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.c b/drivers/md/dm.c
index dfa09e1..fa9b1cb 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -798,12 +798,12 @@
 		if (io_error == DM_ENDIO_REQUEUE)
 			return;
 
-		if ((bio->bi_rw & REQ_PREFLUSH) && bio->bi_iter.bi_size) {
+		if ((bio->bi_opf & REQ_PREFLUSH) && bio->bi_iter.bi_size) {
 			/*
 			 * Preflush done for flush with data, reissue
 			 * without REQ_PREFLUSH.
 			 */
-			bio->bi_rw &= ~REQ_PREFLUSH;
+			bio->bi_opf &= ~REQ_PREFLUSH;
 			queue_io(md, bio);
 		} else {
 			/* done with normal IO or empty flush */
@@ -964,7 +964,7 @@
 {
 	struct dm_target_io *tio = container_of(bio, struct dm_target_io, clone);
 	unsigned bi_size = bio->bi_iter.bi_size >> SECTOR_SHIFT;
-	BUG_ON(bio->bi_rw & REQ_PREFLUSH);
+	BUG_ON(bio->bi_opf & REQ_PREFLUSH);
 	BUG_ON(bi_size > *tio->len_ptr);
 	BUG_ON(n_sectors > bi_size);
 	*tio->len_ptr -= bi_size - n_sectors;
@@ -1252,7 +1252,7 @@
 
 	start_io_acct(ci.io);
 
-	if (bio->bi_rw & REQ_PREFLUSH) {
+	if (bio->bi_opf & REQ_PREFLUSH) {
 		ci.bio = &ci.md->flush_bio;
 		ci.sector_count = 0;
 		error = __send_empty_flush(&ci);
@@ -1290,7 +1290,7 @@
 	if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags))) {
 		dm_put_live_table(md, srcu_idx);
 
-		if (!(bio->bi_rw & REQ_RAHEAD))
+		if (!(bio->bi_opf & REQ_RAHEAD))
 			queue_io(md, bio);
 		else
 			bio_io_error(bio);