--- /dev/null
+/*
+ * 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));
+}
projects / users / willy / pagecache.git / commitdiff