v4.19.13 snapshot.
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
new file mode 100644
index 0000000..d2cd70c
--- /dev/null
+++ b/mm/huge_memory.c
@@ -0,0 +1,2939 @@
+/*
+ * 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.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/sched/coredump.h>
+#include <linux/sched/numa_balancing.h>
+#include <linux/highmem.h>
+#include <linux/hugetlb.h>
+#include <linux/mmu_notifier.h>
+#include <linux/rmap.h>
+#include <linux/swap.h>
+#include <linux/shrinker.h>
+#include <linux/mm_inline.h>
+#include <linux/swapops.h>
+#include <linux/dax.h>
+#include <linux/khugepaged.h>
+#include <linux/freezer.h>
+#include <linux/pfn_t.h>
+#include <linux/mman.h>
+#include <linux/memremap.h>
+#include <linux/pagemap.h>
+#include <linux/debugfs.h>
+#include <linux/migrate.h>
+#include <linux/hashtable.h>
+#include <linux/userfaultfd_k.h>
+#include <linux/page_idle.h>
+#include <linux/shmem_fs.h>
+#include <linux/oom.h>
+
+#include <asm/tlb.h>
+#include <asm/pgalloc.h>
+#include "internal.h"
+
+/*
+ * By default, transparent hugepage support is disabled in order to avoid
+ * risking an increased memory footprint for applications that are not
+ * guaranteed to benefit from it. When transparent hugepage support is
+ * enabled, it is for all mappings, and khugepaged scans all mappings.
+ * Defrag is invoked by khugepaged hugepage allocations and by page faults
+ * for all hugepage allocations.
+ */
+unsigned long transparent_hugepage_flags __read_mostly =
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
+ (1<<TRANSPARENT_HUGEPAGE_FLAG)|
+#endif
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
+ (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
+#endif
+ (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
+ (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
+ (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
+
+static struct shrinker deferred_split_shrinker;
+
+static atomic_t huge_zero_refcount;
+struct page *huge_zero_page __read_mostly;
+
+static struct page *get_huge_zero_page(void)
+{
+ struct page *zero_page;
+retry:
+ if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
+ return READ_ONCE(huge_zero_page);
+
+ zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
+ HPAGE_PMD_ORDER);
+ if (!zero_page) {
+ count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
+ return NULL;
+ }
+ count_vm_event(THP_ZERO_PAGE_ALLOC);
+ preempt_disable();
+ if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
+ preempt_enable();
+ __free_pages(zero_page, compound_order(zero_page));
+ goto retry;
+ }
+
+ /* We take additional reference here. It will be put back by shrinker */
+ atomic_set(&huge_zero_refcount, 2);
+ preempt_enable();
+ return READ_ONCE(huge_zero_page);
+}
+
+static void put_huge_zero_page(void)
+{
+ /*
+ * Counter should never go to zero here. Only shrinker can put
+ * last reference.
+ */
+ BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
+}
+
+struct page *mm_get_huge_zero_page(struct mm_struct *mm)
+{
+ if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
+ return READ_ONCE(huge_zero_page);
+
+ if (!get_huge_zero_page())
+ return NULL;
+
+ if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
+ put_huge_zero_page();
+
+ return READ_ONCE(huge_zero_page);
+}
+
+void mm_put_huge_zero_page(struct mm_struct *mm)
+{
+ if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
+ put_huge_zero_page();
+}
+
+static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ /* we can free zero page only if last reference remains */
+ return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
+}
+
+static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
+ struct page *zero_page = xchg(&huge_zero_page, NULL);
+ BUG_ON(zero_page == NULL);
+ __free_pages(zero_page, compound_order(zero_page));
+ return HPAGE_PMD_NR;
+ }
+
+ return 0;
+}
+
+static struct shrinker huge_zero_page_shrinker = {
+ .count_objects = shrink_huge_zero_page_count,
+ .scan_objects = shrink_huge_zero_page_scan,
+ .seeks = DEFAULT_SEEKS,
+};
+
+#ifdef CONFIG_SYSFS
+static ssize_t enabled_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
+ return sprintf(buf, "[always] madvise never\n");
+ else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
+ return sprintf(buf, "always [madvise] never\n");
+ else
+ return sprintf(buf, "always madvise [never]\n");
+}
+
+static ssize_t enabled_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ ssize_t ret = count;
+
+ if (!memcmp("always", buf,
+ min(sizeof("always")-1, count))) {
+ clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
+ set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
+ } else if (!memcmp("madvise", buf,
+ min(sizeof("madvise")-1, count))) {
+ clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
+ set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
+ } else if (!memcmp("never", buf,
+ min(sizeof("never")-1, count))) {
+ clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
+ } else
+ ret = -EINVAL;
+
+ if (ret > 0) {
+ int err = start_stop_khugepaged();
+ if (err)
+ ret = err;
+ }
+ return ret;
+}
+static struct kobj_attribute enabled_attr =
+ __ATTR(enabled, 0644, enabled_show, enabled_store);
+
+ssize_t single_hugepage_flag_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf,
+ enum transparent_hugepage_flag flag)
+{
+ return sprintf(buf, "%d\n",
+ !!test_bit(flag, &transparent_hugepage_flags));
+}
+
+ssize_t single_hugepage_flag_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count,
+ enum transparent_hugepage_flag flag)
+{
+ unsigned long value;
+ int ret;
+
+ ret = kstrtoul(buf, 10, &value);
+ if (ret < 0)
+ return ret;
+ if (value > 1)
+ return -EINVAL;
+
+ if (value)
+ set_bit(flag, &transparent_hugepage_flags);
+ else
+ clear_bit(flag, &transparent_hugepage_flags);
+
+ return count;
+}
+
+static ssize_t defrag_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
+ return sprintf(buf, "[always] defer defer+madvise madvise never\n");
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
+ return sprintf(buf, "always [defer] defer+madvise madvise never\n");
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
+ return sprintf(buf, "always defer [defer+madvise] madvise never\n");
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
+ return sprintf(buf, "always defer defer+madvise [madvise] never\n");
+ return sprintf(buf, "always defer defer+madvise madvise [never]\n");
+}
+
+static ssize_t defrag_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ if (!memcmp("always", buf,
+ min(sizeof("always")-1, count))) {
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+ set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+ } else if (!memcmp("defer+madvise", buf,
+ min(sizeof("defer+madvise")-1, count))) {
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+ set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+ } else if (!memcmp("defer", buf,
+ min(sizeof("defer")-1, count))) {
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+ set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+ } else if (!memcmp("madvise", buf,
+ min(sizeof("madvise")-1, count))) {
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+ set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+ } else if (!memcmp("never", buf,
+ min(sizeof("never")-1, count))) {
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
+ clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
+ } else
+ return -EINVAL;
+
+ return count;
+}
+static struct kobj_attribute defrag_attr =
+ __ATTR(defrag, 0644, defrag_show, defrag_store);
+
+static ssize_t use_zero_page_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return single_hugepage_flag_show(kobj, attr, buf,
+ TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
+}
+static ssize_t use_zero_page_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf, size_t count)
+{
+ return single_hugepage_flag_store(kobj, attr, buf, count,
+ TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
+}
+static struct kobj_attribute use_zero_page_attr =
+ __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
+
+static ssize_t hpage_pmd_size_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
+}
+static struct kobj_attribute hpage_pmd_size_attr =
+ __ATTR_RO(hpage_pmd_size);
+
+#ifdef CONFIG_DEBUG_VM
+static ssize_t debug_cow_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return single_hugepage_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_hugepage_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,
+ &use_zero_page_attr.attr,
+ &hpage_pmd_size_attr.attr,
+#if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
+ &shmem_enabled_attr.attr,
+#endif
+#ifdef CONFIG_DEBUG_VM
+ &debug_cow_attr.attr,
+#endif
+ NULL,
+};
+
+static const struct attribute_group hugepage_attr_group = {
+ .attrs = hugepage_attr,
+};
+
+static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
+{
+ int err;
+
+ *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
+ if (unlikely(!*hugepage_kobj)) {
+ pr_err("failed to create transparent hugepage kobject\n");
+ return -ENOMEM;
+ }
+
+ err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
+ if (err) {
+ pr_err("failed to register transparent hugepage group\n");
+ goto delete_obj;
+ }
+
+ err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
+ if (err) {
+ pr_err("failed to register transparent hugepage group\n");
+ goto remove_hp_group;
+ }
+
+ return 0;
+
+remove_hp_group:
+ sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
+delete_obj:
+ kobject_put(*hugepage_kobj);
+ return err;
+}
+
+static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
+{
+ sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
+ sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
+ kobject_put(hugepage_kobj);
+}
+#else
+static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
+{
+ return 0;
+}
+
+static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
+{
+}
+#endif /* CONFIG_SYSFS */
+
+static int __init hugepage_init(void)
+{
+ int err;
+ struct kobject *hugepage_kobj;
+
+ if (!has_transparent_hugepage()) {
+ transparent_hugepage_flags = 0;
+ return -EINVAL;
+ }
+
+ /*
+ * hugepages can't be allocated by the buddy allocator
+ */
+ MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
+ /*
+ * we use page->mapping and page->index in second tail page
+ * as list_head: assuming THP order >= 2
+ */
+ MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
+
+ err = hugepage_init_sysfs(&hugepage_kobj);
+ if (err)
+ goto err_sysfs;
+
+ err = khugepaged_init();
+ if (err)
+ goto err_slab;
+
+ err = register_shrinker(&huge_zero_page_shrinker);
+ if (err)
+ goto err_hzp_shrinker;
+ err = register_shrinker(&deferred_split_shrinker);
+ if (err)
+ goto err_split_shrinker;
+
+ /*
+ * By default disable transparent hugepages on smaller systems,
+ * where the extra memory used could hurt more than TLB overhead
+ * is likely to save. The admin can still enable it through /sys.
