diff options
Diffstat (limited to 'mm/khugepaged.c')
| -rw-r--r-- | mm/khugepaged.c | 1922 |
1 files changed, 1922 insertions, 0 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c new file mode 100644 index 000000000000..7dbee698d6aa --- /dev/null +++ b/mm/khugepaged.c @@ -0,0 +1,1922 @@ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/mm.h> +#include <linux/sched.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), +}; + +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", +}; + +#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; +} + +int __khugepaged_enter(struct mm_struct *mm) +{ + struct mm_slot *mm_slot; + int wakeup; + + mm_slot = alloc_mm_slot(); + if (!mm_slot) + return -ENOMEM; + + /* __khugepaged_exit() must not run from under us */ + VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); + if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { + free_mm_slot(mm_slot); + return 0; + } + + spin_lock(&khugepaged_mm_lock); + insert_to_mm_slots_hash(mm, mm_slot); + /* + * Insert just behind the scanning cursor, to let the area settle + * down a little. + */ + wakeup = list_empty(&khugepaged_scan.mm_head); + list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); + spin_unlock(&khugepaged_mm_lock); + + atomic_inc(&mm->mm_count); + if (wakeup) + wake_up_interruptible(&khugepaged_wait); + + return 0; +} + +int khugepaged_enter_vma_merge(struct vm_area_struct *vma, + unsigned long vm_flags) +{ + unsigned long hstart, hend; + if (!vma->anon_vma) + /* + * Not yet faulted in so we will register later in the + * page fault if needed. + */ + return 0; + if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED)) + /* khugepaged not yet working on file or special mappings */ + 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) +{ + /* 0 stands for page_is_file_cache(page) == false */ + dec_zone_page_state(page, NR_ISOLATED_ANON + 0); + unlock_page(page); + putback_lru_page(page); +} + +static void release_pte_pages(pte_t *pte, pte_t *_pte) +{ + while (--_pte >= pte) { + pte_t pteval = *_pte; + if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) + release_pte_page(pte_page(pteval)); + } +} + +static int __collapse_huge_page_isolate(struct vm_area_struct *vma, + unsigned long address, + pte_t *pte) +{ + struct page *page = 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; + } + + VM_BUG_ON_PAGE(PageCompound(page), page); + VM_BUG_ON_PAGE(!PageAnon(page), page); + VM_BUG_ON_PAGE(!PageSwapBacked(page), page); + + /* + * We can do it before isolate_lru_page because the + * page can't be freed from under us. NOTE: PG_lock + * is needed to serialize against split_huge_page + * when invoked from the VM. + */ + if (!trylock_page(page)) { + 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; + } + /* 0 stands for page_is_file_cache(page) == false */ + inc_zone_page_state(page, NR_ISOLATED_ANON + 0); + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(PageLRU(page), page); + + /* 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++) { + 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); + } + + address += PAGE_SIZE; + 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 zone_reclaim_mode is disabled, then no extra effort is made to + * allocate memory locally. + */ + if (!zone_reclaim_mode) + return false; + + /* If there is a count for this node already, it must be acceptable */ + if (khugepaged_node_load[nid]) + return false; + + for (i = 0; i < MAX_NUMNODES; i++) { + if (!khugepaged_node_load[i]) + continue; + if (node_distance(nid, i) > RECLAIM_DISTANCE) + return true; + } + return false; +} + +/* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ +static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) +{ + return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0); +} + +#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 + +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 (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 !(vma->vm_flags & VM_NO_KHUGEPAGED); +} + +/* + * 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 *vma; + unsigned long hstart, hend; + + if (unlikely(khugepaged_test_exit(mm))) + return SCAN_ANY_PROCESS; + + 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)) + 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) +{ + pte_t pteval; + int swapped_in = 0, ret = 0; + struct fault_env fe = { + .vma = vma, + .address = address, + .flags = FAULT_FLAG_ALLOW_RETRY, + .pmd = pmd, + }; + + fe.pte = pte_offset_map(pmd, address); + for (; fe.address < address + HPAGE_PMD_NR*PAGE_SIZE; + fe.pte++, fe.address += PAGE_SIZE) { + pteval = *fe.pte; + if (!is_swap_pte(pteval)) + continue; + swapped_in++; + /* 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; + } + ret = do_swap_page(&fe, pteval); + + /* 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)) { + /* 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) + 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 */ + fe.pte = pte_offset_map(pmd, fe.address); + } + fe.pte--; + pte_unmap(fe.