block, dm-crypt, btrfs: Introduce bio_flags()

Introduce the bio_flags() macro. Ensure that the second argument of
bio_set_op_attrs() only contains flags and no operation. This patch
does not change any functionality.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Chris Mason <clm@fb.com> (maintainer:BTRFS FILE SYSTEM)
Cc: Josef Bacik <jbacik@fb.com> (maintainer:BTRFS FILE SYSTEM)
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Damien Le Moal <damien.lemoal@hgst.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/md/dm-crypt.c

@@ -1136,7 +1136,7 @@ static void clone_init(struct dm_crypt_io *io, struct bio *clone)
 	clone->bi_private = io;
 	clone->bi_end_io  = crypt_endio;
 	clone->bi_bdev    = cc->dev->bdev;
-	bio_set_op_attrs(clone, bio_op(io->base_bio), io->base_bio->bi_opf);
+	bio_set_op_attrs(clone, bio_op(io->base_bio), bio_flags(io->base_bio));
 }
 
 static int kcryptd_io_read(struct dm_crypt_io *io, gfp_t gfp)