block: clear drain buffer if draining for write command
Tejun Heo [Tue, 19 Feb 2008 10:36:55 +0000 (11:36 +0100)]
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>

block/blk-merge.c

index bef1b4d..7506c4f 100644 (file)
@@ -221,6 +221,9 @@ new_segment:
        } /* 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),