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Date: Sun, 9 Mar 2008 18:10:32 +0100
From: Borislav Petkov <petkovbb@...glemail.com>
To: <bzolnier@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
Borislav Petkov <petkovbb@...il.com>
Subject: [PATCH 4/4] ide-tape: remove pipeline-specific code from idetape_add_chrdev_read_request()
In order to do away with queueing read requests on the pipeline, several things
have to be done:
1. Do not allocate additional pipeline stages in idetape_init_read() until
(tape->nr_stages < max_stages) and do only read operation preparations. As a
collateral result, idetape_add_stage_tail() becomes unused so remove it.
2. Wait for all queued pipeline requests to complete before queueing
the read request's buffer directly thru idetape_queue_rw_tail()
3. Do next request buffer allocation (tape->merge_stage)
Signed-off-by: Borislav Petkov <petkovbb@...il.com>
---
drivers/ide/ide-tape.c | 81 +++++++++++++-----------------------------------
1 files changed, 22 insertions(+), 59 deletions(-)
diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index a06d83f..5afcbf4 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -1673,29 +1673,6 @@ static void idetape_switch_buffers(idetape_tape_t *tape, idetape_stage_t *stage)
idetape_init_merge_stage(tape);
}
-/* Add a new stage at the end of the pipeline. */
-static void idetape_add_stage_tail(ide_drive_t *drive, idetape_stage_t *stage)
-{
- idetape_tape_t *tape = drive->driver_data;
- unsigned long flags;
-
- debug_log(DBG_PROCS, "Enter %s\n", __func__);
-
- spin_lock_irqsave(&tape->lock, flags);
- stage->next = NULL;
- if (tape->last_stage != NULL)
- tape->last_stage->next = stage;
- else
- tape->first_stage = stage;
- tape->next_stage = stage;
- tape->last_stage = stage;
- if (tape->next_stage == NULL)
- tape->next_stage = tape->last_stage;
- tape->nr_stages++;
- tape->nr_pending_stages++;
- spin_unlock_irqrestore(&tape->lock, flags);
-}
-
/* Install a completion in a pending request and sleep until it is serviced. The
* caller should ensure that the request will not be serviced before we install
* the completion (usually by disabling interrupts).
@@ -2219,10 +2196,7 @@ static void idetape_empty_write_pipeline(ide_drive_t *drive)
static int idetape_init_read(ide_drive_t *drive, int max_stages)
{
idetape_tape_t *tape = drive->driver_data;
- idetape_stage_t *new_stage;
- struct request rq;
int bytes_read;
- u16 blocks = *(u16 *)&tape->caps[12];
/* Initialize read operation */
if (tape->chrdev_dir != IDETAPE_DIR_READ) {
@@ -2258,21 +2232,7 @@ static int idetape_init_read(ide_drive_t *drive, int max_stages)
}
}
}
- idetape_init_rq(&rq, REQ_IDETAPE_READ);
- rq.sector = tape->first_frame;
- rq.nr_sectors = blocks;
- rq.current_nr_sectors = blocks;
- if (!test_bit(IDETAPE_FLAG_PIPELINE_ERR, &tape->flags) &&
- tape->nr_stages < max_stages) {
- new_stage = __idetape_kmalloc_stage(tape, 0, 0);
- while (new_stage != NULL) {
- new_stage->rq = rq;
- idetape_add_stage_tail(drive, new_stage);
- if (tape->nr_stages >= max_stages)
- break;
- new_stage = __idetape_kmalloc_stage(tape, 0, 0);
- }
- }
+
if (!test_bit(IDETAPE_FLAG_PIPELINE_ACTIVE, &tape->flags)) {
if (tape->nr_pending_stages >= 3 * max_stages / 4) {
tape->measure_insert_time = 1;
@@ -2292,7 +2252,7 @@ static int idetape_init_read(ide_drive_t *drive, int max_stages)
static int idetape_add_chrdev_read_request(ide_drive_t *drive, int blocks)
{
idetape_tape_t *tape = drive->driver_data;
- unsigned long flags;
+ idetape_stage_t *new_stage;
struct request *rq_ptr;
int bytes_read;
@@ -2302,31 +2262,34 @@ static int idetape_add_chrdev_read_request(ide_drive_t *drive, int blocks)
if (test_bit(IDETAPE_FLAG_FILEMARK, &tape->flags))
return 0;
- /* Wait for the next block to reach the head of the pipeline. */
idetape_init_read(drive, tape->max_stages);
- if (tape->first_stage == NULL) {
- if (test_bit(IDETAPE_FLAG_PIPELINE_ERR, &tape->flags))
- return 0;
- return idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, blocks,
- tape->merge_stage->bh);
- }
- idetape_wait_first_stage(drive);
- rq_ptr = &tape->first_stage->rq;
- bytes_read = tape->blk_size * (rq_ptr->nr_sectors -
- rq_ptr->current_nr_sectors);
- rq_ptr->nr_sectors = 0;
- rq_ptr->current_nr_sectors = 0;
+ idetape_wait_for_pipeline(drive);
+
+ if (test_bit(IDETAPE_FLAG_PIPELINE_ERR, &tape->flags))
+ return 0;
+
+ bytes_read = idetape_queue_rw_tail(drive, REQ_IDETAPE_READ, blocks,
+ tape->merge_stage->bh);
+
+ rq_ptr = &tape->merge_stage->rq;
if (rq_ptr->errors == IDETAPE_ERROR_EOD)
return 0;
else {
- idetape_switch_buffers(tape, tape->first_stage);
if (rq_ptr->errors == IDETAPE_ERROR_FILEMARK)
set_bit(IDETAPE_FLAG_FILEMARK, &tape->flags);
- spin_lock_irqsave(&tape->lock, flags);
- idetape_remove_stage_head(drive);
- spin_unlock_irqrestore(&tape->lock, flags);
+
+ __idetape_kfree_stage(tape->merge_stage);
+
+ new_stage = __idetape_kmalloc_stage(tape, 0, 0);
+ if (!new_stage) {
+ printk(KERN_ERR "ide-tape: %s: cannot alloc request "
+ "buffer.\n", __func__);
+ return -ENOMEM;
+ }
+ idetape_switch_buffers(tape, new_stage);
}
+
if (bytes_read > blocks * tape->blk_size) {
printk(KERN_ERR "ide-tape: bug: trying to return more bytes"
" than requested\n");
--
1.5.4.1
--
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