// SPDX-License-Identifier: GPL-2.0-only /* * Copyright (C) 2009 Red Hat, Inc. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "internal.h" /* * By default, transparent hugepage support is disabled in order to avoid * risking an increased memory footprint for applications that are not * guaranteed to benefit from it. When transparent hugepage support is * enabled, it is for all mappings, and khugepaged scans all mappings. * Defrag is invoked by khugepaged hugepage allocations and by page faults * for all hugepage allocations. */ unsigned long transparent_hugepage_flags __read_mostly = #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS (1<vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE; if (!transhuge_vma_suitable(vma, addr)) return false; if (vma_is_anonymous(vma)) return __transparent_hugepage_enabled(vma); if (vma_is_shmem(vma)) return shmem_huge_enabled(vma); return false; } static struct page *get_huge_zero_page(void) { struct page *zero_page; retry: if (likely(atomic_inc_not_zero(&huge_zero_refcount))) return READ_ONCE(huge_zero_page); zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, HPAGE_PMD_ORDER); if (!zero_page) { count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); return NULL; } count_vm_event(THP_ZERO_PAGE_ALLOC); preempt_disable(); if (cmpxchg(&huge_zero_page, NULL, zero_page)) { preempt_enable(); __free_pages(zero_page, compound_order(zero_page)); goto retry; } /* We take additional reference here. It will be put back by shrinker */ atomic_set(&huge_zero_refcount, 2); preempt_enable(); return READ_ONCE(huge_zero_page); } static void put_huge_zero_page(void) { /* * Counter should never go to zero here. Only shrinker can put * last reference. */ BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); } struct page *mm_get_huge_zero_page(struct mm_struct *mm) { if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) return READ_ONCE(huge_zero_page); if (!get_huge_zero_page()) return NULL; if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) put_huge_zero_page(); return READ_ONCE(huge_zero_page); } void mm_put_huge_zero_page(struct mm_struct *mm) { if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) put_huge_zero_page(); } static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, struct shrink_control *sc) { /* we can free zero page only if last reference remains */ return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; } static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, struct shrink_control *sc) { if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { struct page *zero_page = xchg(&huge_zero_page, NULL); BUG_ON(zero_page == NULL); __free_pages(zero_page, compound_order(zero_page)); return HPAGE_PMD_NR; } return 0; } static struct shrinker huge_zero_page_shrinker = { .count_objects = shrink_huge_zero_page_count, .scan_objects = shrink_huge_zero_page_scan, .seeks = DEFAULT_SEEKS, }; #ifdef CONFIG_SYSFS static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { const char *output; if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) output = "[always] madvise never"; else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) output = "always [madvise] never"; else output = "always madvise [never]"; return sysfs_emit(buf, "%s\n", output); } static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { ssize_t ret = count; if (sysfs_streq(buf, "always")) { clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); } else if (sysfs_streq(buf, "madvise")) { clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); } else if (sysfs_streq(buf, "never")) { clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); } else ret = -EINVAL; if (ret > 0) { int err = start_stop_khugepaged(); if (err) ret = err; } return ret; } static struct kobj_attribute enabled_attr = __ATTR(enabled, 0644, enabled_show, enabled_store); ssize_t single_hugepage_flag_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf, enum transparent_hugepage_flag flag) { return sysfs_emit(buf, "%d\n", !!test_bit(flag, &transparent_hugepage_flags)); } ssize_t single_hugepage_flag_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count, enum transparent_hugepage_flag flag) { unsigned long value; int ret; ret = kstrtoul(buf, 10, &value); if (ret < 0) return ret; if (value > 1) return -EINVAL; if (value) set_bit(flag, &transparent_hugepage_flags); else clear_bit(flag, &transparent_hugepage_flags); return count; } static ssize_t defrag_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { const char *output; if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) output = "[always] defer defer+madvise madvise never"; else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) output = "always [defer] defer+madvise madvise never"; else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) output = "always defer [defer+madvise] madvise never"; else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) output = "always defer defer+madvise [madvise] never"; else output = "always defer defer+madvise madvise [never]"; return sysfs_emit(buf, "%s\n", output); } static ssize_t defrag_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { if (sysfs_streq(buf, "always")) { clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); } else if (sysfs_streq(buf, "defer+madvise")) { clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); } else if (sysfs_streq(buf, "defer")) { clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); } else if (sysfs_streq(buf, "madvise")) { clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); } else if (sysfs_streq(buf, "never")) { clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); } else return -EINVAL; return count; } static struct kobj_attribute defrag_attr = __ATTR(defrag, 0644, defrag_show, defrag_store); static ssize_t use_zero_page_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return single_hugepage_flag_show(kobj, attr, buf, TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); } static ssize_t use_zero_page_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { return single_hugepage_flag_store(kobj, attr, buf, count, TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); } static struct kobj_attribute use_zero_page_attr = __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); static ssize_t hpage_pmd_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sysfs_emit(buf, "%lu\n", HPAGE_PMD_SIZE); } static struct kobj_attribute hpage_pmd_size_attr = __ATTR_RO(hpage_pmd_size); static struct attribute *hugepage_attr[] = { &enabled_attr.attr, &defrag_attr.attr, &use_zero_page_attr.attr, &hpage_pmd_size_attr.attr, #ifdef CONFIG_SHMEM &shmem_enabled_attr.attr, #endif NULL, }; static const struct attribute_group hugepage_attr_group = { .attrs = hugepage_attr, }; static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) { int err; *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); if (unlikely(!*hugepage_kobj)) { pr_err("failed to create transparent hugepage kobject\n"); return -ENOMEM; } err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); if (err) { pr_err("failed to register transparent hugepage group\n"); goto delete_obj; } err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); if (err) { pr_err("failed to register transparent hugepage group\n"); goto remove_hp_group; } return 0; remove_hp_group: sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); delete_obj: kobject_put(*hugepage_kobj); return err; } static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) { sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); kobject_put(hugepage_kobj); } #else static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) { return 0; } static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) { } #endif /* CONFIG_SYSFS */ static int __init hugepage_init(void) { int err; struct kobject *hugepage_kobj; if (!has_transparent_hugepage()) { /* * Hardware doesn't support hugepages, hence disable * DAX PMD support. */ transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_NEVER_DAX; return -EINVAL; } /* * hugepages can't be allocated by the buddy allocator */ MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); /* * we use page->mapping and page->index in second tail page * as list_head: assuming THP order >= 2 */ MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); err = hugepage_init_sysfs(&hugepage_kobj); if (err) goto err_sysfs; err = khugepaged_init(); if (err) goto err_slab; err = register_shrinker(&huge_zero_page_shrinker); if (err) goto err_hzp_shrinker; err = register_shrinker(&deferred_split_shrinker); if (err) goto err_split_shrinker; /* * By default disable transparent hugepages on smaller systems, * where the extra memory used could hurt more than TLB overhead * is likely to save. The admin can still enable it through /sys. */ if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) { transparent_hugepage_flags = 0; return 0; } err = start_stop_khugepaged(); if (err) goto err_khugepaged; return 0; err_khugepaged: unregister_shrinker(&deferred_split_shrinker); err_split_shrinker: unregister_shrinker(&huge_zero_page_shrinker); err_hzp_shrinker: khugepaged_destroy(); err_slab: hugepage_exit_sysfs(hugepage_kobj); err_sysfs: return err; } subsys_initcall(hugepage_init); static int __init