diff options
Diffstat (limited to 'mm/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 901 |
1 files changed, 901 insertions, 0 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c new file mode 100644 index 000000000000..0c1e8f939f7c --- /dev/null +++ b/mm/huge_memory.c @@ -0,0 +1,901 @@ +/* + * Copyright (C) 2009 Red Hat, Inc. + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + */ + +#include <linux/mm.h> +#include <linux/sched.h> +#include <linux/highmem.h> +#include <linux/hugetlb.h> +#include <linux/mmu_notifier.h> +#include <linux/rmap.h> +#include <linux/swap.h> +#include <asm/tlb.h> +#include <asm/pgalloc.h> +#include "internal.h" + +unsigned long transparent_hugepage_flags __read_mostly = + (1<<TRANSPARENT_HUGEPAGE_FLAG); + +#ifdef CONFIG_SYSFS +static ssize_t double_flag_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf, + enum transparent_hugepage_flag enabled, + enum transparent_hugepage_flag req_madv) +{ + if (test_bit(enabled, &transparent_hugepage_flags)) { + VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); + return sprintf(buf, "[always] madvise never\n"); + } else if (test_bit(req_madv, &transparent_hugepage_flags)) + return sprintf(buf, "always [madvise] never\n"); + else + return sprintf(buf, "always madvise [never]\n"); +} +static ssize_t double_flag_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count, + enum transparent_hugepage_flag enabled, + enum transparent_hugepage_flag req_madv) +{ + if (!memcmp("always", buf, + min(sizeof("always")-1, count))) { + set_bit(enabled, &transparent_hugepage_flags); + clear_bit(req_madv, &transparent_hugepage_flags); + } else if (!memcmp("madvise", buf, + min(sizeof("madvise")-1, count))) { + clear_bit(enabled, &transparent_hugepage_flags); + set_bit(req_madv, &transparent_hugepage_flags); + } else if (!memcmp("never", buf, + min(sizeof("never")-1, count))) { + clear_bit(enabled, &transparent_hugepage_flags); + clear_bit(req_madv, &transparent_hugepage_flags); + } else + return -EINVAL; + + return count; +} + +static ssize_t enabled_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return double_flag_show(kobj, attr, buf, + TRANSPARENT_HUGEPAGE_FLAG, + TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); +} +static ssize_t enabled_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) +{ + return double_flag_store(kobj, attr, buf, count, + TRANSPARENT_HUGEPAGE_FLAG, + TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); +} +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, + .name = "transparent_hugepage", +}; +#endif /* CONFIG_SYSFS */ + +static int __init hugepage_init(void) +{ +#ifdef CONFIG_SYSFS + int err; + + err = sysfs_create_group(mm_kobj, &hugepage_attr_group); + if (err) + printk(KERN_ERR "hugepage: register sysfs failed\n"); +#endif + return 0; +} +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)) { + 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); + 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; + page = alloc_hugepage(transparent_hugepage_defrag(vma)); + if (unlikely(!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])) { + while (--i >= 0) + put_page(pages[i]); + 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); + for (i = 0; i < HPAGE_PMD_NR; i++) + put_page(pages[i]); + kfree(pages); + goto out; +} + +int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long address, pmd_t *pmd, pmd_t orig_pmd) +{ + 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; + } + + 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))) + 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); + } + + 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); + } + 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); + } + 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; +} + +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)); +} |
