| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * Copyright (C) 2009 Red Hat, Inc. |
| */ |
| |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/mm.h> |
| #include <linux/sched.h> |
| #include <linux/sched/mm.h> |
| #include <linux/sched/coredump.h> |
| #include <linux/sched/numa_balancing.h> |
| #include <linux/highmem.h> |
| #include <linux/hugetlb.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/rmap.h> |
| #include <linux/swap.h> |
| #include <linux/shrinker.h> |
| #include <linux/mm_inline.h> |
| #include <linux/swapops.h> |
| #include <linux/backing-dev.h> |
| #include <linux/dax.h> |
| #include <linux/mm_types.h> |
| #include <linux/khugepaged.h> |
| #include <linux/freezer.h> |
| #include <linux/pfn_t.h> |
| #include <linux/mman.h> |
| #include <linux/memremap.h> |
| #include <linux/pagemap.h> |
| #include <linux/debugfs.h> |
| #include <linux/migrate.h> |
| #include <linux/hashtable.h> |
| #include <linux/userfaultfd_k.h> |
| #include <linux/page_idle.h> |
| #include <linux/shmem_fs.h> |
| #include <linux/oom.h> |
| #include <linux/numa.h> |
| #include <linux/page_owner.h> |
| #include <linux/sched/sysctl.h> |
| #include <linux/memory-tiers.h> |
| #include <linux/compat.h> |
| #include <linux/pgalloc_tag.h> |
| |
| #include <asm/tlb.h> |
| #include <asm/pgalloc.h> |
| #include "internal.h" |
| #include "swap.h" |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/thp.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<<TRANSPARENT_HUGEPAGE_FLAG)| |
| #endif |
| #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE |
| (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| |
| #endif |
| (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)| |
| (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| |
| (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); |
| |
| static struct shrinker *deferred_split_shrinker; |
| static unsigned long deferred_split_count(struct shrinker *shrink, |
| struct shrink_control *sc); |
| static unsigned long deferred_split_scan(struct shrinker *shrink, |
| struct shrink_control *sc); |
| |
| static atomic_t huge_zero_refcount; |
| struct folio *huge_zero_folio __read_mostly; |
| unsigned long huge_zero_pfn __read_mostly = ~0UL; |
| unsigned long huge_anon_orders_always __read_mostly; |
| unsigned long huge_anon_orders_madvise __read_mostly; |
| unsigned long huge_anon_orders_inherit __read_mostly; |
| |
| unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, |
| unsigned long vm_flags, |
| unsigned long tva_flags, |
| unsigned long orders) |
| { |
| bool smaps = tva_flags & TVA_SMAPS; |
| bool in_pf = tva_flags & TVA_IN_PF; |
| bool enforce_sysfs = tva_flags & TVA_ENFORCE_SYSFS; |
| unsigned long supported_orders; |
| |
| /* Check the intersection of requested and supported orders. */ |
| if (vma_is_anonymous(vma)) |
| supported_orders = THP_ORDERS_ALL_ANON; |
| else if (vma_is_dax(vma)) |
| supported_orders = THP_ORDERS_ALL_FILE_DAX; |
| else |
| supported_orders = THP_ORDERS_ALL_FILE_DEFAULT; |
| |
| orders &= supported_orders; |
| if (!orders) |
| return 0; |
| |
| if (!vma->vm_mm) /* vdso */ |
| return 0; |
| |
| /* |
| * Explicitly disabled through madvise or prctl, or some |
| * architectures may disable THP for some mappings, for |
| * example, s390 kvm. |
| * */ |
| if ((vm_flags & VM_NOHUGEPAGE) || |
| test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) |
| return 0; |
| /* |
| * If the hardware/firmware marked hugepage support disabled. |
| */ |
| if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED)) |
| return 0; |
| |
| /* khugepaged doesn't collapse DAX vma, but page fault is fine. */ |
| if (vma_is_dax(vma)) |
| return in_pf ? orders : 0; |
| |
| /* |
| * khugepaged special VMA and hugetlb VMA. |
| * Must be checked after dax since some dax mappings may have |
| * VM_MIXEDMAP set. |
| */ |
| if (!in_pf && !smaps && (vm_flags & VM_NO_KHUGEPAGED)) |
| return 0; |
| |
| /* |
| * Check alignment for file vma and size for both file and anon vma by |
| * filtering out the unsuitable orders. |
| * |
| * Skip the check for page fault. Huge fault does the check in fault |
| * handlers. |
| */ |
| if (!in_pf) { |
| int order = highest_order(orders); |
| unsigned long addr; |
| |
| while (orders) { |
| addr = vma->vm_end - (PAGE_SIZE << order); |
| if (thp_vma_suitable_order(vma, addr, order)) |
| break; |
| order = next_order(&orders, order); |
| } |
| |
| if (!orders) |
| return 0; |
| } |
| |
| /* |
| * Enabled via shmem mount options or sysfs settings. |
| * Must be done before hugepage flags check since shmem has its |
| * own flags. |
| */ |
| if (!in_pf && shmem_file(vma->vm_file)) { |
| bool global_huge = shmem_is_huge(file_inode(vma->vm_file), vma->vm_pgoff, |
| !enforce_sysfs, vma->vm_mm, vm_flags); |
| |
| if (!vma_is_anon_shmem(vma)) |
| return global_huge ? orders : 0; |
| return shmem_allowable_huge_orders(file_inode(vma->vm_file), |
| vma, vma->vm_pgoff, global_huge); |
| } |
| |
| if (!vma_is_anonymous(vma)) { |
| /* |
| * Enforce sysfs THP requirements as necessary. Anonymous vmas |
| * were already handled in thp_vma_allowable_orders(). |
| */ |
| if (enforce_sysfs && |
| (!hugepage_global_enabled() || (!(vm_flags & VM_HUGEPAGE) && |
| !hugepage_global_always()))) |
| return 0; |
| |
| /* |
| * Trust that ->huge_fault() handlers know what they are doing |
| * in fault path. |
| */ |
| if (((in_pf || smaps)) && vma->vm_ops->huge_fault) |
| return orders; |
| /* Only regular file is valid in collapse path */ |
| if (((!in_pf || smaps)) && file_thp_enabled(vma)) |
| return orders; |
| return 0; |
| } |
| |
| if (vma_is_temporary_stack(vma)) |
| return 0; |
| |
| /* |
| * THPeligible bit of smaps should show 1 for proper VMAs even |
| * though anon_vma is not initialized yet. |
| * |
| * Allow page fault since anon_vma may be not initialized until |
| * the first page fault. |
| */ |
| if (!vma->anon_vma) |
| return (smaps || in_pf) ? orders : 0; |
| |
| return orders; |
| } |
| |
| static bool get_huge_zero_page(void) |
| { |
| struct folio *zero_folio; |
| retry: |
| if (likely(atomic_inc_not_zero(&huge_zero_refcount))) |
| return true; |
| |
| zero_folio = folio_alloc((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, |
| HPAGE_PMD_ORDER); |
| if (!zero_folio) { |
| count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); |
| return false; |
| } |
| preempt_disable(); |
| if (cmpxchg(&huge_zero_folio, NULL, zero_folio)) { |
| preempt_enable(); |
| folio_put(zero_folio); |
| goto retry; |
| } |
| WRITE_ONCE(huge_zero_pfn, folio_pfn(zero_folio)); |
| |
| /* We take additional reference here. It will be put back by shrinker */ |
| atomic_set(&huge_zero_refcount, 2); |
| preempt_enable(); |
| count_vm_event(THP_ZERO_PAGE_ALLOC); |
| return true; |
| } |
| |
| 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 folio *mm_get_huge_zero_folio(struct mm_struct *mm) |
| { |
| if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) |
| return READ_ONCE(huge_zero_folio); |
| |
| 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_folio); |
| } |
| |
| void mm_put_huge_zero_folio(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 folio *zero_folio = xchg(&huge_zero_folio, NULL); |
| BUG_ON(zero_folio == NULL); |
| WRITE_ONCE(huge_zero_pfn, ~0UL); |
| folio_put(zero_folio); |
| return HPAGE_PMD_NR; |
| } |
| |
| return 0; |
| } |
| |
| static struct shrinker *huge_zero_page_shrinker; |
| |
| #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_RW(enabled); |
| |
