// SPDX-License-Identifier: GPL-2.0 #include <linux/mm.h> #include <linux/rmap.h> #include <linux/hugetlb.h> #include <linux/swap.h> #include <linux/swapops.h> #include "internal.h" static inline bool not_found(struct page_vma_mapped_walk *pvmw) { page_vma_mapped_walk_done(pvmw); return false; } static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp) { pte_t ptent; if (pvmw->flags & PVMW_SYNC) { /* Use the stricter lookup */ pvmw->pte = pte_offset_map_lock(pvmw->vma->vm_mm, pvmw->pmd, pvmw->address, &pvmw->ptl); *ptlp = pvmw->ptl; return !!pvmw->pte; } /* * It is important to return the ptl corresponding to pte, * in case *pvmw->pmd changes underneath us; so we need to * return it even when choosing not to lock, in case caller * proceeds to loop over next ptes, and finds a match later. * Though, in most cases, page lock already protects this. */ pvmw->pte = pte_offset_map_nolock(pvmw->vma->vm_mm, pvmw->pmd, pvmw->address, ptlp); if (!pvmw->pte) return false; ptent = ptep_get(pvmw->pte); if (pvmw->flags & PVMW_MIGRATION) { if (!is_swap_pte(ptent)) return false; } else if (is_swap_pte(ptent)) { swp_entry_t entry; /* * Handle un-addressable ZONE_DEVICE memory. * * We get here when we are trying to unmap a private * device page from the process address space. Such * page is not CPU accessible and thus is mapped as * a special swap entry, nonetheless it still does * count as a valid regular mapping for the page * (and is accounted as such in page maps count). * * So handle this special case as if it was a normal * page mapping ie lock CPU page table and return true. * * For more details on device private memory see HMM * (include/linux/hmm.h or mm/hmm.c). */ entry = pte_to_swp_entry(ptent); if (!is_device_private_entry(entry) && !is_device_exclusive_entry(entry)) return false; } else if (!pte_present(ptent)) { return false; } pvmw->ptl = *ptlp; spin_lock(pvmw->ptl); return true; } /** * check_pte - check if [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages) is * mapped at the @pvmw->pte * @pvmw: page_vma_mapped_walk struct, includes a pair pte and pfn range * for checking * * page_vma_mapped_walk() found a place where pfn range is *potentially* * mapped. check_pte() has to validate this. * * pvmw->pte may point to empty PTE, swap PTE or PTE pointing to * arbitrary page. * * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration * entry that points to [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages) * * If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to * [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages) * * Otherwise, return false. * */ static bool check_pte(struct page_vma_mapped_walk *pvmw) { unsigned long pfn; pte_t ptent = ptep_get(pvmw->pte); if (pvmw->flags & PVMW_MIGRATION) { swp_entry_t entry; if (!is_swap_pte(ptent)) return false; entry = pte_to_swp_entry(ptent); if (!is_migration_entry(entry) && !is_device_exclusive_entry(entry)) return false; pfn = swp_offset_pfn(entry); } else if (is_swap_pte(ptent)) { swp_entry_t entry; /* Handle un-addressable ZONE_DEVICE memory */ entry = pte_to_swp_entry(ptent); if (!is_device_private_entry(entry) && !is_device_exclusive_entry(entry)) return false; pfn = swp_offset_pfn(entry); } else { if (!pte_present(ptent)) return false; pfn = pte_pfn(ptent); } return (pfn - pvmw->pfn) < pvmw->nr_pages; } /* Returns true if the two ranges overlap. Careful to not overflow. */ static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw) { if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn) return false; if (pfn > pvmw->pfn + pvmw->nr_pages - 1) return false; return true; } static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size) { pvmw->address = (pvmw->address + size) & ~(size - 1); if (!pvmw->address) pvmw->address = ULONG_MAX; } /** * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at * @pvmw->address * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags * must be set. pmd, pte and ptl must be NULL. * * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is * adjusted if needed (for PTE-mapped THPs). * * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in * a loop to find all PTEs that map the THP. * * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry * regardless of which page table level