linux-kernel - Re: [RFC 1/3]block: seperate CFQ io context management code

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Message-ID: <4F040BA7.9070203@lge.com>
Date:	Wed, 04 Jan 2012 17:19:51 +0900
From:	Namhyung Kim <namhyung.kim@....com>
To:	shaohua.li@...el.com
CC:	linux-kernel@...r.kernel.org, axboe@...nel.dk, vgoyal@...hat.com,
	jmoyer@...hat.com
Subject: Re: [RFC 1/3]block: seperate CFQ io context management code

Hi,

Two of nitpicks below ..


2012-01-04 3:53 PM, Shaohua Li Wrote:
> CFQ's io context management creates a per-device io context for each task.
> It's quite generic. Separate it from CFQ, and use it for fiops I/O scheduler.
> 
> Signed-off-by: Shaohua Li<shaohua.li@...el.com>
> ---

[snip]

> +int ioc_builder_init(struct ioc_builder *builder)
> +{
> +	if (!builder->alloc_ioc || !builder->free_ioc)
> +		return -ENOMEM;
> +
> +	builder->ioc_count = alloc_percpu(unsigned long);
> +	if (!builder->ioc_count)
> +		return -ENOMEM;
> +
> +	builder->ioc_gone = NULL;
> +	spin_lock_init(&builder->ioc_gone_lock);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(ioc_builder_init);
> +
> +void io_context_builder_exit(struct ioc_builder *builder)

It'd be better using 'ioc_builder_exit' as a name for consistency, IMHO.


> +{
> +	DECLARE_COMPLETION_ONSTACK(all_gone);
> +
> +	builder->ioc_gone =&all_gone;
> +	/* ioc_gone's update must be visible before reading ioc_count */
> +	smp_wmb();
> +
> +	/*
> +	 * this also protects us from entering cfq_slab_kill() with
> +	 * pending RCU callbacks
> +	 */
> +	if (elv_ioc_count_read(*builder->ioc_count))
> +		wait_for_completion(&all_gone);
> +
> +	free_percpu(builder->ioc_count);
> +}
> +EXPORT_SYMBOL(io_context_builder_exit);

[snip]

> +static void queue_data_cic_free_rcu(struct rcu_head *head)
> +{
> +	struct dev_io_context *cic;
> +	struct ioc_builder *builder;
> +
> +	cic = container_of(head, struct dev_io_context, rcu_head);
> +	builder = cic->builder;
> +
> +	builder->free_ioc(builder, cic);
> +	elv_ioc_count_dec(*builder->ioc_count);
> +
> +	if (builder->ioc_gone) {
> +		/*
> +		 * CFQ scheduler is exiting, grab exit lock and check

s/CFQ/IO/ ?

Thanks.
Namhyung Kim
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