block: add blk_rq_aligned helper function

This adds blk_rq_aligned helper function to see if alignment and
padding requirement is satisfied for DMA transfer. This also converts
blk_rq_map_kern and __blk_rq_map_user to use the helper function.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 358ac423ed2f..9c2549260427 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -899,6 +899,13 @@ static inline int queue_dma_alignment(struct request_queue *q)
         return q ? q->dma_alignment : 511;
 }
 
+static inline int blk_rq_aligned(struct request_queue *q, void *addr,
+                                 unsigned int len)
+{
+        unsigned int alignment = queue_dma_alignment(q) | q->dma_pad_mask;
+        return !((unsigned long)addr & alignment) && !(len & alignment);
+}
+
 /* assumes size > 256 */
 static inline unsigned int blksize_bits(unsigned int size)
 {