From: Lance Yang ioworker0@gmail.com
mainline inclusion from mainline-v6.11-rc1 commit 29e847d2ade3cdff36afe095fdbeb9b5f71a197a category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IAIHQO
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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In preparation for supporting try_to_unmap_one() to unmap PMD-mapped folios, start the pagewalk first, then call split_huge_pmd_address() to split the folio.
Link: https://lkml.kernel.org/r/20240614015138.31461-3-ioworker0@gmail.com Signed-off-by: Lance Yang ioworker0@gmail.com Suggested-by: David Hildenbrand david@redhat.com Acked-by: David Hildenbrand david@redhat.com Suggested-by: Baolin Wang baolin.wang@linux.alibaba.com Acked-by: Zi Yan ziy@nvidia.com Cc: Bang Li libang.li@antgroup.com Cc: Barry Song baohua@kernel.org Cc: Fangrui Song maskray@google.com Cc: Jeff Xie xiehuan09@gmail.com Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Michal Hocko mhocko@suse.com Cc: Minchan Kim minchan@kernel.org Cc: Muchun Song songmuchun@bytedance.com Cc: Peter Xu peterx@redhat.com Cc: Ryan Roberts ryan.roberts@arm.com Cc: SeongJae Park sj@kernel.org Cc: Yang Shi shy828301@gmail.com Cc: Yin Fengwei fengwei.yin@intel.com Cc: Zach O'Keefe zokeefe@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Liu Shixin liushixin2@huawei.com --- include/linux/huge_mm.h | 6 ++++++ include/linux/rmap.h | 24 +++++++++++++++++++++++ mm/huge_memory.c | 42 +++++++++++++++++++++-------------------- mm/rmap.c | 21 +++++++++++++++------ 4 files changed, 67 insertions(+), 26 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 614b50b1707a..37eadd0ce2b9 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -413,6 +413,9 @@ static inline bool thp_migration_supported(void) return IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION); }
+void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmd, bool freeze, struct folio *folio); + #else /* CONFIG_TRANSPARENT_HUGEPAGE */
static inline bool folio_test_pmd_mappable(struct folio *folio) @@ -471,6 +474,9 @@ static inline void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, unsigned long address, bool freeze, struct folio *folio) {} static inline void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, bool freeze, struct folio *folio) {} +static inline void split_huge_pmd_locked(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd, + bool freeze, struct folio *folio) {}
#define split_huge_pud(__vma, __pmd, __address) \ do { } while (0) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 23d7a6260266..43cdb662ce06 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -697,6 +697,30 @@ static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw) spin_unlock(pvmw->ptl); }
+/** + * page_vma_mapped_walk_restart - Restart the page table walk. + * @pvmw: Pointer to struct page_vma_mapped_walk. + * + * It restarts the page table walk when changes occur in the page + * table, such as splitting a PMD. Ensures that the PTL held during + * the previous walk is released and resets the state to allow for + * a new walk starting at the current address stored in pvmw->address. + */ +static inline void +page_vma_mapped_walk_restart(struct page_vma_mapped_walk *pvmw) +{ + WARN_ON_ONCE(!pvmw->pmd && !pvmw->pte); + + if (likely(pvmw->ptl)) + spin_unlock(pvmw->ptl); + else + WARN_ON_ONCE(1); + + pvmw->ptl = NULL; + pvmw->pmd = NULL; + pvmw->pte = NULL; +} + bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
/* diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 47f249c1bf7a..1fed4ce3fb95 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2766,6 +2766,27 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, pmd_populate(mm, pmd, pgtable); }
+void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmd, bool freeze, struct folio *folio) +{ + 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) || + is_pmd_migration_entry(*pmd)) { + if (folio && folio != pmd_folio(*pmd)) + return; + __split_huge_pmd_locked(vma, pmd, address, freeze); + } +} + void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, unsigned long address, bool freeze, struct folio *folio) { @@ -2777,26 +2798,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE); mmu_notifier_invalidate_range_start(&range); ptl = pmd_lock(vma->vm_mm, pmd); - - /* - * If caller asks to setup a migration entry, we need a folio to check - * pmd against. Otherwise we can end up replacing wrong folio. - */ - VM_BUG_ON(freeze && !folio); - VM_WARN_ON_ONCE(folio && !folio_test_locked(folio)); - - 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 != pmd_folio(*pmd)) - goto out; - __split_huge_pmd_locked(vma, pmd, range.start, freeze); - } - -out: + split_huge_pmd_locked(vma, range.start, pmd, freeze, folio); spin_unlock(ptl); mmu_notifier_invalidate_range_end(&range); } diff --git a/mm/rmap.c b/mm/rmap.c index f427c34dbd13..5941a7c09260 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1617,9 +1617,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, if (flags & TTU_SYNC) pvmw.flags = PVMW_SYNC;
- if (flags & TTU_SPLIT_HUGE_PMD) - split_huge_pmd_address(vma, address, false, 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 @@ -1645,9 +1642,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, mmu_notifier_invalidate_range_start(&range);
while (page_vma_mapped_walk(&pvmw)) { - /* Unexpected PMD-mapped THP? */ - VM_BUG_ON_FOLIO(!pvmw.pte, folio); - /* * If the folio is in an mlock()d vma, we must not swap it out. */ @@ -1659,6 +1653,21 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, goto walk_abort; }
+ if (!pvmw.pte && (flags & TTU_SPLIT_HUGE_PMD)) { + /* + * We temporarily have to drop the PTL and start once + * again from that now-PTE-mapped page table. + */ + split_huge_pmd_locked(vma, pvmw.address, pvmw.pmd, + false, folio); + flags &= ~TTU_SPLIT_HUGE_PMD; + page_vma_mapped_walk_restart(&pvmw); + continue; + } + + /* Unexpected PMD-mapped THP? */ + VM_BUG_ON_FOLIO(!pvmw.pte, folio); + pfn = pte_pfn(ptep_get(pvmw.pte)); subpage = folio_page(folio, pfn - folio_pfn(folio)); address = pvmw.address;