+ */
+ if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
+ transparent_hugepage_flags = 0;
+ return 0;
+ }
+
+ err = start_stop_khugepaged();
+ if (err)
+ goto err_khugepaged;
+
+ return 0;
+err_khugepaged:
+ unregister_shrinker(&deferred_split_shrinker);
+err_split_shrinker:
+ unregister_shrinker(&huge_zero_page_shrinker);
+err_hzp_shrinker:
+ khugepaged_destroy();
+err_slab:
+ hugepage_exit_sysfs(hugepage_kobj);
+err_sysfs:
+ return err;
+}
+subsys_initcall(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)
+ pr_warn("transparent_hugepage= cannot parse, ignored\n");
+ return ret;
+}
+__setup("transparent_hugepage=", setup_transparent_hugepage);
+
+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 inline struct list_head *page_deferred_list(struct page *page)
+{
+ /* ->lru in the tail pages is occupied by compound_head. */
+ return &page[2].deferred_list;
+}
+
+void prep_transhuge_page(struct page *page)
+{
+ /*
+ * we use page->mapping and page->indexlru in second tail page
+ * as list_head: assuming THP order >= 2
+ */
+
+ INIT_LIST_HEAD(page_deferred_list(page));
+ set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
+}
+
+unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
+ loff_t off, unsigned long flags, unsigned long size)
+{
+ unsigned long addr;
+ loff_t off_end = off + len;
+ loff_t off_align = round_up(off, size);
+ unsigned long len_pad;
+
+ if (off_end <= off_align || (off_end - off_align) < size)
+ return 0;
+
+ len_pad = len + size;
+ if (len_pad < len || (off + len_pad) < off)
+ return 0;
+
+ addr = current->mm->get_unmapped_area(filp, 0, len_pad,
+ off >> PAGE_SHIFT, flags);
+ if (IS_ERR_VALUE(addr))
+ return 0;
+
+ addr += (off - addr) & (size - 1);
+ return addr;
+}
+
+unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
+ unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+ loff_t off = (loff_t)pgoff << PAGE_SHIFT;
+
+ if (addr)
+ goto out;
+ if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
+ goto out;
+
+ addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
+ if (addr)
+ return addr;
+
+ out:
+ return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
+}
+EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
+
+static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
+ struct page *page, gfp_t gfp)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct mem_cgroup *memcg;
+ pgtable_t pgtable;
+ unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
+ vm_fault_t ret = 0;
+
+ VM_BUG_ON_PAGE(!PageCompound(page), page);
+
+ if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
+ put_page(page);
+ count_vm_event(THP_FAULT_FALLBACK);
+ return VM_FAULT_FALLBACK;
+ }
+
+ pgtable = pte_alloc_one(vma->vm_mm, haddr);
+ if (unlikely(!pgtable)) {
+ ret = VM_FAULT_OOM;
+ goto release;
+ }
+
+ clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
+ /*
+ * The memory barrier inside __SetPageUptodate makes sure that
+ * clear_huge_page writes become visible before the set_pmd_at()
+ * write.
+ */
+ __SetPageUptodate(page);
+
+ vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
+ if (unlikely(!pmd_none(*vmf->pmd))) {
+ goto unlock_release;
+ } else {
+ pmd_t entry;
+
+ ret = check_stable_address_space(vma->vm_mm);
+ if (ret)
+ goto unlock_release;
+
+ /* Deliver the page fault to userland */
+ if (userfaultfd_missing(vma)) {
+ vm_fault_t ret2;
+
+ spin_unlock(vmf->ptl);
+ mem_cgroup_cancel_charge(page, memcg, true);
+ put_page(page);
+ pte_free(vma->vm_mm, pgtable);
+ ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
+ VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
+ return ret2;
+ }
+
+ entry = mk_huge_pmd(page, vma->vm_page_prot);
+ entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ page_add_new_anon_rmap(page, vma, haddr, true);
+ mem_cgroup_commit_charge(page, memcg, false, true);
+ lru_cache_add_active_or_unevictable(page, vma);
+ pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
+ set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
+ add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
+ mm_inc_nr_ptes(vma->vm_mm);
+ spin_unlock(vmf->ptl);
+ count_vm_event(THP_FAULT_ALLOC);
+ }
+
+ return 0;
+unlock_release:
+ spin_unlock(vmf->ptl);
+release:
+ if (pgtable)
+ pte_free(vma->vm_mm, pgtable);
+ mem_cgroup_cancel_charge(page, memcg, true);
+ put_page(page);
+ return ret;
+
+}
+
+/*
+ * always: directly stall for all thp allocations
+ * defer: wake kswapd and fail if not immediately available
+ * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
+ * fail if not immediately available
+ * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
+ * available
+ * never: never stall for any thp allocation
+ */
+static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
+{
+ const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
+
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
+ return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
+ return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
+ return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
+ __GFP_KSWAPD_RECLAIM);
+ if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
+ return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
+ 0);
+ return GFP_TRANSHUGE_LIGHT;
+}
+
+/* Caller must hold page table lock. */
+static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
+ struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
+ struct page *zero_page)
+{
+ pmd_t entry;
+ if (!pmd_none(*pmd))
+ return false;
+ entry = mk_pmd(zero_page, vma->vm_page_prot);
+ entry = pmd_mkhuge(entry);
+ if (pgtable)
+ pgtable_trans_huge_deposit(mm, pmd, pgtable);
+ set_pmd_at(mm, haddr, pmd, entry);
+ mm_inc_nr_ptes(mm);
+ return true;
+}
+
+vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ gfp_t gfp;
+ struct page *page;
+ unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
+
+ if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
+ return VM_FAULT_FALLBACK;
+ if (unlikely(anon_vma_prepare(vma)))
+ return VM_FAULT_OOM;
+ if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
+ return VM_FAULT_OOM;
+ if (!(vmf->flags & FAULT_FLAG_WRITE) &&
+ !mm_forbids_zeropage(vma->vm_mm) &&
+ transparent_hugepage_use_zero_page()) {
+ pgtable_t pgtable;
+ struct page *zero_page;
+ bool set;
+ vm_fault_t ret;
+ pgtable = pte_alloc_one(vma->vm_mm, haddr);
+ if (unlikely(!pgtable))
+ return VM_FAULT_OOM;
+ zero_page = mm_get_huge_zero_page(vma->vm_mm);
+ if (unlikely(!zero_page)) {
+ pte_free(vma->vm_mm, pgtable);
+ count_vm_event(THP_FAULT_FALLBACK);
+ return VM_FAULT_FALLBACK;
+ }
+ vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
+ ret = 0;
+ set = false;
+ if (pmd_none(*vmf->pmd)) {
+ ret = check_stable_address_space(vma->vm_mm);
+ if (ret) {
+ spin_unlock(vmf->ptl);
+ } else if (userfaultfd_missing(vma)) {
+ spin_unlock(vmf->ptl);
+ ret = handle_userfault(vmf, VM_UFFD_MISSING);
+ VM_BUG_ON(ret & VM_FAULT_FALLBACK);
+ } else {
+ set_huge_zero_page(pgtable, vma->vm_mm, vma,
+ haddr, vmf->pmd, zero_page);
+ spin_unlock(vmf->ptl);
+ set = true;
+ }
+ } else
+ spin_unlock(vmf->ptl);
+ if (!set)
+ pte_free(vma->vm_mm, pgtable);
+ return ret;
+ }
+ gfp = alloc_hugepage_direct_gfpmask(vma);
+ page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
+ if (unlikely(!page)) {
+ count_vm_event(THP_FAULT_FALLBACK);
+ return VM_FAULT_FALLBACK;
+ }
+ prep_transhuge_page(page);
+ return __do_huge_pmd_anonymous_page(vmf, page, gfp);
+}
+
+static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
+ pgtable_t pgtable)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ pmd_t entry;
+ spinlock_t *ptl;
+
+ ptl = pmd_lock(mm, pmd);
+ entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
+ if (pfn_t_devmap(pfn))
+ entry = pmd_mkdevmap(entry);
+ if (write) {
+ entry = pmd_mkyoung(pmd_mkdirty(entry));
+ entry = maybe_pmd_mkwrite(entry, vma);
+ }
+
+ if (pgtable) {
+ pgtable_trans_huge_deposit(mm, pmd, pgtable);
+ mm_inc_nr_ptes(mm);
+ }
+
+ set_pmd_at(mm, addr, pmd, entry);
+ update_mmu_cache_pmd(vma, addr, pmd);
+ spin_unlock(ptl);
+}
+
+vm_fault_t vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t *pmd, pfn_t pfn, bool write)
+{
+ pgprot_t pgprot = vma->vm_page_prot;
+ pgtable_t pgtable = NULL;
+ /*
+ * If we had pmd_special, we could avoid all these restrictions,
+ * but we need to be consistent with PTEs and architectures that
+ * can't support a 'special' bit.
+ */
+ BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
+ !pfn_t_devmap(pfn));
+ BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
+ (VM_PFNMAP|VM_MIXEDMAP));
+ BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
+
+ if (addr < vma->vm_start || addr >= vma->vm_end)
+ return VM_FAULT_SIGBUS;
+
+ if (arch_needs_pgtable_deposit()) {
+ pgtable = pte_alloc_one(vma->vm_mm, addr);
+ if (!pgtable)
+ return VM_FAULT_OOM;
+ }
+
+ track_pfn_insert(vma, &pgprot, pfn);
+
+ insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
+ return VM_FAULT_NOPAGE;
+}
+EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
+{
+ if (likely(vma->vm_flags & VM_WRITE))
+ pud = pud_mkwrite(pud);
+ return pud;
+}
+
+static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
+ pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ pud_t entry;
+ spinlock_t *ptl;
+
+ ptl = pud_lock(mm, pud);
+ entry = pud_mkhuge(pfn_t_pud(pfn, prot));
+ if (pfn_t_devmap(pfn))
+ entry = pud_mkdevmap(entry);
+ if (write) {
+ entry = pud_mkyoung(pud_mkdirty(entry));
+ entry = maybe_pud_mkwrite(entry, vma);
+ }
+ set_pud_at(mm, addr, pud, entry);
+ update_mmu_cache_pud(vma, addr, pud);
+ spin_unlock(ptl);
+}
+
+vm_fault_t vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
+ pud_t *pud, pfn_t pfn, bool write)
+{
+ pgprot_t pgprot = vma->vm_page_prot;
+ /*
+ * If we had pud_special, we could avoid all these restrictions,
+ * but we need to be consistent with PTEs and architectures that
+ * can't support a 'special' bit.
