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    SubjectRe: [PATCH] fix update_mmu_cache in fremap.c
    On Fri, 26 May 2006, David Miller wrote:
    > From: Hugh Dickins <hugh@veritas.com>
    > Date: Fri, 26 May 2006 19:28:14 +0100 (BST)
    >
    > > There are two calls to update_mmu_cache in fremap.c, both defective.
    > > The one in install_page needs to be accompanied by lazy_mmu_prot_update
    > > (some other cleanup time, move that into ia64 update_mmu_cache itself); and
    > > the one in install_file_pte should be removed since the pte is not present.
    > >
    > > Signed-off-by: Hugh Dickins <hugh@veritas.com>
    >
    > Where did that rule come from? We should call update_mmu_cache() even
    > if the PTE was not present before, look at the fault path in
    > mm/memory.c, it does this too.
    >
    > This is where we install hash table entries for newly installed
    > mappings on sparc64 and powerpc, so this update_mmu_cache() call
    > is important even for not-previously-present mappings.

    Sure it's important for not-previously-present mappings, when you're
    installing a present pte. But the "file pte" being installed by
    install_file_pte is not a real pte - it's a non-present entry (like
    a swap entry), noting what file offset should be mapped there when
    there's a fault (in a non-linear vma where that's not obvious).

    Hugh
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