| 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_RW(defrag); |
| |
| 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_RW(use_zero_page); |
| |
| 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 void hugepage_exit_sysfs(struct kobject *hugepage_kobj); |
| static void thpsize_release(struct kobject *kobj); |
| static DEFINE_SPINLOCK(huge_anon_orders_lock); |
| static LIST_HEAD(thpsize_list); |
| |
| static ssize_t thpsize_enabled_show(struct kobject *kobj, |
| struct kobj_attribute *attr, char *buf) |
| { |
| int order = to_thpsize(kobj)->order; |
| const char *output; |
| |
| if (test_bit(order, &huge_anon_orders_always)) |
| output = "[always] inherit madvise never"; |
| else if (test_bit(order, &huge_anon_orders_inherit)) |
| output = "always [inherit] madvise never"; |
| else if (test_bit(order, &huge_anon_orders_madvise)) |
| output = "always inherit [madvise] never"; |
| else |
| output = "always inherit madvise [never]"; |
| |
| return sysfs_emit(buf, "%s\n", output); |
| } |
| |
| static ssize_t thpsize_enabled_store(struct kobject *kobj, |
| struct kobj_attribute *attr, |
| const char *buf, size_t count) |
| { |
| int order = to_thpsize(kobj)->order; |
| ssize_t ret = count; |
| |
| if (sysfs_streq(buf, "always")) { |
| spin_lock(&huge_anon_orders_lock); |
| clear_bit(order, &huge_anon_orders_inherit); |
| clear_bit(order, &huge_anon_orders_madvise); |
| set_bit(order, &huge_anon_orders_always); |
| spin_unlock(&huge_anon_orders_lock); |
| } else if (sysfs_streq(buf, "inherit")) { |
| spin_lock(&huge_anon_orders_lock); |
| clear_bit(order, &huge_anon_orders_always); |
| clear_bit(order, &huge_anon_orders_madvise); |
| set_bit(order, &huge_anon_orders_inherit); |
| spin_unlock(&huge_anon_orders_lock); |
| } else if (sysfs_streq(buf, "madvise")) { |
| spin_lock(&huge_anon_orders_lock); |
| clear_bit(order, &huge_anon_orders_always); |
| clear_bit(order, &huge_anon_orders_inherit); |
| set_bit(order, &huge_anon_orders_madvise); |
| spin_unlock(&huge_anon_orders_lock); |
| } else if (sysfs_streq(buf, "never")) { |
| spin_lock(&huge_anon_orders_lock); |
| clear_bit(order, &huge_anon_orders_always); |
| clear_bit(order, &huge_anon_orders_inherit); |
| clear_bit(order, &huge_anon_orders_madvise); |
| spin_unlock(&huge_anon_orders_lock); |
| } else |
| ret = -EINVAL; |
| |
| if (ret > 0) { |
| int err; |
| |
| err = start_stop_khugepaged(); |
| if (err) |
| ret = err; |
| } |
| return ret; |
| } |
| |
| static struct kobj_attribute thpsize_enabled_attr = |
| __ATTR(enabled, 0644, thpsize_enabled_show, thpsize_enabled_store); |
| |
| static struct attribute *thpsize_attrs[] = { |
| &thpsize_enabled_attr.attr, |
| #ifdef CONFIG_SHMEM |
| &thpsize_shmem_enabled_attr.attr, |
| #endif |
| NULL, |
| }; |
| |
| static const struct attribute_group thpsize_attr_group = { |
| .attrs = thpsize_attrs, |
| }; |
| |
| static const struct kobj_type thpsize_ktype = { |
| .release = &thpsize_release, |
| .sysfs_ops = &kobj_sysfs_ops, |
| }; |
| |
| DEFINE_PER_CPU(struct mthp_stat, mthp_stats) = {{{0}}}; |
| |
| static unsigned long sum_mthp_stat(int order, enum mthp_stat_item item) |
| { |
| unsigned long sum = 0; |
| int cpu; |
| |
| for_each_possible_cpu(cpu) { |
| struct mthp_stat *this = &per_cpu(mthp_stats, cpu); |
| |
| sum += this->stats[order][item]; |
| } |
| |
| return sum; |
| } |
| |
| #define DEFINE_MTHP_STAT_ATTR(_name, _index) \ |
| static ssize_t _name##_show(struct kobject *kobj, \ |
| struct kobj_attribute *attr, char *buf) \ |
| { \ |
| int order = to_thpsize(kobj)->order; \ |
| \ |
| return sysfs_emit(buf, "%lu\n", sum_mthp_stat(order, _index)); \ |
| } \ |
| static struct kobj_attribute _name##_attr = __ATTR_RO(_name) |
| |
| DEFINE_MTHP_STAT_ATTR(anon_fault_alloc, MTHP_STAT_ANON_FAULT_ALLOC); |
| DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK); |
| DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE); |
| DEFINE_MTHP_STAT_ATTR(swpout, MTHP_STAT_SWPOUT); |
| DEFINE_MTHP_STAT_ATTR(swpout_fallback, MTHP_STAT_SWPOUT_FALLBACK); |
| DEFINE_MTHP_STAT_ATTR(shmem_alloc, MTHP_STAT_SHMEM_ALLOC); |
| DEFINE_MTHP_STAT_ATTR(shmem_fallback, MTHP_STAT_SHMEM_FALLBACK); |
| DEFINE_MTHP_STAT_ATTR(shmem_fallback_charge, MTHP_STAT_SHMEM_FALLBACK_CHARGE); |
| DEFINE_MTHP_STAT_ATTR(split, MTHP_STAT_SPLIT); |
| DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED); |
| DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED); |
| |
| static struct attribute *stats_attrs[] = { |
| &anon_fault_alloc_attr.attr, |
| &anon_fault_fallback_attr.attr, |
| &anon_fault_fallback_charge_attr.attr, |
| &swpout_attr.attr, |
| &swpout_fallback_attr.attr, |
| &shmem_alloc_attr.attr, |
| &shmem_fallback_attr.attr, |
| &shmem_fallback_charge_attr.attr, |
| &split_attr.attr, |
| &split_failed_attr.attr, |
| &split_deferred_attr.attr, |
| NULL, |
| }; |
| |
| static struct attribute_group stats_attr_group = { |
| .name = "stats", |
| .attrs = stats_attrs, |
| }; |
| |
| static struct thpsize *thpsize_create(int order, struct kobject *parent) |
| { |
| unsigned long size = (PAGE_SIZE << order) / SZ_1K; |
| struct thpsize *thpsize; |
| int ret; |
| |
| thpsize = kzalloc(sizeof(*thpsize), GFP_KERNEL); |
| if (!thpsize) |
| return ERR_PTR(-ENOMEM); |
| |
| ret = kobject_init_and_add(&thpsize->kobj, &thpsize_ktype, parent, |
| "hugepages-%lukB", size); |
| if (ret) { |
| kfree(thpsize); |
| return ERR_PTR(ret); |
| } |
| |
| ret = sysfs_create_group(&thpsize->kobj, &thpsize_attr_group); |
| if (ret) { |
| kobject_put(&thpsize->kobj); |
| return ERR_PTR(ret); |
| } |
| |
| ret = sysfs_create_group(&thpsize->kobj, &stats_attr_group); |
| if (ret) { |
| kobject_put(&thpsize->kobj); |
| return ERR_PTR(ret); |
| } |
| |
| thpsize->order = order; |
| return thpsize; |
| } |
| |
| static void thpsize_release(struct kobject *kobj) |
| { |
| kfree(to_thpsize(kobj)); |
| } |
| |
| static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) |
| { |
| int err; |
| struct thpsize *thpsize; |
| unsigned long orders; |
| int order; |
| |
| /* |
| * Default to setting PMD-sized THP to inherit the global setting and |
| * disable all other sizes. powerpc's PMD_ORDER isn't a compile-time |
| * constant so we have to do this here. |
| */ |
| huge_anon_orders_inherit = BIT(PMD_ORDER); |
| |
| *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; |
| } |
| |
| orders = THP_ORDERS_ALL_ANON; |
| order = highest_order(orders); |
| while (orders) { |
| thpsize = thpsize_create(order, *hugepage_kobj); |
| if (IS_ERR(thpsize)) { |
| pr_err("failed to create thpsize for order %d\n", order); |
| err = PTR_ERR(thpsize); |
| goto remove_all; |
| } |
| list_add(&thpsize->node, &thpsize_list); |
| order = next_order(&orders, order); |
| } |
| |
| return 0; |
| |
| remove_all: |
| hugepage_exit_sysfs(*hugepage_kobj); |
| return err; |
| 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) |
| { |
| struct thpsize *thpsize, *tmp; |
| |
| list_for_each_entry_safe(thpsize, tmp, &thpsize_list, node) { |
| list_del(&thpsize->node); |
| kobject_put(&thpsize->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 thp_shrinker_init(void) |
| { |
| huge_zero_page_shrinker = shrinker_alloc(0, "thp-zero"); |
| if (!huge_zero_page_shrinker) |
| return -ENOMEM; |
| |
| deferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE | |
| SHRINKER_MEMCG_AWARE | |
| SHRINKER_NONSLAB, |
| "thp-deferred_split"); |
| if (!deferred_split_shrinker) { |
| shrinker_free(huge_zero_page_shrinker); |
| return -ENOMEM; |
| } |
| |
