[PATCH 3/4] blk-mq: handle dma_drain_size

Christoph Hellwig
2014-02-07T18:22:38Z

[-- Attachment #1: 0003-blk-mq-handle-dma_drain_size.patch --]
[-- Type: text/plain, Size: 874 bytes --]

Make blk-mq handle the dma_drain_size field the same way as the old request
path.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/blk-mq.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 40fc4dd..35800e1 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -561,6 +561,16 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
list_del_init(&rq->queuelist);
blk_mq_start_request(rq);

+ if (q->dma_drain_size && blk_rq_bytes(rq)) {
+ /*
+ * make sure space for the drain appears we
+ * know we can do this because max_hw_segments
+ * has been adjusted to be one fewer than the
+ * device can handle
+ */
+ rq->nr_phys_segments++;
+ }
+
/*
* Last request in the series. Flag it as such, this
* enables drivers to know when IO should be kicked off,
--
1.7.10.4