linux-kernel - Re: [PATCH v2 3/3] mm/vmalloc: move VM_UNINITIALIZED just before show_numa

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Date:	Tue, 03 Sep 2013 13:40:46 +0800
From:	Zhang Yanfei <zhangyanfei@...fujitsu.com>
To:	Wanpeng Li <liwanp@...ux.vnet.ibm.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] mm/vmalloc: move VM_UNINITIALIZED just before
 show_numa_info

On 09/03/2013 11:00 AM, Wanpeng Li wrote:
> The VM_UNINITIALIZED/VM_UNLIST flag introduced by commit f5252e00(mm: avoid
> null pointer access in vm_struct via /proc/vmallocinfo) is used to avoid
> accessing the pages field with unallocated page when show_numa_info() is
> called. This patch move the check just before show_numa_info in order that
> some messages still can be dumped via /proc/vmallocinfo.
> 
> Signed-off-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>

Hmmm, sorry again. Please revert commit
d157a55815ffff48caec311dfb543ce8a79e283e. That said, we could still
do the check in show_numa_info like before.

> ---
>  mm/vmalloc.c |   10 +++++-----
>  1 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index e3ec8b4..c4720cd 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2590,11 +2590,6 @@ static int s_show(struct seq_file *m, void *p)
>  
>  	v = va->vm;
>  
> -	/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
> -	smp_rmb();
> -	if (v->flags & VM_UNINITIALIZED)
> -		return 0;
> -
>  	seq_printf(m, "0x%pK-0x%pK %7ld",
>  		v->addr, v->addr + v->size, v->size);
>  
> @@ -2622,6 +2617,11 @@ static int s_show(struct seq_file *m, void *p)
>  	if (v->flags & VM_VPAGES)
>  		seq_printf(m, " vpages");
>  
> +	/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
> +	smp_rmb();
> +	if (v->flags & VM_UNINITIALIZED)
> +		return 0;
> +
>  	show_numa_info(m, v);
>  	seq_putc(m, '\n');
>  	return 0;
> 


-- 
Thanks.
Zhang Yanfei
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