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    SubjectRe: [PATCH v2 07/12] mm/hugetlb: do not modify user provided gfp_mask
    On Wed 27-05-20 15:44:58, Joonsoo Kim wrote:
    > From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    >
    > It's not good practice to modify user input. Instead of using it to
    > build correct gfp_mask for APIs, this patch introduces another gfp_mask
    > field, __gfp_mask, for internal usage.

    Ugh, this is really ugly. It is just hugetlb to add __GFP_THISNODE as a
    special case. This is an ugly hack but I do not think we want to work
    around it by yet another hack. Moreover it seems that the __GFP_THISNODE
    might be not needed anymore as pointed out in a reply to earlier patch.

    > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    > ---
    > mm/hugetlb.c | 19 ++++++++++---------
    > mm/internal.h | 2 ++
    > 2 files changed, 12 insertions(+), 9 deletions(-)
    >
    > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
    > index e465582..4757e72 100644
    > --- a/mm/hugetlb.c
    > +++ b/mm/hugetlb.c
    > @@ -1068,15 +1068,15 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h,
    > struct zoneref *z;
    > int node = NUMA_NO_NODE;
    >
    > - zonelist = node_zonelist(ac->nid, ac->gfp_mask);
    > + zonelist = node_zonelist(ac->nid, ac->__gfp_mask);
    >
    > retry_cpuset:
    > cpuset_mems_cookie = read_mems_allowed_begin();
    > for_each_zone_zonelist_nodemask(zone, z, zonelist,
    > - gfp_zone(ac->gfp_mask), ac->nmask) {
    > + gfp_zone(ac->__gfp_mask), ac->nmask) {
    > struct page *page;
    >
    > - if (!cpuset_zone_allowed(zone, ac->gfp_mask))
    > + if (!cpuset_zone_allowed(zone, ac->__gfp_mask))
    > continue;
    > /*
    > * no need to ask again on the same node. Pool is node rather than
    > @@ -1127,8 +1127,8 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
    > if (avoid_reserve && h->free_huge_pages - h->resv_huge_pages == 0)
    > goto err;
    >
    > - ac.gfp_mask = htlb_alloc_mask(h);
    > - ac.nid = huge_node(vma, address, ac.gfp_mask, &mpol, &ac.nmask);
    > + ac.__gfp_mask = htlb_alloc_mask(h);
    > + ac.nid = huge_node(vma, address, ac.__gfp_mask, &mpol, &ac.nmask);
    >
    > page = dequeue_huge_page_nodemask(h, &ac);
    > if (page && !avoid_reserve && vma_has_reserves(vma, chg)) {
    > @@ -1951,7 +1951,7 @@ static struct page *alloc_migrate_huge_page(struct hstate *h,
    > if (hstate_is_gigantic(h))
    > return NULL;
    >
    > - page = alloc_fresh_huge_page(h, ac->gfp_mask,
    > + page = alloc_fresh_huge_page(h, ac->__gfp_mask,
    > ac->nid, ac->nmask, NULL);
    > if (!page)
    > return NULL;
    > @@ -1989,9 +1989,10 @@ struct page *alloc_buddy_huge_page_with_mpol(struct hstate *h,
    > struct page *alloc_huge_page_nodemask(struct hstate *h,
    > struct alloc_control *ac)
    > {
    > - ac->gfp_mask |= htlb_alloc_mask(h);
    > + ac->__gfp_mask = htlb_alloc_mask(h);
    > + ac->__gfp_mask |= ac->gfp_mask;
    > if (ac->nid == NUMA_NO_NODE)
    > - ac->gfp_mask &= ~__GFP_THISNODE;
    > + ac->__gfp_mask &= ~__GFP_THISNODE;
    >
    > spin_lock(&hugetlb_lock);
    > if (h->free_huge_pages - h->resv_huge_pages > 0) {
    > @@ -2010,7 +2011,7 @@ struct page *alloc_huge_page_nodemask(struct hstate *h,
    > * will not come from CMA area
    > */
    > if (ac->skip_cma)
    > - ac->gfp_mask &= ~__GFP_MOVABLE;
    > + ac->__gfp_mask &= ~__GFP_MOVABLE;
    >
    > return alloc_migrate_huge_page(h, ac);
    > }
    > diff --git a/mm/internal.h b/mm/internal.h
    > index 159cfd6..2dc0268 100644
    > --- a/mm/internal.h
    > +++ b/mm/internal.h
    > @@ -619,6 +619,8 @@ struct alloc_control {
    > nodemask_t *nmask;
    > gfp_t gfp_mask;
    > bool skip_cma;
    > +
    > + gfp_t __gfp_mask; /* Used internally in API implementation */
    > };
    >
    > #endif /* __MM_INTERNAL_H */
    > --
    > 2.7.4

    --
    Michal Hocko
    SUSE Labs

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