huge_memory.c 73.8 KB
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/*
 *  Copyright (C) 2009  Red Hat, Inc.
 *
 *  This work is licensed under the terms of the GNU GPL, version 2. See
 *  the COPYING file in the top-level directory.
 */

#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/hugetlb.h>
#include <linux/mmu_notifier.h>
#include <linux/rmap.h>
#include <linux/swap.h>
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#include <linux/shrinker.h>
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#include <linux/mm_inline.h>
#include <linux/kthread.h>
#include <linux/khugepaged.h>
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#include <linux/freezer.h>
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#include <linux/mman.h>
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#include <linux/pagemap.h>
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#include <linux/migrate.h>
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#include <asm/tlb.h>
#include <asm/pgalloc.h>
#include "internal.h"

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/*
 * By default transparent hugepage support is enabled for all mappings
 * and khugepaged scans all mappings. Defrag is only invoked by
 * khugepaged hugepage allocations and by page faults inside
 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
 * allocations.
 */
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unsigned long transparent_hugepage_flags __read_mostly =
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
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	(1<<TRANSPARENT_HUGEPAGE_FLAG)|
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#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
	(1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
#endif
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	(1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
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	(1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
	(1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
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/* default scan 8*512 pte (or vmas) every 30 second */
static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
static unsigned int khugepaged_pages_collapsed;
static unsigned int khugepaged_full_scans;
static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
/* during fragmentation poll the hugepage allocator once every minute */
static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
static struct task_struct *khugepaged_thread __read_mostly;
static DEFINE_MUTEX(khugepaged_mutex);
static DEFINE_SPINLOCK(khugepaged_mm_lock);
static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
/*
 * default collapse hugepages if there is at least one pte mapped like
 * it would have happened if the vma was large enough during page
 * fault.
 */
static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;

static int khugepaged(void *none);
static int mm_slots_hash_init(void);
static int khugepaged_slab_init(void);
static void khugepaged_slab_free(void);

#define MM_SLOTS_HASH_HEADS 1024
static struct hlist_head *mm_slots_hash __read_mostly;
static struct kmem_cache *mm_slot_cache __read_mostly;

/**
 * struct mm_slot - hash lookup from mm to mm_slot
 * @hash: hash collision list
 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
 * @mm: the mm that this information is valid for
 */
struct mm_slot {
	struct hlist_node hash;
	struct list_head mm_node;
	struct mm_struct *mm;
};

/**
 * struct khugepaged_scan - cursor for scanning
 * @mm_head: the head of the mm list to scan
 * @mm_slot: the current mm_slot we are scanning
 * @address: the next address inside that to be scanned
 *
 * There is only the one khugepaged_scan instance of this cursor structure.
 */
struct khugepaged_scan {
	struct list_head mm_head;
	struct mm_slot *mm_slot;
	unsigned long address;
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};
static struct khugepaged_scan khugepaged_scan = {
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	.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
};

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static int set_recommended_min_free_kbytes(void)
{
	struct zone *zone;
	int nr_zones = 0;
	unsigned long recommended_min;
	extern int min_free_kbytes;

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	if (!khugepaged_enabled())
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		return 0;

	for_each_populated_zone(zone)
		nr_zones++;

	/* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
	recommended_min = pageblock_nr_pages * nr_zones * 2;

	/*
	 * Make sure that on average at least two pageblocks are almost free
	 * of another type, one for a migratetype to fall back to and a
	 * second to avoid subsequent fallbacks of other types There are 3
	 * MIGRATE_TYPES we care about.
	 */
	recommended_min += pageblock_nr_pages * nr_zones *
			   MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;

	/* don't ever allow to reserve more than 5% of the lowmem */
	recommended_min = min(recommended_min,
			      (unsigned long) nr_free_buffer_pages() / 20);
	recommended_min <<= (PAGE_SHIFT-10);

	if (recommended_min > min_free_kbytes)
		min_free_kbytes = recommended_min;
	setup_per_zone_wmarks();
	return 0;
}
late_initcall(set_recommended_min_free_kbytes);

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static int start_khugepaged(void)
{
	int err = 0;
	if (khugepaged_enabled()) {
		if (!khugepaged_thread)
			khugepaged_thread = kthread_run(khugepaged, NULL,
							"khugepaged");
		if (unlikely(IS_ERR(khugepaged_thread))) {
			printk(KERN_ERR
			       "khugepaged: kthread_run(khugepaged) failed\n");
			err = PTR_ERR(khugepaged_thread);
			khugepaged_thread = NULL;
		}
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		if (!list_empty(&khugepaged_scan.mm_head))
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			wake_up_interruptible(&khugepaged_wait);
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		set_recommended_min_free_kbytes();
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	} else if (khugepaged_thread) {
		kthread_stop(khugepaged_thread);
		khugepaged_thread = NULL;
	}
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	return err;
}
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static atomic_t huge_zero_refcount;
static unsigned long huge_zero_pfn __read_mostly;

static inline bool is_huge_zero_pfn(unsigned long pfn)
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{
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	unsigned long zero_pfn = ACCESS_ONCE(huge_zero_pfn);
	return zero_pfn && pfn == zero_pfn;
}
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static inline bool is_huge_zero_pmd(pmd_t pmd)
{
	return is_huge_zero_pfn(pmd_pfn(pmd));
}

static unsigned long get_huge_zero_page(void)
{
	struct page *zero_page;
retry:
	if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
		return ACCESS_ONCE(huge_zero_pfn);

	zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
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			HPAGE_PMD_ORDER);
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	if (!zero_page) {
		count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
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		return 0;
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	}
	count_vm_event(THP_ZERO_PAGE_ALLOC);
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	preempt_disable();
	if (cmpxchg(&huge_zero_pfn, 0, page_to_pfn(zero_page))) {
		preempt_enable();
		__free_page(zero_page);
		goto retry;
	}

	/* We take additional reference here. It will be put back by shrinker */
	atomic_set(&huge_zero_refcount, 2);
	preempt_enable();
	return ACCESS_ONCE(huge_zero_pfn);
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}

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static void put_huge_zero_page(void)
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{
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	/*
	 * Counter should never go to zero here. Only shrinker can put
	 * last reference.
	 */
	BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
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}