setup_transparent_hugepage(char *str) { int ret = 0; if (!str) goto out; if (!strcmp(str, "always")) { set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); ret = 1; } else if (!strcmp(str, "madvise")) { clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); ret = 1; } else if (!strcmp(str, "never")) { clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); ret = 1; } out: if (!ret) pr_warn("transparent_hugepage= cannot parse, ignored\n"); return ret; } __setup("transparent_hugepage=", setup_transparent_hugepage); pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) { if (likely(vma->vm_flags & VM_WRITE)) pmd = pmd_mkwrite(pmd); return pmd; } #ifdef CONFIG_MEMCG static inline struct deferred_split *get_deferred_split_queue(struct page *page) { struct mem_cgroup *memcg = page_memcg(compound_head(page)); struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); if (memcg) return &memcg->deferred_split_queue; else return &pgdat->deferred_split_queue; } #else static inline struct deferred_split *get_deferred_split_queue(struct page *page) { struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); return &pgdat->deferred_split_queue; } #endif void prep_transhuge_page(struct page *page) { /* * we use page->mapping and page->indexlru in second tail page * as list_head: assuming THP order >= 2 */ INIT_LIST_HEAD(page_deferred_list(page)); set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); } bool is_transparent_hugepage(struct page *page) { if (!PageCompound(page)) return false; page = compound_head(page); return is_huge_zero_page(page) || page[1].compound_dtor == TRANSHUGE_PAGE_DTOR; } EXPORT_SYMBOL_GPL(is_transparent_hugepage); static unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len, loff_t off, unsigned long flags, unsigned long size) { loff_t off_end = off + len; loff_t off_align = round_up(off, size); unsigned long len_pad, ret; if (off_end <= off_align || (off_end - off_align) < size) return 0; len_pad = len + size; if (len_pad < len || (off + len_pad) < off) return 0; ret = current->mm->get_unmapped_area(filp, addr, len_pad, off >> PAGE_SHIFT, flags); /* * The failure might be due to length padding. The caller will retry * without the padding. */ if (IS_ERR_VALUE(ret)) return 0; /* * Do not try to align to THP boundary if allocation at the address * hint succeeds. */ if (ret == addr) return addr; ret += (off - ret) & (size - 1); return ret; } unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { unsigned long ret; loff_t off = (loff_t)pgoff << PAGE_SHIFT; if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD)) goto out; ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE); if (ret) return ret; out: return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags); } EXPORT_SYMBOL_GPL(thp_get_unmapped_area); static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page, gfp_t gfp) { struct vm_area_struct *vma = vmf->vma; pgtable_t pgtable; unsigned long haddr = vmf->address & HPAGE_PMD_MASK; vm_fault_t ret = 0; VM_BUG_ON_PAGE(!PageCompound(page), page); if (mem_cgroup_charge(page, vma->vm_mm, gfp)) { put_page(page); count_vm_event(THP_FAULT_FALLBACK); count_vm_event(THP_FAULT_FALLBACK_CHARGE); return VM_FAULT_FALLBACK; } cgroup_throttle_swaprate(page, gfp); pgtable = pte_alloc_one(vma->vm_mm); if (unlikely(!pgtable)) { ret = VM_FAULT_OOM; goto release; } clear_huge_page(page, vmf->address, HPAGE_PMD_NR); /* * The memory barrier inside __SetPageUptodate makes sure that * clear_huge_page writes become visible before the set_pmd_at() * write. */ __SetPageUptodate(page); vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); if (unlikely(!pmd_none(*vmf->pmd))) { goto unlock_release; } else { pmd_t entry; ret = check_stable_address_space(vma->vm_mm); if (ret) goto unlock_release; /* Deliver the page fault to userland */ if (userfaultfd_missing(vma)) { spin_unlock(vmf->ptl); put_page(page); pte_free(vma->vm_mm, pgtable); ret = handle_userfault(vmf, VM_UFFD_MISSING); VM_BUG_ON(ret & VM_FAULT_FALLBACK); return ret; } entry = mk_huge_pmd(page, vma->vm_page_prot); entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); page_add_new_anon_rmap(page, vma, haddr, true); lru_cache_add_inactive_or_unevictable(page, vma); pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); mm_inc_nr_ptes(vma->vm_mm); spin_unlock(vmf->ptl); count_vm_event(THP_FAULT_ALLOC); count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC); } return 0; unlock_release: spin_unlock(vmf->ptl); release: if (pgtable) pte_free(vma->vm_mm, pgtable); put_page(page); return ret; } /* * always: directly stall for all thp allocations * defer: wake kswapd and fail if not immediately available * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise * fail if not immediately available * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately * available * never: never stall for any thp allocation */ gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma) { const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE); /* Always do synchronous compaction */ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY); /* Kick kcompactd and fail quickly */ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM; /* Synchronous compaction if madvised, otherwise kick kcompactd */ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM : __GFP_KSWAPD_RECLAIM); /* Only do synchronous compaction if madvised */ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM : 0); return GFP_TRANSHUGE_LIGHT; } /* Caller must hold page table lock. */ static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, struct page *zero_page) { pmd_t entry; if (!pmd_none(*pmd)) return; entry = mk_pmd(zero_page, vma->vm_page_prot); entry = pmd_mkhuge(entry); if (pgtable) pgtable_trans_huge_deposit(mm, pmd, pgtable); set_pmd_at(mm, haddr, pmd, entry); mm_inc_nr_ptes(mm); } vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; gfp_t gfp; struct page *page; unsigned long haddr = vmf->address & HPAGE_PMD_MASK; if (!transhuge_vma_suitable(vma, haddr)) return VM_FAULT_FALLBACK; if (unlikely(anon_vma_prepare(vma))) return VM_FAULT_OOM; if (unlikely(khugepaged_enter(vma, vma->vm_flags))) return VM_FAULT_OOM; if (!(vmf->flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(vma->vm_mm) && transparent_hugepage_use_zero_page()) { pgtable_t pgtable; struct page *zero_page; vm_fault_t ret; pgtable = pte_alloc_one(vma->vm_mm); if (unlikely(!pgtable)) return VM_FAULT_OOM; zero_page = mm_get_huge_zero_page(vma->vm_mm); if (unlikely(!zero_page)) { pte_free(vma->vm_mm, pgtable); count_vm_event(THP_FAULT_FALLBACK); return VM_FAULT_FALLBACK; } vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); ret = 0; if (pmd_none(*vmf->pmd)) { ret = check_stable_address_space(vma->vm_mm); if (ret) { spin_unlock(vmf->ptl); pte_free(vma->vm_mm, pgtable); } else if (userfaultfd_missing(vma)) { spin_unlock(vmf->ptl); pte_free(vma->vm_mm, pgtable); ret = handle_userfault(vmf, VM_UFFD_MISSING); VM_BUG_ON(ret & VM_FAULT_FALLBACK); } else { set_huge_zero_page(pgtable, vma->vm_mm, vma, haddr, vmf->pmd, zero_page); update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); spin_unlock(vmf->ptl); } } else { spin_unlock(vmf->ptl); pte_free(vma->vm_mm, pgtable); } return ret; } gfp = vma_thp_gfp_mask(vma); page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); if (unlikely(!page)) { count_vm_event(THP_FAULT_FALLBACK); return VM_FAULT_FALLBACK; } prep_transhuge_page(page); return __do_huge_pmd_anonymous_page(vmf, page, gfp); } static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write, pgtable_t pgtable) { struct mm_struct *mm = vma->vm_mm; pmd_t entry; spinlock_t *ptl; ptl = pmd_lock(mm, pmd); if (!pmd_none(*pmd)) { if (write) { if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) { WARN_ON_ONCE(!is_huge_zero_pmd(*pmd)); goto out_unlock; } entry = pmd_mkyoung(*pmd); entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); if (pmdp_set_access_flags(vma, addr, pmd, entry, 1)) update_mmu_cache_pmd(vma, addr, pmd); } goto out_unlock; } entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); if (pfn_t_devmap(pfn)) entry = pmd_mkdevmap(entry); if (write) { entry = pmd_mkyoung(pmd_mkdirty(entry)); entry = maybe_pmd_mkwrite(entry, vma); } if (pgtable) { pgtable_trans_huge_deposit(mm, pmd, pgtable); mm_inc_nr_ptes(mm); pgtable = NULL; } set_pmd_at(mm, addr, pmd, entry); update_mmu_cache_pmd(vma, addr, pmd); out_unlock: spin_unlock(ptl); if (pgtable) pte_free(mm, pgtable); } /** * vmf_insert_pfn_pmd_prot - insert a pmd size pfn * @vmf: Structure describing the fault * @pfn: pfn to insert * @pgprot: page protection to use * @write: whether it's a write fault * * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and * also consult the vmf_insert_mixed_prot() documentation when * @pgprot != @vmf->vma->vm_page_prot. * * Return: vm_fault_t value. */ vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn, pgprot_t pgprot, bool write) { unsigned long addr = vmf->address & PMD_MASK; struct vm_area_struct *vma = vmf->vma; pgtable_t pgtable = NULL; /* * If we had pmd_special, we could avoid all these restrictions, * but we need to be consistent with PTEs and architectures that * can't support a 'special' bit. */ BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && !pfn_t_devmap(pfn)); BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == (VM_PFNMAP|VM_MIXEDMAP)); BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); if (addr < vma->vm_start || addr >= vma->vm_end) return VM_FAULT_SIGBUS; if (arch_needs_pgtable_deposit()) { pgtable = pte_alloc_one(vma->vm_mm); if (!pgtable) return VM_FAULT_OOM; } track_pfn_insert(vma, &pgprot, pfn); insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable); return VM_FAULT_NOPAGE; } EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot); #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma) { if (likely(vma->vm_flags & VM_WRITE)) pud = pud_mkwrite(pud); return pud; } static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, pud_t *pud, pfn_t pfn, pgprot_t prot, bool write) { struct mm_struct *mm = vma->vm_mm; pud_t entry; spinlock_t *ptl; ptl = pud_lock(mm, pud); if (!pud_none(*pud)) { if (write) { if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) { WARN_ON_ONCE(!is_huge_zero_pud(*pud)); goto out_unlock; } entry = pud_mkyoung(*pud); entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma); if (pudp_set_access_flags(vma, addr, pud, entry, 1)) update_mmu_cache_pud(vma, addr, pud); } goto out_unlock; } entry = pud_mkhuge(pfn_t_pud(pfn, prot)); if (pfn_t_devmap(pfn)) entry = pud_mkdevmap(entry); if (write) { entry = pud_mkyoung(pud_mkdirty(entry)); entry = maybe_pud_mkwrite(entry, vma); } set_pud_at(mm, addr, pud, entry); update_mmu_cache_pud(vma, addr, pud); out_unlock: spin_unlock(ptl); } /** * vmf_insert_pfn_pud_prot - insert a pud size pfn * @vmf: Structure describing the fault * @pfn: pfn to insert * @pgprot: page protection to use * @write: whether it's a write fault * * Insert a pud size pfn. See vmf_insert_pfn() for additional info and * also consult the vmf_insert_mixed_prot() documentation when * @pgprot != @vmf->vma->vm_page_prot. * * Return: vm_fault_t value. */ vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn, pgprot_t pgprot, bool write) { unsigned long addr = vmf->address & PUD_MASK; struct vm_area_struct *vma = vmf->vma; /* * If we had pud_special, we could avoid all these restrictions, * but we need to be consistent with PTEs and architectures that * can't support a 'special' bit. */ BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && !pfn_t_devmap(pfn)); BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == (VM_PFNMAP|VM_MIXEDMAP)); BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); if (addr < vma->vm_start || addr >= vma->vm_end) return VM_FAULT_SIGBUS; track_pfn_insert(vma, &pgprot, pfn); insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write); return VM_FAULT_NOPAGE; } EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot); #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd, int flags) { pmd_t _pmd; _pmd = pmd_mkyoung(*pmd); if (flags & FOLL_WRITE) _pmd = pmd_mkdirty(_pmd); if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, pmd, _pmd, flags & FOLL_WRITE)) update_mmu_cache_pmd(vma, addr, pmd); } struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd, int flags, struct dev_pagemap **pgmap) { unsigned long pfn = pmd_pfn(*pmd); struct mm_struct *mm = vma->vm_mm; struct page *page; assert_spin_locked(pmd_lockptr(mm, pmd)); /* * When we COW a devmap PMD entry, we split it into PTEs, so we should * not be in this function with `flags & FOLL_COW` set. */ WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set"); /* FOLL_GET and FOLL_PIN are mutually exclusive. */ if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == (FOLL_PIN | FOLL_GET))) return NULL; if (flags & FOLL_WRITE && !pmd_write(*pmd)) return NULL; if (pmd_present(*pmd) && pmd_devmap(*pmd)) /* pass */; else return NULL; if (flags & FOLL_TOUCH) touch_pmd(vma, addr, pmd, flags); /* * device mapped pages can only be returned if the * caller will manage the page reference count. */ if (!(flags & (FOLL_GET | FOLL_PIN))) return ERR_PTR(-EEXIST); pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; *pgmap = get_dev_pagemap(pfn, *pgmap); if (!*pgmap) return ERR_PTR(-EFAULT); page = pfn_to_page(pfn); if (!try_grab_page(page, flags)) page = ERR_PTR(-ENOMEM); return page; } int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, struct vm_area_struct *vma) { spinlock_t *dst_ptl, *src_ptl; struct page *src_page; pmd_t pmd; pgtable_t pgtable = NULL; int ret = -ENOMEM; /* Skip if can be re-fill on fault */ if (!vma_is_anonymous(vma)) return 0; pgtable = pte_alloc_one(dst_mm); if (unlikely(!pgtable)) goto out; dst_ptl = pmd_lock(dst_mm, dst_pmd); src_ptl = pmd_lockptr(src_mm, src_pmd); spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); ret = -EAGAIN; pmd = *src_pmd; /* * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA * does not have the VM_UFFD_WP, which means that the uffd * fork event is not enabled. */ if (!(vma->vm_flags & VM_UFFD_WP)) pmd = pmd_clear_uffd_wp(pmd); #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION if (unlikely(is_swap_pmd(pmd))) { swp_entry_t entry = pmd_to_swp_entry(pmd); VM_BUG_ON(!is_pmd_migration_entry(pmd)); if (is_write_migration_entry(entry)) { make_migration_entry_read(&entry); pmd = swp_entry_to_pmd(entry); if (pmd_swp_soft_dirty(*src_pmd)) pmd = pmd_swp_mksoft_dirty(pmd); set_pmd_at(src_mm, addr, src_pmd, pmd); } add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); mm_inc_nr_ptes(dst_mm); pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); set_pmd_at(dst_mm, addr, dst_pmd, pmd); ret = 0; goto out_unlock; } #endif if (unlikely(!pmd_trans_huge(pmd))) { pte_free(dst_mm, pgtable); goto out_unlock; } /* * When page table lock is held, the huge zero pmd should not be * under splitting since we don't split the page itself, only pmd to * a page table. */ if (is_huge_zero_pmd(pmd)) { struct page *zero_page; /* * get_huge_zero_page() will never allocate a new page here, * since we already have a zero page to copy. It just takes a * reference. */ zero_page = mm_get_huge_zero_page(dst_mm); set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, zero_page); ret = 0; goto out_unlock; } src_page = pmd_page(pmd); VM_BUG_ON_PAGE(!PageHead(src_page), src_page); /* * If this page is a potentially pinned page, split and retry the fault * with smaller page size. Normally this should not happen because the * userspace should use MADV_DONTFORK upon pinned regions. This is a * best effort that the pinned pages won't be replaced by another * random page during the coming copy-on-write. */ if (unlikely(page_needs_cow_for_dma(vma, src_page))) { pte_free(dst_mm, pgtable); spin_unlock(src_ptl); spin_unlock(dst_ptl); __split_huge_pmd(vma, src_pmd, addr, false, NULL); return -EAGAIN; } get_page(src_page); page_dup_rmap(src_page, true); add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); mm_inc_nr_ptes(dst_mm); pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); pmdp_set_wrprotect(src_mm, addr, src_pmd); pmd = pmd_mkold(pmd_wrprotect(pmd)); set_pmd_at(dst_mm, addr, dst_pmd, pmd); ret = 0; out_unlock: spin_unlock(src_ptl); spin_unlock(dst_ptl); out: return ret; } #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD static void touch_pud(struct vm_area_struct *vma, unsigned long addr, pud_t *pud, int flags) { pud_t _pud; _pud = pud_mkyoung(*pud); if (flags & FOLL_WRITE) _pud = pud_mkdirty(_pud); if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK, pud, _pud, flags & FOLL_WRITE)) update_mmu_cache_pud(vma, addr, pud); } struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, pud_t *pud, int flags, struct dev_pagemap **pgmap) { unsigned long pfn = pud_pfn(*pud); struct mm_struct *mm = vma->vm_mm; struct page *page; assert_spin_locked(pud_lockptr(mm, pud)); if (flags & FOLL_WRITE && !pud_write(*pud)) return NULL; /* FOLL_GET and FOLL_PIN are mutually exclusive. */ if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == (FOLL_PIN | FOLL_GET))) return NULL; if (pud_present(*pud) && pud_devmap(*pud)) /* pass */; else return NULL; if (flags & FOLL_TOUCH) touch_pud(vma, addr, pud, flags); /* * device mapped pages can only be returned if the * caller will manage the page reference count. * * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here: */ if (!(flags & (FOLL_GET | FOLL_PIN))) return ERR_PTR(-EEXIST); pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT; *pgmap = get_dev_pagemap(pfn, *pgmap); if (!