diff options
Diffstat (limited to 'mm/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 3015 |
1 files changed, 3015 insertions, 0 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c new file mode 100644 index 000000000..e4c690c21 --- /dev/null +++ b/mm/huge_memory.c @@ -0,0 +1,3015 @@ +// 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/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/dax.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 <asm/tlb.h> +#include <asm/pgalloc.h> +#include "internal.h" + +/* + * By default, transparent hugepage support is disabled in order to avoid + * risking an increased memory footprint for applications that are not + * guaranteed to benefit from it. When transparent hugepage support is + * enabled, it is for all mappings, and khugepaged scans all mappings. + * Defrag is invoked by khugepaged hugepage allocations and by page faults + * for all hugepage allocations. + */ +unsigned long transparent_hugepage_flags __read_mostly = +#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS + (1<<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 atomic_t huge_zero_refcount; +struct page *huge_zero_page __read_mostly; +unsigned long huge_zero_pfn __read_mostly = ~0UL; + +static inline bool file_thp_enabled(struct vm_area_struct *vma) +{ + return transhuge_vma_enabled(vma, vma->vm_flags) && vma->vm_file && + !inode_is_open_for_write(vma->vm_file->f_inode) && + (vma->vm_flags & VM_EXEC); +} + +bool transparent_hugepage_active(struct vm_area_struct *vma) +{ + /* The addr is used to check if the vma size fits */ + unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE; + + if (!transhuge_vma_suitable(vma, addr)) + return false; + if (vma_is_anonymous(vma)) + return __transparent_hugepage_enabled(vma); + if (vma_is_shmem(vma)) + return shmem_huge_enabled(vma); + if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS)) + return file_thp_enabled(vma); + + return false; +} + +static struct page *get_huge_zero_page(void) +{ + struct page *zero_page; +retry: + if (likely(atomic_inc_not_zero(&huge_zero_refcount))) + return READ_ONCE(huge_zero_page); + + zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, + HPAGE_PMD_ORDER); + if (!zero_page) { + count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); + return NULL; + } + count_vm_event(THP_ZERO_PAGE_ALLOC); + preempt_disable(); + if (cmpxchg(&huge_zero_page, NULL, zero_page)) { + preempt_enable(); + __free_pages(zero_page, compound_order(zero_page)); + goto retry; + } + WRITE_ONCE(huge_zero_pfn, page_to_pfn(zero_page)); + + /* We take additional reference here. It will be put back by shrinker */ + atomic_set(&huge_zero_refcount, 2); + preempt_enable(); + return READ_ONCE(huge_zero_page); +} + +static void put_huge_zero_page(void) +{ + /* + * Counter should never go to zero here. Only shrinker can put + * last reference. + */ + BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); +} + +struct page *mm_get_huge_zero_page(struct mm_struct *mm) +{ + if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) + return READ_ONCE(huge_zero_page); + + if (!get_huge_zero_page()) + return NULL; + + if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) + put_huge_zero_page(); + + return READ_ONCE(huge_zero_page); +} + +void mm_put_huge_zero_page(struct mm_struct *mm) +{ + if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) + put_huge_zero_page(); +} + +static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, + struct shrink_control *sc) +{ + /* we can free zero page only if last reference remains */ + return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; +} + +static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, + struct shrink_control *sc) +{ + if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { + struct page *zero_page = xchg(&huge_zero_page, NULL); + BUG_ON(zero_page == NULL); + WRITE_ONCE(huge_zero_pfn, ~0UL); + __free_pages(zero_page, compound_order(zero_page)); + return HPAGE_PMD_NR; + } + + return 0; +} + +static struct shrinker huge_zero_page_shrinker = { + .count_objects = shrink_huge_zero_page_count, + .scan_objects = shrink_huge_zero_page_scan, + .seeks = DEFAULT_SEEKS, +}; + +#ifdef CONFIG_SYSFS +static ssize_t enabled_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "[always] madvise never\n"); + else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "always [madvise] never\n"); + else + return sprintf(buf, "always madvise [never]\n"); +} + +static ssize_t enabled_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + ssize_t ret = count; + + if (sysfs_streq(buf, "always")) { + clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); + set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); + } else if (sysfs_streq(buf, "madvise")) { + clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); + set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); + } else if (sysfs_streq(buf, "never")) { + clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); + } else + ret = -EINVAL; + + if (ret > 0) { + int err = start_stop_khugepaged(); + if (err) + ret = err; + } + return ret; +} +static struct kobj_attribute enabled_attr = + __ATTR(enabled, 0644, enabled_show, enabled_store); + +ssize_t single_hugepage_flag_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf, + enum transparent_hugepage_flag flag) +{ + return sprintf(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) +{ + if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "[always] defer defer+madvise madvise never\n"); + if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "always [defer] defer+madvise madvise never\n"); + if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "always defer [defer+madvise] madvise never\n"); + if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "always defer defer+madvise [madvise] never\n"); + return sprintf(buf, "always defer defer+madvise madvise [never]\n"); +} + +static ssize_t defrag_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + if (sysfs_streq(buf, "always")) { + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); + set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); + } else if (sysfs_streq(buf, "defer+madvise")) { + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); + set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); + } else if (sysfs_streq(buf, "defer")) { + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); + set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); + } else if (sysfs_streq(buf, "madvise")) { + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); + set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); + } else if (sysfs_streq(buf, "never")) { + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags); + } else + return -EINVAL; + + return count; +} +static struct kobj_attribute defrag_attr = + __ATTR(defrag, 0644, defrag_show, defrag_store); + +static ssize_t use_zero_page_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return single_hugepage_flag_show(kobj, attr, buf, + TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); +} +static ssize_t use_zero_page_store(struct kobject *kobj, + struct kobj_attribute *attr, const char *buf, size_t count) +{ + return single_hugepage_flag_store(kobj, attr, buf, count, + TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); +} +static struct kobj_attribute use_zero_page_attr = + __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); + +static ssize_t hpage_pmd_size_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE); +} +static struct kobj_attribute hpage_pmd_size_attr = + __ATTR_RO(hpage_pmd_size); + +static struct attribute *hugepage_attr[] = { + &enabled_attr.attr, + &defrag_attr.attr, + &use_zero_page_attr.attr, + &hpage_pmd_size_attr.attr, +#ifdef CONFIG_SHMEM + &shmem_enabled_attr.attr, +#endif + NULL, +}; + +static const struct attribute_group hugepage_attr_group = { + .attrs = hugepage_attr, +}; + +static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) +{ + int err; + + *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); + if (unlikely(!*hugepage_kobj)) { + pr_err("failed to create transparent hugepage kobject\n"); + return -ENOMEM; + } + + err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); + if (err) { + pr_err("failed to register transparent hugepage group\n"); + goto delete_obj; + } + + err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); + if (err) { + pr_err("failed to register transparent hugepage group\n"); + goto remove_hp_group; + } + + return 0; + +remove_hp_group: + sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); +delete_obj: + kobject_put(*hugepage_kobj); + return err; +} + +static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) +{ + sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); + sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); + kobject_put(hugepage_kobj); +} +#else +static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) +{ + return 0; +} + +static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) +{ +} +#endif /* CONFIG_SYSFS */ + +static int __init hugepage_init(void) +{ + int err; + struct kobject *hugepage_kobj; + + if (!has_transparent_hugepage()) { + /* + * Hardware doesn't support hugepages, hence disable + * DAX PMD support. + */ + transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_NEVER_DAX; + return -EINVAL; + } + + /* + * hugepages can't be allocated by the buddy allocator + */ + MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); + /* + * we use page->mapping and page->index in second tail page + * as list_head: assuming THP order >= 2 + */ + MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); + + err = hugepage_init_sysfs(&hugepage_kobj); + if (err) + goto err_sysfs; + + err = khugepaged_init(); + if (err) + goto err_slab; + + err = register_shrinker(&huge_zero_page_shrinker); + if (err) + goto err_hzp_shrinker; + err = register_shrinker(&deferred_split_shrinker); + if (err) + goto err_split_shrinker; + + /* + * By