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SubjectRe: [PATCH 06/11] mm/hugetlb: do not modify user provided gfp_mask
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On 5/17/20 6:20 PM, js1304@gmail.com 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.

Modifying the flags as is done in the existing code does not bother me
too much, but that is just my opinion. Adding __gfp_mask for modifications
is fine with me if others think it is a good thing.

Does dequeue_huge_page_vma() need to be modified so that it will set
ac.__gfp_mask before calling dequeue_huge_page_nodemask()?
--
Mike Kravetz

>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> ---
> mm/hugetlb.c | 15 ++++++++-------
> mm/internal.h | 2 ++
> 2 files changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 53edd02..5f43b7e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1069,15 +1069,15 @@ 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
> @@ -1952,7 +1952,7 @@ 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;
> @@ -1990,9 +1990,10 @@ 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->thisnode && 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) {
> @@ -2011,7 +2012,7 @@ 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 6b6507e..3239d71 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -620,6 +620,8 @@ struct alloc_control {
> gfp_t gfp_mask;
> bool thisnode;
> bool skip_cma;
> +
> + gfp_t __gfp_mask; /* Used internally in API implementation */
> };
>
> #endif /* __MM_INTERNAL_H */
>

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