[PATCH 00/24] ide-tape: remove pipelined mode operation

@@ -206,19 +206,15 @@ enum {
 	/* 0 When the tape position is unknown */
 	IDETAPE_FLAG_ADDRESS_VALID	= (1 <<	1),
 	/* Device already opened */
-	IDETAPE_FLAG_BUSY			= (1 << 2),
-	/* Error detected in a pipeline stage */
-	IDETAPE_FLAG_PIPELINE_ERR	= (1 <<	3),
+	IDETAPE_FLAG_BUSY		= (1 << 2),
 	/* Attempt to auto-detect the current user block size */
-	IDETAPE_FLAG_DETECT_BS		= (1 << 4),
+	IDETAPE_FLAG_DETECT_BS		= (1 << 3),
 	/* Currently on a filemark */
-	IDETAPE_FLAG_FILEMARK		= (1 << 5),
+	IDETAPE_FLAG_FILEMARK		= (1 << 4),
 	/* DRQ interrupt device */
-	IDETAPE_FLAG_DRQ_INTERRUPT	= (1 << 6),
-	/* pipeline active */
-	IDETAPE_FLAG_PIPELINE_ACTIVE	= (1 << 7),
+	IDETAPE_FLAG_DRQ_INTERRUPT	= (1 << 5),
 	/* 0 = no tape is loaded, so we don't rewind after ejecting */
-	IDETAPE_FLAG_MEDIUM_PRESENT	= (1 << 8),
+	IDETAPE_FLAG_MEDIUM_PRESENT	= (1 << 6),
 };
 
 /* A pipeline stage. */

@@ -1973,52 +1973,6 @@ static int idetape_create_prevent_cmd(ide_drive_t *drive,
 	return 1;
 }
 
-static int __idetape_discard_read_pipeline(ide_drive_t *drive)
-{
-	idetape_tape_t *tape = drive->driver_data;
-	unsigned long flags;
-	int cnt;
-
-	if (tape->chrdev_dir != IDETAPE_DIR_READ)
-		return 0;
-
-	/* Remove merge stage. */
-	cnt = tape->merge_stage_size / tape->blk_size;
-	if (test_and_clear_bit(IDETAPE_FLAG_FILEMARK, &tape->flags))
-		++cnt;		/* Filemarks count as 1 sector */
-	tape->merge_stage_size = 0;
-	if (tape->merge_stage != NULL) {
-		__idetape_kfree_stage(tape->merge_stage);
-		tape->merge_stage = NULL;
-	}
-
-	/* Clear pipeline flags. */
-	clear_bit(IDETAPE_FLAG_PIPELINE_ERR, &tape->flags);
-	tape->chrdev_dir = IDETAPE_DIR_NONE;
-
-	/* Remove pipeline stages. */
-	if (tape->first_stage == NULL)
-		return 0;
-
-	spin_lock_irqsave(&tape->lock, flags);
-	tape->next_stage = NULL;
-	if (test_bit(IDETAPE_FLAG_PIPELINE_ACTIVE, &tape->flags))
-		idetape_wait_for_request(drive, tape->active_data_rq);
-	spin_unlock_irqrestore(&tape->lock, flags);
-
-	while (tape->first_stage != NULL) {
-		struct request *rq_ptr = &tape->first_stage->rq;
-
-		cnt += rq_ptr->nr_sectors - rq_ptr->current_nr_sectors;
-		if (rq_ptr->errors == IDETAPE_ERROR_FILEMARK)
-			++cnt;
-		idetape_remove_stage_head(drive);
-	}
-	tape->nr_pending_stages = 0;
-	tape->max_stages = tape->min_pipeline;
-	return cnt;
-}
-
 /*
  * Position the tape to the requested block using the LOCATE packet command.
  * A READ POSITION command is then issued to check where we are positioned. Like

@@ -2028,12 +1982,9 @@ static int __idetape_discard_read_pipeline(ide_drive_t *drive)
 static int idetape_position_tape(ide_drive_t *drive, unsigned int block,
 		u8 partition, int skip)
 {
-	idetape_tape_t *tape = drive->driver_data;
 	int retval;
 	struct ide_atapi_pc pc;
 
-	if (tape->chrdev_dir == IDETAPE_DIR_READ)
-		__idetape_discard_read_pipeline(drive);
 	idetape_wait_ready(drive, 60 * 5 * HZ);
 	idetape_create_locate_cmd(drive, &pc, block, partition, skip);
 	retval = idetape_queue_pc_tail(drive, &pc);

@@ -2143,19 +2143,6 @@ static void idetape_create_space_cmd(struct ide_atapi_pc *pc, int count, u8 cmd)
 	pc->idetape_callback = &idetape_pc_callback;
 }
 
-static void idetape_wait_first_stage(ide_drive_t *drive)
-{
-	idetape_tape_t *tape = drive->driver_data;
-	unsigned long flags;
-
-	if (tape->first_stage == NULL)
-		return;
-	spin_lock_irqsave(&tape->lock, flags);
-	if (tape->active_stage == tape->first_stage)
-		idetape_wait_for_request(drive, tape->active_data_rq);
-	spin_unlock_irqrestore(&tape->lock, flags);
-}
-
 /* Queue up a character device originated write request. */
 static int idetape_add_chrdev_write_request(ide_drive_t *drive, int blocks)
 {

@@ -2446,73 +2433,23 @@ static int idetape_blkdev_ioctl(ide_drive_t *drive, unsigned int cmd,
 	return 0;
 }
 
