mm: remove file argument from swap_readpage()

The file argument resulted from address_space's readpage long time ago.

We don't use it any more.  Let's remove unnecessary argement.
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/swap.h

@@ -256,7 +256,7 @@ extern void swap_unplug_io_fn(struct backing_dev_info *, struct page *);
 
 #ifdef CONFIG_SWAP
 /* linux/mm/page_io.c */
-extern int swap_readpage(struct file *, struct page *);
+extern int swap_readpage(struct page *);
 extern int swap_writepage(struct page *page, struct writeback_control *wbc);
 extern void end_swap_bio_read(struct bio *bio, int err);
 

mm/page_io.c

@@ -120,7 +120,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
 	return ret;
 }
 
-int swap_readpage(struct file *file, struct page *page)
+int swap_readpage(struct page *page)
 {
 	struct bio *bio;
 	int ret = 0;

mm/swap_state.c

@@ -313,7 +313,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 			 * Initiate read into locked page and return.
 			 */
 			lru_cache_add_anon(new_page);
-			swap_readpage(NULL, new_page);
+			swap_readpage(new_page);
 			return new_page;
 		}
 		ClearPageSwapBacked(new_page);