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    SubjectRe: [PATCH v4 04/11] mm/hugetlb: make hugetlb migration callback CMA aware
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    On 7/8/20 9:41 AM, Michal Hocko wrote:
    > On Wed 08-07-20 16:16:02, Joonsoo Kim wrote:
    >> On Tue, Jul 07, 2020 at 01:22:31PM +0200, Vlastimil Babka wrote:
    >>
    >> Simply, I call memalloc_nocma_{save,restore} in new_non_cma_page(). It
    >> would not cause any problem.
    >
    > I believe a proper fix is the following. The scope is really defined for
    > FOLL_LONGTERM pins and pushing it inside check_and_migrate_cma_pages
    > will solve the problem as well but it imho makes more sense to do it in
    > the caller the same way we do for any others.
    >
    > Fixes: 9a4e9f3b2d73 ("mm: update get_user_pages_longterm to migrate pages allocated from CMA region")

    Agreed.

    >
    > I am not sure this is worth backporting to stable yet.

    CC Aneesh.

    Context: since check_and_migrate_cma_pages() calls __get_user_pages_locked(), it
    should also be called under memalloc_nocma_save().

    > diff --git a/mm/gup.c b/mm/gup.c
    > index de9e36262ccb..75980dd5a2fc 100644
    > --- a/mm/gup.c
    > +++ b/mm/gup.c
    > @@ -1794,7 +1794,6 @@ static long __gup_longterm_locked(struct task_struct *tsk,
    > vmas_tmp, NULL, gup_flags);
    >
    > if (gup_flags & FOLL_LONGTERM) {
    > - memalloc_nocma_restore(flags);
    > if (rc < 0)
    > goto out;
    >
    > @@ -1802,11 +1801,13 @@ static long __gup_longterm_locked(struct task_struct *tsk,
    > for (i = 0; i < rc; i++)
    > put_page(pages[i]);
    > rc = -EOPNOTSUPP;
    > + memalloc_nocma_restore(flags);
    > goto out;
    > }
    >
    > rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages,
    > vmas_tmp, gup_flags);
    > + memalloc_nocma_restore(flags);
    > }
    >
    > out:
    >

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