-/*
- * The function below is now a bit more complicated than just passing the
- * command to the tape since we may have crossed some filemarks during our
- * pipelined read-ahead mode. As a minor side effect, the pipeline enables us to
- * support MTFSFM when the filemark is in our internal pipeline even if the tape
- * doesn't support spacing over filemarks in the reverse direction.
- */
 static int idetape_space_over_filemarks(ide_drive_t *drive, short mt_op,
 					int mt_count)
 {
 	idetape_tape_t *tape = drive->driver_data;
 	struct ide_atapi_pc pc;
-	unsigned long flags;
 	int retval, count = 0;
 	int sprev = !!(tape->caps[4] & 0x20);
 
 	if (mt_count == 0)
 		return 0;
+
 	if (MTBSF == mt_op || MTBSFM == mt_op) {
 		if (!sprev)
 			return -EIO;
 		mt_count = -mt_count;
 	}
 
-	if (tape->chrdev_dir == IDETAPE_DIR_READ) {
-		/* its a read-ahead buffer, scan it for crossed filemarks. */
-		tape->merge_stage_size = 0;
-		if (test_and_clear_bit(IDETAPE_FLAG_FILEMARK, &tape->flags))
-			++count;
-		while (tape->first_stage != NULL) {
-			if (count == mt_count) {
-				if (mt_op == MTFSFM)
-					set_bit(IDETAPE_FLAG_FILEMARK,
-						&tape->flags);
-				return 0;
-			}
-			spin_lock_irqsave(&tape->lock, flags);
-			if (tape->first_stage == tape->active_stage) {
-				/*
-				 * We have reached the active stage in the read
-				 * pipeline. There is no point in allowing the
-				 * drive to continue reading any farther, so we
-				 * stop the pipeline.
-				 *
-				 * This section should be moved to a separate
-				 * subroutine because similar operations are
-				 * done in __idetape_discard_read_pipeline(),
-				 * for example.
-				 */
-				tape->next_stage = NULL;
-				spin_unlock_irqrestore(&tape->lock, flags);
-				idetape_wait_first_stage(drive);
-				tape->next_stage = tape->first_stage->next;
-			} else
-				spin_unlock_irqrestore(&tape->lock, flags);
-			if (tape->first_stage->rq.errors ==
-					IDETAPE_ERROR_FILEMARK)
-				++count;
-			idetape_remove_stage_head(drive);
-		}
-		idetape_discard_read_pipeline(drive, 0);
-	}
-
-	/*
-	 * The filemark was not found in our internal pipeline;	now we can issue
-	 * the space command.
-	 */
 	switch (mt_op) {
 	case MTFSF:
 	case MTBSF:

@@ -2123,12 +2123,6 @@ static int idetape_queue_rw_tail(ide_drive_t *drive, int cmd, int blocks,
 
 	debug_log(DBG_SENSE, "%s: cmd=%d\n", __func__, cmd);
 
-	if (test_bit(IDETAPE_FLAG_PIPELINE_ACTIVE, &tape->flags)) {
-		printk(KERN_ERR "ide-tape: bug: the pipeline is active in %s\n",
-				__func__);
-		return (0);
-	}
-
 	idetape_init_rq(&rq, cmd);
 	rq.rq_disk = tape->disk;
 	rq.special = (void *)bh;

@@ -2140,10 +2134,9 @@ static int idetape_queue_rw_tail(ide_drive_t *drive, int cmd, int blocks,
 	if ((cmd & (REQ_IDETAPE_READ | REQ_IDETAPE_WRITE)) == 0)
 		return 0;
 
-	if (tape->merge_stage)
-		idetape_init_merge_stage(tape);
 	if (rq.errors == IDETAPE_ERROR_GENERAL)
 		return -EIO;
+
 	return (tape->blk_size * (blocks-rq.current_nr_sectors));
 }
 

@@ -2210,81 +2203,15 @@ static void idetape_wait_first_stage(ide_drive_t *drive)
 	spin_unlock_irqrestore(&tape->lock, flags);
 }
 
-/*
- * Try to add a character device originated write request to our pipeline. In
- * case we don't succeed, we revert to non-pipelined operation mode for this
- * request. In order to accomplish that, we
- *
- * 1. Try to allocate a new pipeline stage.
- * 2. If we can't, wait for more and more requests to be serviced and try again
- * each time.
- * 3. If we still can't allocate a stage, fallback to non-pipelined operation
- * mode for this request.
- */
+/* Queue up a character device originated write request. */
 static int idetape_add_chrdev_write_request(ide_drive_t *drive, int blocks)
 {
 	idetape_tape_t *tape = drive->driver_data;
-	idetape_stage_t *new_stage;
-	unsigned long flags;
-	struct request *rq;
 
 	debug_log(DBG_CHRDEV, "Enter %s\n", __func__);
 
