/* * Copyright (C) 2009 Red Hat, Inc. * * This work is licensed under the terms of the GNU GPL, version 2. See * the COPYING file in the top-level directory. */ #include #include #include #include #include #include #include #include #include #include #include #include #include "internal.h" /* * By default transparent hugepage support is enabled for all mappings * and khugepaged scans all mappings. Defrag is only invoked by * khugepaged hugepage allocations and by page faults inside * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived * allocations. */ unsigned long transparent_hugepage_flags __read_mostly = (1< 0) { int err = start_khugepaged(); if (err) ret = err; } return ret; } static struct kobj_attribute enabled_attr = __ATTR(enabled, 0644, enabled_show, enabled_store); static ssize_t single_flag_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf, enum transparent_hugepage_flag flag) { if (test_bit(flag, &transparent_hugepage_flags)) return sprintf(buf, "[yes] no\n"); else return sprintf(buf, "yes [no]\n"); } static ssize_t single_flag_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count, enum transparent_hugepage_flag flag) { if (!memcmp("yes", buf, min(sizeof("yes")-1, count))) { set_bit(flag, &transparent_hugepage_flags); } else if (!memcmp("no", buf, min(sizeof("no")-1, count))) { clear_bit(flag, &transparent_hugepage_flags); } else return -EINVAL; return count; } /* * Currently defrag only disables __GFP_NOWAIT for allocation. A blind * __GFP_REPEAT is too aggressive, it's never worth swapping tons of * memory just to allocate one more hugepage. */ static ssize_t defrag_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return double_flag_show(kobj, attr, buf, TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); } static ssize_t defrag_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { return double_flag_store(kobj, attr, buf, count, TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); } static struct kobj_attribute defrag_attr = __ATTR(defrag, 0644, defrag_show, defrag_store); #ifdef CONFIG_DEBUG_VM static ssize_t debug_cow_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return single_flag_show(kobj, attr, buf, TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); } static ssize_t debug_cow_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { return single_flag_store(kobj, attr, buf, count, TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); } static struct kobj_attribute debug_cow_attr = __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); #endif /* CONFIG_DEBUG_VM */ static struct attribute *hugepage_attr[] = { &enabled_attr.attr, &defrag_attr.attr, #ifdef CONFIG_DEBUG_VM &debug_cow_attr.attr, #endif NULL, }; static struct attribute_group hugepage_attr_group = { .attrs = hugepage_attr, }; static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); } static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { unsigned long msecs; int err; err = strict_strtoul(buf, 10, &msecs); if (err || msecs > UINT_MAX) return -EINVAL; khugepaged_scan_sleep_millisecs = msecs; wake_up_interruptible(&khugepaged_wait); return count; } static struct kobj_attribute scan_sleep_millisecs_attr = __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, scan_sleep_millisecs_store); static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); } static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { unsigned long msecs; int err; err = strict_strtoul(buf, 10, &msecs); if (err || msecs > UINT_MAX) return -EINVAL; khugepaged_alloc_sleep_millisecs = msecs; wake_up_interruptible(&khugepaged_wait); return count; } static struct kobj_attribute alloc_sleep_millisecs_attr = __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, alloc_sleep_millisecs_store); static ssize_t pages_to_scan_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sprintf(buf, "%u\n", khugepaged_pages_to_scan); } static ssize_t pages_to_scan_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { int err; unsigned long pages; err = strict_strtoul(buf, 10, &pages); if (err || !pages || pages > UINT_MAX) return -EINVAL; khugepaged_pages_to_scan = pages; return count; } static struct kobj_attribute pages_to_scan_attr = __ATTR(pages_to_scan, 0644, pages_to_scan_show, pages_to_scan_store); static ssize_t pages_collapsed_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sprintf(buf, "%u\n", khugepaged_pages_collapsed); } static struct kobj_attribute pages_collapsed_attr = __ATTR_RO(pages_collapsed); static ssize_t full_scans_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sprintf(buf, "%u\n", khugepaged_full_scans); } static struct kobj_attribute full_scans_attr = __ATTR_RO(full_scans); static ssize_t khugepaged_defrag_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return single_flag_show(kobj, attr, buf, TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); } static ssize_t khugepaged_defrag_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { return single_flag_store(kobj, attr, buf, count, TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); } static struct kobj_attribute khugepaged_defrag_attr = __ATTR(defrag, 0644, khugepaged_defrag_show, khugepaged_defrag_store); /* * max_ptes_none controls if khugepaged should collapse hugepages over * any unmapped ptes in turn potentially increasing the memory * footprint of the vmas. When max_ptes_none is 0 khugepaged will not * reduce the available free memory in the system as it * runs. Increasing max_ptes_none will instead potentially reduce the * free memory in the system during the khugepaged scan. */ static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { return sprintf(buf, "%u\n", khugepaged_max_ptes_none); } static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { int err; unsigned long max_ptes_none; err = strict_strtoul(buf, 10, &max_ptes_none); if (err || max_ptes_none > HPAGE_PMD_NR-1) return -EINVAL; khugepaged_max_ptes_none = max_ptes_none; return count; } static struct kobj_attribute khugepaged_max_ptes_none_attr = __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, khugepaged_max_ptes_none_store); static struct attribute *khugepaged_attr[] = { &khugepaged_defrag_attr.attr, &khugepaged_max_ptes_none_attr.attr, &pages_to_scan_attr.attr, &pages_collapsed_attr.attr, &full_scans_attr.attr, &scan_sleep_millisecs_attr.attr, &alloc_sleep_millisecs_attr.attr, NULL, }; static struct attribute_group khugepaged_attr_group = { .attrs = khugepaged_attr, .name = "khugepaged", }; #endif /* CONFIG_SYSFS */ static int __init hugepage_init(void) { int err; #ifdef CONFIG_SYSFS static struct kobject *hugepage_kobj; err = -ENOMEM; hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); if (unlikely(!hugepage_kobj)) { printk(KERN_ERR "hugepage: failed kobject create\n"); goto out; } err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group); if (err) { printk(KERN_ERR "hugepage: failed register hugeage group\n"); goto out; } err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group); if (err) { printk(KERN_ERR "hugepage: failed register hugeage group\n"); goto out; } #endif err = khugepaged_slab_init(); if (err) goto out; err = mm_slots_hash_init(); if (err) { khugepaged_slab_free(); goto out; } start_khugepaged(); out: return err; } module_init(hugepage_init) static int __init setup_transparent_hugepage(char *str) { int ret = 0; if (!str) goto out; if (!strcmp(str, "always")) { set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); ret = 1; } else if (!strcmp(str, "madvise")) { clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); ret = 1; } else if (!strcmp(str, "never")) { clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); ret = 1; } out: if (!ret) printk(KERN_WARNING "transparent_hugepage= cannot parse, ignored\n"); return ret; } __setup("transparent_hugepage=", setup_transparent_hugepage); static void prepare_pmd_huge_pte(pgtable_t pgtable, struct mm_struct *mm) { assert_spin_locked(&mm->page_table_lock); /* FIFO */ if (!mm->pmd_huge_pte) INIT_LIST_HEAD(&pgtable->lru); else list_add(&pgtable->lru, &mm->pmd_huge_pte->lru); mm->pmd_huge_pte = pgtable; } static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) { if (likely(vma->vm_flags & VM_WRITE)) pmd = pmd_mkwrite(pmd); return pmd; } static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, struct page *page) { int ret = 0; pgtable_t pgtable; VM_BUG_ON(!PageCompound(page)); pgtable = pte_alloc_one(mm, haddr); if (unlikely(!pgtable)) { mem_cgroup_uncharge_page(page); put_page(page); return VM_FAULT_OOM; } clear_huge_page(page, haddr, HPAGE_PMD_NR); __SetPageUptodate(page); spin_lock(&mm->page_table_lock); if (unlikely(!pmd_none(*pmd))) { spin_unlock(&mm->page_table_lock); mem_cgroup_uncharge_page(page); put_page(page); pte_free(mm, pgtable); } else { pmd_t entry; entry = mk_pmd(page, vma->vm_page_prot); entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); entry = pmd_mkhuge(entry); /* * The spinlocking to take the lru_lock inside * page_add_new_anon_rmap() acts as a full memory * barrier to be sure clear_huge_page writes become * visible after the set_pmd_at() write. */ page_add_new_anon_rmap(page, vma, haddr); set_pmd_at(mm, haddr, pmd, entry); prepare_pmd_huge_pte(pgtable, mm); add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); spin_unlock(&mm->page_table_lock); } return ret; } static inline struct page *alloc_hugepage(int defrag) { return alloc_pages(GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT), HPAGE_PMD_ORDER); } int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, unsigned int flags) { struct page *page; unsigned long haddr = address & HPAGE_PMD_MASK; pte_t *pte; if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) { if (unlikely(anon_vma_prepare(vma))) return VM_FAULT_OOM; if (unlikely(khugepaged_enter(vma))) return VM_FAULT_OOM; page = alloc_hugepage(transparent_hugepage_defrag(vma)); if (unlikely(!page)) goto out; if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) { put_page(page); goto out; } return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page); } out: /* * Use __pte_alloc instead of pte_alloc_map, because we can't * run pte_offset_map on the pmd, if an huge pmd could * materialize from under us from a different