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static int shrink_huge_zero_page(struct shrinker *shrink,
		struct shrink_control *sc)
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{
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	if (!sc->nr_to_scan)
		/* we can free zero page only if last reference remains */
		return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;

	if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
		unsigned long zero_pfn = xchg(&huge_zero_pfn, 0);
		BUG_ON(zero_pfn == 0);
		__free_page(__pfn_to_page(zero_pfn));
	}

	return 0;
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}

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static struct shrinker huge_zero_page_shrinker = {
	.shrink = shrink_huge_zero_page,
	.seeks = DEFAULT_SEEKS,
};

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#ifdef CONFIG_SYSFS
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static ssize_t double_flag_show(struct kobject *kobj,
				struct kobj_attribute *attr, char *buf,
				enum transparent_hugepage_flag enabled,
				enum transparent_hugepage_flag req_madv)
{
	if (test_bit(enabled, &transparent_hugepage_flags)) {
		VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
		return sprintf(buf, "[always] madvise never\n");
	} else if (test_bit(req_madv, &transparent_hugepage_flags))
		return sprintf(buf, "always [madvise] never\n");
	else
		return sprintf(buf, "always madvise [never]\n");
}
static ssize_t double_flag_store(struct kobject *kobj,
				 struct kobj_attribute *attr,
				 const char *buf, size_t count,
				 enum transparent_hugepage_flag enabled,
				 enum transparent_hugepage_flag req_madv)
{
	if (!memcmp("always", buf,
		    min(sizeof("always")-1, count))) {
		set_bit(enabled, &transparent_hugepage_flags);
		clear_bit(req_madv, &transparent_hugepage_flags);
	} else if (!memcmp("madvise", buf,
			   min(sizeof("madvise")-1, count))) {
		clear_bit(enabled, &transparent_hugepage_flags);
		set_bit(req_madv, &transparent_hugepage_flags);
	} else if (!memcmp("never", buf,
			   min(sizeof("never")-1, count))) {
		clear_bit(enabled, &transparent_hugepage_flags);
		clear_bit(req_madv, &transparent_hugepage_flags);
	} else
		return -EINVAL;

	return count;
}

static ssize_t enabled_show(struct kobject *kobj,
			    struct kobj_attribute *attr, char *buf)
{
	return double_flag_show(kobj, attr, buf,
				TRANSPARENT_HUGEPAGE_FLAG,
				TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
}
static ssize_t enabled_store(struct kobject *kobj,
			     struct kobj_attribute *attr,
			     const char *buf, size_t count)
{
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	ssize_t ret;

	ret = double_flag_store(kobj, attr, buf, count,
				TRANSPARENT_HUGEPAGE_FLAG,
				TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);

	if (ret > 0) {
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		int err;

		mutex_lock(&khugepaged_mutex);
		err = start_khugepaged();
		mutex_unlock(&khugepaged_mutex);

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		if (err)
			ret = err;
	}

	return ret;
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}
static struct kobj_attribute enabled_attr =
	__ATTR(enabled, 0644, enabled_show, enabled_store);

static ssize_t single_flag_show(struct kobject *kobj,
				struct kobj_attribute *attr, char *buf,
				enum transparent_hugepage_flag flag)
{
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	return sprintf(buf, "%d\n",
		       !!test_bit(flag, &transparent_hugepage_flags));
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}
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static ssize_t single_flag_store(struct kobject *kobj,
				 struct kobj_attribute *attr,
				 const char *buf, size_t count,
				 enum transparent_hugepage_flag flag)
{
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	unsigned long value;
	int ret;

	ret = kstrtoul(buf, 10, &value);
	if (ret < 0)
		return ret;
	if (value > 1)
		return -EINVAL;

	if (value)
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		set_bit(flag, &transparent_hugepage_flags);
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	else
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		clear_bit(flag, &transparent_hugepage_flags);

	return count;
}

/*
 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
 * memory just to allocate one more hugepage.
 */
static ssize_t defrag_show(struct kobject *kobj,
			   struct kobj_attribute *attr, char *buf)
{
	return double_flag_show(kobj, attr, buf,
				TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
				TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
}
static ssize_t defrag_store(struct kobject *kobj,
			    struct kobj_attribute *attr,
			    const char *buf, size_t count)
{
	return double_flag_store(kobj, attr, buf, count,
				 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
				 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
}
static struct kobj_attribute defrag_attr =
	__ATTR(defrag, 0644, defrag_show, defrag_store);

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static ssize_t use_zero_page_show(struct kobject *kobj,
		struct kobj_attribute *attr, char *buf)
{
	return single_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_flag_store(kobj, attr, buf, count,
				 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
}
static struct kobj_attribute use_zero_page_attr =
	__ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
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#ifdef CONFIG_DEBUG_VM
static ssize_t debug_cow_show(struct kobject *kobj,
				struct kobj_attribute *attr, char *buf)
{
	return single_flag_show(kobj, attr, buf,
				TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
}
static ssize_t debug_cow_store(struct kobject *kobj,
			       struct kobj_attribute *attr,
			       const char *buf, size_t count)
{
	return single_flag_store(kobj, attr, buf, count,
				 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
}
static struct kobj_attribute debug_cow_attr =
	__ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
#endif /* CONFIG_DEBUG_VM */

static struct attribute *hugepage_attr[] = {
	&enabled_attr.attr,
	&defrag_attr.attr,
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	&use_zero_page_attr.attr,
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#ifdef CONFIG_DEBUG_VM
	&debug_cow_attr.attr,
#endif
	NULL,
};

static struct attribute_group hugepage_attr_group = {
	.attrs = hugepage_attr,
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};

static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
					 struct kobj_attribute *attr,
					 char *buf)
{
	return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
}

static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
					  struct kobj_attribute *attr,
					  const char *buf, size_t count)
{
	unsigned long msecs;
	int err;

	err = strict_strtoul(buf, 10, &msecs);
	if (err || msecs > UINT_MAX)
		return -EINVAL;

	khugepaged_scan_sleep_millisecs = msecs;
	wake_up_interruptible(&khugepaged_wait);

