Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3302 insertions, 0 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
new file mode 100644
index 000000000..595779467
--- /dev/null
+++ b/mm/huge_memory.c
@@ -0,0 +1,3302 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Copyright (C) 2009  Red Hat, Inc.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/sched/mm.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/backing-dev.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 <linux/numa.h>
+#include <linux/page_owner.h>
+#include <linux/sched/sysctl.h>
+#include <linux/memory-tiers.h>
+
+#include <asm/tlb.h>
+#include <asm/pgalloc.h>
+#include "internal.h"
+#include "swap.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/thp.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;
+unsigned long huge_zero_pfn __read_mostly = ~0UL;
+
+bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
+			bool smaps, bool in_pf, bool enforce_sysfs)
+{
+	if (!vma->vm_mm)		/* vdso */
+		return false;
+
+	/*
+	 * Explicitly disabled through madvise or prctl, or some
+	 * architectures may disable THP for some mappings, for
+	 * example, s390 kvm.
+	 * */
+	if ((vm_flags & VM_NOHUGEPAGE) ||
+	    test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
+		return false;
+	/*
+	 * If the hardware/firmware marked hugepage support disabled.
+	 */
+	if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_NEVER_DAX))
+		return false;
+
+	/* khugepaged doesn't collapse DAX vma, but page fault is fine. */
+	if (vma_is_dax(vma))
+		return in_pf;
+
+	/*
+	 * Special VMA and hugetlb VMA.
+	 * Must be checked after dax since some dax mappings may have
+	 * VM_MIXEDMAP set.
+	 */
+	if (vm_flags & VM_NO_KHUGEPAGED)
+		return false;
+
+	/*
+	 * Check alignment for file vma and size for both file and anon vma.
+	 *
+	 * Skip the check for page fault. Huge fault does the check in fault
+	 * handlers. And this check is not suitable for huge PUD fault.
+	 */
+	if (!in_pf &&
+	    !transhuge_vma_suitable(vma, (vma->vm_end - HPAGE_PMD_SIZE)))
+		return false;
+
+	/*
+	 * Enabled via shmem mount options or sysfs settings.
+	 * Must be done before hugepage flags check since shmem has its
+	 * own flags.
+	 */
+	if (!in_pf && shmem_file(vma->vm_file))
+		return shmem_huge_enabled(vma, !enforce_sysfs);
+
+	/* Enforce sysfs THP requirements as necessary */
+	if (enforce_sysfs &&
+	    (!hugepage_flags_enabled() || (!(vm_flags & VM_HUGEPAGE) &&
+					   !hugepage_flags_always())))
+		return false;
+
+	/* Only regular file is valid */
+	if (!in_pf && file_thp_enabled(vma))
+		return true;
+
+	if (!vma_is_anonymous(vma))
+		return false;
+
+	if (vma_is_temporary_stack(vma))
+		return false;
+
+	/*
+	 * THPeligible bit of smaps should show 1 for proper VMAs even
+	 * though anon_vma is not initialized yet.
+	 *
+	 * Allow page fault since anon_vma may be not initialized until
+	 * the first page fault.
+	 */
+	if (!vma->anon_vma)
+		return (smaps || in_pf);
+
+	return true;
+}
+
+static bool get_huge_zero_page(void)
+{
+	struct page *zero_page;
+retry:
+	if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
+		return true;
+
+	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 false;
+	}
+	preempt_disable();
+	if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
+		preempt_enable();
+		__free_pages(zero_page, compound_order(zero_page));
+		goto retry;
+	}
+	WRITE_ONCE(huge_zero_pfn, page_to_pfn(zero_page));
+
+	/* We take additional reference here. It will be put back by shrinker */
+	atomic_set(&huge_zero_refcount, 2);
+	preempt_enable();
+	count_vm_event(THP_ZERO_PAGE_ALLOC);
+	return true;
+}
+
+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);
+		WRITE_ONCE(huge_zero_pfn, ~0UL);
+		__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)
+{
+	const char *output;
+
+	if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
+		output = "[always] madvise never";
+	else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
+			  &transparent_hugepage_flags))
+		output = "always [madvise] never";
+	else
+		output = "always madvise [never]";
+
+	return sysfs_emit(buf, "%s\n", output);
+}
+
+static ssize_t enabled_store(struct kobject *kobj,
+			     struct kobj_attribute *attr,
+			     const char *buf, size_t count)
+{
+	ssize_t ret = count;
+
+	if (sysfs_streq(buf, "always")) {
+		clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
+		set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
+	} else if (sysfs_streq(buf, "madvise")) {
+		clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
+		set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
+	} else if (sysfs_streq(buf, "never")) {
+		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_RW(enabled);
+
+ssize_t single_hugepage_flag_show(struct kobject *kobj,
+				  struct kobj_attribute *attr, char *buf,
+				  enum transparent_hugepage_flag flag)
+{
+	return sysfs_emit(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)
+{
+	const char *output;
+
+	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
+		     &transparent_hugepage_flags))
+		output = "[always] defer defer+madvise madvise never";
+	else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
+			  &transparent_hugepage_flags))
+		output = "always [defer] defer+madvise madvise never";
+	else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
+			  &transparent_hugepage_flags))
+		output = "always defer [defer+madvise] madvise never";
+	else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
+			  &transparent_hugepage_flags))
+		output = "always defer defer+madvise [madvise] never";
+	else
+		output = "always defer defer+madvise madvise [never]";
+
+	return sysfs_emit(buf, "%s\n", output);
+}
+
+static ssize_t defrag_store(struct kobject *kobj,
+			    struct kobj_attribute *attr,
+			    const char *buf, size_t count)
+{
+	if (sysfs_streq(buf, "always")) {
+		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 (sysfs_streq(buf, "defer+madvise")) {
+		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 (sysfs_streq(buf, "defer")) {
+		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 (sysfs_streq(buf, "madvise")) {
+		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 (sysfs_streq(buf, "never")) {
+		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_RW(defrag);
+
+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_RW(use_zero_page);
+
+static ssize_t hpage_pmd_size_show(struct kobject *kobj,
+				   struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%lu\n", HPAGE_PMD_SIZE);
+}
+static struct kobj_attribute hpage_pmd_size_attr =
+	__ATTR_RO(hpage_pmd_size);
+
+static struct attribute *hugepage_attr[] = {
+	&enabled_attr.attr,
+	&defrag_attr.attr,
+	&use_zero_page_attr.attr,
+	&hpage_pmd_size_attr.attr,
+#ifdef CONFIG_SHMEM
+	&shmem_enabled_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()) {
+		/*
+		 * Hardware doesn't support hugepages, hence disable
+		 * DAX PMD support.
+		 */
+		transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_NEVER_DAX;
+		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, "thp-zero");
+	if (err)
+		goto err_hzp_shrinker;
+	err = register_shrinker(&deferred_split_shrinker, "thp-deferred_split");
+	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;
+}
+
+#ifdef CONFIG_MEMCG
+static inline struct deferred_split *get_deferred_split_queue(struct page *page)
+{
+	struct mem_cgroup *memcg = page_memcg(compound_head(page));
+	struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
+
+	if (memcg)
+		return &memcg->deferred_split_queue;
+	else
+		return &pgdat->deferred_split_queue;
+}
+#else
+static inline struct deferred_split *get_deferred_split_queue(struct page *page)
+{
+	struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
+
+	return &pgdat->deferred_split_queue;
+}
+#endif
+
+void prep_transhuge_page(struct page *page)
+{
+	/*
+	 * we use page->mapping and page->index 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);
+}
+
+static inline bool is_transparent_hugepage(struct page *page)
+{
+	if (!PageCompound(page))
+		return false;
+
+	page = compound_head(page);
+	return is_huge_zero_page(page) ||
+	       page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
+}
+
+static unsigned long __thp_get_unmapped_area(struct file *filp,
+		unsigned long addr, unsigned long len,
+		loff_t off, unsigned long flags, unsigned long size)
+{
+	loff_t off_end = off + len;
+	loff_t off_align = round_up(off, size);
+	unsigned long len_pad, ret;
+
+	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;
+
+	ret = current->mm->get_unmapped_area(filp, addr, len_pad,
+					      off >> PAGE_SHIFT, flags);
+
+	/*
+	 * The failure might be due to length padding. The caller will retry
+	 * without the padding.
