fs: make mpage read/write_pages() plug

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

fs/mpage.c

@@ -364,6 +364,9 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages,
 	sector_t last_block_in_bio = 0;
 	struct buffer_head map_bh;
 	unsigned long first_logical_block = 0;
+	struct blk_plug plug;
+
+	blk_start_plug(&plug);
 
 	map_bh.b_state = 0;
 	map_bh.b_size = 0;
@@ -385,6 +388,7 @@ mpage_readpages(struct address_space *mapping, struct list_head *pages,
 	BUG_ON(!list_empty(pages));
 	if (bio)
 		mpage_bio_submit(READ, bio);
+	blk_finish_plug(&plug);
 	return 0;
 }
 EXPORT_SYMBOL(mpage_readpages);
@@ -666,8 +670,11 @@ int
 mpage_writepages(struct address_space *mapping,
 		struct writeback_control *wbc, get_block_t get_block)
 {
+	struct blk_plug plug;
 	int ret;
 
+	blk_start_plug(&plug);
+
 	if (!get_block)
 		ret = generic_writepages(mapping, wbc);
 	else {
@@ -682,6 +689,7 @@ mpage_writepages(struct address_space *mapping,
 		if (mpd.bio)
 			mpage_bio_submit(WRITE, mpd.bio);
 	}
+	blk_finish_plug(&plug);
 	return ret;
 }
 EXPORT_SYMBOL(mpage_writepages);