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Commit c284de61 authored by Artem Bityutskiy's avatar Artem Bityutskiy Committed by Jens Axboe
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writeback: cleanup bdi_register 



This patch makes sure we first initialize everything and set the BDI_registered
flag, and only after this we add the bdi to 'bdi_list'. Current code adds the
bdi to the list too early, and as a result I the

WARN(!test_bit(BDI_registered, &bdi->state)

in bdi forker is triggered. Also, it is in general good practice to make things
visible only when they are fully initialized.

Also, this patch does few micro clean-ups:
1. Removes the 'exit' label which does not do anything, just returns. This
   allows to get rid of few braces and 'ret' variable and make the code smaller.
2. If 'kthread_run()' fails, remove the error code it returns, not hard-coded
   '-ENOMEM'. Theoretically, some day 'kthread_run()' can return something
   else. Also, in case of failure it is not necessary to set 'bdi->wb.task' to
   NULL.

Signed-off-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 60332023

mm/backing-dev.c

+11 −19
Original line number Diff line number Diff line
@@ -511,23 +511,16 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent, 
		const char *fmt, ...)

{

	va_list args;

	int ret = 0;

	struct device *dev;



	if (bdi->dev)	/* The driver needs to use separate queues per device */

		goto exit;

		return 0;



	va_start(args, fmt);

	dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);

	va_end(args);

	if (IS_ERR(dev)) {

		ret = PTR_ERR(dev);

		goto exit;

	}



	spin_lock_bh(&bdi_lock);

	list_add_tail_rcu(&bdi->bdi_list, &bdi_list);

	spin_unlock_bh(&bdi_lock);

	if (IS_ERR(dev))

		return PTR_ERR(dev);



	bdi->dev = dev;
@@ -541,20 +534,19 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent, 


		wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",

						dev_name(dev));

		if (IS_ERR(wb->task)) {

			wb->task = NULL;

			ret = -ENOMEM;



			bdi_remove_from_list(bdi);

			goto exit;

		}

		if (IS_ERR(wb->task))

			return PTR_ERR(wb->task);

	}



	bdi_debug_register(bdi, dev_name(dev));

	set_bit(BDI_registered, &bdi->state);



	spin_lock_bh(&bdi_lock);

	list_add_tail_rcu(&bdi->bdi_list, &bdi_list);

	spin_unlock_bh(&bdi_lock);



	trace_writeback_bdi_register(bdi);

exit:

	return ret;

	return 0;

}

EXPORT_SYMBOL(bdi_register);