diff options
Diffstat (limited to 'kernel/mm/huge_memory.c')
| -rw-r--r-- | kernel/mm/huge_memory.c | 3011 |
1 files changed, 3011 insertions, 0 deletions
diff --git a/kernel/mm/huge_memory.c b/kernel/mm/huge_memory.c new file mode 100644 index 000000000..078832cf3 --- /dev/null +++ b/kernel/mm/huge_memory.c @@ -0,0 +1,3011 @@ +/* + * Copyright (C) 2009 Red Hat, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/mm.h> +#include <linux/sched.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/kthread.h> +#include <linux/khugepaged.h> +#include <linux/freezer.h> +#include <linux/mman.h> +#include <linux/pagemap.h> +#include <linux/migrate.h> +#include <linux/hashtable.h> + +#include <asm/tlb.h> +#include <asm/pgalloc.h> +#include "internal.h" + +/* + * By default transparent hugepage support is disabled in order that avoid + * to risk increase the memory footprint of applications without a guaranteed + * benefit. When transparent hugepage support is enabled, 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_FLAG)| + (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| + (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); + +/* default scan 8*512 pte (or vmas) every 30 second */ +static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; +static unsigned int khugepaged_pages_collapsed; +static unsigned int khugepaged_full_scans; +static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; +/* during fragmentation poll the hugepage allocator once every minute */ +static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; +static struct task_struct *khugepaged_thread __read_mostly; +static DEFINE_MUTEX(khugepaged_mutex); +static DEFINE_SPINLOCK(khugepaged_mm_lock); +static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); +/* + * default collapse hugepages if there is at least one pte mapped like + * it would have happened if the vma was large enough during page + * fault. + */ +static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; + +static int khugepaged(void *none); +static int khugepaged_slab_init(void); +static void khugepaged_slab_exit(void); + +#define MM_SLOTS_HASH_BITS 10 +static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); + +static struct kmem_cache *mm_slot_cache __read_mostly; + +/** + * struct mm_slot - hash lookup from mm to mm_slot + * @hash: hash collision list + * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head + * @mm: the mm that this information is valid for + */ +struct mm_slot { + struct hlist_node hash; + struct list_head mm_node; + struct mm_struct *mm; +}; + +/** + * struct khugepaged_scan - cursor for scanning + * @mm_head: the head of the mm list to scan + * @mm_slot: the current mm_slot we are scanning + * @address: the next address inside that to be scanned + * + * There is only the one khugepaged_scan instance of this cursor structure. + */ +struct khugepaged_scan { + struct list_head mm_head; + struct mm_slot *mm_slot; + unsigned long address; +}; +static struct khugepaged_scan khugepaged_scan = { + .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), +}; + + +static int set_recommended_min_free_kbytes(void) +{ + struct zone *zone; + int nr_zones = 0; + unsigned long recommended_min; + + for_each_populated_zone(zone) + nr_zones++; + + /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */ + recommended_min = pageblock_nr_pages * nr_zones * 2; + + /* + * Make sure that on average at least two pageblocks are almost free + * of another type, one for a migratetype to fall back to and a + * second to avoid subsequent fallbacks of other types There are 3 + * MIGRATE_TYPES we care about. + */ + recommended_min += pageblock_nr_pages * nr_zones * + MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; + + /* don't ever allow to reserve more than 5% of the lowmem */ + recommended_min = min(recommended_min, + (unsigned long) nr_free_buffer_pages() / 20); + recommended_min <<= (PAGE_SHIFT-10); + + if (recommended_min > min_free_kbytes) { + if (user_min_free_kbytes >= 0) + pr_info("raising min_free_kbytes from %d to %lu " + "to help transparent hugepage allocations\n", + min_free_kbytes, recommended_min); + + min_free_kbytes = recommended_min; + } + setup_per_zone_wmarks(); + return 0; +} + +static int start_stop_khugepaged(void) +{ + int err = 0; + if (khugepaged_enabled()) { + if (!khugepaged_thread) + khugepaged_thread = kthread_run(khugepaged, NULL, + "khugepaged"); + if (unlikely(IS_ERR(khugepaged_thread))) { + pr_err("khugepaged: kthread_run(khugepaged) failed\n"); + err = PTR_ERR(khugepaged_thread); + khugepaged_thread = NULL; + goto fail; + } + + if (!list_empty(&khugepaged_scan.mm_head)) + wake_up_interruptible(&khugepaged_wait); + + set_recommended_min_free_kbytes(); + } else if (khugepaged_thread) { + kthread_stop(khugepaged_thread); + khugepaged_thread = NULL; + } +fail: + return err; +} + +static atomic_t huge_zero_refcount; +struct page *huge_zero_page __read_mostly; + +static inline bool is_huge_zero_pmd(pmd_t pmd) +{ + return is_huge_zero_page(pmd_page(pmd)); +} + +static struct page *get_huge_zero_page(void) +{ + struct page *zero_page; +retry: + if (likely(atomic_inc_not_zero(&huge_zero_refcount))) + return READ_ONCE(huge_zero_page); + + zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, + HPAGE_PMD_ORDER); + if (!zero_page) { + count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); + return NULL; + } + count_vm_event(THP_ZERO_PAGE_ALLOC); + preempt_disable(); + if (cmpxchg(&huge_zero_page, NULL, zero_page)) { + preempt_enable(); + __free_pages(zero_page, compound_order(zero_page)); + goto retry; + } + + /* We take additional reference here. It will be put back by shrinker */ + atomic_set(&huge_zero_refcount, 2); + preempt_enable(); + return READ_ONCE(huge_zero_page); +} + +static void put_huge_zero_page(void) +{ + /* + * Counter should never go to zero here. Only shrinker can put + * last reference. + */ + BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); +} + +static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, + struct shrink_control *sc) +{ + /* we can free zero page only if last reference remains */ + return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; +} + +static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, + struct shrink_control *sc) +{ + if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { + struct page *zero_page = xchg(&huge_zero_page, NULL); + BUG_ON(zero_page == NULL); + __free_pages(zero_page, compound_order(zero_page)); + return HPAGE_PMD_NR; + } + + return 0; +} + +static struct shrinker huge_zero_page_shrinker = { + .count_objects = shrink_huge_zero_page_count, + .scan_objects = shrink_huge_zero_page_scan, + .seeks = DEFAULT_SEEKS, +}; + +#ifdef CONFIG_SYSFS + +static ssize_t double_flag_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf, + enum transparent_hugepage_flag enabled, + enum transparent_hugepage_flag req_madv) +{ + if (test_bit(enabled, &transparent_hugepage_flags)) { + VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); + return sprintf(buf, "[always] madvise never\n"); + } else if (test_bit(req_madv, &transparent_hugepage_flags)) + return sprintf(buf, "always [madvise] never\n"); + else + return sprintf(buf, "always madvise [never]\n"); +} +static ssize_t double_flag_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count, + enum transparent_hugepage_flag enabled, + enum transparent_hugepage_flag req_madv) +{ + if (!memcmp("always", buf, + min(sizeof("always")-1, count))) { + set_bit(enabled, &transparent_hugepage_flags); + clear_bit(req_madv, &transparent_hugepage_flags); + } else if (!memcmp("madvise", buf, + min(sizeof("madvise")-1, count))) { + clear_bit(enabled, &transparent_hugepage_flags); + set_bit(req_madv, &transparent_hugepage_flags); + } else if (!memcmp("never", buf, + min(sizeof("never")-1, count))) { + clear_bit(enabled, &transparent_hugepage_flags); + clear_bit(req_madv, &transparent_hugepage_flags); + } else + return -EINVAL; + + return count; +} + +static ssize_t enabled_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return double_flag_show(kobj, attr, buf, + TRANSPARENT_HUGEPAGE_FLAG, + TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); +} +static ssize_t enabled_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + ssize_t ret; + + ret = double_flag_store(kobj, attr, buf, count, + TRANSPARENT_HUGEPAGE_FLAG, + TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); + + if (ret > 0) { + int err; + + mutex_lock(&khugepaged_mutex); + err = start_stop_khugepaged(); + mutex_unlock(&khugepaged_mutex); + + if (err) + ret = err; + } + + return ret; +} +static struct kobj_attribute enabled_attr = + __ATTR(enabled, 0644, enabled_show, enabled_store); + +static ssize_t single_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)); +} + +static