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

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Message-Id: <1224523278.1848.123.camel@nimitz>
Date:	Mon, 20 Oct 2008 10:21:18 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Andrey Mirkin <major@...nvz.org>
Cc:	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [PATCH 06/10] Introduce functions to dump mm

On Sat, 2008-10-18 at 03:11 +0400, Andrey Mirkin wrote:
> +static void page_get_desc(struct vm_area_struct *vma, unsigned long addr,
> +                         struct page_desc *pdesc, cpt_context_t * ctx)
> +{
> +       struct mm_struct *mm = vma->vm_mm;
> +       pgd_t *pgd;
> +       pud_t *pud;
> +       pmd_t *pmd;
> +       pte_t *ptep, pte;
> +       spinlock_t *ptl;
> +       struct page *pg = NULL;
> +       pgoff_t linear_index = (addr - vma->vm_start)/PAGE_SIZE + vma->vm_pgoff;
> +
> +       pdesc->index = linear_index;
> +       pdesc->shared = 0;
> +       pdesc->mm = CPT_NULL;
> +
> +       if (vma->vm_flags & VM_IO) {
> +               pdesc->type = PD_ABSENT;
> +               return;
> +       }
> +
> +       pgd = pgd_offset(mm, addr);
> +       if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
> +               goto out_absent;
> +       pud = pud_offset(pgd, addr);
> +       if (pud_none(*pud) || unlikely(pud_bad(*pud)))
> +               goto out_absent;
> +       pmd = pmd_offset(pud, addr);
> +       if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
> +               goto out_absent;
> +#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()?

-- Dave

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