From 60fbb14396d5ee1f430c55883d8e603d3229163c Mon Sep 17 00:00:00 2001 From: Gavin Guo Date: Fri, 25 Apr 2025 18:38:58 +0800 Subject: [PATCH] mm/huge_memory: adjust try_to_migrate_one() and split_huge_pmd_locked() Patch series "Clean up split_huge_pmd_locked() and remove unnecessary folio pointers", v2. The patch series enhances the folio verification by leveraging the existing page_vma_mapped_walk() mechanism and removing redundant folio pointer passing. This patch (of 2): split_huge_pmd_locked() currently performs redundant checks for migration entries and folio validation that are already handled by the page_vma_mapped_walk mechanism in try_to_migrate_one. Specifically, page_vma_mapped_walk already ensures that: - The folio is properly mapped in the given VMA area - pmd_trans_huge, pmd_devmap, and migration entry validation are performed To leverage page_vma_mapped_walk's work, moving TTU_SPLIT_HUGE_PMD handling to the while loop checking and removing these duplicate checks from split_huge_pmd_locked. Link: https://lkml.kernel.org/r/20250425103859.825879-1-gavinguo@igalia.com Link: https://lkml.kernel.org/r/20250425103859.825879-2-gavinguo@igalia.com Link: https://lore.kernel.org/all/98d1d195-7821-4627-b518-83103ade56c0@redhat.com/ Link: https://lore.kernel.org/all/91599a3c-e69e-4d79-bac5-5013c96203d7@redhat.com/ Signed-off-by: Gavin Guo Suggested-by: David Hildenbrand Acked-by: David Hildenbrand Reviewed-by: Zi Yan Reviewed-by: Baolin Wang Cc: Florent Revest Cc: Gavin Shan Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Signed-off-by: Andrew Morton --- mm/huge_memory.c | 21 ++------------------- mm/rmap.c | 18 +++++++++--------- 2 files changed, 11 insertions(+), 28 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index fdcf0a6049b9f..d8a5bb6020082 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3082,27 +3082,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, bool freeze, struct folio *folio) { - bool pmd_migration = is_pmd_migration_entry(*pmd); - - VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio)); VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE)); - VM_WARN_ON_ONCE(folio && !folio_test_locked(folio)); - VM_BUG_ON(freeze && !folio); - - /* - * When the caller requests to set up a migration entry, we - * require a folio to check the PMD against. Otherwise, there - * is a risk of replacing the wrong folio. - */ - if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || pmd_migration) { - /* - * Do not apply pmd_folio() to a migration entry; and folio lock - * guarantees that it must be of the wrong folio anyway. - */ - if (folio && (pmd_migration || folio != pmd_folio(*pmd))) - return; + if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || + is_pmd_migration_entry(*pmd)) __split_huge_pmd_locked(vma, pmd, address, freeze); - } } void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, diff --git a/mm/rmap.c b/mm/rmap.c index 67bb273dfb80d..b53a4dcaeaaef 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2291,13 +2291,6 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, if (flags & TTU_SYNC) pvmw.flags = PVMW_SYNC; - /* - * unmap_page() in mm/huge_memory.c is the only user of migration with - * TTU_SPLIT_HUGE_PMD and it wants to freeze. - */ - if (flags & TTU_SPLIT_HUGE_PMD) - split_huge_pmd_address(vma, address, true, folio); - /* * For THP, we have to assume the worse case ie pmd for invalidation. * For hugetlb, it could be much worse if we need to do pud @@ -2323,9 +2316,16 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, mmu_notifier_invalidate_range_start(&range); while (page_vma_mapped_walk(&pvmw)) { -#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION /* PMD-mapped THP migration entry */ if (!pvmw.pte) { + if (flags & TTU_SPLIT_HUGE_PMD) { + split_huge_pmd_locked(vma, pvmw.address, + pvmw.pmd, true, NULL); + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION subpage = folio_page(folio, pmd_pfn(*pvmw.pmd) - folio_pfn(folio)); VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) || @@ -2337,8 +2337,8 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, break; } continue; - } #endif + } /* Unexpected PMD-mapped THP? */ VM_BUG_ON_FOLIO(!pvmw.pte, folio); -- 2.39.5