ide-atapi: switch to blk_rq_bytes() on do_request() path

After the recent struct request cleanups, blk_rq_bytes() is guaranteed
to be valid and is the current total length of the rq's bio. Use that
instead of pc->req_xfer in the do_request() path after the command has
been queued

The remaining usage of pc->req_xfer now is only until we map the rq to a
bio.

While at it:

- remove local caching of rq completion length in ide_tape_issue_pc()

Signed-off-by: Borislav Petkov <petkovbb@gmail.com>

drivers/ide/ide-tape.c

@@ -292,6 +292,7 @@ static void idetape_analyze_error(ide_drive_t *drive, u8 *sense)
 {
 	idetape_tape_t *tape = drive->driver_data;
 	struct ide_atapi_pc *pc = drive->failed_pc;
+	struct request *rq = drive->hwif->rq;
 
 	tape->sense_key = sense[2] & 0xF;
 	tape->asc       = sense[12];
@@ -302,7 +303,7 @@ static void idetape_analyze_error(ide_drive_t *drive, u8 *sense)
 
 	/* Correct pc->xferred by asking the tape.	 */
 	if (pc->flags & PC_FLAG_DMA_ERROR)
-		pc->xferred = pc->req_xfer -
+		pc->xferred = blk_rq_bytes(rq) -
 			tape->blk_size *
 			get_unaligned_be32(&sense[3]);
 
@@ -484,6 +485,7 @@ static ide_startstop_t ide_tape_issue_pc(ide_drive_t *drive,
 					 struct ide_atapi_pc *pc)
 {
 	idetape_tape_t *tape = drive->driver_data;
+	struct request *rq = drive->hwif->rq;
 
 	if (drive->failed_pc == NULL && pc->c[0] != REQUEST_SENSE)
 		drive->failed_pc = pc;
@@ -493,7 +495,6 @@ static ide_startstop_t ide_tape_issue_pc(ide_drive_t *drive,
 
 	if (pc->retries > IDETAPE_MAX_PC_RETRIES ||
 		(pc->flags & PC_FLAG_ABORT)) {
-		unsigned int done = blk_rq_bytes(drive->hwif->rq);
 
 		/*
 		 * We will "abort" retrying a packet command in case legitimate
@@ -517,7 +518,7 @@ static ide_startstop_t ide_tape_issue_pc(ide_drive_t *drive,
 
 		drive->failed_pc = NULL;
 		drive->pc_callback(drive, 0);
-		ide_complete_rq(drive, -EIO, done);
+		ide_complete_rq(drive, -EIO, blk_rq_bytes(rq));
 		return ide_stopped;
 	}
 	debug_log(DBG_SENSE, "Retry #%d, cmd = %02X\n", pc->retries, pc->c[0]);
@@ -592,9 +593,8 @@ static void ide_tape_create_rw_cmd(idetape_tape_t *tape,
 	put_unaligned(cpu_to_be32(length), (unsigned int *) &pc->c[1]);
 	pc->c[1] = 1;
 	pc->buf = NULL;
-	pc->buf_size = length * tape->blk_size;
-	pc->req_xfer = pc->buf_size;
-	if (pc->req_xfer == tape->buffer_size)
+	pc->buf_size = blk_rq_bytes(rq);
+	if (pc->buf_size == tape->buffer_size)
 		pc->flags |= PC_FLAG_DMA_OK;
 
 	if (opcode == READ_6)
@@ -718,7 +718,7 @@ out:
 
 	cmd.rq = rq;
 
-	ide_init_sg_cmd(&cmd, pc->req_xfer);
+	ide_init_sg_cmd(&cmd, blk_rq_bytes(rq));
 	ide_map_sg(drive, &cmd);
 
 	return ide_tape_issue_pc(drive, &cmd, pc);