linux-kernel - Re: [PATCH 5/5] uprobes: write_opcode: alloc the new page outside of "retry" loop

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Date:	Wed, 20 Jun 2012 14:29:39 +0200
From:	Anton Arapov <anton@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] uprobes: write_opcode: alloc the new page outside of
 "retry" loop

On Tue, Jun 19, 2012 at 09:47:59PM +0200, Oleg Nesterov wrote:
> It is ugly to free and re-alloc new_page if write_opcode() needs to
> retry. Move alloc_page_vma/page_cache_release outside of "retry" loop.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
>  kernel/events/uprobes.c |   26 +++++++++++---------------
>  1 files changed, 11 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 442064d..3fd7bdf 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -214,19 +214,18 @@ static int write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
>  	struct vm_area_struct *vma;
>  	int ret;
>  
> -retry:
> -	/* Read the page with vaddr into memory */
> -	ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma);
> -	if (ret <= 0)
> -		return ret;
> -
> -	ret = -ENOMEM;
>  	new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
  Should we want NULL instead of vma in alloc_page_vma()? Or
initialize vma with NULL...

>  	if (!new_page)
> -		goto put_old;
> +		return -ENOMEM;
>  
>  	__SetPageUptodate(new_page);
>  
> + retry:
> +	/* Read the page with vaddr into memory */
> +	ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma);
> +	if (ret <= 0)
> +		goto out;
> +
[cut]

Anton.
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