+	 */
+	if (IS_ERR_VALUE(ret))
+		return 0;
+
+	/*
+	 * Do not try to align to THP boundary if allocation at the address
+	 * hint succeeds.
+	 */
+	if (ret == addr)
+		return addr;
+
+	ret += (off - ret) & (size - 1);
+	return ret;
+}
+
+unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
+		unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+	unsigned long ret;
+	loff_t off = (loff_t)pgoff << PAGE_SHIFT;
+
+	ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
+	if (ret)
+		return ret;
+
+	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;
+	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_charge(page_folio(page), vma->vm_mm, gfp)) {
+		put_page(page);
+		count_vm_event(THP_FAULT_FALLBACK);
+		count_vm_event(THP_FAULT_FALLBACK_CHARGE);
+		return VM_FAULT_FALLBACK;
+	}
+	cgroup_throttle_swaprate(page, gfp);
+
+	pgtable = pte_alloc_one(vma->vm_mm);
+	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)) {
+			spin_unlock(vmf->ptl);
+			put_page(page);
+			pte_free(vma->vm_mm, pgtable);
+			ret = handle_userfault(vmf, VM_UFFD_MISSING);
+			VM_BUG_ON(ret & VM_FAULT_FALLBACK);
+			return ret;
+		}
+
+		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);
+		lru_cache_add_inactive_or_unevictable(page, vma);
+		pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
+		set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
+		update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
+		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);
+		count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
+	}
+
+	return 0;
+unlock_release:
+	spin_unlock(vmf->ptl);
+release:
+	if (pgtable)
+		pte_free(vma->vm_mm, pgtable);
+	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
+ */
+gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
+{
+	const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
+
+	/* Always do synchronous compaction */
+	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
+		return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
+
+	/* Kick kcompactd and fail quickly */
+	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
+		return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
+
+	/* Synchronous compaction if madvised, otherwise kick kcompactd */
+	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);
+
+	/* Only do synchronous compaction if madvised */
+	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 void 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;
+	entry = mk_pmd(zero_page, vma->vm_page_prot);
+	entry = pmd_mkhuge(entry);
+	pgtable_trans_huge_deposit(mm, pmd, pgtable);
+	set_pmd_at(mm, haddr, pmd, entry);
+	mm_inc_nr_ptes(mm);
+}
+
+vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	gfp_t gfp;
+	struct folio *folio;
+	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
+
+	if (!transhuge_vma_suitable(vma, haddr))
+		return VM_FAULT_FALLBACK;
+	if (unlikely(anon_vma_prepare(vma)))
+		return VM_FAULT_OOM;
+	khugepaged_enter_vma(vma, vma->vm_flags);
+
+	if (!(vmf->flags & FAULT_FLAG_WRITE) &&
+			!mm_forbids_zeropage(vma->vm_mm) &&
+			transparent_hugepage_use_zero_page()) {
+		pgtable_t pgtable;
+		struct page *zero_page;
+		vm_fault_t ret;
+		pgtable = pte_alloc_one(vma->vm_mm);
+		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;
+		if (pmd_none(*vmf->pmd)) {
+			ret = check_stable_address_space(vma->vm_mm);
+			if (ret) {
+				spin_unlock(vmf->ptl);
+				pte_free(vma->vm_mm, pgtable);
+			} else if (userfaultfd_missing(vma)) {
+				spin_unlock(vmf->ptl);
+				pte_free(vma->vm_mm, pgtable);
+				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);
+				update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
+				spin_unlock(vmf->ptl);
+			}
+		} else {
+			spin_unlock(vmf->ptl);
+			pte_free(vma->vm_mm, pgtable);
+		}
+		return ret;
+	}
+	gfp = vma_thp_gfp_mask(vma);
+	folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, vma, haddr, true);
+	if (unlikely(!folio)) {
+		count_vm_event(THP_FAULT_FALLBACK);
+		return VM_FAULT_FALLBACK;
+	}
+	return __do_huge_pmd_anonymous_page(vmf, &folio->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);
+	if (!pmd_none(*pmd)) {
+		if (write) {
+			if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
+				WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
+				goto out_unlock;
+			}
+			entry = pmd_mkyoung(*pmd);
+			entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
+			if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
+				update_mmu_cache_pmd(vma, addr, pmd);
+		}
+
+		goto out_unlock;
+	}
+
+	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);
+		pgtable = NULL;
+	}
+
+	set_pmd_at(mm, addr, pmd, entry);
+	update_mmu_cache_pmd(vma, addr, pmd);
+
+out_unlock:
+	spin_unlock(ptl);
+	if (pgtable)
+		pte_free(mm, pgtable);
+}
+
+/**
+ * vmf_insert_pfn_pmd_prot - insert a pmd size pfn
+ * @vmf: Structure describing the fault
+ * @pfn: pfn to insert
+ * @pgprot: page protection to use
+ * @write: whether it's a write fault
+ *
+ * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and
+ * also consult the vmf_insert_mixed_prot() documentation when
+ * @pgprot != @vmf->vma->vm_page_prot.
+ *
+ * Return: vm_fault_t value.
+ */
+vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn,
+				   pgprot_t pgprot, bool write)
+{
+	unsigned long addr = vmf->address & PMD_MASK;
+	struct vm_area_struct *vma = vmf->vma;
+	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);
+		if (!pgtable)
+			return VM_FAULT_OOM;
+	}
+
+	track_pfn_insert(vma, &pgprot, pfn);
+
+	insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
+	return VM_FAULT_NOPAGE;
+}
+EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot);
+
+#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);
+	if (!pud_none(*pud)) {
+		if (write) {
+			if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
+				WARN_ON_ONCE(!is_huge_zero_pud(*pud));
+				goto out_unlock;
+			}
+			entry = pud_mkyoung(*pud);
+			entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
+			if (pudp_set_access_flags(vma, addr, pud, entry, 1))
+				update_mmu_cache_pud(vma, addr, pud);
+		}
+		goto out_unlock;
+	}
+
+	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);
+
+out_unlock:
+	spin_unlock(ptl);
+}
+
+/**
+ * vmf_insert_pfn_pud_prot - insert a pud size pfn
+ * @vmf: Structure describing the fault
+ * @pfn: pfn to insert
+ * @pgprot: page protection to use
+ * @write: whether it's a write fault
+ *
+ * Insert a pud size pfn. See vmf_insert_pfn() for additional info and
+ * also consult the vmf_insert_mixed_prot() documentation when
+ * @pgprot != @vmf->vma->vm_page_prot.
+ *
+ * Return: vm_fault_t value.
+ */
+vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn,
+				   pgprot_t pgprot, bool write)
+{
+	unsigned long addr = vmf->address & PUD_MASK;
+	struct vm_area_struct *vma = vmf->vma;
+
+	/*
+	 * 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, vmf->pud, pfn, pgprot, write);
+	return VM_FAULT_NOPAGE;
+}
+EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot);
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+
+static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
+		      pmd_t *pmd, bool write)
+{
+	pmd_t _pmd;
+
+	_pmd = pmd_mkyoung(*pmd);
+	if (write)
+		_pmd = pmd_mkdirty(_pmd);
+	if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
+				  pmd, _pmd, 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, struct dev_pagemap **pgmap)
+{
+	unsigned long pfn = pmd_pfn(*pmd);
+	struct mm_struct *mm = vma->vm_mm;
+	struct page *page;
+
+	assert_spin_locked(pmd_lockptr(mm, pmd));
+
+	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
+	if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
+			 (FOLL_PIN | FOLL_GET)))
+		return NULL;
+
+	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 & FOLL_WRITE);
+
+	/*
+	 * device mapped pages can only be returned if the
+	 * caller will manage the page reference count.