+ */
+ BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
+ !pfn_t_devmap(pfn));
+ BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
+ (VM_PFNMAP|VM_MIXEDMAP));
+ BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
+
+ if (addr < vma->vm_start || addr >= vma->vm_end)
+ return VM_FAULT_SIGBUS;
+
+ track_pfn_insert(vma, &pgprot, pfn);
+
+ insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
+ return VM_FAULT_NOPAGE;
+}
+EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+
+static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t *pmd, int flags)
+{
+ pmd_t _pmd;
+
+ _pmd = pmd_mkyoung(*pmd);
+ if (flags & FOLL_WRITE)
+ _pmd = pmd_mkdirty(_pmd);
+ if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
+ pmd, _pmd, flags & FOLL_WRITE))
+ update_mmu_cache_pmd(vma, addr, pmd);
+}
+
+struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t *pmd, int flags)
+{
+ unsigned long pfn = pmd_pfn(*pmd);
+ struct mm_struct *mm = vma->vm_mm;
+ struct dev_pagemap *pgmap;
+ struct page *page;
+
+ assert_spin_locked(pmd_lockptr(mm, pmd));
+
+ /*
+ * When we COW a devmap PMD entry, we split it into PTEs, so we should
+ * not be in this function with `flags & FOLL_COW` set.
+ */
+ WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
+
+ if (flags & FOLL_WRITE && !pmd_write(*pmd))
+ return NULL;
+
+ if (pmd_present(*pmd) && pmd_devmap(*pmd))
+ /* pass */;
+ else
+ return NULL;
+
+ if (flags & FOLL_TOUCH)
+ touch_pmd(vma, addr, pmd, flags);
+
+ /*
+ * device mapped pages can only be returned if the
+ * caller will manage the page reference count.
+ */
+ if (!(flags & FOLL_GET))
+ return ERR_PTR(-EEXIST);
+
+ pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
+ pgmap = get_dev_pagemap(pfn, NULL);
+ if (!pgmap)
+ return ERR_PTR(-EFAULT);
+ page = pfn_to_page(pfn);
+ get_page(page);
+ put_dev_pagemap(pgmap);
+
+ return page;
+}
+
+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)
+{
+ spinlock_t *dst_ptl, *src_ptl;
+ struct page *src_page;
+ pmd_t pmd;
+ pgtable_t pgtable = NULL;
+ int ret = -ENOMEM;
+
+ /* Skip if can be re-fill on fault */
+ if (!vma_is_anonymous(vma))
+ return 0;
+
+ pgtable = pte_alloc_one(dst_mm, addr);
+ if (unlikely(!pgtable))
+ goto out;
+
+ dst_ptl = pmd_lock(dst_mm, dst_pmd);
+ src_ptl = pmd_lockptr(src_mm, src_pmd);
+ spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
+
+ ret = -EAGAIN;
+ pmd = *src_pmd;
+
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ if (unlikely(is_swap_pmd(pmd))) {
+ swp_entry_t entry = pmd_to_swp_entry(pmd);
+
+ VM_BUG_ON(!is_pmd_migration_entry(pmd));
+ if (is_write_migration_entry(entry)) {
+ make_migration_entry_read(&entry);
+ pmd = swp_entry_to_pmd(entry);
+ if (pmd_swp_soft_dirty(*src_pmd))
+ pmd = pmd_swp_mksoft_dirty(pmd);
+ set_pmd_at(src_mm, addr, src_pmd, pmd);
+ }
+ add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
+ mm_inc_nr_ptes(dst_mm);
+ pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
+ set_pmd_at(dst_mm, addr, dst_pmd, pmd);
+ ret = 0;
+ goto out_unlock;
+ }
+#endif
+
+ if (unlikely(!pmd_trans_huge(pmd))) {
+ pte_free(dst_mm, pgtable);
+ goto out_unlock;
+ }
+ /*
+ * When page table lock is held, the huge zero pmd should not be
+ * under splitting since we don't split the page itself, only pmd to
+ * a page table.
+ */
+ if (is_huge_zero_pmd(pmd)) {
+ struct page *zero_page;
+ /*
+ * get_huge_zero_page() will never allocate a new page here,
+ * since we already have a zero page to copy. It just takes a
+ * reference.
+ */
+ zero_page = mm_get_huge_zero_page(dst_mm);
+ set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
+ zero_page);
+ ret = 0;
+ goto out_unlock;
+ }
+
+ src_page = pmd_page(pmd);
+ VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
+ get_page(src_page);
+ page_dup_rmap(src_page, true);
+ add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
+ mm_inc_nr_ptes(dst_mm);
+ pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
+
+ pmdp_set_wrprotect(src_mm, addr, src_pmd);
+ pmd = pmd_mkold(pmd_wrprotect(pmd));
+ set_pmd_at(dst_mm, addr, dst_pmd, pmd);
+
+ ret = 0;
+out_unlock:
+ spin_unlock(src_ptl);
+ spin_unlock(dst_ptl);
+out:
+ return ret;
+}
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
+ pud_t *pud, int flags)
+{
+ pud_t _pud;
+
+ _pud = pud_mkyoung(*pud);
+ if (flags & FOLL_WRITE)
+ _pud = pud_mkdirty(_pud);
+ if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
+ pud, _pud, flags & FOLL_WRITE))
+ update_mmu_cache_pud(vma, addr, pud);
+}
+
+struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
+ pud_t *pud, int flags)
+{
+ unsigned long pfn = pud_pfn(*pud);
+ struct mm_struct *mm = vma->vm_mm;
+ struct dev_pagemap *pgmap;
+ struct page *page;
+
+ assert_spin_locked(pud_lockptr(mm, pud));
+
+ if (flags & FOLL_WRITE && !pud_write(*pud))
+ return NULL;
+
+ if (pud_present(*pud) && pud_devmap(*pud))
+ /* pass */;
+ else
+ return NULL;
+
+ if (flags & FOLL_TOUCH)
+ touch_pud(vma, addr, pud, flags);
+
+ /*
+ * device mapped pages can only be returned if the
+ * caller will manage the page reference count.
+ */
+ if (!(flags & FOLL_GET))
+ return ERR_PTR(-EEXIST);
+
+ pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
+ pgmap = get_dev_pagemap(pfn, NULL);
+ if (!pgmap)
+ return ERR_PTR(-EFAULT);
+ page = pfn_to_page(pfn);
+ get_page(page);
+ put_dev_pagemap(pgmap);
+
+ return page;
+}
+
+int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
+ pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
+ struct vm_area_struct *vma)
+{
+ spinlock_t *dst_ptl, *src_ptl;
+ pud_t pud;
+ int ret;
+
+ dst_ptl = pud_lock(dst_mm, dst_pud);
+ src_ptl = pud_lockptr(src_mm, src_pud);
+ spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
+
+ ret = -EAGAIN;
+ pud = *src_pud;
+ if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
+ goto out_unlock;
+
+ /*
+ * When page table lock is held, the huge zero pud should not be
+ * under splitting since we don't split the page itself, only pud to
+ * a page table.
+ */
+ if (is_huge_zero_pud(pud)) {
+ /* No huge zero pud yet */
+ }
+
+ pudp_set_wrprotect(src_mm, addr, src_pud);
+ pud = pud_mkold(pud_wrprotect(pud));
+ set_pud_at(dst_mm, addr, dst_pud, pud);
+
+ ret = 0;
+out_unlock:
+ spin_unlock(src_ptl);
+ spin_unlock(dst_ptl);
+ return ret;
+}
+
+void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
+{
+ pud_t entry;
+ unsigned long haddr;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
+
+ vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
+ if (unlikely(!pud_same(*vmf->pud, orig_pud)))
+ goto unlock;
+
+ entry = pud_mkyoung(orig_pud);
+ if (write)
+ entry = pud_mkdirty(entry);
+ haddr = vmf->address & HPAGE_PUD_MASK;
+ if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
+ update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
+
+unlock:
+ spin_unlock(vmf->ptl);
+}
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+
+void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
+{
+ pmd_t entry;
+ unsigned long haddr;
+ bool write = vmf->flags & FAULT_FLAG_WRITE;
+
+ vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
+ if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
+ goto unlock;
+
+ entry = pmd_mkyoung(orig_pmd);
+ if (write)
+ entry = pmd_mkdirty(entry);
+ haddr = vmf->address & HPAGE_PMD_MASK;
+ if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
+ update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
+
+unlock:
+ spin_unlock(vmf->ptl);
+}
+
+static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
+ pmd_t orig_pmd, struct page *page)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
+ struct mem_cgroup *memcg;
+ pgtable_t pgtable;
+ pmd_t _pmd;
+ int i;
+ vm_fault_t ret = 0;
+ struct page **pages;
+ unsigned long mmun_start; /* For mmu_notifiers */
+ unsigned long mmun_end; /* For mmu_notifiers */
+
+ pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
+ GFP_KERNEL);
+ if (unlikely(!pages)) {
+ ret |= VM_FAULT_OOM;
+ goto out;
+ }
+
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
+ vmf->address, page_to_nid(page));
+ if (unlikely(!pages[i] ||
+ mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
+ GFP_KERNEL, &memcg, false))) {
+ if (pages[i])
+ put_page(pages[i]);
+ while (--i >= 0) {
+ memcg = (void *)page_private(pages[i]);
+ set_page_private(pages[i], 0);
+ mem_cgroup_cancel_charge(pages[i], memcg,
+ false);
+ put_page(pages[i]);
+ }
+ kfree(pages);
+ ret |= VM_FAULT_OOM;
+ goto out;
+ }
+ set_page_private(pages[i], (unsigned long)memcg);
+ }
+
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ copy_user_highpage(pages[i], page + i,
+ haddr + PAGE_SIZE * i, vma);
+ __SetPageUptodate(pages[i]);
+ cond_resched();
+ }
+
+ mmun_start = haddr;
+ mmun_end = haddr + HPAGE_PMD_SIZE;
+ mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
+
+ vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
+ if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
+ goto out_free_pages;
+ VM_BUG_ON_PAGE(!PageHead(page), page);
+
+ /*
+ * Leave pmd empty until pte is filled note we must notify here as
+ * concurrent CPU thread might write to new page before the call to
+ * mmu_notifier_invalidate_range_end() happens which can lead to a
+ * device seeing memory write in different order than CPU.
