ide-atapi: don't abuse rq->buffer

Impact: rq->buffer usage cleanup

ide-atapi uses rq->buffer as private opaque value for internal special
requests.  rq->special isn't used for these cases (the only case where
rq->special is used is for ide-tape rw requests).  Use rq->special
instead.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>

drivers/ide/ide-atapi.c

@@ -90,7 +90,7 @@ static void ide_queue_pc_head(ide_drive_t *drive, struct gendisk *disk,
 	blk_rq_init(NULL, rq);
 	rq->cmd_type = REQ_TYPE_SPECIAL;
 	rq->cmd_flags |= REQ_PREEMPT;
-	rq->buffer = (char *)pc;
+	rq->special = (char *)pc;
 	rq->rq_disk = disk;
 
 	if (pc->req_xfer) {
@@ -119,7 +119,7 @@ int ide_queue_pc_tail(ide_drive_t *drive, struct gendisk *disk,
 
 	rq = blk_get_request(drive->queue, READ, __GFP_WAIT);
 	rq->cmd_type = REQ_TYPE_SPECIAL;
-	rq->buffer = (char *)pc;
+	rq->special = (char *)pc;
 
 	if (pc->req_xfer) {
 		rq->data = pc->buf;

drivers/ide/ide-floppy.c

@@ -264,7 +264,7 @@ static ide_startstop_t ide_floppy_do_request(ide_drive_t *drive,
 		pc = &floppy->queued_pc;
 		idefloppy_create_rw_cmd(drive, pc, rq, (unsigned long)block);
 	} else if (blk_special_request(rq)) {
-		pc = (struct ide_atapi_pc *) rq->buffer;
+		pc = (struct ide_atapi_pc *)rq->special;
 	} else if (blk_pc_request(rq)) {
 		pc = &floppy->queued_pc;
 		idefloppy_blockpc_cmd(floppy, pc, rq);

drivers/ide/ide-tape.c

@@ -828,7 +828,7 @@ static ide_startstop_t idetape_do_request(ide_drive_t *drive,
 		goto out;
 	}
 	if (rq->cmd[13] & REQ_IDETAPE_PC1) {
-		pc = (struct ide_atapi_pc *) rq->buffer;
+		pc = (struct ide_atapi_pc *)rq->special;
 		rq->cmd[13] &= ~(REQ_IDETAPE_PC1);
 		rq->cmd[13] |= REQ_IDETAPE_PC2;
 		goto out;