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skb: Add skb_head_is_locked helper function 

This patch adds support for a skb_head_is_locked helper function.  It is
meant to be used any time we are considering transferring the head from
skb->head to a paged frag.  If the head is locked it means we cannot remove
the head from the skb so it must be copied or we must take the skb as a
whole.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexander Duyck 2012-05-03 01:09:42 +00:00 committed by David S. Miller
parent 715dc1f342
commit 3a7c1ee4ab
3 changed files with 16 additions and 3 deletions
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14
include/linux/skbuff.h
View File

@ -2566,5 +2566,19 @@ static inline bool skb_is_recycleable(const struct sk_buff *skb, int skb_size)
return true;
}
/**
* skb_head_is_locked - Determine if the skb->head is locked down
* @skb: skb to check
*
* The head on skbs build around a head frag can be removed if they are
* not cloned. This function returns true if the skb head is locked down
* due to either being allocated via kmalloc, or by being a clone with
* multiple references to the head.
*/
static inline bool skb_head_is_locked(const struct sk_buff *skb)
{
return !skb->head_frag || skb_cloned(skb);
}
#endif /* __KERNEL__ */
#endif /* _LINUX_SKBUFF_H */

3
net/core/skbuff.c
View File

@ -1699,7 +1699,6 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
struct splice_pipe_desc *spd, struct sock *sk)
{
int seg;
bool head_is_locked = !skb->head_frag || skb_cloned(skb);
/* map the linear part :
* If skb->head_frag is set, this 'linear' part is backed by a
@ -1710,7 +1709,7 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
(unsigned long) skb->data & (PAGE_SIZE - 1),
skb_headlen(skb),
offset, len, skb, spd,
head_is_locked,
skb_head_is_locked(skb),
sk, pipe))
return true;

2
net/ipv4/tcp_input.c
View File

@ -4568,7 +4568,7 @@ static bool tcp_try_coalesce(struct sock *sk,
skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS)
return false;
if (!from->head_frag || skb_cloned(from))
if (skb_head_is_locked(from))
return false;
delta = from->truesize - SKB_DATA_ALIGN(sizeof(struct sk_buff));