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mm/huge_memory: check pmd_present first in is_huge_zero_pmd 

When pmd is non-present, pmd_pfn returns an insane value. So we should
check pmd_present first to avoid acquiring such insane value and also
avoid touching possible cold huge_zero_pfn cache line when pmd isn't
present.

Link: https://lkml.kernel.org/r/20220704132201.14611-11-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Miaohe Lin 2022-07-04 21:21:55 +08:00 committed by akpm
parent 749290799e
commit 3ce4fee440
1 changed files with 1 additions and 1 deletions
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2
include/linux/huge_mm.h
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@ -273,7 +273,7 @@ static inline bool is_huge_zero_page(struct page *page)
static inline bool is_huge_zero_pmd(pmd_t pmd)
{
return READ_ONCE(huge_zero_pfn) == pmd_pfn(pmd) && pmd_present(pmd);
return pmd_present(pmd) && READ_ONCE(huge_zero_pfn) == pmd_pfn(pmd);
}
static inline bool is_huge_zero_pud(pud_t pud)