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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 12:16 AM, Joonsoo Kim wrote:
    > On Tue, Jul 07, 2020 at 01:22:31PM +0200, Vlastimil Babka wrote:
    >> On 7/7/20 9:44 AM, js1304@gmail.com wrote:
    >>> From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    >>>
    <...>
    >>> This patch makes the deque function on hugetlb CMA aware and skip CMA
    >>> pages if newly added skip_cma argument is passed as true.
    >>
    >> Hmm, can't you instead change dequeue_huge_page_node_exact() to test the PF_
    >> flag and avoid adding bool skip_cma everywhere?
    >
    > Okay! Please check following patch.
    >>
    >> I think that's what Michal suggested [1] except he said "the code already does
    >> by memalloc_nocma_{save,restore} API". It needs extending a bit though, AFAICS.
    >> __gup_longterm_locked() indeed does the save/restore, but restore comes before
    >> check_and_migrate_cma_pages() and thus new_non_cma_page() is called, so an
    >> adjustment is needed there, but that's all?
    >>
    >> Hm the adjustment should be also done because save/restore is done around
    >> __get_user_pages_locked(), but check_and_migrate_cma_pages() also calls
    >> __get_user_pages_locked(), and that call not being between nocma save and
    >> restore is thus also a correctness issue?
    >
    > Simply, I call memalloc_nocma_{save,restore} in new_non_cma_page(). It
    > would not cause any problem.
    >
    > ------------------>8-------------------
    > From bcfc57e3c6f2df1ad2940308b89d740cd3f0fba8 Mon Sep 17 00:00:00 2001
    > From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    > Date: Wed, 8 Jul 2020 14:39:26 +0900
    > Subject: [PATCH] mm/hugetlb: make hugetlb migration callback CMA aware
    >
    <...>
    >
    > This patch makes new_non_cma_page() uses memalloc_nocma_{save,restore}
    > to exclude CMA memory rather than manually clearing __GFP_MOVABLE. And,
    > this patch also makes the deque function on hugetlb CMA aware. In the
    > deque function, CMA memory is skipped if PF_MEMALLOC_NOCMA flag is set
    > by memalloc_nocma_{save,restore}.
    >
    > Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
    > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

    I did ACK the previous version of the patch, but I like this much better.
    I assume there will be a new version built on top of Michal's patch to
    change the placement of memalloc_nocma_restore calls in __gup_longterm_locked.

    --
    Mike Kravetz

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