[PATCH 01/18] ide: dequeue in-flight request

Tejun Heo
2009-05-08T03:00:22Z

ide generally has single request in flight and tracks it using
hwif->rq and all state handlers follow the following convention.

* ide_started is returned if the request is in flight.

* ide_stopped is returned if the queue needs to be restarted. The
request might or might not have been processed fully or partially.

* hwif->rq is set to NULL, when an issued request completes.

So, dequeueing model can be implemented by dequeueing after fetch,
requeueing if hwif->rq isn't NULL on ide_stopped return and doing
about the same thing on completion / port unlock paths. These changes
can be made in ide-io proper.

In addition to the above main changes, the following updates are
necessary.

* ide-cd shouldn't dequeue a request when issuing REQUEST SENSE for it
as the request is already dequeued.

* ide-atapi uses request queue as stack when issuing REQUEST SENSE to
put the REQUEST SENSE in front of the failed request. This now
needs to be done using requeueing.

[ Impact: dequeue in-flight request ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Borislav Petkov <petkovbb@googlemail.com>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
---
drivers/ide/ide-atapi.c | 14 ++++++++++++--
drivers/ide/ide-cd.c | 8 --------
drivers/ide/ide-io.c | 34 +++++++++++++++++++++++++++-------
3 files changed, 39 insertions(+), 17 deletions(-)

diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c
index 792534d..2874c3d 100644
--- a/drivers/ide/ide-atapi.c
+++ b/drivers/ide/ide-atapi.c
@@ -246,6 +246,7 @@ EXPORT_SYMBOL_GPL(ide_queue_sense_rq);
*/
void ide_retry_pc(ide_drive_t *drive)
{
+ struct request *failed_rq = drive->hwif->rq;
struct request *sense_rq = &drive->sense_rq;
struct ide_atapi_pc *pc = &drive->request_sense_pc;

@@ -260,8 +261,17 @@ void ide_retry_pc(ide_drive_t *drive)
if (drive->media == ide_tape)
set_bit(IDE_AFLAG_IGNORE_DSC, &drive->atapi_flags);

- if (ide_queue_sense_rq(drive, pc))
- ide_complete_rq(drive, -EIO, blk_rq_bytes(drive->hwif->rq));
+ /*
+ * Push back the failed request and put request sense on top
+ * of it. The failed command will be retried after sense data
+ * is acquired.
+ */
+ blk_requeue_request(failed_rq->q, failed_rq);
+ drive->hwif->rq = NULL;
+ if (ide_queue_sense_rq(drive, pc)) {
+ blkdev_dequeue_request(failed_rq);
+ ide_complete_rq(drive, -EIO, blk_rq_bytes(failed_rq));
+ }
}
EXPORT_SYMBOL_GPL(ide_retry_pc);

diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
index 1a58b38..1f88911 100644
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -404,15 +404,7 @@ static int cdrom_decode_status(ide_drive_t *drive, u8 stat)

end_request:
if (stat & ATA_ERR) {
- struct request_queue *q = drive->queue;
- unsigned long flags;
-
- spin_lock_irqsave(q->queue_lock, flags);
- blkdev_dequeue_request(rq);
- spin_unlock_irqrestore(q->queue_lock, flags);
-
hwif->rq = NULL;
-
return ide_queue_sense_rq(drive, rq) ? 2 : 1;
} else
return 2;
diff --git a/drivers/ide/ide-io.c b/drivers/ide/ide-io.c
index ca2519d..abda733 100644
--- a/drivers/ide/ide-io.c
+++ b/drivers/ide/ide-io.c
@@ -487,10 +487,10 @@ void do_ide_request(struct request_queue *q)

if (!ide_lock_port(hwif)) {
ide_hwif_t *prev_port;
+
+ WARN_ON_ONCE(hwif->rq);
repeat:
prev_port = hwif->host->cur_port;
- hwif->rq = NULL;
-
if (drive->dev_flags & IDE_DFLAG_SLEEPING &&
time_after(drive->sleep, jiffies)) {
ide_unlock_port(hwif);
@@ -519,7 +519,12 @@ repeat:
* we know that the queue isn't empty, but this can happen
* if the q->prep_rq_fn() decides to kill a request
*/
- rq = elv_next_request(drive->queue);
+ if (!rq) {
+ rq = elv_next_request(drive->queue);
+ if (rq)
+ blkdev_dequeue_request(rq);
+ }
+
spin_unlock_irq(q->queue_lock);
spin_lock_irq(&hwif->lock);

@@ -555,8 +560,11 @@ repeat:
startstop = start_request(drive, rq);
spin_lock_irq(&hwif->lock);

- if (startstop == ide_stopped)
+ if (startstop == ide_stopped) {
+ rq = hwif->rq;
+ hwif->rq = NULL;
goto repeat;
+ }
} else
goto plug_device;
out:
@@ -572,18 +580,24 @@ plug_device:
plug_device_2:
spin_lock_irq(q->queue_lock);

+ if (rq)
+ blk_requeue_request(q, rq);
if (!elv_queue_empty(q))
blk_plug_device(q);
}

-static void ide_plug_device(ide_drive_t *drive)
+static void ide_requeue_and_plug(ide_drive_t *drive, struct request *rq)
{
struct request_queue *q = drive->queue;
unsigned long flags;

spin_lock_irqsave(q->queue_lock, flags);
+
+ if (rq)
+ blk_requeue_request(q, rq);
if (!elv_queue_empty(q))
blk_plug_device(q);
+
spin_unlock_irqrestore(q->queue_lock, flags);
}

@@ -632,6 +646,7 @@ void ide_timer_expiry (unsigned long data)
unsigned long flags;
int wait = -1;
int plug_device = 0;
+ struct request *uninitialized_var(rq_in_flight);

spin_lock_irqsave(&hwif->lock, flags);

@@ -693,6 +708,8 @@ void ide_timer_expiry (unsigned long data)
spin_lock_irq(&hwif->lock);
enable_irq(hwif->irq);
if (startstop == ide_stopped) {
+ rq_in_flight = hwif->rq;
+ hwif->rq = NULL;
ide_unlock_port(hwif);
plug_device = 1;
}
@@ -701,7 +718,7 @@ void ide_timer_expiry (unsigned long data)

if (plug_device) {
ide_unlock_host(hwif->host);
- ide_plug_device(drive);
+ ide_requeue_and_plug(drive, rq_in_flight);
}
}

@@ -787,6 +804,7 @@ irqreturn_t ide_intr (int irq, void *dev_id)
ide_startstop_t startstop;
irqreturn_t irq_ret = IRQ_NONE;
int plug_device = 0;
+ struct request *uninitialized_var(rq_in_flight);

if (host->host_flags & IDE_HFLAG_SERIALIZE) {
if (hwif != host->cur_port)
@@ -866,6 +884,8 @@ irqreturn_t ide_intr (int irq, void *dev_id)
*/
if (startstop == ide_stopped) {
BUG_ON(hwif->handler);
+ rq_in_flight = hwif->rq;
+ hwif->rq = NULL;
ide_unlock_port(hwif);
plug_device = 1;
}
@@ -875,7 +895,7 @@ out:
out_early:
if (plug_device) {
ide_unlock_host(hwif->host);
- ide_plug_device(drive);
+ ide_requeue_and_plug(drive, rq_in_flight);
}

return irq_ret;
--
1.6.0.2