thread. */ if (unlikely(__pte_alloc(mm, vma, pmd, address))) return VM_FAULT_OOM; /* if an huge pmd materialized from under us just retry later */ if (unlikely(pmd_trans_huge(*pmd))) return 0; /* * A regular pmd is established and it can't morph into a huge pmd * from under us anymore at this point because we hold the mmap_sem * read mode and khugepaged takes it in write mode. So now it's * safe to run pte_offset_map(). */ pte = pte_offset_map(pmd, address); return handle_pte_fault(mm, vma, address, pte, pmd, flags); } int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, struct vm_area_struct *vma) { struct page *src_page; pmd_t pmd; pgtable_t pgtable; int ret; ret = -ENOMEM; pgtable = pte_alloc_one(dst_mm, addr); if (unlikely(!pgtable)) goto out; spin_lock(&dst_mm->page_table_lock); spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING); ret = -EAGAIN; pmd = *src_pmd; if (unlikely(!pmd_trans_huge(pmd))) { pte_free(dst_mm, pgtable); goto out_unlock; } if (unlikely(pmd_trans_splitting(pmd))) { /* split huge page running from under us */ spin_unlock(&src_mm->page_table_lock); spin_unlock(&dst_mm->page_table_lock); pte_free(dst_mm, pgtable); wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ goto out; } src_page = pmd_page(pmd); VM_BUG_ON(!PageHead(src_page)); get_page(src_page); page_dup_rmap(src_page); add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); pmdp_set_wrprotect(src_mm, addr, src_pmd); pmd = pmd_mkold(pmd_wrprotect(pmd)); set_pmd_at(dst_mm, addr, dst_pmd, pmd); prepare_pmd_huge_pte(pgtable, dst_mm); ret = 0; out_unlock: spin_unlock(&src_mm->page_table_lock); spin_unlock(&dst_mm->page_table_lock); out: return ret; } /* no "address" argument so destroys page coloring of some arch */ pgtable_t get_pmd_huge_pte(struct mm_struct *mm) { pgtable_t pgtable; assert_spin_locked(&mm->page_table_lock); /* FIFO */ pgtable = mm->pmd_huge_pte; if (list_empty(&pgtable->lru)) mm->pmd_huge_pte = NULL; else { mm->pmd_huge_pte = list_entry(pgtable->lru.next, struct page, lru); list_del(&pgtable->lru); } return pgtable; } static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, pmd_t orig_pmd, struct page *page, unsigned long haddr) { pgtable_t pgtable; pmd_t _pmd; int ret = 0, i; struct page **pages; pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, GFP_KERNEL); if (unlikely(!pages)) { ret |= VM_FAULT_OOM; goto out; } for (i = 0; i < HPAGE_PMD_NR; i++) { pages[i] = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); if (unlikely(!pages[i] || mem_cgroup_newpage_charge(pages[i], mm, GFP_KERNEL))) { if (pages[i]) put_page(pages[i]); mem_cgroup_uncharge_start(); while (--i >= 0) { mem_cgroup_uncharge_page(pages[i]); put_page(pages[i]); } mem_cgroup_uncharge_end(); kfree(pages); ret |= VM_FAULT_OOM; goto out; } } for (i = 0; i < HPAGE_PMD_NR; i++) { copy_user_highpage(pages[i], page + i, haddr + PAGE_SHIFT*i, vma); __SetPageUptodate(pages[i]); cond_resched(); } spin_lock(&mm->page_table_lock); if (unlikely(!pmd_same(*pmd, orig_pmd))) goto out_free_pages; VM_BUG_ON(!PageHead(page)); pmdp_clear_flush_notify(vma, haddr, pmd); /* leave pmd empty until pte is filled */ pgtable = get_pmd_huge_pte(mm); pmd_populate(mm, &_pmd, pgtable); for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { pte_t *pte, entry; entry = mk_pte(pages[i], vma->vm_page_prot); entry = maybe_mkwrite(pte_mkdirty(entry), vma); page_add_new_anon_rmap(pages[i], vma, haddr); pte = pte_offset_map(&_pmd, haddr); VM_BUG_ON(!pte_none(*pte)); set_pte_at(mm, haddr, pte, entry); pte_unmap(pte); } kfree(pages); mm->nr_ptes++; smp_wmb(); /* make pte visible before pmd */ pmd_populate(mm, pmd, pgtable); page_remove_rmap(page); spin_unlock(&mm->page_table_lock); ret |= VM_FAULT_WRITE; put_page(page); out: return ret; out_free_pages: spin_unlock(&mm->page_table_lock); mem_cgroup_uncharge_start(); for (i = 0; i < HPAGE_PMD_NR; i++) { mem_cgroup_uncharge_page(pages[i]); put_page(pages[i]); } mem_cgroup_uncharge_end(); kfree(pages); goto out; } int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, pmd_t orig_pmd) { int ret = 0; struct page *page, *new_page; unsigned long haddr; VM_BUG_ON(!vma->anon_vma); spin_lock(&mm->page_table_lock); if (unlikely(!pmd_same(*pmd, orig_pmd))) goto out_unlock; page = pmd_page(orig_pmd); VM_BUG_ON(!PageCompound(page) || !PageHead(page)); haddr = address & HPAGE_PMD_MASK; if (page_mapcount(page) == 1) { pmd_t entry; entry = pmd_mkyoung(orig_pmd); entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) update_mmu_cache(vma, address, entry); ret |= VM_FAULT_WRITE; goto out_unlock; } get_page(page); spin_unlock(&mm->page_table_lock); if (transparent_hugepage_enabled(vma) && !transparent_hugepage_debug_cow()) new_page = alloc_hugepage(transparent_hugepage_defrag(vma)); else new_page = NULL; if (unlikely(!new_page)) { ret = do_huge_pmd_wp_page_fallback(mm, vma, address, pmd, orig_pmd, page, haddr); put_page(page); goto out; } if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { put_page(new_page); put_page(page); ret |= VM_FAULT_OOM; goto out; } copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); __SetPageUptodate(new_page); spin_lock(&mm->page_table_lock); put_page(page); if (unlikely(!pmd_same(*pmd, orig_pmd))) { mem_cgroup_uncharge_page(new_page); put_page(new_page); } else { pmd_t entry; VM_BUG_ON(!PageHead(page)); entry = mk_pmd(new_page, vma->vm_page_prot); entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); entry = pmd_mkhuge(entry); pmdp_clear_flush_notify(vma, haddr, pmd); page_add_new_anon_rmap(new_page, vma, haddr); set_pmd_at(mm, haddr, pmd, entry); update_mmu_cache(vma, address, entry); page_remove_rmap(page); put_page(page); ret |= VM_FAULT_WRITE; } out_unlock: spin_unlock(&mm->page_table_lock); out: return ret; } struct page *follow_trans_huge_pmd(struct mm_struct *mm, unsigned long addr, pmd_t *pmd, unsigned int flags) { struct page *page = NULL; assert_spin_locked(&mm->page_table_lock); if (flags & FOLL_WRITE && !pmd_write(*pmd)) goto out; page = pmd_page(*pmd); VM_BUG_ON(!PageHead(page)); if (flags & FOLL_TOUCH) { pmd_t _pmd; /* * We should set the dirty bit only for FOLL_WRITE but * for now the dirty bit in the pmd is meaningless. * And if the dirty bit will become meaningful and * we'll only set it with FOLL_WRITE, an atomic * set_bit will be required on the pmd to set the * young bit, instead of the current set_pmd_at. */ _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd); } page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; VM_BUG_ON(!PageCompound(page)); if (flags & FOLL_GET) get_page(page); out: return page; } int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd) { int ret = 0; spin_lock(&tlb->mm->page_table_lock); if (likely(pmd_trans_huge(*pmd))) { if (unlikely(pmd_trans_splitting(*pmd))) { spin_unlock(&tlb->mm->page_table_lock); wait_split_huge_page(vma->anon_vma, pmd); } else { struct page *page; pgtable_t pgtable; pgtable = get_pmd_huge_pte(tlb->mm); page = pmd_page(*pmd); pmd_clear(pmd); page_remove_rmap(page); VM_BUG_ON(page_mapcount(page) < 0); add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); VM_BUG_ON(!PageHead(page)); spin_unlock(&tlb->mm->page_table_lock); tlb_remove_page(tlb, page); pte_free(tlb->mm, pgtable); ret = 1; } } else spin_unlock(&tlb->mm->page_table_lock); return ret; } pmd_t *page_check_address_pmd(struct page *page, struct mm_struct *mm, unsigned long address, enum page_check_address_pmd_flag flag) { pgd_t *pgd; pud_t *pud; pmd_t *pmd, *ret = NULL; if (address & ~HPAGE_PMD_MASK) goto out; pgd = pgd_offset(mm, address); if (!pgd_present(*pgd)) goto out; pud = pud_offset(pgd, address); if (!pud_present(*pud)) goto out; pmd = pmd_offset(pud, address); if (pmd_none(*pmd)) goto out; if (pmd_page(*pmd) != page) goto out; VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && pmd_trans_splitting(*pmd)); if (pmd_trans_huge(*pmd)) { VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && !pmd_trans_splitting(*pmd)); ret = pmd; } out: return ret; } static int __split_huge_page_splitting(struct page *page, struct vm_area_struct *vma, unsigned long address) { struct mm_struct *mm = vma->vm_mm; pmd_t *pmd; int ret = 0; spin_lock(&mm->page_table_lock); pmd = page_check_address_pmd(page, mm, address, PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG); if (pmd) { /* * We can't temporarily set the pmd to null in order * to split it, the pmd must remain marked huge at all * times or the VM won't take the pmd_trans_huge paths * and it won't wait on the anon_vma->root->lock to * serialize against split_huge_page*. */ pmdp_splitting_flush_notify(vma, address, pmd); ret = 1; } spin_unlock(&mm->page_table_lock); return ret; } static void __split_huge_page_refcount(struct page *page) { int i; unsigned long head_index = page->index; struct zone *zone = page_zone(page); /* prevent PageLRU to go away from under us, and freeze lru stats */ spin_lock_irq(&zone->lru_lock); compound_lock(page); for (i = 1; i < HPAGE_PMD_NR; i++) { struct page *page_tail = page + i; /* tail_page->_count cannot change */ atomic_sub(atomic_read(&page_tail->_count), &page->_count); BUG_ON(page_count(page) <= 0); atomic_add(page_mapcount(page) + 1, &page_tail->_count); BUG_ON(atomic_read(&page_tail->_count) <= 0); /* after clearing PageTail the gup refcount can be released */ smp_mb(); page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; page_tail->flags |= (page->flags & ((1L << PG_referenced) | (1L << PG_swapbacked) | (1L << PG_mlocked) | (1L << PG_uptodate))); page_tail->flags |= (1L << PG_dirty); /* * 1) clear PageTail before overwriting first_page * 2) clear PageTail before clearing PageHead for VM_BUG_ON */ smp_wmb(); /* * __split_huge_page_splitting() already set the * splitting bit in all pmd that could map this * hugepage, that will ensure no CPU can alter the * mapcount on the head page. The mapcount is only * accounted in the head page and it has to be * transferred to all tail pages in the below code. So * for this code to be safe, the split the mapcount * can't change. But that doesn't mean userland can't * keep changing and reading the page contents while * we transfer the mapcount, so the pmd splitting * status is achieved setting a reserved bit in the * pmd, not by clearing the present bit. */ BUG_ON(page_mapcount(page_tail)); page_tail->_mapcount = page->_mapcount; BUG_ON(page_tail->mapping); page_tail->mapping = page->mapping; page_tail->index = ++head_index; BUG_ON(!PageAnon(page_tail)); BUG_ON(!PageUptodate(page_tail)); BUG_ON(!PageDirty(page_tail)); BUG_ON(!PageSwapBacked(page_tail)); lru_add_page_tail(zone, page, page_tail); } __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR); ClearPageCompound(page); compound_unlock(page); spin_unlock_irq(&zone->lru_lock); for (i = 1; i < HPAGE_PMD_NR; i++) { struct page *page_tail = page + i; BUG_ON(page_count(page_tail) <= 0); /* * Tail pages may be freed if there wasn't any mapping * like if add_to_swap() is running on a lru page that * had its mapping zapped. And freeing these pages * requires taking the lru_lock so we do the put_page * of the tail pages after the split is complete. */ put_page(page_tail); } /* * Only the head page (now become a regular page) is required * to be pinned by the caller. */ BUG_ON(page_count(page) <= 0); } static int __split_huge_page_map(struct page *page, struct vm_area_struct *vma, unsigned long address) { struct mm_struct *mm = vma->vm_mm; pmd_t *pmd, _pmd; int ret = 0, i; pgtable_t pgtable; unsigned long haddr; spin_lock(&mm->page_table_lock); pmd = page_check_address_pmd(page, mm, address, PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG); if (pmd) { pgtable = get_pmd_huge_pte(mm); pmd_populate(mm, &_pmd, pgtable); for (i = 0, haddr = address; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { pte_t *pte, entry; BUG_ON(PageCompound(page+i)); entry = mk_pte(page + i, vma->vm_page_prot); entry = maybe_mkwrite(pte_mkdirty(entry), vma); if (!pmd_write(*pmd)) entry = pte_wrprotect(entry); else BUG_ON(page_mapcount(page) != 1); if (!pmd_young(*pmd)) entry = pte_mkold(entry); pte = pte_offset_map(&_pmd, haddr); BUG_ON(!pte_none(*pte)); set_pte_at(mm, haddr, pte, entry); pte_unmap(pte); } mm->nr_ptes++; smp_wmb(); /* make pte visible before pmd */ /* * Up to this point the pmd is present and huge and * userland has the whole access to the hugepage * during the split (which happens in place). If we * overwrite the pmd with the not-huge version * pointing to the pte here (which of course we could * if all CPUs were bug free), userland could trigger * a small page size TLB miss on the small sized TLB * while the hugepage TLB entry is still established * in the huge TLB. Some CPU doesn't like that. See * http://support.amd.com/us/Processor_TechDocs/41322.pdf, * Erratum 383 on page 93. Intel should be safe but is * also warns that it's only safe if the permission * and cache attributes of the two entries loaded in * the two TLB is identical (which should be the case * here). But it is generally safer to never allow * small and huge TLB entries for the same virtual * address to be loaded simultaneously. So instead of * doing "pmd_populate(); flush_tlb_range();" we first * mark the current pmd notpresent (atomically because * here the pmd_trans_huge and pmd_trans_splitting * must remain set at all times on the pmd until the * split is complete for this pmd), then we flush the * SMP TLB and finally we write the non-huge version * of the pmd entry with pmd_populate. */ set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd)); flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); pmd_populate(mm, pmd, pgtable); ret = 1; } spin_unlock(&mm->page_table_lock); return ret; } /* must be called with anon_vma->root->lock hold */ static void __split_huge_page(struct page *page, struct anon_vma *anon_vma) { int mapcount, mapcount2; struct anon_vma_chain *avc; BUG_ON(!PageHead(page)); BUG_ON(PageTail(page)); mapcount = 0; list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { struct vm_area_struct *vma = avc->vma; unsigned long addr = vma_address(page, vma); BUG_ON(is_vma_temporary_stack(vma)); if (addr == -EFAULT) continue; mapcount += __split_huge_page_splitting(page, vma, addr); } /* * It is critical that new vmas are added to the tail of the * anon_vma list. This guarantes that if copy_huge_pmd() runs * and establishes a child pmd before * __split_huge_page_splitting() freezes the parent pmd (so if * we fail to prevent copy_huge_pmd() from running until the * whole __split_huge_page() is complete), we will still see * the newly established pmd of the child later during the * walk, to be able to set it as pmd_trans_splitting too. */ if (mapcount != page_mapcount(page)) printk(KERN_ERR "mapcount %d page_mapcount %d\n", mapcount, page_mapcount(page)); BUG_ON(mapcount != page_mapcount(page)); __split_huge_page_refcount(page); mapcount2 = 0; list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { struct vm_area_struct *vma = avc->vma; unsigned long addr = vma_address(page, vma); BUG_ON(is_vma_temporary_stack(vma)); if (addr == -EFAULT) continue; mapcount2 += __split_huge_page_map(page, vma, addr); } if (mapcount != mapcount2) printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n", mapcount, mapcount2, page_mapcount(page)); BUG_ON(mapcount != mapcount2); } int split_huge_page(struct