| huge_zero_page_shrinker->count_objects = shrink_huge_zero_page_count; |
| huge_zero_page_shrinker->scan_objects = shrink_huge_zero_page_scan; |
| shrinker_register(huge_zero_page_shrinker); |
| |
| deferred_split_shrinker->count_objects = deferred_split_count; |
| deferred_split_shrinker->scan_objects = deferred_split_scan; |
| shrinker_register(deferred_split_shrinker); |
| |
| return 0; |
| } |
| |
| static void __init thp_shrinker_exit(void) |
| { |
| shrinker_free(huge_zero_page_shrinker); |
| shrinker_free(deferred_split_shrinker); |
| } |
| |
| static int __init hugepage_init(void) |
| { |
| int err; |
| struct kobject *hugepage_kobj; |
| |
| if (!has_transparent_hugepage()) { |
| transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED; |
| return -EINVAL; |
| } |
| |
| /* |
| * hugepages can't be allocated by the buddy allocator |
| */ |
| MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER > MAX_PAGE_ORDER); |
| |
| err = hugepage_init_sysfs(&hugepage_kobj); |
| if (err) |
| goto err_sysfs; |
| |
| err = khugepaged_init(); |
| if (err) |
| goto err_slab; |
| |
| err = thp_shrinker_init(); |
| if (err) |
| goto err_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: |
| thp_shrinker_exit(); |
| err_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, vma); |
| return pmd; |
| } |
| |
| #ifdef CONFIG_MEMCG |
| static inline |
| struct deferred_split *get_deferred_split_queue(struct folio *folio) |
| { |
| struct mem_cgroup *memcg = folio_memcg(folio); |
| struct pglist_data *pgdat = NODE_DATA(folio_nid(folio)); |
| |
| if (memcg) |
| return &memcg->deferred_split_queue; |
| else |
| return &pgdat->deferred_split_queue; |
| } |
| #else |
| static inline |
| struct deferred_split *get_deferred_split_queue(struct folio *folio) |
| { |
| struct pglist_data *pgdat = NODE_DATA(folio_nid(folio)); |
| |
| return &pgdat->deferred_split_queue; |
| } |
| #endif |
| |
| static inline bool is_transparent_hugepage(const struct folio *folio) |
| { |
| if (!folio_test_large(folio)) |
| return false; |
| |
| return is_huge_zero_folio(folio) || |
| folio_test_large_rmappable(folio); |
| } |
| |
| 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, |
| vm_flags_t vm_flags) |
| { |
| loff_t off_end = off + len; |
| loff_t off_align = round_up(off, size); |
| unsigned long len_pad, ret, off_sub; |
| |
| if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) |
| return 0; |
| |
| 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 = mm_get_unmapped_area_vmflags(current->mm, filp, addr, len_pad, |
| off >> PAGE_SHIFT, flags, vm_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; |
| |
| off_sub = (off - ret) & (size - 1); |
| |
| if (test_bit(MMF_TOPDOWN, ¤t->mm->flags) && !off_sub) |
| return ret + size; |
| |
| ret += off_sub; |
| return ret; |
| } |
| |
| unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long addr, |
| unsigned long len, unsigned long pgoff, unsigned long flags, |
| vm_flags_t vm_flags) |
| { |
| unsigned long ret; |
| loff_t off = (loff_t)pgoff << PAGE_SHIFT; |
| |
| ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE, vm_flags); |
| if (ret) |
| return ret; |
| |
| return mm_get_unmapped_area_vmflags(current->mm, filp, addr, len, pgoff, flags, |
| vm_flags); |
| } |
| |
| unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, |
| unsigned long len, unsigned long pgoff, unsigned long flags) |
| { |
| return thp_get_unmapped_area_vmflags(filp, addr, len, pgoff, flags, 0); |
| } |
| 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; |
| struct folio *folio = page_folio(page); |
| pgtable_t pgtable; |
| unsigned long haddr = vmf->address & HPAGE_PMD_MASK; |
| vm_fault_t ret = 0; |
| |
| VM_BUG_ON_FOLIO(!folio_test_large(folio), folio); |
| |
| if (mem_cgroup_charge(folio, vma->vm_mm, gfp)) { |
| folio_put(folio); |
| count_vm_event(THP_FAULT_FALLBACK); |
| count_vm_event(THP_FAULT_FALLBACK_CHARGE); |
| count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_FALLBACK); |
| count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE); |
| return VM_FAULT_FALLBACK; |
| } |
| folio_throttle_swaprate(folio, gfp); |
| |
| pgtable = pte_alloc_one(vma->vm_mm); |
| if (unlikely(!pgtable)) { |
| ret = VM_FAULT_OOM; |
| goto release; |
| } |
| |
| folio_zero_user(folio, vmf->address); |
| /* |
| * The memory barrier inside __folio_mark_uptodate makes sure that |
| * folio_zero_user writes become visible before the set_pmd_at() |
| * write. |
| */ |
| __folio_mark_uptodate(folio); |
| |
| 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); |
| folio_put(folio); |
| 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); |
| folio_add_new_anon_rmap(folio, vma, haddr, RMAP_EXCLUSIVE); |
| folio_add_lru_vma(folio, 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_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_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); |
| folio_put(folio); |
| 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_folio(pgtable_t pgtable, struct mm_struct *mm, |
| struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, |
| struct folio *zero_folio) |
| { |
| pmd_t entry; |
| if (!pmd_none(*pmd)) |
| return; |
| entry = mk_pmd(&zero_folio->page, vma->vm_page_prot); |
| entry = pmd_mkhuge(entry); |
| 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 folio *folio; |
| unsigned long haddr = vmf->address & HPAGE_PMD_MASK; |
| vm_fault_t ret; |
| |
| if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER)) |
| return VM_FAULT_FALLBACK; |
| ret = vmf_anon_prepare(vmf); |
| if (ret) |
| return ret; |
| khugepaged_enter_vma(vma, vma->vm_flags); |
| |
| if (!(vmf->flags & FAULT_FLAG_WRITE) && |
| !mm_forbids_zeropage(vma->vm_mm) && |
| transparent_hugepage_use_zero_page()) { |
| pgtable_t pgtable; |
| struct folio *zero_folio; |
| vm_fault_t ret; |
| |
| pgtable = pte_alloc_one(vma->vm_mm); |
| if (unlikely(!pgtable)) |
| return VM_FAULT_OOM; |
| zero_folio = mm_get_huge_zero_folio(vma->vm_mm); |
| if (unlikely(!zero_folio)) { |
| 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_folio(pgtable, vma->vm_mm, vma, |
| haddr, vmf->pmd, zero_folio); |
| 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); |
| folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, vma, haddr, true); |
| if (unlikely(!folio)) { |
| count_vm_event(THP_FAULT_FALLBACK); |
| count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_FALLBACK); |
| return VM_FAULT_FALLBACK; |
| } |
| return __do_huge_pmd_anonymous_page(vmf, &folio->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 - insert a pmd size pfn |
| * @vmf: Structure describing the fault |
| * @pfn: pfn to insert |
| * @write: whether it's a write fault |
| * |
| * Insert a pmd size pfn. See vmf_insert_pfn() for additional info. |
| * |
| * Return: vm_fault_t value. |
| */ |
| vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write) |
| { |
| unsigned long addr = vmf->address & PMD_MASK; |
| struct vm_area_struct *vma = vmf->vma; |
| pgprot_t pgprot = vma->vm_page_prot; |
| 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); |
| |
| #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, bool write) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pgprot_t prot = vma->vm_page_prot; |
| 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 - insert a pud size pfn |
| * @vmf: Structure describing the fault |
| * @pfn: pfn to insert |
| * @write: whether it's a write fault |
| * |
| * Insert a pud size pfn. See vmf_insert_pfn() for additional info. |
| * |
| * Return: vm_fault_t value. |
