| // SPDX-License-Identifier: GPL-2.0 |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/mm.h> |
| #include <linux/sched.h> |
| #include <linux/sched/mm.h> |
| #include <linux/sched/coredump.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/rmap.h> |
| #include <linux/swap.h> |
| #include <linux/mm_inline.h> |
| #include <linux/kthread.h> |
| #include <linux/khugepaged.h> |
| #include <linux/freezer.h> |
| #include <linux/mman.h> |
| #include <linux/hashtable.h> |
| #include <linux/userfaultfd_k.h> |
| #include <linux/page_idle.h> |
| #include <linux/swapops.h> |
| #include <linux/shmem_fs.h> |
| |
| #include <asm/tlb.h> |
| #include <asm/pgalloc.h> |
| #include "internal.h" |
| |
| enum scan_result { |
| SCAN_FAIL, |
| SCAN_SUCCEED, |
| SCAN_PMD_NULL, |
| SCAN_EXCEED_NONE_PTE, |
| SCAN_PTE_NON_PRESENT, |
| SCAN_PAGE_RO, |
| SCAN_LACK_REFERENCED_PAGE, |
| SCAN_PAGE_NULL, |
| SCAN_SCAN_ABORT, |
| SCAN_PAGE_COUNT, |
| SCAN_PAGE_LRU, |
| SCAN_PAGE_LOCK, |
| SCAN_PAGE_ANON, |
| SCAN_PAGE_COMPOUND, |
| SCAN_ANY_PROCESS, |
| SCAN_VMA_NULL, |
| SCAN_VMA_CHECK, |
| SCAN_ADDRESS_RANGE, |
| SCAN_SWAP_CACHE_PAGE, |
| SCAN_DEL_PAGE_LRU, |
| SCAN_ALLOC_HUGE_PAGE_FAIL, |
| SCAN_CGROUP_CHARGE_FAIL, |
| SCAN_EXCEED_SWAP_PTE, |
| SCAN_TRUNCATED, |
| }; |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/huge_memory.h> |
| |
| /* default scan 8*512 pte (or vmas) every 30 second */ |
| static unsigned int khugepaged_pages_to_scan __read_mostly; |
| 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 unsigned long khugepaged_sleep_expire; |
| 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; |
| static unsigned int khugepaged_max_ptes_swap __read_mostly; |
| |
| #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), |
| }; |
| |
| #ifdef CONFIG_SYSFS |
| 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; |
| khugepaged_sleep_expire = 0; |
| 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; |
| khugepaged_sleep_expire = 0; |
| 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_hugepage_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_hugepage_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 ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, |
| struct kobj_attribute *attr, |
| char *buf) |
| { |
| return sprintf(buf, "%u\n", khugepaged_max_ptes_swap); |
| } |
| |
| static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, |
| struct kobj_attribute *attr, |
| const char *buf, size_t count) |
| { |
| int err; |
| unsigned long max_ptes_swap; |
| |
| err = kstrtoul(buf, 10, &max_ptes_swap); |
| if (err || max_ptes_swap > HPAGE_PMD_NR-1) |
| return -EINVAL; |
| |
| khugepaged_max_ptes_swap = max_ptes_swap; |
| |
| return count; |
| } |
| |
| static struct kobj_attribute khugepaged_max_ptes_swap_attr = |
| __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, |
| khugepaged_max_ptes_swap_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, |
| &khugepaged_max_ptes_swap_attr.attr, |
| NULL, |
| }; |
| |
| struct attribute_group khugepaged_attr_group = { |
| .attrs = khugepaged_attr, |
| .name = "khugepaged", |
| }; |
| #endif /* CONFIG_SYSFS */ |
| |
| #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB) |
| |
| 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 |
| *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 (!(*vm_flags & VM_NO_KHUGEPAGED) && |
| khugepaged_enter_vma_merge(vma, *vm_flags)) |
| return -ENOMEM; |
| break; |
| case MADV_NOHUGEPAGE: |
| *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; |
| } |
| |
| int __init khugepaged_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; |
| |
| khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; |
| khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; |
| khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; |
| |
| return 0; |
| } |
| |