	return count;
}
static struct kobj_attribute scan_sleep_millisecs_attr =
	__ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
	       scan_sleep_millisecs_store);

static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
					  struct kobj_attribute *attr,
					  char *buf)
{
	return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
}

static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
					   struct kobj_attribute *attr,
					   const char *buf, size_t count)
{
	unsigned long msecs;
	int err;

	err = strict_strtoul(buf, 10, &msecs);
	if (err || msecs > UINT_MAX)
		return -EINVAL;

	khugepaged_alloc_sleep_millisecs = msecs;
	wake_up_interruptible(&khugepaged_wait);

	return count;
}
static struct kobj_attribute alloc_sleep_millisecs_attr =
	__ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
	       alloc_sleep_millisecs_store);

static ssize_t pages_to_scan_show(struct kobject *kobj,
				  struct kobj_attribute *attr,
				  char *buf)
{
	return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
}
static ssize_t pages_to_scan_store(struct kobject *kobj,
				   struct kobj_attribute *attr,
				   const char *buf, size_t count)
{
	int err;
	unsigned long pages;

	err = strict_strtoul(buf, 10, &pages);
	if (err || !pages || pages > UINT_MAX)
		return -EINVAL;

	khugepaged_pages_to_scan = pages;

	return count;
}
static struct kobj_attribute pages_to_scan_attr =
	__ATTR(pages_to_scan, 0644, pages_to_scan_show,
	       pages_to_scan_store);

static ssize_t pages_collapsed_show(struct kobject *kobj,
				    struct kobj_attribute *attr,
				    char *buf)
{
	return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
}
static struct kobj_attribute pages_collapsed_attr =
	__ATTR_RO(pages_collapsed);

static ssize_t full_scans_show(struct kobject *kobj,
			       struct kobj_attribute *attr,
			       char *buf)
{
	return sprintf(buf, "%u\n", khugepaged_full_scans);
}
static struct kobj_attribute full_scans_attr =
	__ATTR_RO(full_scans);

static ssize_t khugepaged_defrag_show(struct kobject *kobj,
				      struct kobj_attribute *attr, char *buf)
{
	return single_flag_show(kobj, attr, buf,
				TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
}
static ssize_t khugepaged_defrag_store(struct kobject *kobj,
				       struct kobj_attribute *attr,
				       const char *buf, size_t count)
{
	return single_flag_store(kobj, attr, buf, count,
				 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
}
static struct kobj_attribute khugepaged_defrag_attr =
	__ATTR(defrag, 0644, khugepaged_defrag_show,
	       khugepaged_defrag_store);

/*
 * max_ptes_none controls if khugepaged should collapse hugepages over
 * any unmapped ptes in turn potentially increasing the memory
 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
 * reduce the available free memory in the system as it
 * runs. Increasing max_ptes_none will instead potentially reduce the
 * free memory in the system during the khugepaged scan.
 */
static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
					     struct kobj_attribute *attr,
					     char *buf)
{
	return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
}
static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
					      struct kobj_attribute *attr,
					      const char *buf, size_t count)
{
	int err;
	unsigned long max_ptes_none;

	err = strict_strtoul(buf, 10, &max_ptes_none);
	if (err || max_ptes_none > HPAGE_PMD_NR-1)
		return -EINVAL;

	khugepaged_max_ptes_none = max_ptes_none;

	return count;
}
static struct kobj_attribute khugepaged_max_ptes_none_attr =
	__ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
	       khugepaged_max_ptes_none_store);

static struct attribute *khugepaged_attr[] = {
	&khugepaged_defrag_attr.attr,
	&khugepaged_max_ptes_none_attr.attr,
	&pages_to_scan_attr.attr,
	&pages_collapsed_attr.attr,
	&full_scans_attr.attr,
	&scan_sleep_millisecs_attr.attr,
	&alloc_sleep_millisecs_attr.attr,
	NULL,
};

static struct attribute_group khugepaged_attr_group = {
	.attrs = khugepaged_attr,
	.name = "khugepaged",
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};

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static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
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{
	int err;

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	*hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
	if (unlikely(!*hugepage_kobj)) {
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		printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n");
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		return -ENOMEM;
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	}

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	err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
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	if (err) {
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		printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
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		goto delete_obj;
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	}

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	err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
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	if (err) {
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		printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
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		goto remove_hp_group;
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	}
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	return 0;

remove_hp_group:
	sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
delete_obj:
	kobject_put(*hugepage_kobj);
	return err;
}

static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
{
	sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
	sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
	kobject_put(hugepage_kobj);
}
#else
static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
{
	return 0;
}

static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
{
}
#endif /* CONFIG_SYSFS */

static int __init hugepage_init(void)
{
	int err;
	struct kobject *hugepage_kobj;

	if (!has_transparent_hugepage()) {
		transparent_hugepage_flags = 0;
		return -EINVAL;
	}

	err = hugepage_init_sysfs(&hugepage_kobj);
	if (err)
		return err;
A
Andrea Arcangeli 已提交
632 633 634 635 636 637 638 639 640 641 642

	err = khugepaged_slab_init();
	if (err)
		goto out;

	err = mm_slots_hash_init();
	if (err) {
		khugepaged_slab_free();
		goto out;
	}

643 644
	register_shrinker(&huge_zero_page_shrinker);

645 646 647 648 649 650 651 652
	/*
	 * 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;

A
Andrea Arcangeli 已提交
653 654
	start_khugepaged();

S
Shaohua Li 已提交
655
	return 0;
A
Andrea Arcangeli 已提交
656
out:
S
Shaohua Li 已提交
657
	hugepage_exit_sysfs(hugepage_kobj);
A
Andrea Arcangeli 已提交
658
	return err;
659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693
}
module_init(hugepage_init)

static int __init setup_transparent_hugepage(char *str)
{
	int ret = 0;
	if (!str)
		goto out;
	if (!strcmp(str, "always")) {
		set_bit(TRANSPARENT_HUGEPAGE_FLAG,
			&transparent_hugepage_flags);
		clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
			  &transparent_hugepage_flags);
		ret = 1;
	} else if (!strcmp(str, "madvise")) {
		clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
			  &transparent_hugepage_flags);
		set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
			&transparent_hugepage_flags);
		ret = 1;
	} else if (!strcmp(str, "never")) {
		clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
			  &transparent_hugepage_flags);
		clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
			  &transparent_hugepage_flags);
		ret = 1;
	}
out:
	if (!ret)
		printk(KERN_WARNING
		       "transparent_hugepage= cannot parse, ignored\n");
	return ret;
}
__setup("transparent_hugepage=", setup_transparent_hugepage);

