skbuff: export mm_[un]account_pinned_pages for other modules

RDS would like to use the helper functions for managing pinned pages
added by Commit a91dbff551a6 ("sock: ulimit on MSG_ZEROCOPY pages")

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -466,6 +466,9 @@ struct ubuf_info {
 
 #define skb_uarg(SKB)	((struct ubuf_info *)(skb_shinfo(SKB)->destructor_arg))
 
+int mm_account_pinned_pages(struct mmpin *mmp, size_t size);
+void mm_unaccount_pinned_pages(struct mmpin *mmp);
+
 struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, size_t size);
 struct ubuf_info *sock_zerocopy_realloc(struct sock *sk, size_t size,
 					struct ubuf_info *uarg);

net/core/skbuff.c

@@ -890,7 +890,7 @@ struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src)
 }
 EXPORT_SYMBOL_GPL(skb_morph);
 
-static int mm_account_pinned_pages(struct mmpin *mmp, size_t size)
+int mm_account_pinned_pages(struct mmpin *mmp, size_t size)
 {
 	unsigned long max_pg, num_pg, new_pg, old_pg;
 	struct user_struct *user;
@@ -919,14 +919,16 @@ static int mm_account_pinned_pages(struct mmpin *mmp, size_t size)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(mm_account_pinned_pages);
 
-static void mm_unaccount_pinned_pages(struct mmpin *mmp)
+void mm_unaccount_pinned_pages(struct mmpin *mmp)
 {
 	if (mmp->user) {
 		atomic_long_sub(mmp->num_pg, &mmp->user->locked_vm);
 		free_uid(mmp->user);
 	}
 }
+EXPORT_SYMBOL_GPL(mm_unaccount_pinned_pages);
 
 struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, size_t size)
 {