[lkml]   [2006]   [Feb]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    Patch in this message
    SubjectRE: IA64 non-contiguous memory space bugs
    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.

    Chen, Kenneth W wrote on Tuesday, February 21, 2006 5:32 PM
    > 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.

    free_pgtables() has partial crap that the check of is_hugepage_only_range()
    should be done on the entire vma range, not just the first hugetlb page.
    Though, it's not possible to have a hugetlb vma while having normal page
    instantiated inside that vma. So the bug is mostly phantom. For
    correctness, it should be fixed.

    --- linux-2.6.16-rc4/mm/memory.c.orig 2006-02-21 18:33:32.427186571 -0800
    +++ linux-2.6.16-rc4/mm/memory.c 2006-02-21 18:37:22.414488441 -0800
    @@ -270,6 +270,7 @@ void free_pgtables(struct mmu_gather **t
    while (vma) {
    struct vm_area_struct *next = vma->vm_next;
    unsigned long addr = vma->vm_start;
    + unsigned long end = vma->vm_end;

    * Hide vma from rmap and vmtruncate before freeing pgtables
    @@ -277,8 +278,8 @@ void free_pgtables(struct mmu_gather **t

    - if (is_hugepage_only_range(vma->vm_mm, addr, HPAGE_SIZE)) {
    - hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
    + if (is_hugepage_only_range(vma->vm_mm, addr, end - addr)) {
    + hugetlb_free_pgd_range(tlb, addr, end
    floor, next? next->vm_start: ceiling);
    } else {

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2006-02-22 02:54    [W:0.021 / U:1.452 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site