+	 */
+	if (!(flags & (FOLL_GET | FOLL_PIN)))
+		return ERR_PTR(-EEXIST);
+
+	pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
+	*pgmap = get_dev_pagemap(pfn, *pgmap);
+	if (!*pgmap)
+		return ERR_PTR(-EFAULT);
+	page = pfn_to_page(pfn);
+	if (!try_grab_page(page, flags))
+		page = ERR_PTR(-ENOMEM);
+
+	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 *dst_vma, struct vm_area_struct *src_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(dst_vma))
+		return 0;
+
+	pgtable = pte_alloc_one(dst_mm);
+	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_readable_migration_entry(entry)) {
+			entry = make_readable_migration_entry(
+							swp_offset(entry));
+			pmd = swp_entry_to_pmd(entry);
+			if (pmd_swp_soft_dirty(*src_pmd))
+				pmd = pmd_swp_mksoft_dirty(pmd);
+			if (pmd_swp_uffd_wp(*src_pmd))
+				pmd = pmd_swp_mkuffd_wp(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);
+		if (!userfaultfd_wp(dst_vma))
+			pmd = pmd_swp_clear_uffd_wp(pmd);
+		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)) {
+		/*
+		 * 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.
+		 */
+		mm_get_huge_zero_page(dst_mm);
+		goto out_zero_page;
+	}
+
+	src_page = pmd_page(pmd);
+	VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
+
+	get_page(src_page);
+	if (unlikely(page_try_dup_anon_rmap(src_page, true, src_vma))) {
+		/* Page maybe pinned: split and retry the fault on PTEs. */
+		put_page(src_page);
+		pte_free(dst_mm, pgtable);
+		spin_unlock(src_ptl);
+		spin_unlock(dst_ptl);
+		__split_huge_pmd(src_vma, src_pmd, addr, false, NULL);
+		return -EAGAIN;
+	}
+	add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
+out_zero_page:
+	mm_inc_nr_ptes(dst_mm);
+	pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
+	pmdp_set_wrprotect(src_mm, addr, src_pmd);
+	if (!userfaultfd_wp(dst_vma))
+		pmd = pmd_clear_uffd_wp(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, bool write)
+{
+	pud_t _pud;
+
+	_pud = pud_mkyoung(*pud);
+	if (write)
+		_pud = pud_mkdirty(_pud);
+	if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
+				  pud, _pud, 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, struct dev_pagemap **pgmap)
+{
+	unsigned long pfn = pud_pfn(*pud);
+	struct mm_struct *mm = vma->vm_mm;
+	struct page *page;
+
+	assert_spin_locked(pud_lockptr(mm, pud));
+
+	if (flags & FOLL_WRITE && !pud_write(*pud))
+		return NULL;
+
+	/* FOLL_GET and FOLL_PIN are mutually exclusive. */
+	if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
+			 (FOLL_PIN | FOLL_GET)))
+		return NULL;
+
+	if (pud_present(*pud) && pud_devmap(*pud))
+		/* pass */;
+	else
+		return NULL;
+
+	if (flags & FOLL_TOUCH)
+		touch_pud(vma, addr, pud, flags & FOLL_WRITE);
+
+	/*
+	 * device mapped pages can only be returned if the
+	 * caller will manage the page reference count.
+	 *
+	 * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here:
+	 */
+	if (!(flags & (FOLL_GET | FOLL_PIN)))
+		return ERR_PTR(-EEXIST);
+
+	pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
+	*pgmap = get_dev_pagemap(pfn, *pgmap);
+	if (!*pgmap)
+		return ERR_PTR(-EFAULT);
+	page = pfn_to_page(pfn);
+	if (!try_grab_page(page, flags))
+		page = ERR_PTR(-ENOMEM);
+
+	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 */
+	}
+
+	/*
+	 * TODO: once we support anonymous pages, use page_try_dup_anon_rmap()
+	 * and split if duplicating fails.
+	 */
+	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)
+{
+	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;
+
+	touch_pud(vmf->vma, vmf->address, vmf->pud, write);
+unlock:
+	spin_unlock(vmf->ptl);
+}
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+
+void huge_pmd_set_accessed(struct vm_fault *vmf)
+{
+	bool write = vmf->flags & FAULT_FLAG_WRITE;
+
+	vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
+	if (unlikely(!pmd_same(*vmf->pmd, vmf->orig_pmd)))
+		goto unlock;
+
+	touch_pmd(vmf->vma, vmf->address, vmf->pmd, write);
+
+unlock:
+	spin_unlock(vmf->ptl);
+}
+
+vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
+{
+	const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
+	struct vm_area_struct *vma = vmf->vma;
+	struct folio *folio;
+	struct page *page;
+	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
+	pmd_t orig_pmd = vmf->orig_pmd;
+
+	vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
+	VM_BUG_ON_VMA(!vma->anon_vma, vma);
+
+	VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE));
+	VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE));
+
+	if (is_huge_zero_pmd(orig_pmd))
+		goto fallback;
+
+	spin_lock(vmf->ptl);
+
+	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
+		spin_unlock(vmf->ptl);
+		return 0;
+	}
+
+	page = pmd_page(orig_pmd);
+	folio = page_folio(page);
+	VM_BUG_ON_PAGE(!PageHead(page), page);
+
+	/* Early check when only holding the PT lock. */
+	if (PageAnonExclusive(page))
+		goto reuse;
+
+	if (!folio_trylock(folio)) {
+		folio_get(folio);
+		spin_unlock(vmf->ptl);
+		folio_lock(folio);
+		spin_lock(vmf->ptl);
+		if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
+			spin_unlock(vmf->ptl);
+			folio_unlock(folio);
+			folio_put(folio);
+			return 0;
+		}
+		folio_put(folio);
+	}
+
+	/* Recheck after temporarily dropping the PT lock. */
+	if (PageAnonExclusive(page)) {
+		folio_unlock(folio);
+		goto reuse;
+	}
+
+	/*
+	 * See do_wp_page(): we can only reuse the folio exclusively if
+	 * there are no additional references. Note that we always drain
+	 * the LRU pagevecs immediately after adding a THP.
+	 */
+	if (folio_ref_count(folio) >
+			1 + folio_test_swapcache(folio) * folio_nr_pages(folio))
+		goto unlock_fallback;
+	if (folio_test_swapcache(folio))
+		folio_free_swap(folio);
+	if (folio_ref_count(folio) == 1) {
+		pmd_t entry;
+
+		page_move_anon_rmap(page, vma);
+		folio_unlock(folio);
+reuse:
+		if (unlikely(unshare)) {
+			spin_unlock(vmf->ptl);
+			return 0;
+		}
+		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);
+		spin_unlock(vmf->ptl);
+		return VM_FAULT_WRITE;
+	}
+
+unlock_fallback:
+	folio_unlock(folio);
+	spin_unlock(vmf->ptl);
+fallback:
+	__split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL);
+	return VM_FAULT_FALLBACK;
+}
+
+/* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */
+static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
+					struct vm_area_struct *vma,
+					unsigned int flags)
+{
+	/* If the pmd is writable, we can write to the page. */
+	if (pmd_write(pmd))
+		return true;
+
+	/* Maybe FOLL_FORCE is set to override it? */
+	if (!(flags & FOLL_FORCE))
+		return false;
+
+	/* But FOLL_FORCE has no effect on shared mappings */
+	if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
+		return false;
+
+	/* ... or read-only private ones */
+	if (!(vma->vm_flags & VM_MAYWRITE))
+		return false;
+
+	/* ... or already writable ones that just need to take a write fault */
+	if (vma->vm_flags & VM_WRITE)
+		return false;
+
+	/*
+	 * See can_change_pte_writable(): we broke COW and could map the page
+	 * writable if we have an exclusive anonymous page ...