+ *
+ * See Documentation/vm/mmu_notifier.rst
+ */
+ pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
+
+ pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
+ pmd_populate(vma->vm_mm, &_pmd, pgtable);
+
+ for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
+ pte_t entry;
+ entry = mk_pte(pages[i], vma->vm_page_prot);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ memcg = (void *)page_private(pages[i]);
+ set_page_private(pages[i], 0);
+ page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
+ mem_cgroup_commit_charge(pages[i], memcg, false, false);
+ lru_cache_add_active_or_unevictable(pages[i], vma);
+ vmf->pte = pte_offset_map(&_pmd, haddr);
+ VM_BUG_ON(!pte_none(*vmf->pte));
+ set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
+ pte_unmap(vmf->pte);
+ }
+ kfree(pages);
+
+ smp_wmb(); /* make pte visible before pmd */
+ pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
+ page_remove_rmap(page, true);
+ spin_unlock(vmf->ptl);
+
+ /*
+ * No need to double call mmu_notifier->invalidate_range() callback as
+ * the above pmdp_huge_clear_flush_notify() did already call it.
+ */
+ mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
+ mmun_end);
+
+ ret |= VM_FAULT_WRITE;
+ put_page(page);
+
+out:
+ return ret;
+
+out_free_pages:
+ spin_unlock(vmf->ptl);
+ mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ memcg = (void *)page_private(pages[i]);
+ set_page_private(pages[i], 0);
+ mem_cgroup_cancel_charge(pages[i], memcg, false);
+ put_page(pages[i]);
+ }
+ kfree(pages);
+ goto out;
+}
+
+vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct page *page = NULL, *new_page;
+ struct mem_cgroup *memcg;
+ unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
+ unsigned long mmun_start; /* For mmu_notifiers */
+ unsigned long mmun_end; /* For mmu_notifiers */
+ gfp_t huge_gfp; /* for allocation and charge */
+ vm_fault_t ret = 0;
+
+ vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
+ VM_BUG_ON_VMA(!vma->anon_vma, vma);
+ if (is_huge_zero_pmd(orig_pmd))
+ goto alloc;
+ spin_lock(vmf->ptl);
+ if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
+ goto out_unlock;
+
+ page = pmd_page(orig_pmd);
+ VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
+ /*
+ * We can only reuse the page if nobody else maps the huge page or it's
+ * part.
+ */
+ if (!trylock_page(page)) {
+ get_page(page);
+ spin_unlock(vmf->ptl);
+ lock_page(page);
+ spin_lock(vmf->ptl);
+ if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
+ unlock_page(page);
+ put_page(page);
+ goto out_unlock;
+ }
+ put_page(page);
+ }
+ if (reuse_swap_page(page, NULL)) {
+ pmd_t entry;
+ entry = pmd_mkyoung(orig_pmd);
+ entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
+ update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
+ ret |= VM_FAULT_WRITE;
+ unlock_page(page);
+ goto out_unlock;
+ }
+ unlock_page(page);
+ get_page(page);
+ spin_unlock(vmf->ptl);
+alloc:
+ if (transparent_hugepage_enabled(vma) &&
+ !transparent_hugepage_debug_cow()) {
+ huge_gfp = alloc_hugepage_direct_gfpmask(vma);
+ new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
+ } else
+ new_page = NULL;
+
+ if (likely(new_page)) {
+ prep_transhuge_page(new_page);
+ } else {
+ if (!page) {
+ split_huge_pmd(vma, vmf->pmd, vmf->address);
+ ret |= VM_FAULT_FALLBACK;
+ } else {
+ ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
+ if (ret & VM_FAULT_OOM) {
+ split_huge_pmd(vma, vmf->pmd, vmf->address);
+ ret |= VM_FAULT_FALLBACK;
+ }
+ put_page(page);
+ }
+ count_vm_event(THP_FAULT_FALLBACK);
+ goto out;
+ }
+
+ if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
+ huge_gfp, &memcg, true))) {
+ put_page(new_page);
+ split_huge_pmd(vma, vmf->pmd, vmf->address);
+ if (page)
+ put_page(page);
+ ret |= VM_FAULT_FALLBACK;
+ count_vm_event(THP_FAULT_FALLBACK);
+ goto out;
+ }
+
+ count_vm_event(THP_FAULT_ALLOC);
+
+ if (!page)
+ clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
+ else
+ copy_user_huge_page(new_page, page, vmf->address,
+ vma, HPAGE_PMD_NR);
+ __SetPageUptodate(new_page);
+
+ mmun_start = haddr;
+ mmun_end = haddr + HPAGE_PMD_SIZE;
+ mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
+
+ spin_lock(vmf->ptl);
+ if (page)
+ put_page(page);
+ if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
+ spin_unlock(vmf->ptl);
+ mem_cgroup_cancel_charge(new_page, memcg, true);
+ put_page(new_page);
+ goto out_mn;
+ } else {
+ pmd_t entry;
+ entry = mk_huge_pmd(new_page, vma->vm_page_prot);
+ entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+ pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
+ page_add_new_anon_rmap(new_page, vma, haddr, true);
+ mem_cgroup_commit_charge(new_page, memcg, false, true);
+ lru_cache_add_active_or_unevictable(new_page, vma);
+ set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
+ update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
+ if (!page) {
+ add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
+ } else {
+ VM_BUG_ON_PAGE(!PageHead(page), page);
+ page_remove_rmap(page, true);
+ put_page(page);
+ }
+ ret |= VM_FAULT_WRITE;
+ }
+ spin_unlock(vmf->ptl);
+out_mn:
+ /*
+ * No need to double call mmu_notifier->invalidate_range() callback as
+ * the above pmdp_huge_clear_flush_notify() did already call it.
+ */
+ mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
+ mmun_end);
+out:
+ return ret;
+out_unlock:
+ spin_unlock(vmf->ptl);
+ return ret;
+}
+
+/*
+ * FOLL_FORCE can write to even unwritable pmd's, but only
+ * after we've gone through a COW cycle and they are dirty.
+ */
+static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
+{
+ return pmd_write(pmd) ||
+ ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
+}
+
+struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
+ unsigned long addr,
+ pmd_t *pmd,
+ unsigned int flags)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ struct page *page = NULL;
+
+ assert_spin_locked(pmd_lockptr(mm, pmd));
+
+ if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
+ goto out;
+
+ /* Avoid dumping huge zero page */
+ if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
+ return ERR_PTR(-EFAULT);
+
+ /* Full NUMA hinting faults to serialise migration in fault paths */
+ if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
+ goto out;
+
+ page = pmd_page(*pmd);
+ VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
+ if (flags & FOLL_TOUCH)
+ touch_pmd(vma, addr, pmd, flags);
+ if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
+ /*
+ * We don't mlock() pte-mapped THPs. This way we can avoid
+ * leaking mlocked pages into non-VM_LOCKED VMAs.
+ *
+ * For anon THP:
+ *
+ * In most cases the pmd is the only mapping of the page as we
+ * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
+ * writable private mappings in populate_vma_page_range().
+ *
+ * The only scenario when we have the page shared here is if we
+ * mlocking read-only mapping shared over fork(). We skip
+ * mlocking such pages.
+ *
+ * For file THP:
+ *
+ * We can expect PageDoubleMap() to be stable under page lock:
+ * for file pages we set it in page_add_file_rmap(), which
+ * requires page to be locked.
+ */
+
+ if (PageAnon(page) && compound_mapcount(page) != 1)
+ goto skip_mlock;
+ if (PageDoubleMap(page) || !page->mapping)
+ goto skip_mlock;
+ if (!trylock_page(page))
+ goto skip_mlock;
+ lru_add_drain();
+ if (page->mapping && !PageDoubleMap(page))
+ mlock_vma_page(page);
+ unlock_page(page);
+ }
+skip_mlock:
+ page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
+ VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
+ if (flags & FOLL_GET)
+ get_page(page);
+
+out:
+ return page;
+}
+
+/* NUMA hinting page fault entry point for trans huge pmds */
+vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct anon_vma *anon_vma = NULL;
+ struct page *page;
+ unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
+ int page_nid = -1, this_nid = numa_node_id();
+ int target_nid, last_cpupid = -1;
+ bool page_locked;
+ bool migrated = false;
+ bool was_writable;
+ int flags = 0;
+
+ vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
+ if (unlikely(!pmd_same(pmd, *vmf->pmd)))
+ goto out_unlock;
+
+ /*
+ * If there are potential migrations, wait for completion and retry
+ * without disrupting NUMA hinting information. Do not relock and
+ * check_same as the page may no longer be mapped.
+ */
+ if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
+ page = pmd_page(*vmf->pmd);
+ if (!get_page_unless_zero(page))
+ goto out_unlock;
+ spin_unlock(vmf->ptl);
+ wait_on_page_locked(page);
+ put_page(page);
+ goto out;
+ }
+
+ page = pmd_page(pmd);
+ BUG_ON(is_huge_zero_page(page));
+ page_nid = page_to_nid(page);
+ last_cpupid = page_cpupid_last(page);
+ count_vm_numa_event(NUMA_HINT_FAULTS);
+ if (page_nid == this_nid) {
+ count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
+ flags |= TNF_FAULT_LOCAL;
+ }
+
+ /* See similar comment in do_numa_page for explanation */
+ if (!pmd_savedwrite(pmd))
+ flags |= TNF_NO_GROUP;
+
+ /*
+ * Acquire the page lock to serialise THP migrations but avoid dropping
+ * page_table_lock if at all possible
+ */
+ page_locked = trylock_page(page);
+ target_nid = mpol_misplaced(page, vma, haddr);
+ if (target_nid == -1) {
+ /* If the page was locked, there are no parallel migrations */
+ if (page_locked)
+ goto clear_pmdnuma;
+ }
+
+ /* Migration could have started since the pmd_trans_migrating check */
+ if (!page_locked) {
+ page_nid = -1;
+ if (!get_page_unless_zero(page))
+ goto out_unlock;
+ spin_unlock(vmf->ptl);
+ wait_on_page_locked(page);
+ put_page(page);
+ goto out;
+ }
+
+ /*
+ * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
+ * to serialises splits
+ */
+ get_page(page);
+ spin_unlock(vmf->ptl);
+ anon_vma = page_lock_anon_vma_read(page);
+
+ /* Confirm the PMD did not change while page_table_lock was released */
+ spin_lock(vmf->ptl);
+ if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
+ unlock_page(page);
+ put_page(page);
+ page_nid = -1;
+ goto out_unlock;
+ }
+
+ /* Bail if we fail to protect against THP splits for any reason */
+ if (unlikely(!anon_vma)) {
+ put_page(page);
+ page_nid = -1;
+ goto clear_pmdnuma;
+ }
+
+ /*
+ * Since we took the NUMA fault, we must have observed the !accessible
+ * bit. Make sure all other CPUs agree with that, to avoid them
+ * modifying the page we're about to migrate.