| */ |
| vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write) |
| { |
| unsigned long addr = vmf->address & PUD_MASK; |
| struct vm_area_struct *vma = vmf->vma; |
| pgprot_t pgprot = vma->vm_page_prot; |
| |
| /* |
| * 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, write); |
| return VM_FAULT_NOPAGE; |
| } |
| EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud); |
| #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ |
| |
| void touch_pmd(struct vm_area_struct *vma, unsigned long addr, |
| pmd_t *pmd, bool write) |
| { |
| pmd_t _pmd; |
| |
| _pmd = pmd_mkyoung(*pmd); |
| if (write) |
| _pmd = pmd_mkdirty(_pmd); |
| if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, |
| pmd, _pmd, 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; |
| int ret; |
| |
| assert_spin_locked(pmd_lockptr(mm, pmd)); |
| |
| 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 & FOLL_WRITE); |
| |
| /* |
| * 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); |
| ret = try_grab_folio(page_folio(page), 1, flags); |
| if (ret) |
| page = ERR_PTR(ret); |
| |
| 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 *dst_vma, struct vm_area_struct *src_vma) |
| { |
| spinlock_t *dst_ptl, *src_ptl; |
| struct page *src_page; |
| struct folio *src_folio; |
| pmd_t pmd; |
| pgtable_t pgtable = NULL; |
| int ret = -ENOMEM; |
| |
| /* Skip if can be re-fill on fault */ |
| if (!vma_is_anonymous(dst_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; |
| |
| #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_readable_migration_entry(entry)) { |
| entry = make_readable_migration_entry( |
| swp_offset(entry)); |
| pmd = swp_entry_to_pmd(entry); |
| if (pmd_swp_soft_dirty(*src_pmd)) |
| pmd = pmd_swp_mksoft_dirty(pmd); |
| if (pmd_swp_uffd_wp(*src_pmd)) |
| pmd = pmd_swp_mkuffd_wp(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); |
| if (!userfaultfd_wp(dst_vma)) |
| pmd = pmd_swp_clear_uffd_wp(pmd); |
| 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)) { |
| /* |
| * mm_get_huge_zero_folio() will never allocate a new |
| * folio here, since we already have a zero page to |
| * copy. It just takes a reference. |
| */ |
| mm_get_huge_zero_folio(dst_mm); |
| goto out_zero_page; |
| } |
| |
| src_page = pmd_page(pmd); |
| VM_BUG_ON_PAGE(!PageHead(src_page), src_page); |
| src_folio = page_folio(src_page); |
| |
| folio_get(src_folio); |
| if (unlikely(folio_try_dup_anon_rmap_pmd(src_folio, src_page, src_vma))) { |
| /* Page maybe pinned: split and retry the fault on PTEs. */ |
| folio_put(src_folio); |
| pte_free(dst_mm, pgtable); |
| spin_unlock(src_ptl); |
| spin_unlock(dst_ptl); |
| __split_huge_pmd(src_vma, src_pmd, addr, false, NULL); |
| return -EAGAIN; |
| } |
| add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); |
| out_zero_page: |
| mm_inc_nr_ptes(dst_mm); |
| pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); |
| pmdp_set_wrprotect(src_mm, addr, src_pmd); |
| if (!userfaultfd_wp(dst_vma)) |
| pmd = pmd_clear_uffd_wp(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 |
| void touch_pud(struct vm_area_struct *vma, unsigned long addr, |
| pud_t *pud, bool write) |
| { |
| pud_t _pud; |
| |
| _pud = pud_mkyoung(*pud); |
| if (write) |
| _pud = pud_mkdirty(_pud); |
| if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK, |
| pud, _pud, write)) |
| update_mmu_cache_pud(vma, addr, pud); |
| } |
| |
| 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 */ |
| } |
| |
| /* |
| * TODO: once we support anonymous pages, use |
| * folio_try_dup_anon_rmap_*() and split if duplicating fails. |
| */ |
| 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) |
| { |
| 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; |
| |
| touch_pud(vmf->vma, vmf->address, vmf->pud, write); |
| unlock: |
| spin_unlock(vmf->ptl); |
| } |
| #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ |
| |
| void huge_pmd_set_accessed(struct vm_fault *vmf) |
| { |
| bool write = vmf->flags & FAULT_FLAG_WRITE; |
| |
| vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); |
| if (unlikely(!pmd_same(*vmf->pmd, vmf->orig_pmd))) |
| goto unlock; |
| |
| touch_pmd(vmf->vma, vmf->address, vmf->pmd, write); |
| |
| unlock: |
| spin_unlock(vmf->ptl); |
| } |
| |
| vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf) |
| { |
| const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE; |
| struct vm_area_struct *vma = vmf->vma; |
| struct folio *folio; |
| struct page *page; |
| unsigned long haddr = vmf->address & HPAGE_PMD_MASK; |
| pmd_t orig_pmd = vmf->orig_pmd; |
| |
| 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); |
| folio = page_folio(page); |
| VM_BUG_ON_PAGE(!PageHead(page), page); |
| |
| /* Early check when only holding the PT lock. */ |
| if (PageAnonExclusive(page)) |
| goto reuse; |
| |
| if (!folio_trylock(folio)) { |
| folio_get(folio); |
| spin_unlock(vmf->ptl); |
| folio_lock(folio); |
| spin_lock(vmf->ptl); |
| if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { |
| spin_unlock(vmf->ptl); |
| folio_unlock(folio); |
| folio_put(folio); |
| return 0; |
| } |
| folio_put(folio); |
| } |
| |
| /* Recheck after temporarily dropping the PT lock. */ |
| if (PageAnonExclusive(page)) { |
| folio_unlock(folio); |
| goto reuse; |
| } |
| |
| /* |
| * See do_wp_page(): we can only reuse the folio exclusively if |
| * there are no additional references. Note that we always drain |
| * the LRU cache immediately after adding a THP. |
| */ |
| if (folio_ref_count(folio) > |
| 1 + folio_test_swapcache(folio) * folio_nr_pages(folio)) |
| goto unlock_fallback; |
| if (folio_test_swapcache(folio)) |
| folio_free_swap(folio); |
| if (folio_ref_count(folio) == 1) { |
| pmd_t entry; |
| |
| folio_move_anon_rmap(folio, vma); |
| SetPageAnonExclusive(page); |
| folio_unlock(folio); |
| reuse: |
| if (unlikely(unshare)) { |
| spin_unlock(vmf->ptl); |
| return 0; |
| } |
| 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); |
| spin_unlock(vmf->ptl); |
| return 0; |
| } |
| |
| unlock_fallback: |
| folio_unlock(folio); |
| spin_unlock(vmf->ptl); |
| fallback: |
| __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL); |
| return VM_FAULT_FALLBACK; |
| } |
| |
| static inline bool can_change_pmd_writable(struct vm_area_struct *vma, |
| unsigned long addr, pmd_t pmd) |
| { |
| struct page *page; |
| |
| if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE))) |
| return false; |
| |
| /* Don't touch entries that are not even readable (NUMA hinting). */ |
| if (pmd_protnone(pmd)) |
| return false; |
| |
| /* Do we need write faults for softdirty tracking? */ |
| if (pmd_needs_soft_dirty_wp(vma, pmd)) |
| return false; |
| |
| /* Do we need write faults for uffd-wp tracking? */ |
| if (userfaultfd_huge_pmd_wp(vma, pmd)) |
| return false; |
| |
| if (!(vma->vm_flags & VM_SHARED)) { |
| /* See can_change_pte_writable(). */ |
| page = vm_normal_page_pmd(vma, addr, pmd); |
| return page && PageAnon(page) && PageAnonExclusive(page); |
| } |
| |
| /* See can_change_pte_writable(). */ |
| return pmd_dirty(pmd); |
| } |
| |
| /* NUMA hinting page fault entry point for trans huge pmds */ |
| vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf) |
| { |
| struct vm_area_struct *vma = vmf->vma; |
| pmd_t oldpmd = vmf->orig_pmd; |
| pmd_t pmd; |
| struct folio *folio; |
| unsigned long haddr = vmf->address & HPAGE_PMD_MASK; |
| int nid = NUMA_NO_NODE; |
| int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK); |
| bool writable = false; |