-	/* Attempt to allocate a new stage. Beware possible race conditions. */
-	while ((new_stage = idetape_kmalloc_stage(tape)) == NULL) {
-		spin_lock_irqsave(&tape->lock, flags);
-		if (test_bit(IDETAPE_FLAG_PIPELINE_ACTIVE, &tape->flags)) {
-			idetape_wait_for_request(drive, tape->active_data_rq);
-			spin_unlock_irqrestore(&tape->lock, flags);
-		} else {
-			spin_unlock_irqrestore(&tape->lock, flags);
-			idetape_plug_pipeline(drive);
-			if (test_bit(IDETAPE_FLAG_PIPELINE_ACTIVE,
-					&tape->flags))
-				continue;
-			/*
-			 * The machine is short on memory. Fallback to non-
-			 * pipelined operation mode for this request.
-			 */
-			return idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE,
-						blocks, tape->merge_stage->bh);
-		}
-	}
-	rq = &new_stage->rq;
-	idetape_init_rq(rq, REQ_IDETAPE_WRITE);
-	/* Doesn't actually matter - We always assume sequential access */
-	rq->sector = tape->first_frame;
-	rq->current_nr_sectors = blocks;
-	rq->nr_sectors = blocks;
-
-	idetape_switch_buffers(tape, new_stage);
-	idetape_add_stage_tail(drive, new_stage);
-	tape->pipeline_head++;
-	idetape_calculate_speeds(drive);
-
-	/*
-	 * Estimate whether the tape has stopped writing by checking if our
-	 * write pipeline is currently empty. If we are not writing anymore,
-	 * wait for the pipeline to be almost completely full (90%) before
-	 * starting to service requests, so that we will be able to keep up with
-	 * the higher speeds of the tape.
-	 */
-	if (!test_bit(IDETAPE_FLAG_PIPELINE_ACTIVE, &tape->flags)) {
-		if (tape->nr_stages >= tape->max_stages * 9 / 10 ||
-			tape->nr_stages >= tape->max_stages -
-			tape->uncontrolled_pipeline_head_speed * 3 * 1024 /
-			tape->blk_size) {
-			tape->measure_insert_time = 1;
-			tape->insert_time = jiffies;
-			tape->insert_size = 0;
-			tape->insert_speed = 0;
-			idetape_plug_pipeline(drive);
-		}
-	}
-	if (test_and_clear_bit(IDETAPE_FLAG_PIPELINE_ERR, &tape->flags))
-		/* Return a deferred error */
-		return -EIO;
-	return blocks;
+	return idetape_queue_rw_tail(drive, REQ_IDETAPE_WRITE, blocks,
+					tape->merge_stage->bh);
 }
 
 /*

@@ -8,8 +8,6 @@
  * interface, on the other hand, creates new requests, adds them
  * to the request-list of the block device, and waits for their completion.
  *
- * Pipelined operation mode is now supported on both reads and writes.
- *
  * The block device major and minor numbers are determined from the
  * tape's relative position in the ide interfaces, as explained in ide.c.
  *

@@ -45,83 +43,6 @@
  *
  * | Special care is recommended.  Have Fun!
  *
- *
- * An overview of the pipelined operation mode.
- *
- * In the pipelined write mode, we will usually just add requests to our
- * pipeline and return immediately, before we even start to service them. The
- * user program will then have enough time to prepare the next request while
- * we are still busy servicing previous requests. In the pipelined read mode,
- * the situation is similar - we add read-ahead requests into the pipeline,
- * before the user even requested them.
- *
- * The pipeline can be viewed as a "safety net" which will be activated when
- * the system load is high and prevents the user backup program from keeping up
- * with the current tape speed. At this point, the pipeline will get
- * shorter and shorter but the tape will still be streaming at the same speed.
- * Assuming we have enough pipeline stages, the system load will hopefully
- * decrease before the pipeline is completely empty, and the backup program
- * will be able to "catch up" and refill the pipeline again.
- *
- * When using the pipelined mode, it would be best to disable any type of
- * buffering done by the user program, as ide-tape already provides all the
- * benefits in the kernel, where it can be done in a more efficient way.
- * As we will usually not block the user program on a request, the most
- * efficient user code will then be a simple read-write-read-... cycle.
- * Any additional logic will usually just slow down the backup process.
- *
- * Using the pipelined mode, I get a constant over 400 KBps throughput,
- * which seems to be the maximum throughput supported by my tape.
- *
- * However, there are some downfalls:
- *
- *	1.	We use memory (for data buffers) in proportional to the number
- *		of pipeline stages (each stage is about 26 KB with my tape).
- *	2.	In the pipelined write mode, we cheat and postpone error codes
- *		to the user task. In read mode, the actual tape position
- *		will be a bit further than the last requested block.
- *
- * Concerning (1):
- *
- *	1.	We allocate stages dynamically only when we need them. When
- *		we don't need them, we don't consume additional memory. In
- *		case we can't allocate stages, we just manage without them
- *		(at the expense of decreased throughput) so when Linux is
- *		tight in memory, we will not pose additional difficulties.
- *
- *	2.	The maximum number of stages (which is, in fact, the maximum
- *		amount of memory) which we allocate is limited by the compile
- *		time parameter IDETAPE_MAX_PIPELINE_STAGES.
- *
- *	3.	The maximum number of stages is a controlled parameter - We
- *		don't start from the user defined maximum number of stages
- *		but from the lower IDETAPE_MIN_PIPELINE_STAGES (again, we
- *		will not even allocate this amount of stages if the user
- *		program can't handle the speed). We then implement a feedback
- *		loop which checks if the pipeline is empty, and if it is, we
- *		increase the maximum number of stages as necessary until we
- *		reach the optimum value which just manages to keep the tape
- *		busy with minimum allocated memory or until we reach
- *		IDETAPE_MAX_PIPELINE_STAGES.
- *
- * Concerning (2):
- *
- *	In pipelined write mode, ide-tape can not return accurate error codes
- *	to the user program since we usually just add the request to the
- *      pipeline without waiting for it to be serviced. In case an error
- *      occurs, I will report it on the next user request.
- *
- *	In the pipelined read mode, subsequent read requests or forward
- *	filemark spacing will perform correctly, as we preserve all blocks
- *	and filemarks which we encountered during our excess read-ahead.
- *
- *	For accurate tape positioning and error reporting, disabling
- *	pipelined mode might be the best option.
- *
- * You can enable/disable/tune the pipelined operation mode by adjusting
- * the compile time parameters below.
- *
- *
  *	Possible improvements.
  *
  *	1.	Support for the ATAPI overlap protocol.