default disable transparent hugepages on smaller systems, + * where the extra memory used could hurt more than TLB overhead + * is likely to save. The admin can still enable it through /sys. + */ + if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) { + transparent_hugepage_flags = 0; + return 0; + } + + err = start_stop_khugepaged(); + if (err) + goto err_khugepaged; + + return 0; +err_khugepaged: + unregister_shrinker(&deferred_split_shrinker); +err_split_shrinker: + unregister_shrinker(&huge_zero_page_shrinker); +err_hzp_shrinker: + khugepaged_destroy(); +err_slab: + hugepage_exit_sysfs(hugepage_kobj); +err_sysfs: + return err; +} +subsys_initcall(hugepage_init); + +static int __init setup_transparent_hugepage(char *str) +{ + int ret = 0; + if (!str) + goto out; + if (!strcmp(str, "always")) { + set_bit(TRANSPARENT_HUGEPAGE_FLAG, + &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, + &transparent_hugepage_flags); + ret = 1; + } else if (!strcmp(str, "madvise")) { + clear_bit(TRANSPARENT_HUGEPAGE_FLAG, + &transparent_hugepage_flags); + set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, + &transparent_hugepage_flags); + ret = 1; + } else if (!strcmp(str, "never")) { + clear_bit(TRANSPARENT_HUGEPAGE_FLAG, + &transparent_hugepage_flags); + clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, + &transparent_hugepage_flags); + ret = 1; + } +out: + if (!ret) + pr_warn("transparent_hugepage= cannot parse, ignored\n"); + return ret; +} +__setup("transparent_hugepage=", setup_transparent_hugepage); + +pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) +{ + if (likely(vma->vm_flags & VM_WRITE)) + pmd = pmd_mkwrite(pmd); + return pmd; +} + +#ifdef CONFIG_MEMCG +static inline struct deferred_split *get_deferred_split_queue(struct page *page) +{ + struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; + struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); + + if (memcg) + return &memcg->deferred_split_queue; + else + return &pgdat->deferred_split_queue; +} +#else +static inline struct deferred_split *get_deferred_split_queue(struct page *page) +{ + struct pglist_data *pgdat = NODE_DATA(page_to_nid(page)); + + return &pgdat->deferred_split_queue; +} +#endif + +void prep_transhuge_page(struct page *page) +{ + /* + * we use page->mapping and page->indexlru in second tail page + * as list_head: assuming THP order >= 2 + */ + + INIT_LIST_HEAD(page_deferred_list(page)); + set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); +} + +bool is_transparent_hugepage(struct page *page) +{ + if (!PageCompound(page)) + return false; + + page = compound_head(page); + return is_huge_zero_page(page) || + page[1].compound_dtor == TRANSHUGE_PAGE_DTOR; +} +EXPORT_SYMBOL_GPL(is_transparent_hugepage); + +static unsigned long __thp_get_unmapped_area(struct file *filp, + unsigned long addr, unsigned long len, + loff_t off, unsigned long flags, unsigned long size) +{ + loff_t off_end = off + len; + loff_t off_align = round_up(off, size); + unsigned long len_pad, ret; + + if (off_end <= off_align || (off_end - off_align) < size) + return 0; + + len_pad = len + size; + if (len_pad < len || (off + len_pad) < off) + return 0; + + ret = current->mm->get_unmapped_area(filp, addr, len_pad, + off >> PAGE_SHIFT, flags); + + /* + * The failure might be due to length padding. The caller will retry + * without the padding. + */ + if (IS_ERR_VALUE(ret)) + return 0; + + /* + * Do not try to align to THP boundary if allocation at the address + * hint succeeds. + */ + if (ret == addr) + return addr; + + ret += (off - ret) & (size - 1); + return ret; +} + +unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, + unsigned long len, unsigned long pgoff, unsigned long flags) +{ + unsigned long ret; + loff_t off = (loff_t)pgoff << PAGE_SHIFT; + + if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD)) + goto out; + + ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE); + if (ret) + return ret; +out: + return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags); +} +EXPORT_SYMBOL_GPL(thp_get_unmapped_area); + +static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf, + struct page *page, gfp_t gfp) +{ + struct vm_area_struct *vma = vmf->vma; + pgtable_t pgtable; + unsigned long haddr = vmf->address & HPAGE_PMD_MASK; + vm_fault_t ret = 0; + + VM_BUG_ON_PAGE(!PageCompound(page), page); + + if (mem_cgroup_charge(page, vma->vm_mm, gfp)) { + put_page(page); + count_vm_event(THP_FAULT_FALLBACK); + count_vm_event(THP_FAULT_FALLBACK_CHARGE); + return VM_FAULT_FALLBACK; + } + cgroup_throttle_swaprate(page, gfp); + + pgtable = pte_alloc_one(vma->vm_mm); + if (unlikely(!pgtable)) { + ret = VM_FAULT_OOM; + goto release; + } + + clear_huge_page(page, vmf->address, HPAGE_PMD_NR); + /* + * The memory barrier inside __SetPageUptodate makes sure that + * clear_huge_page writes become visible before the set_pmd_at() + * write. + */ + __SetPageUptodate(page); + + vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); + if (unlikely(!pmd_none(*vmf->pmd))) { + goto unlock_release; + } else { + pmd_t entry; + + ret = check_stable_address_space(vma->vm_mm); + if (ret) + goto unlock_release; + + /* Deliver the page fault to userland */ + if (userfaultfd_missing(vma)) { + vm_fault_t ret2; + + spin_unlock(vmf->ptl); + put_page(page); + pte_free(vma->vm_mm, pgtable); + ret2 = handle_userfault(vmf, VM_UFFD_MISSING); + VM_BUG_ON(ret2 & VM_FAULT_FALLBACK); + return ret2; + } + + entry = mk_huge_pmd(page, vma->vm_page_prot); + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + page_add_new_anon_rmap(page, vma, haddr, true); + lru_cache_add_inactive_or_unevictable(page, vma); + pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); + set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); + add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); + mm_inc_nr_ptes(vma->vm_mm); + spin_unlock(vmf->ptl); + count_vm_event(THP_FAULT_ALLOC); + count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC); + } + + return 0; +unlock_release: + spin_unlock(vmf->ptl); +release: + if (pgtable) + pte_free(vma->vm_mm, pgtable); + put_page(page); + return ret; + +} + +/* + * always: directly stall for all thp allocations + * defer: wake kswapd and fail if not immediately available + * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise + * fail if not immediately available + * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately + * available + * never: never stall for any thp allocation + */ +static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) +{ + const bool vma_madvised = !!(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 bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, + struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, + struct page *zero_page) +{ + pmd_t entry; + if (!pmd_none(*pmd)) + return false; + entry = mk_pmd(zero_page, vma->vm_page_prot); + entry = pmd_mkhuge(entry); + if (pgtable) + pgtable_trans_huge_deposit(mm, pmd, pgtable); + set_pmd_at(mm, haddr, pmd, entry); + mm_inc_nr_ptes(mm); + return true; +} + +vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf) +{ + struct vm_area_struct *vma = vmf->vma; + gfp_t gfp; + struct page *page; + unsigned long haddr = vmf->address & HPAGE_PMD_MASK; + + if (!transhuge_vma_suitable(vma, haddr)) + return VM_FAULT_FALLBACK; + if (unlikely(anon_vma_prepare(vma))) + return VM_FAULT_OOM; + if (unlikely(khugepaged_enter(vma, vma->vm_flags))) + return VM_FAULT_OOM; + if (!(vmf->flags & FAULT_FLAG_WRITE) && + !mm_forbids_zeropage(vma->vm_mm) && + transparent_hugepage_use_zero_page()) { + pgtable_t pgtable; + struct page *zero_page; + vm_fault_t ret; + pgtable = pte_alloc_one(vma->vm_mm); + if (unlikely(!pgtable)) + return VM_FAULT_OOM; + zero_page = mm_get_huge_zero_page(vma->vm_mm); + if (unlikely(!zero_page)) { + pte_free(vma->vm_mm, pgtable); + count_vm_event(THP_FAULT_FALLBACK); + return VM_FAULT_FALLBACK; + } + vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); + ret = 0; + if (pmd_none(*vmf->pmd)) { + ret = check_stable_address_space(vma->vm_mm); + if (ret) { + spin_unlock(vmf->ptl); + pte_free(vma->vm_mm, pgtable); + } else if (userfaultfd_missing(vma)) { + spin_unlock(vmf->ptl); + pte_free(vma->vm_mm, pgtable); + ret = handle_userfault(vmf, VM_UFFD_MISSING); + VM_BUG_ON(ret & VM_FAULT_FALLBACK); + } else { + set_huge_zero_page(pgtable, vma->vm_mm, vma, + haddr, vmf->pmd, zero_page); + spin_unlock(vmf->ptl); + } + } else { + spin_unlock(vmf->ptl); + pte_free(vma->vm_mm, pgtable); + } + return ret; + } + gfp = alloc_hugepage_direct_gfpmask(vma); + page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); + if (unlikely(!page)) { + count_vm_event(THP_FAULT_FALLBACK); + return VM_FAULT_FALLBACK; + } + prep_transhuge_page(page); + return __do_huge_pmd_anonymous_page(vmf, page, gfp); +} + +static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, + pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write, + pgtable_t pgtable) +{ + struct mm_struct *mm = vma->vm_mm; + pmd_t entry; + spinlock_t *ptl; + + ptl = pmd_lock(mm, pmd); + if (!pmd_none(*pmd)) { + if (write) { + if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) { + WARN_ON_ONCE(!is_huge_zero_pmd(*pmd)); + goto out_unlock; + } + entry = pmd_mkyoung(*pmd); + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + if (pmdp_set_access_flags(vma, addr, pmd, entry, 1)) + update_mmu_cache_pmd(vma, addr, pmd); + } + + goto out_unlock; + } + + entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); + if (pfn_t_devmap(pfn)) + entry = pmd_mkdevmap(entry); + if (write) { + entry = pmd_mkyoung(pmd_mkdirty(entry)); + entry = maybe_pmd_mkwrite(entry, vma); + } + + if (pgtable) { + pgtable_trans_huge_deposit(mm, pmd, pgtable); + mm_inc_nr_ptes(mm); + pgtable = NULL; + } + + set_pmd_at(mm, addr, pmd, entry); + update_mmu_cache_pmd(vma, addr, pmd); + +out_unlock: + spin_unlock(ptl); + if (pgtable) + pte_free(mm, pgtable); +} + +/** + * vmf_insert_pfn_pmd_prot - insert