linux-kernel - Re: [PATCH 1/8] cgroups: add res_counter_write

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Date:	Wed, 25 Jan 2012 19:31:03 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Li Zefan <lizf@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Aditya Kali <adityakali@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Kay Sievers <kay.sievers@...y.org>,
	Tim Hockin <thockin@...kin.org>, Tejun Heo <htejun@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/8] cgroups: add res_counter_write_u64() API

On Mon, Jan 16, 2012 at 02:27:13PM +0200, Kirill A. Shutemov wrote:
> On Fri, Jan 13, 2012 at 07:13:47PM +0100, Frederic Weisbecker wrote:
> > Extend the resource counter API with a mirror of res_counter_read_u64() to
> > make it handy to update a resource counter value from a cgroup subsystem
> > u64 value file.
> 
> I still think it worth to have two versions of res_counter_write_u64().
> From my POV, it's clean enough, but consistent with res_counter_read_u64()
> and faster on 64bit system.
> 
> What do you think?

Yeah right let's do this. Can I get your signed-off-by to take the below?

Thanks.

> 
> ---
> diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
> index c9d625c..1b3fe05 100644
> --- a/include/linux/res_counter.h
> +++ b/include/linux/res_counter.h
> @@ -82,6 +82,8 @@ int res_counter_memparse_write_strategy(const char *buf,
>  int res_counter_write(struct res_counter *counter, int member,
>  		      const char *buffer, write_strategy_fn write_strategy);
>  
> +void res_counter_write_u64(struct res_counter *counter, int member, u64 val);
> +
>  /*
>   * the field descriptors. one for each member of res_counter
>   */
> diff --git a/kernel/res_counter.c b/kernel/res_counter.c
> index 6d269cc..aad4ddb 100644
> --- a/kernel/res_counter.c
> +++ b/kernel/res_counter.c
> @@ -167,12 +167,27 @@ int res_counter_memparse_write_strategy(const char *buf,
>  	return 0;
>  }
>  
> +#if BITS_PER_LONG == 32
> +void res_counter_write_u64(struct res_counter *counter, int member, u64 val)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&counter->lock, flags);
> +	*res_counter_member(counter, member) = val;
> +	spin_unlock_irqrestore(&counter->lock, flags);
> +}
> +#else
> +void res_counter_write_u64(struct res_counter *counter, int member, u64 val)
> +{
> +	*res_counter_member(counter, member) = val;
> +}
> +#endif
> +
>  int res_counter_write(struct res_counter *counter, int member,
>  		      const char *buf, write_strategy_fn write_strategy)
>  {
>  	char *end;
> -	unsigned long flags;
> -	unsigned long long tmp, *val;
> +	unsigned long long tmp;
>  
>  	if (write_strategy) {
>  		if (write_strategy(buf, &tmp))
> @@ -182,9 +197,8 @@ int res_counter_write(struct res_counter *counter, int member,
>  		if (*end != '\0')
>  			return -EINVAL;
>  	}
> -	spin_lock_irqsave(&counter->lock, flags);
> -	val = res_counter_member(counter, member);
> -	*val = tmp;
> -	spin_unlock_irqrestore(&counter->lock, flags);
> +
> +	res_counter_write_u64(counter, member, tmp);
> +
>  	return 0;
>  }
> -- 
>  Kirill A. Shutemov
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