ssize_t single_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; +} + +/* + * Currently defrag only disables __GFP_NOWAIT for allocation. A blind + * __GFP_REPEAT is too aggressive, it's never worth swapping tons of + * memory just to allocate one more hugepage. + */ +static ssize_t defrag_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return double_flag_show(kobj, attr, buf, + TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, + TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); +} +static ssize_t defrag_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + return double_flag_store(kobj, attr, buf, count, + TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, + TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); +} +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_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_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); +#ifdef CONFIG_DEBUG_VM +static ssize_t debug_cow_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return single_flag_show(kobj, attr, buf, + TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); +} +static ssize_t debug_cow_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + return single_flag_store(kobj, attr, buf, count, + TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); +} +static struct kobj_attribute debug_cow_attr = + __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); +#endif /* CONFIG_DEBUG_VM */ + +static struct attribute *hugepage_attr[] = { + &enabled_attr.attr, + &defrag_attr.attr, + &use_zero_page_attr.attr, +#ifdef CONFIG_DEBUG_VM + &debug_cow_attr.attr, +#endif + NULL, +}; + +static struct attribute_group hugepage_attr_group = { + .attrs = hugepage_attr, +}; + +static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); +} + +static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned long msecs; + int err; + + err = kstrtoul(buf, 10, &msecs); + if (err || msecs > UINT_MAX) + return -EINVAL; + + khugepaged_scan_sleep_millisecs = msecs; + wake_up_interruptible(&khugepaged_wait); + + return count; +} +static struct kobj_attribute scan_sleep_millisecs_attr = + __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, + scan_sleep_millisecs_store); + +static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); +} + +static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + unsigned long msecs; + int err; + + err = kstrtoul(buf, 10, &msecs); + if (err || msecs > UINT_MAX) + return -EINVAL; + + khugepaged_alloc_sleep_millisecs = msecs; + wake_up_interruptible(&khugepaged_wait); + + return count; +} +static struct kobj_attribute alloc_sleep_millisecs_attr = + __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, + alloc_sleep_millisecs_store); + +static ssize_t pages_to_scan_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", khugepaged_pages_to_scan); +} +static ssize_t pages_to_scan_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long pages; + + err = kstrtoul(buf, 10, &pages); + if (err || !pages || pages > UINT_MAX) + return -EINVAL; + + khugepaged_pages_to_scan = pages; + + return count; +} +static struct kobj_attribute pages_to_scan_attr = + __ATTR(pages_to_scan, 0644, pages_to_scan_show, + pages_to_scan_store); + +static ssize_t pages_collapsed_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", khugepaged_pages_collapsed); +} +static struct kobj_attribute pages_collapsed_attr = + __ATTR_RO(pages_collapsed); + +static ssize_t full_scans_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", khugepaged_full_scans); +} +static struct kobj_attribute full_scans_attr = + __ATTR_RO(full_scans); + +static ssize_t khugepaged_defrag_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return single_flag_show(kobj, attr, buf, + TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); +} +static ssize_t khugepaged_defrag_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + return single_flag_store(kobj, attr, buf, count, + TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); +} +static struct kobj_attribute khugepaged_defrag_attr = + __ATTR(defrag, 0644, khugepaged_defrag_show, + khugepaged_defrag_store); + +/* + * max_ptes_none controls if khugepaged should collapse hugepages over + * any unmapped ptes in turn potentially increasing the memory + * footprint of the vmas. When max_ptes_none is 0 khugepaged will not + * reduce the available free memory in the system as it + * runs. Increasing max_ptes_none will instead potentially reduce the + * free memory in the system during the khugepaged scan. + */ +static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) +{ + return sprintf(buf, "%u\n", khugepaged_max_ptes_none); +} +static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + int err; + unsigned long max_ptes_none; + + err = kstrtoul(buf, 10, &max_ptes_none); + if (err || max_ptes_none > HPAGE_PMD_NR-1) + return -EINVAL; + + khugepaged_max_ptes_none = max_ptes_none; + + return count; +} +static struct kobj_attribute khugepaged_max_ptes_none_attr = + __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, + khugepaged_max_ptes_none_store); + +static struct attribute *khugepaged_attr[] = { + &khugepaged_defrag_attr.attr, + &khugepaged_max_ptes_none_attr.attr, + &pages_to_scan_attr.attr, + &pages_collapsed_attr.attr, + &full_scans_attr.attr, + &scan_sleep_millisecs_attr.attr, + &alloc_sleep_millisecs_attr.attr, + NULL, +}; + +static struct attribute_group khugepaged_attr_group = { + .attrs = khugepaged_attr, + .name = "khugepaged", +}; + +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()) { + transparent_hugepage_flags = 0; + return -EINVAL; + } + + err = hugepage_init_sysfs(&hugepage_kobj); + if (err) + goto err_sysfs; + + err = khugepaged_slab_init(); + if (err) + goto err_slab; + + err = register_shrinker(&huge_zero_page_shrinker); + if (err) + goto err_hzp_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(&huge_zero_page_shrinker); +err_hzp_shrinker: + khugepaged_slab_exit(); +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; +} + +static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot) +{ + pmd_t entry; + entry = mk_pmd(page, prot); + entry = pmd_mkhuge(entry); + return entry; +} + +static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, + struct vm_area_struct *vma, + unsigned long haddr, pmd_t *pmd, + struct page *page, gfp_t gfp) +{ + struct mem_cgroup *memcg; + pgtable_t pgtable; + spinlock_t *ptl; + + VM_BUG_ON_PAGE(!PageCompound(page), page); + + if (mem_cgroup_try_charge(page, mm, gfp, &memcg)) + return VM_FAULT_OOM; + + pgtable = pte_alloc_one(mm, haddr); + if (unlikely(!pgtable)) { + mem_cgroup_cancel_charge(page, memcg); + return VM_FAULT_OOM; + } + + clear_huge_page(page, haddr, 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); + + ptl = pmd_lock(mm, pmd); + if (unlikely(!pmd_none(*pmd))) { + spin_unlock(ptl); + mem_cgroup_cancel_charge(page, memcg); + put_page(page); + pte_free(mm, pgtable); + } else { + pmd_t entry; + 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); + mem_cgroup_commit_charge(page, memcg, false); + lru_cache_add_active_or_unevictable(page, vma); + pgtable_trans_huge_deposit(mm, pmd, pgtable); + set_pmd_at(mm, haddr, pmd, entry); + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); + atomic_long_inc(&mm->nr_ptes); + spin_unlock(ptl); + } + + return 0; +} + +static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) +{ + return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; +} + +/* 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); + pgtable_trans_huge_deposit(mm, pmd, pgtable); + set_pmd_at(mm, haddr, pmd, entry); + atomic_long_inc(&mm->nr_ptes); + return true; +} + +int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd, + unsigned int flags) +{ + gfp_t gfp; + struct page *page; + unsigned long haddr = address & HPAGE_PMD_MASK; + + if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) + 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 (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) && + transparent_hugepage_use_zero_page()) { + spinlock_t *ptl; + pgtable_t pgtable; + struct page *zero_page; + bool set; + pgtable = pte_alloc_one(mm, haddr); + if (unlikely(!pgtable)) + return VM_FAULT_OOM; + zero_page = get_huge_zero_page(); + if (unlikely(!zero_page)) { + pte_free(mm, pgtable); + count_vm_event(THP_FAULT_FALLBACK); + return VM_FAULT_FALLBACK; + } + ptl = pmd_lock(mm, pmd); + set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, + zero_page); + spin_unlock(ptl); + if (!set) { + pte_free(mm, pgtable); + put_huge_zero_page(); + } + return 0; + } + gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0); + page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); + if (unlikely(!page)) { + count_vm_event(THP_FAULT_FALLBACK); + return