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    SubjectRe: IA64 non-contiguous memory space bugs
    On Tue, Feb 21, 2006 at 05:31:59PM -0800, Chen, Kenneth W wrote:
    > 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.

    Ah, yes, I see now. free_pgd_range() only iterates through to end,
    not ceiling so it should be fine.

    --
    David Gibson | I'll have my music baroque, and my code
    david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
    | _way_ _around_!
    http://www.ozlabs.org/~dgibson
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