the page is mapped at. @pvmw->pmd is * NULL. * * Returns false if there are no more page table entries for the page in * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped. * * If you need to stop the walk before page_vma_mapped_walk() returned false, * use page_vma_mapped_walk_done(). It will do the housekeeping. */ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) { struct vm_area_struct *vma = pvmw->vma; struct mm_struct *mm = vma->vm_mm; unsigned long end; spinlock_t *ptl; pgd_t *pgd; p4d_t *p4d; pud_t *pud; pmd_t pmde; /* The only possible pmd mapping has been handled on last iteration */ if (pvmw->pmd && !pvmw->pte) return not_found(pvmw); if (unlikely(is_vm_hugetlb_page(vma))) { struct hstate *hstate = hstate_vma(vma); unsigned long size = huge_page_size(hstate); /* The only possible mapping was handled on last iteration */ if (pvmw->pte) return not_found(pvmw); /* * All callers that get here will already hold the * i_mmap_rwsem. Therefore, no additional locks need to be * taken before calling hugetlb_walk(). */ pvmw->pte = hugetlb_walk(vma, pvmw->address, size); if (!pvmw->pte) return false; pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte); if (!check_pte(pvmw)) return not_found(pvmw); return true; } end = vma_address_end(pvmw); if (pvmw->pte) goto next_pte; restart: do { pgd = pgd_offset(mm, pvmw->address); if (!pgd_present(*pgd)) { step_forward(pvmw, PGDIR_SIZE); continue; } p4d = p4d_offset(pgd, pvmw->address); if (!p4d_present(*p4d)) { step_forward(pvmw, P4D_SIZE); continue; } pud = pud_offset(p4d, pvmw->address); if (!pud_present(*pud)) { step_forward(pvmw, PUD_SIZE); continue; } pvmw->pmd = pmd_offset(pud, pvmw->address); /* * Make sure the pmd value isn't cached in a register by the * compiler and used as a stale value after we've observed a * subsequent update. */ pmde = pmdp_get_lockless(pvmw->pmd); if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) || (pmd_present(pmde) && pmd_devmap(pmde))) { pvmw->ptl = pmd_lock(mm, pvmw->pmd); pmde = *pvmw->pmd; if (!pmd_present(pmde)) { swp_entry_t entry; if (!thp_migration_supported() || !(pvmw->flags & PVMW_MIGRATION)) return not_found(pvmw); entry = pmd_to_swp_entry(pmde); if (!is_migration_entry(entry) || !check_pmd(swp_offset_pfn(entry), pvmw)) return not_found(pvmw); return true; } if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) { if (pvmw->flags & PVMW_MIGRATION) return not_found(pvmw); if (!check_pmd(pmd_pfn(pmde), pvmw)) return not_found(pvmw); return true; } /* THP pmd was split under us: handle on pte level */ spin_unlock(pvmw->ptl); pvmw->ptl = NULL; } else if (!pmd_present(pmde)) { /* * If PVMW_SYNC, take and drop THP pmd lock so that we * cannot return prematurely, while zap_huge_pmd() has * cleared *pmd but not decremented compound_mapcount(). */ if ((pvmw->flags & PVMW_SYNC) && thp_vma_suitable_order(vma, pvmw->address, PMD_ORDER) && (pvmw->nr_pages >= HPAGE_PMD_NR)) { spinlock_t *ptl = pmd_lock(mm, pvmw->pmd); spin_unlock(ptl); } step_forward(pvmw, PMD_SIZE); continue; } if (!map_pte(pvmw, &ptl)) { if (!pvmw->pte) goto restart; goto next_pte; } this_pte: if (check_pte(pvmw)) return true; next_pte: do { pvmw->address += PAGE_SIZE; if (pvmw->address >= end) return not_found(pvmw); /* Did we cross page table boundary? */ if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) { if (pvmw->ptl) { spin_unlock(pvmw->ptl); pvmw->ptl = NULL; } pte_unmap(pvmw->pte); pvmw->pte = NULL; goto restart; } pvmw->pte++; } while (pte_none(ptep_get(pvmw->pte))); if (!pvmw->ptl) { pvmw->ptl = ptl; spin_lock(pvmw->ptl); } goto this_pte; } while (pvmw->address < end); return false; } /** * page_mapped_in_vma - check whether a page is really mapped in a VMA * @page: the page to test * @vma: the VMA to test * * Returns 1 if the page is mapped into the page tables of the VMA, 0 * if the page is not mapped into the page tables of this VMA. Only * valid for normal file or anonymous VMAs. */ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) { struct page_vma_mapped_walk pvmw = { .pfn = page_to_pfn(page), .nr_pages = 1, .vma = vma, .flags = PVMW_SYNC, }; pvmw.address = vma_address(page, vma); if (pvmw.address == -EFAULT) return 0; if (!page_vma_mapped_walk(&pvmw)) return 0; page_vma_mapped_walk_done(&pvmw); return 1; }