@@ -267,9 +267,7 @@ typedef struct ide_tape_obj {
 	 * While polling for DSC we use postponed_rq to postpone the current
 	 * request so that ide.c will be able to service pending requests on the
 	 * other device. Note that at most we will have only one DSC (usually
-	 * data transfer) request in the device request queue. Additional
-	 * requests can be queued in our internal pipeline, but they will be
-	 * visible to ide.c only one at a time.
+	 * data transfer) request in the device request queue.
 	 */
 	struct request *postponed_rq;
 	/* The time in which we started polling for DSC */

@@ -309,10 +307,8 @@ typedef struct ide_tape_obj {
 	 * At most, there is only one ide-tape originated data transfer request
 	 * in the device request queue. This allows ide.c to easily service
 	 * requests from the other device when we postpone our active request.
-	 * In the pipelined operation mode, we use our internal pipeline
-	 * structure to hold more data requests. The data buffer size is chosen
-	 * based on the tape's recommendation.
 	 */
+
 	/* ptr to the request which is waiting in the device request queue */
 	struct request *active_data_rq;
 	/* Data buffer size chosen based on the tape's recommendation */

@@ -1792,8 +1788,7 @@ static int idetape_init_read(ide_drive_t *drive)
 }
 
 /*
- * Called from idetape_chrdev_read() to service a character device read request
- * and add read-ahead requests to our pipeline.
+ * Called from idetape_chrdev_read() to service a character device read request.
  */
 static int idetape_add_chrdev_read_request(ide_drive_t *drive, int blocks)
 {

@@ -2112,8 +2107,7 @@ static int idetape_write_filemark(ide_drive_t *drive)
  *
  * Note: MTBSF and MTBSFM are not supported when the tape doesn't support
  * spacing over filemarks in the reverse direction. In this case, MTFSFM is also
- * usually not supported (it is supported in the rare case in which we crossed
- * the filemark during our read-ahead pipelined operation mode).
+ * usually not supported.
  *
  * The following commands are currently not supported:
  *

@@ -2129,7 +2123,6 @@ static int idetape_mtioctop(ide_drive_t *drive, short mt_op, int mt_count)
 	debug_log(DBG_ERR, "Handling MTIOCTOP ioctl: mt_op=%d, mt_count=%d\n",
 			mt_op, mt_count);
 
-	/* Commands which need our pipelined read-ahead stages. */
 	switch (mt_op) {
 	case MTFSF:
 	case MTFSFM:

@@ -2353,27 +2353,6 @@ static void idetape_pad_zeros(ide_drive_t *drive, int bcount)
 	}
 }
 
-static int idetape_pipeline_size(ide_drive_t *drive)
-{
-	idetape_tape_t *tape = drive->driver_data;
-	idetape_stage_t *stage;
-	struct request *rq;
-	int size = 0;
-
-	idetape_wait_for_pipeline(drive);
-	stage = tape->first_stage;
-	while (stage != NULL) {
-		rq = &stage->rq;
-		size += tape->blk_size * (rq->nr_sectors -
-				rq->current_nr_sectors);
-		if (rq->errors == IDETAPE_ERROR_FILEMARK)
-			size += tape->blk_size;
-		stage = stage->next;
-	}
-	size += tape->merge_stage_size;
-	return size;
-}
-
 /*
  * Rewinds the tape to the Beginning Of the current Partition (BOP). We
  * currently support only one partition.

@@ -2779,7 +2758,7 @@ static int idetape_mtioctop(ide_drive_t *drive, short mt_op, int mt_count)
 
 /*
  * Our character device ioctls. General mtio.h magnetic io commands are
- * supported here, and not in the corresponding block interface. Our own
+ * supported here and not in the corresponding block interface. Our own
  * ide-tape ioctls are supported on both interfaces.
  */
 static int idetape_chrdev_ioctl(struct inode *inode, struct file *file,

@@ -2795,18 +2774,20 @@ static int idetape_chrdev_ioctl(struct inode *inode, struct file *file,
 
 	debug_log(DBG_CHRDEV, "Enter %s, cmd=%u\n", __func__, cmd);
 
-	tape->restart_speed_control_req = 1;
-	if (tape->chrdev_dir == IDETAPE_DIR_WRITE) {
-		idetape_empty_write_pipeline(drive);
+	if (tape->chrdev_dir == IDETAPE_DIR_WRITE)
 		idetape_flush_tape_buffers(drive);
-	}
+
 	if (cmd == MTIOCGET || cmd == MTIOCPOS) {
-		block_offset = idetape_pipeline_size(drive) /
-			(tape->blk_size * tape->user_bs_factor);
+		struct request *rq = tape->active_data_rq;
+
+		block_offset = (rq->nr_sectors - rq->current_nr_sectors) /
+			       (tape->blk_size * tape->user_bs_factor);
+
 		position = idetape_read_position(drive);
 		if (position < 0)
 			return -EIO;
 	}
+
 	switch (cmd) {
 	case MTIOCTOP:
 		if (copy_from_user(&mtop, argp, sizeof(struct mtop)))

