linux-kernel - Re: [-mm][PATCH 2/4] Setup the memrlimit controller (v5)

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Date:	Wed, 11 Jun 2008 12:15:10 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	righi.andrea@...il.com
Cc:	balbir@...ux.vnet.ibm.com, linux-mm@...ck.org,
	skumar@...ux.vnet.ibm.com, yamamoto@...inux.co.jp,
	menage@...gle.com, lizf@...fujitsu.com,
	linux-kernel@...r.kernel.org, xemul@...nvz.org,
	kamezawa.hiroyu@...fujitsu.com
Subject: Re: [-mm][PATCH 2/4] Setup the memrlimit controller (v5)

On Wed, 11 Jun 2008 19:10:40 +0200 (MEST)
Andrea Righi <righi.andrea@...il.com> wrote:

> Balbir Singh wrote:
> > +static int memrlimit_cgroup_write_strategy(char *buf, unsigned long long *tmp)
> > +{
> > +	*tmp = memparse(buf, &buf);
> > +	if (*buf != '\0')
> > +		return -EINVAL;
> > +
> > +	*tmp = PAGE_ALIGN(*tmp);
> > +	return 0;
> > +}
> 
> We shouldn't use PAGE_ALIGN() here, otherwise we limit the address space
> to 4GB on 32-bit architectures (that could be reasonable, because this
> is a per-cgroup limit and not per-process).
> 
> Signed-off-by: Andrea Righi <righi.andrea@...il.com>
> ---
>  mm/memrlimitcgroup.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/memrlimitcgroup.c b/mm/memrlimitcgroup.c
> index 9a03d7d..2d42ff3 100644
> --- a/mm/memrlimitcgroup.c
> +++ b/mm/memrlimitcgroup.c
> @@ -29,6 +29,8 @@
>  #include <linux/res_counter.h>
>  #include <linux/memrlimitcgroup.h>
>  
> +#define PAGE_ALIGN64(addr) (((((addr)+PAGE_SIZE-1))>>PAGE_SHIFT)<<PAGE_SHIFT)
> +
>  struct cgroup_subsys memrlimit_cgroup_subsys;
>  
>  struct memrlimit_cgroup {
> @@ -124,7 +126,7 @@ static int memrlimit_cgroup_write_strategy(char *buf, unsigned long long *tmp)
>  	if (*buf != '\0')
>  		return -EINVAL;
>  
> -	*tmp = PAGE_ALIGN(*tmp);
> +	*tmp = PAGE_ALIGN64(*tmp);
>  	return 0;
>  }
>  

I don't beleive the change is needed.

#define PAGE_ALIGN(addr)	(((addr)+PAGE_SIZE-1)&PAGE_MASK)

that implementation will behaved as desired when passed a 64-bit addr?
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