+	 */
+	if (!page || !PageAnon(page) || !PageAnonExclusive(page))
+		return false;
+
+	/* ... and a write-fault isn't required for other reasons. */
+	if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
+		return false;
+	return !userfaultfd_huge_pmd_wp(vma, 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;
+
+	assert_spin_locked(pmd_lockptr(mm, pmd));
+
+	page = pmd_page(*pmd);
+	VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
+
+	if ((flags & FOLL_WRITE) &&
+	    !can_follow_write_pmd(*pmd, page, vma, flags))
+		return NULL;
+
+	/* 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 (pmd_protnone(*pmd) && !gup_can_follow_protnone(flags))
+		return NULL;
+
+	if (!pmd_write(*pmd) && gup_must_unshare(flags, page))
+		return ERR_PTR(-EMLINK);
+
+	VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
+			!PageAnonExclusive(page), page);
+
+	if (!try_grab_page(page, flags))
+		return ERR_PTR(-ENOMEM);
+
+	if (flags & FOLL_TOUCH)
+		touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
+
+	page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
+	VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
+
+	return page;
+}
+
+/* NUMA hinting page fault entry point for trans huge pmds */
+vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	pmd_t oldpmd = vmf->orig_pmd;
+	pmd_t pmd;
+	struct page *page;
+	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
+	int page_nid = NUMA_NO_NODE;
+	int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK);
+	bool migrated = false;
+	bool was_writable = pmd_savedwrite(oldpmd);
+	int flags = 0;
+
+	vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
+	if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
+		spin_unlock(vmf->ptl);
+		goto out;
+	}
+
+	pmd = pmd_modify(oldpmd, vma->vm_page_prot);
+	page = vm_normal_page_pmd(vma, haddr, pmd);
+	if (!page)
+		goto out_map;
+
+	/* See similar comment in do_numa_page for explanation */
+	if (!was_writable)
+		flags |= TNF_NO_GROUP;
+
+	page_nid = page_to_nid(page);
+	/*
+	 * For memory tiering mode, cpupid of slow memory page is used
+	 * to record page access time.  So use default value.
+	 */
+	if (node_is_toptier(page_nid))
+		last_cpupid = page_cpupid_last(page);
+	target_nid = numa_migrate_prep(page, vma, haddr, page_nid,
+				       &flags);
+
+	if (target_nid == NUMA_NO_NODE) {
+		put_page(page);
+		goto out_map;
+	}
+
+	spin_unlock(vmf->ptl);
+
+	migrated = migrate_misplaced_page(page, vma, target_nid);
+	if (migrated) {
+		flags |= TNF_MIGRATED;
+		page_nid = target_nid;
+	} else {
+		flags |= TNF_MIGRATE_FAIL;
+		vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
+		if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
+			spin_unlock(vmf->ptl);
+			goto out;
+		}
+		goto out_map;
+	}
+
+out:
+	if (page_nid != NUMA_NO_NODE)
+		task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
+				flags);
+
+	return 0;
+
+out_map:
+	/* Restore the PMD */
+	pmd = pmd_modify(oldpmd, 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);
+	spin_unlock(vmf->ptl);
+	goto out;
+}
+
+/*
+ * 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_change_page_size(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 (total_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_change_page_size(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(vma, addr, pmd,
+						tlb->fullmm);
+	tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+	if (vma_is_special_huge(vma)) {
+		if (arch_needs_pgtable_deposit())
+			zap_deposited_table(tlb->mm, pmd);
+		spin_unlock(ptl);
+	} else if (is_huge_zero_pmd(orig_pmd)) {
+		zap_deposited_table(tlb->mm, pmd);
+		spin_unlock(ptl);
+	} else {
+		struct page *page = NULL;
+		int flush_needed = 1;
+
+		if (pmd_present(orig_pmd)) {
+			page = pmd_page(orig_pmd);
+			page_remove_rmap(page, vma, 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_swap_entry_to_page(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, 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;
+
+	/*
+	 * 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_lock 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_pmd_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 unchanged and TLB flush unnecessary
+ *      or if prot_numa but THP migration is not supported
+ *  - HPAGE_PMD_NR if protections changed and TLB flush necessary
+ */
+int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
+		    pmd_t *pmd, unsigned long addr, pgprot_t newprot,
+		    unsigned long cp_flags)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	spinlock_t *ptl;
+	pmd_t oldpmd, entry;
+	bool preserve_write;
+	int ret;
+	bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
+	bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
+	bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
+
+	tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
+
+	if (prot_numa && !thp_migration_supported())
+		return 1;
+
+	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);
+		struct page *page = pfn_swap_entry_to_page(entry);
+		pmd_t newpmd;
+
+		VM_BUG_ON(!is_pmd_migration_entry(*pmd));
+		if (is_writable_migration_entry(entry)) {
+			/*
+			 * A protection check is difficult so
+			 * just be safe and disable write
+			 */
+			if (PageAnon(page))
+				entry = make_readable_exclusive_migration_entry(swp_offset(entry));
+			else
+				entry = make_readable_migration_entry(swp_offset(entry));
+			newpmd = swp_entry_to_pmd(entry);
+			if (pmd_swp_soft_dirty(*pmd))
+				newpmd = pmd_swp_mksoft_dirty(newpmd);
+			if (pmd_swp_uffd_wp(*pmd))
+				newpmd = pmd_swp_mkuffd_wp(newpmd);
+		} else {
+			newpmd = *pmd;
+		}
+
+		if (uffd_wp)
+			newpmd = pmd_swp_mkuffd_wp(newpmd);
+		else if (uffd_wp_resolve)
+			newpmd = pmd_swp_clear_uffd_wp(newpmd);
+		if (!pmd_same(*pmd, newpmd))
+			set_pmd_at(mm, addr, pmd, newpmd);
+		goto unlock;
+	}
+#endif
+
+	if (prot_numa) {
+		struct page *page;
+		bool toptier;
+		/*
+		 * 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 (is_huge_zero_pmd(*pmd))
+			goto unlock;
+
+		if (pmd_protnone(*pmd))
+			goto unlock;
+
+		page = pmd_page(*pmd);
+		toptier = node_is_toptier(page_to_nid(page));
+		/*
+		 * Skip scanning top tier node if normal numa
+		 * balancing is disabled
+		 */
+		if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
+		    toptier)
+			goto unlock;
+
+		if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
+		    !toptier)
+			xchg_page_access_time(page, jiffies_to_msecs(jiffies));
+	}
+	/*
+	 * In case prot_numa, we are under mmap_read_lock(mm). It's critical
+	 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
+	 * which is also under mmap_read_lock(mm):
+	 *
+	 *	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_ad() is required to make sure we don't miss
+	 * dirty/young flags set by hardware.
+	 */
+	oldpmd = pmdp_invalidate_ad(vma, addr, pmd);
+
+	entry = pmd_modify(oldpmd, newprot);
+	if (preserve_write)
+		entry = pmd_mk_savedwrite(entry);
+	if (uffd_wp) {
+		entry = pmd_wrprotect(entry);
+		entry = pmd_mkuffd_wp(entry);
+	} else if (uffd_wp_resolve) {
+		/*
+		 * Leave the write bit to be handled by PF interrupt
+		 * handler, then things like COW could be properly
+		 * handled.