*pgmap) return ERR_PTR(-EFAULT); page = pfn_to_page(pfn); if (!try_grab_page(page, flags)) page = ERR_PTR(-ENOMEM); return page; } int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, pud_t *dst_pud, pud_t *src_pud, unsigned long addr, struct vm_area_struct *vma) { spinlock_t *dst_ptl, *src_ptl; pud_t pud; int ret; dst_ptl = pud_lock(dst_mm, dst_pud); src_ptl = pud_lockptr(src_mm, src_pud); spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); ret = -EAGAIN; pud = *src_pud; if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud))) goto out_unlock; /* * When page table lock is held, the huge zero pud should not be * under splitting since we don't split the page itself, only pud to * a page table. */ if (is_huge_zero_pud(pud)) { /* No huge zero pud yet */ } /* Please refer to comments in copy_huge_pmd() */ if (unlikely(page_needs_cow_for_dma(vma, pud_page(pud)))) { spin_unlock(src_ptl); spin_unlock(dst_ptl); __split_huge_pud(vma, src_pud, addr); return -EAGAIN; } pudp_set_wrprotect(src_mm, addr, src_pud); pud = pud_mkold(pud_wrprotect(pud)); set_pud_at(dst_mm, addr, dst_pud, pud); ret = 0; out_unlock: spin_unlock(src_ptl); spin_unlock(dst_ptl); return ret; } void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud) { pud_t entry; unsigned long haddr; bool write = vmf->flags & FAULT_FLAG_WRITE; vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud); if (unlikely(!pud_same(*vmf->pud, orig_pud))) goto unlock; entry = pud_mkyoung(orig_pud); if (write) entry = pud_mkdirty(entry); haddr = vmf->address & HPAGE_PUD_MASK; if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write)) update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud); unlock: spin_unlock(vmf->ptl); } #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) { pmd_t entry; unsigned long haddr; bool write = vmf->flags & FAULT_FLAG_WRITE; vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) goto unlock; entry = pmd_mkyoung(orig_pmd); if (write) entry = pmd_mkdirty(entry); haddr = vmf->address & HPAGE_PMD_MASK; if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); unlock: spin_unlock(vmf->ptl); } vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) { struct vm_area_struct *vma = vmf->vma; struct page *page; unsigned long haddr = vmf->address & HPAGE_PMD_MASK; vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); VM_BUG_ON_VMA(!vma->anon_vma, vma); if (is_huge_zero_pmd(orig_pmd)) goto fallback; spin_lock(vmf->ptl); if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { spin_unlock(vmf->ptl); return 0; } page = pmd_page(orig_pmd); VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); /* Lock page for reuse_swap_page() */ if (!trylock_page(page)) { get_page(page); spin_unlock(vmf->ptl); lock_page(page); spin_lock(vmf->ptl); if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { spin_unlock(vmf->ptl); unlock_page(page); put_page(page); return 0; } put_page(page); } /* * We can only reuse the page if nobody else maps the huge page or it's * part. */ if (reuse_swap_page(page, NULL)) { pmd_t entry; entry = pmd_mkyoung(orig_pmd); entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1)) update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); unlock_page(page); spin_unlock(vmf->ptl); return VM_FAULT_WRITE; } unlock_page(page); spin_unlock(vmf->ptl); fallback: __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL); return VM_FAULT_FALLBACK; } /* * FOLL_FORCE can write to even unwritable pmd's, but only * after we've gone through a COW cycle and they are dirty. */ static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) { return pmd_write(pmd) || ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); } struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd, unsigned int flags) { struct mm_struct *mm = vma->vm_mm; struct page *page = NULL; assert_spin_locked(pmd_lockptr(mm, pmd)); if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) goto out; /* Avoid dumping huge zero page */ if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) return ERR_PTR(-EFAULT); /* Full NUMA hinting faults to serialise migration in fault paths */ if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) goto out; page = pmd_page(*pmd); VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); if (!try_grab_page(page, flags)) return ERR_PTR(-ENOMEM); if (flags & FOLL_TOUCH) touch_pmd(vma, addr, pmd, flags); if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { /* * We don't mlock() pte-mapped THPs. This way we can avoid * leaking mlocked pages into non-VM_LOCKED VMAs. * * For anon THP: * * In most cases the pmd is the only mapping of the page as we * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for * writable private mappings in populate_vma_page_range(). * * The only scenario when we have the page shared here is if we * mlocking read-only mapping shared over fork(). We skip * mlocking such pages. * * For file THP: * * We can expect PageDoubleMap() to be stable under page lock: * for file pages we set it in page_add_file_rmap(), which * requires page to be locked. */ if (PageAnon(page) && compound_mapcount(page) != 1) goto skip_mlock; if (PageDoubleMap(page) || !page->mapping) goto skip_mlock; if (!trylock_page(page)) goto skip_mlock; if (page->mapping && !PageDoubleMap(page)) mlock_vma_page(page); unlock_page(page); } skip_mlock: page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page); out: return page; } /* NUMA hinting page fault entry point for trans huge pmds */ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) { struct vm_area_struct *vma = vmf->vma; struct anon_vma *anon_vma = NULL; struct page *page; unsigned long haddr = vmf->address & HPAGE_PMD_MASK; int page_nid = NUMA_NO_NODE, this_nid = numa_node_id(); int target_nid, last_cpupid = -1; bool page_locked; bool migrated = false; bool was_writable; int flags = 0; vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); if (unlikely(!pmd_same(pmd, *vmf->pmd))) goto out_unlock; /* * If there are potential migrations, wait for completion and retry * without disrupting NUMA hinting information. Do not relock and * check_same as the page may no longer be mapped. */ if (unlikely(pmd_trans_migrating(*vmf->pmd))) { page = pmd_page(*vmf->pmd); if (!get_page_unless_zero(page)) goto out_unlock; spin_unlock(vmf->ptl); put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE); goto out; } page = pmd_page(pmd); BUG_ON(is_huge_zero_page(page)); page_nid = page_to_nid(page); last_cpupid = page_cpupid_last(page); count_vm_numa_event(NUMA_HINT_FAULTS); if (page_nid == this_nid) { count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); flags |= TNF_FAULT_LOCAL; } /* See similar comment in do_numa_page for explanation */ if (!pmd_savedwrite(pmd)) flags |= TNF_NO_GROUP; /* * Acquire the page lock to serialise THP migrations but avoid dropping * page_table_lock if at all possible */ page_locked = trylock_page(page); target_nid = mpol_misplaced(page, vma, haddr); if (target_nid == NUMA_NO_NODE) { /* If the page was locked, there are no parallel migrations */ if (page_locked) goto clear_pmdnuma; } /* Migration could have started since the pmd_trans_migrating check */ if (!page_locked) { page_nid = NUMA_NO_NODE; if (!get_page_unless_zero(page)) goto out_unlock; spin_unlock(vmf->ptl); put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE); goto out; } /* * Page is misplaced. Page lock serialises migrations. Acquire anon_vma * to serialises splits */ get_page(page); spin_unlock(vmf->ptl); anon_vma = page_lock_anon_vma_read(page); /* Confirm the PMD did not change while page_table_lock was released */ spin_lock(vmf->ptl); if (unlikely(!pmd_same(pmd, *vmf->pmd))) { unlock_page(page); put_page(page); page_nid = NUMA_NO_NODE; goto out_unlock; } /* Bail if we fail to protect against THP splits for any reason */ if (unlikely(!anon_vma)) { put_page(page); page_nid = NUMA_NO_NODE; goto clear_pmdnuma; } /* * Since we took the NUMA fault, we must have observed the !accessible * bit. Make sure all other CPUs agree with that, to avoid them * modifying the page we're about to migrate. * * Must be done under PTL such that we'll observe the relevant * inc_tlb_flush_pending(). * * We are not sure a pending tlb flush here is for a huge page * mapping or not. Hence use the tlb range variant */ if (mm_tlb_flush_pending(vma->vm_mm)) { flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); /* * change_huge_pmd() released the pmd lock before * invalidating the secondary MMUs sharing the primary * MMU pagetables (with ->invalidate_range()). The * mmu_notifier_invalidate_range_end() (which * internally calls ->invalidate_range()) in * change_pmd_range() will run after us, so we can't * rely on it here and we need an explicit invalidate. */ mmu_notifier_invalidate_range(vma->vm_mm, haddr, haddr + HPAGE_PMD_SIZE); } /* * Migrate the THP to the requested node, returns with page unlocked * and access rights restored. */ spin_unlock(vmf->ptl); migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma, vmf->pmd, pmd, vmf->address, page, target_nid); if (migrated) { flags |= TNF_MIGRATED; page_nid = target_nid; } else flags |= TNF_MIGRATE_FAIL; goto out; clear_pmdnuma: BUG_ON(!PageLocked(page)); was_writable = pmd_savedwrite(pmd); pmd = pmd_modify(pmd, vma->vm_page_prot); pmd = pmd_mkyoung(pmd); if (was_writable) pmd = pmd_mkwrite(pmd); set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd); update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); unlock_page(page); out_unlock: spin_unlock(vmf->ptl); out: if (anon_vma) page_unlock_anon_vma_read(anon_vma); if (page_nid != NUMA_NO_NODE) task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags); return 0; } /* * Return true if we do MADV_FREE successfully on entire pmd page. * Otherwise, return false. */ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, unsigned long next) { spinlock_t *ptl; pmd_t orig_pmd; struct page *page; struct mm_struct *mm = tlb->mm; bool ret = false; tlb_change_page_size(tlb, HPAGE_PMD_SIZE); ptl = pmd_trans_huge_lock(pmd, vma); if (!ptl) goto out_unlocked; orig_pmd = *pmd; if (is_huge_zero_pmd(orig_pmd)) goto out; if (unlikely(!pmd_present(orig_pmd))) { VM_BUG_ON(thp_migration_supported() && !is_pmd_migration_entry(orig_pmd)); goto out; } page = pmd_page(orig_pmd); /* * If other processes are mapping this page, we couldn't discard * the page unless they all do MADV_FREE so let's skip the page. */ if (page_mapcount(page) != 1) goto out; if (!trylock_page(page)) goto out; /* * If user want to discard part-pages of THP, split it so MADV_FREE * will deactivate only them. */ if (next - addr != HPAGE_PMD_SIZE) { get_page(page); spin_unlock(ptl); split_huge_page(page); unlock_page(page); put_page(page); goto out_unlocked; } if (PageDirty(page)) ClearPageDirty(page); unlock_page(page); if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { pmdp_invalidate(vma, addr, pmd); orig_pmd = pmd_mkold(orig_pmd); orig_pmd = pmd_mkclean(orig_pmd); set_pmd_at(mm, addr, pmd, orig_pmd); tlb_remove_pmd_tlb_entry(tlb, pmd, addr); } mark_page_lazyfree(page); ret = true; out: spin_unlock(ptl); out_unlocked: return ret; } static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) { pgtable_t pgtable; pgtable = pgtable_trans_huge_withdraw(mm, pmd); pte_free(mm, pgtable); mm_dec_nr_ptes(mm); } int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr) { pmd_t orig_pmd; spinlock_t *ptl; tlb_change_page_size(tlb, HPAGE_PMD_SIZE); ptl = __pmd_trans_huge_lock(pmd, vma); if (!ptl) return 0; /* * For architectures like ppc64 we look at deposited pgtable * when calling pmdp_huge_get_and_clear. So do the * pgtable_trans_huge_withdraw after finishing pmdp related * operations. */ orig_pmd = pmdp_huge_get_and_clear_full(vma, addr, pmd, tlb->fullmm); tlb_remove_pmd_tlb_entry(tlb, pmd, addr); if (vma_is_special_huge(vma)) { if (arch_needs_pgtable_deposit()) zap_deposited_table(tlb->mm, pmd); spin_unlock(ptl); if (is_huge_zero_pmd(orig_pmd)) tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); } else if (is_huge_zero_pmd(orig_pmd)) { zap_deposited_table(tlb->mm, pmd); spin_unlock(ptl); tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); } else { struct page *page = NULL; int flush_needed = 1; if (pmd_present(orig_pmd)) { page = pmd_page(orig_pmd); page_remove_rmap(page, true); VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); VM_BUG_ON_PAGE(!PageHead(page), page); } else if (thp_migration_supported()) { swp_entry_t entry; VM_BUG_ON(!is_pmd_migration_entry(orig_pmd)); entry = pmd_to_swp_entry(orig_pmd); page = pfn_to_page(swp_offset(entry)); flush_needed = 0; } else WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!"); if (PageAnon(page)) { zap_deposited_table(tlb->mm, pmd); add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); } else { if (arch_needs_pgtable_deposit()) zap_deposited_table(tlb->mm, pmd); add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR); } spin_unlock(ptl); if (flush_needed) tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); } return 1; } #ifndef pmd_move_must_withdraw static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, spinlock_t *old_pmd_ptl, struct vm_area_struct *vma) { /* * With split pmd lock we also need to move preallocated * PTE page table if new_pmd is on different PMD page table. * * We also don't deposit and withdraw tables for file pages. */ return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma); } #endif static pmd_t move_soft_dirty_pmd(pmd_t pmd) { #ifdef CONFIG_MEM_SOFT_DIRTY if (unlikely(is_pmd_migration_entry(pmd))) pmd = pmd_swp_mksoft_dirty(pmd); else if (pmd_present(pmd)) pmd = pmd_mksoft_dirty(pmd); #endif return pmd; } bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd) { spinlock_t *old_ptl, *new_ptl; pmd_t pmd; struct mm_struct *mm = vma->vm_mm; bool force_flush = false; /* * The destination pmd shouldn't be established, free_pgtables() * should have release it. */ if (WARN_ON(!pmd_none(*new_pmd))) { VM_BUG_ON(pmd_trans_huge(*new_pmd)); return false; } /* * We don't have to worry about the ordering of src and dst * ptlocks because exclusive mmap_lock prevents deadlock. */ old_ptl = __pmd_trans_huge_lock(old_pmd, vma); if (old_ptl) { new_ptl = pmd_lockptr(mm, new_pmd); if (new_ptl != old_ptl) spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); if (pmd_present(pmd)) force_flush = true; VM_BUG_ON(!pmd_none(*new_pmd)); if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) { pgtable_t pgtable; pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); pgtable_trans_huge_deposit(mm, new_pmd, pgtable); } pmd = move_soft_dirty_pmd(pmd); set_pmd_at(mm, new_addr, new_pmd, pmd); if (force_flush) flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); if (new_ptl != old_ptl) spin_unlock(new_ptl); spin_unlock(old_ptl); return true; } return false; } /* * Returns * - 0 if PMD could not be locked * - 1 if PMD was locked but protections unchange and TLB flush unnecessary * - HPAGE_PMD_NR is protections changed and TLB flush necessary */ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, pgprot_t newprot, unsigned long cp_flags) { struct mm_struct *mm = vma->vm_mm; spinlock_t *ptl; pmd_t entry; bool preserve_write; int ret; bool prot_numa = cp_flags & MM_CP_PROT_NUMA; bool uffd_wp = cp_flags & MM_CP_UFFD_WP; bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; ptl = __pmd_trans_huge_lock(pmd, vma); if (!ptl) return 0; preserve_write = prot_numa && pmd_write(*pmd); ret = 1; #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION if (is_swap_pmd(*pmd)) { swp_entry_t entry = pmd_to_swp_entry(*pmd); VM_BUG_ON(!is_pmd_migration_entry(*pmd)); if (is_write_migration_entry(entry)) { pmd_t newpmd; /* * A protection check is difficult so * just be safe and disable write */ make_migration_entry_read(&entry); newpmd = swp_entry_to_pmd(entry); if (pmd_swp_soft_dirty(*pmd)) newpmd = pmd_swp_mksoft_dirty(newpmd); set_pmd_at(mm, addr, pmd, newpmd); } goto unlock; } #endif /* * Avoid trapping faults against the zero page. The read-only * data is likely to be read-cached on the local CPU and * local/remote hits to the zero page are not interesting. */ if (prot_numa && is_huge_zero_pmd(*pmd)) goto unlock; if (prot_numa && pmd_protnone(*pmd)) goto unlock; /* * In case prot_numa, we are under mmap_read_lock(mm). It's critical * to not clear pmd intermittently to avoid race with MADV_DONTNEED * which is also under mmap_read_lock(mm): * * CPU0: CPU1: * change_huge_pmd(prot_numa=1) * pmdp_huge_get_and_clear_notify() * madvise_dontneed() * zap_pmd_range() * pmd_trans_huge(*pmd) == 0 (without ptl) * // skip the pmd * set_pmd_at(); * // pmd is re-established * * The race makes MADV_DONTNEED miss the huge pmd and don't clear it * which may break userspace. * * pmdp_invalidate() is required to make sure we don't miss * dirty/young flags set by hardware. */ entry = pmdp_invalidate(vma, addr, pmd); entry = pmd_modify(entry, newprot); if (preserve_write) entry = pmd_mk_savedwrite(entry); if (uffd_wp) { entry = pmd_wrprotect(entry); entry = pmd_mkuffd_wp(entry); } else if (uffd_wp_resolve) { /* * Leave the write bit to be handled by PF interrupt * handler, then things like COW could be properly * handled. */ entry = pmd_clear_uffd_wp(entry); } ret = HPAGE_PMD_NR; set_pmd_at(mm, addr, pmd, entry); BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry)); unlock: spin_unlock(ptl); return ret; } /* * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise. * * Note that if it returns page table lock pointer, this routine returns without * unlocking page table lock. So callers must unlock it. */ spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) { spinlock_t *ptl; ptl = pmd_lock(vma->vm_mm, pmd); if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd))) return ptl; spin_unlock(ptl); return NULL; } /* * Returns true if a given pud maps a thp, false otherwise. * * Note that if it returns true, this routine returns without unlocking page * table lock. So callers must unlock it. */ spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma) { spinlock_t *ptl; ptl = pud_lock(vma->vm_mm, pud); if (likely(pud_trans_huge(*pud) || pud_devmap(*pud))) return ptl; spin_unlock(ptl); return NULL; } #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, pud_t *pud, unsigned long addr) { spinlock_t *ptl; ptl = __pud_trans_huge_lock(pud, vma); if (!ptl) return 0; /* * For architectures like ppc64 we look at deposited pgtable * when calling pudp_huge_get_and_clear. So do the * pgtable_trans_huge_withdraw after finishing pudp related * operations. */ pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm); tlb_remove_pud_tlb_entry(tlb, pud, addr); if (vma_is_special_huge(vma)) { spin_unlock(ptl); /* No zero page support yet */ } else { /* No support for anonymous PUD pages yet */ BUG(); } return 1; } static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud, unsigned long haddr) { VM_BUG_ON(haddr & ~HPAGE_PUD_MASK); VM_BUG_ON_VMA(vma->vm_start > haddr, vma); VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma); VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud)); count_vm_event(THP_SPLIT_PUD); pudp_huge_clear_flush_notify(vma, haddr, pud); } void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud, unsigned long address) { spinlock_t *ptl; struct mmu_notifier_range range; mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, address & HPAGE_PUD_MASK, (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE); mmu_notifier_invalidate_range_start(&range); ptl = pud_lock(vma->vm_mm, pud); if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud))) goto out; __split_huge_pud_locked(vma, pud, range.start); out: spin_unlock(ptl); /* * No need to double call mmu_notifier->invalidate_range() callback as * the above pudp_huge_clear_flush_notify() did already call it. */ mmu_notifier_invalidate_range_only_end(&range); } #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd) { struct mm_struct *mm = vma->vm_mm; pgtable_t pgtable; pmd_t _pmd; int i; /* * Leave pmd empty until pte is filled note that it is fine to delay * notification until mmu_notifier_invalidate_range_end() as we are * replacing a zero pmd write protected page with a zero pte write * protected page. * * See Documentation/vm/mmu_notifier.rst */ pmdp_huge_clear_flush(vma, haddr, pmd); pgtable = pgtable_trans_huge_withdraw(mm, pmd); pmd_populate(mm, &_pmd, pgtable); for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { pte_t *pte, entry; entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); entry = pte_mkspecial(entry); pte = pte_offset_map(&_pmd, haddr); VM_BUG_ON(!pte_none(*pte)); set_pte_at(mm, haddr, pte, entry); pte_unmap(pte); } smp_wmb(); /* make pte visible before pmd */ pmd_populate(mm, pmd, pgtable); } static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, unsigned long haddr, bool freeze) { struct mm_struct *mm = vma->vm_mm; struct page *page; pgtable_t pgtable; pmd_t old_pmd, _pmd; bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; unsigned long addr; int i; VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); VM_BUG_ON_VMA(vma->vm_start > haddr, vma); VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)); count_vm_event(THP_SPLIT_PMD); if (!vma_is_anonymous(vma)) { _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); /* * We are going to unmap this huge page. So * just go ahead and zap it */ if (arch_needs_pgtable_deposit()) zap_deposited_table(mm, pmd); if (vma_is_special_huge(vma)) return; page = pmd_page(_pmd); if (!PageDirty(page) && pmd_dirty(_pmd)) set_page_dirty(page); if (!PageReferenced(page) && pmd_young(_pmd)) SetPageReferenced(page); page_remove_rmap(page, true); put_page(page); add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR); return; } else if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) { /* * FIXME: Do we want to invalidate secondary mmu by calling * mmu_notifier_invalidate_range() see comments below inside * __split_huge_pmd() ? * * We are going from a zero huge page write protected to zero * small page also write protected so it does not seems useful * to invalidate secondary mmu at this time. */ return __split_huge_zero_page_pmd(vma, haddr, pmd); } /* * Up to this point the pmd is present and huge and userland has the * whole access to the hugepage during the split (which happens in * place). If we overwrite the pmd with the not-huge version pointing * to the pte here (which of course we could if all CPUs were bug * free), userland could trigger a small page size TLB miss on the * small sized TLB while the hugepage TLB entry is still established in * the huge TLB. Some CPU doesn't like that. * See http://support.amd.com/TechDocs/41322_10h_Rev_Gd.pdf, Erratum * 383 on page 105. Intel should be safe but is also warns that it's * only safe if the permission and cache attributes of the two entries * loaded in the two TLB is identical (which should be the case here). * But it is generally safer to never allow small and huge TLB entries * for the same virtual address to be loaded simultaneously. So instead * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the * current pmd notpresent (atomically because here the pmd_trans_huge * must remain set at all times on the pmd until the split is complete * for this pmd), then we flush the SMP TLB and finally we write the * non-huge version of the pmd entry with pmd_populate. */ old_pmd = pmdp_invalidate(vma, haddr, pmd); pmd_migration = is_pmd_migration_entry(old_pmd); if (unlikely(pmd_migration)) { swp_entry_t entry; entry = pmd_to_swp_entry(old_pmd); page = pfn_to_page(swp_offset(entry)); write = is_write_migration_entry(entry); young = false; soft_dirty = pmd_swp_soft_dirty(old_pmd); uffd_wp = pmd_swp_uffd_wp(old_pmd); } else { page = pmd_page(old_pmd); if (pmd_dirty(old_pmd)) SetPageDirty(page); write = pmd_write(old_pmd); young = pmd_young(old_pmd); soft_dirty = pmd_soft_dirty(old_pmd); uffd_wp = pmd_uffd_wp(old_pmd); } VM_BUG_ON_PAGE(!page_count(page), page); page_ref_add(page, HPAGE_PMD_NR - 1); /* * Withdraw the table only after we mark the pmd entry invalid. * This's critical for some architectures (Power). */ pgtable = pgtable_trans_huge_withdraw(mm, pmd); pmd_populate(mm, &_pmd, pgtable); for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { pte_t entry, *pte; /* * Note that NUMA hinting access restrictions are not * transferred to avoid any possibility of altering * permissions across VMAs. */ if (freeze || pmd_migration) { swp_entry_t swp_entry; swp_entry = make_migration_entry(page + i, write); entry = swp_entry_to_pte(swp_entry); if (soft_dirty) entry = pte_swp_mksoft_dirty(entry); if (uffd_wp) entry = pte_swp_mkuffd_wp(entry); } else { entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); entry = maybe_mkwrite(entry, vma); if (!write) entry = pte_wrprotect(entry); if (!young) entry = pte_mkold(entry); if (soft_dirty) entry = pte_mksoft_dirty(entry); if (uffd_wp) entry = pte_mkuffd_wp(entry); } pte = pte_offset_map(&_pmd, addr); BUG_ON(!pte_none(*pte)); set_pte_at(mm, addr, pte, entry); if (!pmd_migration) atomic_inc(&page[i]._mapcount); pte_unmap(pte); } if (!pmd_migration) { /* * Set PG_double_map before dropping compound_mapcount to avoid * false-negative page_mapped(). */ if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { for (i = 0; i < HPAGE_PMD_NR; i++) atomic_inc(&page[i]._mapcount); } lock_page_memcg(page); if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { /* Last compound_mapcount is gone. */ __mod_lruvec_page_state(page, NR_ANON_THPS, -HPAGE_PMD_NR); if (TestClearPageDoubleMap(page)) { /* No need in mapcount reference anymore */ for (i = 0; i < HPAGE_PMD_NR; i++) atomic_dec(&page[i]._mapcount); } } unlock_page_memcg(page); } smp_wmb(); /* make pte visible before pmd */ pmd_populate(mm, pmd, pgtable); if (freeze) { for (i = 0; i < HPAGE_PMD_NR; i++) { page_remove_rmap(page + i, false); put_page(page + i); } } } void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, unsigned long address, bool freeze, struct page *page) { spinlock_t *ptl; struct mmu_notifier_range range; bool do_unlock_page = false; pmd_t _pmd; mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, address & HPAGE_PMD_MASK, (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 entries, we need a page to check * pmd against. Otherwise we can end up replacing wrong page. */ VM_BUG_ON(freeze && !page); if (page) { VM_WARN_ON_ONCE(!PageLocked(page)); if (page != pmd_page(*pmd)) goto out; } repeat: if (pmd_trans_huge(*pmd)) { if (!page) { page = pmd_page(*pmd); /* * An anonymous page must be locked, to ensure that a * concurrent reuse_swap_page() sees stable mapcount; * but reuse_swap_page() is not used on shmem or file, * and page lock must not be taken when zap_pmd_range() * calls __split_huge_pmd() while i_mmap_lock is held. */ if (PageAnon(page)) { if (unlikely(!trylock_page(page))) { get_page(page); _pmd = *pmd; spin_unlock(ptl); lock_page(page); spin_lock(ptl); if (unlikely(!pmd_same(*pmd, _pmd))) { unlock_page(page); put_page(page); page = NULL; goto repeat; } put_page(page); } do_unlock_page = true; } } if (PageMlocked(page)) clear_page_mlock(page); } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) goto out; __split_huge_pmd_locked(vma, pmd, range.start, freeze); out: spin_unlock(ptl); if (do_unlock_page) unlock_page(page); /* * No need to double call mmu_notifier->invalidate_range() callback. * They are 3 cases to consider inside __split_huge_pmd_locked(): * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious * 2) __split_huge_zero_page_pmd() read only zero page and any write * fault will trigger a flush_notify before pointing to a new page * (it is fine if the secondary mmu keeps pointing to the old zero * page in the meantime) * 3) Split a huge pmd into pte pointing to the same page. No need * to invalidate secondary tlb entry they are all still valid. * any further changes to individual pte will notify. So no need * to call mmu_notifier->invalidate_range() */ mmu_notifier_invalidate_range_only_end(&range); } void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, bool freeze, struct page *page) { pgd_t *pgd; p4d_t *p4d; pud_t *pud; pmd_t *pmd; pgd = pgd_offset(vma->vm_mm, address); if (!pgd_present(*pgd)) return; p4d = p4d_offset(pgd, address); if (!p4d_present(*p4d)) return; pud = pud_offset(p4d, address); if (!pud_present(*pud)) return; pmd = pmd_offset(pud, address); __split_huge_pmd(vma, pmd, address, freeze, page); } static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address) { /* * If the new address isn't hpage aligned and it could previously * contain an hugepage: check if we need to split an huge pmd. */ if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) && range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE), ALIGN(address, HPAGE_PMD_SIZE))) split_huge_pmd_address(vma, address, false, NULL); } void