linux-kernel - Re: [PATCH 13/14] mm: mempolicy: Check return code of check

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Message-ID: <20100906141813.GB9632@albatros>
Date:	Mon, 6 Sep 2010 18:18:13 +0400
From:	Kulikov Vasiliy <segooon@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	kernel-janitors@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 13/14] mm: mempolicy: Check return code of check_range

On Mon, Sep 06, 2010 at 02:02 -0700, David Rientjes wrote:
> On Mon, 6 Sep 2010, KOSAKI Motohiro wrote:
> 
> > > From: Vasiliy Kulikov <segooon@...il.com>
> > > 
> > > Function check_range may return ERR_PTR(...). Check for it.
> > 
> > When happen this issue?
> > 
> > afaik, check_range return error when following condition.
> >  1) mm->mmap->vm_start argument is incorrect
> >  2) don't have neigher MPOL_MF_STATS, MPOL_MF_MOVE and MPOL_MF_MOVE_ALL
> > 
> > I think both case is not happen in real. Am I overlooking anything?
> > 
> 
> There's no reason not to check the return value of a function when the 
> implementation of either could change at any time.  migrate_to_node() is 
> certainly not in any fastpath where we can't sacrifice a branch for more 
> robust code.

Agreed, if you know that the caller must check input data and must not
check return code, it's better to make this function return void.

-- 
Vasiliy
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