From: Tejun Heo <htejun@gmail.com>
Date: Tue, 19 Feb 2008 10:36:55 +0000 (+0100)
Subject: block: clear drain buffer if draining for write command
X-Git-Tag: v2.6.25-rc3~122^2~2
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=db0a2e0099be3a1cff55879225881465f16c67d3;p=pandora-kernel.git

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 bef1b4d0fc02..7506c4fe0264 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -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),