vma_adjust_trans_huge(struct vm_area_struct *vma, unsigned long start, unsigned long end, long adjust_next) { /* Check if we need to split start first. */ split_huge_pmd_if_needed(vma, start); /* Check if we need to split end next. */ split_huge_pmd_if_needed(vma, end); /* * If we're also updating the vma->vm_next->vm_start, * check if we need to split it. */ if (adjust_next > 0) { struct vm_area_struct *next = vma->vm_next; unsigned long nstart = next->vm_start; nstart += adjust_next; split_huge_pmd_if_needed(next, nstart); } } static void unmap_page(struct page *page) { enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; bool unmap_success; VM_BUG_ON_PAGE(!PageHead(page), page); if (PageAnon(page)) ttu_flags |= TTU_SPLIT_FREEZE; unmap_success = try_to_unmap(page, ttu_flags); VM_BUG_ON_PAGE(!unmap_success, page); } static void remap_page(struct page *page, unsigned int nr) { int i; if (PageTransHuge(page)) { remove_migration_ptes(page, page, true); } else { for (i = 0; i < nr; i++) remove_migration_ptes(page + i, page + i, true); } } static void lru_add_page_tail(struct page *head, struct page *tail, struct lruvec *lruvec, struct list_head *list) { VM_BUG_ON_PAGE(!PageHead(head), head); VM_BUG_ON_PAGE(PageCompound(tail), head); VM_BUG_ON_PAGE(PageLRU(tail), head); lockdep_assert_held(&lruvec->lru_lock); if (list) { /* page reclaim is reclaiming a huge page */ VM_WARN_ON(PageLRU(head)); get_page(tail); list_add_tail(&tail->lru, list); } else { /* head is still on lru (and we have it frozen) */ VM_WARN_ON(!PageLRU(head)); SetPageLRU(tail); list_add_tail(&tail->lru, &head->lru); } } static void __split_huge_page_tail(struct page *head, int tail, struct lruvec *lruvec, struct list_head *list) { struct page *page_tail = head + tail; VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); /* * Clone page flags before unfreezing refcount. * * After successful get_page_unless_zero() might follow flags change, * for example lock_page() which set PG_waiters. */ page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; page_tail->flags |= (head->flags & ((1L << PG_referenced) | (1L << PG_swapbacked) | (1L << PG_swapcache) | (1L << PG_mlocked) | (1L << PG_uptodate) | (1L << PG_active) | (1L << PG_workingset) | (1L << PG_locked) | (1L << PG_unevictable) | #ifdef CONFIG_64BIT (1L << PG_arch_2) | #endif (1L << PG_dirty))); /* ->mapping in first tail page is compound_mapcount */ VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, page_tail); page_tail->mapping = head->mapping; page_tail->index = head->index + tail; /* Page flags must be visible before we make the page non-compound. */ smp_wmb(); /* * Clear PageTail before unfreezing page refcount. * * After successful get_page_unless_zero() might follow put_page() * which needs correct compound_head(). */ clear_compound_head(page_tail); /* Finally unfreeze refcount. Additional reference from page cache. */ page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) || PageSwapCache(head))); if (page_is_young(head)) set_page_young(page_tail); if (page_is_idle(head)) set_page_idle(page_tail); page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); /* * always add to the tail because some iterators expect new * pages to show after the currently processed elements - e.g. * migrate_pages */ lru_add_page_tail(head, page_tail, lruvec, list); } static void __split_huge_page(struct page *page, struct list_head *list, pgoff_t end) { struct page *head = compound_head(page); struct lruvec *lruvec; struct address_space *swap_cache = NULL; unsigned long offset = 0; unsigned int nr = thp_nr_pages(head); int i; /* complete memcg works before add pages to LRU */ split_page_memcg(head, nr); if (PageAnon(head) && PageSwapCache(head)) { swp_entry_t entry = { .val = page_private(head) }; offset = swp_offset(entry); swap_cache = swap_address_space(entry); xa_lock(&swap_cache->i_pages); } /* lock lru list/PageCompound, ref freezed by page_ref_freeze */ lruvec = lock_page_lruvec(head); for (i = nr - 1; i >= 1; i--) { __split_huge_page_tail(head, i, lruvec, list); /* Some pages can be beyond i_size: drop them from page cache */ if (head[i].index >= end) { ClearPageDirty(head + i); __delete_from_page_cache(head + i, NULL); if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head)) shmem_uncharge(head->mapping->host, 1); put_page(head + i); } else if (!PageAnon(page)) { __xa_store(&head->mapping->i_pages, head[i].index, head + i, 0); } else if (swap_cache) { __xa_store(&swap_cache->i_pages, offset + i, head + i, 0); } } ClearPageCompound(head); unlock_page_lruvec(lruvec); /* Caller disabled irqs, so they are still disabled here */ split_page_owner(head, nr); /* See comment in __split_huge_page_tail() */ if (PageAnon(head)) { /* Additional pin to swap cache */ if (PageSwapCache(head)) { page_ref_add(head, 2); xa_unlock(&swap_cache->i_pages); } else { page_ref_inc(head); } } else { /* Additional pin to page cache */ page_ref_add(head, 2); xa_unlock(&head->mapping->i_pages); } local_irq_enable(); remap_page(head, nr); if (PageSwapCache(head)) { swp_entry_t entry = { .val = page_private(head) }; split_swap_cluster(entry); } for (i = 0; i < nr; i++) { struct page *subpage = head + i; if (subpage == page) continue; unlock_page(subpage); /* * Subpages may be freed if there wasn't any mapping * like if add_to_swap() is running on a lru page that * had its mapping zapped. And freeing these pages * requires taking the lru_lock so we do the put_page * of the tail pages after the split is complete. */ put_page(subpage); } } int total_mapcount(struct page *page) { int i, compound, nr, ret; VM_BUG_ON_PAGE(PageTail(page), page); if (likely(!PageCompound(page))) return atomic_read(&page->_mapcount) + 1; compound = compound_mapcount(page); nr = compound_nr(page); if (PageHuge(page)) return compound; ret = compound; for (i = 0; i < nr; i++) ret += atomic_read(&page[i]._mapcount) + 1; /* File pages has compound_mapcount included in _mapcount */ if (!PageAnon(page)) return ret - compound * nr; if (PageDoubleMap(page)) ret -= nr; return ret; } /* * This calculates accurately how many mappings a transparent hugepage * has (unlike page_mapcount() which isn't fully accurate). This full * accuracy is primarily needed to know if copy-on-write faults can * reuse the page and change the mapping to read-write instead of * copying them. At the same time this returns the total_mapcount too. * * The function returns the highest mapcount any one of the subpages * has. If the return value is one, even if different processes are * mapping different subpages of the transparent hugepage, they can * all reuse it, because each process is reusing a different subpage. * * The total_mapcount is instead counting all virtual mappings of the * subpages. If the total_mapcount is equal to "one", it tells the * caller all mappings belong to the same "mm" and in turn the * anon_vma of the transparent hugepage can become the vma->anon_vma * local one as no other process may be mapping any of the subpages. * * It would be more accurate to replace page_mapcount() with * page_trans_huge_mapcount(), however we only use * page_trans_huge_mapcount() in the copy-on-write faults where we * need full accuracy to avoid breaking page pinning, because * page_trans_huge_mapcount() is slower than page_mapcount(). */ int page_trans_huge_mapcount(struct page *page, int *total_mapcount) { int i, ret, _total_mapcount, mapcount; /* hugetlbfs shouldn't call it */ VM_BUG_ON_PAGE(PageHuge(page), page); if (likely(!PageTransCompound(page))) { mapcount = atomic_read(&page->_mapcount) + 1; if (total_mapcount) *total_mapcount = mapcount; return mapcount; } page = compound_head(page); _total_mapcount = ret = 0; for (i = 0; i < thp_nr_pages(page); i++) { mapcount = atomic_read(&page[i]._mapcount) + 1; ret = max(ret, mapcount); _total_mapcount += mapcount; } if (PageDoubleMap(page)) { ret -= 1; _total_mapcount -= thp_nr_pages(page); } mapcount = compound_mapcount(page); ret += mapcount; _total_mapcount += mapcount; if (total_mapcount) *total_mapcount = _total_mapcount; return ret; } /* Racy check whether the huge page can be split */ bool can_split_huge_page(struct page *page, int *pextra_pins) { int extra_pins; /* Additional pins from page cache */ if (PageAnon(page)) extra_pins = PageSwapCache(page) ? thp_nr_pages(page) : 0; else extra_pins = thp_nr_pages(page); if (pextra_pins) *pextra_pins = extra_pins; return total_mapcount(page) == page_count(page) - extra_pins - 1; } /* * This function splits huge page into normal pages. @page can point to any * subpage of huge page to split. Split doesn't change the position of @page. * * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. * The huge page must be locked. * * If @list is null, tail pages will be added to LRU list, otherwise, to @list. * * Both head page and tail pages will inherit mapping, flags, and so on from * the hugepage. * * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if * they are not mapped. * * Returns 0 if the hugepage is split successfully. * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under * us. */ int split_huge_page_to_list(struct page *page, struct list_head *list) { struct page *head = compound_head(page); struct