| // 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) |
| { |
| pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address); |
| if (!(pvmw->flags & PVMW_SYNC)) { |
| if (pvmw->flags & PVMW_MIGRATION) { |
| if (!is_swap_pte(*pvmw->pte)) |
| return false; |
| } else { |
| /* |
| * 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 returns |
| * true. |
| * |
| * For more details on device private memory see HMM |
| * (include/linux/hmm.h or mm/hmm.c). |
| */ |
| if (is_swap_pte(*pvmw->pte)) { |
| swp_entry_t entry; |
| |
| /* Handle un-addressable ZONE_DEVICE memory */ |
| entry = pte_to_swp_entry(*pvmw->pte); |
| if (!is_device_private_entry(entry)) |
| return false; |
| } else if (!pte_present(*pvmw->pte)) |
| return false; |
| } |
| } |
| pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd); |
| spin_lock(pvmw->ptl); |
| return true; |
| } |
| |
| static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn) |
| { |
| unsigned long hpage_pfn = page_to_pfn(hpage); |
| |
| /* THP can be referenced by any subpage */ |
| return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage); |
| } |
| |
| /** |
| * check_pte - check if @pvmw->page is mapped at the @pvmw->pte |
| * |
| * page_vma_mapped_walk() found a place where @pvmw->page 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->page or any subpage in case of THP. |
| * |
| * If PVMW_MIGRATION flag is not set, returns true if @pvmw->pte points to |
| * @pvmw->page or any subpage in case of THP. |
| * |
| * Otherwise, return false. |
| * |
| */ |
| static bool check_pte(struct page_vma_mapped_walk *pvmw) |
| { |
| unsigned long pfn; |
| |
| if (pvmw->flags & PVMW_MIGRATION) { |
| swp_entry_t entry; |
| if (!is_swap_pte(*pvmw->pte)) |
| return false; |
| entry = pte_to_swp_entry(*pvmw->pte); |
| |
| if (!is_migration_entry(entry)) |
| return false; |
| |
| pfn = migration_entry_to_pfn(entry); |
| } else if (is_swap_pte(*pvmw->pte)) { |
| swp_entry_t entry; |
| |
| /* Handle un-addressable ZONE_DEVICE memory */ |
| entry = pte_to_swp_entry(*pvmw->pte); |
| if (!is_device_private_entry(entry)) |
| return false; |
| |
| pfn = device_private_entry_to_pfn(entry); |
| } else { |
| if (!pte_present(*pvmw->pte)) |
| return false; |
| |
| pfn = pte_pfn(*pvmw->pte); |
| } |
| |
| return pfn_in_hpage(pvmw->page, pfn); |
| } |
| |
| 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->page 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. |
| * |
| * Retruns 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 mm_struct *mm = pvmw->vma->vm_mm; |
| struct page *page = pvmw->page; |
| unsigned long end; |
| 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(PageHuge(page))) { |
| /* The only possible mapping was handled on last iteration */ |
| if (pvmw->pte) |
| return not_found(pvmw); |
| |
| /* when pud is not present, pte will be NULL */ |
| pvmw->pte = huge_pte_offset(mm, pvmw->address, |
| PAGE_SIZE << compound_order(page)); |
| if (!pvmw->pte) |
| return false; |
| |
| pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); |
| spin_lock(pvmw->ptl); |
| if (!check_pte(pvmw)) |
| return not_found(pvmw); |
| return true; |
| } |
| |
| /* |
| * Seek to next pte only makes sense for THP. |
| * But more important than that optimization, is to filter out |
| * any PageKsm page: whose page->index misleads vma_address() |
| * and vma_address_end() to disaster. |
| */ |
| end = PageTransCompound(page) ? |
| vma_address_end(page, pvmw->vma) : |
| pvmw->address + PAGE_SIZE; |
| 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 = READ_ONCE(*pvmw->pmd); |
| |
| if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) { |
| pvmw->ptl = pmd_lock(mm, pvmw->pmd); |
| pmde = *pvmw->pmd; |
| if (likely(pmd_trans_huge(pmde))) { |
| if (pvmw->flags & PVMW_MIGRATION) |
| return not_found(pvmw); |
| if (pmd_page(pmde) != page) |
| return not_found(pvmw); |
| return true; |
| } |
| 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) || |
| migration_entry_to_page(entry) != page) |
| 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) && |
| PageTransCompound(page)) { |
| spinlock_t *ptl = pmd_lock(mm, pvmw->pmd); |
| |
| spin_unlock(ptl); |
| } |
| step_forward(pvmw, PMD_SIZE); |
| continue; |
| } |
| if (!map_pte(pvmw)) |
| 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++; |
| if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) { |
| pvmw->ptl = pte_lockptr(mm, pvmw->pmd); |
| spin_lock(pvmw->ptl); |
| } |
| } while (pte_none(*pvmw->pte)); |
| |
| if (!pvmw->ptl) { |
| pvmw->ptl = pte_lockptr(mm, pvmw->pmd); |
| 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 = { |
| .page = page, |
| .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; |
| } |