readahead: split ondemand readahead interface into two functions

Split ondemand readahead interface into two functions.  I think this makes it
a little clearer for non-readahead experts (like Rusty).

Internally they both call ondemand_readahead(), but the page argument is
changed to an obvious boolean flag.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ext3/dir.c b/fs/ext3/dir.c
index 3c6d384..c00723a 100644
--- a/fs/ext3/dir.c
+++ b/fs/ext3/dir.c
@@ -139,10 +139,10 @@
 			pgoff_t index = map_bh.b_blocknr >>
 					(PAGE_CACHE_SHIFT - inode->i_blkbits);
 			if (!ra_has_index(&filp->f_ra, index))
-				page_cache_readahead_ondemand(
+				page_cache_sync_readahead(
 					sb->s_bdev->bd_inode->i_mapping,
 					&filp->f_ra, filp,
-					NULL, index, 1);
+					index, 1);
 			filp->f_ra.prev_index = index;
 			bh = ext3_bread(NULL, inode, blk, 0, &err);
 		}
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index 0a872a0..3ab01c0 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -138,10 +138,10 @@
 			pgoff_t index = map_bh.b_blocknr >>
 					(PAGE_CACHE_SHIFT - inode->i_blkbits);
 			if (!ra_has_index(&filp->f_ra, index))
-				page_cache_readahead_ondemand(
+				page_cache_sync_readahead(
 					sb->s_bdev->bd_inode->i_mapping,
 					&filp->f_ra, filp,
-					NULL, index, 1);
+					index, 1);
 			filp->f_ra.prev_index = index;
 			bh = ext4_bread(NULL, inode, blk, 0, &err);
 		}
diff --git a/fs/splice.c b/fs/splice.c
index 6ddd032..22496d2 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -295,8 +295,8 @@
 	 * readahead/allocate the rest and fill in the holes.
 	 */
 	if (spd.nr_pages < nr_pages)
-		page_cache_readahead_ondemand(mapping, &in->f_ra, in,
-				NULL, index, req_pages - spd.nr_pages);
+		page_cache_sync_readahead(mapping, &in->f_ra, in,
+				index, req_pages - spd.nr_pages);
 
 	error = 0;
 	while (spd.nr_pages < nr_pages) {
@@ -352,7 +352,7 @@
 		page = pages[page_nr];
 
 		if (PageReadahead(page))
-			page_cache_readahead_ondemand(mapping, &in->f_ra, in,
+			page_cache_async_readahead(mapping, &in->f_ra, in,
 					page, index, req_pages - page_nr);
 
 		/*