| int flags = 0; |
| |
| vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); |
| if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) { |
| spin_unlock(vmf->ptl); |
| goto out; |
| } |
| |
| pmd = pmd_modify(oldpmd, vma->vm_page_prot); |
| |
| /* |
| * Detect now whether the PMD could be writable; this information |
| * is only valid while holding the PT lock. |
| */ |
| writable = pmd_write(pmd); |
| if (!writable && vma_wants_manual_pte_write_upgrade(vma) && |
| can_change_pmd_writable(vma, vmf->address, pmd)) |
| writable = true; |
| |
| folio = vm_normal_folio_pmd(vma, haddr, pmd); |
| if (!folio) |
| goto out_map; |
| |
| /* See similar comment in do_numa_page for explanation */ |
| if (!writable) |
| flags |= TNF_NO_GROUP; |
| |
| nid = folio_nid(folio); |
| /* |
| * For memory tiering mode, cpupid of slow memory page is used |
| * to record page access time. So use default value. |
| */ |
| if (node_is_toptier(nid)) |
| last_cpupid = folio_last_cpupid(folio); |
| target_nid = numa_migrate_prep(folio, vmf, haddr, nid, &flags); |
| if (target_nid == NUMA_NO_NODE) |
| goto out_map; |
| if (migrate_misplaced_folio_prepare(folio, vma, target_nid)) { |
| flags |= TNF_MIGRATE_FAIL; |
| goto out_map; |
| } |
| /* The folio is isolated and isolation code holds a folio reference. */ |
| spin_unlock(vmf->ptl); |
| writable = false; |
| |
| if (!migrate_misplaced_folio(folio, vma, target_nid)) { |
| flags |= TNF_MIGRATED; |
| nid = target_nid; |
| } else { |
| flags |= TNF_MIGRATE_FAIL; |
| vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); |
| if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) { |
| spin_unlock(vmf->ptl); |
| goto out; |
| } |
| goto out_map; |
| } |
| |
| out: |
| if (nid != NUMA_NO_NODE) |
| task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags); |
| |
| return 0; |
| |
| out_map: |
| /* Restore the PMD */ |
| pmd = pmd_modify(oldpmd, vma->vm_page_prot); |
| pmd = pmd_mkyoung(pmd); |
| if (writable) |
| pmd = pmd_mkwrite(pmd, vma); |
| set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd); |
| update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); |
| spin_unlock(vmf->ptl); |
| goto out; |
| } |
| |
| /* |
| * 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 folio *folio; |
| 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; |
| } |
| |
| folio = pmd_folio(orig_pmd); |
| /* |
| * If other processes are mapping this folio, we couldn't discard |
| * the folio unless they all do MADV_FREE so let's skip the folio. |
| */ |
| if (folio_likely_mapped_shared(folio)) |
| goto out; |
| |
| if (!folio_trylock(folio)) |
| 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) { |
| folio_get(folio); |
| spin_unlock(ptl); |
| split_folio(folio); |
| folio_unlock(folio); |
| folio_put(folio); |
| goto out_unlocked; |
| } |
| |
| if (folio_test_dirty(folio)) |
| folio_clear_dirty(folio); |
| folio_unlock(folio); |
| |
| 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); |
| } |
| |
| folio_mark_lazyfree(folio); |
| 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); |
| arch_check_zapped_pmd(vma, orig_pmd); |
| 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); |
| } else if (is_huge_zero_pmd(orig_pmd)) { |
| zap_deposited_table(tlb->mm, pmd); |
| spin_unlock(ptl); |
| } else { |
| struct folio *folio = NULL; |
| int flush_needed = 1; |
| |
| if (pmd_present(orig_pmd)) { |
| struct page *page = pmd_page(orig_pmd); |
| |
| folio = page_folio(page); |
| folio_remove_rmap_pmd(folio, page, vma); |
| WARN_ON_ONCE(folio_mapcount(folio) < 0); |
| 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); |
| folio = pfn_swap_entry_folio(entry); |
| flush_needed = 0; |
| } else |
| WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!"); |
| |
| if (folio_test_anon(folio)) { |
| 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(folio), |
| -HPAGE_PMD_NR); |
| } |
| |
| spin_unlock(ptl); |
| if (flush_needed) |
| tlb_remove_page_size(tlb, &folio->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 released it; but move_page_tables() might have already |
| * inserted a page table, if racing against shmem/file collapse. |
| */ |
| if (!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_pmd_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 unchanged and TLB flush unnecessary |
| * or if prot_numa but THP migration is not supported |
| * - HPAGE_PMD_NR if protections changed and TLB flush necessary |
| */ |
| int change_huge_pmd(struct mmu_gather *tlb, 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 oldpmd, entry; |
| 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; |
| int ret = 1; |
| |
| tlb_change_page_size(tlb, HPAGE_PMD_SIZE); |
| |
| if (prot_numa && !thp_migration_supported()) |
| return 1; |
| |
| ptl = __pmd_trans_huge_lock(pmd, vma); |
| if (!ptl) |
| return 0; |
| |
| #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION |
| if (is_swap_pmd(*pmd)) { |
| swp_entry_t entry = pmd_to_swp_entry(*pmd); |
| struct folio *folio = pfn_swap_entry_folio(entry); |
| pmd_t newpmd; |
| |
| VM_BUG_ON(!is_pmd_migration_entry(*pmd)); |
| if (is_writable_migration_entry(entry)) { |
| /* |
| * A protection check is difficult so |
| * just be safe and disable write |
| */ |
| if (folio_test_anon(folio)) |
| entry = make_readable_exclusive_migration_entry(swp_offset(entry)); |
| else |
| entry = make_readable_migration_entry(swp_offset(entry)); |
| newpmd = swp_entry_to_pmd(entry); |
| if (pmd_swp_soft_dirty(*pmd)) |
| newpmd = pmd_swp_mksoft_dirty(newpmd); |
| } else { |
| newpmd = *pmd; |
| } |
| |
| if (uffd_wp) |
| newpmd = pmd_swp_mkuffd_wp(newpmd); |
| else if (uffd_wp_resolve) |
| newpmd = pmd_swp_clear_uffd_wp(newpmd); |
| if (!pmd_same(*pmd, newpmd)) |
| set_pmd_at(mm, addr, pmd, newpmd); |
| goto unlock; |
| } |
| #endif |
| |
| if (prot_numa) { |
| struct folio *folio; |
| bool toptier; |
| /* |
| * 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 (is_huge_zero_pmd(*pmd)) |
| goto unlock; |
| |
| if (pmd_protnone(*pmd)) |
| goto unlock; |
| |
| folio = pmd_folio(*pmd); |
| toptier = node_is_toptier(folio_nid(folio)); |
| /* |
| * Skip scanning top tier node if normal numa |
| * balancing is disabled |
| */ |
| if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) && |
| toptier) |
| goto unlock; |
| |
| if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING && |
| !toptier) |
| folio_xchg_access_time(folio, |
| jiffies_to_msecs(jiffies)); |
| } |
| /* |
| * 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_ad() is required to make sure we don't miss |
| * dirty/young flags set by hardware. |
| */ |
| oldpmd = pmdp_invalidate_ad(vma, addr, pmd); |
| |
| entry = pmd_modify(oldpmd, newprot); |
| if (uffd_wp) |
| 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); |
| |
| /* See change_pte_range(). */ |
| if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && !pmd_write(entry) && |
| can_change_pmd_writable(vma, addr, entry)) |
| entry = pmd_mkwrite(entry, vma); |
| |
| ret = HPAGE_PMD_NR; |
| set_pmd_at(mm, addr, pmd, entry); |
| |
| if (huge_pmd_needs_flush(oldpmd, entry)) |
| tlb_flush_pmd_range(tlb, addr, HPAGE_PMD_SIZE); |
| unlock: |
| spin_unlock(ptl); |
| return ret; |
| } |
| |
| #ifdef CONFIG_USERFAULTFD |
| /* |
| * The PT lock for src_pmd and dst_vma/src_vma (for reading) are locked by |
| * the caller, but it must return after releasing the page_table_lock. |
| * Just move the page from src_pmd to dst_pmd if possible. |
| * Return zero if succeeded in moving the page, -EAGAIN if it needs to be |
