Message-Id: <200602220132.k1M1Vxg09552@unix-os.sc.intel.com>
From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
To: "'David Gibson'" <david@gibson.dropbear.id.au>,
       <linux-ia64@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: RE: IA64 non-contiguous memory space bugs
Date: Tue, 21 Feb 2006 17:31:59 -0800
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David Gibson wrote on Tuesday, February 21, 2006 4:14 PM
> Second problem is in the hugepage logic in free_pgtables()
> (mm/memory.c).  As far as I can tell it's complete crap, and only
> works by accident, for different accidental reasons on ppc64 and ia64,
> the only archs that have a non-trivial is_hugepage_only_range().
> Except that I'm not sure it does entirely work by accident on ia64:
> suppose a process has a hugepage mapping that begins some way after
> the beginning of the hugepage address range.  Before
> hugetlb_free_pgd_range() gets called on that area, it will be called
> on the next normal page VMA down - but with an end address at the
> beginning of the hugepage VMA and so extending into the hugepage
> address range.  I don't really understand the ia64 pagetable mapping
> stuff well enough to tell if that's dangerous or not.

I don't see any problem in the ia64 code.  The start and end address is
what the vma specified.  Floor and ceiling is just a hint for free_pgtables()
to free any left over page tables between vma holes (to prev and next).
As far as I can tell, the code looks fine.

- Ken

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