+ *
+ * Must be done under PTL such that we'll observe the relevant
+ * inc_tlb_flush_pending().
+ *
+ * We are not sure a pending tlb flush here is for a huge page
+ * mapping or not. Hence use the tlb range variant
+ */
+ if (mm_tlb_flush_pending(vma->vm_mm))
+ flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
+
+ /*
+ * Migrate the THP to the requested node, returns with page unlocked
+ * and access rights restored.
+ */
+ spin_unlock(vmf->ptl);
+
+ migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
+ vmf->pmd, pmd, vmf->address, page, target_nid);
+ if (migrated) {
+ flags |= TNF_MIGRATED;
+ page_nid = target_nid;
+ } else
+ flags |= TNF_MIGRATE_FAIL;
+
+ goto out;
+clear_pmdnuma:
+ BUG_ON(!PageLocked(page));
+ was_writable = pmd_savedwrite(pmd);
+ pmd = pmd_modify(pmd, vma->vm_page_prot);
+ pmd = pmd_mkyoung(pmd);
+ if (was_writable)
+ pmd = pmd_mkwrite(pmd);
+ set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
+ update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
+ unlock_page(page);
+out_unlock:
+ spin_unlock(vmf->ptl);
+
+out:
+ if (anon_vma)
+ page_unlock_anon_vma_read(anon_vma);
+
+ if (page_nid != -1)
+ task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
+ flags);
+
+ return 0;
+}
+
+/*
+ * Return true if we do MADV_FREE successfully on entire pmd page.
+ * Otherwise, return false.
+ */
+bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ pmd_t *pmd, unsigned long addr, unsigned long next)
+{
+ spinlock_t *ptl;
+ pmd_t orig_pmd;
+ struct page *page;
+ struct mm_struct *mm = tlb->mm;
+ bool ret = false;
+
+ tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
+
+ ptl = pmd_trans_huge_lock(pmd, vma);
+ if (!ptl)
+ goto out_unlocked;
+
+ orig_pmd = *pmd;
+ if (is_huge_zero_pmd(orig_pmd))
+ goto out;
+
+ if (unlikely(!pmd_present(orig_pmd))) {
+ VM_BUG_ON(thp_migration_supported() &&
+ !is_pmd_migration_entry(orig_pmd));
+ goto out;
+ }
+
+ page = pmd_page(orig_pmd);
+ /*
+ * If other processes are mapping this page, we couldn't discard
+ * the page unless they all do MADV_FREE so let's skip the page.
+ */
+ if (page_mapcount(page) != 1)
+ goto out;
+
+ if (!trylock_page(page))
+ goto out;
+
+ /*
+ * If user want to discard part-pages of THP, split it so MADV_FREE
+ * will deactivate only them.
+ */
+ if (next - addr != HPAGE_PMD_SIZE) {
+ get_page(page);
+ spin_unlock(ptl);
+ split_huge_page(page);
+ unlock_page(page);
+ put_page(page);
+ goto out_unlocked;
+ }
+
+ if (PageDirty(page))
+ ClearPageDirty(page);
+ unlock_page(page);
+
+ if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
+ pmdp_invalidate(vma, addr, pmd);
+ orig_pmd = pmd_mkold(orig_pmd);
+ orig_pmd = pmd_mkclean(orig_pmd);
+
+ set_pmd_at(mm, addr, pmd, orig_pmd);
+ tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+ }
+
+ mark_page_lazyfree(page);
+ ret = true;
+out:
+ spin_unlock(ptl);
+out_unlocked:
+ return ret;
+}
+
+static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
+{
+ pgtable_t pgtable;
+
+ pgtable = pgtable_trans_huge_withdraw(mm, pmd);
+ pte_free(mm, pgtable);
+ mm_dec_nr_ptes(mm);
+}
+
+int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ pmd_t *pmd, unsigned long addr)
+{
+ pmd_t orig_pmd;
+ spinlock_t *ptl;
+
+ tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
+
+ ptl = __pmd_trans_huge_lock(pmd, vma);
+ if (!ptl)
+ return 0;
+ /*
+ * For architectures like ppc64 we look at deposited pgtable
+ * when calling pmdp_huge_get_and_clear. So do the
+ * pgtable_trans_huge_withdraw after finishing pmdp related
+ * operations.
+ */
+ orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
+ tlb->fullmm);
+ tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+ if (vma_is_dax(vma)) {
+ if (arch_needs_pgtable_deposit())
+ zap_deposited_table(tlb->mm, pmd);
+ spin_unlock(ptl);
+ if (is_huge_zero_pmd(orig_pmd))
+ tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
+ } else if (is_huge_zero_pmd(orig_pmd)) {
+ zap_deposited_table(tlb->mm, pmd);
+ spin_unlock(ptl);
+ tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
+ } else {
+ struct page *page = NULL;
+ int flush_needed = 1;
+
+ if (pmd_present(orig_pmd)) {
+ page = pmd_page(orig_pmd);
+ page_remove_rmap(page, true);
+ VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
+ VM_BUG_ON_PAGE(!PageHead(page), page);
+ } else if (thp_migration_supported()) {
+ swp_entry_t entry;
+
+ VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
+ entry = pmd_to_swp_entry(orig_pmd);
+ page = pfn_to_page(swp_offset(entry));
+ flush_needed = 0;
+ } else
+ WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
+
+ if (PageAnon(page)) {
+ zap_deposited_table(tlb->mm, pmd);
+ add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
+ } else {
+ if (arch_needs_pgtable_deposit())
+ zap_deposited_table(tlb->mm, pmd);
+ add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
+ }
+
+ spin_unlock(ptl);
+ if (flush_needed)
+ tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
+ }
+ return 1;
+}
+
+#ifndef pmd_move_must_withdraw
+static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
+ spinlock_t *old_pmd_ptl,
+ struct vm_area_struct *vma)
+{
+ /*
+ * With split pmd lock we also need to move preallocated
+ * PTE page table if new_pmd is on different PMD page table.
+ *
+ * We also don't deposit and withdraw tables for file pages.
+ */
+ return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
+}
+#endif
+
+static pmd_t move_soft_dirty_pmd(pmd_t pmd)
+{
+#ifdef CONFIG_MEM_SOFT_DIRTY
+ if (unlikely(is_pmd_migration_entry(pmd)))
+ pmd = pmd_swp_mksoft_dirty(pmd);
+ else if (pmd_present(pmd))
+ pmd = pmd_mksoft_dirty(pmd);
+#endif
+ return pmd;
+}
+
+bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
+ unsigned long new_addr, unsigned long old_end,
+ pmd_t *old_pmd, pmd_t *new_pmd)
+{
+ spinlock_t *old_ptl, *new_ptl;
+ pmd_t pmd;
+ struct mm_struct *mm = vma->vm_mm;
+ bool force_flush = false;
+
+ if ((old_addr & ~HPAGE_PMD_MASK) ||
+ (new_addr & ~HPAGE_PMD_MASK) ||
+ old_end - old_addr < HPAGE_PMD_SIZE)
+ return false;
+
+ /*
+ * The destination pmd shouldn't be established, free_pgtables()
+ * should have release it.
+ */
+ if (WARN_ON(!pmd_none(*new_pmd))) {
+ VM_BUG_ON(pmd_trans_huge(*new_pmd));
+ return false;
+ }
+
+ /*
+ * We don't have to worry about the ordering of src and dst
+ * ptlocks because exclusive mmap_sem prevents deadlock.
+ */
+ old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
+ if (old_ptl) {
+ new_ptl = pmd_lockptr(mm, new_pmd);
+ if (new_ptl != old_ptl)
+ spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
+ pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
+ if (pmd_present(pmd))
+ force_flush = true;
+ VM_BUG_ON(!pmd_none(*new_pmd));
+
+ if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
+ pgtable_t pgtable;
+ pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
+ pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
+ }
+ pmd = move_soft_dirty_pmd(pmd);
+ set_pmd_at(mm, new_addr, new_pmd, pmd);
+ if (force_flush)
+ flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
+ if (new_ptl != old_ptl)
+ spin_unlock(new_ptl);
+ spin_unlock(old_ptl);
+ return true;
+ }
+ return false;
+}
+
+/*
+ * Returns
+ * - 0 if PMD could not be locked
+ * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
+ * - HPAGE_PMD_NR is protections changed and TLB flush necessary
+ */
+int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+ unsigned long addr, pgprot_t newprot, int prot_numa)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ spinlock_t *ptl;
+ pmd_t entry;
+ bool preserve_write;
+ int ret;
+
+ ptl = __pmd_trans_huge_lock(pmd, vma);
+ if (!ptl)
+ return 0;
+
+ preserve_write = prot_numa && pmd_write(*pmd);
+ ret = 1;
+
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+ if (is_swap_pmd(*pmd)) {
+ swp_entry_t entry = pmd_to_swp_entry(*pmd);
+
+ VM_BUG_ON(!is_pmd_migration_entry(*pmd));
+ if (is_write_migration_entry(entry)) {
+ pmd_t newpmd;
+ /*
+ * A protection check is difficult so
+ * just be safe and disable write
+ */
+ make_migration_entry_read(&entry);
+ newpmd = swp_entry_to_pmd(entry);
+ if (pmd_swp_soft_dirty(*pmd))
+ newpmd = pmd_swp_mksoft_dirty(newpmd);
+ set_pmd_at(mm, addr, pmd, newpmd);
+ }
+ goto unlock;
+ }
+#endif
+
+ /*
+ * Avoid trapping faults against the zero page. The read-only
+ * data is likely to be read-cached on the local CPU and
+ * local/remote hits to the zero page are not interesting.
