diff options
Diffstat (limited to 'mm/page_vma_mapped.c')
| -rw-r--r-- | mm/page_vma_mapped.c | 375 |
1 files changed, 375 insertions, 0 deletions
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c new file mode 100644 index 000000000..d7670ba41 --- /dev/null +++ b/mm/page_vma_mapped.c @@ -0,0 +1,375 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/mm.h> +#include <linux/rmap.h> +#include <linux/hugetlb.h> +#include <linux/swap.h> +#include <linux/leafops.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, pmd_t *pmdvalp, + spinlock_t **ptlp) +{ + bool is_migration; + 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; + } + + is_migration = pvmw->flags & PVMW_MIGRATION; +again: + /* + * 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_rw_nolock(pvmw->vma->vm_mm, pvmw->pmd, + pvmw->address, pmdvalp, ptlp); + if (!pvmw->pte) + return false; + + ptent = ptep_get_lockless(pvmw->pte); + + if (pte_none(ptent)) { + return false; + } else if (pte_present(ptent)) { + if (is_migration) + return false; + } else if (!is_migration) { + softleaf_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 = softleaf_from_pte(ptent); + if (!softleaf_is_device_private(entry) && + !softleaf_is_device_exclusive(entry)) + return false; + } + spin_lock(*ptlp); + if (unlikely(!pmd_same(*pmdvalp, pmdp_get_lockless(pvmw->pmd)))) { + pte_unmap_unlock(pvmw->pte, *ptlp); + goto again; + } + pvmw->ptl = *ptlp; + + 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 + * @pte_nr: the number of small pages described by @pvmw->pte. + * + * 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 pte_nr) +{ + unsigned long pfn; + pte_t ptent; + + if (is_vm_hugetlb_page(pvmw->vma)) + ptent = huge_ptep_get(pvmw->vma->vm_mm, pvmw->address, + pvmw->pte); + else + ptent = ptep_get(pvmw->pte); + + if (pvmw->flags & PVMW_MIGRATION) { + const softleaf_t entry = softleaf_from_pte(ptent); + + if (!softleaf_is_migration(entry)) + return false; + + pfn = softleaf_to_pfn(entry); + } else if (pte_present(ptent)) { + pfn = pte_pfn(ptent); + } else { + const softleaf_t entry = softleaf_from_pte(ptent); + + /* Handle un-addressable ZONE_DEVICE memory */ + if (!softleaf_is_device_private(entry) && + !softleaf_is_device_exclusive(entry)) + return false; + + pfn = softleaf_to_pfn(entry); + } + + if ((pfn + pte_nr - 1) < pvmw->pfn) + return false; + if (pfn > (pvmw->pfn + pvmw->nr_pages - 1)) + return false; + return true; +} + +/* 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; + pte_t pteval; + 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, pages_per_huge_page(hstate))) + 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 (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && + (pmd_trans_huge(pmde) || pmd_is_migration_entry(pmde) || + pmd_is_device_private_entry(pmde))) { + pvmw->ptl = pmd_lock(mm, pvmw->pmd); + pmde = *pvmw->pmd; + if (pmd_is_migration_entry(pmde)) { + softleaf_t entry; + + if (!(pvmw->flags & PVMW_MIGRATION)) + return not_found(pvmw); + entry = softleaf_from_pmd(pmde); + if (!check_pmd(softleaf_to_pfn(entry), pvmw)) + return not_found(pvmw); + return true; + } else if (pmd_is_device_private_entry(pmde)) { + softleaf_t entry; + + if (pvmw->flags & PVMW_MIGRATION) + return not_found(pvmw); + entry = softleaf_from_pmd(pmde); + if (!check_pmd(softleaf_to_pfn(entry), pvmw)) + return not_found(pvmw); + return true; + } else if (!pmd_present(pmde)) { + return not_found(pvmw); + } + if (likely(pmd_trans_huge(pmde))) { + if (pvmw->flags & PVMW_MIGRATION) + return not_found(pvmw); + if (!check_pmd(pmd_pfn(pmde), pvmw)) + return not_found(pvmw); + return true; + } + /* THP/device-private pmd was split under us: handle on pte level */ + spin_unlock(pvmw->ptl); + pvmw->ptl = NULL; + } else if (!pmd_present(pmde)) { + if ((pvmw->flags & PVMW_SYNC) && + thp_vma_suitable_order(vma, pvmw->address, + PMD_ORDER) && + (pvmw->nr_pages >= HPAGE_PMD_NR)) + sync_with_folio_pmd_zap(mm, pvmw->pmd); + + step_forward(pvmw, PMD_SIZE); + continue; + } + if (!map_pte(pvmw, &pmde, &ptl)) { + if (!pvmw->pte) + goto restart; + goto next_pte; + } +this_pte: + if (check_pte(pvmw, 1)) + 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; + pvmw->flags |= PVMW_PGTABLE_CROSSED; + goto restart; + } + pvmw->pte++; + if (!pvmw->ptl) + pteval = ptep_get_lockless(pvmw->pte); + else + pteval = ptep_get(pvmw->pte); + } while (pte_none(pteval)); + + if (!pvmw->ptl) { + spin_lock(ptl); + if (unlikely(!pmd_same(pmde, pmdp_get_lockless(pvmw->pmd)))) { + pte_unmap_unlock(pvmw->pte, ptl); + pvmw->pte = NULL; + goto restart; + } + pvmw->ptl = ptl; + } + goto this_pte; + } while (pvmw->address < end); + + return false; +} + +#ifdef CONFIG_MEMORY_FAILURE +/** + * page_mapped_in_vma - check whether a page is really mapped in a VMA + * @page: the page to test + * @vma: the VMA to test + * + * Return: The address the page is mapped at if the page is in the range + * covered by the VMA and present in the page table. If the page is + * outside the VMA or not present, returns -EFAULT. + * Only valid for normal file or anonymous VMAs. + */ +unsigned long page_mapped_in_vma(const struct page *page, + struct vm_area_struct *vma) +{ + const struct folio *folio = page_folio(page); + struct page_vma_mapped_walk pvmw = { + .pfn = page_to_pfn(page), + .nr_pages = 1, + .vma = vma, + .flags = PVMW_SYNC, + }; + + pvmw.address = vma_address(vma, page_pgoff(folio, page), 1); + if (pvmw.address == -EFAULT) + goto out; + if (!page_vma_mapped_walk(&pvmw)) + return -EFAULT; + page_vma_mapped_walk_done(&pvmw); +out: + return pvmw.address; +} +#endif |