| void __init khugepaged_destroy(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; |
| } |
| |
| static bool hugepage_vma_check(struct vm_area_struct *vma, |
| unsigned long vm_flags) |
| { |
| if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || |
| (vm_flags & VM_NOHUGEPAGE) || |
| test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) |
| return false; |
| if (shmem_file(vma->vm_file)) { |
| if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) |
| return false; |
| return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, |
| HPAGE_PMD_NR); |
| } |
| if (!vma->anon_vma || vma->vm_ops) |
| return false; |
| if (is_vma_temporary_stack(vma)) |
| return false; |
| return !(vm_flags & VM_NO_KHUGEPAGED); |
| } |
| |
| 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); |
| |
| mmgrab(mm); |
| 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; |
| |
| /* |
| * khugepaged does not yet work on non-shmem files or special |
| * mappings. And file-private shmem THP is not supported. |
| */ |
| if (!hugepage_vma_check(vma, vm_flags)) |
| return 0; |
| |
| 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) |
| { |
| dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); |
| 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 = NULL; |
| pte_t *_pte; |
| int none_or_zero = 0, result = 0, referenced = 0; |
| bool writable = false; |
| |
| for (_pte = pte; _pte < pte+HPAGE_PMD_NR; |
| _pte++, address += PAGE_SIZE) { |
| pte_t pteval = *_pte; |
| if (pte_none(pteval) || (pte_present(pteval) && |
| is_zero_pfn(pte_pfn(pteval)))) { |
| if (!userfaultfd_armed(vma) && |
| ++none_or_zero <= khugepaged_max_ptes_none) { |
| continue; |
| } else { |
| result = SCAN_EXCEED_NONE_PTE; |
| goto out; |
| } |
| } |
| if (!pte_present(pteval)) { |
| result = SCAN_PTE_NON_PRESENT; |
| goto out; |
| } |
| page = vm_normal_page(vma, address, pteval); |
| if (unlikely(!page)) { |
| result = SCAN_PAGE_NULL; |
| goto out; |
| } |
| |
| /* TODO: teach khugepaged to collapse THP mapped with pte */ |
| if (PageCompound(page)) { |
| result = SCAN_PAGE_COMPOUND; |
| goto out; |
| } |
| |
| VM_BUG_ON_PAGE(!PageAnon(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)) { |
| result = SCAN_PAGE_LOCK; |
| 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); |
| result = SCAN_PAGE_COUNT; |
| goto out; |
| } |
| if (pte_write(pteval)) { |
| writable = true; |
| } else { |
| if (PageSwapCache(page) && |
| !reuse_swap_page(page, NULL)) { |
| unlock_page(page); |
| result = SCAN_SWAP_CACHE_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); |
| result = SCAN_DEL_PAGE_LRU; |
| goto out; |
| } |
| inc_node_page_state(page, |
| NR_ISOLATED_ANON + page_is_file_cache(page)); |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(PageLRU(page), page); |
| |
| /* There should be enough young pte to collapse the page */ |
| if (pte_young(pteval) || |
| page_is_young(page) || PageReferenced(page) || |
| mmu_notifier_test_young(vma->vm_mm, address)) |
| referenced++; |
| } |
| if (likely(writable)) { |
| if (likely(referenced)) { |
| result = SCAN_SUCCEED; |
| trace_mm_collapse_huge_page_isolate(page, none_or_zero, |
| referenced, writable, result); |
| return 1; |
| } |
| } else { |
| result = SCAN_PAGE_RO; |
| } |
| |
| out: |
| release_pte_pages(pte, _pte); |
| trace_mm_collapse_huge_page_isolate(page, none_or_zero, |
| referenced, writable, result); |
| 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++, page++, address += PAGE_SIZE) { |
| 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, false); |
| spin_unlock(ptl); |
| free_page_and_swap_cache(src_page); |
| } |
| } |
| } |
| |
| static void khugepaged_alloc_sleep(void) |
| { |
| DEFINE_WAIT(wait); |
| |
| add_wait_queue(&khugepaged_wait, &wait); |
| freezable_schedule_timeout_interruptible( |
| msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); |
| remove_wait_queue(&khugepaged_wait, &wait); |
| } |
| |
| static int khugepaged_node_load[MAX_NUMNODES]; |
| |
| static bool khugepaged_scan_abort(int nid) |
| { |
| int i; |
| |
| /* |
| * If node_reclaim_mode is disabled, then no extra effort is made to |
| * allocate memory locally. |
| */ |
| if (!node_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; |
| } |
| |
| /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ |
| static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) |
| { |
| return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; |
| } |
| |
| #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, int node) |
| { |
| VM_BUG_ON_PAGE(*hpage, *hpage); |
| |
| *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); |
| if (unlikely(!*hpage)) { |
| count_vm_event(THP_COLLAPSE_ALLOC_FAILED); |
| *hpage = ERR_PTR(-ENOMEM); |
| return NULL; |
| } |
| |
| prep_transhuge_page(*hpage); |
| count_vm_event(THP_COLLAPSE_ALLOC); |
| return *hpage; |
| } |
| #else |
| static int khugepaged_find_target_node(void) |
| { |
| return 0; |
| } |
| |
| static inline struct page *alloc_khugepaged_hugepage(void) |
| { |
| struct page *page; |
| |
| page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), |
| HPAGE_PMD_ORDER); |
| if (page) |
| prep_transhuge_page(page); |
| return page; |
| } |
| |
| static struct page *khugepaged_alloc_hugepage(bool *wait) |
| { |
| struct page *hpage; |
| |
| do { |
| hpage = alloc_khugepaged_hugepage(); |
| 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, int node) |
| { |
| VM_BUG_ON(!*hpage); |
| |
| return *hpage; |
| } |
| #endif |
| |
| /* |
| * If mmap_sem temporarily dropped, revalidate vma |
| * before taking mmap_sem. |
| * Return 0 if succeeds, otherwise return none-zero |
| * value (scan code). |
| */ |
| |
| static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, |
| struct vm_area_struct **vmap) |
| { |
| struct vm_area_struct *vma; |
| unsigned long hstart, hend; |
| |
| if (unlikely(khugepaged_test_exit(mm))) |
| return SCAN_ANY_PROCESS; |
| |
| *vmap = vma = find_vma(mm, address); |
| if (!vma) |
| return SCAN_VMA_NULL; |
| |
| 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) |
| return SCAN_ADDRESS_RANGE; |
| if (!hugepage_vma_check(vma, vma->vm_flags)) |
| return SCAN_VMA_CHECK; |
| return 0; |
| } |
| |
| /* |
| * Bring missing pages in from swap, to complete THP collapse. |
| * Only done if khugepaged_scan_pmd believes it is worthwhile. |
| * |
| * Called and returns without pte mapped or spinlocks held, |
| * but with mmap_sem held to protect against vma changes. |
| */ |
| |
| static bool __collapse_huge_page_swapin(struct mm_struct *mm, |
| struct vm_area_struct *vma, |
| unsigned long address, pmd_t *pmd, |
| int referenced) |
| { |
| int swapped_in = 0; |
| vm_fault_t ret = 0; |
| struct vm_fault vmf = { |
| .vma = vma, |
| .address = address, |
| .flags = FAULT_FLAG_ALLOW_RETRY, |
| .pmd = pmd, |
| .pgoff = linear_page_index(vma, address), |
| }; |
| |
| /* we only decide to swapin, if there is enough young ptes */ |
| if (referenced < HPAGE_PMD_NR/2) { |
| trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
| return false; |
| } |
| vmf.pte = pte_offset_map(pmd, address); |
| for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; |
| vmf.pte++, vmf.address += PAGE_SIZE) { |
| vmf.orig_pte = *vmf.pte; |
| if (!is_swap_pte(vmf.orig_pte)) |
| continue; |
| swapped_in++; |
| ret = do_swap_page(&vmf); |
| |
| /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ |
| if (ret & VM_FAULT_RETRY) { |
| down_read(&mm->mmap_sem); |
| if (hugepage_vma_revalidate(mm, address, &vmf.vma)) { |
| /* vma is no longer available, don't continue to swapin */ |
| trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
| return false; |
| } |
