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    SubjectRe: [patch 1/3] uml: share page bits handling between 2 and 3 level pagetables
    On Saturday 30 July 2005 18:02, Jeff Dike wrote:
    > On Thu, Jul 28, 2005 at 08:56:53PM +0200, wrote:
    > > As obvious, a "core code nice cleanup" is not a "stability-friendly
    > > patch" so usual care applies.
    > These look reasonable, as they are what we discussed in Ottawa.
    > I'll put them in my tree and see if I see any problems. I would
    > suggest sending these in early after 2.6.13 if they seem OK.
    Just noticed: you can drop them (except the first, which is a nice cleanup).

    set_pte handles that, and include/asm-generic/pgtable.h uses coherently
    set_pte_at. I've checked UML by examining "grep pte", and either mk_pte or
    set_pte are used.

    Exceptions: fixaddr_user_init (but that should be ok as we shouldn't map it
    actually), pte_modify() (which handles that only for present pages).

    But pte_modify is used with set_pte, so probably we could as well drop that

    Also look, on the "set_pte" theme, at the attached patch. I realized this when
    I needed those lines to work - I was getting a segfault loop.

    After using set_pte(), things worked. I have now an almost perfectly working
    implementation of remap_file_pages with protection support.
    There will probably be some other things to update, like swapping locations,
    but I can't get this kernel to fail (it's easier to find bugs in the
    test-program, it grew quite complex).

    And, I'd like to note, original Ingo's version *DID NOT* work properly (it was
    not safe against swapout, it didn't allow write-protecting a page

    I'm going to clean up the code and write changelogs, to send then the patches
    for -mm (hoping the page fault scalability patches don't get in the way).
    Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
    Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)

    From: Paolo 'Blaisorblade' Giarrusso <>

    The PTE returned from handle_mm_fault is already marked as dirty and accessed
    if needed.
    Also, since this is not set with set_pte() (which sets NEWPAGE and NEWPROT as
    needed), this wouldn't work anyway.

    Signed-off-by: Paolo 'Blaisorblade' Giarrusso <>

    linux-2.6.git-paolo/arch/um/kernel/trap_kern.c | 3 +--
    1 files changed, 1 insertion(+), 2 deletions(-)

    diff -puN arch/um/kernel/trap_kern.c~uml-avoid-already-done-dirtying arch/um/kernel/trap_kern.c
    --- linux-2.6.git/arch/um/kernel/trap_kern.c~uml-avoid-already-done-dirtying 2005-08-10 19:21:13.000000000 +0200
    +++ linux-2.6.git-paolo/arch/um/kernel/trap_kern.c 2005-08-10 19:21:13.000000000 +0200
    @@ -83,8 +83,7 @@ survive:
    pte = pte_offset_kernel(pmd, address);
    } while(!pte_present(*pte));
    err = 0;
    - *pte = pte_mkyoung(*pte);
    - if(pte_write(*pte)) *pte = pte_mkdirty(*pte);
    + WARN_ON(!pte_young(*pte) || pte_write(*pte) && !pte_dirty(*pte));
    flush_tlb_page(vma, address);
     \ /
      Last update: 2005-08-12 15:08    [W:0.035 / U:0.044 seconds]
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