a pmd size pfn + * @vmf: Structure describing the fault + * @pfn: pfn to insert + * @pgprot: page protection to use + * @write: whether it's a write fault + * + * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and + * also consult the vmf_insert_mixed_prot() documentation when + * @pgprot != @vmf->vma->vm_page_prot. + * + * Return: vm_fault_t value. + */ +vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn, + pgprot_t pgprot, bool write) +{ + unsigned long addr = vmf->address & PMD_MASK; + struct vm_area_struct *vma = vmf->vma; + pgtable_t pgtable = NULL; + + /* + * If we had pmd_special, we could avoid all these restrictions, + * but we need to be consistent with PTEs and architectures that + * can't support a 'special' bit. + */ + BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && + !pfn_t_devmap(pfn)); + BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == + (VM_PFNMAP|VM_MIXEDMAP)); + BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); + + if (addr < vma->vm_start || addr >= vma->vm_end) + return VM_FAULT_SIGBUS; + + if (arch_needs_pgtable_deposit()) { + pgtable = pte_alloc_one(vma->vm_mm); + if (!pgtable) + return VM_FAULT_OOM; + } + + track_pfn_insert(vma, &pgprot, pfn); + + insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable); + return VM_FAULT_NOPAGE; +} +EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot); + +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD +static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma) +{ + if (likely(vma->vm_flags & VM_WRITE)) + pud = pud_mkwrite(pud); + return pud; +} + +static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, + pud_t *pud, pfn_t pfn, pgprot_t prot, bool write) +{ + struct mm_struct *mm = vma->vm_mm; + pud_t entry; + spinlock_t *ptl; + + ptl = pud_lock(mm, pud); + if (!pud_none(*pud)) { + if (write) { + if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) { + WARN_ON_ONCE(!is_huge_zero_pud(*pud)); + goto out_unlock; + } + entry = pud_mkyoung(*pud); + entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma); + if (pudp_set_access_flags(vma, addr, pud, entry, 1)) + update_mmu_cache_pud(vma, addr, pud); + } + goto out_unlock; + } + + entry = pud_mkhuge(pfn_t_pud(pfn, prot)); + if (pfn_t_devmap(pfn)) + entry = pud_mkdevmap(entry); + if (write) { + entry = pud_mkyoung(pud_mkdirty(entry)); + entry = maybe_pud_mkwrite(entry, vma); + } + set_pud_at(mm, addr, pud, entry); + update_mmu_cache_pud(vma, addr, pud); + +out_unlock: + spin_unlock(ptl); +} + +/** + * vmf_insert_pfn_pud_prot - insert a pud size pfn + * @vmf: Structure describing the fault + * @pfn: pfn to insert + * @pgprot: page protection to use + * @write: whether it's a write fault + * + * Insert a pud size pfn. See vmf_insert_pfn() for additional info and + * also consult the vmf_insert_mixed_prot() documentation when + * @pgprot != @vmf->vma->vm_page_prot. + * + * Return: vm_fault_t value. + */ +vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn, + pgprot_t pgprot, bool write) +{ + unsigned long addr = vmf->address & PUD_MASK; + struct vm_area_struct *vma = vmf->vma; + + /* + * If we had pud_special, we could avoid all these restrictions, + * but we need to be consistent with PTEs and architectures that + * can't support a 'special' bit. + */ + BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) && + !pfn_t_devmap(pfn)); + BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == + (VM_PFNMAP|VM_MIXEDMAP)); + BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); + + if (addr < vma->vm_start || addr >= vma->vm_end) + return VM_FAULT_SIGBUS; + + track_pfn_insert(vma, &pgprot, pfn); + + insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write); + return VM_FAULT_NOPAGE; +} +EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot); +#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ + +static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, + pmd_t *pmd, int flags) +{ + pmd_t _pmd; + + _pmd = pmd_mkyoung(*pmd); + if (flags & FOLL_WRITE) + _pmd = pmd_mkdirty(_pmd); + if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, + pmd, _pmd, flags & FOLL_WRITE)) + update_mmu_cache_pmd(vma, addr, pmd); +} + +struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, + pmd_t *pmd, int flags, struct dev_pagemap **pgmap) +{ + unsigned long pfn = pmd_pfn(*pmd); + struct mm_struct *mm = vma->vm_mm; + struct page *page; + + assert_spin_locked(pmd_lockptr(mm, pmd)); + + /* + * When we COW a devmap PMD entry, we split it into PTEs, so we should + * not be in this function with `flags & FOLL_COW` set. + */ + WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set"); + + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == + (FOLL_PIN | FOLL_GET))) + return NULL; + + if (flags & FOLL_WRITE && !pmd_write(*pmd)) + return NULL; + + if (pmd_present(*pmd) && pmd_devmap(*pmd)) + /* pass */; + else + return NULL; + + if (flags & FOLL_TOUCH) + touch_pmd(vma, addr, pmd, flags); + + /* + * device mapped pages can only be returned if the + * caller will manage the page reference count. + */ + if (!(flags & (FOLL_GET | FOLL_PIN))) + return ERR_PTR(-EEXIST); + + pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; + *pgmap = get_dev_pagemap(pfn, *pgmap); + if (!*pgmap) + return ERR_PTR(-EFAULT); + page = pfn_to_page(pfn); + if (!try_grab_page(page, flags)) + page = ERR_PTR(-ENOMEM); + + return page; +} + +int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, + pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, + struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) +{ + spinlock_t *dst_ptl, *src_ptl; + struct page *src_page; + pmd_t pmd; + pgtable_t pgtable = NULL; + int ret = -ENOMEM; + + /* Skip if can be re-fill on fault */ + if (!vma_is_anonymous(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_write_migration_entry(entry)) { + make_migration_entry_read(&entry); + pmd = swp_entry_to_pmd(entry); + if (pmd_swp_soft_dirty(*src_pmd)) + pmd = pmd_swp_mksoft_dirty(pmd); + 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)) { + /* + * get_huge_zero_page() will never allocate a new page here, + * since we already have a zero page to copy. It just takes a + * reference. + */ + mm_get_huge_zero_page(dst_mm); + goto out_zero_page; + } + + src_page = pmd_page(pmd); + VM_BUG_ON_PAGE(!PageHead(src_page), src_page); + + /* + * If this page is a potentially pinned page, split and retry the fault + * with smaller page size. Normally this should not happen because the + * userspace should use MADV_DONTFORK upon pinned regions. This is a + * best effort that the pinned pages won't be replaced by another + * random page during the coming copy-on-write. + */ + if (unlikely(is_cow_mapping(src_vma->vm_flags) && + atomic_read(&src_mm->has_pinned) && + page_maybe_dma_pinned(src_page))) { + 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; + } + + get_page(src_page); + page_dup_rmap(src_page, true); + 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 +static void touch_pud(struct vm_area_struct *vma, unsigned long addr, + pud_t *pud, int flags) +{ + pud_t _pud; + + _pud = pud_mkyoung(*pud); + if (flags & FOLL_WRITE) + _pud = pud_mkdirty(_pud); + if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK, + pud, _pud, flags & FOLL_WRITE)) + update_mmu_cache_pud(vma, addr, pud); +} + +struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, + pud_t *pud, int flags, struct dev_pagemap **pgmap) +{ + unsigned long pfn = pud_pfn(*pud); + struct mm_struct *mm = vma->vm_mm; + struct page *page; + + assert_spin_locked(pud_lockptr(mm, pud)); + + if (flags & FOLL_WRITE && !pud_write(*pud)) + return NULL; + + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == + (FOLL_PIN | FOLL_GET))) + return NULL; + + if (pud_present(*pud) && pud_devmap(*pud)) + /* pass */; + else + return NULL; + + if (flags & FOLL_TOUCH) + touch_pud(vma, addr, pud, flags); + + /* + * device mapped pages can only be returned if the + * caller will manage the page reference count. + * + * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here: + */ + if (!(flags & (FOLL_GET | FOLL_PIN))) + return ERR_PTR(-EEXIST); + + pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT; + *pgmap = get_dev_pagemap(pfn, *pgmap); + if (!*pgmap) + return ERR_PTR(-EFAULT); + page = pfn_to_page(pfn); + if (!try_grab_page(page, flags)) + page = ERR_PTR(-ENOMEM); + + return page; +} + +int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, + pud_t *dst_pud, pud_t *src_pud, unsigned long addr, + struct vm_area_struct *vma) +{ + spinlock_t *dst_ptl, *src_ptl; + pud_t pud; + int ret; + + dst_ptl = pud_lock(dst_mm, dst_pud); + src_ptl = pud_lockptr(src_mm, src_pud); + spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); + + ret = -EAGAIN; + pud = *src_pud; + if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud))) + goto out_unlock; + + /* + * When page table lock is held, the huge zero pud should not be + * under splitting since we don't split the page itself, only pud to + * a page table. + */ + if (is_huge_zero_pud(pud)) { + /* No huge zero pud yet */ + } + + /* Please refer to comments in copy_huge_pmd() */ + if (unlikely(is_cow_mapping(vma->vm_flags) && + atomic_read(&src_mm->has_pinned) && + page_maybe_dma_pinned(pud_page(pud)))) { + spin_unlock(src_ptl); + spin_unlock(dst_ptl); + __split_huge_pud(vma, src_pud, addr); + return -EAGAIN; + } + + pudp_set_wrprotect(src_mm, addr, src_pud); + pud = pud_mkold(pud_wrprotect(pud)); + set_pud_at(dst_mm, addr, dst_pud, pud); + + ret = 0; +out_unlock: + spin_unlock(src_ptl); + spin_unlock(dst_ptl); + return ret; +} + +void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud) +{ + pud_t entry; + unsigned long haddr; + bool write = vmf->flags & FAULT_FLAG_WRITE; + + vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud); + if (unlikely(!pud_same(*vmf->pud, orig_pud))) + goto unlock; + + entry = pud_mkyoung(orig_pud); + if (write) + entry = pud_mkdirty(entry); + haddr = vmf->address & HPAGE_PUD_MASK; + if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write)) + update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud); + +unlock: + spin_unlock(vmf->ptl); +} +#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ + +void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) +{ + pmd_t entry; + unsigned long haddr; + bool write = vmf->flags & FAULT_FLAG_WRITE; + + vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); + if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) + goto unlock; + + entry = pmd_mkyoung(orig_pmd); + if (write) + entry = pmd_mkdirty(entry); + haddr = vmf->address & HPAGE_PMD_MASK; + if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) + update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); + +unlock: + spin_unlock(vmf->ptl); +} + +vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) +{ + struct vm_area_struct *vma = vmf->vma; + struct page *page; + unsigned long haddr = vmf->address & HPAGE_PMD_MASK; + + vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); + VM_BUG_ON_VMA(!vma->anon_vma, vma); + + if (is_huge_zero_pmd(orig_pmd)) + goto fallback; + + spin_lock(vmf->ptl); + + if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { + spin_unlock(vmf->ptl); + return 0; + } + + page = pmd_page(orig_pmd); + VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); + + /* Lock page for reuse_swap_page() */ + if (!trylock_page(page)) { + get_page(page); + spin_unlock(vmf->ptl); + lock_page(page); + spin_lock(vmf->ptl); + if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { + spin_unlock(vmf->ptl); + unlock_page(page); + put_page(page); + return 0; + } + put_page(page); + } + + /* + * We can only reuse the page if nobody else maps the huge page or it's + * part. + */ + if (reuse_swap_page(page, NULL)) { + pmd_t entry; + entry = pmd_mkyoung(orig_pmd); + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1)) + update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); + unlock_page(page); + spin_unlock(vmf->ptl); + return VM_FAULT_WRITE; + } + + unlock_page(page); + spin_unlock(vmf->ptl); +fallback: + __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL); + return VM_FAULT_FALLBACK; +} + +/* + * FOLL_FORCE can write to even unwritable pmd's, but only + * after we've gone through a COW cycle and they are dirty. + */ +static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) +{ + return pmd_write(pmd) || + ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); +} + +struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, + unsigned long addr, + pmd_t *pmd, + unsigned int flags) +{ + struct mm_struct *mm = vma->vm_mm; + struct page *page = NULL; + + assert_spin_locked(pmd_lockptr(mm, pmd)); + + if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) + goto out; + + /* Avoid dumping huge zero page */ + if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) + return ERR_PTR(-EFAULT); + + /* Full NUMA hinting faults to serialise migration in fault paths */ + if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) + goto out; + + page = pmd_page(*pmd); + VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); + + if (!try_grab_page(page, flags)) + return ERR_PTR(-ENOMEM); + + if (flags & FOLL_TOUCH) + touch_pmd(vma, addr, pmd, flags); + + if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { + /* + * We don't mlock() pte-mapped THPs. This way we can avoid + * leaking mlocked pages into non-VM_LOCKED VMAs. + * + * For anon THP: + * + * In most cases the pmd is the only mapping of the page as we + * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for + * writable private mappings in populate_vma_page_range(). + * + * The only scenario when we have the page shared here is if we + * mlocking read-only mapping shared over fork(). We skip + * mlocking such pages. + * + * For file THP: + * + * We can expect PageDoubleMap() to be stable under page lock: + * for file pages we set it in page_add_file_rmap(), which + * requires page to be locked. + */ + + if (PageAnon(page) && compound_mapcount(page) != 1) + goto skip_mlock; + if (PageDoubleMap(page) || !page->mapping) + goto skip_mlock; + if (!trylock_page(page)) + goto skip_mlock; + if (page->mapping && !PageDoubleMap(page)) + mlock_vma_page(page); + unlock_page(page); + } +skip_mlock: + page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; + VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page); + +out: + return page; +} + +/* NUMA hinting page fault entry point for trans huge pmds */ +vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) +{ + struct vm_area_struct *vma = vmf->vma; + struct anon_vma *anon_vma = NULL; + struct page *page; + unsigned long haddr = vmf->address & HPAGE_PMD_MASK; + int page_nid = NUMA_NO_NODE, this_nid = numa_node_id(); + int target_nid, last_cpupid = -1; + bool page_locked; + bool migrated = false; + bool was_writable; + int flags = 0; + + vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); + if (unlikely(!pmd_same(pmd, *vmf->pmd))) + goto out_unlock; + + /* + * If there are potential migrations, wait for completion and retry + * without disrupting NUMA hinting information. Do not relock and + * check_same as the page may no longer be mapped. + */ + if (unlikely(pmd_trans_migrating(*vmf->pmd))) { + page = pmd_page(*vmf->pmd); + if (!get_page_unless_zero(page)) + goto out_unlock; + spin_unlock(vmf->ptl); + put_and_wait_on_page_locked(page); + goto out; + } + + page = pmd_page(pmd); + BUG_ON(is_huge_zero_page(page)); + page_nid = page_to_nid(page); + last_cpupid = page_cpupid_last(page); + count_vm_numa_event(NUMA_HINT_FAULTS); + if (page_nid == this_nid) { + count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); + flags |= TNF_FAULT_LOCAL; + } + + /* See similar comment in do_numa_page for explanation */ + if (!pmd_savedwrite(pmd)) + flags |= TNF_NO_GROUP; + + /* + * Acquire the page lock to serialise THP migrations but avoid dropping + * page_table_lock if at all possible + */ + page_locked = trylock_page(page); + target_nid = mpol_misplaced(page, vma, haddr); + if (target_nid == NUMA_NO_NODE) { + /* If the page was locked, there are no parallel migrations */ + if (page_locked) + goto clear_pmdnuma; + } + + /* Migration could have started since the pmd_trans_migrating check */ + if (!page_locked) { + page_nid = NUMA_NO_NODE; + if (!get_page_unless_zero(page)) + goto out_unlock; + spin_unlock(vmf->ptl); + put_and_wait_on_page_locked(page); + goto out; + } + + /* + * Page is misplaced. Page lock serialises migrations. Acquire anon_vma + * to serialises splits + */ + get_page(page); + spin_unlock(vmf->ptl); + anon_vma = page_lock_anon_vma_read(page); + + /* Confirm the PMD did not change while page_table_lock was released */ + spin_lock(vmf->ptl); + if (unlikely(!pmd_same(pmd, *vmf->pmd))) { + unlock_page(page); + put_page(page); + page_nid = NUMA_NO_NODE; + goto out_unlock; + } + + /* Bail if we fail to protect against THP splits for any reason */ + if (unlikely(!anon_vma)) { + put_page(page); + page_nid = NUMA_NO_NODE; + goto clear_pmdnuma; + } + + /* + * Since we took the NUMA fault, we must have observed the !accessible + * bit. Make sure all other CPUs agree with that, to avoid them + * modifying the page we're about to migrate. + * + * Must be done under PTL such that we'll observe the relevant + * inc_tlb_flush_pending(). + * + * We are not sure a pending tlb flush here is for a huge page + * mapping or not. Hence use the tlb range variant + */ + if (mm_tlb_flush_pending(vma->vm_mm)) { + flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE); + /* + * change_huge_pmd() released the pmd lock before + * invalidating the secondary MMUs sharing the primary + * MMU pagetables (with ->invalidate_range()). The + * mmu_notifier_invalidate_range_end() (which + * internally calls ->invalidate_range()) in + * change_pmd_range() will run after us, so we can't + * rely on it here and we need an explicit invalidate. + */ + mmu_notifier_invalidate_range(vma->vm_mm, haddr, + haddr + HPAGE_PMD_SIZE); + } + + /* + * Migrate the THP to the requested node, returns with page unlocked + * and access rights restored. + */ + spin_unlock(vmf->ptl); + + migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma, + vmf->pmd, pmd, vmf->address, page, target_nid); + if (migrated) { + flags |= TNF_MIGRATED; + page_nid = target_nid; + } else + flags |= TNF_MIGRATE_FAIL; + + goto out; +clear_pmdnuma: + BUG_ON(!PageLocked(page)); + was_writable = pmd_savedwrite(pmd); + pmd = pmd_modify(pmd, vma->vm_page_prot); + pmd = pmd_mkyoung(pmd); + if (was_writable) + pmd = pmd_mkwrite(pmd); + set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd); + update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); + unlock_page(page); +out_unlock: + spin_unlock(vmf->ptl); + +out: + if (anon_vma) + page_unlock_anon_vma_read(anon_vma); + + if (page_nid != NUMA_NO_NODE) + task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, + flags); + + return 0; +} + +/* + * Return true if we do MADV_FREE successfully on entire pmd page. + * Otherwise, return false. + */ +bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, + pmd_t *pmd, unsigned long addr, unsigned long next) +{ + spinlock_t *ptl; + pmd_t orig_pmd; + struct page *page; + struct mm_struct *mm = tlb->mm; + bool ret = false; + + tlb_change_page_size(tlb, HPAGE_PMD_SIZE); + + ptl = pmd_trans_huge_lock(pmd, vma); + if (!ptl) + goto out_unlocked; + + orig_pmd = *pmd; + if (is_huge_zero_pmd(orig_pmd)) + goto out; + + if (unlikely(!pmd_present(orig_pmd))) { + VM_BUG_ON(thp_migration_supported() && + !is_pmd_migration_entry(orig_pmd)); + goto out; + } + + page = pmd_page(orig_pmd); + /* + * If other processes are mapping this page, we couldn't discard + * the page unless they all do MADV_FREE so let's skip the page. + */ + if (total_mapcount(page) != 1) + goto out; + + if (!trylock_page(page)) + goto out; + + /* + * If user want to discard part-pages of THP, split it so MADV_FREE + * will deactivate only them. + */ + if (next - addr != HPAGE_PMD_SIZE) { + get_page(page); + spin_unlock(ptl); + split_huge_page(page); + unlock_page(page); + put_page(page); + goto out_unlocked; + } + + if (PageDirty(page)) + ClearPageDirty(page); + unlock_page(page); + + if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { + pmdp_invalidate(vma, addr, pmd); + orig_pmd = pmd_mkold(orig_pmd); + orig_pmd = pmd_mkclean(orig_pmd); + + set_pmd_at(mm, addr, pmd, orig_pmd); + tlb_remove_pmd_tlb_entry(tlb, pmd, addr); + } + + mark_page_lazyfree(page); + ret = true; +out: + spin_unlock(ptl); +out_unlocked: + return ret; +} + +static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) +{ + pgtable_t pgtable; + + pgtable = pgtable_trans_huge_withdraw(mm, pmd); + pte_free(mm, pgtable); + mm_dec_nr_ptes(mm); +} + +int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, + pmd_t *pmd, unsigned long addr) +{ + pmd_t orig_pmd; + spinlock_t *ptl; + + tlb_change_page_size(tlb, HPAGE_PMD_SIZE); + + ptl = __pmd_trans_huge_lock(pmd, vma); + if (!ptl) + return 0; + /* + * For architectures like ppc64 we look at deposited pgtable + * when calling pmdp_huge_get_and_clear. So do the + * pgtable_trans_huge_withdraw after finishing pmdp related + * operations. + */ + orig_pmd = pmdp_huge_get_and_clear_full(vma, addr, pmd, + tlb->fullmm); + tlb_remove_pmd_tlb_entry(tlb, pmd, addr); + if (vma_is_special_huge(vma)) { + if (arch_needs_pgtable_deposit()) + zap_deposited_table(tlb->mm, pmd); + spin_unlock(ptl); + if (is_huge_zero_pmd(orig_pmd)) + tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); + } else if (is_huge_zero_pmd(orig_pmd)) { + zap_deposited_table(tlb->mm, pmd); + spin_unlock(ptl); + tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); + } else { + struct page *page = NULL; + int flush_needed = 1; + + if (pmd_present(orig_pmd)) { + page = pmd_page(orig_pmd); + page_remove_rmap(page, true); + VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); + VM_BUG_ON_PAGE(!PageHead(page), page); + } else if (thp_migration_supported()) { + swp_entry_t entry; + + VM_BUG_ON(!is_pmd_migration_entry(orig_pmd)); + entry = pmd_to_swp_entry(orig_pmd); + page = migration_entry_to_page(entry); + flush_needed = 0; + } else + WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!"); + + if (PageAnon(page)) { + zap_deposited_table(tlb->mm, pmd); + add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); + } else { + if (arch_needs_pgtable_deposit()) + zap_deposited_table(tlb->mm, pmd); + add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR); + } + + spin_unlock(ptl); + if (flush_needed) + tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); + } + return 1; +} + +#ifndef pmd_move_must_withdraw +static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, + spinlock_t *old_pmd_ptl, + struct vm_area_struct *vma) +{ + /* + * With split pmd lock we also need to move preallocated + * PTE page table if new_pmd is on different PMD page table. + * + * We also don't deposit and withdraw tables for file pages. + */ + return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma); +} +#endif + +static pmd_t move_soft_dirty_pmd(pmd_t pmd) +{ +#ifdef CONFIG_MEM_SOFT_DIRTY + if (unlikely(is_pmd_migration_entry(pmd))) + pmd = pmd_swp_mksoft_dirty(pmd); + else if (pmd_present(pmd)) + pmd = pmd_mksoft_dirty(pmd); +#endif + return pmd; +} + +bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, + unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd) +{ + spinlock_t *old_ptl, *new_ptl; + pmd_t pmd; + struct mm_struct *mm = vma->vm_mm; + bool force_flush = false; + + /* + * The destination pmd shouldn't be established, free_pgtables() + * should have release it. + */ + if (WARN_ON(!pmd_none(*new_pmd))) { + VM_BUG_ON(pmd_trans_huge(*new_pmd)); + return false; + } + + /* + * We don't have to worry about the ordering of src and dst + * ptlocks because exclusive mmap_lock prevents deadlock. + */ + old_ptl = __pmd_trans_huge_lock(old_pmd, vma); + if (old_ptl) { + new_ptl = pmd_lockptr(mm, new_pmd); + if (new_ptl != old_ptl) + spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); + pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); + if (pmd_present(pmd)) + force_flush = true; + VM_BUG_ON(!pmd_none(*new_pmd)); + + if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) { + pgtable_t pgtable; + pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); + pgtable_trans_huge_deposit(mm, new_pmd, pgtable); + } + pmd = move_soft_dirty_pmd(pmd); + set_pmd_at(mm, new_addr, new_pmd, pmd); + if (force_flush) + flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); + if (new_ptl != old_ptl) + spin_unlock(new_ptl); + spin_unlock(old_ptl); + return true; + } + return false; +} + +/* + * Returns + * - 0 if PMD could not be locked + * - 1 if PMD was locked but protections unchange and TLB flush unnecessary + * - HPAGE_PMD_NR is protections changed and TLB flush necessary + */ +int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, + unsigned long addr, pgprot_t newprot, unsigned long cp_flags) +{ + struct mm_struct *mm = vma->vm_mm; + spinlock_t *ptl; + pmd_t entry; + bool preserve_write; + int ret; + bool prot_numa = cp_flags & MM_CP_PROT_NUMA; + bool uffd_wp = cp_flags & MM_CP_UFFD_WP; + bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; + + ptl = __pmd_trans_huge_lock(pmd, vma); + if (!ptl) + return 0; + + preserve_write = prot_numa && pmd_write(*pmd); + ret = 1; + +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION + if (is_swap_pmd(*pmd)) { + swp_entry_t entry = pmd_to_swp_entry(*pmd); + + VM_BUG_ON(!is_pmd_migration_entry(*pmd)); + if (is_write_migration_entry(entry)) { + pmd_t newpmd; + /* + * A protection check is difficult so + * just be safe and disable write + */ + make_migration_entry_read(&entry); + newpmd = swp_entry_to_pmd(entry); + if (pmd_swp_soft_dirty(*pmd)) + newpmd = pmd_swp_mksoft_dirty(newpmd); + if (pmd_swp_uffd_wp(*pmd)) + newpmd = pmd_swp_mkuffd_wp(newpmd); + set_pmd_at(mm, addr, pmd, newpmd); + } + goto unlock; + } +#endif + + /* + * Avoid trapping faults against the zero page. The read-only + * data is likely to be read-cached on the local CPU and + * local/remote hits to the zero page are not interesting. + */ + if (prot_numa && is_huge_zero_pmd(*pmd)) + goto unlock; + + if (prot_numa && pmd_protnone(*pmd)) + goto unlock; + + /* + * In case prot_numa, we are under mmap_read_lock(mm). It's critical + * to not clear pmd intermittently to avoid race with MADV_DONTNEED + * which is also under mmap_read_lock(mm): + * + * CPU0: CPU1: + * change_huge_pmd(prot_numa=1) + * pmdp_huge_get_and_clear_notify() + * madvise_dontneed() + * zap_pmd_range() + * pmd_trans_huge(*pmd) == 0 (without ptl) + * // skip the pmd + * set_pmd_at(); + * // pmd is re-established + * + * The race makes MADV_DONTNEED miss the huge pmd and don't clear it + * which may break userspace. + * + * pmdp_invalidate() is required to make sure we don't miss + * dirty/young flags set by hardware. + */ + entry = pmdp_invalidate(vma, addr, pmd); + + entry = pmd_modify(entry, newprot); + if (preserve_write) + entry = pmd_mk_savedwrite(entry); + if (uffd_wp) { + entry = pmd_wrprotect(entry); + entry = pmd_mkuffd_wp(entry); + } else if (uffd_wp_resolve) { + /* + * Leave the write bit to be handled by PF interrupt + * handler, then things like COW could be properly + * handled. + */ + entry = pmd_clear_uffd_wp(entry); + } + ret = HPAGE_PMD_NR; + set_pmd_at(mm, addr, pmd, entry); + BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry)); +unlock: + spin_unlock(ptl); + return ret; +} + +/* + * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise. + * + * Note that if it returns page table lock pointer, this routine returns without + * unlocking page table lock. So callers must unlock it. + */ +spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) +{ + spinlock_t *ptl; + ptl = pmd_lock(vma->vm_mm, pmd); + if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || + pmd_devmap(*pmd))) + return ptl; + spin_unlock(ptl); + return NULL; +} + +/* + * Returns true if a given pud maps a thp, false otherwise. + * + * Note that if it returns true, this routine returns without unlocking page + * table lock. So callers must unlock it. + */ +spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma) +{ + spinlock_t *ptl; + + ptl = pud_lock(vma->vm_mm, pud); + if (likely(pud_trans_huge(*pud) || pud_devmap(*pud))) + return ptl; + spin_unlock(ptl); + return NULL; +} + +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD +int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, + pud_t *pud, unsigned long addr) +{ + spinlock_t *ptl; + + ptl = __pud_trans_huge_lock(pud, vma); + if (!ptl) + return 0; + /* + * For architectures like ppc64 we look at deposited pgtable + * when calling pudp_huge_get_and_clear. So do the + * pgtable_trans_huge_withdraw after finishing pudp related + * operations. + */ + pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm); + tlb_remove_pud_tlb_entry(tlb, pud, addr); + if (vma_is_special_huge(vma)) { + spin_unlock(ptl); + /* No zero page support yet */ + } else { + /* No support for anonymous PUD pages yet */ + BUG(); + } + return 1; +} + +static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud, + unsigned long haddr) +{ + VM_BUG_ON(haddr & ~HPAGE_PUD_MASK); + VM_BUG_ON_VMA(vma->vm_start > haddr, vma); + VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma); + VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud)); + + count_vm_event(THP_SPLIT_PUD); + + pudp_huge_clear_flush_notify(vma, haddr, pud); +} + +void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud, + unsigned long address) +{ + spinlock_t *ptl; + struct mmu_notifier_range range; + + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, + address & HPAGE_PUD_MASK, + (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE); + mmu_notifier_invalidate_range_start(&range); + ptl = pud_lock(vma->vm_mm, pud); + if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud))) + goto