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ide-tape: use standard data transfer mechanism
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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>
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Tejun Heo committed Apr 18, 2009
1 parent 35ab8d3 commit 21d9c5d
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Showing 2 changed files with 24 additions and 94 deletions.
6 changes: 1 addition & 5 deletions drivers/ide/ide-atapi.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down
112 changes: 23 additions & 89 deletions drivers/ide/ide-tape.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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.
Expand All @@ -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,
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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
*
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -1063,32 +989,42 @@ 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;
rq->cmd[13] = cmd;
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;
}

Expand Down Expand Up @@ -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;

Expand Down

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