diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 72b5d3671abc..acbb925b0123 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1228,22 +1228,24 @@ static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_stru * while allocating a THP, as that could trigger direct reclaim/compaction. * Note that the VMA must be rechecked after grabbing the mmap_lock again. */ -static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long address, - int referenced, int unmapped, struct collapse_control *cc) +static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long start_addr, + int referenced, int unmapped, struct collapse_control *cc, + unsigned int order) { + const unsigned long pmd_addr = start_addr & HPAGE_PMD_MASK; + const unsigned long end_addr = start_addr + (PAGE_SIZE << order); LIST_HEAD(compound_pagelist); pmd_t *pmd, _pmd; - pte_t *pte; + pte_t *pte = NULL; pgtable_t pgtable; struct folio *folio; spinlock_t *pmd_ptl, *pte_ptl; enum scan_result result = SCAN_FAIL; struct vm_area_struct *vma; struct mmu_notifier_range range; + bool anon_vma_locked = false; - VM_BUG_ON(address & ~HPAGE_PMD_MASK); - - result = alloc_charge_folio(&folio, mm, cc, HPAGE_PMD_ORDER); + result = alloc_charge_folio(&folio, mm, cc, order); if (result != SCAN_SUCCEED) goto out_nolock; @@ -1253,14 +1255,14 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a } mmap_read_lock(mm); - result = hugepage_vma_revalidate(mm, address, true, &vma, cc, - HPAGE_PMD_ORDER); + result = hugepage_vma_revalidate(mm, pmd_addr, /*expect_anon=*/ true, + &vma, cc, order); if (result != SCAN_SUCCEED) { mmap_read_unlock(mm); goto out_nolock; } - result = find_pmd_or_thp_or_none(mm, address, &pmd); + result = find_pmd_or_thp_or_none(mm, pmd_addr, &pmd); if (result != SCAN_SUCCEED) { mmap_read_unlock(mm); goto out_nolock; @@ -1272,8 +1274,8 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a * released when it fails. So we jump out_nolock directly in * that case. Continuing to collapse causes inconsistency. */ - result = __collapse_huge_page_swapin(mm, vma, address, pmd, - referenced, HPAGE_PMD_ORDER); + result = __collapse_huge_page_swapin(mm, vma, start_addr, pmd, + referenced, order); if (result != SCAN_SUCCEED) goto out_nolock; } @@ -1288,20 +1290,28 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a * mmap_lock. */ mmap_write_lock(mm); - result = hugepage_vma_revalidate(mm, address, true, &vma, cc, - HPAGE_PMD_ORDER); + result = hugepage_vma_revalidate(mm, pmd_addr, /*expect_anon=*/ true, + &vma, cc, order); if (result != SCAN_SUCCEED) goto out_up_write; /* check if the pmd is still valid */ vma_start_write(vma); - result = check_pmd_still_valid(mm, address, pmd); + result = check_pmd_still_valid(mm, pmd_addr, pmd); if (result != SCAN_SUCCEED) goto out_up_write; anon_vma_lock_write(vma->anon_vma); + anon_vma_locked = true; - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, address, - address + HPAGE_PMD_SIZE); + /* + * Only notify about the PTE range we will actually modify. While we + * temporary unmap the whole PTE table for mTHP collapse, we'll remap + * it later, leaving other PTEs effectively unmodified. The locks we + * hold prevent anybody from stumbling over such temporarily unmapped + * PTE tables. + */ + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, start_addr, + end_addr); mmu_notifier_invalidate_range_start(&range); pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ @@ -1313,26 +1323,23 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a * Parallel GUP-fast