block: rename bio bi_rw to bi_opf

Since commit 63a4cc24867d, 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>
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index dac55b2..bdf1606 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -657,7 +657,7 @@
 	struct mirror *m;
 	struct dm_io_request io_req = {
 		.bi_op = REQ_OP_WRITE,
-		.bi_op_flags = bio->bi_rw & WRITE_FLUSH_FUA,
+		.bi_op_flags = bio->bi_opf & WRITE_FLUSH_FUA,
 		.mem.type = DM_IO_BIO,
 		.mem.ptr.bio = bio,
 		.notify.fn = write_callback,
@@ -704,7 +704,7 @@
 	bio_list_init(&requeue);
 
 	while ((bio = bio_list_pop(writes))) {
-		if ((bio->bi_rw & REQ_PREFLUSH) ||
+		if ((bio->bi_opf & REQ_PREFLUSH) ||
 		    (bio_op(bio) == REQ_OP_DISCARD)) {
 			bio_list_add(&sync, bio);
 			continue;
@@ -1217,7 +1217,7 @@
 	 * If region is not in-sync queue the bio.
 	 */
 	if (!r || (r == -EWOULDBLOCK)) {
-		if (bio->bi_rw & REQ_RAHEAD)
+		if (bio->bi_opf & REQ_RAHEAD)
 			return -EWOULDBLOCK;
 
 		queue_bio(ms, bio, rw);
@@ -1253,7 +1253,7 @@
 	 * We need to dec pending if this was a write.
 	 */
 	if (rw == WRITE) {
-		if (!(bio->bi_rw & REQ_PREFLUSH) &&
+		if (!(bio->bi_opf & REQ_PREFLUSH) &&
 		    bio_op(bio) != REQ_OP_DISCARD)
 			dm_rh_dec(ms->rh, bio_record->write_region);
 		return error;
@@ -1262,7 +1262,7 @@
 	if (error == -EOPNOTSUPP)
 		goto out;
 
-	if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
+	if ((error == -EWOULDBLOCK) && (bio->bi_opf & REQ_RAHEAD))
 		goto out;
 
 	if (unlikely(error)) {