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    SubjectRe: [PATCH v4 55/66] mm/mempolicy: Use maple tree iterators instead of vma linked list
    On 12/1/21 15:30, Liam Howlett wrote:
    > From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
    >
    > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
    > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
    > ---
    > mm/mempolicy.c | 53 ++++++++++++++++++++++++++------------------------
    > 1 file changed, 28 insertions(+), 25 deletions(-)
    >
    > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
    > index 10e9c87260ed..0e2d918f4f30 100644
    > --- a/mm/mempolicy.c
    > +++ b/mm/mempolicy.c
    > @@ -377,9 +377,10 @@ void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *new)
    > void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
    > {
    > struct vm_area_struct *vma;
    > + MA_STATE(mas, &mm->mm_mt, 0, 0);

    VMA_ITERATOR?

    >
    > mmap_write_lock(mm);
    > - for (vma = mm->mmap; vma; vma = vma->vm_next)
    > + mas_for_each(&mas, vma, ULONG_MAX)
    > mpol_rebind_policy(vma->vm_policy, new);
    > mmap_write_unlock(mm);
    > }
    > @@ -652,7 +653,7 @@ static unsigned long change_prot_numa(struct vm_area_struct *vma,
    > static int queue_pages_test_walk(unsigned long start, unsigned long end,
    > struct mm_walk *walk)
    > {
    > - struct vm_area_struct *vma = walk->vma;
    > + struct vm_area_struct *next, *vma = walk->vma;
    > struct queue_pages *qp = walk->private;
    > unsigned long endvma = vma->vm_end;
    > unsigned long flags = qp->flags;
    > @@ -667,9 +668,10 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
    > /* hole at head side of range */
    > return -EFAULT;
    > }
    > + next = find_vma(vma->vm_mm, vma->vm_end);
    > if (!(flags & MPOL_MF_DISCONTIG_OK) &&
    > ((vma->vm_end < qp->end) &&
    > - (!vma->vm_next || vma->vm_end < vma->vm_next->vm_start)))
    > + (!next || vma->vm_end < next->vm_start)))
    > /* hole at middle or tail of range */
    > return -EFAULT;
    >
    > @@ -783,28 +785,24 @@ static int vma_replace_policy(struct vm_area_struct *vma,
    > static int mbind_range(struct mm_struct *mm, unsigned long start,
    > unsigned long end, struct mempolicy *new_pol)
    > {
    > - struct vm_area_struct *next;
    > + MA_STATE(mas, &mm->mm_mt, start - 1, start - 1);
    > struct vm_area_struct *prev;
    > struct vm_area_struct *vma;
    > int err = 0;
    > pgoff_t pgoff;
    > - unsigned long vmstart;
    > - unsigned long vmend;
    > -
    > - vma = find_vma(mm, start);
    > - VM_BUG_ON(!vma);
    >
    > - prev = vma->vm_prev;
    > - if (start > vma->vm_start)
    > - prev = vma;
    > + prev = mas_find_rev(&mas, 0);
    > + if (prev && (start < prev->vm_end))
    > + vma = prev;
    > + else
    > + vma = mas_next(&mas, end - 1);
    >
    > - for (; vma && vma->vm_start < end; prev = vma, vma = next) {
    > - next = vma->vm_next;
    > - vmstart = max(start, vma->vm_start);
    > - vmend = min(end, vma->vm_end);
    > + do {
    > + unsigned long vmstart = max(start, vma->vm_start);
    > + unsigned long vmend = min(end, vma->vm_end);

    What if vma is null? Shouldn't this rather be a "for (; vma; vma =
    mas_next(...)"

    >
    > if (mpol_equal(vma_policy(vma), new_pol))
    > - continue;
    > + goto next;
    >
    > pgoff = vma->vm_pgoff +
    > ((vmstart - vma->vm_start) >> PAGE_SHIFT);
    > @@ -812,8 +810,8 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
    > vma->anon_vma, vma->vm_file, pgoff,
    > new_pol, vma->vm_userfaultfd_ctx);
    > if (prev) {
    > + mas_pause(&mas);
    > vma = prev;
    > - next = vma->vm_next;
    > if (mpol_equal(vma_policy(vma), new_pol))
    > continue;
    > /* vma_merge() joined vma && vma->next, case 8 */
    > @@ -823,19 +821,23 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
    > err = split_vma(vma->vm_mm, vma, vmstart, 1);
    > if (err)
    > goto out;
    > + mas_pause(&mas);
    > }
    > if (vma->vm_end != vmend) {
    > err = split_vma(vma->vm_mm, vma, vmend, 0);
    > if (err)
    > goto out;
    > + /* mas_pause() unnecessary as the loop is ending */
    > }
    > - replace:
    > +replace:
    > err = vma_replace_policy(vma, new_pol);
    > if (err)
    > goto out;
    > - }
    > +next:
    > + prev = vma;
    > + } while ((vma = mas_next(&mas, end - 1)) != NULL);
    >
    > - out:
    > +out:
    > return err;
    > }
    >
    > @@ -1053,6 +1055,7 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
    > int flags)
    > {
    > nodemask_t nmask;
    > + struct vm_area_struct *vma;
    > LIST_HEAD(pagelist);
    > int err = 0;
    > struct migration_target_control mtc = {
    > @@ -1068,8 +1071,9 @@ static int migrate_to_node(struct mm_struct *mm, int source, int dest,
    > * need migration. Between passing in the full user address
    > * space range and MPOL_MF_DISCONTIG_OK, this call can not fail.
    > */
    > + vma = find_vma(mm, 0);
    > VM_BUG_ON(!(flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)));
    > - queue_pages_range(mm, mm->mmap->vm_start, mm->task_size, &nmask,
    > + queue_pages_range(mm, vma->vm_start, mm->task_size, &nmask,
    > flags | MPOL_MF_DISCONTIG_OK, &pagelist);
    >
    > if (!list_empty(&pagelist)) {
    > @@ -1198,13 +1202,12 @@ static struct page *new_page(struct page *page, unsigned long start)
    > {
    > struct vm_area_struct *vma;
    > unsigned long address;
    > + MA_STATE(mas, &current->mm->mm_mt, start, start);
    >
    > - vma = find_vma(current->mm, start);
    > - while (vma) {
    > + mas_for_each(&mas, vma, ULONG_MAX) {
    > address = page_address_in_vma(page, vma);
    > if (address != -EFAULT)
    > break;
    > - vma = vma->vm_next;
    > }
    >
    > if (PageHuge(page)) {

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