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scsi: convert to blk_delay_queue() 

It was always abuse to reuse the plugging infrastructure for this,
convert it to the (new) real API for delaying queueing a bit. A
default delay of 3 msec is defined, to match the previous
behaviour.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Jens Axboe 2010-04-16 21:13:15 +02:00
parent 0a41e90bb7
commit a488e74976
1 changed files with 19 additions and 25 deletions
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44
drivers/scsi/scsi_lib.c
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@ -67,6 +67,13 @@ static struct scsi_host_sg_pool scsi_sg_pools[] = {
struct kmem_cache *scsi_sdb_cache;
/*
* When to reinvoke queueing after a resource shortage. It's 3 msecs to
* not change behaviour from the previous unplug mechanism, experimentation
* may prove this needs changing.
*/
#define SCSI_QUEUE_DELAY 3
static void scsi_run_queue(struct request_queue *q);
/*
@ -149,14 +156,7 @@ static int __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)
/*
* Requeue this command. It will go before all other commands
* that are already in the queue.
*
* NOTE: there is magic here about the way the queue is plugged if
* we have no outstanding commands.
*
* Although we *don't* plug the queue, we call the request
* function. The SCSI request function detects the blocked condition
* and plugs the queue appropriately.
*/
*/
spin_lock_irqsave(q->queue_lock, flags);
blk_requeue_request(q, cmd->request);
spin_unlock_irqrestore(q->queue_lock, flags);
@ -1194,11 +1194,11 @@ int scsi_prep_return(struct request_queue *q, struct request *req, int ret)
case BLKPREP_DEFER:
/*
* If we defer, the blk_peek_request() returns NULL, but the
* queue must be restarted, so we plug here if no returning
* command will automatically do that.
* queue must be restarted, so we schedule a callback to happen
* shortly.
*/
if (sdev->device_busy == 0)
blk_plug_device(q);
blk_delay_queue(q, SCSI_QUEUE_DELAY);
break;
default:
req->cmd_flags |= REQ_DONTPREP;
@ -1237,7 +1237,7 @@ static inline int scsi_dev_queue_ready(struct request_queue *q,
sdev_printk(KERN_INFO, sdev,
"unblocking device at zero depth\n"));
} else {
blk_plug_device(q);
blk_delay_queue(q, SCSI_QUEUE_DELAY);
return 0;
}
}
@ -1467,7 +1467,7 @@ static void scsi_request_fn(struct request_queue *q)
* the host is no longer able to accept any more requests.
*/
shost = sdev->host;
while (!blk_queue_plugged(q)) {
for (;;) {
int rtn;
/*
* get next queueable request. We do this early to make sure
@ -1546,15 +1546,8 @@ static void scsi_request_fn(struct request_queue *q)
*/
rtn = scsi_dispatch_cmd(cmd);
spin_lock_irq(q->queue_lock);
if(rtn) {
/* we're refusing the command; because of
* the way locks get dropped, we need to
* check here if plugging is required */
if(sdev->device_busy == 0)
blk_plug_device(q);
break;
}
if (rtn)
goto out_delay;
}
goto out;
@ -1573,9 +1566,10 @@ static void scsi_request_fn(struct request_queue *q)
spin_lock_irq(q->queue_lock);
blk_requeue_request(q, req);
sdev->device_busy--;
if(sdev->device_busy == 0)
blk_plug_device(q);
out:
out_delay:
if (sdev->device_busy == 0)
blk_delay_queue(q, SCSI_QUEUE_DELAY);
out:
/* must be careful here...if we trigger the ->remove() function
* we cannot be holding the q lock */
spin_unlock_irq(q->queue_lock);