block: implement blk_rq_pos/[cur_]sectors() and convert obvious ones

Implement accessors - blk_rq_pos(), blk_rq_sectors() and
blk_rq_cur_sectors() which return rq->hard_sector, rq->hard_nr_sectors
and rq->hard_cur_sectors respectively and convert direct references of
the said fields to the accessors.

This is in preparation of request data length handling cleanup.

Geert	: suggested adding const to struct request * parameter to accessors
Sergei	: spotted error in patch description

[ Impact: cleanup ]

Signed-off-by: Tejun Heo <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>
Acked-by: Stephen Rothwell <[email protected]>
Tested-by: Grant Likely <[email protected]>
Acked-by: Grant Likely <[email protected]>
Ackec-by: Sergei Shtylyov <[email protected]>
Cc: Bartlomiej Zolnierkiewicz <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: James Bottomley <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

block/blk-barrier.c

@@ -163,7 +163,7 @@ static inline bool start_ordered(struct request_queue *q, struct request **rqp)
 	 * For an empty barrier, there's no actual BAR request, which
 	 * in turn makes POSTFLUSH unnecessary.  Mask them off.
 	 */
-	if (!rq->hard_nr_sectors) {
+	if (!blk_rq_sectors(rq)) {
 		q->ordered &= ~(QUEUE_ORDERED_DO_BAR |
 				QUEUE_ORDERED_DO_POSTFLUSH);
 		/*

block/blk-core.c

@@ -1683,7 +1683,7 @@ static void blk_account_io_done(struct request *req)
 unsigned int blk_rq_bytes(struct request *rq)
 {
 	if (blk_fs_request(rq))
-		return rq->hard_nr_sectors << 9;
+		return blk_rq_sectors(rq) << 9;
 
 	return rq->data_len;
 }

block/cfq-iosched.c

@@ -760,7 +760,7 @@ static void cfq_activate_request(struct request_queue *q, struct request *rq)
 	cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
 						cfqd->rq_in_driver);
 
-	cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
+	cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
 }
 
 static void cfq_deactivate_request(struct request_queue *q, struct request *rq)