| /* check if the pmd is still valid */ |
| if (mm_find_pmd(mm, address) != pmd) { |
| trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
| return false; |
| } |
| } |
| if (ret & VM_FAULT_ERROR) { |
| trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
| return false; |
| } |
| /* pte is unmapped now, we need to map it */ |
| vmf.pte = pte_offset_map(pmd, vmf.address); |
| } |
| vmf.pte--; |
| pte_unmap(vmf.pte); |
| trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); |
| return true; |
| } |
| |
| static void collapse_huge_page(struct mm_struct *mm, |
| unsigned long address, |
| struct page **hpage, |
| int node, int referenced) |
| { |
| pmd_t *pmd, _pmd; |
| pte_t *pte; |
| pgtable_t pgtable; |
| struct page *new_page; |
| spinlock_t *pmd_ptl, *pte_ptl; |
| int isolated = 0, result = 0; |
| struct mem_cgroup *memcg; |
| struct vm_area_struct *vma; |
| struct mmu_notifier_range range; |
| gfp_t gfp; |
| |
| VM_BUG_ON(address & ~HPAGE_PMD_MASK); |
| |
| /* Only allocate from the target node */ |
| gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
| |
| /* |
| * 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); |
| new_page = khugepaged_alloc_page(hpage, gfp, node); |
| if (!new_page) { |
| result = SCAN_ALLOC_HUGE_PAGE_FAIL; |
| goto out_nolock; |
| } |
| |
| if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { |
| result = SCAN_CGROUP_CHARGE_FAIL; |
| goto out_nolock; |
| } |
| |
| down_read(&mm->mmap_sem); |
| result = hugepage_vma_revalidate(mm, address, &vma); |
| if (result) { |
| mem_cgroup_cancel_charge(new_page, memcg, true); |
| up_read(&mm->mmap_sem); |
| goto out_nolock; |
| } |
| |
| pmd = mm_find_pmd(mm, address); |
| if (!pmd) { |
| result = SCAN_PMD_NULL; |
| mem_cgroup_cancel_charge(new_page, memcg, true); |
| up_read(&mm->mmap_sem); |
| goto out_nolock; |
| } |
| |
| /* |
| * __collapse_huge_page_swapin always returns with mmap_sem locked. |
| * If it fails, we release mmap_sem and jump out_nolock. |
| * Continuing to collapse causes inconsistency. |
| */ |
| if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) { |
| mem_cgroup_cancel_charge(new_page, memcg, true); |
| up_read(&mm->mmap_sem); |
| goto out_nolock; |
| } |
| |
| up_read(&mm->mmap_sem); |
| /* |
| * Prevent all access to pagetables with the exception of |
| * gup_fast later handled by the ptep_clear_flush and the VM |
| * handled by the anon_vma lock + PG_lock. |
| */ |
| down_write(&mm->mmap_sem); |
| result = hugepage_vma_revalidate(mm, address, &vma); |
| if (result) |
| goto out; |
| /* check if the pmd is still valid */ |
| if (mm_find_pmd(mm, address) != pmd) |
| goto out; |
| |
| anon_vma_lock_write(vma->anon_vma); |
| |
| pte = pte_offset_map(pmd, address); |
| pte_ptl = pte_lockptr(mm, pmd); |
| |
| mmu_notifier_range_init(&range, mm, address, address + HPAGE_PMD_SIZE); |
| mmu_notifier_invalidate_range_start(&range); |
| 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_collapse_flush(vma, address, pmd); |
| spin_unlock(pmd_ptl); |
| mmu_notifier_invalidate_range_end(&range); |
| |
| 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); |
| result = SCAN_FAIL; |
| 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, true); |
| mem_cgroup_commit_charge(new_page, memcg, false, true); |
| count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1); |
| 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++; |
| result = SCAN_SUCCEED; |
| out_up_write: |
| up_write(&mm->mmap_sem); |
| out_nolock: |
| trace_mm_collapse_huge_page(mm, isolated, result); |
| return; |
| out: |
| mem_cgroup_cancel_charge(new_page, memcg, true); |
| 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, result = 0, referenced = 0; |
| struct page *page = NULL; |
| unsigned long _address; |
| spinlock_t *ptl; |
| int node = NUMA_NO_NODE, unmapped = 0; |