+ */
+ if (prot_numa && is_huge_zero_pmd(*pmd))
+ goto unlock;
+
+ if (prot_numa && pmd_protnone(*pmd))
+ goto unlock;
+
+ /*
+ * In case prot_numa, we are under down_read(mmap_sem). It's critical
+ * to not clear pmd intermittently to avoid race with MADV_DONTNEED
+ * which is also under down_read(mmap_sem):
+ *
+ * CPU0: CPU1:
+ * change_huge_pmd(prot_numa=1)
+ * pmdp_huge_get_and_clear_notify()
+ * madvise_dontneed()
+ * zap_pmd_range()
+ * pmd_trans_huge(*pmd) == 0 (without ptl)
+ * // skip the pmd
+ * set_pmd_at();
+ * // pmd is re-established
+ *
+ * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
+ * which may break userspace.
+ *
+ * pmdp_invalidate() is required to make sure we don't miss
+ * dirty/young flags set by hardware.
+ */
+ entry = pmdp_invalidate(vma, addr, pmd);
+
+ entry = pmd_modify(entry, newprot);
+ if (preserve_write)
+ entry = pmd_mk_savedwrite(entry);
+ ret = HPAGE_PMD_NR;
+ set_pmd_at(mm, addr, pmd, entry);
+ BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
+unlock:
+ spin_unlock(ptl);
+ return ret;
+}
+
+/*
+ * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
+ *
+ * Note that if it returns page table lock pointer, this routine returns without
+ * unlocking page table lock. So callers must unlock it.
+ */
+spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
+{
+ spinlock_t *ptl;
+ ptl = pmd_lock(vma->vm_mm, pmd);
+ if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
+ pmd_devmap(*pmd)))
+ return ptl;
+ spin_unlock(ptl);
+ return NULL;
+}
+
+/*
+ * Returns true if a given pud maps a thp, false otherwise.
+ *
+ * Note that if it returns true, this routine returns without unlocking page
+ * table lock. So callers must unlock it.
+ */
+spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
+{
+ spinlock_t *ptl;
+
+ ptl = pud_lock(vma->vm_mm, pud);
+ if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
+ return ptl;
+ spin_unlock(ptl);
+ return NULL;
+}
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
+ pud_t *pud, unsigned long addr)
+{
+ pud_t orig_pud;
+ spinlock_t *ptl;
+
+ ptl = __pud_trans_huge_lock(pud, vma);
+ if (!ptl)
+ return 0;
+ /*
+ * For architectures like ppc64 we look at deposited pgtable
+ * when calling pudp_huge_get_and_clear. So do the
+ * pgtable_trans_huge_withdraw after finishing pudp related
+ * operations.
+ */
+ orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
+ tlb->fullmm);
+ tlb_remove_pud_tlb_entry(tlb, pud, addr);
+ if (vma_is_dax(vma)) {
+ spin_unlock(ptl);
+ /* No zero page support yet */
+ } else {
+ /* No support for anonymous PUD pages yet */
+ BUG();
+ }
+ return 1;
+}
+
+static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
+ unsigned long haddr)
+{
+ VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
+ VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
+ VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
+ VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
+
+ count_vm_event(THP_SPLIT_PUD);
+
+ pudp_huge_clear_flush_notify(vma, haddr, pud);
+}
+
+void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
+ unsigned long address)
+{
+ spinlock_t *ptl;
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long haddr = address & HPAGE_PUD_MASK;
+
+ mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
+ ptl = pud_lock(mm, pud);
+ if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
+ goto out;
+ __split_huge_pud_locked(vma, pud, haddr);
+
+out:
+ spin_unlock(ptl);
+ /*
+ * No need to double call mmu_notifier->invalidate_range() callback as
+ * the above pudp_huge_clear_flush_notify() did already call it.
+ */
+ mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
+ HPAGE_PUD_SIZE);
+}
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+
+static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
+ unsigned long haddr, pmd_t *pmd)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ pgtable_t pgtable;
+ pmd_t _pmd;
+ int i;
+
+ /*
+ * Leave pmd empty until pte is filled note that it is fine to delay
+ * notification until mmu_notifier_invalidate_range_end() as we are
+ * replacing a zero pmd write protected page with a zero pte write
+ * protected page.
+ *
+ * See Documentation/vm/mmu_notifier.rst
+ */
+ pmdp_huge_clear_flush(vma, haddr, pmd);
+
+ pgtable = pgtable_trans_huge_withdraw(mm, pmd);
+ pmd_populate(mm, &_pmd, pgtable);
+
+ for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
+ pte_t *pte, entry;
+ entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
+ entry = pte_mkspecial(entry);
+ pte = pte_offset_map(&_pmd, haddr);
+ VM_BUG_ON(!pte_none(*pte));
+ set_pte_at(mm, haddr, pte, entry);
+ pte_unmap(pte);
+ }
+ smp_wmb(); /* make pte visible before pmd */
+ pmd_populate(mm, pmd, pgtable);
+}
+
+static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
+ unsigned long haddr, bool freeze)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ struct page *page;
+ pgtable_t pgtable;
+ pmd_t old_pmd, _pmd;
+ bool young, write, soft_dirty, pmd_migration = false;
+ unsigned long addr;
+ int i;
+
+ VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
+ VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
+ VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
+ VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
+ && !pmd_devmap(*pmd));
+
+ count_vm_event(THP_SPLIT_PMD);
+
+ if (!vma_is_anonymous(vma)) {
+ _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
+ /*
+ * We are going to unmap this huge page. So
+ * just go ahead and zap it
+ */
+ if (arch_needs_pgtable_deposit())
+ zap_deposited_table(mm, pmd);
+ if (vma_is_dax(vma))
+ return;
+ page = pmd_page(_pmd);
+ if (!PageDirty(page) && pmd_dirty(_pmd))
+ set_page_dirty(page);
+ if (!PageReferenced(page) && pmd_young(_pmd))
+ SetPageReferenced(page);
+ page_remove_rmap(page, true);
+ put_page(page);
+ add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
+ return;
+ } else if (is_huge_zero_pmd(*pmd)) {
+ /*
+ * FIXME: Do we want to invalidate secondary mmu by calling
+ * mmu_notifier_invalidate_range() see comments below inside
+ * __split_huge_pmd() ?
+ *
+ * We are going from a zero huge page write protected to zero
+ * small page also write protected so it does not seems useful
+ * to invalidate secondary mmu at this time.
+ */
+ return __split_huge_zero_page_pmd(vma, haddr, 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_pmd_tlb_range();" we first mark the
+ * current pmd notpresent (atomically because here the pmd_trans_huge
+ * 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.
+ */
+ old_pmd = pmdp_invalidate(vma, haddr, pmd);
+
+ pmd_migration = is_pmd_migration_entry(old_pmd);
+ if (unlikely(pmd_migration)) {
+ swp_entry_t entry;
+
+ entry = pmd_to_swp_entry(old_pmd);
+ page = pfn_to_page(swp_offset(entry));
+ write = is_write_migration_entry(entry);
+ young = false;
+ soft_dirty = pmd_swp_soft_dirty(old_pmd);
+ } else {
+ page = pmd_page(old_pmd);
+ if (pmd_dirty(old_pmd))
+ SetPageDirty(page);
+ write = pmd_write(old_pmd);
+ young = pmd_young(old_pmd);
+ soft_dirty = pmd_soft_dirty(old_pmd);
+ }
+ VM_BUG_ON_PAGE(!page_count(page), page);
+ page_ref_add(page, HPAGE_PMD_NR - 1);
+
+ /*
+ * Withdraw the table only after we mark the pmd entry invalid.
+ * This's critical for some architectures (Power).
+ */
+ pgtable = pgtable_trans_huge_withdraw(mm, pmd);
+ pmd_populate(mm, &_pmd, pgtable);
+
+ for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
+ pte_t entry, *pte;
+ /*
+ * Note that NUMA hinting access restrictions are not
+ * transferred to avoid any possibility of altering
+ * permissions across VMAs.
+ */
+ if (freeze || pmd_migration) {
+ swp_entry_t swp_entry;
+ swp_entry = make_migration_entry(page + i, write);
+ entry = swp_entry_to_pte(swp_entry);
+ if (soft_dirty)
+ entry = pte_swp_mksoft_dirty(entry);
+ } else {
+ entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
+ entry = maybe_mkwrite(entry, vma);
+ if (!write)
+ entry = pte_wrprotect(entry);
+ if (!young)
+ entry = pte_mkold(entry);
+ if (soft_dirty)
+ entry = pte_mksoft_dirty(entry);
+ }
+ pte = pte_offset_map(&_pmd, addr);
+ BUG_ON(!pte_none(*pte));
+ set_pte_at(mm, addr, pte, entry);
+ atomic_inc(&page[i]._mapcount);
+ pte_unmap(pte);
+ }
+
+ /*
+ * Set PG_double_map before dropping compound_mapcount to avoid
+ * false-negative page_mapped().
+ */
+ if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ atomic_inc(&page[i]._mapcount);
+ }
+
+ if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
+ /* Last compound_mapcount is gone. */
+ __dec_node_page_state(page, NR_ANON_THPS);
+ if (TestClearPageDoubleMap(page)) {
+ /* No need in mapcount reference anymore */
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ atomic_dec(&page[i]._mapcount);
+ }
+ }
+
+ smp_wmb(); /* make pte visible before pmd */
+ pmd_populate(mm, pmd, pgtable);
+
+ if (freeze) {
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ page_remove_rmap(page + i, false);
+ put_page(page + i);
+ }
+ }
+}
+
+void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+ unsigned long address, bool freeze, struct page *page)
+{
+ spinlock_t *ptl;
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long haddr = address & HPAGE_PMD_MASK;
+
+ mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
+ ptl = pmd_lock(mm, pmd);
+
+ /*
+ * If caller asks to setup a migration entries, we need a page to check
+ * pmd against. Otherwise we can end up replacing wrong page.
+ */
+ VM_BUG_ON(freeze && !page);
+ if (page && page != pmd_page(*pmd))
+ goto out;
+
+ if (pmd_trans_huge(*pmd)) {
+ page = pmd_page(*pmd);
+ if (PageMlocked(page))
+ clear_page_mlock(page);
+ } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
+ goto out;
+ __split_huge_pmd_locked(vma, pmd, haddr, freeze);
+out:
+ spin_unlock(ptl);
+ /*
+ * No need to double call mmu_notifier->invalidate_range() callback.
+ * They are 3 cases to consider inside __split_huge_pmd_locked():
+ * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
+ * 2) __split_huge_zero_page_pmd() read only zero page and any write
+ * fault will trigger a flush_notify before pointing to a new page
+ * (it is fine if the secondary mmu keeps pointing to the old zero
+ * page in the meantime)
+ * 3) Split a huge pmd into pte pointing to the same page. No need
+ * to invalidate secondary tlb entry they are all still valid.
