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>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/ide/ide-floppy.c b/drivers/ide/ide-floppy.c
index d20704ac318..537b7c55803 100644
--- a/drivers/ide/ide-floppy.c
+++ b/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;
 	}