diff --git a/[refs] b/[refs]
index 9ae677799096..15978b0e00b9 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 2fb98e8414c42cb14698833aac640b143b9ade4f
+refs/heads/master: db0a2e0099be3a1cff55879225881465f16c67d3
diff --git a/trunk/block/blk-merge.c b/trunk/block/blk-merge.c
index bef1b4d0fc02..7506c4fe0264 100644
--- a/trunk/block/blk-merge.c
+++ b/trunk/block/blk-merge.c
@@ -221,6 +221,9 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 	} /* segments in rq */
 
 	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
+		if (rq->cmd_flags & REQ_RW)
+			memset(q->dma_drain_buffer, 0, q->dma_drain_size);
+
 		sg->page_link &= ~0x02;
 		sg = sg_next(sg);
 		sg_set_page(sg, virt_to_page(q->dma_drain_buffer),