| bool writable = false; |
| |
| VM_BUG_ON(address & ~HPAGE_PMD_MASK); |
| |
| pmd = mm_find_pmd(mm, address); |
| if (!pmd) { |
| result = SCAN_PMD_NULL; |
| 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 (is_swap_pte(pteval)) { |
| if (++unmapped <= khugepaged_max_ptes_swap) { |
| continue; |
| } else { |
| result = SCAN_EXCEED_SWAP_PTE; |
| goto out_unmap; |
| } |
| } |
| if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { |
| if (!userfaultfd_armed(vma) && |
| ++none_or_zero <= khugepaged_max_ptes_none) { |
| continue; |
| } else { |
| result = SCAN_EXCEED_NONE_PTE; |
| goto out_unmap; |
| } |
| } |
| if (!pte_present(pteval)) { |
| result = SCAN_PTE_NON_PRESENT; |
| goto out_unmap; |
| } |
| if (pte_write(pteval)) |
| writable = true; |
| |
| page = vm_normal_page(vma, _address, pteval); |
| if (unlikely(!page)) { |
| result = SCAN_PAGE_NULL; |
| goto out_unmap; |
| } |
| |
| /* TODO: teach khugepaged to collapse THP mapped with pte */ |
| if (PageCompound(page)) { |
| result = SCAN_PAGE_COMPOUND; |
| 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)) { |
| result = SCAN_SCAN_ABORT; |
| goto out_unmap; |
| } |
| khugepaged_node_load[node]++; |
| if (!PageLRU(page)) { |
| result = SCAN_PAGE_LRU; |
| goto out_unmap; |
| } |
| if (PageLocked(page)) { |
| result = SCAN_PAGE_LOCK; |
| goto out_unmap; |
| } |
| if (!PageAnon(page)) { |
| result = SCAN_PAGE_ANON; |
| 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)) { |
| result = SCAN_PAGE_COUNT; |
| goto out_unmap; |
| } |
| if (pte_young(pteval) || |
| page_is_young(page) || PageReferenced(page) || |
| mmu_notifier_test_young(vma->vm_mm, address)) |
| referenced++; |
| } |
| if (writable) { |
| if (referenced) { |
| result = SCAN_SUCCEED; |
| ret = 1; |
| } else { |
| result = SCAN_LACK_REFERENCED_PAGE; |
| } |
| } else { |
| result = SCAN_PAGE_RO; |
| } |
| 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, node, referenced); |
| } |
| out: |
| trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, |
| none_or_zero, result, unmapped); |
| return ret; |
| } |
| |
| static void collect_mm_slot(struct mm_slot *mm_slot) |
| { |
| struct mm_struct *mm = mm_slot->mm; |
| |
| lockdep_assert_held(&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); |
| } |
| } |
| |
| #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) |
| static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) |
| { |
| struct vm_area_struct *vma; |
| unsigned long addr; |
| pmd_t *pmd, _pmd; |
| |
| i_mmap_lock_write(mapping); |
| vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { |
| /* probably overkill */ |
| if (vma->anon_vma) |
| continue; |
| addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
| if (addr & ~HPAGE_PMD_MASK) |
| continue; |
| if (vma->vm_end < addr + HPAGE_PMD_SIZE) |
| continue; |
| pmd = mm_find_pmd(vma->vm_mm, addr); |
| if (!pmd) |
| continue; |
| /* |
| * We need exclusive mmap_sem to retract page table. |
| * If trylock fails we would end up with pte-mapped THP after |
| * re-fault. Not ideal, but it's more important to not disturb |
| * the system too much. |
| */ |
| if (down_write_trylock(&vma->vm_mm->mmap_sem)) { |
| spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd); |
| /* assume page table is clear */ |
| _pmd = pmdp_collapse_flush(vma, addr, pmd); |
| spin_unlock(ptl); |
| up_write(&vma->vm_mm->mmap_sem); |
| mm_dec_nr_ptes(vma->vm_mm); |
| pte_free(vma->vm_mm, pmd_pgtable(_pmd)); |
| } |
| } |
| i_mmap_unlock_write(mapping); |
| } |
| |
| /** |
| * collapse_shmem - collapse small tmpfs/shmem pages into huge one. |
| * |
| * Basic scheme is simple, details are more complex: |
| * - allocate and lock a new huge page; |
| * - scan page cache replacing old pages with the new one |
| * + swap in pages if necessary; |
| * + fill in gaps; |
