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SubjectRe: [PATCH] mm/hugetlb: Remove redundant VM_BUG_ON_PAGE on putback_active_hugepage()
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On 2/8/21 12:37 AM, Miaohe Lin wrote:
> PageHead(page) is implicitly checked in set_page_huge_active() via the
> PageHeadHuge(page) check. So remove this explicit one.

I do not disagree with the code change. However, this commit message
is not accurate. set_page_huge_active() no longer exists in the tree
you are changing. It was replaced with SetHPageMigratable. Also, the
VM_BUG_ON_PAGE(!PageHeadHuge(page), page) was removed in the process.
So, there is no redundant check.

However, a quick audit of calling code reveals that all callers know they
are operating on a hugetlb head page.
--
Mike Kravetz

>
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> mm/hugetlb.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 6cdb59d8f663..bbbe013a3a2d 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -5577,7 +5577,6 @@ bool isolate_huge_page(struct page *page, struct list_head *list)
>
> void putback_active_hugepage(struct page *page)
> {
> - VM_BUG_ON_PAGE(!PageHead(page), page);
> spin_lock(&hugetlb_lock);
> SetHPageMigratable(page);
> list_move_tail(&page->lru, &(page_hstate(page))->hugepage_activelist);
>

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