ide-tape: use standard data transfer mechanism

Impact: use standard way to transfer data

ide-tape uses rq in an interesting way.  For r/w requests, rq->special
is used to carry a private buffer management structure idetape_bh and
rq->nr_sectors and current_nr_sectors are initialized to the number of
idetape blocks which isn't necessary 512 bytes.  Also,
rq->current_nr_sectors is used to report back the residual count in
units of idetape blocks.

This peculiarity taxes both block layer and ide.  ide-atapi has
different paths and hooks to accomodate it and what a rq means becomes
quite confusing and making changes at the block layer becomes quite
difficult and error-prone.

This patch makes ide-tape use bio instead.  With the previous patch,
ide-tape currently is using single contiguos buffer so replacing it
isn't difficult.  Data buffer is mapped into bio using
blk_rq_map_kern() in idetape_queue_rw_tail().  idetape_io_buffers()
and idetape_update_buffers() are dropped and pc->bh is set to null to
tell ide-atapi to use standard data transfer mechanism and idetape_bh
byte counts are updated by the issuer on completion using the residual
count.

This change also nicely removes the FIXME in ide_pc_intr() where
ide-tape rqs need to be completed using ide_rq_bytes() instead of
blk_rq_bytes() (although this didn't really matter as the request
didn't have bio).

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 1 insertions, 5 deletions

diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c
index 3df5442de71..b9dd4503cbc 100644
--- a/drivers/ide/ide-atapi.c
+++ b/drivers/ide/ide-atapi.c
@@ -413,11 +413,7 @@ static ide_startstop_t ide_pc_intr(ide_drive_t *drive)
 		 * ->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);
+		done = blk_rq_bytes(rq);
 
 		/* Command finished - Call the callback function */
 		uptodate = drive->pc_callback(drive, dsc);