+ * any further changes to individual pte will notify. So no need
+ * to call mmu_notifier->invalidate_range()
+ */
+ mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
+ HPAGE_PMD_SIZE);
+}
+
+void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
+ bool freeze, struct page *page)
+{
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+
+ pgd = pgd_offset(vma->vm_mm, address);
+ if (!pgd_present(*pgd))
+ return;
+
+ p4d = p4d_offset(pgd, address);
+ if (!p4d_present(*p4d))
+ return;
+
+ pud = pud_offset(p4d, address);
+ if (!pud_present(*pud))
+ return;
+
+ pmd = pmd_offset(pud, address);
+
+ __split_huge_pmd(vma, pmd, address, freeze, page);
+}
+
+void vma_adjust_trans_huge(struct vm_area_struct *vma,
+ unsigned long start,
+ unsigned long end,
+ long adjust_next)
+{
+ /*
+ * If the new start address isn't hpage aligned and it could
+ * previously contain an hugepage: check if we need to split
+ * an huge pmd.
+ */
+ if (start & ~HPAGE_PMD_MASK &&
+ (start & HPAGE_PMD_MASK) >= vma->vm_start &&
+ (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
+ split_huge_pmd_address(vma, start, false, NULL);
+
+ /*
+ * If the new end address isn't hpage aligned and it could
+ * previously contain an hugepage: check if we need to split
+ * an huge pmd.
+ */
+ if (end & ~HPAGE_PMD_MASK &&
+ (end & HPAGE_PMD_MASK) >= vma->vm_start &&
+ (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
+ split_huge_pmd_address(vma, end, false, NULL);
+
+ /*
+ * If we're also updating the vma->vm_next->vm_start, if the new
+ * vm_next->vm_start isn't page aligned and it could previously
+ * contain an hugepage: check if we need to split an huge pmd.
+ */
+ if (adjust_next > 0) {
+ struct vm_area_struct *next = vma->vm_next;
+ unsigned long nstart = next->vm_start;
+ nstart += adjust_next << PAGE_SHIFT;
+ if (nstart & ~HPAGE_PMD_MASK &&
+ (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
+ (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
+ split_huge_pmd_address(next, nstart, false, NULL);
+ }
+}
+
+static void unmap_page(struct page *page)
+{
+ enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
+ TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
+ bool unmap_success;
+
+ VM_BUG_ON_PAGE(!PageHead(page), page);
+
+ if (PageAnon(page))
+ ttu_flags |= TTU_SPLIT_FREEZE;
+
+ unmap_success = try_to_unmap(page, ttu_flags);
+ VM_BUG_ON_PAGE(!unmap_success, page);
+}
+
+static void remap_page(struct page *page)
+{
+ int i;
+ if (PageTransHuge(page)) {
+ remove_migration_ptes(page, page, true);
+ } else {
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ remove_migration_ptes(page + i, page + i, true);
+ }
+}
+
+static void __split_huge_page_tail(struct page *head, int tail,
+ struct lruvec *lruvec, struct list_head *list)
+{
+ struct page *page_tail = head + tail;
+
+ VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
+
+ /*
+ * Clone page flags before unfreezing refcount.
+ *
+ * After successful get_page_unless_zero() might follow flags change,
+ * for exmaple lock_page() which set PG_waiters.
+ */
+ page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
+ page_tail->flags |= (head->flags &
+ ((1L << PG_referenced) |
+ (1L << PG_swapbacked) |
+ (1L << PG_swapcache) |
+ (1L << PG_mlocked) |
+ (1L << PG_uptodate) |
+ (1L << PG_active) |
+ (1L << PG_locked) |
+ (1L << PG_unevictable) |
+ (1L << PG_dirty)));
+
+ /* ->mapping in first tail page is compound_mapcount */
+ VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
+ page_tail);
+ page_tail->mapping = head->mapping;
+ page_tail->index = head->index + tail;
+
+ /* Page flags must be visible before we make the page non-compound. */
+ smp_wmb();
+
+ /*
+ * Clear PageTail before unfreezing page refcount.
+ *
+ * After successful get_page_unless_zero() might follow put_page()
+ * which needs correct compound_head().
+ */
+ clear_compound_head(page_tail);
+
+ /* Finally unfreeze refcount. Additional reference from page cache. */
+ page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
+ PageSwapCache(head)));
+
+ if (page_is_young(head))
+ set_page_young(page_tail);
+ if (page_is_idle(head))
+ set_page_idle(page_tail);
+
+ page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
+
+ /*
+ * always add to the tail because some iterators expect new
+ * pages to show after the currently processed elements - e.g.
+ * migrate_pages
+ */
+ lru_add_page_tail(head, page_tail, lruvec, list);
+}
+
+static void __split_huge_page(struct page *page, struct list_head *list,
+ pgoff_t end, unsigned long flags)
+{
+ struct page *head = compound_head(page);
+ struct zone *zone = page_zone(head);
+ struct lruvec *lruvec;
+ int i;
+
+ lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
+
+ /* complete memcg works before add pages to LRU */
+ mem_cgroup_split_huge_fixup(head);
+
+ for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
+ __split_huge_page_tail(head, i, lruvec, list);
+ /* Some pages can be beyond i_size: drop them from page cache */
+ if (head[i].index >= end) {
+ ClearPageDirty(head + i);
+ __delete_from_page_cache(head + i, NULL);
+ if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
+ shmem_uncharge(head->mapping->host, 1);
+ put_page(head + i);
+ }
+ }
+
+ ClearPageCompound(head);
+ /* See comment in __split_huge_page_tail() */
+ if (PageAnon(head)) {
+ /* Additional pin to radix tree of swap cache */
+ if (PageSwapCache(head))
+ page_ref_add(head, 2);
+ else
+ page_ref_inc(head);
+ } else {
+ /* Additional pin to radix tree */
+ page_ref_add(head, 2);
+ xa_unlock(&head->mapping->i_pages);
+ }
+
+ spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
+
+ remap_page(head);
+
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ struct page *subpage = head + i;
+ if (subpage == page)
+ continue;
+ unlock_page(subpage);
+
+ /*
+ * Subpages 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(subpage);
+ }
+}
+
+int total_mapcount(struct page *page)
+{
+ int i, compound, ret;
+
+ VM_BUG_ON_PAGE(PageTail(page), page);
+
+ if (likely(!PageCompound(page)))
+ return atomic_read(&page->_mapcount) + 1;
+
+ compound = compound_mapcount(page);
+ if (PageHuge(page))
+ return compound;
+ ret = compound;
+ for (i = 0; i < HPAGE_PMD_NR; i++)
+ ret += atomic_read(&page[i]._mapcount) + 1;
+ /* File pages has compound_mapcount included in _mapcount */
+ if (!PageAnon(page))
+ return ret - compound * HPAGE_PMD_NR;
+ if (PageDoubleMap(page))
+ ret -= HPAGE_PMD_NR;
+ return ret;
+}
+
+/*
+ * This calculates accurately how many mappings a transparent hugepage
+ * has (unlike page_mapcount() which isn't fully accurate). This full
+ * accuracy is primarily needed to know if copy-on-write faults can
+ * reuse the page and change the mapping to read-write instead of
+ * copying them. At the same time this returns the total_mapcount too.
+ *
+ * The function returns the highest mapcount any one of the subpages
+ * has. If the return value is one, even if different processes are
+ * mapping different subpages of the transparent hugepage, they can
+ * all reuse it, because each process is reusing a different subpage.
+ *
+ * The total_mapcount is instead counting all virtual mappings of the
+ * subpages. If the total_mapcount is equal to "one", it tells the
+ * caller all mappings belong to the same "mm" and in turn the
+ * anon_vma of the transparent hugepage can become the vma->anon_vma
+ * local one as no other process may be mapping any of the subpages.
+ *
+ * It would be more accurate to replace page_mapcount() with
+ * page_trans_huge_mapcount(), however we only use
+ * page_trans_huge_mapcount() in the copy-on-write faults where we
+ * need full accuracy to avoid breaking page pinning, because
+ * page_trans_huge_mapcount() is slower than page_mapcount().
+ */
+int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
+{
+ int i, ret, _total_mapcount, mapcount;
+
+ /* hugetlbfs shouldn't call it */
+ VM_BUG_ON_PAGE(PageHuge(page), page);
+
+ if (likely(!PageTransCompound(page))) {
+ mapcount = atomic_read(&page->_mapcount) + 1;
+ if (total_mapcount)
+ *total_mapcount = mapcount;
+ return mapcount;
+ }
+
+ page = compound_head(page);
+
+ _total_mapcount = ret = 0;
+ for (i = 0; i < HPAGE_PMD_NR; i++) {
+ mapcount = atomic_read(&page[i]._mapcount) + 1;
+ ret = max(ret, mapcount);
+ _total_mapcount += mapcount;
+ }
+ if (PageDoubleMap(page)) {
+ ret -= 1;
+ _total_mapcount -= HPAGE_PMD_NR;
+ }
+ mapcount = compound_mapcount(page);
+ ret += mapcount;
+ _total_mapcount += mapcount;
+ if (total_mapcount)
+ *total_mapcount = _total_mapcount;
+ return ret;
+}
+
+/* Racy check whether the huge page can be split */
+bool can_split_huge_page(struct page *page, int *pextra_pins)
+{
+ int extra_pins;
+
+ /* Additional pins from radix tree */
+ if (PageAnon(page))
+ extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
+ else
+ extra_pins = HPAGE_PMD_NR;
+ if (pextra_pins)
+ *pextra_pins = extra_pins;
+ return total_mapcount(page) == page_count(page) - extra_pins - 1;
+}
+
+/*
+ * This function splits huge page into normal pages. @page can point to any
+ * subpage of huge page to split. Split doesn't change the position of @page.
+ *
+ * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
+ * The huge page must be locked.
+ *
+ * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
+ *
+ * Both head page and tail pages will inherit mapping, flags, and so on from
+ * the hugepage.
+ *
+ * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
+ * they are not mapped.
+ *
+ * Returns 0 if the hugepage is split successfully.
+ * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
+ * us.