694
pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
695 696 697 698 699 700
{
	if (likely(vma->vm_flags & VM_WRITE))
		pmd = pmd_mkwrite(pmd);
	return pmd;
}

B
Bob Liu 已提交
701 702 703 704 705 706 707 708 709
static inline pmd_t mk_huge_pmd(struct page *page, struct vm_area_struct *vma)
{
	pmd_t entry;
	entry = mk_pmd(page, vma->vm_page_prot);
	entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
	entry = pmd_mkhuge(entry);
	return entry;
}

710 711 712 713 714 715 716 717 718
static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
					struct vm_area_struct *vma,
					unsigned long haddr, pmd_t *pmd,
					struct page *page)
{
	pgtable_t pgtable;

	VM_BUG_ON(!PageCompound(page));
	pgtable = pte_alloc_one(mm, haddr);
719
	if (unlikely(!pgtable))
720 721 722 723 724 725 726 727
		return VM_FAULT_OOM;

	clear_huge_page(page, haddr, HPAGE_PMD_NR);
	__SetPageUptodate(page);

	spin_lock(&mm->page_table_lock);
	if (unlikely(!pmd_none(*pmd))) {
		spin_unlock(&mm->page_table_lock);
A
Andrea Arcangeli 已提交
728
		mem_cgroup_uncharge_page(page);
729 730 731 732
		put_page(page);
		pte_free(mm, pgtable);
	} else {
		pmd_t entry;
B
Bob Liu 已提交
733
		entry = mk_huge_pmd(page, vma);
734 735 736 737 738 739 740 741
		/*
		 * The spinlocking to take the lru_lock inside
		 * page_add_new_anon_rmap() acts as a full memory
		 * barrier to be sure clear_huge_page writes become
		 * visible after the set_pmd_at() write.
		 */
		page_add_new_anon_rmap(page, vma, haddr);
		set_pmd_at(mm, haddr, pmd, entry);
742
		pgtable_trans_huge_deposit(mm, pgtable);
743
		add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
744
		mm->nr_ptes++;
745 746 747
		spin_unlock(&mm->page_table_lock);
	}

748
	return 0;
749 750
}

751
static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
752
{
753
	return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
754 755 756 757
}

static inline struct page *alloc_hugepage_vma(int defrag,
					      struct vm_area_struct *vma,
758 759
					      unsigned long haddr, int nd,
					      gfp_t extra_gfp)
760
{
761
	return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
762
			       HPAGE_PMD_ORDER, vma, haddr, nd);
763 764 765
}

#ifndef CONFIG_NUMA
766 767
static inline struct page *alloc_hugepage(int defrag)
{
768
	return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
769 770
			   HPAGE_PMD_ORDER);
}
771
#endif
772

773
static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
774 775
		struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
		unsigned long zero_pfn)
776 777
{
	pmd_t entry;
778 779
	if (!pmd_none(*pmd))
		return false;
780
	entry = pfn_pmd(zero_pfn, vma->vm_page_prot);
781 782 783 784 785
	entry = pmd_wrprotect(entry);
	entry = pmd_mkhuge(entry);
	set_pmd_at(mm, haddr, pmd, entry);
	pgtable_trans_huge_deposit(mm, pgtable);
	mm->nr_ptes++;
786
	return true;
787 788
}

789 790 791 792 793 794 795 796 797 798 799
int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
			       unsigned long address, pmd_t *pmd,
			       unsigned int flags)
{
	struct page *page;
	unsigned long haddr = address & HPAGE_PMD_MASK;
	pte_t *pte;

	if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
		if (unlikely(anon_vma_prepare(vma)))
			return VM_FAULT_OOM;
A
Andrea Arcangeli 已提交
800 801
		if (unlikely(khugepaged_enter(vma)))
			return VM_FAULT_OOM;
802 803
		if (!(flags & FAULT_FLAG_WRITE) &&
				transparent_hugepage_use_zero_page()) {
804
			pgtable_t pgtable;
805
			unsigned long zero_pfn;
806
			bool set;
807 808 809
			pgtable = pte_alloc_one(mm, haddr);
			if (unlikely(!pgtable))
				return VM_FAULT_OOM;
810 811 812 813 814 815
			zero_pfn = get_huge_zero_page();
			if (unlikely(!zero_pfn)) {
				pte_free(mm, pgtable);
				count_vm_event(THP_FAULT_FALLBACK);
				goto out;
			}
816
			spin_lock(&mm->page_table_lock);
817
			set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
818
					zero_pfn);
819
			spin_unlock(&mm->page_table_lock);
820 821 822 823
			if (!set) {
				pte_free(mm, pgtable);
				put_huge_zero_page();
			}
824 825
			return 0;
		}
826
		page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
827
					  vma, haddr, numa_node_id(), 0);
828 829
		if (unlikely(!page)) {
			count_vm_event(THP_FAULT_FALLBACK);
830
			goto out;
831 832
		}
		count_vm_event(THP_FAULT_ALLOC);
A
Andrea Arcangeli 已提交
833 834 835 836
		if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
			put_page(page);
			goto out;
		}
837 838 839 840 841 842
		if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
							  page))) {
			mem_cgroup_uncharge_page(page);
			put_page(page);
			goto out;
		}
843

