linux-kernel - Re: [patch] bdi: add a user-tunable cpu

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Message-ID: <20121130221542.GM18574@lenny.home.zabbo.net>
Date:	Fri, 30 Nov 2012 14:15:42 -0800
From:	Zach Brown <zab@...hat.com>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	Jens Axboe <jaxboe@...ionio.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [patch] bdi: add a user-tunable cpu_list for the bdi flusher
 threads

> +	ret = cpulist_parse(buf, newmask);
> +	if (!ret) {
> +		spin_lock(&bdi->wb_lock);
> +		task = wb->task;
> +		get_task_struct(task);
> +		spin_unlock(&bdi->wb_lock);
> +		if (task)
> +			ret = set_cpus_allowed_ptr(task, newmask);
> +		put_task_struct(task);

If that test for a non-null task is needed then surely the get and put
need to be similarly protected :).

> +		bdi->flusher_cpumask = kmalloc(sizeof(cpumask_t), GFP_KERNEL);
> +		if (!bdi->flusher_cpumask)
> +			return -ENOMEM;

The bare GFP_KERNEL raises an eyebrow.  Some bdi_init() callers like
blk_alloc_queue_node() look like they'll want to pass in a gfp_t for the
allocation.

And shouldn't this be freed in the error path of bdi_init()?

- z
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