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>

2 files changed, 24 insertions, 94 deletions

diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c
index 3df5442de710..b9dd4503cbc7 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);
diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index b2afbc7bcb6b..b373ac876352 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -292,65 +292,6 @@ static struct ide_tape_obj *ide_tape_chrdev_get(unsigned int i)
         return tape;
 }
 
-static int idetape_input_buffers(ide_drive_t *drive, struct ide_atapi_pc *pc,
-                                  unsigned int bcount)
-{
-        struct idetape_bh *bh = pc->bh;
-        int count;
-
-        if (bcount && bh) {
-                count = min(
-                        (unsigned int)(bh->b_size - atomic_read(&bh->b_count)),
-                        bcount);
-                drive->hwif->tp_ops->input_data(drive, NULL, bh->b_data +
-                                        atomic_read(&bh->b_count), count);
-                bcount -= count;
-                atomic_add(count, &bh->b_count);
-                if (atomic_read(&bh->b_count) == bh->b_size)
-                        pc->bh = NULL;
-        }
-
-        return bcount;
-}
-
-static int idetape_output_buffers(ide_drive_t *drive, struct ide_atapi_pc *pc,
-                                   unsigned int bcount)
-{
-        struct idetape_bh *bh = pc->bh;
-        int count;
-
-        if (bcount && bh) {
-                count = min((unsigned int)pc->b_count, (unsigned int)bcount);
-                drive->hwif->tp_ops->output_data(drive, NULL, pc->b_data, count);
-                bcount -= count;
-                pc->b_data += count;
-                pc->b_count -= count;
-                if (!pc->b_count)
-                        pc->bh = NULL;
-        }
-
-        return bcount;
-}
-
-static void idetape_update_buffers(ide_drive_t *drive, struct ide_atapi_pc *pc)
-{
-        struct idetape_bh *bh = pc->bh;
-        unsigned int bcount = pc->xferred;
-
-        if (pc->flags & PC_FLAG_WRITING)
-                return;
-        if (bcount) {
-                if (bh == NULL || bcount > bh->b_size) {
-                        printk(KERN_ERR "ide-tape: bh == NULL in %s\n",
-                                        __func__);
-                        return;
-                }
-                atomic_set(&bh->b_count, bcount);
-                if (atomic_read(&bh->b_count) == bh->b_size)
-                        pc->bh = NULL;
-        }
-}
-
 /*
  * called on each failed packet command retry to analyze the request sense. We
  * currently do not utilize this information.
@@ -368,12 +309,10 @@ static void idetape_analyze_error(ide_drive_t *drive, u8 *sense)
                  pc->c[0], tape->sense_key, tape->asc, tape->ascq);
 
         /* Correct pc->xferred by asking the tape.       */
-        if (pc->flags & PC_FLAG_DMA_ERROR) {
+        if (pc->flags & PC_FLAG_DMA_ERROR)
                 pc->xferred = pc->req_xfer -
                         tape->blk_size *
                         get_unaligned_be32(&sense[3]);
-                idetape_update_buffers(drive, pc);
-        }
 
         /*
          * If error was the result of a zero-length read or write command,
@@ -458,7 +397,7 @@ static int ide_tape_callback(ide_drive_t *drive, int dsc)
                 }
 
                 tape->first_frame += blocks;
-                rq->current_nr_sectors -= blocks;
+                rq->data_len -= blocks * tape->blk_size;
 
                 if (pc->error) {
                         uptodate = 0;
@@ -520,19 +459,6 @@ static void ide_tape_handle_dsc(ide_drive_t *drive)
         idetape_postpone_request(drive);
 }
 
-static int ide_tape_io_buffers(ide_drive_t *drive, struct ide_atapi_pc *pc,
-                                unsigned int bcount, int write)
-{
-        unsigned int bleft;
-
-        if (write)
-                bleft = idetape_output_buffers(drive, pc, bcount);
-        else
-                bleft = idetape_input_buffers(drive, pc, bcount);
-
-        return bcount - bleft;
-}
-
 /*
  * Packet Command Interface
  *
@@ -683,7 +609,7 @@ static void ide_tape_create_rw_cmd(idetape_tape_t *tape,
         ide_init_pc(pc);
         put_unaligned(cpu_to_be32(length), (unsigned int *) &pc->c[1]);
         pc->c[1] = 1;
-        pc->bh = bh;
+        pc->bh = NULL;
         pc->buf = NULL;
         pc->buf_size = length * tape->blk_size;
         pc->req_xfer = pc->buf_size;
@@ -1063,10 +989,12 @@ static int idetape_queue_rw_tail(ide_drive_t *drive, int cmd, int blocks,
                                  struct idetape_bh *bh)
 {
         idetape_tape_t *tape = drive->driver_data;
+        size_t size = blocks * tape->blk_size;
         struct request *rq;
-        int ret, errors;
+        int ret;
 
         debug_log(DBG_SENSE, "%s: cmd=%d\n", __func__, cmd);
+        BUG_ON(cmd != REQ_IDETAPE_READ && cmd != REQ_IDETAPE_WRITE);
 
         rq = blk_get_request(drive->queue, READ, __GFP_WAIT);
         rq->cmd_type = REQ_TYPE_SPECIAL;
@@ -1074,21 +1002,29 @@ static int idetape_queue_rw_tail(ide_drive_t *drive, int cmd, int blocks,
         rq->rq_disk = tape->disk;
         rq->special = (void *)bh;
         rq->sector = tape->first_frame;
-        rq->nr_sectors = blocks;
-        rq->current_nr_sectors = blocks;
+
+        if (size) {
+                ret = blk_rq_map_kern(drive->queue, rq, bh->b_data, size,
+                                      __GFP_WAIT);
+                if (ret)
+                        goto out_put;
+        }
+
         blk_execute_rq(drive->queue, tape->disk, rq, 0);
 
-        errors = rq->errors;
-        ret = tape->blk_size * (blocks - rq->current_nr_sectors);
-        blk_put_request(rq);
+        /* calculate the number of transferred bytes and update bh */
+        size -= rq->data_len;
+        if (cmd == REQ_IDETAPE_READ)
+                atomic_add(size, &bh->b_count);
 
-        if ((cmd & (REQ_IDETAPE_READ | REQ_IDETAPE_WRITE)) == 0)
-                return 0;
+        ret = size;
+        if (rq->errors == IDE_DRV_ERROR_GENERAL)
+                ret = -EIO;
 
         if (tape->merge_bh)
                 idetape_init_merge_buffer(tape);
-        if (errors == IDE_DRV_ERROR_GENERAL)
-                return -EIO;
+out_put:
+        blk_put_request(rq);
         return ret;
 }
 
@@ -2034,8 +1970,6 @@ static void idetape_setup(ide_drive_t *drive, idetape_tape_t *tape, int minor)
         u16 *ctl = (u16 *)&tape->caps[12];
 
         drive->pc_callback       = ide_tape_callback;
-        drive->pc_update_buffers = idetape_update_buffers;
-        drive->pc_io_buffers     = ide_tape_io_buffers;
 
         drive->dev_flags |= IDE_DFLAG_DSC_OVERLAP;