block: implement request_queue->dma_drain_needed
Draining shouldn't be done for commands where overflow may indicate
data integrity issues. Add dma_drain_needed callback to
request_queue. Drain buffer is appened iff this function returns
non-zero.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 13536a3..9a8ffdd 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -296,6 +296,7 @@
* blk_queue_dma_drain - Set up a drain buffer for excess dma.
*
* @q: the request queue for the device
+ * @dma_drain_needed: fn which returns non-zero if drain is necessary
* @buf: physically contiguous buffer
* @size: size of the buffer in bytes
*
@@ -315,14 +316,16 @@
* device can support otherwise there won't be room for the drain
* buffer.
*/
-int blk_queue_dma_drain(struct request_queue *q, void *buf,
- unsigned int size)
+extern int blk_queue_dma_drain(struct request_queue *q,
+ dma_drain_needed_fn *dma_drain_needed,
+ void *buf, unsigned int size)
{
if (q->max_hw_segments < 2 || q->max_phys_segments < 2)
return -EINVAL;
/* make room for appending the drain */
--q->max_hw_segments;
--q->max_phys_segments;
+ q->dma_drain_needed = dma_drain_needed;
q->dma_drain_buffer = buf;
q->dma_drain_size = size;