844
		return 0;
845 846 847 848 849 850 851
	}
out:
	/*
	 * Use __pte_alloc instead of pte_alloc_map, because we can't
	 * run pte_offset_map on the pmd, if an huge pmd could
	 * materialize from under us from a different thread.
	 */
852 853
	if (unlikely(pmd_none(*pmd)) &&
	    unlikely(__pte_alloc(mm, vma, pmd, address)))
854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890
		return VM_FAULT_OOM;
	/* if an huge pmd materialized from under us just retry later */
	if (unlikely(pmd_trans_huge(*pmd)))
		return 0;
	/*
	 * A regular pmd is established and it can't morph into a huge pmd
	 * from under us anymore at this point because we hold the mmap_sem
	 * read mode and khugepaged takes it in write mode. So now it's
	 * safe to run pte_offset_map().
	 */
	pte = pte_offset_map(pmd, address);
	return handle_pte_fault(mm, vma, address, pte, pmd, flags);
}

int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
		  pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
		  struct vm_area_struct *vma)
{
	struct page *src_page;
	pmd_t pmd;
	pgtable_t pgtable;
	int ret;

	ret = -ENOMEM;
	pgtable = pte_alloc_one(dst_mm, addr);
	if (unlikely(!pgtable))
		goto out;

	spin_lock(&dst_mm->page_table_lock);
	spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);

	ret = -EAGAIN;
	pmd = *src_pmd;
	if (unlikely(!pmd_trans_huge(pmd))) {
		pte_free(dst_mm, pgtable);
		goto out_unlock;
	}
891 892 893 894 895 896
	/*
	 * mm->page_table_lock is enough to be sure that huge zero pmd is not
	 * under splitting since we don't split the page itself, only pmd to
	 * a page table.
	 */
	if (is_huge_zero_pmd(pmd)) {
897
		unsigned long zero_pfn;
898
		bool set;
899 900 901 902 903 904
		/*
		 * get_huge_zero_page() will never allocate a new page here,
		 * since we already have a zero page to copy. It just takes a
		 * reference.
		 */
		zero_pfn = get_huge_zero_page();
905
		set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
906
				zero_pfn);
907
		BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
908 909 910
		ret = 0;
		goto out_unlock;
	}
911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928
	if (unlikely(pmd_trans_splitting(pmd))) {
		/* split huge page running from under us */
		spin_unlock(&src_mm->page_table_lock);
		spin_unlock(&dst_mm->page_table_lock);
		pte_free(dst_mm, pgtable);

		wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
		goto out;
	}
	src_page = pmd_page(pmd);
	VM_BUG_ON(!PageHead(src_page));
	get_page(src_page);
	page_dup_rmap(src_page);
	add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);

	pmdp_set_wrprotect(src_mm, addr, src_pmd);
	pmd = pmd_mkold(pmd_wrprotect(pmd));
	set_pmd_at(dst_mm, addr, dst_pmd, pmd);
929
	pgtable_trans_huge_deposit(dst_mm, pgtable);
930
	dst_mm->nr_ptes++;
931 932 933 934 935 936 937 938 939

	ret = 0;
out_unlock:
	spin_unlock(&src_mm->page_table_lock);
	spin_unlock(&dst_mm->page_table_lock);
out:
	return ret;
}

940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961
void huge_pmd_set_accessed(struct mm_struct *mm,
			   struct vm_area_struct *vma,
			   unsigned long address,
			   pmd_t *pmd, pmd_t orig_pmd,
			   int dirty)
{
	pmd_t entry;
	unsigned long haddr;

	spin_lock(&mm->page_table_lock);
	if (unlikely(!pmd_same(*pmd, orig_pmd)))
		goto unlock;

	entry = pmd_mkyoung(orig_pmd);
	haddr = address & HPAGE_PMD_MASK;
	if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
		update_mmu_cache_pmd(vma, address, pmd);

unlock:
	spin_unlock(&mm->page_table_lock);
}

962 963
static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
		struct vm_area_struct *vma, unsigned long address,
964
		pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992
{
	pgtable_t pgtable;
	pmd_t _pmd;
	struct page *page;
	int i, ret = 0;
	unsigned long mmun_start;	/* For mmu_notifiers */
	unsigned long mmun_end;		/* For mmu_notifiers */

	page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
	if (!page) {
		ret |= VM_FAULT_OOM;
		goto out;
	}

	if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
		put_page(page);
		ret |= VM_FAULT_OOM;
		goto out;
	}

	clear_user_highpage(page, address);
	__SetPageUptodate(page);

	mmun_start = haddr;
	mmun_end   = haddr + HPAGE_PMD_SIZE;
	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);

	spin_lock(&mm->page_table_lock);
993 994 995
	if (unlikely(!pmd_same(*pmd, orig_pmd)))
		goto out_free_page;

996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019
	pmdp_clear_flush(vma, haddr, pmd);
	/* leave pmd empty until pte is filled */

	pgtable = pgtable_trans_huge_withdraw(mm);
	pmd_populate(mm, &_pmd, pgtable);

	for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
		pte_t *pte, entry;
		if (haddr == (address & PAGE_MASK)) {
			entry = mk_pte(page, vma->vm_page_prot);
			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
			page_add_new_anon_rmap(page, vma, haddr);
		} else {
			entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
			entry = pte_mkspecial(entry);
		}
		pte = pte_offset_map(&_pmd, haddr);
		VM_BUG_ON(!pte_none(*pte));
		set_pte_at(mm, haddr, pte, entry);
		pte_unmap(pte);
	}
	smp_wmb(); /* make pte visible before pmd */
	pmd_populate(mm, pmd, pgtable);
	spin_unlock(&mm->page_table_lock);
1020
	put_huge_zero_page();
1021 1022 1023 1024 1025 1026 1027
	inc_mm_counter(mm, MM_ANONPAGES);

	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);

	ret |= VM_FAULT_WRITE;
out:
	return ret;
1028 1029 1030 1031 1032 1033
out_free_page:
	spin_unlock(&mm->page_table_lock);
	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
	mem_cgroup_uncharge_page(page);
	put_page(page);
	goto out;
1034 1035
}

