swap: remove unused mem_cgroup_uncharge_swapcache declaration

The body of this function was removed by commit 0a31bc97 ("mm:
memcontrol: rewrite uncharge API").
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/swap.h

@@ -437,16 +437,6 @@ extern int reuse_swap_page(struct page *);
 extern int try_to_free_swap(struct page *);
 struct backing_dev_info;
 
-#ifdef CONFIG_MEMCG
-extern void
-mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout);
-#else
-static inline void
-mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
-{
-}
-#endif
-
 #else /* CONFIG_SWAP */
 
 #define swap_address_space(entry)		(NULL)
@@ -547,11 +537,6 @@ static inline swp_entry_t get_swap_page(void)
 	return entry;
 }
 
-static inline void
-mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
-{
-}
-
 #endif /* CONFIG_SWAP */
 #endif /* __KERNEL__*/
 #endif /* _LINUX_SWAP_H */

mm/shmem.c

@@ -1131,7 +1131,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 			 * truncated or holepunched since swap was confirmed.
 			 * shmem_undo_range() will have done some of the
 			 * unaccounting, now delete_from_swap_cache() will do
-			 * the rest (including mem_cgroup_uncharge_swapcache).
+			 * the rest.
 			 * Reset swap.val? No, leave it so "failed" goes back to
 			 * "repeat": reading a hole and writing should succeed.
 			 */