@@ -2832,8 +2813,6 @@ static int idetape_chrdev_ioctl(struct inode *inode, struct file *file,
 			return -EFAULT;
 		return 0;
 	default:
-		if (tape->chrdev_dir == IDETAPE_DIR_READ)
-			idetape_discard_read_pipeline(drive, 1);
 		return idetape_blkdev_ioctl(drive, cmd, arg);
 	}
 }

@@ -1,67 +1,65 @@
-/*
- * IDE ATAPI streaming tape driver.
- *
- * This driver is a part of the Linux ide driver.
- *
- * The driver, in co-operation with ide.c, basically traverses the
- * request-list for the block device interface. The character device
- * interface, on the other hand, creates new requests, adds them
- * to the request-list of the block device, and waits for their completion.
- *
- * The block device major and minor numbers are determined from the
- * tape's relative position in the ide interfaces, as explained in ide.c.
- *
- * The character device interface consists of the following devices:
- *
- * ht0		major 37, minor 0	first  IDE tape, rewind on close.
- * ht1		major 37, minor 1	second IDE tape, rewind on close.
- * ...
- * nht0		major 37, minor 128	first  IDE tape, no rewind on close.
- * nht1		major 37, minor 129	second IDE tape, no rewind on close.
- * ...
- *
- * The general magnetic tape commands compatible interface, as defined by
- * include/linux/mtio.h, is accessible through the character device.
- *
- * General ide driver configuration options, such as the interrupt-unmask
- * flag, can be configured by issuing an ioctl to the block device interface,
- * as any other ide device.
- *
- * Our own ide-tape ioctl's can be issued to either the block device or
- * the character device interface.
- *
- * Maximal throughput with minimal bus load will usually be achieved in the
- * following scenario:
- *
- *	1.	ide-tape is operating in the pipelined operation mode.
- *	2.	No buffering is performed by the user backup program.
- *
- * Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive.
- *
- * Here are some words from the first releases of hd.c, which are quoted
- * in ide.c and apply here as well:
- *
- * | Special care is recommended.  Have Fun!
- *
- *	Possible improvements.
- *
- *	1.	Support for the ATAPI overlap protocol.
- *
- *		In order to maximize bus throughput, we currently use the DSC
- *		overlap method which enables ide.c to service requests from the
- *		other device while the tape is busy executing a command. The
- *		DSC overlap method involves polling the tape's status register
- *		for the DSC bit, and servicing the other device while the tape
- *		isn't ready.
- *
- *		In the current QIC development standard (December 1995),
- *		it is recommended that new tape drives will *in addition*
- *		implement the ATAPI overlap protocol, which is used for the
- *		same purpose - efficient use of the IDE bus, but is interrupt
- *		driven and thus has much less CPU overhead.
- *
- *		ATAPI overlap is likely to be supported in most new ATAPI
- *		devices, including new ATAPI cdroms, and thus provides us
- *		a method by which we can achieve higher throughput when
- *		sharing a (fast) ATA-2 disk with any (slow) new ATAPI device.
- */
+IDE ATAPI streaming tape driver.
+
+This driver is a part of the Linux ide driver.
+
+The driver, in co-operation with ide.c, basically traverses the
+request-list for the block device interface. The character device
+interface, on the other hand, creates new requests, adds them
+to the request-list of the block device, and waits for their completion.
+
+The block device major and minor numbers are determined from the
+tape's relative position in the ide interfaces, as explained in ide.c.
+
+The character device interface consists of the following devices:
+
+ht0		major 37, minor 0	first  IDE tape, rewind on close.
+ht1		major 37, minor 1	second IDE tape, rewind on close.
+...
+nht0		major 37, minor 128	first  IDE tape, no rewind on close.
+nht1		major 37, minor 129	second IDE tape, no rewind on close.
+...
+
+The general magnetic tape commands compatible interface, as defined by
+include/linux/mtio.h, is accessible through the character device.
+
+General ide driver configuration options, such as the interrupt-unmask
+flag, can be configured by issuing an ioctl to the block device interface,
+as any other ide device.
+
+Our own ide-tape ioctl's can be issued to either the block device or
+the character device interface.
+
+Maximal throughput with minimal bus load will usually be achieved in the
+following scenario:
+
+     1.	ide-tape is operating in the pipelined operation mode.
+     2.	No buffering is performed by the user backup program.
+
+Testing was done with a 2 GB CONNER CTMA 4000 IDE ATAPI Streaming Tape Drive.
+
+Here are some words from the first releases of hd.c, which are quoted
+in ide.c and apply here as well:
+
+| Special care is recommended.  Have Fun!
+
+Possible improvements:
+
+1. Support for the ATAPI overlap protocol.
+
+In order to maximize bus throughput, we currently use the DSC
+overlap method which enables ide.c to service requests from the
+other device while the tape is busy executing a command. The
+DSC overlap method involves polling the tape's status register
+for the DSC bit, and servicing the other device while the tape
+isn't ready.
+
+In the current QIC development standard (December 1995),
+it is recommended that new tape drives will *in addition*
+implement the ATAPI overlap protocol, which is used for the
+same purpose - efficient use of the IDE bus, but is interrupt
+driven and thus has much less CPU overhead.
+
+ATAPI overlap is likely to be supported in most new ATAPI
+devices, including new ATAPI cdroms, and thus provides us
+a method by which we can achieve higher throughput when
+sharing a (fast) ATA-2 disk with any (slow) new ATAPI device.