1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046
static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
					struct vm_area_struct *vma,
					unsigned long address,
					pmd_t *pmd, pmd_t orig_pmd,
					struct page *page,
					unsigned long haddr)
{
	pgtable_t pgtable;
	pmd_t _pmd;
	int ret = 0, i;
	struct page **pages;
1047 1048
	unsigned long mmun_start;	/* For mmu_notifiers */
	unsigned long mmun_end;		/* For mmu_notifiers */
1049 1050 1051 1052 1053 1054 1055 1056 1057

	pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
			GFP_KERNEL);
	if (unlikely(!pages)) {
		ret |= VM_FAULT_OOM;
		goto out;
	}

	for (i = 0; i < HPAGE_PMD_NR; i++) {
1058 1059
		pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
					       __GFP_OTHER_NODE,
1060
					       vma, address, page_to_nid(page));
A
Andrea Arcangeli 已提交
1061 1062 1063 1064
		if (unlikely(!pages[i] ||
			     mem_cgroup_newpage_charge(pages[i], mm,
						       GFP_KERNEL))) {
			if (pages[i])
1065
				put_page(pages[i]);
A
Andrea Arcangeli 已提交
1066 1067 1068 1069 1070 1071
			mem_cgroup_uncharge_start();
			while (--i >= 0) {
				mem_cgroup_uncharge_page(pages[i]);
				put_page(pages[i]);
			}
			mem_cgroup_uncharge_end();
1072 1073 1074 1075 1076 1077 1078 1079
			kfree(pages);
			ret |= VM_FAULT_OOM;
			goto out;
		}
	}

	for (i = 0; i < HPAGE_PMD_NR; i++) {
		copy_user_highpage(pages[i], page + i,
1080
				   haddr + PAGE_SIZE * i, vma);
1081 1082 1083 1084
		__SetPageUptodate(pages[i]);
		cond_resched();
	}

1085 1086 1087 1088
	mmun_start = haddr;
	mmun_end   = haddr + HPAGE_PMD_SIZE;
	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);

1089 1090 1091 1092 1093
	spin_lock(&mm->page_table_lock);
	if (unlikely(!pmd_same(*pmd, orig_pmd)))
		goto out_free_pages;
	VM_BUG_ON(!PageHead(page));

1094
	pmdp_clear_flush(vma, haddr, pmd);
1095 1096
	/* leave pmd empty until pte is filled */

1097
	pgtable = pgtable_trans_huge_withdraw(mm);
1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116
	pmd_populate(mm, &_pmd, pgtable);

	for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
		pte_t *pte, entry;
		entry = mk_pte(pages[i], vma->vm_page_prot);
		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
		page_add_new_anon_rmap(pages[i], vma, haddr);
		pte = pte_offset_map(&_pmd, haddr);
		VM_BUG_ON(!pte_none(*pte));
		set_pte_at(mm, haddr, pte, entry);
		pte_unmap(pte);
	}
	kfree(pages);

	smp_wmb(); /* make pte visible before pmd */
	pmd_populate(mm, pmd, pgtable);
	page_remove_rmap(page);
	spin_unlock(&mm->page_table_lock);

1117 1118
	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);

1119 1120 1121 1122 1123 1124 1125 1126
	ret |= VM_FAULT_WRITE;
	put_page(page);

out:
	return ret;

out_free_pages:
	spin_unlock(&mm->page_table_lock);
1127
	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
A
Andrea Arcangeli 已提交
1128 1129 1130
	mem_cgroup_uncharge_start();
	for (i = 0; i < HPAGE_PMD_NR; i++) {
		mem_cgroup_uncharge_page(pages[i]);
1131
		put_page(pages[i]);
A
Andrea Arcangeli 已提交
1132 1133
	}
	mem_cgroup_uncharge_end();
1134 1135 1136 1137 1138 1139 1140 1141
	kfree(pages);
	goto out;
}

int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
			unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
{
	int ret = 0;
1142
	struct page *page = NULL, *new_page;
1143
	unsigned long haddr;
1144 1145
	unsigned long mmun_start;	/* For mmu_notifiers */
	unsigned long mmun_end;		/* For mmu_notifiers */
1146 1147

	VM_BUG_ON(!vma->anon_vma);
1148 1149 1150
	haddr = address & HPAGE_PMD_MASK;
	if (is_huge_zero_pmd(orig_pmd))
		goto alloc;
1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161
	spin_lock(&mm->page_table_lock);
	if (unlikely(!pmd_same(*pmd, orig_pmd)))
		goto out_unlock;

	page = pmd_page(orig_pmd);
	VM_BUG_ON(!PageCompound(page) || !PageHead(page));
	if (page_mapcount(page) == 1) {
		pmd_t entry;
		entry = pmd_mkyoung(orig_pmd);
		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
		if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
1162
			update_mmu_cache_pmd(vma, address, pmd);
1163 1164 1165 1166 1167
		ret |= VM_FAULT_WRITE;
		goto out_unlock;
	}
	get_page(page);
	spin_unlock(&mm->page_table_lock);
1168
alloc:
1169 1170
	if (transparent_hugepage_enabled(vma) &&
	    !transparent_hugepage_debug_cow())
1171
		new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
1172
					      vma, haddr, numa_node_id(), 0);
1173 1174 1175 1176
	else
		new_page = NULL;

	if (unlikely(!new_page)) {
1177
		count_vm_event(THP_FAULT_FALLBACK);
1178 1179
		if (is_huge_zero_pmd(orig_pmd)) {
			ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
1180
					address, pmd, orig_pmd, haddr);
1181 1182 1183 1184 1185 1186 1187
		} else {
			ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
					pmd, orig_pmd, page, haddr);
			if (ret & VM_FAULT_OOM)
				split_huge_page(page);
			put_page(page);
		}
1188 1189
		goto out;
	}
1190
	count_vm_event(THP_FAULT_ALLOC);
1191

A
Andrea Arcangeli 已提交
1192 1193
	if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
		put_page(new_page);
1194 1195 1196 1197
		if (page) {
			split_huge_page(page);
			put_page(page);
		}
A
Andrea Arcangeli 已提交
1198 1199 1200 1201
		ret |= VM_FAULT_OOM;
		goto out;
	}

1202 1203 1204 1205
	if (is_huge_zero_pmd(orig_pmd))
		clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
	else
		copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1206 1207
	__SetPageUptodate(new_page);

1208 1209 1210 1211
	mmun_start = haddr;
	mmun_end   = haddr + HPAGE_PMD_SIZE;
	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);

