size,
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return __alloc_skb(size, priority, 1, -1);
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}
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extern int skb_recycle_check(struct sk_buff *skb, int skb_size);
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extern struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src);
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extern struct sk_buff *skb_clone(struct sk_buff *skb,
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gfp_t priority);
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@ -363,8 +363,7 @@ static void kfree_skbmem(struct sk_buff *skb)
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}
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}
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/* Free everything but the sk_buff shell. */
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static void skb_release_all(struct sk_buff *skb)
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static void skb_release_head_state(struct sk_buff *skb)
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{
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dst_release(skb->dst);
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#ifdef CONFIG_XFRM
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@ -388,6 +387,12 @@ static void skb_release_all(struct sk_buff *skb)
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skb->tc_verd = 0;
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#endif
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#endif
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}
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/* Free everything but the sk_buff shell. */
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static void skb_release_all(struct sk_buff *skb)
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{
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skb_release_head_state(skb);
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skb_release_data(skb);
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}
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@ -424,6 +429,38 @@ void kfree_skb(struct sk_buff *skb)
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__kfree_skb(skb);
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}
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int skb_recycle_check(struct sk_buff *skb, int skb_size)
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{
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struct skb_shared_info *shinfo;
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if (skb_is_nonlinear(skb) || skb->fclone != SKB_FCLONE_UNAVAILABLE)
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return 0;
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skb_size = SKB_DATA_ALIGN(skb_size + NET_SKB_PAD);
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if (skb_end_pointer(skb) - skb->head < skb_size)
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return 0;
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if (skb_shared(skb) || skb_cloned(skb))
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return 0;
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skb_release_head_state(skb);
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shinfo = skb_shinfo(skb);
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atomic_set(&shinfo->dataref, 1);
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shinfo->nr_frags = 0;
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shinfo->gso_size = 0;
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shinfo->gso_segs = 0;
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shinfo->gso_type = 0;
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shinfo->ip6_frag_id = 0;
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shinfo->frag_list = NULL;
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memset(skb, 0, offsetof(struct sk_buff, tail));
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skb_reset_tail_pointer(skb);
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skb->data = skb->head + NET_SKB_PAD;
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return 1;
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}
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EXPORT_SYMBOL(skb_recycle_check);
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static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
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{
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new->tstamp = old->tstamp;
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