| * + keep old pages around in case rollback is required; |
| * - if replacing succeeds: |
| * + copy data over; |
| * + free old pages; |
| * + unlock huge page; |
| * - if replacing failed; |
| * + put all pages back and unfreeze them; |
| * + restore gaps in the page cache; |
| * + unlock and free huge page; |
| */ |
| static void collapse_shmem(struct mm_struct *mm, |
| struct address_space *mapping, pgoff_t start, |
| struct page **hpage, int node) |
| { |
| gfp_t gfp; |
| struct page *new_page; |
| struct mem_cgroup *memcg; |
| pgoff_t index, end = start + HPAGE_PMD_NR; |
| LIST_HEAD(pagelist); |
| XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); |
| int nr_none = 0, result = SCAN_SUCCEED; |
| |
| VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); |
| |
| /* Only allocate from the target node */ |
| gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
| |
| new_page = khugepaged_alloc_page(hpage, gfp, node); |
| if (!new_page) { |
| result = SCAN_ALLOC_HUGE_PAGE_FAIL; |
| goto out; |
| } |
| |
| if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { |
| result = SCAN_CGROUP_CHARGE_FAIL; |
| goto out; |
| } |
| |
| /* This will be less messy when we use multi-index entries */ |
| do { |
| xas_lock_irq(&xas); |
| xas_create_range(&xas); |
| if (!xas_error(&xas)) |
| break; |
| xas_unlock_irq(&xas); |
| if (!xas_nomem(&xas, GFP_KERNEL)) { |
| mem_cgroup_cancel_charge(new_page, memcg, true); |
| result = SCAN_FAIL; |
| goto out; |
| } |
| } while (1); |
| |
| __SetPageLocked(new_page); |
| __SetPageSwapBacked(new_page); |
| new_page->index = start; |
| new_page->mapping = mapping; |
| |
| /* |
| * At this point the new_page is locked and not up-to-date. |
| * It's safe to insert it into the page cache, because nobody would |
| * be able to map it or use it in another way until we unlock it. |
| */ |
| |
| xas_set(&xas, start); |
| for (index = start; index < end; index++) { |
| struct page *page = xas_next(&xas); |
| |
| VM_BUG_ON(index != xas.xa_index); |
| if (!page) { |
| /* |
| * Stop if extent has been truncated or hole-punched, |
| * and is now completely empty. |
| */ |
| if (index == start) { |
| if (!xas_next_entry(&xas, end - 1)) { |
| result = SCAN_TRUNCATED; |
| goto xa_locked; |
| } |
| xas_set(&xas, index); |
| } |
| if (!shmem_charge(mapping->host, 1)) { |
| result = SCAN_FAIL; |
| goto xa_locked; |
| } |
| xas_store(&xas, new_page); |
| nr_none++; |
| continue; |
| } |
| |
| if (xa_is_value(page) || !PageUptodate(page)) { |
| xas_unlock_irq(&xas); |
| /* swap in or instantiate fallocated page */ |
| if (shmem_getpage(mapping->host, index, &page, |
| SGP_NOHUGE)) { |
| result = SCAN_FAIL; |
| goto xa_unlocked; |
| } |
| } else if (trylock_page(page)) { |
| get_page(page); |
| xas_unlock_irq(&xas); |
| } else { |
| result = SCAN_PAGE_LOCK; |
| goto xa_locked; |
| } |
| |
| /* |
| * The page must be locked, so we can drop the i_pages lock |
| * without racing with truncate. |
| */ |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(!PageUptodate(page), page); |
| |
| /* |
| * If file was truncated then extended, or hole-punched, before |
| * we locked the first page, then a THP might be there already. |
| */ |
| if (PageTransCompound(page)) { |
| result = SCAN_PAGE_COMPOUND; |
| goto out_unlock; |
| } |
| |
| if (page_mapping(page) != mapping) { |
| result = SCAN_TRUNCATED; |
| goto out_unlock; |
| } |
| |
| if (isolate_lru_page(page)) { |
| result = SCAN_DEL_PAGE_LRU; |
| goto out_unlock; |
| } |
| |
| if (page_mapped(page)) |
| unmap_mapping_pages(mapping, index, 1, false); |
| |
| xas_lock_irq(&xas); |
| xas_set(&xas, index); |
| |
| VM_BUG_ON_PAGE(page != xas_load(&xas), page); |
| VM_BUG_ON_PAGE(page_mapped(page), page); |
| |
| /* |
| * The page is expected to have page_count() == 3: |
| * - we hold a pin on it; |
| * - one reference from page cache; |
