net: add documentation for skb recycling

Commit 04a4bb55bcf35b63d40fd2725e58599ff8310dd7 ("net: add
skb_recycle_check() to enable netdriver skb recycling") added a
method for network drivers to recycle skbuffs, but while use of
this mechanism was documented in the commit message, it should
really have been added as a docbook comment as well -- this
patch does that.

Signed-off-by: Stephen Hemminger <[e-mail]>
Signed-off-by: Lennert Buytenhek <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/skbuff.c

···
 	__kfree_skb(skb);
 }
 
+/**
+ *	skb_recycle_check - check if skb can be reused for receive
+ *	@skb: buffer
+ *	@skb_size: minimum receive buffer size
+ *
+ *	Checks that the skb passed in is not shared or cloned, and
+ *	that it is linear and its head portion at least as large as
+ *	skb_size so that it can be recycled as a receive buffer.
+ *	If these conditions are met, this function does any necessary
+ *	reference count dropping and cleans up the skbuff as if it
+ *	just came from __alloc_skb().
+ */
 int skb_recycle_check(struct sk_buff *skb, int skb_size)
 {
 	struct skb_shared_info *shinfo;