Re: 2.5.69-mjb1: undefined reference to `blk_queue_empty'

[Bharata B Rao]

On Tue, May 13, 2003 at 08:11:55PM +0200, Jens Axboe wrote:
> > >  
> > >  	/* For now we assume we have the device to ourselves */
> > >  	/* Just a quick sanity check */
> > > -	if (!blk_queue_empty(bdev_get_queue(dump_bdev->bdev))) {
> > > +	if (elv_next_request(bdev_get_queue(dump_bdev->bdev))) {
> > >  		/* i/o in flight - safer to quit */
> > >  		return -EBUSY;
> > >  	}
> 
> this looks horribly racy (of the io scheduler internals corrupting
> kind), I don't see you holding the queue lock here. some io schedulers
> do non-significant amount of work inside they next_request functions,
> moving from back-end lists to dispatch queue.
> 

Jens,

All we want to do here is to check if there are requests in the
queue. Hence thinking of using elv_queue_empty(). Do you think
we still need to acquire queue lock for this ? This code will be
run when we have stopped everything else in other cpus by putting
them into spin.

--- 2569+mjb1/drivers/dump/dump_blockdev.c.orig	Wed May 14 13:23:36 2003
+++ 2569+mjb1/drivers/dump/dump_blockdev.c	Wed May 14 13:24:58 2003
@@ -258,10 +258,11 @@
 dump_block_silence(struct dump_dev *dev)
 {
 	struct dump_blockdev *dump_bdev = DUMP_BDEV(dev);
+	struct request_queue *q = bdev_get_queue(dump_bdev->bdev);
 
 	/* For now we assume we have the device to ourselves */
 	/* Just a quick sanity check */
-	if (!blk_queue_empty(bdev_get_queue(dump_bdev->bdev))) {
+	if (!elv_queue_empty(q)) {
 		/* i/o in flight - safer to quit */
 		return -EBUSY;
 	}

Regards,
Bharata.