ide-atapi,tape,floppy: allow ->pc_callback() to change rq->data_len

Impact: allow residual count implementation in ->pc_callback()

rq->data_len has two duties - carrying the number of input bytes on
issue and carrying residual count back to the issuer on completion.
ide-atapi completion callback ->pc_callback() is the right place to do
this but currently ide-atapi depends on rq->data_len carrying the
original request size after calling ->pc_callback() to complete the pc
request.

This patch makes ide_pc_intr(), ide_tape_issue_pc() and
ide_floppy_issue_pc() cache length to complete before calling
->pc_callback() so that it can modify rq->data_len as necessary.

Note: As using rq->data_len for two purposes can make cases like this
      incorrect in subtle ways, future changes will introduce separate
      field for residual count.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <jens.axboe@oracle.com>

drivers/ide/ide-atapi.c

@@ -409,6 +409,16 @@ static ide_startstop_t ide_pc_intr(ide_drive_t *drive)
 		if ((pc->flags & PC_FLAG_WAIT_FOR_DSC) && (stat & ATA_DSC) == 0)
 			dsc = 1;
 
+		/*
+		 * ->pc_callback() might change rq->data_len for
+		 * residual count, cache total length.
+		 */
+		if (!blk_special_request(rq) &&
+		    (drive->media == ide_tape && !rq->bio))
+			done = ide_rq_bytes(rq);        /* FIXME */
+		else
+			done = blk_rq_bytes(rq);
+
 		/* Command finished - Call the callback function */
 		uptodate = drive->pc_callback(drive, dsc);
 
@@ -417,7 +427,6 @@ static ide_startstop_t ide_pc_intr(ide_drive_t *drive)
 
 		if (blk_special_request(rq)) {
 			rq->errors = 0;
-			done = blk_rq_bytes(rq);
 			error = 0;
 		} else {
 
@@ -426,11 +435,6 @@ static ide_startstop_t ide_pc_intr(ide_drive_t *drive)
 					rq->errors = -EIO;
 			}
 
-			if (drive->media == ide_tape && !rq->bio)
-				done = ide_rq_bytes(rq); /* FIXME */
-			else
-				done = blk_rq_bytes(rq);
-
 			error = uptodate ? 0 : -EIO;
 		}
 

drivers/ide/ide-floppy.c

@@ -134,14 +134,17 @@ static ide_startstop_t ide_floppy_issue_pc(ide_drive_t *drive,
 	drive->pc = pc;
 
 	if (pc->retries > IDEFLOPPY_MAX_PC_RETRIES) {
+		unsigned int done = blk_rq_bytes(drive->hwif->rq);
+
 		if (!(pc->flags & PC_FLAG_SUPPRESS_ERROR))
 			ide_floppy_report_error(floppy, pc);
+
 		/* Giving up */
 		pc->error = IDE_DRV_ERROR_GENERAL;
 
 		drive->failed_pc = NULL;
 		drive->pc_callback(drive, 0);
-		ide_complete_rq(drive, -EIO, blk_rq_bytes(drive->hwif->rq));
+		ide_complete_rq(drive, -EIO, done);
 		return ide_stopped;
 	}
 

drivers/ide/ide-tape.c

@@ -622,6 +622,8 @@ 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
 		 * error code was received (crossing a filemark, or end of the
@@ -641,9 +643,10 @@ static ide_startstop_t ide_tape_issue_pc(ide_drive_t *drive,
 			/* Giving up */
 			pc->error = IDE_DRV_ERROR_GENERAL;
 		}
+
 		drive->failed_pc = NULL;
 		drive->pc_callback(drive, 0);
-		ide_complete_rq(drive, -EIO, blk_rq_bytes(drive->hwif->rq));
+		ide_complete_rq(drive, -EIO, done);
 		return ide_stopped;
 	}
 	debug_log(DBG_SENSE, "Retry #%d, cmd = %02X\n", pc->retries, pc->c[0]);