+		 */
+		entry = pmd_clear_uffd_wp(entry);
+	}
+	ret = HPAGE_PMD_NR;
+	set_pmd_at(mm, addr, pmd, entry);
+
+	if (huge_pmd_needs_flush(oldpmd, entry))
+		tlb_flush_pmd_range(tlb, addr, HPAGE_PMD_SIZE);
+
+	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 page table lock pointer if a given pud 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 *__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)
+{
+	spinlock_t *ptl;
+
+	ptl = __pud_trans_huge_lock(pud, vma);
+	if (!ptl)
+		return 0;
+
+	pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
+	tlb_remove_pud_tlb_entry(tlb, pud, addr);
+	if (vma_is_special_huge(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 mmu_notifier_range range;
+
+	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
+				address & HPAGE_PUD_MASK,
+				(address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
+	mmu_notifier_invalidate_range_start(&range);
+	ptl = pud_lock(vma->vm_mm, pud);
+	if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
+		goto out;
+	__split_huge_pud_locked(vma, pud, range.start);
+
+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(&range);
+}
+#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, old_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/mm/mmu_notifier.rst
+	 */
+	old_pmd = 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);
+		if (pmd_uffd_wp(old_pmd))
+			entry = pte_mkuffd_wp(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, uffd_wp = false;
+	bool anon_exclusive = false, dirty = 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)) {
+		old_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_special_huge(vma))
+			return;
+		if (unlikely(is_pmd_migration_entry(old_pmd))) {
+			swp_entry_t entry;
+
+			entry = pmd_to_swp_entry(old_pmd);
+			page = pfn_swap_entry_to_page(entry);
+		} else {
+			page = pmd_page(old_pmd);
+			if (!PageDirty(page) && pmd_dirty(old_pmd))
+				set_page_dirty(page);
+			if (!PageReferenced(page) && pmd_young(old_pmd))
+				SetPageReferenced(page);
+			page_remove_rmap(page, vma, true);
+			put_page(page);
+		}
+		add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
+		return;
+	}
+
+	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/TechDocs/41322_10h_Rev_Gd.pdf, Erratum
+	 * 383 on page 105. 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_swap_entry_to_page(entry);
+		write = is_writable_migration_entry(entry);
+		if (PageAnon(page))
+			anon_exclusive = is_readable_exclusive_migration_entry(entry);
+		young = is_migration_entry_young(entry);
+		dirty = is_migration_entry_dirty(entry);
+		soft_dirty = pmd_swp_soft_dirty(old_pmd);
+		uffd_wp = pmd_swp_uffd_wp(old_pmd);
+	} else {
+		page = pmd_page(old_pmd);
+		if (pmd_dirty(old_pmd)) {
+			dirty = true;
+			SetPageDirty(page);
+		}
+		write = pmd_write(old_pmd);
+		young = pmd_young(old_pmd);
+		soft_dirty = pmd_soft_dirty(old_pmd);
+		uffd_wp = pmd_uffd_wp(old_pmd);
+
+		VM_BUG_ON_PAGE(!page_count(page), page);
+		page_ref_add(page, HPAGE_PMD_NR - 1);
+
+		/*
+		 * Without "freeze", we'll simply split the PMD, propagating the
+		 * PageAnonExclusive() flag for each PTE by setting it for
+		 * each subpage -- no need to (temporarily) clear.
+		 *
+		 * With "freeze" we want to replace mapped pages by
+		 * migration entries right away. This is only possible if we
+		 * managed to clear PageAnonExclusive() -- see
+		 * set_pmd_migration_entry().
+		 *
+		 * In case we cannot clear PageAnonExclusive(), split the PMD
+		 * only and let try_to_migrate_one() fail later.
+		 *
+		 * See page_try_share_anon_rmap(): invalidate PMD first.
+		 */
+		anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
+		if (freeze && anon_exclusive && page_try_share_anon_rmap(page))
+			freeze = false;
+	}
+
+	/*
+	 * 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;
+			if (write)
+				swp_entry = make_writable_migration_entry(
+							page_to_pfn(page + i));
+			else if (anon_exclusive)
+				swp_entry = make_readable_exclusive_migration_entry(
+							page_to_pfn(page + i));
+			else
+				swp_entry = make_readable_migration_entry(
+							page_to_pfn(page + i));
+			if (young)
+				swp_entry = make_migration_entry_young(swp_entry);
+			if (dirty)
+				swp_entry = make_migration_entry_dirty(swp_entry);
+			entry = swp_entry_to_pte(swp_entry);
+			if (soft_dirty)
+				entry = pte_swp_mksoft_dirty(entry);
+			if (uffd_wp)
+				entry = pte_swp_mkuffd_wp(entry);
+		} else {
+			entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
+			entry = maybe_mkwrite(entry, vma);
+			if (anon_exclusive)
+				SetPageAnonExclusive(page + i);
+			if (!write)
+				entry = pte_wrprotect(entry);
+			if (!young)
+				entry = pte_mkold(entry);
+			/*
+			 * NOTE: we don't do pte_mkdirty when dirty==true
+			 * because it breaks sparc64 which can sigsegv
+			 * random process.  Need to revisit when we figure
+			 * out what is special with sparc64.
+			 */
+			if (soft_dirty)
+				entry = pte_mksoft_dirty(entry);
+			if (uffd_wp)
+				entry = pte_mkuffd_wp(entry);
+		}
+		pte = pte_offset_map(&_pmd, addr);
+		BUG_ON(!pte_none(*pte));
+		set_pte_at(mm, addr, pte, entry);
+		if (!pmd_migration)
+			atomic_inc(&page[i]._mapcount);
+		pte_unmap(pte);
+	}
+
+	if (!pmd_migration) {
+		/*
+		 * 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);
+		}
+
+		lock_page_memcg(page);
+		if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
+			/* Last compound_mapcount is gone. */
+			__mod_lruvec_page_state(page, NR_ANON_THPS,
+						-HPAGE_PMD_NR);
+			if (TestClearPageDoubleMap(page)) {
+				/* No need in mapcount reference anymore */
+				for (i = 0; i < HPAGE_PMD_NR; i++)
+					atomic_dec(&page[i]._mapcount);
+			}
+		}
+		unlock_page_memcg(page);
+
+		/* Above is effectively page_remove_rmap(page, vma, true) */
+		munlock_vma_page(page, vma, true);
+	}
+
+	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, vma, false);
+			put_page(page + i);
+		}
+	}
+}
+
+void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+		unsigned long address, bool freeze, struct folio *folio)
+{
+	spinlock_t *ptl;
+	struct mmu_notifier_range range;
+
+	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
+				address & HPAGE_PMD_MASK,
+				(address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
+	mmu_notifier_invalidate_range_start(&range);
+	ptl = pmd_lock(vma->vm_mm, pmd);
+
+	/*
+	 * If caller asks to setup a migration entry, we need a folio to check
+	 * pmd against. Otherwise we can end up replacing wrong folio.
+	 */
+	VM_BUG_ON(freeze && !folio);
+	VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
+
+	if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
+	    is_pmd_migration_entry(*pmd)) {
+		/*
+		 * It's safe to call pmd_page when folio is set because it's
+		 * guaranteed that pmd is present.
+		 */
+		if (folio && folio != page_folio(pmd_page(*pmd)))
+			goto out;
+		__split_huge_pmd_locked(vma, pmd, range.start, 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(&range);
+}
+
+void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
+		bool freeze, struct folio *folio)
+{
+	pmd_t *pmd = mm_find_pmd(vma->vm_mm, address);
+
+	if (!pmd)
+		return;
+
+	__split_huge_pmd(vma, pmd, address, freeze, folio);
+}
+
+static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address)
+{
+	/*
+	 * If the new address isn't hpage aligned and it could previously
+	 * contain an hugepage: check if we need to split an huge pmd.
+	 */
+	if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) &&
+	    range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE),
+			 ALIGN(address, HPAGE_PMD_SIZE)))
+		split_huge_pmd_address(vma, address, false, NULL);
+}
+
+void vma_adjust_trans_huge(struct vm_area_struct *vma,
+			     unsigned long start,
+			     unsigned long end,
+			     long adjust_next)
+{
+	/* Check if we need to split start first. */
+	split_huge_pmd_if_needed(vma, start);
+
+	/* Check if we need to split end next. */
+	split_huge_pmd_if_needed(vma, end);
+
+	/*
+	 * If we're also updating the next vma vm_start,
+	 * check if we need to split it.