1212
	spin_lock(&mm->page_table_lock);
1213 1214
	if (page)
		put_page(page);
A
Andrea Arcangeli 已提交
1215
	if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1216
		spin_unlock(&mm->page_table_lock);
A
Andrea Arcangeli 已提交
1217
		mem_cgroup_uncharge_page(new_page);
1218
		put_page(new_page);
1219
		goto out_mn;
A
Andrea Arcangeli 已提交
1220
	} else {
1221
		pmd_t entry;
B
Bob Liu 已提交
1222
		entry = mk_huge_pmd(new_page, vma);
1223
		pmdp_clear_flush(vma, haddr, pmd);
1224 1225
		page_add_new_anon_rmap(new_page, vma, haddr);
		set_pmd_at(mm, haddr, pmd, entry);
1226
		update_mmu_cache_pmd(vma, address, pmd);
1227
		if (is_huge_zero_pmd(orig_pmd)) {
1228
			add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1229 1230
			put_huge_zero_page();
		} else {
1231 1232 1233 1234
			VM_BUG_ON(!PageHead(page));
			page_remove_rmap(page);
			put_page(page);
		}
1235 1236 1237
		ret |= VM_FAULT_WRITE;
	}
	spin_unlock(&mm->page_table_lock);
1238 1239
out_mn:
	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1240 1241
out:
	return ret;
1242 1243 1244
out_unlock:
	spin_unlock(&mm->page_table_lock);
	return ret;
1245 1246
}

1247
struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1248 1249 1250 1251
				   unsigned long addr,
				   pmd_t *pmd,
				   unsigned int flags)
{
1252
	struct mm_struct *mm = vma->vm_mm;
1253 1254 1255 1256 1257 1258 1259
	struct page *page = NULL;

	assert_spin_locked(&mm->page_table_lock);

	if (flags & FOLL_WRITE && !pmd_write(*pmd))
		goto out;

1260 1261 1262 1263
	/* Avoid dumping huge zero page */
	if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
		return ERR_PTR(-EFAULT);

1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278
	page = pmd_page(*pmd);
	VM_BUG_ON(!PageHead(page));
	if (flags & FOLL_TOUCH) {
		pmd_t _pmd;
		/*
		 * We should set the dirty bit only for FOLL_WRITE but
		 * for now the dirty bit in the pmd is meaningless.
		 * And if the dirty bit will become meaningful and
		 * we'll only set it with FOLL_WRITE, an atomic
		 * set_bit will be required on the pmd to set the
		 * young bit, instead of the current set_pmd_at.
		 */
		_pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
		set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
	}
1279 1280 1281 1282 1283 1284 1285 1286
	if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
		if (page->mapping && trylock_page(page)) {
			lru_add_drain();
			if (page->mapping)
				mlock_vma_page(page);
			unlock_page(page);
		}
	}
1287 1288 1289
	page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
	VM_BUG_ON(!PageCompound(page));
	if (flags & FOLL_GET)
1290
		get_page_foll(page);
1291 1292 1293 1294 1295

out:
	return page;
}

1296
/* NUMA hinting page fault entry point for trans huge pmds */
1297 1298
int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
				unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1299
{
1300
	struct page *page;
1301
	unsigned long haddr = addr & HPAGE_PMD_MASK;
1302
	int target_nid;
1303
	int current_nid = -1;
1304 1305
	bool migrated;
	bool page_locked = false;
1306 1307 1308 1309 1310 1311

	spin_lock(&mm->page_table_lock);
	if (unlikely(!pmd_same(pmd, *pmdp)))
		goto out_unlock;

	page = pmd_page(pmd);
1312
	get_page(page);
1313 1314 1315 1316
	current_nid = page_to_nid(page);
	count_vm_numa_event(NUMA_HINT_FAULTS);
	if (current_nid == numa_node_id())
		count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1317 1318

	target_nid = mpol_misplaced(page, vma, haddr);
1319 1320
	if (target_nid == -1) {
		put_page(page);
1321
		goto clear_pmdnuma;
1322
	}
1323

1324 1325 1326 1327
	/* Acquire the page lock to serialise THP migrations */
	spin_unlock(&mm->page_table_lock);
	lock_page(page);
	page_locked = true;
1328

1329
	/* Confirm the PTE did not while locked */
1330
	spin_lock(&mm->page_table_lock);
1331 1332 1333
	if (unlikely(!pmd_same(pmd, *pmdp))) {
		unlock_page(page);
		put_page(page);
1334
		goto out_unlock;
1335 1336
	}
	spin_unlock(&mm->page_table_lock);
1337

1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356
	/* Migrate the THP to the requested node */
	migrated = migrate_misplaced_transhuge_page(mm, vma,
				pmdp, pmd, addr,
				page, target_nid);
	if (migrated)
		current_nid = target_nid;
	else {
		spin_lock(&mm->page_table_lock);
		if (unlikely(!pmd_same(pmd, *pmdp))) {
			unlock_page(page);
			goto out_unlock;
		}
		goto clear_pmdnuma;
	}

	task_numa_fault(current_nid, HPAGE_PMD_NR, migrated);
	return 0;

clear_pmdnuma:
1357 1358 1359 1360
	pmd = pmd_mknonnuma(pmd);
	set_pmd_at(mm, haddr, pmdp, pmd);
	VM_BUG_ON(pmd_numa(*pmdp));
	update_mmu_cache_pmd(vma, addr, pmdp);
1361 1362
	if (page_locked)
		unlock_page(page);
1363 1364 1365

out_unlock:
	spin_unlock(&mm->page_table_lock);
1366 1367
	if (current_nid != -1)
		task_numa_fault(current_nid, HPAGE_PMD_NR, migrated);
1368 1369 1370
	return 0;
}

1371
int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
S
Shaohua Li 已提交
1372
		 pmd_t *pmd, unsigned long addr)
1373 1374 1375
{
	int ret = 0;