out; + __split_huge_pud_locked(vma, pud, range.start); + +out: + spin_unlock(ptl); + /* + * No need to double call mmu_notifier->invalidate_range() callback as + * the above pudp_huge_clear_flush_notify() did already call it. + */ + mmu_notifier_invalidate_range_only_end(&range); +} +#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ + +static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, + unsigned long haddr, pmd_t *pmd) +{ + struct mm_struct *mm = vma->vm_mm; + pgtable_t pgtable; + pmd_t _pmd, old_pmd; + int i; + + /* + * Leave pmd empty until pte is filled note that it is fine to delay + * notification until mmu_notifier_invalidate_range_end() as we are + * replacing a zero pmd write protected page with a zero pte write + * protected page. + * + * See Documentation/vm/mmu_notifier.rst + */ + old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd); + + pgtable = pgtable_trans_huge_withdraw(mm, pmd); + pmd_populate(mm, &_pmd, pgtable); + + for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { + pte_t *pte, entry; + entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); + entry = pte_mkspecial(entry); + if (pmd_uffd_wp(old_pmd)) + entry = pte_mkuffd_wp(entry); + pte = pte_offset_map(&_pmd, haddr); + VM_BUG_ON(!pte_none(*pte)); + set_pte_at(mm, haddr, pte, entry); + pte_unmap(pte); + } + smp_wmb(); /* make pte visible before pmd */ + pmd_populate(mm, pmd, pgtable); +} + +static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, + unsigned long haddr, bool freeze) +{ + struct mm_struct *mm = vma->vm_mm; + struct page *page; + pgtable_t pgtable; + pmd_t old_pmd, _pmd; + bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; + unsigned long addr; + int i; + + VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); + VM_BUG_ON_VMA(vma->vm_start > haddr, vma); + VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); + VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd) + && !pmd_devmap(*pmd)); + + count_vm_event(THP_SPLIT_PMD); + + if (!vma_is_anonymous(vma)) { + old_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); + /* + * We are going to unmap this huge page. So + * just go ahead and zap it + */ + if (arch_needs_pgtable_deposit()) + zap_deposited_table(mm, pmd); + if (vma_is_special_huge(vma)) + return; + if (unlikely(is_pmd_migration_entry(old_pmd))) { + swp_entry_t entry; + + entry = pmd_to_swp_entry(old_pmd); + page = migration_entry_to_page(entry); + } else { + page = pmd_page(old_pmd); + if (!PageDirty(page) && pmd_dirty(old_pmd)) + set_page_dirty(page); + if (!PageReferenced(page) && pmd_young(old_pmd)) + SetPageReferenced(page); + page_remove_rmap(page, true); + put_page(page); + } + add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR); + return; + } + + if (is_huge_zero_pmd(*pmd)) { + /* + * FIXME: Do we want to invalidate secondary mmu by calling + * mmu_notifier_invalidate_range() see comments below inside + * __split_huge_pmd() ? + * + * We are going from a zero huge page write protected to zero + * small page also write protected so it does not seems useful + * to invalidate secondary mmu at this time. + */ + return __split_huge_zero_page_pmd(vma, haddr, pmd); + } + + /* + * Up to this point the pmd is present and huge and userland has the + * whole access to the hugepage during the split (which happens in + * place). If we overwrite the pmd with the not-huge version pointing + * to the pte here (which of course we could if all CPUs were bug + * free), userland could trigger a small page size TLB miss on the + * small sized TLB while the hugepage TLB entry is still established in + * the huge TLB. Some CPU doesn't like that. + * See http://support.amd.com/TechDocs/41322_10h_Rev_Gd.pdf, Erratum + * 383 on page 105. Intel should be safe but is also warns that it's + * only safe if the permission and cache attributes of the two entries + * loaded in the two TLB is identical (which should be the case here). + * But it is generally safer to never allow small and huge TLB entries + * for the same virtual address to be loaded simultaneously. So instead + * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the + * current pmd notpresent (atomically because here the pmd_trans_huge + * must remain set at all times on the pmd until the split is complete + * for this pmd), then we flush the SMP TLB and finally we write the + * non-huge version of the pmd entry with pmd_populate. + */ + old_pmd = pmdp_invalidate(vma, haddr, pmd); + + pmd_migration = is_pmd_migration_entry(old_pmd); + if (unlikely(pmd_migration)) { + swp_entry_t entry; + + entry = pmd_to_swp_entry(old_pmd); + page = migration_entry_to_page(entry); + write = is_write_migration_entry(entry); + young = false; + soft_dirty = pmd_swp_soft_dirty(old_pmd); + uffd_wp = pmd_swp_uffd_wp(old_pmd); + } else { + page = pmd_page(old_pmd); + if (pmd_dirty(old_pmd)) + SetPageDirty(page); + write = pmd_write(old_pmd); + young = pmd_young(old_pmd); + soft_dirty = pmd_soft_dirty(old_pmd); + uffd_wp = pmd_uffd_wp(old_pmd); + } + VM_BUG_ON_PAGE(!page_count(page), page); + page_ref_add(page, HPAGE_PMD_NR - 1); + + /* + * Withdraw the table only after we mark the pmd entry invalid. + * This's critical for some architectures (Power). + */ + pgtable = pgtable_trans_huge_withdraw(mm, pmd); + pmd_populate(mm, &_pmd, pgtable); + + for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { + pte_t entry, *pte; + /* + * Note that NUMA hinting access restrictions are not + * transferred to avoid any possibility of altering + * permissions across VMAs. + */ + if (freeze || pmd_migration) { + swp_entry_t swp_entry; + swp_entry = make_migration_entry(page + i, write); + entry = swp_entry_to_pte(swp_entry); + if (soft_dirty) + entry = pte_swp_mksoft_dirty(entry); + if (uffd_wp) + entry = pte_swp_mkuffd_wp(entry); + } else { + entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); + entry = maybe_mkwrite(entry, vma); + if (!write) + entry = pte_wrprotect(entry); + if (!young) + entry = pte_mkold(entry); + if (soft_dirty) + entry = pte_mksoft_dirty(entry); + if (uffd_wp) + entry = pte_mkuffd_wp(entry); + } + pte = pte_offset_map(&_pmd, addr); + BUG_ON(!pte_none(*pte)); + set_pte_at(mm, addr, pte, entry); + if (!pmd_migration) + atomic_inc(&page[i]._mapcount); + pte_unmap(pte); + } + + if (!pmd_migration) { + /* + * Set PG_double_map before dropping compound_mapcount to avoid + * false-negative page_mapped(). + */ + if (compound_mapcount(page) > 1 && + !TestSetPageDoubleMap(page)) { + for (i = 0; i < HPAGE_PMD_NR; i++) + atomic_inc(&page[i]._mapcount); + } + + lock_page_memcg(page); + if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { + /* Last compound_mapcount is gone. */ + __dec_lruvec_page_state(page, NR_ANON_THPS); + if (TestClearPageDoubleMap(page)) { + /* No need in mapcount reference anymore */ + for (i = 0; i < HPAGE_PMD_NR; i++) + atomic_dec(&page[i]._mapcount); + } + } + unlock_page_memcg(page); + } + + smp_wmb(); /* make pte visible before pmd */ + pmd_populate(mm, pmd, pgtable); + + if (freeze) { + for (i = 0; i < HPAGE_PMD_NR; i++) { + page_remove_rmap(page + i, false); + put_page(page + i); + } + } +} + +void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, + unsigned long address, bool freeze, struct page *page) +{ + spinlock_t *ptl; + struct mmu_notifier_range range; + bool do_unlock_page = false; + pmd_t _pmd; + + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, + address & HPAGE_PMD_MASK, + (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE); + mmu_notifier_invalidate_range_start(&range); + ptl = pmd_lock(vma->vm_mm, pmd); + + /* + * If caller asks to setup a migration entries, we need a page to check + * pmd against. Otherwise we can end up replacing wrong page. + */ + VM_BUG_ON(freeze && !page); + if (page) { + VM_WARN_ON_ONCE(!PageLocked(page)); + if (page != pmd_page(*pmd)) + goto out; + } + +repeat: + if (pmd_trans_huge(*pmd)) { + if (!page) { + page = pmd_page(*pmd); + /* + * An anonymous page must be locked, to ensure that a + * concurrent reuse_swap_page() sees stable mapcount; + * but reuse_swap_page() is not used on shmem or file, + * and page lock must not be taken when zap_pmd_range() + * calls __split_huge_pmd() while i_mmap_lock is held. + */ + if (PageAnon(page)) { + if (unlikely(!trylock_page(page))) { + get_page(page); + _pmd = *pmd; + spin_unlock(ptl); + lock_page(page); + spin_lock(ptl); + if (unlikely(!pmd_same(*pmd, _pmd))) { + unlock_page(page); + put_page(page); + page = NULL; + goto repeat; + } + put_page(page); + } + do_unlock_page = true; + } + } + if (PageMlocked(page)) + clear_page_mlock(page); + } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) + goto out; + __split_huge_pmd_locked(vma, pmd, range.start, freeze); +out: + spin_unlock(ptl); + if (do_unlock_page) + unlock_page(page); + /* + * No need to double call mmu_notifier->invalidate_range() callback. + * They are 3 cases to consider inside __split_huge_pmd_locked(): + * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious + * 2) __split_huge_zero_page_pmd() read only zero page and any write + * fault will trigger a flush_notify before pointing to a new page + * (it is fine if the secondary mmu keeps pointing to the old zero + * page in the meantime) + * 3) Split a huge pmd into pte pointing to the same page. No need + * to invalidate secondary tlb entry they are all still valid. + * any further changes to individual pte will notify. So no need + * to call mmu_notifier->invalidate_range() + */ + mmu_notifier_invalidate_range_only_end(&range); +} + +void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, + bool freeze, struct page *page) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + + pgd = pgd_offset(vma->vm_mm, address); + if (!pgd_present(*pgd)) + return; + + p4d = p4d_offset(pgd, address); + if (!p4d_present(*p4d)) + return; + + pud = pud_offset(p4d, address); + if (!pud_present(*pud)) + return; + + pmd = pmd_offset(pud, address); + + __split_huge_pmd(vma, pmd, address, freeze, page); +} + +void