@@ -2384,26 +2384,19 @@ static int idetape_blkdev_ioctl(ide_drive_t *drive, unsigned int cmd,
 {
 	idetape_tape_t *tape = drive->driver_data;
 	void __user *argp = (void __user *)arg;
-
-	struct idetape_config {
-		int dsc_rw_frequency;
-		int dsc_media_access_frequency;
-		int nr_stages;
-	} config;
+	int dsc_rw_frequency;
 
 	debug_log(DBG_PROCS, "Enter %s\n", __func__);
 
 	switch (cmd) {
 	case 0x0340:
-		if (copy_from_user(&config, argp, sizeof(config)))
+		if (copy_from_user(&dsc_rw_frequency, argp, sizeof(int)))
 			return -EFAULT;
-		tape->best_dsc_rw_freq = config.dsc_rw_frequency;
-		tape->max_stages = config.nr_stages;
+		tape->best_dsc_rw_freq = dsc_rw_frequency;
 		break;
 	case 0x0350:
-		config.dsc_rw_frequency = (int) tape->best_dsc_rw_freq;
-		config.nr_stages = tape->max_stages;
-		if (copy_to_user(argp, &config, sizeof(config)))
+		dsc_rw_frequency = (int) tape->best_dsc_rw_freq;
+		if (copy_to_user(argp, &dsc_rw_frequency, sizeof(int)))
 			return -EFAULT;
 		break;
 	default:

@@ -366,7 +366,6 @@ typedef struct ide_tape_obj {
 	/* New requests will be added to the pipeline here */
 	idetape_stage_t *last_stage;
 	/* Optional free stage which we can use */
-	idetape_stage_t *cache_stage;
 	int pages_per_stage;
 	/* Wasted space in each stage */
 	int excess_bh_size;

@@ -2045,25 +2044,6 @@ static int idetape_position_tape(ide_drive_t *drive, unsigned int block,
 	return (idetape_queue_pc_tail(drive, &pc));
 }
 
-static void idetape_discard_read_pipeline(ide_drive_t *drive,
-					  int restore_position)
-{
-	idetape_tape_t *tape = drive->driver_data;
-	int cnt;
-	int seek, position;
-
-	cnt = __idetape_discard_read_pipeline(drive);
-	if (restore_position) {
-		position = idetape_read_position(drive);
-		seek = position > cnt ? position - cnt : 0;
-		if (idetape_position_tape(drive, seek, 0, 0)) {
-			printk(KERN_INFO "ide-tape: %s: position_tape failed in"
-					 " discard_pipeline()\n", tape->name);
-			return;
-		}
-	}
-}
-
 /*
  * Generate a read/write request for the block device interface and wait for it
  * to be serviced.

@@ -2093,19 +2073,6 @@ static int idetape_queue_rw_tail(ide_drive_t *drive, int cmd, int blocks,
 	return (tape->blk_size * (blocks-rq.current_nr_sectors));
 }
 
-/* start servicing the pipeline stages, starting from tape->next_stage. */
-static void idetape_plug_pipeline(ide_drive_t *drive)
-{
-	idetape_tape_t *tape = drive->driver_data;
-
-	if (tape->next_stage == NULL)
-		return;
-	if (!test_and_set_bit(IDETAPE_FLAG_PIPELINE_ACTIVE, &tape->flags)) {
-		idetape_activate_next_stage(drive);
-		(void) ide_do_drive_cmd(drive, tape->active_data_rq, ide_end);
-	}
-}
-
 static void idetape_create_inquiry_cmd(struct ide_atapi_pc *pc)
 {
 	idetape_init_pc(pc);

@@ -2154,25 +2121,6 @@ static int idetape_add_chrdev_write_request(ide_drive_t *drive, int blocks)
 					tape->merge_stage->bh);
 }
 
-/*
- * Wait until all pending pipeline requests are serviced. Typically called on
- * device close.
- */
-static void idetape_wait_for_pipeline(ide_drive_t *drive)
-{
-	idetape_tape_t *tape = drive->driver_data;
-	unsigned long flags;
-
-	while (tape->next_stage || test_bit(IDETAPE_FLAG_PIPELINE_ACTIVE,
-						&tape->flags)) {
-		idetape_plug_pipeline(drive);
-		spin_lock_irqsave(&tape->lock, flags);
-		if (test_bit(IDETAPE_FLAG_PIPELINE_ACTIVE, &tape->flags))
-			idetape_wait_for_request(drive, tape->active_data_rq);
-		spin_unlock_irqrestore(&tape->lock, flags);
-	}
-}
-
 static void idetape_restart_speed_control(ide_drive_t *drive)
 {
 	idetape_tape_t *tape = drive->driver_data;

@@ -2875,26 +2823,16 @@ static int idetape_chrdev_release(struct inode *inode, struct file *filp)
 
 	if (tape->chrdev_dir == IDETAPE_DIR_WRITE)
 		idetape_write_release(drive, minor);
-	if (tape->chrdev_dir == IDETAPE_DIR_READ) {
-		if (minor < 128)
-			idetape_discard_read_pipeline(drive, 1);
-		else
-			idetape_wait_for_pipeline(drive);
-	}
-	if (tape->cache_stage != NULL) {
-		__idetape_kfree_stage(tape->cache_stage);
-		tape->cache_stage = NULL;
-	}
+
 	if (minor < 128 && test_bit(IDETAPE_FLAG_MEDIUM_PRESENT, &tape->flags))
 		(void) idetape_rewind_tape(drive);
-	if (tape->chrdev_dir == IDETAPE_DIR_NONE) {
-		if (tape->door_locked == DOOR_LOCKED) {
-			if (idetape_create_prevent_cmd(drive, &pc, 0)) {
-				if (!idetape_queue_pc_tail(drive, &pc))
-					tape->door_locked = DOOR_UNLOCKED;
-			}
-		}
-	}
+
+	if (tape->chrdev_dir == IDETAPE_DIR_NONE &&
+	    tape->door_locked == DOOR_LOCKED &&
+	    idetape_create_prevent_cmd(drive, &pc, 0) &&
+	    !idetape_queue_pc_tail(drive, &pc))
+		tape->door_locked = DOOR_UNLOCKED;
+
 	clear_bit(IDETAPE_FLAG_BUSY, &tape->flags);
 	ide_tape_put(tape);
 	unlock_kernel();

