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    Subject[PATCH 03/16] mm: check rb_subtree_gap correctness
    Date
    When CONFIG_DEBUG_VM_RB is enabled, check that rb_subtree_gap is
    correctly set for every vma and that mm->highest_vm_end is also correct.

    Also add an explicit 'bug' variable to track if browse_rb() detected any
    invalid condition.

    Signed-off-by: Michel Lespinasse <walken@google.com>
    Reviewed-by: Rik van Riel <riel@redhat.com>

    ---
    mm/mmap.c | 24 ++++++++++++++++--------
    1 files changed, 16 insertions(+), 8 deletions(-)

    diff --git a/mm/mmap.c b/mm/mmap.c
    index 2de8bcfe859d..769a09cc71af 100644
    --- a/mm/mmap.c
    +++ b/mm/mmap.c
    @@ -365,7 +365,7 @@ static void vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
    #ifdef CONFIG_DEBUG_VM_RB
    static int browse_rb(struct rb_root *root)
    {
    - int i = 0, j;
    + int i = 0, j, bug = 0;
    struct rb_node *nd, *pn = NULL;
    unsigned long prev = 0, pend = 0;

    @@ -373,29 +373,33 @@ static int browse_rb(struct rb_root *root)
    struct vm_area_struct *vma;
    vma = rb_entry(nd, struct vm_area_struct, vm_rb);
    if (vma->vm_start < prev)
    - printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
    + printk("vm_start %lx prev %lx\n", vma->vm_start, prev), bug = 1;
    if (vma->vm_start < pend)
    - printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
    + printk("vm_start %lx pend %lx\n", vma->vm_start, pend), bug = 1;
    if (vma->vm_start > vma->vm_end)
    - printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
    + printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start), bug = 1;
    + if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma))
    + printk("free gap %lx, correct %lx\n",
    + vma->rb_subtree_gap,
    + vma_compute_subtree_gap(vma)), bug = 1;
    i++;
    pn = nd;
    prev = vma->vm_start;
    pend = vma->vm_end;
    }
    j = 0;
    - for (nd = pn; nd; nd = rb_prev(nd)) {
    + for (nd = pn; nd; nd = rb_prev(nd))
    j++;
    - }
    if (i != j)
    - printk("backwards %d, forwards %d\n", j, i), i = 0;
    - return i;
    + printk("backwards %d, forwards %d\n", j, i), bug = 1;
    + return bug ? -1 : i;
    }

    void validate_mm(struct mm_struct *mm)
    {
    int bug = 0;
    int i = 0;
    + unsigned long highest_address = 0;
    struct vm_area_struct *vma = mm->mmap;
    while (vma) {
    struct anon_vma_chain *avc;
    @@ -403,11 +407,15 @@ void validate_mm(struct mm_struct *mm)
    list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
    anon_vma_interval_tree_verify(avc);
    anon_vma_unlock(vma->anon_vma);
    + highest_address = vma->vm_end;
    vma = vma->vm_next;
    i++;
    }
    if (i != mm->map_count)
    printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
    + if (highest_address != mm->highest_vm_end)
    + printk("mm->highest_vm_end %lx, found %lx\n",
    + mm->highest_vm_end, highest_address), bug = 1;
    i = browse_rb(&mm->mm_rb);
    if (i != mm->map_count)
    printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
    --
    1.7.7.3

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