is fine since GUP-fast will back off when * it detects PMD is changed. */ - _pmd = pmdp_collapse_flush(vma, address, pmd); + _pmd = pmdp_collapse_flush(vma, pmd_addr, pmd); spin_unlock(pmd_ptl); mmu_notifier_invalidate_range_end(&range); tlb_remove_table_sync_one(); - pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl); + pte = pte_offset_map_lock(mm, &_pmd, start_addr, &pte_ptl); if (pte) { - result = __collapse_huge_page_isolate(vma, address, pte, cc, - HPAGE_PMD_ORDER, - &compound_pagelist); + result = __collapse_huge_page_isolate(vma, start_addr, pte, cc, + order, &compound_pagelist); spin_unlock(pte_ptl); } else { result = SCAN_NO_PTE_TABLE; } if (unlikely(result != SCAN_SUCCEED)) { - if (pte) - pte_unmap(pte); spin_lock(pmd_ptl); - BUG_ON(!pmd_none(*pmd)); + VM_WARN_ON_ONCE(!pmd_none(*pmd)); /* * We can only use set_pmd_at when establishing * hugepmds and never for establishing regular pmds that @@ -1340,21 +1347,24 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a */ pmd_populate(mm, pmd, pmd_pgtable(_pmd)); spin_unlock(pmd_ptl); - anon_vma_unlock_write(vma->anon_vma); goto out_up_write; } /* - * All pages are isolated and locked so anon_vma rmap - * can't run anymore. + * For PMD collapse all pages are isolated and locked so anon_vma + * rmap can't run anymore. For mTHP collapse the PMD entry has been + * removed and not all pages are isolated and locked, so we must hold + * the lock to prevent neighboring folios from attempting to access + * this PMD until its reinstalled. */ - anon_vma_unlock_write(vma->anon_vma); + if (is_pmd_order(order)) { + anon_vma_unlock_write(vma->anon_vma); + anon_vma_locked = false; + } result = __collapse_huge_page_copy(pte, folio, pmd, _pmd, - vma, address, pte_ptl, - HPAGE_PMD_ORDER, - &compound_pagelist); - pte_unmap(pte); + vma, start_addr, pte_ptl, + order, &compound_pagelist); if (unlikely(result != SCAN_SUCCEED)) goto out_up_write; @@ -1364,18 +1374,37 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a * write. */ __folio_mark_uptodate(folio); - pgtable = pmd_pgtable(_pmd); - spin_lock(pmd_ptl); - BUG_ON(!pmd_none(*pmd)); - pgtable_trans_huge_deposit(mm, pmd, pgtable); - map_anon_folio_pmd_nopf(folio, pmd, vma, address); + VM_WARN_ON_ONCE(!pmd_none(*pmd)); + if (is_pmd_order(order)) { + pgtable = pmd_pgtable(_pmd); + pgtable_trans_huge_deposit(mm, pmd, pgtable); + map_anon_folio_pmd_nopf(folio, pmd, vma, pmd_addr); + } else { + /* + * Some architectures (e.g. MIPS) walk the live page table in + * their implementation. update_mmu_cache_range() must be called + * with a valid page table hierarchy and the PTE lock held. + * Acquire it nested inside pmd_ptl when they are distinct locks. + */ + if (pte_ptl != pmd_ptl) + spin_lock_nested(pte_ptl, SINGLE_DEPTH_NESTING); + pmd_populate(mm, pmd, pmd_pgtable(_pmd)); + map_anon_folio_pte_nopf(folio, pte, vma, start_addr, + /*uffd_wp=*/ false); + if (pte_ptl != pmd_ptl) + spin_unlock(pte_ptl); + } spin_unlock(pmd_ptl); folio = NULL; result = SCAN_SUCCEED; out_up_write: + if (anon_vma_locked) + anon_vma_unlock_write(vma->anon_vma); + if (pte) + pte_unmap(pte); mmap_write_unlock(mm); out_nolock: if (folio) @@ -1555,7 +1584,7 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm, /* collapse_huge_page expects the lock to be dropped before calling */ mmap_read_unlock(mm); result = collapse_huge_page(mm, start_addr, referenced, - unmapped, cc); + unmapped, cc, HPAGE_PMD_ORDER); /* collapse_huge_page will return with the mmap_lock released */ *lock_dropped = true; }