@@ -2693,7 +2693,6 @@ static int idetape_mtioctop(ide_drive_t *drive, short mt_op, int mt_count)
 	case MTWEOF:
 		if (tape->write_prot)
 			return -EACCES;
-		idetape_discard_read_pipeline(drive, 1);
 		for (i = 0; i < mt_count; i++) {
 			retval = idetape_write_filemark(drive);
 			if (retval)

@@ -2701,12 +2700,10 @@ static int idetape_mtioctop(ide_drive_t *drive, short mt_op, int mt_count)
 		}
 		return 0;
 	case MTREW:
-		idetape_discard_read_pipeline(drive, 0);
 		if (idetape_rewind_tape(drive))
 			return -EIO;
 		return 0;
 	case MTLOAD:
-		idetape_discard_read_pipeline(drive, 0);
 		idetape_create_load_unload_cmd(drive, &pc,
 					       IDETAPE_LU_LOAD_MASK);
 		return idetape_queue_pc_tail(drive, &pc);

@@ -2721,7 +2718,6 @@ static int idetape_mtioctop(ide_drive_t *drive, short mt_op, int mt_count)
 				if (!idetape_queue_pc_tail(drive, &pc))
 					tape->door_locked = DOOR_UNLOCKED;
 		}
-		idetape_discard_read_pipeline(drive, 0);
 		idetape_create_load_unload_cmd(drive, &pc,
 					      !IDETAPE_LU_LOAD_MASK);
 		retval = idetape_queue_pc_tail(drive, &pc);

@@ -2729,10 +2725,8 @@ static int idetape_mtioctop(ide_drive_t *drive, short mt_op, int mt_count)
 			clear_bit(IDETAPE_FLAG_MEDIUM_PRESENT, &tape->flags);
 		return retval;
 	case MTNOP:
-		idetape_discard_read_pipeline(drive, 0);
 		return idetape_flush_tape_buffers(drive);
 	case MTRETEN:
-		idetape_discard_read_pipeline(drive, 0);
 		idetape_create_load_unload_cmd(drive, &pc,
 			IDETAPE_LU_RETENSION_MASK | IDETAPE_LU_LOAD_MASK);
 		return idetape_queue_pc_tail(drive, &pc);

@@ -2754,11 +2748,9 @@ static int idetape_mtioctop(ide_drive_t *drive, short mt_op, int mt_count)
 			set_bit(IDETAPE_FLAG_DETECT_BS, &tape->flags);
 		return 0;
 	case MTSEEK:
-		idetape_discard_read_pipeline(drive, 0);
 		return idetape_position_tape(drive,
 			mt_count * tape->user_bs_factor, tape->partition, 0);
 	case MTSETPART:
-		idetape_discard_read_pipeline(drive, 0);
 		return idetape_position_tape(drive, 0, mt_count, 0);
 	case MTFSR:
 	case MTBSR:

@@ -2699,11 +2699,10 @@ static inline void idetape_add_settings(ide_drive_t *drive) { ; }
  */
 static void idetape_setup(ide_drive_t *drive, idetape_tape_t *tape, int minor)
 {
-	unsigned long t1, tmid, tn, t;
+	unsigned long t;
 	int speed;
 	int stage_size;
 	u8 gcw[2];
-	struct sysinfo si;
 	u16 *ctl = (u16 *)&tape->caps[12];
 
 	spin_lock_init(&tape->lock);

@@ -2730,10 +2729,6 @@ static void idetape_setup(ide_drive_t *drive, idetape_tape_t *tape, int minor)
 	if (((gcw[0] & 0x60) >> 5) == 1)
 		set_bit(IDETAPE_FLAG_DRQ_INTERRUPT, &tape->flags);
 
-	tape->min_pipeline = 10;
-	tape->max_pipeline = 10;
-	tape->max_stages   = 10;
-
 	idetape_get_inquiry_results(drive);
 	idetape_get_mode_sense_results(drive);
 	ide_tape_get_bsize_from_bdesc(drive);

@@ -2751,36 +2746,10 @@ static void idetape_setup(ide_drive_t *drive, idetape_tape_t *tape, int minor)
 		tape->excess_bh_size = PAGE_SIZE - stage_size % PAGE_SIZE;
 	}
 
-	/* Select the "best" DSC read/write polling freq and pipeline size. */
+	/* select the "best" DSC read/write polling freq */
 	speed = max(*(u16 *)&tape->caps[14], *(u16 *)&tape->caps[8]);
 