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, + struct vm_area_struct *vma, + 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; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ + gfp_t gfp; + + VM_BUG_ON(address & ~HPAGE_PMD_MASK); + + /* Only allocate from the target node */ + gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __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); + 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); + 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); + + mmun_start = address; + mmun_end = address + HPAGE_PMD_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ + /* + * After this gup_fast can't run anymore. This also removes + * any huge TLB entry from the CPU so we won't allow + * huge and small TLB entries for the same virtual address + * to avoid the risk of CPU bugs in that area. + */ + _pmd = pmdp_collapse_flush(vma, address, pmd); + spin_unlock(pmd_ptl); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + + spin_lock(pte_ptl); + isolated = __collapse_huge_page_isolate(vma, address, pte); + spin_unlock(pte_ptl); + + if (unlikely(!isolated)) { + pte_unmap(pte); + spin_lock(pmd_ptl); + BUG_ON(!pmd_none(*pmd)); + /* + * We can only use set_pmd_at when establishing + * hugepmds and never for establishing regular pmds that + * points to regular pagetables. Use pmd_populate for that + */ + pmd_populate(mm, pmd, pmd_pgtable(_pmd)); + spin_unlock(pmd_ptl); + anon_vma_unlock_write(vma->anon_vma); + 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); + 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, vma, 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; + + 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); + } +} + +#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); + atomic_long_dec(&vma->vm_mm->nr_ptes); + 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 freeze a new huge page; + * - scan over radix tree replacing old pages the new one + * + swap in pages if necessary; + * + fill in gaps; + * + keep old pages around in case if rollback is required; + * - if replacing succeed: + * + copy data over; + * + free old pages; + * + unfreeze huge page; + * - if replacing failed; + * + put all pages back and unfreeze them; + * + restore gaps in the radix-tree; + * + 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 *page, *new_page, *tmp; + struct mem_cgroup *memcg; + pgoff_t index, end = start + HPAGE_PMD_NR; + LIST_HEAD(pagelist); + struct radix_tree_iter iter; + void **slot; + 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_OTHER_NODE | __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; + } + + new_page->index = start; + new_page->mapping = mapping; + __SetPageSwapBacked(new_page); + __SetPageLocked(new_page); + BUG_ON(!page_ref_freeze(new_page, 1)); + + + /* + * At this point the new_page is 'frozen' (page_count() is zero), locked + * and not up-to-date. It's safe to insert it into radix tree, because + * nobody would be able to map it or use it in other way until we + * unfreeze it. + */ + + index = start; + spin_lock_irq(&mapping->tree_lock); + radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { + int n = min(iter.index, end) - index; + + /* + * Handle holes in the radix tree: charge it from shmem and + * insert relevant subpage of new_page into the radix-tree. + */ + if (n && !shmem_charge(mapping->host, n)) { + result = SCAN_FAIL; + break; + } + nr_none += n; + for (; index < min(iter.index, end); index++) { + radix_tree_insert(&mapping->page_tree, index, + new_page + (index % HPAGE_PMD_NR)); + } + + /* We are done. */ + if (index >= end) + break; + + page = radix_tree_deref_slot_protected(slot, + &mapping->tree_lock); + if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) { + spin_unlock_irq(&mapping->tree_lock); + /* swap in or instantiate fallocated page */ + if (shmem_getpage(mapping->host, index, &page, + SGP_NOHUGE)) { + result = SCAN_FAIL; + goto tree_unlocked; + } + spin_lock_irq(&mapping->tree_lock); + } else if (trylock_page(page)) { + get_page(page); + } else { + result = SCAN_PAGE_LOCK; + break; + } + + /* + * The page must be locked, so we can drop the tree_lock + * without racing with truncate. + */ + VM_BUG_ON_PAGE(!PageLocked(page), page); + VM_BUG_ON_PAGE(!PageUptodate(page), page); + VM_BUG_ON_PAGE(PageTransCompound(page), page); + + if (page_mapping(page) != mapping) { + result = SCAN_TRUNCATED; + goto out_unlock; + } + spin_unlock_irq(&mapping->tree_lock); + + if (isolate_lru_page(page)) { + result = SCAN_DEL_PAGE_LRU; + goto out_isolate_failed; + } + + if (page_mapped(page)) + unmap_mapping_range(mapping, index << PAGE_SHIFT, + PAGE_SIZE, 0); + + spin_lock_irq(&mapping->tree_lock); + + 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 radix tree; + * - one from isolate_lru_page; + */ + if (!page_ref_freeze(page, 3)) { + result = SCAN_PAGE_COUNT; + goto out_lru; + } + + /* + * 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. */ + radix_tree_replace_slot(slot, + new_page + (index % HPAGE_PMD_NR)); + + index++; + continue; +out_lru: + spin_unlock_irq(&mapping->tree_lock); + putback_lru_page(page); +out_isolate_failed: + unlock_page(page); + put_page(page); + goto tree_unlocked; +out_unlock: + unlock_page(page); + put_page(page); + break; + } + + /* + * Handle hole in radix tree at the end of the range. + * This code only triggers if there's nothing in radix tree + * beyond 'end'. + */ + if (result == SCAN_SUCCEED && index < end) { + int n = end - index; + + if (!shmem_charge(mapping->host, n)) { + result = SCAN_FAIL; + goto tree_locked; + } + + for (; index < end; index++) { + radix_tree_insert(&mapping->page_tree, index, + new_page + (index % HPAGE_PMD_NR)); + } + nr_none += n; + } + +tree_locked: + spin_unlock_irq(&mapping->tree_lock); +tree_unlocked: + + if (result == SCAN_SUCCEED) { + unsigned long flags; + struct zone *zone = page_zone(new_page); + + /* + * Replacing old pages with new one has succeed, now we need to + * copy the content and free old pages. + */ + list_for_each_entry_safe(page, tmp, &pagelist, lru) { + copy_highpage(new_page + (page->index % HPAGE_PMD_NR), + page); + list_del(&page->lru); + unlock_page(page); + page_ref_unfreeze(page, 1); + page->mapping = NULL; + ClearPageActive(page); + ClearPageUnevictable(page); + put_page(page); + } + + local_irq_save(flags); + __inc_zone_page_state(new_page, NR_SHMEM_THPS); + if (nr_none) { + __mod_zone_page_state(zone, NR_FILE_PAGES, nr_none); + __mod_zone_page_state(zone, NR_SHMEM, nr_none); + } + local_irq_restore(flags); + + /* + * Remove pte page tables, so we can re-faulti + * the page as huge. + */ + retract_page_tables(mapping, start); + + /* Everything is ready, let's unfreeze the new_page */ + set_page_dirty(new_page); + SetPageUptodate(new_page); + page_ref_unfreeze(new_page, HPAGE_PMD_NR); + mem_cgroup_commit_charge(new_page, memcg, false, true); + lru_cache_add_anon(new_page); + unlock_page(new_page); + + *hpage = NULL; + } else { + /* Something went wrong: rollback changes to the radix-tree */ + shmem_uncharge(mapping->host, nr_none); + spin_lock_irq(&mapping->tree_lock); + radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, + start) { + if (iter.index >= end) + break; + page = list_first_entry_or_null(&pagelist, + struct page, lru); + if (!page || iter.index < page->index) { + if (!nr_none) + break; + /* Put holes back where they were */ + radix_tree_replace_slot(slot, NULL); + nr_none--; + continue; + } + + VM_BUG_ON_PAGE(page->index != iter.index, page); + + /* Unfreeze the page. */ + list_del(&page->lru); + page_ref_unfreeze(page, 2); + radix_tree_replace_slot(slot, page); + spin_unlock_irq(&mapping->tree_lock); + putback_lru_page(page); + unlock_page(page); + spin_lock_irq(&mapping->tree_lock); + } + VM_BUG_ON(nr_none); + spin_unlock_irq(&mapping->tree_lock); + + /* Unfreeze new_page, caller would take care about freeing it */ + page_ref_unfreeze(new_page, 1); + mem_cgroup_cancel_charge(new_page, memcg, true); + unlock_page(new_page); + new_page->mapping = NULL; + } +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; + struct radix_tree_iter iter; + void **slot; + 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(); + radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { + if (iter.index >= start + HPAGE_PMD_NR) + break; + + page = radix_tree_deref_slot(slot); + if (radix_tree_deref_retry(page)) { + slot = radix_tree_iter_retry(&iter); + continue; + } + + if (radix_tree_exception(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()) { + cond_resched_rcu(); + slot = radix_tree_iter_next(&iter); + } + } + 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); + 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); + 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) + 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; +} |