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From: David Rientjes <rientjes@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
	Andi Kleen <andi@firstfloor.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: mempolicy: turn vma_set_policy() into vma_dup_policy()
Date: Thu, 11 Jul 2013 15:27:46 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.02.1307111524400.2458@chino.kir.corp.google.com> (raw)
In-Reply-To: <20130711152006.de0900cfcd784f2833285ee4@linux-foundation.org>

On Thu, 11 Jul 2013, Andrew Morton wrote:

> On Thu, 11 Jul 2013 15:13:03 -0700 (PDT) David Rientjes <rientjes@google.com> wrote:
> 
> > > +int vma_dup_policy(struct vm_area_struct *src, struct vm_area_struct *dst)
> > > +{
> > > +	struct mempolicy *pol = mpol_dup(vma_policy(src));
> > > +
> > > +	if (IS_ERR(pol))
> > > +		return PTR_ERR(pol);
> > 
> > PTR_ERR() returns long, so vma_dup_policy() needs to return long.
> 
> hm, really?  vma_dup_policy() returns an errno and errnos have type "int".
> 
> Arguably it is PTR_ERR() which returns the wrong type...
> 

PTR_ERR() may not imply IS_ERR(), which I believe Rusty is trying to fix 
with his series that fixes up abuses of PTR_ERR().  But I agree that 
vma_dup_policy() can return int because of the IS_ERR() check as written.  

For complete correctness there should probably be a build error if 
MAX_ERRNO cannot fit in an int and then this should do 
return (int)PTR_ERR(pol) to make it clear.

  reply	other threads:[~2013-07-11 22:27 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-10 17:02 [PATCH] mm: mempolicy: turn vma_set_policy() into vma_dup_policy() Oleg Nesterov
2013-07-11 22:13 ` David Rientjes
2013-07-11 22:20   ` Andrew Morton
2013-07-11 22:27     ` David Rientjes [this message]
2013-07-11 22:33       ` Andrew Morton
2013-07-11 22:54         ` David Rientjes
2013-07-12 15:32   ` Oleg Nesterov

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