-	tape->max_stages = speed * 1000 * 10 / tape->stage_size;
-
-	/* Limit memory use for pipeline to 10% of physical memory */
-	si_meminfo(&si);
-	if (tape->max_stages * tape->stage_size >
-			si.totalram * si.mem_unit / 10)
-		tape->max_stages =
-			si.totalram * si.mem_unit / (10 * tape->stage_size);
-
-	tape->max_stages   = min(tape->max_stages, IDETAPE_MAX_PIPELINE_STAGES);
-	tape->min_pipeline = min(tape->max_stages, IDETAPE_MIN_PIPELINE_STAGES);
-	tape->max_pipeline =
-		min(tape->max_stages * 2, IDETAPE_MAX_PIPELINE_STAGES);
-	if (tape->max_stages == 0) {
-		tape->max_stages   = 1;
-		tape->min_pipeline = 1;
-		tape->max_pipeline = 1;
-	}
-
-	t1 = (tape->stage_size * HZ) / (speed * 1000);
-	tmid = (*(u16 *)&tape->caps[16] * 32 * HZ) / (speed * 125);
-	tn = (IDETAPE_FIFO_THRESHOLD * tape->stage_size * HZ) / (speed * 1000);
-
-	if (tape->max_stages)
-		t = tn;
-	else
-		t = t1;
+	t = (tape->stage_size * HZ) / (speed * 1000);
 
 	/*
 	 * Ensure that the number we got makes sense; limit it within

@@ -2790,11 +2759,10 @@ static void idetape_setup(ide_drive_t *drive, idetape_tape_t *tape, int minor)
 				min_t(unsigned long, t, IDETAPE_DSC_RW_MAX),
 				IDETAPE_DSC_RW_MIN);
 	printk(KERN_INFO "ide-tape: %s <-> %s: %dKBps, %d*%dkB buffer, "
-		"%dkB pipeline, %lums tDSC%s\n",
+		"%lums tDSC%s\n",
 		drive->name, tape->name, *(u16 *)&tape->caps[14],
 		(*(u16 *)&tape->caps[16] * 512) / tape->stage_size,
 		tape->stage_size / 1024,
-		tape->max_stages * tape->stage_size / 1024,
 		tape->best_dsc_rw_freq * 1000 / HZ,
 		drive->using_dma ? ", DMA":"");
 

@@ -1187,69 +1187,6 @@ static void idetape_create_mode_sense_cmd(struct ide_atapi_pc *pc, u8 page_code)
 	pc->idetape_callback = &idetape_pc_callback;
 }
 
-static void idetape_calculate_speeds(ide_drive_t *drive)
-{
-	idetape_tape_t *tape = drive->driver_data;
-
-	if (time_after(jiffies,
-			tape->controlled_pipeline_head_time + 120 * HZ)) {
-		tape->controlled_previous_pipeline_head =
-			tape->controlled_last_pipeline_head;
-		tape->controlled_previous_head_time =
-			tape->controlled_pipeline_head_time;
-		tape->controlled_last_pipeline_head = tape->pipeline_head;
-		tape->controlled_pipeline_head_time = jiffies;
-	}
-	if (time_after(jiffies, tape->controlled_pipeline_head_time + 60 * HZ))
-		tape->controlled_pipeline_head_speed = (tape->pipeline_head -
-				tape->controlled_last_pipeline_head) * 32 * HZ /
-				(jiffies - tape->controlled_pipeline_head_time);
-	else if (time_after(jiffies, tape->controlled_previous_head_time))
-		tape->controlled_pipeline_head_speed = (tape->pipeline_head -
-				tape->controlled_previous_pipeline_head) * 32 *
-			HZ / (jiffies - tape->controlled_previous_head_time);
-
-	if (tape->nr_pending_stages < tape->max_stages/*- 1 */) {
-		/* -1 for read mode error recovery */
-		if (time_after(jiffies, tape->uncontrolled_previous_head_time +
-					10 * HZ)) {
-			tape->uncontrolled_pipeline_head_time = jiffies;
-			tape->uncontrolled_pipeline_head_speed =
-				(tape->pipeline_head -
-				 tape->uncontrolled_previous_pipeline_head) *
-				32 * HZ / (jiffies -
-					tape->uncontrolled_previous_head_time);
-		}
-	} else {
-		tape->uncontrolled_previous_head_time = jiffies;
-		tape->uncontrolled_previous_pipeline_head = tape->pipeline_head;
-		if (time_after(jiffies, tape->uncontrolled_pipeline_head_time +
-					30 * HZ))
-			tape->uncontrolled_pipeline_head_time = jiffies;
-
-	}
-	tape->pipeline_head_speed = max(tape->uncontrolled_pipeline_head_speed,
-					tape->controlled_pipeline_head_speed);
-
-	if (tape->speed_control == 1) {
-		if (tape->nr_pending_stages >= tape->max_stages / 2)
-			tape->max_insert_speed = tape->pipeline_head_speed +
-				(1100 - tape->pipeline_head_speed) * 2 *
-				(tape->nr_pending_stages - tape->max_stages / 2)
-				/ tape->max_stages;
-		else
-			tape->max_insert_speed = 500 +
-				(tape->pipeline_head_speed - 500) * 2 *
-				tape->nr_pending_stages / tape->max_stages;
-
-		if (tape->nr_pending_stages >= tape->max_stages * 99 / 100)
-			tape->max_insert_speed = 5000;
-	} else
-		tape->max_insert_speed = tape->speed_control;
-
-	tape->max_insert_speed = max(tape->max_insert_speed, 500);
-}
-
 static ide_startstop_t idetape_media_access_finished(ide_drive_t *drive)
 {
 	idetape_tape_t *tape = drive->driver_data;