VM_FAULT_FALLBACK; + } + if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page, gfp))) { + put_page(page); + count_vm_event(THP_FAULT_FALLBACK); + return VM_FAULT_FALLBACK; + } + + count_vm_event(THP_FAULT_ALLOC); + return 0; +} + +int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, + pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, + struct vm_area_struct *vma) +{ + spinlock_t *dst_ptl, *src_ptl; + struct page *src_page; + pmd_t pmd; + pgtable_t pgtable; + int ret; + + ret = -ENOMEM; + pgtable = pte_alloc_one(dst_mm, addr); + 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; + if (unlikely(!pmd_trans_huge(pmd))) { + pte_free(dst_mm, pgtable); + goto out_unlock; + } + /* + * When page table lock is held, the huge zero pmd should not be + * under splitting since we don't split the page itself, only pmd to + * a page table. + */ + if (is_huge_zero_pmd(pmd)) { + struct page *zero_page; + bool set; + /* + * get_huge_zero_page() will never allocate a new page here, + * since we already have a zero page to copy. It just takes a + * reference. + */ + zero_page = get_huge_zero_page(); + set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, + zero_page); + BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ + ret = 0; + goto out_unlock; + } + + if (unlikely(pmd_trans_splitting(pmd))) { + /* split huge page running from under us */ + spin_unlock(src_ptl); + spin_unlock(dst_ptl); + pte_free(dst_mm, pgtable); + + wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ + goto out; + } + src_page = pmd_page(pmd); + VM_BUG_ON_PAGE(!PageHead(src_page), src_page); + get_page(src_page); + page_dup_rmap(src_page); + add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); + + pmdp_set_wrprotect(src_mm, addr, src_pmd); + pmd = pmd_mkold(pmd_wrprotect(pmd)); + pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); + set_pmd_at(dst_mm, addr, dst_pmd, pmd); + atomic_long_inc(&dst_mm->nr_ptes); + + ret = 0; +out_unlock: + spin_unlock(src_ptl); + spin_unlock(dst_ptl); +out: + return ret; +} + +void huge_pmd_set_accessed(struct mm_struct *mm, + struct vm_area_struct *vma, + unsigned long address, + pmd_t *pmd, pmd_t orig_pmd, + int dirty) +{ + spinlock_t *ptl; + pmd_t entry; + unsigned long haddr; + + ptl = pmd_lock(mm, pmd); + if (unlikely(!pmd_same(*pmd, orig_pmd))) + goto unlock; + + entry = pmd_mkyoung(orig_pmd); + haddr = address & HPAGE_PMD_MASK; + if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) + update_mmu_cache_pmd(vma, address, pmd); + +unlock: + spin_unlock(ptl); +} + +/* + * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages + * during copy_user_huge_page()'s copy_page_rep(): in the case when + * the source page gets split and a tail freed before copy completes. + * Called under pmd_lock of checked pmd, so safe from splitting itself. + */ +static void get_user_huge_page(struct page *page) +{ + if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { + struct page *endpage = page + HPAGE_PMD_NR; + + atomic_add(HPAGE_PMD_NR, &page->_count); + while (++page < endpage) + get_huge_page_tail(page); + } else { + get_page(page); + } +} + +static void put_user_huge_page(struct page *page) +{ + if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { + struct page *endpage = page + HPAGE_PMD_NR; + + while (page < endpage) + put_page(page++); + } else { + put_page(page); + } +} + +static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, + struct vm_area_struct *vma, + unsigned long address, + pmd_t *pmd, pmd_t orig_pmd, + struct page *page, + unsigned long haddr) +{ + struct mem_cgroup *memcg; + spinlock_t *ptl; + pgtable_t pgtable; + pmd_t _pmd; + int ret = 0, i; + struct page **pages; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ + + pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, + GFP_KERNEL); + if (unlikely(!pages)) { + ret |= VM_FAULT_OOM; + goto out; + } + + for (i = 0; i < HPAGE_PMD_NR; i++) { + pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | + __GFP_OTHER_NODE, + vma, address, page_to_nid(page)); + if (unlikely(!pages[i] || + mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL, + &memcg))) { + if (pages[i]) + put_page(pages[i]); + while (--i >= 0) { + memcg = (void *)page_private(pages[i]); + set_page_private(pages[i], 0); + mem_cgroup_cancel_charge(pages[i], memcg); + put_page(pages[i]); + } + kfree(pages); + ret |= VM_FAULT_OOM; + goto out; + } + set_page_private(pages[i], (unsigned long)memcg); + } + + for (i = 0; i < HPAGE_PMD_NR; i++) { + copy_user_highpage(pages[i], page + i, + haddr + PAGE_SIZE * i, vma); + __SetPageUptodate(pages[i]); + cond_resched(); + } + + mmun_start = haddr; + mmun_end = haddr + HPAGE_PMD_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + + ptl = pmd_lock(mm, pmd); + if (unlikely(!pmd_same(*pmd, orig_pmd))) + goto out_free_pages; + VM_BUG_ON_PAGE(!PageHead(page), page); + + pmdp_clear_flush_notify(vma, haddr, pmd); + /* leave pmd empty until pte is filled */ + + 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 = mk_pte(pages[i], vma->vm_page_prot); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + memcg = (void *)page_private(pages[i]); + set_page_private(pages[i], 0); + page_add_new_anon_rmap(pages[i], vma, haddr); + mem_cgroup_commit_charge(pages[i], memcg, false); + lru_cache_add_active_or_unevictable(pages[i], vma); + pte = pte_offset_map(&_pmd, haddr); + VM_BUG_ON(!pte_none(*pte)); + set_pte_at(mm, haddr, pte, entry); + pte_unmap(pte); + } + kfree(pages); + + smp_wmb(); /* make pte visible before pmd */ + pmd_populate(mm, pmd, pgtable); + page_remove_rmap(page); + spin_unlock(ptl); + + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + + ret |= VM_FAULT_WRITE; + put_page(page); + +out: + return ret; + +out_free_pages: + spin_unlock(ptl); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + for (i = 0; i < HPAGE_PMD_NR; i++) { + memcg = (void *)page_private(pages[i]); + set_page_private(pages[i], 0); + mem_cgroup_cancel_charge(pages[i], memcg); + put_page(pages[i]); + } + kfree(pages); + goto out; +} + +int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd, pmd_t orig_pmd) +{ + spinlock_t *ptl; + int ret = 0; + struct page *page = NULL, *new_page; + struct mem_cgroup *memcg; + unsigned long haddr; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ + gfp_t huge_gfp; /* for allocation and charge */ + + ptl = pmd_lockptr(mm, pmd); + VM_BUG_ON_VMA(!vma->anon_vma, vma); + haddr = address & HPAGE_PMD_MASK; + if (is_huge_zero_pmd(orig_pmd)) + goto alloc; + spin_lock(ptl); + if (unlikely(!pmd_same(*pmd, orig_pmd))) + goto out_unlock; + + page = pmd_page(orig_pmd); + VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); + if (page_mapcount(page) == 1) { + pmd_t entry; + entry = pmd_mkyoung(orig_pmd); + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) + update_mmu_cache_pmd(vma, address, pmd); + ret |= VM_FAULT_WRITE; + goto out_unlock; + } + get_user_huge_page(page); + spin_unlock(ptl); +alloc: + if (transparent_hugepage_enabled(vma) && + !transparent_hugepage_debug_cow()) { + huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0); + new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); + } else + new_page = NULL; + + if (unlikely(!new_page)) { + if (!page) { + split_huge_page_pmd(vma, address, pmd); + ret |= VM_FAULT_FALLBACK; + } else { + ret = do_huge_pmd_wp_page_fallback(mm, vma, address, + pmd, orig_pmd, page, haddr); + if (ret & VM_FAULT_OOM) { + split_huge_page(page); + ret |= VM_FAULT_FALLBACK; + } + put_user_huge_page(page); + } + count_vm_event(THP_FAULT_FALLBACK); + goto out; + } + + if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg))) { + put_page(new_page); + if (page) { + split_huge_page(page); + put_user_huge_page(page); + } else + split_huge_page_pmd(vma, address, pmd); + ret |= VM_FAULT_FALLBACK; + count_vm_event(THP_FAULT_FALLBACK); + goto out; + } + + count_vm_event(THP_FAULT_ALLOC); + + if (!page) + clear_huge_page(new_page, haddr, HPAGE_PMD_NR); + else + copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); + __SetPageUptodate(new_page); + + mmun_start = haddr; + mmun_end = haddr + HPAGE_PMD_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + + spin_lock(ptl); + if (page) + put_user_huge_page(page); + if (unlikely(!pmd_same(*pmd, orig_pmd))) { + spin_unlock(ptl); + mem_cgroup_cancel_charge(new_page, memcg); + put_page(new_page); + goto out_mn; + } else { + pmd_t entry; + entry = mk_huge_pmd(new_page, vma->vm_page_prot); + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + pmdp_clear_flush_notify(vma, haddr, pmd); + page_add_new_anon_rmap(new_page, vma, haddr); + mem_cgroup_commit_charge(new_page, memcg, false); + lru_cache_add_active_or_unevictable(new_page, vma); + set_pmd_at(mm, haddr, pmd, entry); + update_mmu_cache_pmd(vma, address, pmd); + if (!page) { + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); + put_huge_zero_page(); + } else { + VM_BUG_ON_PAGE(!PageHead(page), page); + page_remove_rmap(page); + put_page(page); + } + ret |= VM_FAULT_WRITE; + } + spin_unlock(ptl); +out_mn: + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); +out: + return ret; +out_unlock: + spin_unlock(ptl); + return ret; +} + +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 && !pmd_write(*pmd)) + 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), page); + if (flags & FOLL_TOUCH) { + pmd_t _pmd; + /* + * We should set the dirty bit only for FOLL_WRITE but + * for now the dirty bit in the pmd is meaningless. + * And if the dirty bit will become meaningful and + * we'll only set it with FOLL_WRITE, an atomic + * set_bit will be required on the pmd to set the + * young bit, instead of the current set_pmd_at. + */ + _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); + if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, + pmd, _pmd, 1)) + update_mmu_cache_pmd(vma, addr, pmd); + } + if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) { + if (page->mapping && trylock_page(page)) { + lru_add_drain(); + if (page->mapping) + mlock_vma_page(page); + unlock_page(page); + } + } + page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; + VM_BUG_ON_PAGE(!PageCompound(page), page); + if (flags & FOLL_GET) + get_page_foll(page); + +out: + return page; +} + +/* NUMA hinting page fault entry point for trans huge pmds */ +int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long addr, pmd_t pmd, pmd_t *pmdp) +{ + spinlock_t *ptl; + struct anon_vma *anon_vma = NULL; + struct page *page; + unsigned long haddr = addr & HPAGE_PMD_MASK; + int page_nid = -1, this_nid = numa_node_id(); + int target_nid, last_cpupid = -1; + bool page_locked; + bool migrated = false; + bool was_writable; + int flags = 0; + + /* A PROT_NONE fault should not end up here */ + BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))); + + ptl = pmd_lock(mm, pmdp); + if (unlikely(!pmd_same(pmd, *pmdp))) + 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(*pmdp))) { + page = pmd_page(*pmdp); + spin_unlock(ptl); + 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 (!(vma->vm_flags & VM_WRITE)) + 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 == -1) { + /* 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) { + spin_unlock(ptl); + wait_on_page_locked(page); + page_nid = -1; + goto out; + } + + /* + * Page is misplaced. Page lock serialises migrations. Acquire anon_vma + * to serialises splits + */ + get_page(page); + spin_unlock(ptl); + anon_vma = page_lock_anon_vma_read(page); + + /* Confirm the PMD did not change while page_table_lock was released */ + spin_lock(ptl); + if (unlikely(!pmd_same(pmd, *pmdp))) { + unlock_page(page); + put_page(page); + page_nid = -1; + goto out_unlock; + } + + /* Bail if we fail to protect against THP splits for any reason */ + if (unlikely(!anon_vma)) { + put_page(page); + page_nid = -1; + goto clear_pmdnuma; + } + + /* + * Migrate the THP to the requested node, returns with page unlocked + * and access rights restored. + */ + spin_unlock(ptl); + migrated = migrate_misplaced_transhuge_page(mm, vma, + pmdp, pmd, addr, 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_write(pmd); + pmd = pmd_modify(pmd, vma->vm_page_prot); + pmd = pmd_mkyoung(pmd); + if (was_writable) + pmd = pmd_mkwrite(pmd); + set_pmd_at(mm, haddr, pmdp, pmd); + update_mmu_cache_pmd(vma, addr, pmdp); + unlock_page(page); +out_unlock: + spin_unlock(ptl); + +out: + if (anon_vma) + page_unlock_anon_vma_read(anon_vma); + + if (page_nid != -1) + task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags); + + return 0; +} + +int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, + pmd_t *pmd, unsigned long addr) +{ + spinlock_t *ptl; + int ret = 0; + + if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { + struct page *page; + pgtable_t pgtable; + pmd_t orig_pmd; + /* + * For architectures like ppc64 we look at deposited pgtable + * when calling pmdp_get_and_clear. So do the + * pgtable_trans_huge_withdraw after finishing pmdp related + * operations. + */ + orig_pmd = pmdp_get_and_clear_full(tlb->mm, addr, pmd, + tlb->fullmm); + tlb_remove_pmd_tlb_entry(tlb, pmd, addr); + pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd); + if (is_huge_zero_pmd(orig_pmd)) { + atomic_long_dec(&tlb->mm->nr_ptes); + spin_unlock(ptl); + put_huge_zero_page(); + } else { + page = pmd_page(orig_pmd); + page_remove_rmap(page); + VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); + add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); + VM_BUG_ON_PAGE(!PageHead(page), page); + atomic_long_dec(&tlb->mm->nr_ptes); + spin_unlock(ptl); + tlb_remove_page(tlb, page); + } + pte_free(tlb->mm, pgtable); + ret = 1; + } + return ret; +} + +int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, + unsigned long old_addr, + unsigned long new_addr, unsigned long old_end, + pmd_t *old_pmd, pmd_t *new_pmd) +{ + spinlock_t *old_ptl, *new_ptl; + int ret = 0; + pmd_t pmd; + + struct mm_struct *mm = vma->vm_mm; + + if ((old_addr & ~HPAGE_PMD_MASK) || + (new_addr & ~HPAGE_PMD_MASK) || + old_end - old_addr < HPAGE_PMD_SIZE || + (new_vma->vm_flags & VM_NOHUGEPAGE)) + goto out; + + /* + * 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)); + goto out; + } + + /* + * We don't have to worry about the ordering of src and dst + * ptlocks because exclusive mmap_sem prevents deadlock. + */ + ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl); + if (ret == 1) { + new_ptl = pmd_lockptr(mm, new_pmd); + if (new_ptl != old_ptl) + spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); + pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); + VM_BUG_ON(!pmd_none(*new_pmd)); + + if (pmd_move_must_withdraw(new_ptl, old_ptl)) { + pgtable_t pgtable; + pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); + pgtable_trans_huge_deposit(mm, new_pmd, pgtable); + } + set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); + if (new_ptl != old_ptl) + spin_unlock(new_ptl); + spin_unlock(old_ptl); + } +out: + return ret; +} + +/* + * 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, int prot_numa) +{ + struct mm_struct *mm = vma->vm_mm; + spinlock_t *ptl; + int ret = 0; + + if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { + pmd_t entry; + bool preserve_write = prot_numa && pmd_write(*pmd); + ret = 1; + + /* + * 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)) { + spin_unlock(ptl); + return ret; + } + + if (!prot_numa || !pmd_protnone(*pmd)) { + entry = pmdp_get_and_clear_notify(mm, addr, pmd); + entry = pmd_modify(entry, newprot); + if (preserve_write) + entry = pmd_mkwrite(entry); + ret = HPAGE_PMD_NR; + set_pmd_at(mm, addr, pmd, entry); + BUG_ON(!preserve_write && pmd_write(entry)); + } + spin_unlock(ptl); + } + + return ret; +} + +/* + * Returns 1 if a given pmd maps a stable (not under splitting) thp. + * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. + * + * Note that if it returns 1, this routine returns without unlocking page + * table locks. So callers must unlock them. + */ +int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma, + spinlock_t **ptl) +{ + *ptl = pmd_lock(vma->vm_mm, pmd); + if (likely(pmd_trans_huge(*pmd))) { + if (unlikely(pmd_trans_splitting(*pmd))) { + spin_unlock(*ptl); + wait_split_huge_page(vma->anon_vma, pmd); + return -1; + } else { + /* Thp mapped by 'pmd' is stable, so we can + * handle it as it is. */ + return 1; + } + } + spin_unlock(*ptl); + return 0; +} + +/* + * This function returns whether a given @page is mapped onto the @address + * in the virtual space of @mm. + * + * When it's true, this function returns *pmd with holding the page table lock + * and passing it back to the caller via @ptl. + * If it's false, returns NULL without holding the page table lock. + */ +pmd_t *page_check_address_pmd(struct page *page, + struct mm_struct *mm, + unsigned long address, + enum page_check_address_pmd_flag flag, + spinlock_t **ptl) +{ + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + + if (address & ~HPAGE_PMD_MASK) + return NULL; + + pgd = pgd_offset(mm, address); + if (!pgd_present(*pgd)) + return NULL; + pud = pud_offset(pgd, address); + if (!pud_present(*pud)) + return NULL; + pmd = pmd_offset(pud, address); + + *ptl = pmd_lock(mm, pmd); + if (!pmd_present(*pmd)) + goto unlock; + if (pmd_page(*pmd) != page) + goto unlock; + /* + * split_vma() may create temporary aliased mappings. There is + * no risk as long as all huge pmd are found and have their + * splitting bit set before __split_huge_page_refcount + * runs. Finding the same huge pmd more than once during the + * same rmap walk is not a problem. + */ + if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && + pmd_trans_splitting(*pmd)) + goto unlock; + if (pmd_trans_huge(*pmd)) { + VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && + !pmd_trans_splitting(*pmd)); + return pmd; + } +unlock: + spin_unlock(*ptl); + return NULL; +} + +static int __split_huge_page_splitting(struct page *page, + struct vm_area_struct *vma, + unsigned long address) +{ + struct mm_struct *mm = vma->vm_mm; + spinlock_t *ptl; + pmd_t *pmd; + int ret = 0; + /* For mmu_notifiers */ + const unsigned long mmun_start = address; + const unsigned long mmun_end = address + HPAGE_PMD_SIZE; + + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + pmd = page_check_address_pmd(page, mm, address, + PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl); + if (pmd) { + /* + * We can't temporarily set the pmd to null in order + * to split it, the pmd must remain marked huge at all + * times or the VM won't take the pmd_trans_huge paths + * and it won't wait on the anon_vma->root->rwsem to + * serialize against split_huge_page*. + */ + pmdp_splitting_flush(vma, address, pmd); + + ret = 1; + spin_unlock(ptl); + } + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + + return ret; +} + +static void __split_huge_page_refcount(struct page *page, + struct list_head *list) +{ + int i; + struct zone *zone = page_zone(page); + struct lruvec *lruvec; + int tail_count = 0; + + /* prevent PageLRU to go away from under us, and freeze lru stats */ + spin_lock_irq(&zone->lru_lock); + lruvec = mem_cgroup_page_lruvec(page, zone); + + compound_lock(page); + /* complete memcg works before add pages to LRU */ + mem_cgroup_split_huge_fixup(page); + + for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { + struct page *page_tail = page + i; + + /* tail_page->_mapcount cannot change */ + BUG_ON(page_mapcount(page_tail) < 0); + tail_count += page_mapcount(page_tail); + /* check for overflow */ + BUG_ON(tail_count < 0); + BUG_ON(atomic_read(&page_tail->_count) != 0); + /* + * tail_page->_count is zero and not changing from + * under us. But get_page_unless_zero() may be running + * from under us on the tail_page. If we used + * atomic_set() below instead of atomic_add(), we + * would then run atomic_set() concurrently with + * get_page_unless_zero(), and atomic_set() is + * implemented in C not using locked ops. spin_unlock + * on x86 sometime uses locked ops because of PPro + * errata 66, 92, so unless somebody can guarantee + * atomic_set() here would be safe on all archs (and + * not only on x86), it's safer to use atomic_add(). + */ + atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, + &page_tail->_count); + + /* after clearing PageTail the gup refcount can be released */ + smp_mb__after_atomic(); + + /* + * retain hwpoison flag of the poisoned tail page: + * fix for the unsuitable process killed on Guest Machine(KVM) + * by the memory-failure. + */ + page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; + page_tail->flags |= (page->flags & + ((1L << PG_referenced) | + (1L << PG_swapbacked) | + (1L << PG_mlocked) | + (1L << PG_uptodate) | + (1L << PG_active) | + (1L << PG_unevictable))); + page_tail->flags |= (1L << PG_dirty); + + /* clear PageTail before overwriting first_page */ + smp_wmb(); + + /* + * __split_huge_page_splitting() already set the + * splitting bit in all pmd that could map this + * hugepage, that will ensure no CPU can alter the + * mapcount on the head page. The mapcount is only + * accounted in the head page and it has to be + * transferred to all tail pages in the below code. So + * for this code to be safe, the split the mapcount + * can't change. But that doesn't mean userland can't + * keep changing and reading the page contents while + * we transfer the mapcount, so the pmd splitting + * status is achieved setting a reserved bit in the + * pmd, not by clearing the present bit. + */ + page_tail->_mapcount = page->_mapcount; + + BUG_ON(page_tail->mapping); + page_tail->mapping = page->mapping; + + page_tail->index = page->index + i; + page_cpupid_xchg_last(page_tail, page_cpupid_last(page)); + + BUG_ON(!PageAnon(page_tail)); + BUG_ON(!PageUptodate(page_tail)); + BUG_ON(!PageDirty(page_tail)); + BUG_ON(!PageSwapBacked(page_tail)); + + lru_add_page_tail(page, page_tail, lruvec, list); + } + atomic_sub(tail_count, &page->_count); + BUG_ON(atomic_read(&page->_count) <= 0); + + __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); + + ClearPageCompound(page); + compound_unlock(page); + spin_unlock_irq(&zone->lru_lock); + + for (i = 1; i < HPAGE_PMD_NR; i++) { + struct page *page_tail = page + i; + BUG_ON(page_count(page_tail) <= 0); + /* + * Tail pages 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(page_tail); + } + + /* + * Only the head page (now become a regular page) is required + * to be pinned by the caller. + */ + BUG_ON(page_count(page) <= 0); +} + +static int __split_huge_page_map(struct page *page, + struct vm_area_struct *vma, + unsigned long address) +{ + struct mm_struct *mm = vma->vm_mm; + spinlock_t *ptl; + pmd_t *pmd, _pmd; + int ret = 0, i; + pgtable_t pgtable; + unsigned long haddr; + + pmd = page_check_address_pmd(page, mm, address, + PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl); + if (pmd) { + pgtable = pgtable_trans_huge_withdraw(mm, pmd); + pmd_populate(mm, &_pmd, pgtable); + if (pmd_write(*pmd)) + BUG_ON(page_mapcount(page) != 1); + + haddr = address; + for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { + pte_t *pte, entry; + BUG_ON(PageCompound(page+i)); + /* + * Note that NUMA hinting access restrictions are not + * transferred to avoid any possibility of altering + * permissions across VMAs. + */ + entry = mk_pte(page + i, vma->vm_page_prot); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + if (!pmd_write(*pmd)) + entry = pte_wrprotect(entry); + if (!pmd_young(*pmd)) + entry = pte_mkold(entry); + pte = pte_offset_map(&_pmd, haddr); + BUG_ON(!pte_none(*pte)); + set_pte_at(mm, haddr, pte, entry); + pte_unmap(pte); + } + + smp_wmb(); /* make pte visible before 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/us/Processor_TechDocs/41322.pdf, + * Erratum 383 on page 93. 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_tlb_range();" we first + * mark the current pmd notpresent (atomically because + * here the pmd_trans_huge and pmd_trans_splitting + * 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. + */ + pmdp_invalidate(vma, address, pmd); + pmd_populate(mm, pmd, pgtable); + ret = 1; + spin_unlock(ptl); + } + + return ret; +} + +/* must be called with anon_vma->root->rwsem held */ +static void __split_huge_page(struct page *page, + struct anon_vma *anon_vma, + struct list_head *list) +{ + int mapcount, mapcount2; + pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); + struct anon_vma_chain *avc; + + BUG_ON(!PageHead(page)); + BUG_ON(PageTail(page)); + + mapcount = 0; + anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { + struct vm_area_struct *vma = avc->vma; + unsigned long addr = vma_address(page, vma); + BUG_ON(is_vma_temporary_stack(vma)); + mapcount += __split_huge_page_splitting(page, vma, addr); + } + /* + * It is critical that new vmas are added to the tail of the + * anon_vma list. This guarantes that if copy_huge_pmd() runs + * and establishes a child pmd before + * __split_huge_page_splitting() freezes the parent pmd (so if + * we fail to prevent copy_huge_pmd() from running until the + * whole __split_huge_page() is complete), we will still see + * the newly established pmd of the child later during the + * walk, to be able to set it as pmd_trans_splitting too. + */ + if (mapcount != page_mapcount(page)) { + pr_err("mapcount %d page_mapcount %d\n", + mapcount, page_mapcount(page)); + BUG(); + } + + __split_huge_page_refcount(page, list); + + mapcount2 = 0; + anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { + struct vm_area_struct *vma = avc->vma; + unsigned long addr = vma_address(page, vma); + BUG_ON(is_vma_temporary_stack(vma)); + mapcount2 += __split_huge_page_map(page, vma, addr); + } + if (mapcount != mapcount2) { + pr_err("mapcount %d mapcount2 %d page_mapcount %d\n", + mapcount, mapcount2, page_mapcount(page)); + BUG(); + } +} + +/* + * Split a hugepage into normal pages. This doesn't change the position of head + * page. 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. + * Return 0 if the hugepage is split successfully otherwise return 1. + */ +int split_huge_page_to_list(struct page *page, struct list_head *list) +{ + struct anon_vma *anon_vma; + int ret = 1; + + BUG_ON(is_huge_zero_page(page)); + BUG_ON(!PageAnon(page)); + + /* + * The caller does not necessarily hold an mmap_sem 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(page); + if (!anon_vma) + goto out; + anon_vma_lock_write(anon_vma); + + ret = 0; + if (!PageCompound(page)) + goto out_unlock; + + BUG_ON(!PageSwapBacked(page)); + __split_huge_page(page, anon_vma, list); + count_vm_event(THP_SPLIT); + + BUG_ON(PageCompound(page)); +out_unlock: + anon_vma_unlock_write(anon_vma); + put_anon_vma(anon_vma); +out: + return ret; +} + +#define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE) + +int hugepage_madvise(struct vm_area_struct *vma, + unsigned long *vm_flags, int advice) +{ + switch (advice) { + case MADV_HUGEPAGE: +#ifdef CONFIG_S390 + /* + * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 + * can't handle this properly after s390_enable_sie, so we simply + * ignore the madvise to prevent qemu from causing a SIGSEGV. + */ + if (mm_has_pgste(vma->vm_mm)) + return 0; +#endif + /* + * Be somewhat over-protective like KSM for now! + */ + if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) + return -EINVAL; + *vm_flags &= ~VM_NOHUGEPAGE; + *vm_flags |= VM_HUGEPAGE; + /* + * If the vma become good for khugepaged to scan, + * register it here without waiting a page fault that + * may not happen any time soon. + */ + if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags))) + return -ENOMEM; + break; + case MADV_NOHUGEPAGE: + /* + * Be somewhat over-protective like KSM for now! + */ + if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) + return -EINVAL; + *vm_flags &= ~VM_HUGEPAGE; + *vm_flags |= VM_NOHUGEPAGE; + /* + * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning + * this vma even if we leave the mm registered in khugepaged if + * it got registered before VM_NOHUGEPAGE was set. + */ + break; + } + + return 0; +} + +static int __init khugepaged_slab_init(void) +{ + mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", + sizeof(struct mm_slot), + __alignof__(struct mm_slot), 0, NULL); + if (!mm_slot_cache) + return -ENOMEM; + + return 0; +} + +static void __init khugepaged_slab_exit(void) +{ + kmem_cache_destroy(mm_slot_cache); +} + +static inline struct mm_slot *alloc_mm_slot(void) +{ + if (!mm_slot_cache) /* initialization failed */ + return NULL; + return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); +} + +static inline void free_mm_slot(struct mm_slot *mm_slot) +{ + kmem_cache_free(mm_slot_cache, mm_slot); +} + +static struct mm_slot *get_mm_slot(struct mm_struct *mm) +{ + struct mm_slot *mm_slot; + + hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) + if (mm == mm_slot->mm) + return mm_slot; + + return NULL; +} + +static void insert_to_mm_slots_hash(struct mm_struct *mm, + struct mm_slot *mm_slot) +{ + mm_slot->mm = mm; + hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); +} + +static inline int khugepaged_test_exit(struct mm_struct *mm) +{ + return atomic_read(&mm->mm_users) == 0; +} + +int __khugepaged_enter(struct mm_struct *mm) +{ + struct mm_slot *mm_slot; + int wakeup; + + mm_slot = alloc_mm_slot(); + if (!mm_slot) + return -ENOMEM; + + /* __khugepaged_exit() must not run from under us */ + VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); + if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { + free_mm_slot(mm_slot); + return 0; + } + + spin_lock(&khugepaged_mm_lock); + insert_to_mm_slots_hash(mm, mm_slot); + /* + * Insert just behind the scanning cursor, to let the area settle + * down a little. + */ + wakeup = list_empty(&khugepaged_scan.mm_head); + list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); + spin_unlock(&khugepaged_mm_lock); + + atomic_inc(&mm->mm_count); + if (wakeup) + wake_up_interruptible(&khugepaged_wait); + + return 0; +} + +int khugepaged_enter_vma_merge(struct vm_area_struct *vma, + unsigned long vm_flags) +{ + unsigned long hstart, hend; + if (!vma->anon_vma) + /* + * Not yet faulted in so we will register later in the + * page fault if needed. + */ + return 0; + if (vma->vm_ops) + /* khugepaged not yet working on file or special mappings */ + return 0; + VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma); + hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; + hend = vma->vm_end & HPAGE_PMD_MASK; + if (hstart < hend) + return khugepaged_enter(vma, vm_flags); + return 0; +} + +void __khugepaged_exit(struct mm_struct *mm) +{ + struct mm_slot *mm_slot; + int free = 0; + + spin_lock(&khugepaged_mm_lock); + mm_slot = get_mm_slot(mm); + if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { + hash_del(&mm_slot->hash); + list_del(&mm_slot->mm_node); + free = 1; + } + spin_unlock(&khugepaged_mm_lock); + + if (free) { + clear_bit(MMF_VM_HUGEPAGE, &mm->flags); + free_mm_slot(mm_slot); + mmdrop(mm); + } else if (mm_slot) { + /* + * This is required to serialize against + * khugepaged_test_exit() (which is guaranteed to run + * under mmap sem read mode). Stop here (after we + * return all pagetables will be destroyed) until + * khugepaged has finished working on the pagetables + * under the mmap_sem. + */ + down_write(&mm->mmap_sem); + up_write(&mm->mmap_sem); + } +} + +static void release_pte_page(struct page *page) +{ + /* 0 stands for page_is_file_cache(page) == false */ + dec_zone_page_state(page, NR_ISOLATED_ANON + 0); + unlock_page(page); + putback_lru_page(page); +} + +static void release_pte_pages(pte_t *pte, pte_t *_pte) +{ + while (--_pte >= pte) { + pte_t pteval = *_pte; + if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) + release_pte_page(pte_page(pteval)); + } +} + +static int __collapse_huge_page_isolate(struct vm_area_struct *vma, + unsigned long address, + pte_t *pte) +{ + struct page *page; + pte_t *_pte; + int none_or_zero = 0; + bool referenced = false, writable = false; + for (_pte = pte; _pte < pte+HPAGE_PMD_NR; + _pte++, address += PAGE_SIZE) { + pte_t pteval = *_pte; + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + if (++none_or_zero <= khugepaged_max_ptes_none) + continue; + else + goto out; + } + if (!pte_present(pteval)) + goto out; + page = vm_normal_page(vma, address, pteval); + if (unlikely(!page)) + goto out; + + VM_BUG_ON_PAGE(PageCompound(page), page); + VM_BUG_ON_PAGE(!PageAnon(page), page); + VM_BUG_ON_PAGE(!PageSwapBacked(page), page); + + /* + * We can do it before isolate_lru_page because the + * page can't be freed from under us. NOTE: PG_lock + * is needed to serialize against split_huge_page + * when invoked from the VM. + */ + if (!trylock_page(page)) + goto out; + + /* + * cannot use mapcount: can't collapse if there's a gup pin. + * The page must only be referenced by the scanned process + * and page swap cache. + */ + if (page_count(page) != 1 + !!PageSwapCache(page)) { + unlock_page(page); + goto out; + } + if (pte_write(pteval)) { + writable = true; + } else { + if (PageSwapCache(page) && !reuse_swap_page(page)) { + unlock_page(page); + goto out; + } + /* + * Page is not in the swap cache. It can be collapsed + * into a THP. + */ + } + + /* + * Isolate the page to avoid collapsing an hugepage + * currently in use by the VM. + */ + if (isolate_lru_page(page)) { + unlock_page(page); + goto out; + } + /* 0 stands for page_is_file_cache(page) == false */ + inc_zone_page_state(page, NR_ISOLATED_ANON + 0); + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(PageLRU(page), page); + + /* If there is no mapped pte young don't collapse the page */ + if (pte_young(pteval) || PageReferenced(page) || + mmu_notifier_test_young(vma->vm_mm, address)) + referenced = true; + } + if (likely(referenced && writable)) + return 1; +out: + release_pte_pages(pte, _pte); + return 0; +} + +static void __collapse_huge_page_copy(pte_t *pte, struct page *page, + struct vm_area_struct *vma, + unsigned long address, + spinlock_t *ptl) +{ + pte_t *_pte; + for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { + pte_t pteval = *_pte; + struct page *src_page; + + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + clear_user_highpage(page, address); + add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); + if (is_zero_pfn(pte_pfn(pteval))) { + /* + * ptl mostly unnecessary. + */ + spin_lock(ptl); + /* + * paravirt calls inside pte_clear here are + * superfluous. + */ + pte_clear(vma->vm_mm, address, _pte); + spin_unlock(ptl); + } + } else { + src_page = pte_page(pteval); + copy_user_highpage(page, src_page, address, vma); + VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); + release_pte_page(src_page); + /* + * ptl mostly unnecessary, but preempt has to + * be disabled to update the per-cpu stats + * inside page_remove_rmap(). + */ + spin_lock(ptl); + /* + * paravirt calls inside pte_clear here are + * superfluous. + */ + pte_clear(vma->vm_mm, address, _pte); + page_remove_rmap(src_page); + spin_unlock(ptl); + free_page_and_swap_cache(src_page); + } + + address += PAGE_SIZE; + page++; + } +} + +static void khugepaged_alloc_sleep(void) +{ + wait_event_freezable_timeout(khugepaged_wait, false, + msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); +} + +static int khugepaged_node_load[MAX_NUMNODES]; + +static bool khugepaged_scan_abort(int nid) +{ + int i; + + /* + * If zone_reclaim_mode is disabled, then no extra effort is made to + * allocate memory locally. + */ + if (!zone_reclaim_mode) + return false; + + /* If there is a count for this node already, it must be acceptable */ + if (khugepaged_node_load[nid]) + return false; + + for (i = 0; i < MAX_NUMNODES; i++) { + if (!khugepaged_node_load[i]) + continue; + if (node_distance(nid, i) > RECLAIM_DISTANCE) + return true; + } + return false; +} + +#ifdef CONFIG_NUMA +static int khugepaged_find_target_node(void) +{ + static int last_khugepaged_target_node = NUMA_NO_NODE; + int nid, target_node = 0, max_value = 0; + + /* find first node with max normal pages hit */ + for (nid = 0; nid < MAX_NUMNODES; nid++) + if (khugepaged_node_load[nid] > max_value) { + max_value = khugepaged_node_load[nid]; + target_node = nid; + } + + /* do some balance if several nodes have the same hit record */ + if (target_node <= last_khugepaged_target_node) + for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; + nid++) + if (max_value == khugepaged_node_load[nid]) { + target_node = nid; + break; + } + + last_khugepaged_target_node = target_node; + return target_node; +} + +static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) +{ + if (IS_ERR(*hpage)) { + if (!*wait) + return false; + + *wait = false; + *hpage = NULL; + khugepaged_alloc_sleep(); + } else if (*hpage) { + put_page(*hpage); + *hpage = NULL; + } + + return true; +} + +static struct page * +khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, + struct vm_area_struct *vma, unsigned long address, + int node) +{ + VM_BUG_ON_PAGE(*hpage, *hpage); + + /* + * Before allocating the hugepage, release the mmap_sem read lock. + * The allocation can take potentially a long time if it involves + * sync compaction, and we do not need to hold the mmap_sem during + * that. We will recheck the vma after taking it again in write mode. + */ + up_read(&mm->mmap_sem); + + *hpage = alloc_pages_exact_node(node, gfp, HPAGE_PMD_ORDER); + if (unlikely(!*hpage)) { + count_vm_event(THP_COLLAPSE_ALLOC_FAILED); + *hpage = ERR_PTR(-ENOMEM); + return NULL; + } + + count_vm_event(THP_COLLAPSE_ALLOC); + return *hpage; +} +#else +static int khugepaged_find_target_node(void) +{ + return 0; +} + +static inline struct page *alloc_hugepage(int defrag) +{ + return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), + HPAGE_PMD_ORDER); +} + +static struct page *khugepaged_alloc_hugepage(bool *wait) +{ + struct page *hpage; + + do { + hpage = alloc_hugepage(khugepaged_defrag()); + if (!hpage) { + count_vm_event(THP_COLLAPSE_ALLOC_FAILED); + if (!*wait) + return NULL; + + *wait = false; + khugepaged_alloc_sleep(); + } else + count_vm_event(THP_COLLAPSE_ALLOC); + } while (unlikely(!hpage) && likely(khugepaged_enabled())); + + return hpage; +} + +static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) +{ + if (!*hpage) + *hpage = khugepaged_alloc_hugepage(wait); + + if (unlikely(!*hpage)) + return false; + + return true; +} + +static struct page * +khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, + struct vm_area_struct *vma, unsigned long address, + int node) +{ + up_read(&mm->mmap_sem); + VM_BUG_ON(!*hpage); + + return *hpage; +} +#endif + +static bool hugepage_vma_check(struct vm_area_struct *vma) +{ + if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || + (vma->vm_flags & VM_NOHUGEPAGE)) + return false; + + if (!vma->anon_vma || vma->vm_ops) + return false; + if (is_vma_temporary_stack(vma)) + return false; + VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma); + return true; +} + +static void collapse_huge_page(struct mm_struct *mm, + unsigned long address, + struct page **hpage, + struct vm_area_struct *vma, + int node) +{ + pmd_t *pmd, _pmd; + pte_t *pte; + pgtable_t pgtable; + struct page *new_page; + spinlock_t *pmd_ptl, *pte_ptl; + int isolated; + unsigned long hstart, hend; + struct mem_cgroup *memcg; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ + gfp_t gfp; + + VM_BUG_ON(address & ~HPAGE_PMD_MASK); + + /* Only allocate from the target node */ + gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) | + __GFP_THISNODE; + + /* release the mmap_sem read lock. */ + new_page = khugepaged_alloc_page(hpage, gfp, mm, vma, address, node); + if (!new_page) + return; + + if (unlikely(mem_cgroup_try_charge(new_page, mm, + gfp, &memcg))) + return; + + /* + * Prevent all access to pagetables with the exception of + * gup_fast later hanlded by the ptep_clear_flush and the VM + * handled by the anon_vma lock + PG_lock. + */ + down_write(&mm->mmap_sem); + if (unlikely(khugepaged_test_exit(mm))) + goto out; + + vma = find_vma(mm, address); + if (!vma) + goto out; + hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; + hend = vma->vm_end & HPAGE_PMD_MASK; + if (address < hstart || address + HPAGE_PMD_SIZE > hend) + goto out; + if (!hugepage_vma_check(vma)) + goto out; + pmd = mm_find_pmd(mm, address); + if (!pmd) + goto out; + + anon_vma_lock_write(vma->anon_vma); + + pte = pte_offset_map(pmd, address); + pte_ptl = pte_lockptr(mm, pmd); + + mmun_start = address; + mmun_end = address + HPAGE_PMD_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ + /* + * After this gup_fast can't run anymore. This also removes + * any huge TLB entry from the CPU so we won't allow + * huge and small TLB entries for the same virtual address + * to avoid the risk of CPU bugs in that area. + */ + _pmd = pmdp_clear_flush(vma, address, pmd); + spin_unlock(pmd_ptl); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + + spin_lock(pte_ptl); + isolated = __collapse_huge_page_isolate(vma, address, pte); + spin_unlock(pte_ptl); + + if (unlikely(!isolated)) { + pte_unmap(pte); + spin_lock(pmd_ptl); + BUG_ON(!pmd_none(*pmd)); + /* + * We can only use set_pmd_at when establishing + * hugepmds and never for establishing regular pmds that + * points to regular pagetables. Use pmd_populate for that + */ + pmd_populate(mm, pmd, pmd_pgtable(_pmd)); + spin_unlock(pmd_ptl); + anon_vma_unlock_write(vma->anon_vma); + goto out; + } + + /* + * All pages are isolated and locked so anon_vma rmap + * can't run anymore. + */ + anon_vma_unlock_write(vma->anon_vma); + + __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); + pte_unmap(pte); + __SetPageUptodate(new_page); + pgtable = pmd_pgtable(_pmd); + + _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); + _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); + + /* + * spin_lock() below is not the equivalent of smp_wmb(), so + * this is needed to avoid the copy_huge_page writes to become + * visible after the set_pmd_at() write. + */ + smp_wmb(); + + spin_lock(pmd_ptl); + BUG_ON(!pmd_none(*pmd)); + page_add_new_anon_rmap(new_page, vma, address); + mem_cgroup_commit_charge(new_page, memcg, false); + lru_cache_add_active_or_unevictable(new_page, vma); + pgtable_trans_huge_deposit(mm, pmd, pgtable); + set_pmd_at(mm, address, pmd, _pmd); + update_mmu_cache_pmd(vma, address, pmd); + spin_unlock(pmd_ptl); + + *hpage = NULL; + + khugepaged_pages_collapsed++; +out_up_write: + up_write(&mm->mmap_sem); + return; + +out: + mem_cgroup_cancel_charge(new_page, memcg); + goto out_up_write; +} + +static int khugepaged_scan_pmd(struct mm_struct *mm, + struct vm_area_struct *vma, + unsigned long address, + struct page **hpage) +{ + pmd_t *pmd; + pte_t *pte, *_pte; + int ret = 0, none_or_zero = 0; + struct page *page; + unsigned long _address; + spinlock_t *ptl; + int node = NUMA_NO_NODE; + bool writable = false, referenced = false; + + VM_BUG_ON(address & ~HPAGE_PMD_MASK); + + pmd = mm_find_pmd(mm, address); + if (!pmd) + goto out; + + memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); + pte = pte_offset_map_lock(mm, pmd, address, &ptl); + for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; + _pte++, _address += PAGE_SIZE) { + pte_t pteval = *_pte; + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + if (++none_or_zero <= khugepaged_max_ptes_none) + continue; + else + goto out_unmap; + } + if (!pte_present(pteval)) + goto out_unmap; + if (pte_write(pteval)) + writable = true; + + page = vm_normal_page(vma, _address, pteval); + if (unlikely(!page)) + goto out_unmap; + /* + * Record which node the original page is from and save this + * information to khugepaged_node_load[]. + * Khupaged will allocate hugepage from the node has the max + * hit record. + */ + node = page_to_nid(page); + if (khugepaged_scan_abort(node)) + goto out_unmap; + khugepaged_node_load[node]++; + VM_BUG_ON_PAGE(PageCompound(page), page); + if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) + goto out_unmap; + /* + * cannot use mapcount: can't collapse if there's a gup pin. + * The page must only be referenced by the scanned process + * and page swap cache. + */ + if (page_count(page) != 1 + !!PageSwapCache(page)) + goto out_unmap; + if (pte_young(pteval) || PageReferenced(page) || + mmu_notifier_test_young(vma->vm_mm, address)) + referenced = true; + } + if (referenced && writable) + ret = 1; +out_unmap: + pte_unmap_unlock(pte, ptl); + if (ret) { + node = khugepaged_find_target_node(); + /* collapse_huge_page will return with the mmap_sem released */ + collapse_huge_page(mm, address, hpage, vma, node); + } +out: + return ret; +} + +static void collect_mm_slot(struct mm_slot *mm_slot) +{ + struct mm_struct *mm = mm_slot->mm; + + VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); + + if (khugepaged_test_exit(mm)) { + /* free mm_slot */ + hash_del(&mm_slot->hash); + list_del(&mm_slot->mm_node); + + /* + * Not strictly needed because the mm exited already. + * + * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); + */ + + /* khugepaged_mm_lock actually not necessary for the below */ + free_mm_slot(mm_slot); + mmdrop(mm); + } +} + +static unsigned int khugepaged_scan_mm_slot(unsigned int pages, + struct page **hpage) + __releases(&khugepaged_mm_lock) + __acquires(&khugepaged_mm_lock) +{ + struct mm_slot *mm_slot; + struct mm_struct *mm; + struct vm_area_struct *vma; + int progress = 0; + + VM_BUG_ON(!pages); + VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); + + if (khugepaged_scan.mm_slot) + mm_slot = khugepaged_scan.mm_slot; + else { + mm_slot = list_entry(khugepaged_scan.mm_head.next, + struct mm_slot, mm_node); + khugepaged_scan.address = 0; + khugepaged_scan.mm_slot = mm_slot; + } + spin_unlock(&khugepaged_mm_lock); + + mm = mm_slot->mm; + down_read(&mm->mmap_sem); + if (unlikely(khugepaged_test_exit(mm))) + vma = NULL; + else + vma = find_vma(mm, khugepaged_scan.address); + + progress++; + for (; vma; vma = vma->vm_next) { + unsigned long hstart, hend; + + cond_resched(); + if (unlikely(khugepaged_test_exit(mm))) { + progress++; + break; + } + if (!hugepage_vma_check(vma)) { +skip: + progress++; + continue; + } + hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; + hend = vma->vm_end & HPAGE_PMD_MASK; + if (hstart >= hend) + goto skip; + if (khugepaged_scan.address > hend) + goto skip; + if (khugepaged_scan.address < hstart) + khugepaged_scan.address = hstart; + VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); + + while (khugepaged_scan.address < hend) { + int ret; + cond_resched(); + if (unlikely(khugepaged_test_exit(mm))) + goto breakouterloop; + + VM_BUG_ON(khugepaged_scan.address < hstart || + khugepaged_scan.address + HPAGE_PMD_SIZE > + hend); + ret = khugepaged_scan_pmd(mm, vma, + khugepaged_scan.address, + hpage); + /* move to next address */ + khugepaged_scan.address += HPAGE_PMD_SIZE; + progress += HPAGE_PMD_NR; + if (ret) + /* we released mmap_sem so break loop */ + goto breakouterloop_mmap_sem; + if (progress >= pages) + goto breakouterloop; + } + } +breakouterloop: + up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ +breakouterloop_mmap_sem: + + spin_lock(&khugepaged_mm_lock); + VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); + /* + * Release the current mm_slot if this mm is about to die, or + * if we scanned all vmas of this mm. + */ + if (khugepaged_test_exit(mm) || !vma) { + /* + * Make sure that if mm_users is reaching zero while + * khugepaged runs here, khugepaged_exit will find + * mm_slot not pointing to the exiting mm. + */ + if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { + khugepaged_scan.mm_slot = list_entry( + mm_slot->mm_node.next, + struct mm_slot, mm_node); + khugepaged_scan.address = 0; + } else { + khugepaged_scan.mm_slot = NULL; + khugepaged_full_scans++; + } + + collect_mm_slot(mm_slot); + } + + return progress; +} + +static int khugepaged_has_work(void) +{ + return !list_empty(&khugepaged_scan.mm_head) && + khugepaged_enabled(); +} + +static int khugepaged_wait_event(void) +{ + return !list_empty(&khugepaged_scan.mm_head) || + kthread_should_stop(); +} + +static void khugepaged_do_scan(void) +{ + struct page *hpage = NULL; + unsigned int progress = 0, pass_through_head = 0; + unsigned int pages = khugepaged_pages_to_scan; + bool wait = true; + + barrier(); /* write khugepaged_pages_to_scan to local stack */ + + while (progress < pages) { + if (!khugepaged_prealloc_page(&hpage, &wait)) + break; + + cond_resched(); + + if (unlikely(kthread_should_stop() || freezing(current))) + break; + + spin_lock(&khugepaged_mm_lock); + if (!khugepaged_scan.mm_slot) + pass_through_head++; + if (khugepaged_has_work() && + pass_through_head < 2) + progress += khugepaged_scan_mm_slot(pages - progress, + &hpage); + else + progress = pages; + spin_unlock(&khugepaged_mm_lock); + } + + if (!IS_ERR_OR_NULL(hpage)) + put_page(hpage); +} + +static void khugepaged_wait_work(void) +{ + try_to_freeze(); + + if (khugepaged_has_work()) { + if (!khugepaged_scan_sleep_millisecs) + return; + + wait_event_freezable_timeout(khugepaged_wait, + kthread_should_stop(), + msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); + return; + } + + if (khugepaged_enabled()) + wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); +} + +static int khugepaged(void *none) +{ + struct mm_slot *mm_slot; + + set_freezable(); + set_user_nice(current, MAX_NICE); + + while (!kthread_should_stop()) { + khugepaged_do_scan(); + khugepaged_wait_work(); + } + + spin_lock(&khugepaged_mm_lock); + mm_slot = khugepaged_scan.mm_slot; + khugepaged_scan.mm_slot = NULL; + if (mm_slot) + collect_mm_slot(mm_slot); + spin_unlock(&khugepaged_mm_lock); + return 0; +} + +static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, + unsigned long haddr, pmd_t *pmd) +{ + struct mm_struct *mm = vma->vm_mm; + pgtable_t pgtable; + pmd_t _pmd; + int i; + + pmdp_clear_flush_notify(vma, haddr, pmd); + /* leave pmd empty until pte is filled */ + + pgtable = pgtable_trans_huge_withdraw(mm, pmd); + pmd_populate(mm, &_pmd, pgtable); + + for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { + pte_t *pte, entry; + entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); + entry = pte_mkspecial(entry); + pte = pte_offset_map(&_pmd, haddr); + VM_BUG_ON(!pte_none(*pte)); + set_pte_at(mm, haddr, pte, entry); + pte_unmap(pte); + } + smp_wmb(); /* make pte visible before pmd */ + pmd_populate(mm, pmd, pgtable); + put_huge_zero_page(); +} + +void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmd) +{ + spinlock_t *ptl; + struct page *page; + struct mm_struct *mm = vma->vm_mm; + unsigned long haddr = address & HPAGE_PMD_MASK; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ + + BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); + + mmun_start = haddr; + mmun_end = haddr + HPAGE_PMD_SIZE; +again: + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + ptl = pmd_lock(mm, pmd); + if (unlikely(!pmd_trans_huge(*pmd))) { + spin_unlock(ptl); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + return; + } + if (is_huge_zero_pmd(*pmd)) { + __split_huge_zero_page_pmd(vma, haddr, pmd); + spin_unlock(ptl); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + return; + } + page = pmd_page(*pmd); + VM_BUG_ON_PAGE(!page_count(page), page); + get_page(page); + spin_unlock(ptl); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + + split_huge_page(page); + + put_page(page); + + /* + * We don't always have down_write of mmap_sem here: a racing + * do_huge_pmd_wp_page() might have copied-on-write to another + * huge page before our split_huge_page() got the anon_vma lock. + */ + if (unlikely(pmd_trans_huge(*pmd))) + goto again; +} + +void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, + pmd_t *pmd) +{ + struct vm_area_struct *vma; + + vma = find_vma(mm, address); + BUG_ON(vma == NULL); + split_huge_page_pmd(vma, address, pmd); +} + +static void split_huge_page_address(struct mm_struct *mm, + unsigned long address) +{ + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + + VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); + + pgd = pgd_offset(mm, address); + if (!pgd_present(*pgd)) + return; + + pud = pud_offset(pgd, address); + if (!pud_present(*pud)) + return; + + pmd = pmd_offset(pud, address); + if (!pmd_present(*pmd)) + return; + /* + * Caller holds the mmap_sem write mode, so a huge pmd cannot + * materialize from under us. + */ + split_huge_page_pmd_mm(mm, address, pmd); +} + +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_page_address(vma->vm_mm, start); + + /* + * 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_page_address(vma->vm_mm, end); + + /* + * If we're also updating the vma->vm_next->vm_start, if the new + * vm_next->vm_start isn't page 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 << PAGE_SHIFT; + if (nstart & ~HPAGE_PMD_MASK && + (nstart & HPAGE_PMD_MASK) >= next->vm_start && + (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) + split_huge_page_address(next->vm_mm, nstart); + } +} |