net: Revert "net: avoid one atomic operation in skb_clone()"

net: Revert "net: avoid one atomic operation in skb_clone()"

Not sure what I was thinking, but doing anything after
releasing a refcount is suicidal or/and embarrassing.

By the time we set skb->fclone to SKB_FCLONE_FREE, another cpu
could have released last reference and freed whole skb.

We potentially corrupt memory or trap if CONFIG_DEBUG_PAGEALLOC is set.

Reported-by: Chris Mason <[email protected]>
Fixes: ce1a4ea3f1258 ("net: avoid one atomic operation in skb_clone()")
Signed-off-by: Eric Dumazet <[email protected]>
Cc: Sabrina Dubroca <[email protected]>
Signed-off-by: David S. Miller <[email protected]>