direct-io: use bio set/get op accessors

This patch has the dio code use a REQ_OP for the op and rq_flag_bits
for bi_rw flags. To set/get the op it uses the bio_set_op_attrs/bio_op
accssors.

It also begins to convert btrfs's dio_submit_t because of the dio
submit_io callout use. The next patches will completely convert
this code and the reset of the btrfs code paths.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 8b1212e..348ad81 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8433,14 +8433,14 @@
 	return 0;
 }
 
-static void btrfs_submit_direct(int rw, struct bio *dio_bio,
-				struct inode *inode, loff_t file_offset)
+static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
+				loff_t file_offset)
 {
 	struct btrfs_dio_private *dip = NULL;
 	struct bio *io_bio = NULL;
 	struct btrfs_io_bio *btrfs_bio;
 	int skip_sum;
-	int write = rw & REQ_WRITE;
+	bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
 	int ret = 0;
 
 	skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
@@ -8491,7 +8491,7 @@
 			dio_data->unsubmitted_oe_range_end;
 	}
 
-	ret = btrfs_submit_direct_hook(rw, dip, skip_sum);
+	ret = btrfs_submit_direct_hook(dio_bio->bi_rw, dip, skip_sum);
 	if (!ret)
 		return;