| * repeated by the caller, or other errors in case of failure. |
| */ |
| int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval, |
| struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma, |
| unsigned long dst_addr, unsigned long src_addr) |
| { |
| pmd_t _dst_pmd, src_pmdval; |
| struct page *src_page; |
| struct folio *src_folio; |
| struct anon_vma *src_anon_vma; |
| spinlock_t *src_ptl, *dst_ptl; |
| pgtable_t src_pgtable; |
| struct mmu_notifier_range range; |
| int err = 0; |
| |
| src_pmdval = *src_pmd; |
| src_ptl = pmd_lockptr(mm, src_pmd); |
| |
| lockdep_assert_held(src_ptl); |
| vma_assert_locked(src_vma); |
| vma_assert_locked(dst_vma); |
| |
| /* Sanity checks before the operation */ |
| if (WARN_ON_ONCE(!pmd_none(dst_pmdval)) || WARN_ON_ONCE(src_addr & ~HPAGE_PMD_MASK) || |
| WARN_ON_ONCE(dst_addr & ~HPAGE_PMD_MASK)) { |
| spin_unlock(src_ptl); |
| return -EINVAL; |
| } |
| |
| if (!pmd_trans_huge(src_pmdval)) { |
| spin_unlock(src_ptl); |
| if (is_pmd_migration_entry(src_pmdval)) { |
| pmd_migration_entry_wait(mm, &src_pmdval); |
| return -EAGAIN; |
| } |
| return -ENOENT; |
| } |
| |
| src_page = pmd_page(src_pmdval); |
| |
| if (!is_huge_zero_pmd(src_pmdval)) { |
| if (unlikely(!PageAnonExclusive(src_page))) { |
| spin_unlock(src_ptl); |
| return -EBUSY; |
| } |
| |
| src_folio = page_folio(src_page); |
| folio_get(src_folio); |
| } else |
| src_folio = NULL; |
| |
| spin_unlock(src_ptl); |
| |
| flush_cache_range(src_vma, src_addr, src_addr + HPAGE_PMD_SIZE); |
| mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, src_addr, |
| src_addr + HPAGE_PMD_SIZE); |
| mmu_notifier_invalidate_range_start(&range); |
| |
| if (src_folio) { |
| folio_lock(src_folio); |
| |
| /* |
| * split_huge_page walks the anon_vma chain without the page |
| * lock. Serialize against it with the anon_vma lock, the page |
| * lock is not enough. |
| */ |
| src_anon_vma = folio_get_anon_vma(src_folio); |
| if (!src_anon_vma) { |
| err = -EAGAIN; |
| goto unlock_folio; |
| } |
| anon_vma_lock_write(src_anon_vma); |
| } else |
| src_anon_vma = NULL; |
| |
| dst_ptl = pmd_lockptr(mm, dst_pmd); |
| double_pt_lock(src_ptl, dst_ptl); |
| if (unlikely(!pmd_same(*src_pmd, src_pmdval) || |
| !pmd_same(*dst_pmd, dst_pmdval))) { |
| err = -EAGAIN; |
| goto unlock_ptls; |
| } |
| if (src_folio) { |
| if (folio_maybe_dma_pinned(src_folio) || |
| !PageAnonExclusive(&src_folio->page)) { |
| err = -EBUSY; |
| goto unlock_ptls; |
| } |
| |
| if (WARN_ON_ONCE(!folio_test_head(src_folio)) || |
| WARN_ON_ONCE(!folio_test_anon(src_folio))) { |
| err = -EBUSY; |
| goto unlock_ptls; |
| } |
| |
| src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd); |
| /* Folio got pinned from under us. Put it back and fail the move. */ |
| if (folio_maybe_dma_pinned(src_folio)) { |
| set_pmd_at(mm, src_addr, src_pmd, src_pmdval); |
| err = -EBUSY; |
| goto unlock_ptls; |
| } |
| |
| folio_move_anon_rmap(src_folio, dst_vma); |
| src_folio->index = linear_page_index(dst_vma, dst_addr); |
| |
| _dst_pmd = mk_huge_pmd(&src_folio->page, dst_vma->vm_page_prot); |
| /* Follow mremap() behavior and treat the entry dirty after the move */ |
| _dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma); |
| } else { |
| src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd); |
| _dst_pmd = mk_huge_pmd(src_page, dst_vma->vm_page_prot); |
| } |
| set_pmd_at(mm, dst_addr, dst_pmd, _dst_pmd); |
| |
| src_pgtable = pgtable_trans_huge_withdraw(mm, src_pmd); |
| pgtable_trans_huge_deposit(mm, dst_pmd, src_pgtable); |
| unlock_ptls: |
| double_pt_unlock(src_ptl, dst_ptl); |
| if (src_anon_vma) { |
| anon_vma_unlock_write(src_anon_vma); |
| put_anon_vma(src_anon_vma); |
| } |
| unlock_folio: |
| /* unblock rmap walks */ |
| if (src_folio) |
| folio_unlock(src_folio); |
| mmu_notifier_invalidate_range_end(&range); |
| if (src_folio) |
| folio_put(src_folio); |
| return err; |
| } |
| #endif /* CONFIG_USERFAULTFD */ |
| |
| /* |
| * 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 page table lock pointer if a given pud 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 *__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; |
| |
| pudp_huge_get_and_clear_full(vma, 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(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->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); |
| mmu_notifier_invalidate_range_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, old_pmd; |
| unsigned long addr; |
| pte_t *pte; |
| 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/mm/mmu_notifier.rst |
| */ |
| old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd); |
| |
| pgtable = pgtable_trans_huge_withdraw(mm, pmd); |
| pmd_populate(mm, &_pmd, pgtable); |
| |
| pte = pte_offset_map(&_pmd, haddr); |
| VM_BUG_ON(!pte); |
| for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { |
| pte_t entry; |
| |
| entry = pfn_pte(my_zero_pfn(addr), vma->vm_page_prot); |
| entry = pte_mkspecial(entry); |
| if (pmd_uffd_wp(old_pmd)) |
| entry = pte_mkuffd_wp(entry); |
| VM_BUG_ON(!pte_none(ptep_get(pte))); |
| set_pte_at(mm, addr, pte, entry); |
| pte++; |
| } |
| pte_unmap(pte - 1); |
| 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 folio *folio; |
| struct page *page; |
| pgtable_t pgtable; |
| pmd_t old_pmd, _pmd; |
| bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; |
| bool anon_exclusive = false, dirty = false; |
| unsigned long addr; |
| pte_t *pte; |
| 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)) { |
| old_pmd = pmdp_huge_clear_flush(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; |
| if (unlikely(is_pmd_migration_entry(old_pmd))) { |
| swp_entry_t entry; |
| |
| entry = pmd_to_swp_entry(old_pmd); |
| folio = pfn_swap_entry_folio(entry); |
| } else { |
| page = pmd_page(old_pmd); |
| folio = page_folio(page); |
| if (!folio_test_dirty(folio) && pmd_dirty(old_pmd)) |
| folio_mark_dirty(folio); |
| if (!folio_test_referenced(folio) && pmd_young(old_pmd)) |
| folio_set_referenced(folio); |
| folio_remove_rmap_pmd(folio, page, vma); |
| folio_put(folio); |
| } |
| add_mm_counter(mm, mm_counter_file(folio), -HPAGE_PMD_NR); |
| return; |
| } |
| |
| if (is_huge_zero_pmd(*pmd)) { |
| /* |
| * FIXME: Do we want to invalidate secondary mmu by calling |
| * mmu_notifier_arch_invalidate_secondary_tlbs() 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); |
| } |
| |
| pmd_migration = is_pmd_migration_entry(*pmd); |
| if (unlikely(pmd_migration)) { |
| swp_entry_t entry; |
| |
| old_pmd = *pmd; |
| entry = pmd_to_swp_entry(old_pmd); |
| page = pfn_swap_entry_to_page(entry); |
| write = is_writable_migration_entry(entry); |
| if (PageAnon(page)) |
| anon_exclusive = is_readable_exclusive_migration_entry(entry); |
| young = is_migration_entry_young(entry); |
| dirty = is_migration_entry_dirty(entry); |
| soft_dirty = pmd_swp_soft_dirty(old_pmd); |
| uffd_wp = pmd_swp_uffd_wp(old_pmd); |
| } else { |
| /* |
| * 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); |
| page = pmd_page(old_pmd); |
| folio = page_folio(page); |
| if (pmd_dirty(old_pmd)) { |
| dirty = true; |
| folio_set_dirty(folio); |
| } |
| 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_WARN_ON_FOLIO(!folio_ref_count(folio), folio); |
| VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); |
| |
| /* |
| * Without "freeze", we'll simply split the PMD, propagating the |
| * PageAnonExclusive() flag for each PTE by setting it for |
