linux-kernel - Re: + memblock-add-assertion-for-zero-allocation-alignment.patch added to -mm tree

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Message-Id: <20130306161619.0b8e3674d91bc3b5f1927813@linux-foundation.org>
Date:	Wed, 6 Mar 2013 16:16:19 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Vineet.Gupta1@...opsys.com,
	liwanp@...ux.vnet.ibm.com, mingo@...nel.org, tj@...nel.org,
	vgupta@...opsys.com
Subject: Re: + memblock-add-assertion-for-zero-allocation-alignment.patch
 added to -mm tree

On Wed, 6 Mar 2013 16:07:20 -0800 Yinghai Lu <yinghai@...nel.org> wrote:

> > --- a/mm/memblock.c~memblock-add-assertion-for-zero-allocation-alignment
> > +++ a/mm/memblock.c
> > @@ -771,6 +771,9 @@ static phys_addr_t __init memblock_alloc
> >  {
> >         phys_addr_t found;
> >
> > +       if (WARN_ON(!align))
> > +               align = __alignof__(long long);
> > +
> >         /* align @size to avoid excessive fragmentation on reserved array */
> >         size = round_up(size, align);
> 
> Hi, Peter,
> 
> Do you agree that we should check align in round_up()?

As you don't describe your reasoning it is hard to say.

But no, I don't think so.  Checking for zero would add a pile of
basically useless code to the 100+ round_up() callsites, and
round_up(x, 0) is kinda meaningful, in a strange way.

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