deferred_split *ds_queue = get_deferred_split_queue(head); struct anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; int count, mapcount, extra_pins, ret; pgoff_t end; VM_BUG_ON_PAGE(is_huge_zero_page(head), head); VM_BUG_ON_PAGE(!PageLocked(head), head); VM_BUG_ON_PAGE(!PageCompound(head), head); if (PageWriteback(head)) return -EBUSY; if (PageAnon(head)) { /* * The caller does not necessarily hold an mmap_lock that would * prevent the anon_vma disappearing so we first we take a * reference to it and then lock the anon_vma for write. This * is similar to page_lock_anon_vma_read except the write lock * is taken to serialise against parallel split or collapse * operations. */ anon_vma = page_get_anon_vma(head); if (!anon_vma) { ret = -EBUSY; goto out; } end = -1; mapping = NULL; anon_vma_lock_write(anon_vma); } else { mapping = head->mapping; /* Truncated ? */ if (!mapping) { ret = -EBUSY; goto out; } anon_vma = NULL; i_mmap_lock_read(mapping); /* *__split_huge_page() may need to trim off pages beyond EOF: * but on 32-bit, i_size_read() takes an irq-unsafe seqlock, * which cannot be nested inside the page tree lock. So note * end now: i_size itself may be changed at any moment, but * head page lock is good enough to serialize the trimming. */ end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); } /* * Racy check if we can split the page, before unmap_page() will * split PMDs */ if (!can_split_huge_page(head, &extra_pins)) { ret = -EBUSY; goto out_unlock; } unmap_page(head); VM_BUG_ON_PAGE(compound_mapcount(head), head); /* block interrupt reentry in xa_lock and spinlock */ local_irq_disable(); if (mapping) { XA_STATE(xas, &mapping->i_pages, page_index(head)); /* * Check if the head page is present in page cache. * We assume all tail are present too, if head is there. */ xa_lock(&mapping->i_pages); if (xas_load(&xas) != head) goto fail; } /* Prevent deferred_split_scan() touching ->_refcount */ spin_lock(&ds_queue->split_queue_lock); count = page_count(head); mapcount = total_mapcount(head); if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { if (!list_empty(page_deferred_list(head))) { ds_queue->split_queue_len--; list_del(page_deferred_list(head)); } spin_unlock(&ds_queue->split_queue_lock); if (mapping) { int nr = thp_nr_pages(head); if (PageSwapBacked(head)) __mod_lruvec_page_state(head, NR_SHMEM_THPS, -nr); else __mod_lruvec_page_state(head, NR_FILE_THPS, -nr); } __split_huge_page(page, list, end); ret = 0; } else { if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { pr_alert("total_mapcount: %u, page_count(): %u\n", mapcount, count); if (PageTail(page)) dump_page(head, NULL); dump_page(page, "total_mapcount(head) > 0"); BUG(); } spin_unlock(&ds_queue->split_queue_lock); fail: if (mapping) xa_unlock(&mapping->i_pages); local_irq_enable(); remap_page(head, thp_nr_pages(head)); ret = -EBUSY; } out_unlock: if (anon_vma) { anon_vma_unlock_write(anon_vma); put_anon_vma(anon_vma); } if (mapping) i_mmap_unlock_read(mapping); out: count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); return ret; } void free_transhuge_page(struct page *page) { struct deferred_split *ds_queue = get_deferred_split_queue(page); unsigned long flags; spin_lock_irqsave(&ds_queue->split_queue_lock, flags); if (!list_empty(page_deferred_list(page))) { ds_queue->split_queue_len--; list_del(page_deferred_list(page)); } spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); free_compound_page(page); } void deferred_split_huge_page(struct page *page) { struct deferred_split *ds_queue = get_deferred_split_queue(page); #ifdef CONFIG_MEMCG struct mem_cgroup *memcg = page_memcg(compound_head(page)); #endif unsigned long flags; VM_BUG_ON_PAGE(!PageTransHuge(page), page); /* * The try_to_unmap() in page reclaim path might reach here too, * this may cause a race condition to corrupt deferred split queue. * And, if page reclaim is already handling the same page, it is * unnecessary to handle it again in shrinker. * * Check PageSwapCache to determine if the page is being * handled by page reclaim since THP swap would add the page into * swap cache before calling try_to_unmap(). */ if (PageSwapCache(page)) return; spin_lock_irqsave(&ds_queue->split_queue_lock, flags); if (list_empty(page_deferred_list(page))) { count_vm_event(THP_DEFERRED_SPLIT_PAGE); list_add_tail(page_deferred_list(page), &ds_queue->split_queue); ds_queue->split_queue_len++; #ifdef CONFIG_MEMCG if (memcg) memcg_set_shrinker_bit(memcg, page_to_nid(page), deferred_split_shrinker.id); #endif } spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); } static unsigned long deferred_split_count(struct shrinker *shrink, struct shrink_control *sc) { struct pglist_data *pgdata = NODE_DATA(sc->nid); struct deferred_split *ds_queue = &pgdata->deferred_split_queue; #ifdef CONFIG_MEMCG if (sc->memcg) ds_queue = &sc->memcg->deferred_split_queue; #endif return READ_ONCE(ds_queue->split_queue_len); } static unsigned long deferred_split_scan(struct shrinker *shrink, struct shrink_control *sc) { struct pglist_data *pgdata = NODE_DATA(sc->nid); struct deferred_split *ds_queue = &pgdata->deferred_split_queue; unsigned long flags; LIST_HEAD(list), *pos, *next; struct page *page; int split = 0; #ifdef CONFIG_MEMCG if (sc->memcg) ds_queue = &sc->memcg->deferred_split_queue; #endif spin_lock_irqsave(&ds_queue->split_queue_lock, flags); /* Take pin on all head pages to avoid freeing them under us */ list_for_each_safe(pos, next, &ds_queue->split_queue) { page = list_entry((void *)pos, struct page, mapping); page = compound_head(page); if (get_page_unless_zero(page)) { list_move(page_deferred_list(page), &list); } else { /* We lost race with put_compound_page() */ list_del_init(page_deferred_list(page)); ds_queue->split_queue_len--; } if (!--sc->nr_to_scan) break; } spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); list_for_each_safe(pos, next, &list) { page = list_entry((void *)pos, struct page, mapping); if (!trylock_page(page)) goto next; /* split_huge_page() removes page from list on success */ if (!split_huge_page(page)) split++; unlock_page(page); next: put_page(page); } spin_lock_irqsave(&ds_queue->split_queue_lock, flags); list_splice_tail(&list, &ds_queue->split_queue); spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); /* * Stop shrinker if we didn't split any page, but the queue is empty. * This can happen if pages were freed under us. */ if (!split && list_empty(&ds_queue->split_queue)) return SHRINK_STOP; return split; } static struct shrinker deferred_split_shrinker = { .count_objects = deferred_split_count, .scan_objects = deferred_split_scan, .seeks = DEFAULT_SEEKS, .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE | SHRINKER_NONSLAB, }; #ifdef CONFIG_DEBUG_FS static int split_huge_pages_set(void *data, u64 val) { struct zone *zone; struct page *page; unsigned long pfn, max_zone_pfn; unsigned long total = 0, split = 0; if (val != 1) return -EINVAL; for_each_populated_zone(zone) { max_zone_pfn = zone_end_pfn(zone); for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { if (!pfn_valid(pfn)) continue; page = pfn_to_page(pfn); if (!get_page_unless_zero(page)) continue; if (zone != page_zone(page)) goto next; if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) goto next; total++; lock_page(page); if (!split_huge_page(page)) split++; unlock_page(page); next: put_page(page); } } pr_info("%lu of %lu THP split\n", split, total); return 0; } DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, "%llu\n"); static int __init split_huge_pages_debugfs(void) { debugfs_create_file("split_huge_pages", 0200, NULL, NULL, &split_huge_pages_fops); return 0; } late_initcall(split_huge_pages_debugfs); #endif #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, struct page *page) { struct vm_area_struct *vma = pvmw->vma; struct mm_struct *mm = vma->vm_mm; unsigned long address = pvmw->address; pmd_t pmdval; swp_entry_t entry; pmd_t pmdswp; if (!(pvmw->pmd && !pvmw->pte)) return; flush_cache_range(vma, address, address + HPAGE_PMD_SIZE); pmdval = pmdp_invalidate(vma, address, pvmw->pmd); if (pmd_dirty(pmdval)) set_page_dirty(page); entry = make_migration_entry(page, pmd_write(pmdval)); pmdswp = swp_entry_to_pmd(entry); if (pmd_soft_dirty(pmdval)) pmdswp = pmd_swp_mksoft_dirty(pmdswp); set_pmd_at(mm, address, pvmw->pmd, pmdswp); page_remove_rmap(page, true); put_page(page); } void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) { struct vm_area_struct *vma = pvmw->vma; struct mm_struct *mm = vma->vm_mm; unsigned long address = pvmw->address; unsigned long mmun_start = address & HPAGE_PMD_MASK; pmd_t pmde; swp_entry_t entry; if (!(pvmw->pmd && !pvmw->pte)) return; entry = pmd_to_swp_entry(*pvmw->pmd); get_page(new); pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot)); if (pmd_swp_soft_dirty(*pvmw->pmd)) pmde = pmd_mksoft_dirty(pmde); if (is_write_migration_entry(entry)) pmde = maybe_pmd_mkwrite(pmde, vma); flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE); if (PageAnon(new)) page_add_anon_rmap(new, vma, mmun_start, true); else page_add_file_rmap(new, true); set_pmd_at(mm, mmun_start, pvmw->pmd, pmde); if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new)) mlock_vma_page(new); update_mmu_cache_pmd(vma, address, pvmw->pmd); } #endif