+	 */
+	if (adjust_next > 0) {
+		struct vm_area_struct *next = find_vma(vma->vm_mm, vma->vm_end);
+		unsigned long nstart = next->vm_start;
+		nstart += adjust_next;
+		split_huge_pmd_if_needed(next, nstart);
+	}
+}
+
+static void unmap_folio(struct folio *folio)
+{
+	enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
+		TTU_SYNC;
+
+	VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
+
+	/*
+	 * Anon pages need migration entries to preserve them, but file
+	 * pages can simply be left unmapped, then faulted back on demand.
+	 * If that is ever changed (perhaps for mlock), update remap_page().
+	 */
+	if (folio_test_anon(folio))
+		try_to_migrate(folio, ttu_flags);
+	else
+		try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK);
+}
+
+static void remap_page(struct folio *folio, unsigned long nr)
+{
+	int i = 0;
+
+	/* If unmap_folio() uses try_to_migrate() on file, remove this check */
+	if (!folio_test_anon(folio))
+		return;
+	for (;;) {
+		remove_migration_ptes(folio, folio, true);
+		i += folio_nr_pages(folio);
+		if (i >= nr)
+			break;
+		folio = folio_next(folio);
+	}
+}
+
+static void lru_add_page_tail(struct page *head, struct page *tail,
+		struct lruvec *lruvec, struct list_head *list)
+{
+	VM_BUG_ON_PAGE(!PageHead(head), head);
+	VM_BUG_ON_PAGE(PageCompound(tail), head);
+	VM_BUG_ON_PAGE(PageLRU(tail), head);
+	lockdep_assert_held(&lruvec->lru_lock);
+
+	if (list) {
+		/* page reclaim is reclaiming a huge page */
+		VM_WARN_ON(PageLRU(head));
+		get_page(tail);
+		list_add_tail(&tail->lru, list);
+	} else {
+		/* head is still on lru (and we have it frozen) */
+		VM_WARN_ON(!PageLRU(head));
+		if (PageUnevictable(tail))
+			tail->mlock_count = 0;
+		else
+			list_add_tail(&tail->lru, &head->lru);
+		SetPageLRU(tail);
+	}
+}
+
+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 example lock_page() which set PG_waiters.
+	 *
+	 * Note that for mapped sub-pages of an anonymous THP,
+	 * PG_anon_exclusive has been cleared in unmap_folio() and is stored in
+	 * the migration entry instead from where remap_page() will restore it.
+	 * We can still have PG_anon_exclusive set on effectively unmapped and
+	 * unreferenced sub-pages of an anonymous THP: we can simply drop
+	 * PG_anon_exclusive (-> PG_mappedtodisk) for these here.
+	 */
+	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_workingset) |
+			 (1L << PG_locked) |
+			 (1L << PG_unevictable) |
+#ifdef CONFIG_64BIT
+			 (1L << PG_arch_2) |
+#endif
+			 (1L << PG_dirty) |
+			 LRU_GEN_MASK | LRU_REFS_MASK));
+
+	/* ->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->private should not be set in tail pages with the exception
+	 * of swap cache pages that store the swp_entry_t in tail pages.
+	 * Fix up and warn once if private is unexpectedly set.
+	 */
+	if (!folio_test_swapcache(page_folio(head))) {
+		VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, page_tail);
+		page_tail->private = 0;
+	}
+
+	/* 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)
+{
+	struct folio *folio = page_folio(page);
+	struct page *head = &folio->page;
+	struct lruvec *lruvec;
+	struct address_space *swap_cache = NULL;
+	unsigned long offset = 0;
+	unsigned int nr = thp_nr_pages(head);
+	int i;
+
+	/* complete memcg works before add pages to LRU */
+	split_page_memcg(head, nr);
+
+	if (PageAnon(head) && PageSwapCache(head)) {
+		swp_entry_t entry = { .val = page_private(head) };
+
+		offset = swp_offset(entry);
+		swap_cache = swap_address_space(entry);
+		xa_lock(&swap_cache->i_pages);
+	}
+
+	/* lock lru list/PageCompound, ref frozen by page_ref_freeze */
+	lruvec = folio_lruvec_lock(folio);
+
+	ClearPageHasHWPoisoned(head);
+
+	for (i = nr - 1; i >= 1; i--) {
+		__split_huge_page_tail(head, i, lruvec, list);
+		/* Some pages can be beyond EOF: drop them from page cache */
+		if (head[i].index >= end) {
+			struct folio *tail = page_folio(head + i);
+
+			if (shmem_mapping(head->mapping))
+				shmem_uncharge(head->mapping->host, 1);
+			else if (folio_test_clear_dirty(tail))
+				folio_account_cleaned(tail,
+					inode_to_wb(folio->mapping->host));
+			__filemap_remove_folio(tail, NULL);
+			folio_put(tail);
+		} else if (!PageAnon(page)) {
+			__xa_store(&head->mapping->i_pages, head[i].index,
+					head + i, 0);
+		} else if (swap_cache) {
+			__xa_store(&swap_cache->i_pages, offset + i,
+					head + i, 0);
+		}
+	}
+
+	ClearPageCompound(head);
+	unlock_page_lruvec(lruvec);
+	/* Caller disabled irqs, so they are still disabled here */
+
+	split_page_owner(head, nr);
+
+	/* See comment in __split_huge_page_tail() */
+	if (PageAnon(head)) {
+		/* Additional pin to swap cache */
+		if (PageSwapCache(head)) {
+			page_ref_add(head, 2);
+			xa_unlock(&swap_cache->i_pages);
+		} else {
+			page_ref_inc(head);
+		}
+	} else {
+		/* Additional pin to page cache */
+		page_ref_add(head, 2);
+		xa_unlock(&head->mapping->i_pages);
+	}
+	local_irq_enable();
+
+	remap_page(folio, nr);
+
+	if (PageSwapCache(head)) {
+		swp_entry_t entry = { .val = page_private(head) };
+
+		split_swap_cluster(entry);
+	}
+
+	for (i = 0; i < 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.
+		 */
+		free_page_and_swap_cache(subpage);
+	}
+}
+
+/* Racy check whether the huge page can be split */
+bool can_split_folio(struct folio *folio, int *pextra_pins)
+{
+	int extra_pins;
+
+	/* Additional pins from page cache */
+	if (folio_test_anon(folio))
+		extra_pins = folio_test_swapcache(folio) ?
+				folio_nr_pages(folio) : 0;
+	else
+		extra_pins = folio_nr_pages(folio);
+	if (pextra_pins)
+		*pextra_pins = extra_pins;
+	return folio_mapcount(folio) == folio_ref_count(folio) - 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 folio *folio = page_folio(page);
+	struct deferred_split *ds_queue = get_deferred_split_queue(&folio->page);
+	XA_STATE(xas, &folio->mapping->i_pages, folio->index);
+	struct anon_vma *anon_vma = NULL;
+	struct address_space *mapping = NULL;
+	int extra_pins, ret;
+	pgoff_t end;
+	bool is_hzp;
+
+	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+	VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
+
+	is_hzp = is_huge_zero_page(&folio->page);
+	if (is_hzp) {
+		pr_warn_ratelimited("Called split_huge_page for huge zero page\n");
+		return -EBUSY;
+	}
+
+	if (folio_test_writeback(folio))
+		return -EBUSY;
+
+	if (folio_test_anon(folio)) {
+		/*
+		 * The caller does not necessarily hold an mmap_lock 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 folio_lock_anon_vma_read except the write lock
+		 * is taken to serialise against parallel split or collapse
+		 * operations.
+		 */
+		anon_vma = folio_get_anon_vma(folio);
+		if (!anon_vma) {
+			ret = -EBUSY;
+			goto out;
+		}
+		end = -1;
+		mapping = NULL;
+		anon_vma_lock_write(anon_vma);
+	} else {
+		gfp_t gfp;
+
+		mapping = folio->mapping;
+
+		/* Truncated ? */
+		if (!mapping) {
+			ret = -EBUSY;
+			goto out;
+		}
+
+		gfp = current_gfp_context(mapping_gfp_mask(mapping) &
+							GFP_RECLAIM_MASK);
+
+		if (!filemap_release_folio(folio, gfp)) {
+			ret = -EBUSY;
+			goto out;
+		}
+
+		xas_split_alloc(&xas, folio, folio_order(folio), gfp);
+		if (xas_error(&xas)) {
+			ret = xas_error(&xas);
+			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
+		 * folio lock is good enough to serialize the trimming.
