writeback: cleanup bdi_register (c284de61) · Commits · 戴 / test

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:

Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by:

Jens Axboe <jaxboe@fusionio.com>

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);

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