Initial blktrace support

This doesn't work yet, just committing what little bits I did as not
to lose them.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/log.c b/log.c
index 9669b4a..fbc407d 100644
--- a/log.c
+++ b/log.c
@@ -199,9 +199,16 @@
 	if (td->io_ops->flags & FIO_DISKLESSIO)
 		return 0;
 
-	if (td->o.read_iolog_file)
-		ret = init_iolog_read(td);
-	else if (td->o.write_iolog_file)
+	if (td->o.read_iolog_file) {
+		/*
+		 * Check if it's a blktrace file and load that if possible.
+		 * Otherwise assume it's a normal log file and load that.
+		 */
+		if (is_blktrace(td->o.read_iolog_file))
+			ret = load_blktrace(td, td->o.read_iolog_file);
+		else
+			ret = init_iolog_read(td);
+	} else if (td->o.write_iolog_file)
 		ret = init_iolog_write(td);
 
 	return ret;