page *page) { struct anon_vma *anon_vma; int ret = 1; BUG_ON(!PageAnon(page)); anon_vma = page_lock_anon_vma(page); if (!anon_vma) goto out; ret = 0; if (!PageCompound(page)) goto out_unlock; BUG_ON(!PageSwapBacked(page)); __split_huge_page(page, anon_vma); BUG_ON(PageCompound(page)); out_unlock: page_unlock_anon_vma(anon_vma); out: return ret; } int hugepage_madvise(unsigned long *vm_flags) { /* * Be somewhat over-protective like KSM for now! */ if (*vm_flags & (VM_HUGEPAGE | VM_SHARED | VM_MAYSHARE | VM_PFNMAP | VM_IO | VM_DONTEXPAND | VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | VM_MIXEDMAP | VM_SAO)) return -EINVAL; *vm_flags |= VM_HUGEPAGE; return 0; } static int __init khugepaged_slab_init(void) { mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", sizeof(struct mm_slot), __alignof__(struct mm_slot), 0, NULL); if (!mm_slot_cache) return -ENOMEM; return 0; } static void __init khugepaged_slab_free(void) { kmem_cache_destroy(mm_slot_cache); mm_slot_cache = NULL; } 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 int __init mm_slots_hash_init(void) { mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head), GFP_KERNEL); if (!mm_slots_hash) return -ENOMEM; return 0; } #if 0 static void __init mm_slots_hash_free(void) { kfree(mm_slots_hash); mm_slots_hash = NULL; } #endif static struct mm_slot *get_mm_slot(struct mm_struct *mm) { struct mm_slot *mm_slot; struct hlist_head *bucket; struct hlist_node *node; bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) % MM_SLOTS_HASH_HEADS]; hlist_for_each_entry(mm_slot, node, bucket, hash) { 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) { struct hlist_head *bucket; bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct)) % MM_SLOTS_HASH_HEADS]; mm_slot->mm = mm; hlist_add_head(&mm_slot->hash, bucket); } static inline int khugepaged_test_exit(struct mm_struct *mm) { return atomic_read(&mm->mm_users) == 0; } int __khugepaged_enter(struct mm_struct *mm) { struct mm_slot *mm_slot; int wakeup; mm_slot = alloc_mm_slot(); if (!mm_slot) return -ENOMEM; /* __khugepaged_exit() must not run from under us */ VM_BUG_ON(khugepaged_test_exit(mm)); if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { free_mm_slot(mm_slot); return 0; } spin_lock(&khugepaged_mm_lock); insert_to_mm_slots_hash(mm, mm_slot); /* * Insert just behind the scanning cursor, to let the area settle * down a little. */ wakeup = list_empty(&khugepaged_scan.mm_head); list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); spin_unlock(&khugepaged_mm_lock); atomic_inc(&mm->mm_count); if (wakeup) wake_up_interruptible(&khugepaged_wait); return 0; } int khugepaged_enter_vma_merge(struct vm_area_struct *vma) { unsigned long hstart, hend; if (!vma->anon_vma) /* * Not yet faulted in so we will register later in the * page fault if needed. */ return 0; if (vma->vm_file || vma->vm_ops) /* khugepaged not yet working on file or special mappings */ return 0; VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; hend = vma->vm_end & HPAGE_PMD_MASK; if (hstart < hend) return khugepaged_enter(vma); 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) { hlist_del(&mm_slot->hash); list_del(&mm_slot->mm_node); free = 1; } if (free) { spin_unlock(&khugepaged_mm_lock); clear_bit(MMF_VM_HUGEPAGE, &mm->flags); free_mm_slot(mm_slot); mmdrop(mm); } else if (mm_slot) { spin_unlock(&khugepaged_mm_lock); /* * 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); } else spin_unlock(&khugepaged_mm_lock); } static void release_pte_page(struct page *page) { /* 0 stands for page_is_file_cache(page) == false */ dec_zone_page_state(page, NR_ISOLATED_ANON + 0); unlock_page(page); putback_lru_page(page); } static void release_pte_pages(pte_t *pte, pte_t *_pte) { while (--_pte >= pte) { pte_t pteval = *_pte; if (!pte_none(pteval)) release_pte_page(pte_page(pteval)); } } static void release_all_pte_pages(pte_t *pte) { release_pte_pages(pte, pte + HPAGE_PMD_NR); } static int __collapse_huge_page_isolate(struct vm_area_struct *vma, unsigned long address, pte_t *pte) { struct page *page; pte_t *_pte; int referenced = 0, isolated = 0, none = 0; for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++, address += PAGE_SIZE) { pte_t pteval = *_pte; if (pte_none(pteval)) { if (++none <= khugepaged_max_ptes_none) continue; else { release_pte_pages(pte, _pte); goto out; } } if (!pte_present(pteval) || !pte_write(pteval)) { release_pte_pages(pte, _pte); goto out; } page = vm_normal_page(vma, address, pteval); if (unlikely(!page)) { release_pte_pages(pte, _pte); goto out; } VM_BUG_ON(PageCompound(page)); BUG_ON(!PageAnon(page)); VM_BUG_ON(!PageSwapBacked(page)); /* cannot use mapcount: can't collapse if there's a gup pin */ if (page_count(page) != 1) { release_pte_pages(pte, _pte); goto out; } /* * We can do it before isolate_lru_page because the * page can't be freed from under us. NOTE: PG_lock * is needed to serialize against split_huge_page * when invoked from the VM. */ if (!trylock_page(page)) { release_pte_pages(pte, _pte); goto out; } /* * Isolate the page to avoid collapsing an hugepage * currently in use by