Improve static type checking by using the enum req_op type for a
function argument that represents a request operation.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220714180729.1065367-13-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
  * Process a single bvec of a bio.
  */
 static int brd_do_bvec(struct brd_device *brd, struct page *page,
-                       unsigned int len, unsigned int off, unsigned int op,
+                       unsigned int len, unsigned int off, enum req_op op,
                        sector_t sector)
 {
        void *mem;