block: get rid of bio_rw and READA

These two are confusing leftover of the old world order, combining
values of the REQ_OP_ and REQ_ namespaces.  For callers that don't
special case we mostly just replace bi_rw with bio_data_dir or
op_is_write, except for the few cases where a switch over the REQ_OP_
values makes more sense.  Any check for READA is replaced with an
explicit check for REQ_RAHEAD.  Also remove the READA alias for
REQ_RAHEAD.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1830245..dc48866 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -178,9 +178,6 @@
  * READ_SYNC		A synchronous read. Device is not plugged, caller can
  *			immediately wait on this read without caring about
  *			unplugging.
- * READA		Used for read-ahead operations. Lower priority, and the
- *			block layer could (in theory) choose to ignore this
- *			request if it runs into resource problems.
  * WRITE		A normal async write. Device will be plugged.
  * WRITE_SYNC		Synchronous write. Identical to WRITE, but passes down
  *			the hint that someone will be waiting on this IO
@@ -195,11 +192,9 @@
  *
  */
 #define RW_MASK			REQ_OP_WRITE
-#define RWA_MASK		REQ_RAHEAD
 
 #define READ			REQ_OP_READ
-#define WRITE			RW_MASK
-#define READA			RWA_MASK
+#define WRITE			REQ_OP_WRITE
 
 #define READ_SYNC		REQ_SYNC
 #define WRITE_SYNC		(REQ_SYNC | REQ_NOIDLE)
@@ -2471,17 +2466,6 @@
 }
 
 /*
- * return READ, READA, or WRITE
- */
-static inline int bio_rw(struct bio *bio)
-{
-	if (op_is_write(bio_op(bio)))
-		return WRITE;
-
-	return bio->bi_rw & RWA_MASK;
-}
-
-/*
  * return data direction, READ or WRITE
  */
 static inline int bio_data_dir(struct bio *bio)