the VM. */ if (isolate_lru_page(page)) { unlock_page(page); release_pte_pages(pte, _pte); goto out; } /* 0 stands for page_is_file_cache(page) == false */ inc_zone_page_state(page, NR_ISOLATED_ANON + 0); VM_BUG_ON(!PageLocked(page)); VM_BUG_ON(PageLRU(page)); /* If there is no mapped pte young don't collapse the page */ if (pte_young(pteval)) referenced = 1; } if (unlikely(!referenced)) release_all_pte_pages(pte); else isolated = 1; out: return isolated; } static void __collapse_huge_page_copy(pte_t *pte, struct page *page, struct vm_area_struct *vma, unsigned long address, spinlock_t *ptl) { pte_t *_pte; for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { pte_t pteval = *_pte; struct page *src_page; if (pte_none(pteval)) { clear_user_highpage(page, address); add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); } else { src_page = pte_page(pteval); copy_user_highpage(page, src_page, address, vma); VM_BUG_ON(page_mapcount(src_page) != 1); VM_BUG_ON(page_count(src_page) != 2); release_pte_page(src_page); /* * ptl mostly unnecessary, but preempt has to * be disabled to update the per-cpu stats * inside page_remove_rmap(). */ spin_lock(ptl); /* * paravirt calls inside pte_clear here are * superfluous. */ pte_clear(vma->vm_mm, address, _pte); page_remove_rmap(src_page); spin_unlock(ptl); free_page_and_swap_cache(src_page); } address += PAGE_SIZE; page++; } } static void collapse_huge_page(struct mm_struct *mm, unsigned long address, struct page **hpage) { struct vm_area_struct *vma; pgd_t *pgd; pud_t *pud; pmd_t *pmd, _pmd; pte_t *pte; pgtable_t pgtable; struct page *new_page; spinlock_t *ptl; int isolated; unsigned long hstart, hend; VM_BUG_ON(address & ~HPAGE_PMD_MASK); VM_BUG_ON(!*hpage); /* * Prevent all access to pagetables with the exception of * gup_fast later hanlded by the ptep_clear_flush and the VM * handled by the anon_vma lock + PG_lock. */ down_write(&mm->mmap_sem); if (unlikely(khugepaged_test_exit(mm))) goto out; vma = find_vma(mm, address); hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; hend = vma->vm_end & HPAGE_PMD_MASK; if (address < hstart || address + HPAGE_PMD_SIZE > hend) goto out; if (!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) goto out; /* VM_PFNMAP vmas may have vm_ops null but vm_file set */ if (!vma->anon_vma || vma->vm_ops || vma->vm_file) goto out; VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); pgd = pgd_offset(mm, address); if (!pgd_present(*pgd)) goto out; pud = pud_offset(pgd, address); if (!pud_present(*pud)) goto out; pmd = pmd_offset(pud, address); /* pmd can't go away or become huge under us */ if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) goto out; new_page = *hpage; if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) goto out; anon_vma_lock(vma->anon_vma); pte = pte_offset_map(pmd, address); ptl = pte_lockptr(mm, pmd); spin_lock(&mm->page_table_lock); /* probably unnecessary */ /* * After this gup_fast can't run anymore. This also removes * any huge TLB entry from the CPU so we won't allow * huge and small TLB entries for the same virtual address * to avoid the risk of CPU bugs in that area. */ _pmd = pmdp_clear_flush_notify(vma, address, pmd); spin_unlock(&mm->page_table_lock); spin_lock(ptl); isolated = __collapse_huge_page_isolate(vma, address, pte); spin_unlock(ptl); pte_unmap(pte); if (unlikely(!isolated)) { spin_lock(&mm->page_table_lock); BUG_ON(!pmd_none(*pmd)); set_pmd_at(mm, address, pmd, _pmd); spin_unlock(&mm->page_table_lock); anon_vma_unlock(vma->anon_vma); mem_cgroup_uncharge_page(new_page); goto out; } /* * All pages are isolated and locked so anon_vma rmap * can't run anymore. */ anon_vma_unlock(vma->anon_vma); __collapse_huge_page_copy(pte, new_page, vma, address, ptl); __SetPageUptodate(new_page); pgtable = pmd_pgtable(_pmd); VM_BUG_ON(page_count(pgtable) != 1); VM_BUG_ON(page_mapcount(pgtable) != 0); _pmd = mk_pmd(new_page, vma->vm_page_prot); _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); _pmd = pmd_mkhuge(_pmd); /* * spin_lock() below is not the equivalent of smp_wmb(), so * this is needed to avoid the copy_huge_page writes to become * visible after the set_pmd_at() write. */ smp_wmb(); spin_lock(&mm->page_table_lock); BUG_ON(!pmd_none(*pmd)); page_add_new_anon_rmap(new_page, vma, address); set_pmd_at(mm, address, pmd, _pmd); update_mmu_cache(vma, address, entry); prepare_pmd_huge_pte(pgtable, mm); mm->nr_ptes--; spin_unlock(&mm->page_table_lock); *hpage = NULL; khugepaged_pages_collapsed++; out: up_write(&mm->mmap_sem); } static int khugepaged_scan_pmd(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, struct page **hpage) { pgd_t *pgd; pud_t *pud; pmd_t *pmd; pte_t *pte, *_pte; int ret = 0, referenced = 0, none = 0; struct page *page; unsigned long _address; spinlock_t *ptl; VM_BUG_ON(address & ~HPAGE_PMD_MASK); pgd = pgd_offset(mm, address); if (!pgd_present(*pgd)) goto out; pud = pud_offset(pgd, address); if (!pud_present(*pud)) goto out; pmd = pmd_offset(pud, address); if (!pmd_present(*pmd) || pmd_trans_huge(*pmd)) goto out; pte = pte_offset_map_lock(mm, pmd, address, &ptl); for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++, _address += PAGE_SIZE) { pte_t pteval = *_pte; if (pte_none(pteval)) { if (++none <= khugepaged_max_ptes_none) continue; else goto out_unmap; } if (!pte_present(pteval) || !pte_write(pteval)) goto out_unmap; page = vm_normal_page(vma, _address, pteval); if (unlikely(!page)) goto out_unmap; VM_BUG_ON(PageCompound(page)); if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) goto out_unmap; /* cannot use mapcount: can't collapse if there's a gup pin */ if (page_count(page) != 1) goto out_unmap; if (pte_young(pteval)) referenced = 1; } if (referenced) ret = 1; out_unmap: pte_unmap_unlock(pte, ptl); if (ret) { up_read(&mm->mmap_sem); collapse_huge_page(mm, address, hpage); } out: return ret; } static void collect_mm_slot(struct mm_slot *mm_slot) { struct mm_struct *mm = mm_slot->mm; VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock)); if (khugepaged_test_exit(mm)) { /* free mm_slot */ hlist_del(&mm_slot->hash); list_del(&mm_slot->mm_node); /* * Not strictly needed because the mm exited already. * * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); */ /* khugepaged_mm_lock actually not necessary for the below */ free_mm_slot(mm_slot); mmdrop(mm); } } static unsigned int khugepaged_scan_mm_slot(unsigned int pages, struct page **hpage) { struct mm_slot *mm_slot; struct mm_struct *mm; struct vm_area_struct *vma; int progress = 0; VM_BUG_ON(!pages); VM_BUG_ON(!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 (!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) { progress++; continue; } /* VM_PFNMAP vmas may have vm_ops null but vm_file set */ if (!vma->anon_vma || vma->vm_ops || vma->vm_file) { khugepaged_scan.address = vma->vm_end; progress++; continue; } VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; hend = vma->vm_end & HPAGE_PMD_MASK; if (hstart >= hend) { progress++; continue; } if (khugepaged_scan.address < hstart) khugepaged_scan.address = hstart; if (khugepaged_scan.address > hend) { khugepaged_scan.address = hend + HPAGE_PMD_SIZE; progress++; continue; } BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); while (khugepaged_scan.address < hend) { int ret; cond_resched(); if (unlikely(khugepaged_test_exit(mm))) goto breakouterloop; VM_BUG_ON(khugepaged_scan.address < hstart || khugepaged_scan.address + HPAGE_PMD_SIZE > hend); ret = khugepaged_scan_pmd(mm, vma, khugepaged_scan.address, hpage); /* move to next address */ khugepaged_scan.address += HPAGE_PMD_SIZE; progress += HPAGE_PMD_NR; if (ret) /* we released mmap_sem so break loop */ goto breakouterloop_mmap_sem; if (progress >= pages) goto breakouterloop; } } breakouterloop: up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ breakouterloop_mmap_sem: spin_lock(&khugepaged_mm_lock); 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) || !khugepaged_enabled(); } static void khugepaged_do_scan(struct page **hpage) { unsigned int progress = 0, pass_through_head = 0; unsigned int pages = khugepaged_pages_to_scan; barrier(); /* write khugepaged_pages_to_scan to local stack */ while (progress < pages) { cond_resched(); if (!*hpage) { *hpage = alloc_hugepage(khugepaged_defrag()); if (unlikely(!*hpage)) 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); } } static struct page *khugepaged_alloc_hugepage(void) { struct page *hpage; do { hpage = alloc_hugepage(khugepaged_defrag()); if (!hpage) { DEFINE_WAIT(wait); add_wait_queue(&khugepaged_wait, &wait); schedule_timeout_interruptible( msecs_to_jiffies( khugepaged_alloc_sleep_millisecs)); remove_wait_queue(&khugepaged_wait, &wait); } } while (unlikely(!hpage) && likely(khugepaged_enabled())); return hpage; } static void khugepaged_loop(void) { struct page *hpage; while (likely(khugepaged_enabled())) { hpage = khugepaged_alloc_hugepage(); if (unlikely(!hpage)) break; khugepaged_do_scan(&hpage); if (hpage) put_page(hpage); if (khugepaged_has_work()) { DEFINE_WAIT(wait); if (!khugepaged_scan_sleep_millisecs) continue; add_wait_queue(&khugepaged_wait, &wait); schedule_timeout_interruptible( msecs_to_jiffies( khugepaged_scan_sleep_millisecs)); remove_wait_queue(&khugepaged_wait, &wait); } else if (khugepaged_enabled()) wait_event_interruptible(khugepaged_wait, khugepaged_wait_event()); } } static int khugepaged(void *none) { struct mm_slot *mm_slot; set_user_nice(current, 19); /* serialize with start_khugepaged() */ mutex_lock(&khugepaged_mutex); for (;;) { mutex_unlock(&khugepaged_mutex); BUG_ON(khugepaged_thread != current); khugepaged_loop(); BUG_ON(khugepaged_thread != current); mutex_lock(&khugepaged_mutex); if (!khugepaged_enabled()) break; } 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); khugepaged_thread = NULL; mutex_unlock(&khugepaged_mutex); return 0; } void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) { struct page *page; spin_lock(&mm->page_table_lock); if (unlikely(!pmd_trans_huge(*pmd))) { spin_unlock(&mm->page_table_lock); return; } page = pmd_page(*pmd); VM_BUG_ON(!page_count(page)); get_page(page); spin_unlock(&mm->page_table_lock); split_huge_page(page); put_page(page); BUG_ON(pmd_trans_huge(*pmd)); }