mm: introduce wait_on_page_locked_killable()

commit 2687a35 ("Add lock_page_killable") introduced killable
lock_page().  Similarly this patch introdues killable
wait_on_page_locked().

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/pagemap.h

@@ -357,6 +357,15 @@ static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
  */
 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);
+
+static inline int wait_on_page_locked_killable(struct page *page)
+{
+	if (PageLocked(page))
+		return wait_on_page_bit_killable(page, PG_locked);
+	return 0;
+}
+
 /* 
  * Wait for a page to be unlocked.
  *

mm/filemap.c

@@ -562,6 +562,17 @@ void wait_on_page_bit(struct page *page, int bit_nr)
 }
 EXPORT_SYMBOL(wait_on_page_bit);
 
+int wait_on_page_bit_killable(struct page *page, int bit_nr)
+{
+	DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
+
+	if (!test_bit(bit_nr, &page->flags))
+		return 0;
+
+	return __wait_on_bit(page_waitqueue(page), &wait,
+			     sleep_on_page_killable, TASK_KILLABLE);
+}
+
 /**
  * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
  * @page: Page defining the wait queue of interest