mm: un-export wake_up_page functions

These are no longer used outside mm/filemap.c, so un-export them and
make them static where possible.  These were exported specifically for
NFS use in commit a4796e37c1 ("MM: export page_wakeup functions").

Link: http://lkml.kernel.org/r/20170103182234.30141-3-npiggin@gmail.com
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/pagemap.h

@@ -482,19 +482,11 @@ static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
 }
 
 /*
- * This is exported only for wait_on_page_locked/wait_on_page_writeback,
- * and for filesystems which need to wait on PG_private.
+ * This is exported only for wait_on_page_locked/wait_on_page_writeback, etc.,
+ * and should not be used directly.
  */
 extern void wait_on_page_bit(struct page *page, int bit_nr);
 extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
-extern void wake_up_page_bit(struct page *page, int bit_nr);
-
-static inline void wake_up_page(struct page *page, int bit)
-{
-	if (!PageWaiters(page))
-		return;
-	wake_up_page_bit(page, bit);
-}
 
 /* 
  * Wait for a page to be unlocked.

mm/filemap.c

@@ -788,7 +788,7 @@ static int wake_page_function(wait_queue_t *wait, unsigned mode, int sync, void
 	return autoremove_wake_function(wait, mode, sync, key);
 }
 
-void wake_up_page_bit(struct page *page, int bit_nr)
+static void wake_up_page_bit(struct page *page, int bit_nr)
 {
 	wait_queue_head_t *q = page_waitqueue(page);
 	struct wait_page_key key;
@@ -821,7 +821,13 @@ void wake_up_page_bit(struct page *page, int bit_nr)
 	}
 	spin_unlock_irqrestore(&q->lock, flags);
 }
-EXPORT_SYMBOL(wake_up_page_bit);
+
+static void wake_up_page(struct page *page, int bit)
+{
+	if (!PageWaiters(page))
+		return;
+	wake_up_page_bit(page, bit);
+}
 
 static inline int wait_on_page_bit_common(wait_queue_head_t *q,
 		struct page *page, int bit_nr, int state, bool lock)