| * each subpage -- no need to (temporarily) clear. |
| * |
| * With "freeze" we want to replace mapped pages by |
| * migration entries right away. This is only possible if we |
| * managed to clear PageAnonExclusive() -- see |
| * set_pmd_migration_entry(). |
| * |
| * In case we cannot clear PageAnonExclusive(), split the PMD |
| * only and let try_to_migrate_one() fail later. |
| * |
| * See folio_try_share_anon_rmap_pmd(): invalidate PMD first. |
| */ |
| anon_exclusive = PageAnonExclusive(page); |
| if (freeze && anon_exclusive && |
| folio_try_share_anon_rmap_pmd(folio, page)) |
| freeze = false; |
| if (!freeze) { |
| rmap_t rmap_flags = RMAP_NONE; |
| |
| folio_ref_add(folio, HPAGE_PMD_NR - 1); |
| if (anon_exclusive) |
| rmap_flags |= RMAP_EXCLUSIVE; |
| folio_add_anon_rmap_ptes(folio, page, HPAGE_PMD_NR, |
| vma, haddr, rmap_flags); |
| } |
| } |
| |
| /* |
| * 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); |
| |
| pte = pte_offset_map(&_pmd, haddr); |
| VM_BUG_ON(!pte); |
| |
| /* |
| * Note that NUMA hinting access restrictions are not transferred to |
| * avoid any possibility of altering permissions across VMAs. |
| */ |
| if (freeze || pmd_migration) { |
| for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { |
| pte_t entry; |
| swp_entry_t swp_entry; |
| |
| if (write) |
| swp_entry = make_writable_migration_entry( |
| page_to_pfn(page + i)); |
| else if (anon_exclusive) |
| swp_entry = make_readable_exclusive_migration_entry( |
| page_to_pfn(page + i)); |
| else |
| swp_entry = make_readable_migration_entry( |
| page_to_pfn(page + i)); |
| if (young) |
| swp_entry = make_migration_entry_young(swp_entry); |
| if (dirty) |
| swp_entry = make_migration_entry_dirty(swp_entry); |
| 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); |
| |
| VM_WARN_ON(!pte_none(ptep_get(pte + i))); |
| set_pte_at(mm, addr, pte + i, entry); |
| } |
| } else { |
| pte_t entry; |
| |
| entry = mk_pte(page, READ_ONCE(vma->vm_page_prot)); |
| if (write) |
| entry = pte_mkwrite(entry, vma); |
| if (!young) |
| entry = pte_mkold(entry); |
| /* NOTE: this may set soft-dirty too on some archs */ |
| if (dirty) |
| entry = pte_mkdirty(entry); |
| if (soft_dirty) |
| entry = pte_mksoft_dirty(entry); |
| if (uffd_wp) |
| entry = pte_mkuffd_wp(entry); |
| |
| for (i = 0; i < HPAGE_PMD_NR; i++) |
| VM_WARN_ON(!pte_none(ptep_get(pte + i))); |
| |
| set_ptes(mm, haddr, pte, entry, HPAGE_PMD_NR); |
| } |
| pte_unmap(pte); |
| |
| if (!pmd_migration) |
| folio_remove_rmap_pmd(folio, page, vma); |
| if (freeze) |
| put_page(page); |
| |
| smp_wmb(); /* make pte visible before pmd */ |
| pmd_populate(mm, pmd, pgtable); |
| } |
| |
| void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address, |
| pmd_t *pmd, bool freeze, struct folio *folio) |
| { |
| VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio)); |
| VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE)); |
| VM_WARN_ON_ONCE(folio && !folio_test_locked(folio)); |
| VM_BUG_ON(freeze && !folio); |
| |
| /* |
| * When the caller requests to set up a migration entry, we |
| * require a folio to check the PMD against. Otherwise, there |
| * is a risk of replacing the wrong folio. |
| */ |
| if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || |
| is_pmd_migration_entry(*pmd)) { |
| if (folio && folio != pmd_folio(*pmd)) |
| return; |
| __split_huge_pmd_locked(vma, pmd, address, freeze); |
| } |
| } |
| |
| void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, |
| unsigned long address, bool freeze, struct folio *folio) |
| { |
| spinlock_t *ptl; |
| struct mmu_notifier_range range; |
| |
| mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, 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); |
| split_huge_pmd_locked(vma, range.start, pmd, freeze, folio); |
| spin_unlock(ptl); |
| mmu_notifier_invalidate_range_end(&range); |
| } |
| |
| void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, |
| bool freeze, struct folio *folio) |
| { |
| pmd_t *pmd = mm_find_pmd(vma->vm_mm, address); |
| |
| if (!pmd) |
| return; |
| |
| __split_huge_pmd(vma, pmd, address, freeze, folio); |
| } |
| |
| 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 next vma vm_start, |
| * check if we need to split it. |
| */ |
| if (adjust_next > 0) { |
| struct vm_area_struct *next = find_vma(vma->vm_mm, vma->vm_end); |
| unsigned long nstart = next->vm_start; |
| nstart += adjust_next; |
| split_huge_pmd_if_needed(next, nstart); |
| } |
| } |
| |
| static void unmap_folio(struct folio *folio) |
| { |
| enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SYNC | |
| TTU_BATCH_FLUSH; |
| |
| VM_BUG_ON_FOLIO(!folio_test_large(folio), folio); |
| |
| if (folio_test_pmd_mappable(folio)) |
| ttu_flags |= TTU_SPLIT_HUGE_PMD; |
| |
| /* |
| * Anon pages need migration entries to preserve them, but file |
| * pages can simply be left unmapped, then faulted back on demand. |
| * If that is ever changed (perhaps for mlock), update remap_page(). |
| */ |
| if (folio_test_anon(folio)) |
| try_to_migrate(folio, ttu_flags); |
| else |
| try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK); |
| |
| try_to_unmap_flush(); |
| } |
| |
| static bool __discard_anon_folio_pmd_locked(struct vm_area_struct *vma, |
| unsigned long addr, pmd_t *pmdp, |
| struct folio *folio) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| int ref_count, map_count; |
| pmd_t orig_pmd = *pmdp; |
| |
| if (folio_test_dirty(folio) || pmd_dirty(orig_pmd)) |
| return false; |
| |
| orig_pmd = pmdp_huge_clear_flush(vma, addr, pmdp); |
| |
| /* |
| * Syncing against concurrent GUP-fast: |
| * - clear PMD; barrier; read refcount |
| * - inc refcount; barrier; read PMD |
| */ |
| smp_mb(); |
| |
| ref_count = folio_ref_count(folio); |
| map_count = folio_mapcount(folio); |
| |
| /* |
| * Order reads for folio refcount and dirty flag |
| * (see comments in __remove_mapping()). |
| */ |
| smp_rmb(); |
| |
| /* |
| * If the folio or its PMD is redirtied at this point, or if there |
| * are unexpected references, we will give up to discard this folio |
| * and remap it. |
| * |
| * The only folio refs must be one from isolation plus the rmap(s). |
| */ |
| if (folio_test_dirty(folio) || pmd_dirty(orig_pmd) || |
| ref_count != map_count + 1) { |
| set_pmd_at(mm, addr, pmdp, orig_pmd); |
| return false; |
| } |
| |
| folio_remove_rmap_pmd(folio, pmd_page(orig_pmd), vma); |
| zap_deposited_table(mm, pmdp); |
| add_mm_counter(mm, MM_ANONPAGES, -HPAGE_PMD_NR); |
| if (vma->vm_flags & VM_LOCKED) |
| mlock_drain_local(); |
| folio_put(folio); |
| |
| return true; |
| } |
| |
| bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr, |
| pmd_t *pmdp, struct folio *folio) |
| { |
| VM_WARN_ON_FOLIO(!folio_test_pmd_mappable(folio), folio); |
| VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio); |
| VM_WARN_ON_ONCE(!IS_ALIGNED(addr, HPAGE_PMD_SIZE)); |
| |
| if (folio_test_anon(folio) && !folio_test_swapbacked(folio)) |
| return __discard_anon_folio_pmd_locked(vma, addr, pmdp, folio); |
| |
| return false; |
| } |
| |
| static void remap_page(struct folio *folio, unsigned long nr) |
| { |
| int i = 0; |
| |
| /* If unmap_folio() uses try_to_migrate() on file, remove this check */ |
| if (!folio_test_anon(folio)) |
| return; |
| for (;;) { |
| remove_migration_ptes(folio, folio, true); |
| i += folio_nr_pages(folio); |
| if (i >= nr) |
| break; |
| folio = folio_next(folio); |
| } |
| } |
| |
| 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(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)); |
