MM: export page_wakeup functions

This will allow NFS to wait for PG_private to be cleared and,
particularly, to send a wake-up when it is.
Signed-off-by: NNeilBrown <neilb@suse.de>
Acked-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

include/linux/pagemap.h

@@ -496,8 +496,8 @@ 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.
- * Never use this directly!
+ * This is exported only for wait_on_page_locked/wait_on_page_writeback,
+ * and for filesystems which need to wait on PG_private.
  */
 extern void wait_on_page_bit(struct page *page, int bit_nr);
 
@@ -512,6 +512,12 @@ static inline int wait_on_page_locked_killable(struct page *page)
 	return 0;
 }
 
+extern wait_queue_head_t *page_waitqueue(struct page *page);
+static inline void wake_up_page(struct page *page, int bit)
+{
+	__wake_up_bit(page_waitqueue(page), &page->flags, bit);
+}
+
 /* 
  * Wait for a page to be unlocked.
  *

mm/filemap.c

@@ -670,17 +670,13 @@ EXPORT_SYMBOL(__page_cache_alloc);
  * at a cost of "thundering herd" phenomena during rare hash
  * collisions.
  */
-static wait_queue_head_t *page_waitqueue(struct page *page)
+wait_queue_head_t *page_waitqueue(struct page *page)
 {
 	const struct zone *zone = page_zone(page);
 
 	return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
 }
-
-static inline void wake_up_page(struct page *page, int bit)
-{
-	__wake_up_bit(page_waitqueue(page), &page->flags, bit);
-}
+EXPORT_SYMBOL(page_waitqueue);
 
 void wait_on_page_bit(struct page *page, int bit_nr)
 {