| * - one from isolate_lru_page; |
| */ |
| if (!page_ref_freeze(page, 3)) { |
| result = SCAN_PAGE_COUNT; |
| xas_unlock_irq(&xas); |
| putback_lru_page(page); |
| goto out_unlock; |
| } |
| |
| /* |
| * Add the page to the list to be able to undo the collapse if |
| * something go wrong. |
| */ |
| list_add_tail(&page->lru, &pagelist); |
| |
| /* Finally, replace with the new page. */ |
| xas_store(&xas, new_page); |
| continue; |
| out_unlock: |
| unlock_page(page); |
| put_page(page); |
| goto xa_unlocked; |
| } |
| |
| __inc_node_page_state(new_page, NR_SHMEM_THPS); |
| if (nr_none) { |
| struct zone *zone = page_zone(new_page); |
| |
| __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none); |
| __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none); |
| } |
| |
| xa_locked: |
| xas_unlock_irq(&xas); |
| xa_unlocked: |
| |
| if (result == SCAN_SUCCEED) { |
| struct page *page, *tmp; |
| |
| /* |
| * Replacing old pages with new one has succeeded, now we |
| * need to copy the content and free the old pages. |
| */ |
| index = start; |
| list_for_each_entry_safe(page, tmp, &pagelist, lru) { |
| while (index < page->index) { |
| clear_highpage(new_page + (index % HPAGE_PMD_NR)); |
| index++; |
| } |
| copy_highpage(new_page + (page->index % HPAGE_PMD_NR), |
| page); |
| list_del(&page->lru); |
| page->mapping = NULL; |
| page_ref_unfreeze(page, 1); |
| ClearPageActive(page); |
| ClearPageUnevictable(page); |
| unlock_page(page); |
| put_page(page); |
| index++; |
| } |
| while (index < end) { |
| clear_highpage(new_page + (index % HPAGE_PMD_NR)); |
| index++; |
| } |
| |
| SetPageUptodate(new_page); |
| page_ref_add(new_page, HPAGE_PMD_NR - 1); |
| set_page_dirty(new_page); |
| mem_cgroup_commit_charge(new_page, memcg, false, true); |
| count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1); |
| lru_cache_add_anon(new_page); |
| |
| /* |
| * Remove pte page tables, so we can re-fault the page as huge. |
| */ |
| retract_page_tables(mapping, start); |
| *hpage = NULL; |
| |
| khugepaged_pages_collapsed++; |
| } else { |
| struct page *page; |
| |
| /* Something went wrong: roll back page cache changes */ |
| xas_lock_irq(&xas); |
| mapping->nrpages -= nr_none; |
| shmem_uncharge(mapping->host, nr_none); |
| |
| xas_set(&xas, start); |
| xas_for_each(&xas, page, end - 1) { |
| page = list_first_entry_or_null(&pagelist, |
| struct page, lru); |
| if (!page || xas.xa_index < page->index) { |
| if (!nr_none) |
| break; |
| nr_none--; |
| /* Put holes back where they were */ |
| xas_store(&xas, NULL); |
| continue; |
| } |
| |
| VM_BUG_ON_PAGE(page->index != xas.xa_index, page); |
| |
| /* Unfreeze the page. */ |
| list_del(&page->lru); |
| page_ref_unfreeze(page, 2); |
| xas_store(&xas, page); |
| xas_pause(&xas); |
| xas_unlock_irq(&xas); |
| unlock_page(page); |
| putback_lru_page(page); |
| xas_lock_irq(&xas); |
| } |
| VM_BUG_ON(nr_none); |
| xas_unlock_irq(&xas); |
| |
| mem_cgroup_cancel_charge(new_page, memcg, true); |
| new_page->mapping = NULL; |
| } |
| |
| unlock_page(new_page); |
| out: |
| VM_BUG_ON(!list_empty(&pagelist)); |
| /* TODO: tracepoints */ |
| } |
| |
| static void khugepaged_scan_shmem(struct mm_struct *mm, |
| struct address_space *mapping, |
| pgoff_t start, struct page **hpage) |
| { |
| struct page *page = NULL; |
| XA_STATE(xas, &mapping->i_pages, start); |
| int present, swap; |
| int node = NUMA_NO_NODE; |
| int result = SCAN_SUCCEED; |
| |
| present = 0; |
| swap = 0; |
| memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); |
| rcu_read_lock(); |
| xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) { |
| if (xas_retry(&xas, page)) |
| continue; |
| |
| if (xa_is_value(page)) { |
| if (++swap > khugepaged_max_ptes_swap) { |
| result = SCAN_EXCEED_SWAP_PTE; |
| break; |
| } |
| continue; |