| if (PageUnevictable(tail)) |
| tail->mlock_count = 0; |
| else |
| list_add_tail(&tail->lru, &head->lru); |
| SetPageLRU(tail); |
| } |
| } |
| |
| static void __split_huge_page_tail(struct folio *folio, int tail, |
| struct lruvec *lruvec, struct list_head *list, |
| unsigned int new_order) |
| { |
| struct page *head = &folio->page; |
| struct page *page_tail = head + tail; |
| /* |
| * Careful: new_folio is not a "real" folio before we cleared PageTail. |
| * Don't pass it around before clear_compound_head(). |
| */ |
| struct folio *new_folio = (struct folio *)page_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. |
| * |
| * Note that for mapped sub-pages of an anonymous THP, |
| * PG_anon_exclusive has been cleared in unmap_folio() and is stored in |
| * the migration entry instead from where remap_page() will restore it. |
| * We can still have PG_anon_exclusive set on effectively unmapped and |
| * unreferenced sub-pages of an anonymous THP: we can simply drop |
| * PG_anon_exclusive (-> PG_mappedtodisk) for these here. |
| */ |
| 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_ARCH_USES_PG_ARCH_X |
| (1L << PG_arch_2) | |
| (1L << PG_arch_3) | |
| #endif |
| (1L << PG_dirty) | |
| LRU_GEN_MASK | LRU_REFS_MASK)); |
| |
| /* ->mapping in first and second tail page is replaced by other uses */ |
| 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->private should not be set in tail pages. Fix up and warn once |
| * if private is unexpectedly set. |
| */ |
| if (unlikely(page_tail->private)) { |
| VM_WARN_ON_ONCE_PAGE(true, page_tail); |
| page_tail->private = 0; |
| } |
| if (folio_test_swapcache(folio)) |
| new_folio->swap.val = folio->swap.val + 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); |
| if (new_order) { |
| prep_compound_page(page_tail, new_order); |
| folio_set_large_rmappable(new_folio); |
| } |
| |
| /* Finally unfreeze refcount. Additional reference from page cache. */ |
| page_ref_unfreeze(page_tail, |
| 1 + ((!folio_test_anon(folio) || folio_test_swapcache(folio)) ? |
| folio_nr_pages(new_folio) : 0)); |
| |
| if (folio_test_young(folio)) |
| folio_set_young(new_folio); |
| if (folio_test_idle(folio)) |
| folio_set_idle(new_folio); |
| |
| folio_xchg_last_cpupid(new_folio, folio_last_cpupid(folio)); |
| |
| /* |
| * 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, unsigned int new_order) |
| { |
| struct folio *folio = page_folio(page); |
| struct page *head = &folio->page; |
| struct lruvec *lruvec; |
| struct address_space *swap_cache = NULL; |
| unsigned long offset = 0; |
| int i, nr_dropped = 0; |
| unsigned int new_nr = 1 << new_order; |
| int order = folio_order(folio); |
| unsigned int nr = 1 << order; |
| |
| /* complete memcg works before add pages to LRU */ |
| split_page_memcg(head, order, new_order); |
| |
| if (folio_test_anon(folio) && folio_test_swapcache(folio)) { |
| offset = swap_cache_index(folio->swap); |
| swap_cache = swap_address_space(folio->swap); |
| xa_lock(&swap_cache->i_pages); |
| } |
| |
| /* lock lru list/PageCompound, ref frozen by page_ref_freeze */ |
| lruvec = folio_lruvec_lock(folio); |
| |
| ClearPageHasHWPoisoned(head); |
| |
| for (i = nr - new_nr; i >= new_nr; i -= new_nr) { |
| __split_huge_page_tail(folio, i, lruvec, list, new_order); |
| /* Some pages can be beyond EOF: drop them from page cache */ |
| if (head[i].index >= end) { |
| struct folio *tail = page_folio(head + i); |
| |
| if (shmem_mapping(folio->mapping)) |
| nr_dropped++; |
| else if (folio_test_clear_dirty(tail)) |
| folio_account_cleaned(tail, |
| inode_to_wb(folio->mapping->host)); |
| __filemap_remove_folio(tail, NULL); |
| folio_put(tail); |
| } else if (!PageAnon(page)) { |
| __xa_store(&folio->mapping->i_pages, head[i].index, |
| head + i, 0); |
| } else if (swap_cache) { |
| __xa_store(&swap_cache->i_pages, offset + i, |
| head + i, 0); |
| } |
| } |
| |
| if (!new_order) |
| ClearPageCompound(head); |
| else { |
| struct folio *new_folio = (struct folio *)head; |
| |
| folio_set_order(new_folio, new_order); |
| } |
| unlock_page_lruvec(lruvec); |
| /* Caller disabled irqs, so they are still disabled here */ |
| |
| split_page_owner(head, order, new_order); |
| pgalloc_tag_split(head, 1 << order); |
| |
| /* See comment in __split_huge_page_tail() */ |
| if (folio_test_anon(folio)) { |
| /* Additional pin to swap cache */ |
| if (folio_test_swapcache(folio)) { |
| folio_ref_add(folio, 1 + new_nr); |
| xa_unlock(&swap_cache->i_pages); |
| } else { |
| folio_ref_inc(folio); |
| } |
| } else { |
| /* Additional pin to page cache */ |
| folio_ref_add(folio, 1 + new_nr); |
| xa_unlock(&folio->mapping->i_pages); |
| } |
| local_irq_enable(); |
| |
| if (nr_dropped) |
| shmem_uncharge(folio->mapping->host, nr_dropped); |
| remap_page(folio, nr); |
| |
| /* |
| * set page to its compound_head when split to non order-0 pages, so |
| * we can skip unlocking it below, since PG_locked is transferred to |
| * the compound_head of the page and the caller will unlock it. |
| */ |
| if (new_order) |
| page = compound_head(page); |
| |
| for (i = 0; i < nr; i += new_nr) { |
| struct page *subpage = head + i; |
| struct folio *new_folio = page_folio(subpage); |
| if (subpage == page) |
| continue; |
| folio_unlock(new_folio); |
| |
| /* |
| * 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. |
| */ |
| free_page_and_swap_cache(subpage); |
| } |
| } |
| |
| /* Racy check whether the huge page can be split */ |
| bool can_split_folio(struct folio *folio, int *pextra_pins) |
| { |
| int extra_pins; |
| |
| /* Additional pins from page cache */ |
| if (folio_test_anon(folio)) |
| extra_pins = folio_test_swapcache(folio) ? |
| folio_nr_pages(folio) : 0; |
| else |
| extra_pins = folio_nr_pages(folio); |
| if (pextra_pins) |
| *pextra_pins = extra_pins; |
| return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins - 1; |
| } |
| |
| /* |
| * This function splits a large folio into smaller folios of order @new_order. |
| * @page can point to any page of the large folio to split. The split operation |
| * does not change the position of @page. |
| * |
| * Prerequisites: |
| * |
| * 1) The caller must hold a reference on the @page's owning folio, also known |
| * as the large folio. |
| * |
| * 2) The large folio must be locked. |
| * |
| * 3) The folio must not be pinned. Any unexpected folio references, including |
| * GUP pins, will result in the folio not getting split; instead, the caller |
| * will receive an -EAGAIN. |
| * |
| * 4) @new_order > 1, usually. Splitting to order-1 anonymous folios is not |
| * supported for non-file-backed folios, because folio->_deferred_list, which |
| * is used by partially mapped folios, is stored in subpage 2, but an order-1 |
| * folio only has subpages 0 and 1. File-backed order-1 folios are supported, |
| * since they do not use _deferred_list. |
| * |
| * After splitting, the caller's folio reference will be transferred to @page, |
| * resulting in a raised refcount of @page after this call. The other pages may |
| * be freed if they are not mapped. |
| * |
| * If @list is null, tail pages will be added to LRU list, otherwise, to @list. |
| * |
| * Pages in @new_order will inherit the mapping, flags, and so on from the |
| * huge page. |
| * |
| * Returns 0 if the huge page was split successfully. |
| * |
| * Returns -EAGAIN if the folio has unexpected reference (e.g., GUP) or if |
| * the folio was concurrently removed from the page cache. |
| * |
|