lkml.org 
[lkml]   [2020]   [Aug]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.8 077/232] khugepaged: collapse_pte_mapped_thp() flush the right range
    Date
    From: Hugh Dickins <hughd@google.com>

    commit 723a80dafed5c95889d48baab9aa433a6ffa0b4e upstream.

    pmdp_collapse_flush() should be given the start address at which the huge
    page is mapped, haddr: it was given addr, which at that point has been
    used as a local variable, incremented to the end address of the extent.

    Found by source inspection while chasing a hugepage locking bug, which I
    then could not explain by this. At first I thought this was very bad;
    then saw that all of the page translations that were not flushed would
    actually still point to the right pages afterwards, so harmless; then
    realized that I know nothing of how different architectures and models
    cache intermediate paging structures, so maybe it matters after all -
    particularly since the page table concerned is immediately freed.

    Much easier to fix than to think about.

    Fixes: 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP")
    Signed-off-by: Hugh Dickins <hughd@google.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Mike Kravetz <mike.kravetz@oracle.com>
    Cc: Song Liu <songliubraving@fb.com>
    Cc: <stable@vger.kernel.org> [5.4+]
    Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008021204390.27773@eggly.anvils
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    mm/khugepaged.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/mm/khugepaged.c
    +++ b/mm/khugepaged.c
    @@ -1502,7 +1502,7 @@ void collapse_pte_mapped_thp(struct mm_s

    /* step 4: collapse pmd */
    ptl = pmd_lock(vma->vm_mm, pmd);
    - _pmd = pmdp_collapse_flush(vma, addr, pmd);
    + _pmd = pmdp_collapse_flush(vma, haddr, pmd);
    spin_unlock(ptl);
    mm_dec_nr_ptes(mm);
    pte_free(mm, pmd_pgtable(_pmd));

    \
     
     \ /
      Last update: 2020-08-20 11:28    [W:4.020 / U:0.540 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site