| } |
| |
| if (PageTransCompound(page)) { |
| result = SCAN_PAGE_COMPOUND; |
| break; |
| } |
| |
| node = page_to_nid(page); |
| if (khugepaged_scan_abort(node)) { |
| result = SCAN_SCAN_ABORT; |
| break; |
| } |
| khugepaged_node_load[node]++; |
| |
| if (!PageLRU(page)) { |
| result = SCAN_PAGE_LRU; |
| break; |
| } |
| |
| if (page_count(page) != 1 + page_mapcount(page)) { |
| result = SCAN_PAGE_COUNT; |
| break; |
| } |
| |
| /* |
| * We probably should check if the page is referenced here, but |
| * nobody would transfer pte_young() to PageReferenced() for us. |
| * And rmap walk here is just too costly... |
| */ |
| |
| present++; |
| |
| if (need_resched()) { |
| xas_pause(&xas); |
| cond_resched_rcu(); |
| } |
| } |
| rcu_read_unlock(); |
| |
| if (result == SCAN_SUCCEED) { |
| if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { |
| result = SCAN_EXCEED_NONE_PTE; |
| } else { |
| node = khugepaged_find_target_node(); |
| collapse_shmem(mm, mapping, start, hpage, node); |
| } |
| } |
| |
| /* TODO: tracepoints */ |
| } |
| #else |
| static void khugepaged_scan_shmem(struct mm_struct *mm, |
| struct address_space *mapping, |
| pgoff_t start, struct page **hpage) |
| { |
| BUILD_BUG(); |
| } |
| #endif |
| |
| 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); |
| lockdep_assert_held(&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; |
| /* |
| * Don't wait for semaphore (to avoid long wait times). Just move to |
| * the next mm on the list. |
| */ |
| vma = NULL; |
| if (unlikely(!down_read_trylock(&mm->mmap_sem))) |
| goto breakouterloop_mmap_sem; |
| if (likely(!khugepaged_test_exit(mm))) |
| 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, vma->vm_flags)) { |
| 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); |
| if (shmem_file(vma->vm_file)) { |
| struct file *file; |
| pgoff_t pgoff = linear_page_index(vma, |
| khugepaged_scan.address); |
| if (!shmem_huge_enabled(vma)) |
| goto skip; |
| file = get_file(vma->vm_file); |
| up_read(&mm->mmap_sem); |
| ret = 1; |
| khugepaged_scan_shmem(mm, file->f_mapping, |
| pgoff, hpage); |
| fput(file); |
| } else { |
| 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() || try_to_freeze())) |
| 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 bool khugepaged_should_wakeup(void) |
| { |
| return kthread_should_stop() || |
| time_after_eq(jiffies, khugepaged_sleep_expire); |
| } |
| |
| static void khugepaged_wait_work(void) |
| { |
| if (khugepaged_has_work()) { |
| const unsigned long scan_sleep_jiffies = |
| msecs_to_jiffies(khugepaged_scan_sleep_millisecs); |
| |
| if (!scan_sleep_jiffies) |
| return; |
| |
| khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; |
| wait_event_freezable_timeout(khugepaged_wait, |
| khugepaged_should_wakeup(), |
| scan_sleep_jiffies); |
| 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 set_recommended_min_free_kbytes(void) |
| { |
| struct zone *zone; |
| int nr_zones = 0; |
| unsigned long recommended_min; |
| |
| for_each_populated_zone(zone) { |
| /* |
| * We don't need to worry about fragmentation of |
| * ZONE_MOVABLE since it only has movable pages. |
| */ |
| if (zone_idx(zone) > gfp_zone(GFP_USER)) |
| continue; |
| |
| nr_zones++; |
| } |
| |
| /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ |
| 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(); |
| } |
| |
| int start_stop_khugepaged(void) |
| { |
| static struct task_struct *khugepaged_thread __read_mostly; |
| static DEFINE_MUTEX(khugepaged_mutex); |
| int err = 0; |
| |
| mutex_lock(&khugepaged_mutex); |
| if (khugepaged_enabled()) { |
| if (!khugepaged_thread) |
| khugepaged_thread = kthread_run(khugepaged, NULL, |
| "khugepaged"); |
| if (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: |
| mutex_unlock(&khugepaged_mutex); |
| return err; |
| } |