+ */
+int split_huge_page_to_list(struct page *page, struct list_head *list)
+{
+ struct page *head = compound_head(page);
+ struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
+ struct anon_vma *anon_vma = NULL;
+ struct address_space *mapping = NULL;
+ int count, mapcount, extra_pins, ret;
+ bool mlocked;
+ unsigned long flags;
+ pgoff_t end;
+
+ VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+ VM_BUG_ON_PAGE(!PageCompound(page), page);
+
+ if (PageWriteback(page))
+ return -EBUSY;
+
+ if (PageAnon(head)) {
+ /*
+ * The caller does not necessarily hold an mmap_sem that would
+ * prevent the anon_vma disappearing so we first we take a
+ * reference to it and then lock the anon_vma for write. This
+ * is similar to page_lock_anon_vma_read except the write lock
+ * is taken to serialise against parallel split or collapse
+ * operations.
+ */
+ anon_vma = page_get_anon_vma(head);
+ if (!anon_vma) {
+ ret = -EBUSY;
+ goto out;
+ }
+ end = -1;
+ mapping = NULL;
+ anon_vma_lock_write(anon_vma);
+ } else {
+ mapping = head->mapping;
+
+ /* Truncated ? */
+ if (!mapping) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ anon_vma = NULL;
+ i_mmap_lock_read(mapping);
+
+ /*
+ *__split_huge_page() may need to trim off pages beyond EOF:
+ * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
+ * which cannot be nested inside the page tree lock. So note
+ * end now: i_size itself may be changed at any moment, but
+ * head page lock is good enough to serialize the trimming.
+ */
+ end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
+ }
+
+ /*
+ * Racy check if we can split the page, before unmap_page() will
+ * split PMDs
+ */
+ if (!can_split_huge_page(head, &extra_pins)) {
+ ret = -EBUSY;
+ goto out_unlock;
+ }
+
+ mlocked = PageMlocked(page);
+ unmap_page(head);
+ VM_BUG_ON_PAGE(compound_mapcount(head), head);
+
+ /* Make sure the page is not on per-CPU pagevec as it takes pin */
+ if (mlocked)
+ lru_add_drain();
+
+ /* prevent PageLRU to go away from under us, and freeze lru stats */
+ spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
+
+ if (mapping) {
+ void **pslot;
+
+ xa_lock(&mapping->i_pages);
+ pslot = radix_tree_lookup_slot(&mapping->i_pages,
+ page_index(head));
+ /*
+ * Check if the head page is present in radix tree.
+ * We assume all tail are present too, if head is there.
+ */
+ if (radix_tree_deref_slot_protected(pslot,
+ &mapping->i_pages.xa_lock) != head)
+ goto fail;
+ }
+
+ /* Prevent deferred_split_scan() touching ->_refcount */
+ spin_lock(&pgdata->split_queue_lock);
+ count = page_count(head);
+ mapcount = total_mapcount(head);
+ if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
+ if (!list_empty(page_deferred_list(head))) {
+ pgdata->split_queue_len--;
+ list_del(page_deferred_list(head));
+ }
+ if (mapping)
+ __dec_node_page_state(page, NR_SHMEM_THPS);
+ spin_unlock(&pgdata->split_queue_lock);
+ __split_huge_page(page, list, end, flags);
+ if (PageSwapCache(head)) {
+ swp_entry_t entry = { .val = page_private(head) };
+
+ ret = split_swap_cluster(entry);
+ } else
+ ret = 0;
+ } else {
+ if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
+ pr_alert("total_mapcount: %u, page_count(): %u\n",
+ mapcount, count);
+ if (PageTail(page))
+ dump_page(head, NULL);
+ dump_page(page, "total_mapcount(head) > 0");
+ BUG();
+ }
+ spin_unlock(&pgdata->split_queue_lock);
+fail: if (mapping)
+ xa_unlock(&mapping->i_pages);
+ spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
+ remap_page(head);
+ ret = -EBUSY;
+ }
+
+out_unlock:
+ if (anon_vma) {
+ anon_vma_unlock_write(anon_vma);
+ put_anon_vma(anon_vma);
+ }
+ if (mapping)
+ i_mmap_unlock_read(mapping);
+out:
+ count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
+ return ret;
+}
+
+void free_transhuge_page(struct page *page)
+{
+ struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
+ unsigned long flags;
+
+ spin_lock_irqsave(&pgdata->split_queue_lock, flags);
+ if (!list_empty(page_deferred_list(page))) {
+ pgdata->split_queue_len--;
+ list_del(page_deferred_list(page));
+ }
+ spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
+ free_compound_page(page);
+}
+
+void deferred_split_huge_page(struct page *page)
+{
+ struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
+ unsigned long flags;
+
+ VM_BUG_ON_PAGE(!PageTransHuge(page), page);
+
+ spin_lock_irqsave(&pgdata->split_queue_lock, flags);
+ if (list_empty(page_deferred_list(page))) {
+ count_vm_event(THP_DEFERRED_SPLIT_PAGE);
+ list_add_tail(page_deferred_list(page), &pgdata->split_queue);
+ pgdata->split_queue_len++;
+ }
+ spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
+}
+
+static unsigned long deferred_split_count(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ struct pglist_data *pgdata = NODE_DATA(sc->nid);
+ return READ_ONCE(pgdata->split_queue_len);
+}
+
+static unsigned long deferred_split_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ struct pglist_data *pgdata = NODE_DATA(sc->nid);
+ unsigned long flags;
+ LIST_HEAD(list), *pos, *next;
+ struct page *page;
+ int split = 0;
+
+ spin_lock_irqsave(&pgdata->split_queue_lock, flags);
+ /* Take pin on all head pages to avoid freeing them under us */
+ list_for_each_safe(pos, next, &pgdata->split_queue) {
+ page = list_entry((void *)pos, struct page, mapping);
+ page = compound_head(page);
+ if (get_page_unless_zero(page)) {
+ list_move(page_deferred_list(page), &list);
+ } else {
+ /* We lost race with put_compound_page() */
+ list_del_init(page_deferred_list(page));
+ pgdata->split_queue_len--;
+ }
+ if (!--sc->nr_to_scan)
+ break;
+ }
+ spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
+
+ list_for_each_safe(pos, next, &list) {
+ page = list_entry((void *)pos, struct page, mapping);
+ if (!trylock_page(page))
+ goto next;
+ /* split_huge_page() removes page from list on success */
+ if (!split_huge_page(page))
+ split++;
+ unlock_page(page);
+next:
+ put_page(page);
+ }
+
+ spin_lock_irqsave(&pgdata->split_queue_lock, flags);
+ list_splice_tail(&list, &pgdata->split_queue);
+ spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
+
+ /*
+ * Stop shrinker if we didn't split any page, but the queue is empty.
+ * This can happen if pages were freed under us.
+ */
+ if (!split && list_empty(&pgdata->split_queue))
+ return SHRINK_STOP;
+ return split;
+}
+
+static struct shrinker deferred_split_shrinker = {
+ .count_objects = deferred_split_count,
+ .scan_objects = deferred_split_scan,
+ .seeks = DEFAULT_SEEKS,
+ .flags = SHRINKER_NUMA_AWARE,
+};
+
+#ifdef CONFIG_DEBUG_FS
+static int split_huge_pages_set(void *data, u64 val)
+{
+ struct zone *zone;
+ struct page *page;
+ unsigned long pfn, max_zone_pfn;
+ unsigned long total = 0, split = 0;
+
+ if (val != 1)
+ return -EINVAL;
+
+ for_each_populated_zone(zone) {
+ max_zone_pfn = zone_end_pfn(zone);
+ for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
+ if (!pfn_valid(pfn))
+ continue;
+
+ page = pfn_to_page(pfn);
+ if (!get_page_unless_zero(page))
+ continue;
+
+ if (zone != page_zone(page))
+ goto next;
+
+ if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
+ goto next;
+
+ total++;
+ lock_page(page);
+ if (!split_huge_page(page))
+ split++;
+ unlock_page(page);
+next:
+ put_page(page);
+ }
+ }
+
+ pr_info("%lu of %lu THP split\n", split, total);
+
+ return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
+ "%llu\n");
+
+static int __init split_huge_pages_debugfs(void)
+{
+ void *ret;
+
+ ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
+ &split_huge_pages_fops);
+ if (!ret)
+ pr_warn("Failed to create split_huge_pages in debugfs");
+ return 0;
+}
+late_initcall(split_huge_pages_debugfs);
+#endif
+
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
+ struct page *page)
+{
+ struct vm_area_struct *vma = pvmw->vma;
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long address = pvmw->address;
+ pmd_t pmdval;
+ swp_entry_t entry;
+ pmd_t pmdswp;
+
+ if (!(pvmw->pmd && !pvmw->pte))
+ return;
+
+ flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
+ pmdval = *pvmw->pmd;
+ pmdp_invalidate(vma, address, pvmw->pmd);
+ if (pmd_dirty(pmdval))
+ set_page_dirty(page);
+ entry = make_migration_entry(page, pmd_write(pmdval));
+ pmdswp = swp_entry_to_pmd(entry);
+ if (pmd_soft_dirty(pmdval))
+ pmdswp = pmd_swp_mksoft_dirty(pmdswp);
+ set_pmd_at(mm, address, pvmw->pmd, pmdswp);
+ page_remove_rmap(page, true);
+ put_page(page);
+}
+
+void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
+{
+ struct vm_area_struct *vma = pvmw->vma;
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long address = pvmw->address;
+ unsigned long mmun_start = address & HPAGE_PMD_MASK;
+ pmd_t pmde;
+ swp_entry_t entry;
+
+ if (!(pvmw->pmd && !pvmw->pte))
+ return;
+
+ entry = pmd_to_swp_entry(*pvmw->pmd);
+ get_page(new);
+ pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
+ if (pmd_swp_soft_dirty(*pvmw->pmd))
+ pmde = pmd_mksoft_dirty(pmde);
+ if (is_write_migration_entry(entry))
+ pmde = maybe_pmd_mkwrite(pmde, vma);
+
+ flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
+ if (PageAnon(new))
+ page_add_anon_rmap(new, vma, mmun_start, true);
+ else
+ page_add_file_rmap(new, true);
+ set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
+ if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
+ mlock_vma_page(new);
+ update_mmu_cache_pmd(vma, address, pvmw->pmd);
+}
+#endif