btrfs: make end_bio_extent_writepage() to be subpage compatible

Now in end_bio_extent_writepage(), the only subpage incompatible code is
the end_page_writeback().

Just call the subpage helpers.

Tested-by: Ritesh Harjani <[email protected]> # [ppc64]
Tested-by: Anand Jain <[email protected]> # [aarch64]
Reviewed-by: Josef Bacik <[email protected]>
Signed-off-by: Qu Wenruo <[email protected]>
Signed-off-by: David Sterba <[email protected]>

fs/btrfs/extent_io.c

@@ -2853,7 +2853,8 @@ static void end_bio_extent_writepage(struct bio *bio)
 		}
 
 		end_extent_writepage(page, error, start, end);
-		end_page_writeback(page);
+
+		btrfs_page_clear_writeback(fs_info, page, start, bvec->bv_len);
 	}
 
 	bio_put(bio);