block: clear drain buffer if draining for write command
Clear drain buffer before chaining if the command in question is a
write.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-merge.c b/block/blk-merge.c
index bef1b4d..7506c4f 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -221,6 +221,9 @@
} /* 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),