[PATCH] ifdef blktrace debugging fields

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/block/blktrace.c b/block/blktrace.c
index 2b4ef2b..8ff3344 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -450,8 +450,10 @@
  **/
 void blk_trace_shutdown(request_queue_t *q)
 {
-	blk_trace_startstop(q, 0);
-	blk_trace_remove(q);
+	if (q->blk_trace) {
+		blk_trace_startstop(q, 0);
+		blk_trace_remove(q);
+	}
 }
 
 /*