block: split scsi_request out of struct request

And require all drivers that want to support BLOCK_PC to allocate it
as the first thing of their private data.  To support this the legacy
IDE and BSG code is switched to set cmd_size on their queues to let
the block layer allocate the additional space.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/ide/ide-tape.c

@@ -282,7 +282,7 @@ static void idetape_analyze_error(ide_drive_t *drive)
 
 	/* correct remaining bytes to transfer */
 	if (pc->flags & PC_FLAG_DMA_ERROR)
-		rq->resid_len = tape->blk_size * get_unaligned_be32(&sense[3]);
+		scsi_req(rq)->resid_len = tape->blk_size * get_unaligned_be32(&sense[3]);
 
 	/*
 	 * If error was the result of a zero-length read or write command,
@@ -316,7 +316,7 @@ static void idetape_analyze_error(ide_drive_t *drive)
 			pc->flags |= PC_FLAG_ABORT;
 		}
 		if (!(pc->flags & PC_FLAG_ABORT) &&
-		    (blk_rq_bytes(rq) - rq->resid_len))
+		    (blk_rq_bytes(rq) - scsi_req(rq)->resid_len))
 			pc->retries = IDETAPE_MAX_PC_RETRIES + 1;
 	}
 }
@@ -348,7 +348,7 @@ static int ide_tape_callback(ide_drive_t *drive, int dsc)
 					"itself - Aborting request!\n");
 	} else if (pc->c[0] == READ_6 || pc->c[0] == WRITE_6) {
 		unsigned int blocks =
-			(blk_rq_bytes(rq) - rq->resid_len) / tape->blk_size;
+			(blk_rq_bytes(rq) - scsi_req(rq)->resid_len) / tape->blk_size;
 
 		tape->avg_size += blocks * tape->blk_size;
 
@@ -560,7 +560,7 @@ static void ide_tape_create_rw_cmd(idetape_tape_t *tape,
 		pc->flags |= PC_FLAG_WRITING;
 	}
 
-	memcpy(rq->cmd, pc->c, 12);
+	memcpy(scsi_req(rq)->cmd, pc->c, 12);
 }
 
 static ide_startstop_t idetape_do_request(ide_drive_t *drive,
@@ -570,10 +570,11 @@ static ide_startstop_t idetape_do_request(ide_drive_t *drive,
 	idetape_tape_t *tape = drive->driver_data;
 	struct ide_atapi_pc *pc = NULL;
 	struct ide_cmd cmd;
+	struct scsi_request *req = scsi_req(rq);
 	u8 stat;
 
 	ide_debug_log(IDE_DBG_RQ, "cmd: 0x%x, sector: %llu, nr_sectors: %u",
-		      rq->cmd[0], (unsigned long long)blk_rq_pos(rq),
+		      req->cmd[0], (unsigned long long)blk_rq_pos(rq),
 		      blk_rq_sectors(rq));
 
 	BUG_ON(!(rq->cmd_type == REQ_TYPE_DRV_PRIV ||
@@ -592,7 +593,7 @@ static ide_startstop_t idetape_do_request(ide_drive_t *drive,
 	stat = hwif->tp_ops->read_status(hwif);
 
 	if ((drive->dev_flags & IDE_DFLAG_DSC_OVERLAP) == 0 &&
-	    (rq->cmd[13] & REQ_IDETAPE_PC2) == 0)
+	    (req->cmd[13] & REQ_IDETAPE_PC2) == 0)
 		drive->atapi_flags |= IDE_AFLAG_IGNORE_DSC;
 
 	if (drive->dev_flags & IDE_DFLAG_POST_RESET) {
@@ -609,7 +610,7 @@ static ide_startstop_t idetape_do_request(ide_drive_t *drive,
 		} else if (time_after(jiffies, tape->dsc_timeout)) {
 			printk(KERN_ERR "ide-tape: %s: DSC timeout\n",
 				tape->name);
-			if (rq->cmd[13] & REQ_IDETAPE_PC2) {
+			if (req->cmd[13] & REQ_IDETAPE_PC2) {
 				idetape_media_access_finished(drive);
 				return ide_stopped;
 			} else {
@@ -626,23 +627,23 @@ static ide_startstop_t idetape_do_request(ide_drive_t *drive,
 		tape->postponed_rq = false;
 	}
 
-	if (rq->cmd[13] & REQ_IDETAPE_READ) {
+	if (req->cmd[13] & REQ_IDETAPE_READ) {
 		pc = &tape->queued_pc;
 		ide_tape_create_rw_cmd(tape, pc, rq, READ_6);
 		goto out;
 	}
-	if (rq->cmd[13] & REQ_IDETAPE_WRITE) {
+	if (req->cmd[13] & REQ_IDETAPE_WRITE) {
 		pc = &tape->queued_pc;
 		ide_tape_create_rw_cmd(tape, pc, rq, WRITE_6);
 		goto out;
 	}
-	if (rq->cmd[13] & REQ_IDETAPE_PC1) {
+	if (req->cmd[13] & REQ_IDETAPE_PC1) {
 		pc = (struct ide_atapi_pc *)rq->special;
-		rq->cmd[13] &= ~(REQ_IDETAPE_PC1);
-		rq->cmd[13] |= REQ_IDETAPE_PC2;
+		req->cmd[13] &= ~(REQ_IDETAPE_PC1);
+		req->cmd[13] |= REQ_IDETAPE_PC2;
 		goto out;
 	}
-	if (rq->cmd[13] & REQ_IDETAPE_PC2) {
+	if (req->cmd[13] & REQ_IDETAPE_PC2) {
 		idetape_media_access_finished(drive);
 		return ide_stopped;
 	}
@@ -853,8 +854,9 @@ static int idetape_queue_rw_tail(ide_drive_t *drive, int cmd, int size)
 	BUG_ON(size < 0 || size % tape->blk_size);
 
 	rq = blk_get_request(drive->queue, READ, __GFP_RECLAIM);
+	scsi_req_init(rq);
 	rq->cmd_type = REQ_TYPE_DRV_PRIV;
-	rq->cmd[13] = cmd;
+	scsi_req(rq)->cmd[13] = cmd;
 	rq->rq_disk = tape->disk;
 	rq->__sector = tape->first_frame;
 
@@ -868,7 +870,7 @@ static int idetape_queue_rw_tail(ide_drive_t *drive, int cmd, int size)
 	blk_execute_rq(drive->queue, tape->disk, rq, 0);
 
 	/* calculate the number of transferred bytes and update buffer state */
-	size -= rq->resid_len;
+	size -= scsi_req(rq)->resid_len;
 	tape->cur = tape->buf;
 	if (cmd == REQ_IDETAPE_READ)
 		tape->valid = size;