net: Use __skb_pagelen() directly in skb_cow_data()
Miaohe Lin authored

In fact, skb_pagelen() - skb_headlen() is equal to __skb_pagelen(), use it
directly to avoid unnecessary skb_headlen() call.

Also fix the CHECK note of checkpatch.pl:
    Comparison to NULL could be written "!__pskb_pull_tail"
Signed-off-by: default avatarMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
c15fc199