Messages in this thread Patch in this message | | | From | Miaohe Lin <> | Subject | [PATCH v3 15/16] mm/huge_memory: comment the subtly logic in __split_huge_pmd | Date | Mon, 4 Jul 2022 21:22:00 +0800 |
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It's dangerous and wrong to call page_folio(pmd_page(*pmd)) when pmd isn't present. But the caller guarantees pmd is present when folio is set. So we should be safe here. Add comment to make it clear.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> --- mm/huge_memory.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 36f3fc2e7306..8380912b39fd 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2336,6 +2336,10 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)) { + /* + * It's safe to call pmd_page when folio is set because it's + * guaranteed that pmd is present. + */ if (folio && folio != page_folio(pmd_page(*pmd))) goto out; __split_huge_pmd_locked(vma, pmd, range.start, freeze); -- 2.23.0
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