mm/readahead.c: remove unused file_ra_state from count_history_pages

count_history_pages does only call page_cache_prev_hole in rcu_lock
context using address_space mapping.  There's no need to have
file_ra_state here.
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Acked-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/readahead.c

@@ -326,7 +326,6 @@ static unsigned long get_next_ra_size(struct file_ra_state *ra,
  * 	- thrashing threshold in memory tight systems
  */
 static pgoff_t count_history_pages(struct address_space *mapping,
-				   struct file_ra_state *ra,
 				   pgoff_t offset, unsigned long max)
 {
 	pgoff_t head;
@@ -349,7 +348,7 @@ static int try_context_readahead(struct address_space *mapping,
 {
 	pgoff_t size;
 
-	size = count_history_pages(mapping, ra, offset, max);
+	size = count_history_pages(mapping, offset, max);
 
 	/*
 	 * not enough history pages: