/* * 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. */ #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 enabled for all mappings * and khugepaged scans all mappings. Defrag is only invoked by * khugepaged hugepage allocations and by page faults inside * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived * 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); #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; if (!khugepaged_enabled()) return 0; 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) min_free_kbytes = recommended_min; setup_per_zone_wmarks(); return 0; } late_initcall(set_recommended_min_free_kbytes); static int start_khugepaged(void) { int err = 0; if (khugepaged_enabled()) { if (!khugepaged_thread) khugepaged_thread = kthread_run(khugepaged, NULL, "khugepaged"); if (unlikely(IS_ERR(khugepaged_thread))) { printk(KERN_ERR "khugepaged: kthread_run(khugepaged) failed\n"); err = PTR_ERR(khugepaged_thread); khugepaged_thread = NULL; } 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; } return err; } static atomic_t huge_zero_refcount; static struct page *huge_zero_page __read_mostly; static inline bool is_huge_zero_page(struct page *page) { return ACCESS_ONCE(huge_zero_page) == page; } 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 ACCESS_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_page(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 ACCESS_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 int shrink_huge_zero_page(struct shrinker *shrink, struct shrink_control *sc) { if (!sc->nr_to_scan) /* we can free zero page only if last reference remains */ return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { struct page *zero_page = xchg(&huge_zero_page, NULL); BUG_ON(zero_page == NULL); __free_page(zero_page); } return 0; } static struct shrinker huge_zero_page_shrinker = { .shrink = shrink_huge_zero_page, .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_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 = strict_strtoul(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 = strict_strtoul(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 = strict_strtoul(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 = strict_strtoul(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)) { printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n"); return -ENOMEM; } err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); if (err) { printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n"); goto delete_obj; } err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); if (err) { printk(KERN_ERR "hugepage: 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) return err; err = khugepaged_slab_init(); if (err) goto out; register_shrinker(&huge_zero_page_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; start_khugepaged(); return 0; out: hugepage_exit_sysfs(hugepage_kobj); return err; } module_init(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) printk(KERN_WARNING "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, struct vm_area_struct *vma) { pmd_t entry; entry = mk_pmd(page, vma->vm_page_prot); entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); 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) { pgtable_t pgtable; VM_BUG_ON(!PageCompound(page)); pgtable = pte_alloc_one(mm, haddr); if (unlikely(!pgtable)) 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); spin_lock(&mm->page_table_lock); if (unlikely(!pmd_none(*pmd))) { spin_unlock(&mm->page_table_lock); mem_cgroup_uncharge_page(page); put_page(page); pte_free(mm, pgtable); } else { pmd_t entry; entry = mk_huge_pmd(page, vma); page_add_new_anon_rmap(page, vma, haddr); set_pmd_at(mm, haddr, pmd, entry); pgtable_trans_huge_deposit(mm, pgtable); add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); mm->nr_ptes++; spin_unlock(&mm->page_table_lock); } return 0; } static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) { return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; } static inline struct page *alloc_hugepage_vma(int defrag, struct vm_area_struct *vma, unsigned long haddr, int nd, gfp_t extra_gfp) { return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp), HPAGE_PMD_ORDER, vma, haddr, nd); } #ifndef CONFIG_NUMA static inline struct page *alloc_hugepage(int defrag) { return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), HPAGE_PMD_ORDER); } #endif 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_wrprotect(entry); entry = pmd_mkhuge(entry); set_pmd_at(mm, haddr, pmd, entry); pgtable_trans_huge_deposit(mm, pgtable); 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) { struct page *page; unsigned long haddr = address & HPAGE_PMD_MASK; pte_t *pte; if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { if (unlikely(anon_vma_prepare(vma))) return VM_FAULT_OOM; if (unlikely(khugepaged_enter(vma))) return VM_FAULT_OOM; if (!(flags & FAULT_FLAG_WRITE) && transparent_hugepage_use_zero_page()) { 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); goto out; } spin_lock(&mm->page_table_lock); set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, zero_page); spin_unlock(&mm->page_table_lock); if (!set) { pte_free(mm, pgtable); put_huge_zero_page(); } return 0; } page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), vma, haddr, numa_node_id(), 0); if (unlikely(!page)) { count_vm_event(THP_FAULT_FALLBACK); goto out; } count_vm_event(THP_FAULT_ALLOC); if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { put_page(page); goto out; } if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page))) { mem_cgroup_uncharge_page(page); put_page(page); goto out; } return 0; } out: /* * Use __pte_alloc instead of pte_alloc_map, because we can't * run pte_offset_map on the pmd, if an huge pmd could * materialize from under us from a different thread. */ if (unlikely(pmd_none(*pmd)) && unlikely(__pte_alloc(mm, vma, pmd, address))) return VM_FAULT_OOM; /* if an huge pmd materialized from under us just retry later */ if (unlikely(pmd_trans_huge(*pmd))) return 0; /* * A regular pmd is established and it can't morph into a huge pmd * from under us anymore at this point because we hold the mmap_sem * read mode and khugepaged takes it in write mode. So now it's * safe to run pte_offset_map(). */ pte = pte_offset_map(pmd, address); return handle_pte_fault(mm, vma, address, pte, pmd, flags); } 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) { 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; spin_lock(&dst_mm->page_table_lock); spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); ret = -EAGAIN; pmd = *src_pmd; if (unlikely(!pmd_trans_huge(pmd))) { pte_free(dst_mm, pgtable); goto out_unlock; } /* * mm->page_table_lock is enough to be sure that huge zero pmd is not * 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_mm->page_table_lock); spin_unlock(&dst_mm->page_table_lock); 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(!PageHead(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)); set_pmd_at(dst_mm, addr, dst_pmd, pmd); pgtable_trans_huge_deposit(dst_mm, pgtable); dst_mm->nr_ptes++; ret = 0; out_unlock: spin_unlock(&src_mm->page_table_lock); spin_unlock(&dst_mm->page_table_lock); 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) { pmd_t entry; unsigned long haddr; spin_lock(&mm->page_table_lock); 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(&mm->page_table_lock); } static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr) { pgtable_t pgtable; pmd_t _pmd; struct page *page; int i, ret = 0; unsigned long mmun_start; /* For mmu_notifiers */ unsigned long mmun_end; /* For mmu_notifiers */ page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); if (!page) { ret |= VM_FAULT_OOM; goto out; } if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) { put_page(page); ret |= VM_FAULT_OOM; goto out; } clear_user_highpage(page, address); __SetPageUptodate(page); mmun_start = haddr; mmun_end = haddr + HPAGE_PMD_SIZE; mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); spin_lock(&mm->page_table_lock); if (unlikely(!pmd_same(*pmd, orig_pmd))) goto out_free_page; pmdp_clear_flush(vma, haddr, pmd); /* leave pmd empty until pte is filled */ pgtable = pgtable_trans_huge_withdraw(mm); pmd_populate(mm, &_pmd, pgtable); for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { pte_t *pte, entry; if (haddr == (address & PAGE_MASK)) { entry = mk_pte(page, vma->vm_page_prot); entry = maybe_mkwrite(pte_mkdirty(entry), vma); page_add_new_anon_rmap(page, vma, haddr); } else { 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); spin_unlock(&mm->page_table_lock); put_huge_zero_page(); inc_mm_counter(mm, MM_ANONPAGES); mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); ret |= VM_FAULT_WRITE; out: return ret; out_free_page: spin_unlock(&mm->page_table_lock); mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); mem_cgroup_uncharge_page(page); put_page(page); goto out; } 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) { 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_newpage_charge(pages[i], mm, GFP_KERNEL))) { if (pages[i]) put_page(pages[i]); mem_cgroup_uncharge_start(); while (--i >= 0) { mem_cgroup_uncharge_page(pages[i]); put_page(pages[i]); } mem_cgroup_uncharge_end(); kfree(pages); ret |= VM_FAULT_OOM; goto out; } } 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); spin_lock(&mm->page_table_lock); if (unlikely(!pmd_same(*pmd, orig_pmd))) goto out_free_pages; VM_BUG_ON(!PageHead(page)); pmdp_clear_flush(vma, haddr, pmd); /* leave pmd empty until pte is filled */ pgtable = pgtable_trans_huge_withdraw(mm); 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); page_add_new_anon_rmap(pages[i], vma, haddr); 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(&mm->page_table_lock); 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(&mm->page_table_lock); mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); mem_cgroup_uncharge_start(); for (i = 0; i < HPAGE_PMD_NR; i++) { mem_cgroup_uncharge_page(pages[i]); put_page(pages[i]); } mem_cgroup_uncharge_end(); 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) { int ret = 0; struct page *page = NULL, *new_page; unsigned long haddr; unsigned long mmun_start; /* For mmu_notifiers */ unsigned long mmun_end; /* For mmu_notifiers */ VM_BUG_ON(!vma->anon_vma); haddr = address & HPAGE_PMD_MASK; if (is_huge_zero_pmd(orig_pmd)) goto alloc; spin_lock(&mm->page_table_lock); if (unlikely(!pmd_same(*pmd, orig_pmd))) goto out_unlock; page = pmd_page(orig_pmd); VM_BUG_ON(!PageCompound(page) || !PageHead(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_page(page); spin_unlock(&mm->page_table_lock); alloc: if (transparent_hugepage_enabled(vma) && !transparent_hugepage_debug_cow()) new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), vma, haddr, numa_node_id(), 0); else new_page = NULL; if (unlikely(!new_page)) { count_vm_event(THP_FAULT_FALLBACK); if (is_huge_zero_pmd(orig_pmd)) { ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, address, pmd, orig_pmd, haddr); } 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); put_page(page); } goto out; } count_vm_event(THP_FAULT_ALLOC); if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { put_page(new_page); if (page) { split_huge_page(page); put_page(page); } ret |= VM_FAULT_OOM; goto out; } if (is_huge_zero_pmd(orig_pmd)) 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(&mm->page_table_lock); if (page) put_page(page); if (unlikely(!pmd_same(*pmd, orig_pmd))) { spin_unlock(&mm->page_table_lock); mem_cgroup_uncharge_page(new_page); put_page(new_page); goto out_mn; } else { pmd_t entry; entry = mk_huge_pmd(new_page, vma); pmdp_clear_flush(vma, haddr, pmd); page_add_new_anon_rmap(new_page, vma, haddr); set_pmd_at(mm, haddr, pmd, entry); update_mmu_cache_pmd(vma, address, pmd); if (is_huge_zero_pmd(orig_pmd)) { add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); put_huge_zero_page(); } else { VM_BUG_ON(!PageHead(page)); page_remove_rmap(page); put_page(page); } ret |= VM_FAULT_WRITE; } spin_unlock(&mm->page_table_lock); out_mn: mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); out: return ret; out_unlock: spin_unlock(&mm->page_table_lock); 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(&mm->page_table_lock); 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); page = pmd_page(*pmd); VM_BUG_ON(!PageHead(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)); set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); } if ((flags & FOLL_MLOCK) && (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(!PageCompound(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) { struct page *page; unsigned long haddr = addr & HPAGE_PMD_MASK; int target_nid; int current_nid = -1; bool migrated; spin_lock(&mm->page_table_lock); if (unlikely(!pmd_same(pmd, *pmdp))) goto out_unlock; page = pmd_page(pmd); get_page(page); current_nid = page_to_nid(page); count_vm_numa_event(NUMA_HINT_FAULTS); if (current_nid == numa_node_id()) count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); target_nid = mpol_misplaced(page, vma, haddr); if (target_nid == -1) { put_page(page); goto clear_pmdnuma; } /* Acquire the page lock to serialise THP migrations */ spin_unlock(&mm->page_table_lock); lock_page(page); /* Confirm the PTE did not while locked */ spin_lock(&mm->page_table_lock); if (unlikely(!pmd_same(pmd, *pmdp))) { unlock_page(page); put_page(page); goto out_unlock; } spin_unlock(&mm->page_table_lock); /* Migrate the THP to the requested node */ migrated = migrate_misplaced_transhuge_page(mm, vma, pmdp, pmd, addr, page, target_nid); if (!migrated) goto check_same; task_numa_fault(target_nid, HPAGE_PMD_NR, true); return 0; check_same: spin_lock(&mm->page_table_lock); if (unlikely(!pmd_same(pmd, *pmdp))) goto out_unlock; clear_pmdnuma: pmd = pmd_mknonnuma(pmd); set_pmd_at(mm, haddr, pmdp, pmd); VM_BUG_ON(pmd_numa(*pmdp)); update_mmu_cache_pmd(vma, addr, pmdp); out_unlock: spin_unlock(&mm->page_table_lock); if (current_nid != -1) task_numa_fault(current_nid, HPAGE_PMD_NR, false); return 0; } int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr) { int ret = 0; if (__pmd_trans_huge_lock(pmd, vma) == 1) { struct page *page; pgtable_t pgtable; pmd_t orig_pmd; pgtable = pgtable_trans_huge_withdraw(tlb->mm); orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd); tlb_remove_pmd_tlb_entry(tlb, pmd, addr); if (is_huge_zero_pmd(orig_pmd)) { tlb->mm->nr_ptes--; spin_unlock(&tlb->mm->page_table_lock); put_huge_zero_page(); } else { page = pmd_page(orig_pmd); page_remove_rmap(page); VM_BUG_ON(page_mapcount(page) < 0); add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); VM_BUG_ON(!PageHead(page)); tlb->mm->nr_ptes--; spin_unlock(&tlb->mm->page_table_lock); tlb_remove_page(tlb, page); } pte_free(tlb->mm, pgtable); ret = 1; } return ret; } int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, unsigned long end, unsigned char *vec) { int ret = 0; if (__pmd_trans_huge_lock(pmd, vma) == 1) { /* * All logical pages in the range are present * if backed by a huge page. */ spin_unlock(&vma->vm_mm->page_table_lock); memset(vec, 1, (end - addr) >> PAGE_SHIFT); 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) { 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; } ret = __pmd_trans_huge_lock(old_pmd, vma); if (ret == 1) { pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); VM_BUG_ON(!pmd_none(*new_pmd)); set_pmd_at(mm, new_addr, new_pmd, pmd); spin_unlock(&mm->page_table_lock); } out: return ret; } 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; int ret = 0; if (__pmd_trans_huge_lock(pmd, vma) == 1) { pmd_t entry; entry = pmdp_get_and_clear(mm, addr, pmd); if (!prot_numa) { entry = pmd_modify(entry, newprot); BUG_ON(pmd_write(entry)); } else { struct page *page = pmd_page(*pmd); /* only check non-shared pages */ if (page_mapcount(page) == 1 && !pmd_numa(*pmd)) { entry = pmd_mknuma(entry); } } set_pmd_at(mm, addr, pmd, entry); spin_unlock(&vma->vm_mm->page_table_lock); ret = 1; } 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) { spin_lock(&vma->vm_mm->page_table_lock); if (likely(pmd_trans_huge(*pmd))) { if (unlikely(pmd_trans_splitting(*pmd))) { spin_unlock(&vma->vm_mm->page_table_lock); 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(&vma->vm_mm->page_table_lock); return 0; } pmd_t *page_check_address_pmd(struct page *page, struct mm_struct *mm, unsigned long address, enum page_check_address_pmd_flag flag) { pmd_t *pmd, *ret = NULL; if (address & ~HPAGE_PMD_MASK) goto out; pmd = mm_find_pmd(mm, address); if (!pmd) goto out; if (pmd_none(*pmd)) goto out; if (pmd_page(*pmd) != page) goto out; /* * 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 out; if (pmd_trans_huge(*pmd)) { VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && !pmd_trans_splitting(*pmd)); ret = pmd; } out: return ret; } static int __split_huge_page_splitting(struct page *page, struct vm_area_struct *vma, unsigned long address) { struct mm_struct *mm = vma->vm_mm; 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); spin_lock(&mm->page_table_lock); pmd = page_check_address_pmd(page, mm, address, PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); 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(&mm->page_table_lock); 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(); /* * 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))); 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_nid_xchg_last(page_tail, page_nid_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); __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); 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; pmd_t *pmd, _pmd; int ret = 0, i; pgtable_t pgtable; unsigned long haddr; spin_lock(&mm->page_table_lock); pmd = page_check_address_pmd(page, mm, address, PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); if (pmd) { pgtable = pgtable_trans_huge_withdraw(mm); pmd_populate(mm, &_pmd, pgtable); haddr = address; for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { pte_t *pte, entry; BUG_ON(PageCompound(page+i)); entry = mk_pte(page + i, vma->vm_page_prot); entry = maybe_mkwrite(pte_mkdirty(entry), vma); if (!pmd_write(*pmd)) entry = pte_wrprotect(entry); else BUG_ON(page_mapcount(page) != 1); if (!pmd_young(*pmd)) entry = pte_mkold(entry); if (pmd_numa(*pmd)) entry = pte_mknuma(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(&mm->page_table_lock); 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)) printk(KERN_ERR "mapcount %d page_mapcount %d\n", mapcount, page_mapcount(page)); BUG_ON(mapcount != page_mapcount(page)); __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) printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", mapcount, mapcount2, page_mapcount(page)); BUG_ON(mapcount != mapcount2); } /* * 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_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE) int hugepage_madvise(struct vm_area_struct *vma, unsigned long *vm_flags, int advice) { struct mm_struct *mm = vma->vm_mm; switch (advice) { case MADV_HUGEPAGE: /* * Be somewhat over-protective like KSM for now! */ if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) return -EINVAL; if (mm->def_flags & VM_NOHUGEPAGE) 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))) 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 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(khugepaged_test_exit(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 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); hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; hend = vma->vm_end & HPAGE_PMD_MASK; if (hstart < hend) return khugepaged_enter(vma); 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)) 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 referenced = 0, none = 0; for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++, address += PAGE_SIZE) { pte_t pteval = *_pte; if (pte_none(pteval)) { if (++none <= khugepaged_max_ptes_none) continue; else goto out; } if (!pte_present(pteval) || !pte_write(pteval)) goto out; page = vm_normal_page(vma, address, pteval); if (unlikely(!page)) goto out; VM_BUG_ON(PageCompound(page)); BUG_ON(!PageAnon(page)); VM_BUG_ON(!PageSwapBacked(page)); /* cannot use mapcount: can't collapse if there's a gup pin */ if (page_count(page) != 1) goto out; /* * 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; /* * 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(!PageLocked(page)); VM_BUG_ON(PageLRU(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 = 1; } if (likely(referenced)) 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)) { clear_user_highpage(page, address); add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); } else { src_page = pte_page(pteval); copy_user_highpage(page, src_page, address, vma); VM_BUG_ON(page_mapcount(src_page) != 1); 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)); } #ifdef CONFIG_NUMA 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, struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, int node) { VM_BUG_ON(*hpage); /* * Allocate the page while the vma is still valid and under * the mmap_sem read mode so there is no memory allocation * later when we take the mmap_sem in write mode. This is more * friendly behavior (OTOH it may actually hide bugs) to * filesystems in userland with daemons allocating memory in * the userland I/O paths. Allocating memory with the * mmap_sem in read mode is good idea also to allow greater * scalability. */ *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address, node, __GFP_OTHER_NODE); /* * After allocating the hugepage, release the mmap_sem read lock in * preparation for taking it in write mode. */ up_read(&mm->mmap_sem); 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 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, 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->vm_flags & VM_NO_THP); 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 *ptl; int isolated; unsigned long hstart, hend; unsigned long mmun_start; /* For mmu_notifiers */ unsigned long mmun_end; /* For mmu_notifiers */ VM_BUG_ON(address & ~HPAGE_PMD_MASK); /* release the mmap_sem read lock. */ new_page = khugepaged_alloc_page(hpage, mm, vma, address, node); if (!new_page) return; if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) 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); 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; if (pmd_trans_huge(*pmd)) goto out; anon_vma_lock_write(vma->anon_vma); pte = pte_offset_map(pmd, address); ptl = pte_lockptr(mm, pmd); mmun_start = address; mmun_end = address + HPAGE_PMD_SIZE; mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); spin_lock(&mm->page_table_lock); /* 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(&mm->page_table_lock); mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); spin_lock(ptl); isolated = __collapse_huge_page_isolate(vma, address, pte); spin_unlock(ptl); if (unlikely(!isolated)) { pte_unmap(pte); spin_lock(&mm->page_table_lock); BUG_ON(!pmd_none(*pmd)); set_pmd_at(mm, address, pmd, _pmd); spin_unlock(&mm->page_table_lock); 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, ptl); pte_unmap(pte); __SetPageUptodate(new_page); pgtable = pmd_pgtable(_pmd); _pmd = mk_huge_pmd(new_page, 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(&mm->page_table_lock); BUG_ON(!pmd_none(*pmd)); page_add_new_anon_rmap(new_page, vma, address); set_pmd_at(mm, address, pmd, _pmd); update_mmu_cache_pmd(vma, address, pmd); pgtable_trans_huge_deposit(mm, pgtable); spin_unlock(&mm->page_table_lock); *hpage = NULL; khugepaged_pages_collapsed++; out_up_write: up_write(&mm->mmap_sem); return; out: mem_cgroup_uncharge_page(new_page); 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, referenced = 0, none = 0; struct page *page; unsigned long _address; spinlock_t *ptl; int node = NUMA_NO_NODE; VM_BUG_ON(address & ~HPAGE_PMD_MASK); pmd = mm_find_pmd(mm, address); if (!pmd) goto out; if (pmd_trans_huge(*pmd)) goto out; 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)) { if (++none <= khugepaged_max_ptes_none) continue; else goto out_unmap; } if (!pte_present(pteval) || !pte_write(pteval)) goto out_unmap; page = vm_normal_page(vma, _address, pteval); if (unlikely(!page)) goto out_unmap; /* * Chose the node of the first page. This could * be more sophisticated and look at more pages, * but isn't for now. */ if (node == NUMA_NO_NODE) node = page_to_nid(page); VM_BUG_ON(PageCompound(page)); if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) goto out_unmap; /* cannot use mapcount: can't collapse if there's a gup pin */ if (page_count(page) != 1) goto out_unmap; if (pte_young(pteval) || PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm, address)) referenced = 1; } if (referenced) ret = 1; out_unmap: pte_unmap_unlock(pte, ptl); if (ret) /* 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, 19); 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(vma, haddr, pmd); /* leave pmd empty until pte is filled */ pgtable = pgtable_trans_huge_withdraw(mm); 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) { 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; mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); spin_lock(&mm->page_table_lock); if (unlikely(!pmd_trans_huge(*pmd))) { spin_unlock(&mm->page_table_lock); 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(&mm->page_table_lock); mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); return; } page = pmd_page(*pmd); VM_BUG_ON(!page_count(page)); get_page(page); spin_unlock(&mm->page_table_lock); mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); split_huge_page(page); put_page(page); BUG_ON(pmd_trans_huge(*pmd)); } 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) { pmd_t *pmd; VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); pmd = mm_find_pmd(mm, address); if (!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); } }