linux-kernel - Re: [Devel] Re: [PATCH 06/10] Introduce functions to dump mm

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Message-Id: <1224769880.12673.15.camel@nimitz>
Date:	Thu, 23 Oct 2008 06:51:20 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Andrey Mirkin <major@...nvz.org>
Cc:	devel@...nvz.org, containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [Devel] Re: [PATCH 06/10] Introduce functions to dump mm

On Thu, 2008-10-23 at 12:43 +0400, Andrey Mirkin wrote:
> > > +#ifdef CONFIG_X86
> > > +       if (pmd_huge(*pmd)) {
> > > +               eprintk("page_huge\n");
> > > +               goto out_unsupported;
> > > +       }
> > > +#endif
> >
> > I take it you know that this breaks with the 1GB (x86_64) and 16GB (ppc)
> > large pages.
> >
> > Since you have the VMA, why not use is_vm_hugetlb_page()?
> Right now I'm checking VM_HUGETLB flag on VMAs in dump_one_vma().
> This checks were added for sanity purpose just to throw out all unsupported 
> right now cases.

I'm telling you that it's no good.  Not only should this path never be
hit.  But, if it is, you'll crash anyway in some cases.

It's a bad check.  At best it misleads the reader to think that you've
covered your bases.

-- Dave

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