+		 */
+		end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
+		if (shmem_mapping(mapping))
+			end = shmem_fallocend(mapping->host, end);
+	}
+
+	/*
+	 * Racy check if we can split the page, before unmap_folio() will
+	 * split PMDs
+	 */
+	if (!can_split_folio(folio, &extra_pins)) {
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
+	unmap_folio(folio);
+
+	/* block interrupt reentry in xa_lock and spinlock */
+	local_irq_disable();
+	if (mapping) {
+		/*
+		 * Check if the folio is present in page cache.
+		 * We assume all tail are present too, if folio is there.
+		 */
+		xas_lock(&xas);
+		xas_reset(&xas);
+		if (xas_load(&xas) != folio)
+			goto fail;
+	}
+
+	/* Prevent deferred_split_scan() touching ->_refcount */
+	spin_lock(&ds_queue->split_queue_lock);
+	if (folio_ref_freeze(folio, 1 + extra_pins)) {
+		if (!list_empty(page_deferred_list(&folio->page))) {
+			ds_queue->split_queue_len--;
+			list_del(page_deferred_list(&folio->page));
+		}
+		spin_unlock(&ds_queue->split_queue_lock);
+		if (mapping) {
+			int nr = folio_nr_pages(folio);
+
+			xas_split(&xas, folio, folio_order(folio));
+			if (folio_test_pmd_mappable(folio)) {
+				if (folio_test_swapbacked(folio)) {
+					__lruvec_stat_mod_folio(folio,
+							NR_SHMEM_THPS, -nr);
+				} else {
+					__lruvec_stat_mod_folio(folio,
+							NR_FILE_THPS, -nr);
+					filemap_nr_thps_dec(mapping);
+				}
+			}
+		}
+
+		__split_huge_page(page, list, end);
+		ret = 0;
+	} else {
+		spin_unlock(&ds_queue->split_queue_lock);
+fail:
+		if (mapping)
+			xas_unlock(&xas);
+		local_irq_enable();
+		remap_page(folio, folio_nr_pages(folio));
+		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:
+	xas_destroy(&xas);
+	count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
+	return ret;
+}
+
+void free_transhuge_page(struct page *page)
+{
+	struct deferred_split *ds_queue = get_deferred_split_queue(page);
+	unsigned long flags;
+
+	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
+	if (!list_empty(page_deferred_list(page))) {
+		ds_queue->split_queue_len--;
+		list_del(page_deferred_list(page));
+	}
+	spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
+	free_compound_page(page);
+}
+
+void deferred_split_huge_page(struct page *page)
+{
+	struct deferred_split *ds_queue = get_deferred_split_queue(page);
+#ifdef CONFIG_MEMCG
+	struct mem_cgroup *memcg = page_memcg(compound_head(page));
+#endif
+	unsigned long flags;
+
+	VM_BUG_ON_PAGE(!PageTransHuge(page), page);
+
+	/*
+	 * The try_to_unmap() in page reclaim path might reach here too,
+	 * this may cause a race condition to corrupt deferred split queue.
+	 * And, if page reclaim is already handling the same page, it is
+	 * unnecessary to handle it again in shrinker.
+	 *
+	 * Check PageSwapCache to determine if the page is being
+	 * handled by page reclaim since THP swap would add the page into
+	 * swap cache before calling try_to_unmap().
+	 */
+	if (PageSwapCache(page))
+		return;
+
+	if (!list_empty(page_deferred_list(page)))
+		return;
+
+	spin_lock_irqsave(&ds_queue->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), &ds_queue->split_queue);
+		ds_queue->split_queue_len++;
+#ifdef CONFIG_MEMCG
+		if (memcg)
+			set_shrinker_bit(memcg, page_to_nid(page),
+					 deferred_split_shrinker.id);
+#endif
+	}
+	spin_unlock_irqrestore(&ds_queue->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);
+	struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
+
+#ifdef CONFIG_MEMCG
+	if (sc->memcg)
+		ds_queue = &sc->memcg->deferred_split_queue;
+#endif
+	return READ_ONCE(ds_queue->split_queue_len);
+}
+
+static unsigned long deferred_split_scan(struct shrinker *shrink,
+		struct shrink_control *sc)
+{
+	struct pglist_data *pgdata = NODE_DATA(sc->nid);
+	struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
+	unsigned long flags;
+	LIST_HEAD(list), *pos, *next;
+	struct page *page;
+	int split = 0;
+
+#ifdef CONFIG_MEMCG
+	if (sc->memcg)
+		ds_queue = &sc->memcg->deferred_split_queue;
+#endif
+
+	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
+	/* Take pin on all head pages to avoid freeing them under us */
+	list_for_each_safe(pos, next, &ds_queue->split_queue) {
+		page = list_entry((void *)pos, struct page, deferred_list);
+		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));
+			ds_queue->split_queue_len--;
+		}
+		if (!--sc->nr_to_scan)
+			break;
+	}
+	spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
+
+	list_for_each_safe(pos, next, &list) {
+		page = list_entry((void *)pos, struct page, deferred_list);
+		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(&ds_queue->split_queue_lock, flags);
+	list_splice_tail(&list, &ds_queue->split_queue);
+	spin_unlock_irqrestore(&ds_queue->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(&ds_queue->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 | SHRINKER_MEMCG_AWARE |
+		 SHRINKER_NONSLAB,
+};
+
+#ifdef CONFIG_DEBUG_FS
+static void split_huge_pages_all(void)
+{
+	struct zone *zone;
+	struct page *page;
+	unsigned long pfn, max_zone_pfn;
+	unsigned long total = 0, split = 0;
+
+	pr_debug("Split all THPs\n");
+	for_each_zone(zone) {
+		if (!managed_zone(zone))
+			continue;
+		max_zone_pfn = zone_end_pfn(zone);
+		for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
+			int nr_pages;
+
+			page = pfn_to_online_page(pfn);
+			if (!page || !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);
+			nr_pages = thp_nr_pages(page);
+			if (!split_huge_page(page))
+				split++;
+			pfn += nr_pages - 1;
+			unlock_page(page);
+next:
+			put_page(page);
+			cond_resched();
+		}
+	}
+
+	pr_debug("%lu of %lu THP split\n", split, total);
+}
+
+static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma)
+{
+	return vma_is_special_huge(vma) || (vma->vm_flags & VM_IO) ||
+		    is_vm_hugetlb_page(vma);
+}
+
+static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
+				unsigned long vaddr_end)
+{
+	int ret = 0;
+	struct task_struct *task;
+	struct mm_struct *mm;
+	unsigned long total = 0, split = 0;
+	unsigned long addr;
+
+	vaddr_start &= PAGE_MASK;
+	vaddr_end &= PAGE_MASK;
+
+	/* Find the task_struct from pid */
+	rcu_read_lock();
+	task = find_task_by_vpid(pid);
+	if (!task) {
+		rcu_read_unlock();
+		ret = -ESRCH;
+		goto out;
+	}
+	get_task_struct(task);
+	rcu_read_unlock();
+
+	/* Find the mm_struct */
+	mm = get_task_mm(task);
+	put_task_struct(task);
+
+	if (!mm) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",
+		 pid, vaddr_start, vaddr_end);
+
+	mmap_read_lock(mm);
+	/*
+	 * always increase addr by PAGE_SIZE, since we could have a PTE page
+	 * table filled with PTE-mapped THPs, each of which is distinct.
+	 */
+	for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
+		struct vm_area_struct *vma = vma_lookup(mm, addr);
+		struct page *page;
+
+		if (!vma)
+			break;
+
+		/* skip special VMA and hugetlb VMA */
+		if (vma_not_suitable_for_thp_split(vma)) {
+			addr = vma->vm_end;
+			continue;
+		}
+
+		/* FOLL_DUMP to ignore special (like zero) pages */
+		page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
+
+		if (IS_ERR_OR_NULL(page))
+			continue;
+
+		if (!is_transparent_hugepage(page))
+			goto next;
+
+		total++;
+		if (!can_split_folio(page_folio(page), NULL))
+			goto next;
+
+		if (!trylock_page(page))
+			goto next;
+
+		if (!split_huge_page(page))
+			split++;
+
+		unlock_page(page);
+next:
+		put_page(page);
+		cond_resched();
+	}
+	mmap_read_unlock(mm);
+	mmput(mm);
+
+	pr_debug("%lu of %lu THP split\n", split, total);
+
+out:
+	return ret;
+}
+
+static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
+				pgoff_t off_end)
+{
+	struct filename *file;
+	struct file *candidate;
+	struct address_space *mapping;
+	int ret = -EINVAL;
+	pgoff_t index;
+	int nr_pages = 1;
+	unsigned long total = 0, split = 0;
+
+	file = getname_kernel(file_path);
+	if (IS_ERR(file))
+		return ret;
+
+	candidate = file_open_name(file, O_RDONLY, 0);
+	if (IS_ERR(candidate))
+		goto out;
+
+	pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
+		 file_path, off_start, off_end);
+
+	mapping = candidate->f_mapping;
+
+	for (index = off_start; index < off_end; index += nr_pages) {
+		struct page *fpage = pagecache_get_page(mapping, index,
+						FGP_ENTRY | FGP_HEAD, 0);
+
+		nr_pages = 1;
+		if (xa_is_value(fpage) || !fpage)
+			continue;
+
+		if (!is_transparent_hugepage(fpage))
+			goto next;
+
+		total++;
+		nr_pages = thp_nr_pages(fpage);
+
+		if (!trylock_page(fpage))
+			goto next;
+
+		if (!split_huge_page(fpage))
+			split++;
+
+		unlock_page(fpage);
+next:
+		put_page(fpage);
+		cond_resched();
+	}
+
+	filp_close(candidate, NULL);
+	ret = 0;
+
+	pr_debug("%lu of %lu file-backed THP split\n", split, total);
+out:
+	putname(file);
+	return ret;
+}
+
+#define MAX_INPUT_BUF_SZ 255
+
+static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppops)
+{
+	static DEFINE_MUTEX(split_debug_mutex);
+	ssize_t ret;
+	/* hold pid, start_vaddr, end_vaddr or file_path, off_start, off_end */
+	char input_buf[MAX_INPUT_BUF_SZ];
+	int pid;
+	unsigned long vaddr_start, vaddr_end;
+
+	ret = mutex_lock_interruptible(&split_debug_mutex);
+	if (ret)
+		return ret;
+
+	ret = -EFAULT;
+
+	memset(input_buf, 0, MAX_INPUT_BUF_SZ);
+	if (copy_from_user(input_buf, buf, min_t(size_t, count, MAX_INPUT_BUF_SZ)))
+		goto out;
+
+	input_buf[MAX_INPUT_BUF_SZ - 1] = '\0';
+
+	if (input_buf[0] == '/') {
+		char *tok;
+		char *buf = input_buf;
+		char file_path[MAX_INPUT_BUF_SZ];
+		pgoff_t off_start = 0, off_end = 0;
+		size_t input_len = strlen(input_buf);
+
+		tok = strsep(&buf, ",");
+		if (tok) {
+			strcpy(file_path, tok);
+		} else {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		ret = sscanf(buf, "0x%lx,0x%lx", &off_start, &off_end);
+		if (ret != 2) {
+			ret = -EINVAL;
+			goto out;
+		}
+		ret = split_huge_pages_in_file(file_path, off_start, off_end);
+		if (!ret)
+			ret = input_len;
+
+		goto out;
+	}
+
+	ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
+	if (ret == 1 && pid == 1) {
+		split_huge_pages_all();
+		ret = strlen(input_buf);
+		goto out;
+	} else if (ret != 3) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end);
+	if (!ret)
+		ret = strlen(input_buf);
+out:
+	mutex_unlock(&split_debug_mutex);
+	return ret;
+
+}
+
+static const struct file_operations split_huge_pages_fops = {
+	.owner	 = THIS_MODULE,
+	.write	 = split_huge_pages_write,
+	.llseek  = no_llseek,
+};
+
+static int __init split_huge_pages_debugfs(void)
+{
+	debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
+			    &split_huge_pages_fops);
+	return 0;
+}
+late_initcall(split_huge_pages_debugfs);
+#endif
+
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+int 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;
+	bool anon_exclusive;
+	pmd_t pmdval;
+	swp_entry_t entry;
+	pmd_t pmdswp;
+
+	if (!(pvmw->pmd && !pvmw->pte))
+		return 0;
+
+	flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
+	pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
+
+	/* See page_try_share_anon_rmap(): invalidate PMD first. */
+	anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
+	if (anon_exclusive && page_try_share_anon_rmap(page)) {
+		set_pmd_at(mm, address, pvmw->pmd, pmdval);
+		return -EBUSY;
+	}
+
+	if (pmd_dirty(pmdval))
+		set_page_dirty(page);
+	if (pmd_write(pmdval))
+		entry = make_writable_migration_entry(page_to_pfn(page));
+	else if (anon_exclusive)
+		entry = make_readable_exclusive_migration_entry(page_to_pfn(page));
+	else
+		entry = make_readable_migration_entry(page_to_pfn(page));
+	if (pmd_young(pmdval))
+		entry = make_migration_entry_young(entry);
+	if (pmd_dirty(pmdval))
+		entry = make_migration_entry_dirty(entry);
+	pmdswp = swp_entry_to_pmd(entry);
+	if (pmd_soft_dirty(pmdval))
+		pmdswp = pmd_swp_mksoft_dirty(pmdswp);
+	if (pmd_uffd_wp(pmdval))
+		pmdswp = pmd_swp_mkuffd_wp(pmdswp);
+	set_pmd_at(mm, address, pvmw->pmd, pmdswp);
+	page_remove_rmap(page, vma, true);
+	put_page(page);
+	trace_set_migration_pmd(address, pmd_val(pmdswp));
+
+	return 0;
+}
+
+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 haddr = 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 = mk_huge_pmd(new, READ_ONCE(vma->vm_page_prot));
+	if (pmd_swp_soft_dirty(*pvmw->pmd))
+		pmde = pmd_mksoft_dirty(pmde);
+	if (pmd_swp_uffd_wp(*pvmw->pmd))
+		pmde = pmd_wrprotect(pmd_mkuffd_wp(pmde));
+	if (!is_migration_entry_young(entry))
+		pmde = pmd_mkold(pmde);
+	/* NOTE: this may contain setting soft-dirty on some archs */
+	if (PageDirty(new) && is_migration_entry_dirty(entry))
+		pmde = pmd_mkdirty(pmde);
+	if (is_writable_migration_entry(entry))
+		pmde = maybe_pmd_mkwrite(pmde, vma);
+	else
+		pmde = pmd_wrprotect(pmde);
+
+	if (PageAnon(new)) {
+		rmap_t rmap_flags = RMAP_COMPOUND;
+
+		if (!is_readable_migration_entry(entry))
+			rmap_flags |= RMAP_EXCLUSIVE;
+
+		page_add_anon_rmap(new, vma, haddr, rmap_flags);
+	} else {
+		page_add_file_rmap(new, vma, true);
+	}
+	VM_BUG_ON(pmd_write(pmde) && PageAnon(new) && !PageAnonExclusive(new));
+	set_pmd_at(mm, haddr, pvmw->pmd, pmde);
+
+	/* No need to invalidate - it was non-present before */
+	update_mmu_cache_pmd(vma, address, pvmw->pmd);
+	trace_remove_migration_pmd(address, pmd_val(pmde));
+}
+#endif