block: rename bio bi_rw to bi_opf

Since commit 63a4cc2486, bio->bi_rw contains flags in the lower
portion and the op code in the higher portions. This means that
old code that relies on manually setting bi_rw is most likely
going to be broken. Instead of letting that brokeness linger,
rename the member, to force old and out-of-tree code to break
at compile time instead of at runtime.

No intended functional changes in this commit.

Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/md/raid10.c

@@ -1054,8 +1054,8 @@ static void __make_request(struct mddev *mddev, struct bio *bio)
 	int i;
 	const int op = bio_op(bio);
 	const int rw = bio_data_dir(bio);
-	const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
-	const unsigned long do_fua = (bio->bi_rw & REQ_FUA);
+	const unsigned long do_sync = (bio->bi_opf & REQ_SYNC);
+	const unsigned long do_fua = (bio->bi_opf & REQ_FUA);
 	unsigned long flags;
 	struct md_rdev *blocked_rdev;
 	struct blk_plug_cb *cb;
@@ -1440,7 +1440,7 @@ static void raid10_make_request(struct mddev *mddev, struct bio *bio)
 
 	struct bio *split;
 
-	if (unlikely(bio->bi_rw & REQ_PREFLUSH)) {
+	if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
 		md_flush_request(mddev, bio);
 		return;
 	}
@@ -2533,7 +2533,7 @@ read_more:
 		return;
 	}
 
-	do_sync = (r10_bio->master_bio->bi_rw & REQ_SYNC);
+	do_sync = (r10_bio->master_bio->bi_opf & REQ_SYNC);
 	slot = r10_bio->read_slot;
 	printk_ratelimited(
 		KERN_ERR