vma_adjust_trans_huge(struct vm_area_struct *vma, + unsigned long start, + unsigned long end, + long adjust_next) +{ + /* + * If the new start address isn't hpage aligned and it could + * previously contain an hugepage: check if we need to split + * an huge pmd. + */ + if (start & ~HPAGE_PMD_MASK && + (start & HPAGE_PMD_MASK) >= vma->vm_start && + (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) + split_huge_pmd_address(vma, start, false, NULL); + + /* + * If the new end address isn't hpage aligned and it could + * previously contain an hugepage: check if we need to split + * an huge pmd. + */ + if (end & ~HPAGE_PMD_MASK && + (end & HPAGE_PMD_MASK) >= vma->vm_start && + (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) + split_huge_pmd_address(vma, end, false, NULL); + + /* + * If we're also updating the vma->vm_next->vm_start, if the new + * vm_next->vm_start isn't hpage aligned and it could previously + * contain an hugepage: check if we need to split an huge pmd. + */ + if (adjust_next > 0) { + struct vm_area_struct *next = vma->vm_next; + unsigned long nstart = next->vm_start; + nstart += adjust_next; + if (nstart & ~HPAGE_PMD_MASK && + (nstart & HPAGE_PMD_MASK) >= next->vm_start && + (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) + split_huge_pmd_address(next, nstart, false, NULL); + } +} + +static void unmap_page(struct page *page) +{ + enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_SYNC | + TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; + + VM_BUG_ON_PAGE(!PageHead(page), page); + + if (PageAnon(page)) + ttu_flags |= TTU_SPLIT_FREEZE; + + try_to_unmap(page, ttu_flags); + + VM_WARN_ON_ONCE_PAGE(page_mapped(page), page); +} + +static void remap_page(struct page *page, unsigned int nr) +{ + int i; + if (PageTransHuge(page)) { + remove_migration_ptes(page, page, true); + } else { + for (i = 0; i < nr; i++) + remove_migration_ptes(page + i, page + i, true); + } +} + +static void __split_huge_page_tail(struct page *head, int tail, + struct lruvec *lruvec, struct list_head *list) +{ + struct page *page_tail = head + tail; + + VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); + + /* + * Clone page flags before unfreezing refcount. + * + * After successful get_page_unless_zero() might follow flags change, + * for exmaple lock_page() which set PG_waiters. + */ + page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; + page_tail->flags |= (head->flags & + ((1L << PG_referenced) | + (1L << PG_swapbacked) | + (1L << PG_swapcache) | + (1L << PG_mlocked) | + (1L << PG_uptodate) | + (1L << PG_active) | + (1L << PG_workingset) | + (1L << PG_locked) | + (1L << PG_unevictable) | +#ifdef CONFIG_64BIT + (1L << PG_arch_2) | +#endif + (1L << PG_dirty))); + + /* ->mapping in first tail page is compound_mapcount */ + VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, + page_tail); + page_tail->mapping = head->mapping; + page_tail->index = head->index + tail; + + /* Page flags must be visible before we make the page non-compound. */ + smp_wmb(); + + /* + * Clear PageTail before unfreezing page refcount. + * + * After successful get_page_unless_zero() might follow put_page() + * which needs correct compound_head(). + */ + clear_compound_head(page_tail); + + /* Finally unfreeze refcount. Additional reference from page cache. */ + page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) || + PageSwapCache(head))); + + if (page_is_young(head)) + set_page_young(page_tail); + if (page_is_idle(head)) + set_page_idle(page_tail); + + page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); + + /* + * always add to the tail because some iterators expect new + * pages to show after the currently processed elements - e.g. + * migrate_pages + */ + lru_add_page_tail(head, page_tail, lruvec, list); +} + +static void __split_huge_page(struct page *page, struct list_head *list, + pgoff_t end, unsigned long flags) +{ + struct page *head = compound_head(page); + pg_data_t *pgdat = page_pgdat(head); + struct lruvec *lruvec; + struct address_space *swap_cache = NULL; + unsigned long offset = 0; + unsigned int nr = thp_nr_pages(head); + int i; + + lruvec = mem_cgroup_page_lruvec(head, pgdat); + + /* complete memcg works before add pages to LRU */ + split_page_memcg(head, nr); + + if (PageAnon(head) && PageSwapCache(head)) { + swp_entry_t entry = { .val = page_private(head) }; + + offset = swp_offset(entry); + swap_cache = swap_address_space(entry); + xa_lock(&swap_cache->i_pages); + } + + for (i = nr - 1; i >= 1; i--) { + __split_huge_page_tail(head, i, lruvec, list); + /* Some pages can be beyond i_size: drop them from page cache */ + if (head[i].index >= end) { + ClearPageDirty(head + i); + __delete_from_page_cache(head + i, NULL); + if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head)) + shmem_uncharge(head->mapping->host, 1); + put_page(head + i); + } else if (!PageAnon(page)) { + __xa_store(&head->mapping->i_pages, head[i].index, + head + i, 0); + } else if (swap_cache) { + __xa_store(&swap_cache->i_pages, offset + i, + head + i, 0); + } + } + + ClearPageCompound(head); + + split_page_owner(head, nr); + + /* See comment in __split_huge_page_tail() */ + if (PageAnon(head)) { + /* Additional pin to swap cache */ + if (PageSwapCache(head)) { + page_ref_add(head, 2); + xa_unlock(&swap_cache->i_pages); + } else { + page_ref_inc(head); + } + } else { + /* Additional pin to page cache */ + page_ref_add(head, 2); + xa_unlock(&head->mapping->i_pages); + } + + spin_unlock_irqrestore(&pgdat->lru_lock, flags); + + remap_page(head, nr); + + if (PageSwapCache(head)) { + swp_entry_t entry = { .val = page_private(head) }; + + split_swap_cluster(entry); + } + + for (i = 0; i < nr; i++) { + struct page *subpage = head + i; + if (subpage == page) + continue; + unlock_page(subpage); + + /* + * Subpages may be freed if there wasn't any mapping + * like if add_to_swap() is running on a lru page that + * had its mapping zapped. And freeing these pages + * requires taking the lru_lock so we do the put_page + * of the tail pages after the split is complete. + */ + put_page(subpage); + } +} + +int total_mapcount(struct page *page) +{ + int i, compound, nr, ret; + + VM_BUG_ON_PAGE(PageTail(page), page); + + if (likely(!PageCompound(page))) + return atomic_read(&page->_mapcount) + 1; + + compound = compound_mapcount(page); + nr = compound_nr(page); + if (PageHuge(page)) + return compound; + ret = compound; + for (i = 0; i < nr; i++) + ret += atomic_read(&page[i]._mapcount) + 1; + /* File pages has compound_mapcount included in _mapcount */ + if (!PageAnon(page)) + return ret - compound * nr; + if (PageDoubleMap(page)) + ret -= nr; + return ret; +} + +/* + * This calculates accurately how many mappings a transparent hugepage + * has (unlike page_mapcount() which isn't fully accurate). This full + * accuracy is primarily needed to know if copy-on-write faults can + * reuse the page and change the mapping to read-write instead of + * copying them. At the same time this returns the total_mapcount too. + * + * The function returns the highest mapcount any one of the subpages + * has. If the return value is one, even if different processes are + * mapping different subpages of the transparent hugepage, they can + * all reuse it, because each process is reusing a different subpage. + * + * The total_mapcount is instead counting all virtual mappings of the + * subpages. If the total_mapcount is equal to "one", it tells the + * caller all mappings belong to the same "mm" and in turn the + * anon_vma of the transparent hugepage can become the vma->anon_vma + * local one as no other process may be mapping any of the subpages. + * + * It would be more accurate to replace page_mapcount() with + * page_trans_huge_mapcount(), however we only use + * page_trans_huge_mapcount() in the copy-on-write faults where we + * need full accuracy to avoid breaking page pinning, because + * page_trans_huge_mapcount() is slower than page_mapcount(). + */ +int page_trans_huge_mapcount(struct page *page, int *total_mapcount) +{ + int i, ret, _total_mapcount, mapcount; + + /* hugetlbfs shouldn't call it */ + VM_BUG_ON_PAGE(PageHuge(page), page); + + if (likely(!PageTransCompound(page))) { + mapcount = atomic_read(&page->_mapcount) + 1; + if (total_mapcount) + *total_mapcount = mapcount; + return mapcount; + } + + page = compound_head(page); + + _total_mapcount = ret = 0; + for (i = 0; i < thp_nr_pages(page); i++) { + mapcount = atomic_read(&page[i]._mapcount) + 1; + ret = max(ret, mapcount); + _total_mapcount += mapcount; + } + if (PageDoubleMap(page)) { + ret -= 1; + _total_mapcount -= thp_nr_pages(page); + } + mapcount = compound_mapcount(page); + ret += mapcount; + _total_mapcount += mapcount; + if (total_mapcount) + *total_mapcount = _total_mapcount; + return ret; +} + +/* Racy check whether the huge page can be split */ +bool can_split_huge_page(struct page *page, int *pextra_pins) +{ + int extra_pins; + + /* Additional pins from page cache */ + if (PageAnon(page)) + extra_pins = PageSwapCache(page) ? thp_nr_pages(page) : 0; + else + extra_pins = thp_nr_pages(page); + if (pextra_pins) + *pextra_pins = extra_pins; + return total_mapcount(page) == page_count(page) - extra_pins - 1; +} + +/* + * This function splits huge page into normal pages. @page can point to any + * subpage of huge page to split. Split doesn't change the position of @page. + * + * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. + * The huge page must be locked. + * + * If @list is null, tail pages will be added to LRU list, otherwise, to @list. + * + * Both head page and tail pages will inherit mapping, flags, and so on from + * the hugepage. + * + * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if + * they are not mapped. + * + * Returns 0 if the hugepage is split successfully. + * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under + * us. + */ +int split_huge_page_to_list(struct page *page, struct list_head *list) +{ + struct page *head = compound_head(page); + struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); + struct deferred_split *ds_queue = get_deferred_split_queue(head); + struct anon_vma *anon_vma = NULL; + struct address_space *mapping = NULL; + int extra_pins, ret; + unsigned long flags; + pgoff_t end; + + VM_BUG_ON_PAGE(is_huge_zero_page(head), head); + VM_BUG_ON_PAGE(!PageLocked(head), head); + VM_BUG_ON_PAGE(!PageCompound(head), head); + + if (PageWriteback(head)) + return -EBUSY; + + if (PageAnon(head)) { + /* + * The caller does not necessarily hold an mmap_lock that would + * prevent the anon_vma disappearing so we first we take a + * reference to it and then lock the anon_vma for write. This + * is similar to page_lock_anon_vma_read except the write lock + * is taken to serialise against parallel split or collapse + * operations. + */ + anon_vma = page_get_anon_vma(head); + if (!anon_vma) { + ret = -EBUSY; + goto out; + } + end = -1; + mapping = NULL; + anon_vma_lock_write(anon_vma); + } else { + mapping = head->mapping; + + /* Truncated ? */ + if (!mapping) { + ret = -EBUSY; + goto out; + } + + anon_vma = NULL; + i_mmap_lock_read(mapping); + + /* + *__split_huge_page() may need to trim off pages beyond EOF: + * but on 32-bit, i_size_read() takes an irq-unsafe seqlock, + * which cannot be nested inside the page tree lock. So note + * end now: i_size itself may be changed at any moment, but + * head page lock is good enough to serialize the trimming. + */ + end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); + } + + /* + * Racy check if we can split the page, before unmap_page() will + * split PMDs + */ + if (!can_split_huge_page(head, &extra_pins)) { + ret = -EBUSY; + goto out_unlock; + } + + unmap_page(head); + + /* prevent PageLRU to go away from under us, and freeze lru stats */ + spin_lock_irqsave(&pgdata->lru_lock, flags); + + if (mapping) { + XA_STATE(xas, &mapping->i_pages, page_index(head)); + + /* + * Check if the head page is present in page cache. + * We assume all tail are present too, if head is there. + */ + xa_lock(&mapping->i_pages); + if (xas_load(&xas) != head) + goto fail; + } + + /* Prevent deferred_split_scan() touching ->_refcount */ + spin_lock(&ds_queue->split_queue_lock); + if (page_ref_freeze(head, 1 + extra_pins)) { + if (!list_empty(page_deferred_list(head))) { + ds_queue->split_queue_len--; + list_del(page_deferred_list(head)); + } + spin_unlock(&ds_queue->split_queue_lock); + if (mapping) { + if (PageSwapBacked(head)) + __dec_node_page_state(head, NR_SHMEM_THPS); + else + __dec_node_page_state(head, NR_FILE_THPS); + } + + __split_huge_page(page, list, end, flags); + ret = 0; + } else { + spin_unlock(&ds_queue->split_queue_lock); +fail: + if (mapping) + xa_unlock(&mapping->i_pages); + spin_unlock_irqrestore(&pgdata->lru_lock, flags); + remap_page(head, thp_nr_pages(head)); + ret = -EBUSY; + } + +out_unlock: + if (anon_vma) { + anon_vma_unlock_write(anon_vma); + put_anon_vma(anon_vma); + } + if (mapping) + i_mmap_unlock_read(mapping); +out: + count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); + return ret; +} + +void free_transhuge_page(struct page *page) +{ + struct deferred_split *ds_queue = get_deferred_split_queue(page); + unsigned long flags; + + spin_lock_irqsave(&ds_queue->split_queue_lock, flags); + if (!list_empty(page_deferred_list(page))) { + ds_queue->split_queue_len--; + list_del(page_deferred_list(page)); + } + spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); + free_compound_page(page); +} + +void deferred_split_huge_page(struct page *page) +{ + struct deferred_split *ds_queue = get_deferred_split_queue(page); +#ifdef CONFIG_MEMCG + struct mem_cgroup *memcg = compound_head(page)->mem_cgroup; +#endif + unsigned long flags; + + VM_BUG_ON_PAGE(!PageTransHuge(page), page); + + /* + * The try_to_unmap() in page reclaim path might reach here too, + * this may cause a race condition to corrupt deferred split queue. + * And, if page reclaim is already handling the same page, it is + * unnecessary to handle it again in shrinker. + * + * Check PageSwapCache to determine if the page is being + * handled by page reclaim since THP swap would add the page into + * swap cache before calling try_to_unmap(). + */ + if (PageSwapCache(page)) + return; + + if (!list_empty(page_deferred_list(page))) + return; + + spin_lock_irqsave(&ds_queue->split_queue_lock, flags); + if (list_empty(page_deferred_list(page))) { + count_vm_event(THP_DEFERRED_SPLIT_PAGE); + list_add_tail(page_deferred_list(page), &ds_queue->split_queue); + ds_queue->split_queue_len++; +#ifdef CONFIG_MEMCG + if (memcg) + memcg_set_shrinker_bit(memcg, page_to_nid(page), + deferred_split_shrinker.id); +#endif + } + spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); +} + +static unsigned long deferred_split_count(struct shrinker *shrink, + struct shrink_control *sc) +{ + struct pglist_data *pgdata = NODE_DATA(sc->nid); + struct deferred_split *ds_queue = &pgdata->deferred_split_queue; + +#ifdef CONFIG_MEMCG + if (sc->memcg) + ds_queue = &sc->memcg->deferred_split_queue; +#endif + return READ_ONCE(ds_queue->split_queue_len); +} + +static unsigned long deferred_split_scan(struct shrinker *shrink, + struct shrink_control *sc) +{ + struct pglist_data *pgdata = NODE_DATA(sc->nid); + struct deferred_split *ds_queue = &pgdata->deferred_split_queue; + unsigned long flags; + LIST_HEAD(list), *pos, *next; + struct page *page; + int split = 0; + +#ifdef CONFIG_MEMCG + if (sc->memcg) + ds_queue = &sc->memcg->deferred_split_queue; +#endif + + spin_lock_irqsave(&ds_queue->split_queue_lock, flags); + /* Take pin on all head pages to avoid freeing them under us */ + list_for_each_safe(pos, next, &ds_queue->split_queue) { + page = list_entry((void *)pos, struct page, mapping); + page = compound_head(page); + if (get_page_unless_zero(page)) { + list_move(page_deferred_list(page), &list); + } else { + /* We lost race with put_compound_page() */ + list_del_init(page_deferred_list(page)); + ds_queue->split_queue_len--; + } + if (!--sc->nr_to_scan) + break; + } + spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); + + list_for_each_safe(pos, next, &list) { + page = list_entry((void *)pos, struct page, mapping); + if (!trylock_page(page)) + goto next; + /* split_huge_page() removes page from list on success */ + if (!split_huge_page(page)) + split++; + unlock_page(page); +next: + put_page(page); + } + + spin_lock_irqsave(&ds_queue->split_queue_lock, flags); + list_splice_tail(&list, &ds_queue->split_queue); + spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); + + /* + * Stop shrinker if we didn't split any page, but the queue is empty. + * This can happen if pages were freed under us. + */ + if (!split && list_empty(&ds_queue->split_queue)) + return SHRINK_STOP; + return split; +} + +static struct shrinker deferred_split_shrinker = { + .count_objects = deferred_split_count, + .scan_objects = deferred_split_scan, + .seeks = DEFAULT_SEEKS, + .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE | + SHRINKER_NONSLAB, +}; + +#ifdef CONFIG_DEBUG_FS +static int split_huge_pages_set(void *data, u64 val) +{ + struct zone *zone; + struct page *page; + unsigned long pfn, max_zone_pfn; + unsigned long total = 0, split = 0; + + if (val != 1) + return -EINVAL; + + for_each_populated_zone(zone) { + max_zone_pfn = zone_end_pfn(zone); + for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { + if (!pfn_valid(pfn)) + continue; + + page = pfn_to_page(pfn); + if (!get_page_unless_zero(page)) + continue; + + if (zone != page_zone(page)) + goto next; + + if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) + goto next; + + total++; + lock_page(page); + if (!split_huge_page(page)) + split++; + unlock_page(page); +next: + put_page(page); + } + } + + pr_info("%lu of %lu THP split\n", split, total); + + return 0; +} +DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, + "%llu\n"); + +static int __init split_huge_pages_debugfs(void) +{ + debugfs_create_file("split_huge_pages", 0200, NULL, NULL, + &split_huge_pages_fops); + return 0; +} +late_initcall(split_huge_pages_debugfs); +#endif + +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION +void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, + struct page *page) +{ + struct vm_area_struct *vma = pvmw->vma; + struct mm_struct *mm = vma->vm_mm; + unsigned long address = pvmw->address; + pmd_t pmdval; + swp_entry_t entry; + pmd_t pmdswp; + + if (!(pvmw->pmd && !pvmw->pte)) + return; + + flush_cache_range(vma, address, address + HPAGE_PMD_SIZE); + pmdval = pmdp_invalidate(vma, address, pvmw->pmd); + if (pmd_dirty(pmdval)) + set_page_dirty(page); + entry = make_migration_entry(page, pmd_write(pmdval)); + pmdswp = swp_entry_to_pmd(entry); + if (pmd_soft_dirty(pmdval)) + pmdswp = pmd_swp_mksoft_dirty(pmdswp); + set_pmd_at(mm, address, pvmw->pmd, pmdswp); + page_remove_rmap(page, true); + put_page(page); +} + +void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) +{ + struct vm_area_struct *vma = pvmw->vma; + struct mm_struct *mm = vma->vm_mm; + unsigned long address = pvmw->address; + unsigned long mmun_start = address & HPAGE_PMD_MASK; + pmd_t pmde; + swp_entry_t entry; + + if (!(pvmw->pmd && !pvmw->pte)) + return; + + entry = pmd_to_swp_entry(*pvmw->pmd); + get_page(new); + pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot)); + if (pmd_swp_soft_dirty(*pvmw->pmd)) + pmde = pmd_mksoft_dirty(pmde); + if (is_write_migration_entry(entry)) + pmde = maybe_pmd_mkwrite(pmde, vma); + if (pmd_swp_uffd_wp(*pvmw->pmd)) + pmde = pmd_wrprotect(pmd_mkuffd_wp(pmde)); + + flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE); + if (PageAnon(new)) + page_add_anon_rmap(new, vma, mmun_start, true); + else + page_add_file_rmap(new, true); + set_pmd_at(mm, mmun_start, pvmw->pmd, pmde); + if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new)) + mlock_vma_page(new); + update_mmu_cache_pmd(vma, address, pvmw->pmd); +} +#endif |