linux-kernel - Re: [PATCH] mempolicy: reduce stack size of migrate

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Message-Id: <20100621090550.B4F8.A69D9226@jp.fujitsu.com>
Date:	Mon, 21 Jun 2010 20:45:47 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	kosaki.motohiro@...fujitsu.com,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mempolicy: reduce stack size of migrate_pages()

> >  	const struct cred *cred = current_cred(), *tcred;
> > -	struct mm_struct *mm;
> > +	struct mm_struct *mm = NULL;
> >  	struct task_struct *task;
> > -	nodemask_t old;
> > -	nodemask_t new;
> >  	nodemask_t task_nodes;
> >  	int err;
> > +	NODEMASK_SCRATCH(scratch);
> > +	nodemask_t *old = &scratch->mask1;
> > +	nodemask_t *new = &scratch->mask2;
> >
> > +	if (!scratch)
> > +		return -ENOMEM;
> 
> It doesn't matter in practice, but it makes me all queazy to see code
> which plays with pointers which might be NULL.

I see. thanks.
Do we need to send you updated patch?


> 
> --- a/mm/mempolicy.c~mempolicy-reduce-stack-size-of-migrate_pages-fix
> +++ a/mm/mempolicy.c
> @@ -1279,13 +1279,16 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pi
>  	struct task_struct *task;
>  	nodemask_t task_nodes;
>  	int err;
> +	nodemask_t *old;
> +	nodemask_t *new;
>  	NODEMASK_SCRATCH(scratch);
> -	nodemask_t *old = &scratch->mask1;
> -	nodemask_t *new = &scratch->mask2;
>  
>  	if (!scratch)
>  		return -ENOMEM;
>  
> +	old = &scratch->mask1;
> +	new = &scratch->mask2;
> +
>  	err = get_nodes(old, old_nodes, maxnode);
>  	if (err)
>  		goto out;
> _
> 
> --
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