1376 1377 1378
	if (__pmd_trans_huge_lock(pmd, vma) == 1) {
		struct page *page;
		pgtable_t pgtable;
1379
		pmd_t orig_pmd;
1380
		pgtable = pgtable_trans_huge_withdraw(tlb->mm);
1381
		orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1382
		tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1383 1384 1385
		if (is_huge_zero_pmd(orig_pmd)) {
			tlb->mm->nr_ptes--;
			spin_unlock(&tlb->mm->page_table_lock);
1386
			put_huge_zero_page();
1387 1388 1389 1390 1391 1392 1393 1394 1395 1396
		} else {
			page = pmd_page(orig_pmd);
			page_remove_rmap(page);
			VM_BUG_ON(page_mapcount(page) < 0);
			add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
			VM_BUG_ON(!PageHead(page));
			tlb->mm->nr_ptes--;
			spin_unlock(&tlb->mm->page_table_lock);
			tlb_remove_page(tlb, page);
		}
1397 1398 1399
		pte_free(tlb->mm, pgtable);
		ret = 1;
	}
1400 1401 1402
	return ret;
}

1403 1404 1405 1406 1407 1408
int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
		unsigned long addr, unsigned long end,
		unsigned char *vec)
{
	int ret = 0;

1409 1410 1411 1412 1413
	if (__pmd_trans_huge_lock(pmd, vma) == 1) {
		/*
		 * All logical pages in the range are present
		 * if backed by a huge page.
		 */
1414
		spin_unlock(&vma->vm_mm->page_table_lock);
1415 1416 1417
		memset(vec, 1, (end - addr) >> PAGE_SHIFT);
		ret = 1;
	}
1418 1419 1420 1421

	return ret;
}

1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446
int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
		  unsigned long old_addr,
		  unsigned long new_addr, unsigned long old_end,
		  pmd_t *old_pmd, pmd_t *new_pmd)
{
	int ret = 0;
	pmd_t pmd;

	struct mm_struct *mm = vma->vm_mm;

	if ((old_addr & ~HPAGE_PMD_MASK) ||
	    (new_addr & ~HPAGE_PMD_MASK) ||
	    old_end - old_addr < HPAGE_PMD_SIZE ||
	    (new_vma->vm_flags & VM_NOHUGEPAGE))
		goto out;

	/*
	 * 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));
		goto out;
	}

1447 1448 1449 1450 1451
	ret = __pmd_trans_huge_lock(old_pmd, vma);
	if (ret == 1) {
		pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
		VM_BUG_ON(!pmd_none(*new_pmd));
		set_pmd_at(mm, new_addr, new_pmd, pmd);
1452 1453 1454 1455 1456 1457
		spin_unlock(&mm->page_table_lock);
	}
out:
	return ret;
}

1458
int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1459
		unsigned long addr, pgprot_t newprot, int prot_numa)
1460 1461 1462 1463
{
	struct mm_struct *mm = vma->vm_mm;
	int ret = 0;

1464 1465 1466
	if (__pmd_trans_huge_lock(pmd, vma) == 1) {
		pmd_t entry;
		entry = pmdp_get_and_clear(mm, addr, pmd);
1467
		if (!prot_numa) {
1468
			entry = pmd_modify(entry, newprot);
1469 1470
			BUG_ON(pmd_write(entry));
		} else {
1471 1472 1473 1474 1475 1476 1477 1478
			struct page *page = pmd_page(*pmd);

			/* only check non-shared pages */
			if (page_mapcount(page) == 1 &&
			    !pmd_numa(*pmd)) {
				entry = pmd_mknuma(entry);
			}
		}
1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496
		set_pmd_at(mm, addr, pmd, entry);
		spin_unlock(&vma->vm_mm->page_table_lock);
		ret = 1;
	}

	return ret;
}

/*
 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
 *
 * Note that if it returns 1, this routine returns without unlocking page
 * table locks. So callers must unlock them.
 */
int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
{
	spin_lock(&vma->vm_mm->page_table_lock);
1497 1498
	if (likely(pmd_trans_huge(*pmd))) {
		if (unlikely(pmd_trans_splitting(*pmd))) {
1499
			spin_unlock(&vma->vm_mm->page_table_lock);
1500
			wait_split_huge_page(vma->anon_vma, pmd);
1501
			return -1;
1502
		} else {
1503 1504 1505
			/* Thp mapped by 'pmd' is stable, so we can
			 * handle it as it is. */
			return 1;
1506
		}
1507 1508 1509
	}
	spin_unlock(&vma->vm_mm->page_table_lock);
	return 0;
1510 1511
}

1512 1513 1514 1515 1516 1517 1518 1519 1520 1521
pmd_t *page_check_address_pmd(struct page *page,
			      struct mm_struct *mm,
			      unsigned long address,
			      enum page_check_address_pmd_flag flag)
{
	pmd_t *pmd, *ret = NULL;

	if (address & ~HPAGE_PMD_MASK)
		goto out;

B
Bob Liu 已提交
1522 1523
	pmd = mm_find_pmd(mm, address);
	if (!pmd)
1524 1525 1526 1527 1528
		goto out;
	if (pmd_none(*pmd))
		goto out;
	if (pmd_page(*pmd) != page)
		goto out;
1529 1530 1531 1532 1533 1534 1535 1536 1537 1538
	/*
	 * split_vma() may create temporary aliased mappings. There is
	 * no risk as long as all huge pmd are found and have their
	 * splitting bit set before __split_huge_page_refcount
	 * runs. Finding the same huge pmd more than once during the
	 * same rmap walk is not a problem.
	 */
	if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
	    pmd_trans_splitting(*pmd))
		goto out;
1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554
	if (pmd_trans_huge(*pmd)) {
		VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
			  !pmd_trans_splitting(*pmd));
		ret = pmd;
	}
out:
	return ret;
}

static int __split_huge_page_splitting(struct page *page,
				       struct vm_area_struct *vma,
				       unsigned long address)
{
	struct mm_struct *mm = vma->vm_mm;
	pmd_t *pmd;
	int ret = 0;
1555 1556 1557
	/* For mmu_notifiers */
	const unsigned long mmun_start = address;
	const unsigned long mmun_end   = address + HPAGE_PMD_SIZE;
1558

1559
	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1560 1561 1562 1563 1564 1565 1566 1567
	spin_lock(&mm->page_table_lock);
	pmd = page_check_address_pmd(page, mm, address,
				     PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
	if (pmd) {
		/*
		 * We can't temporarily set the pmd to null in order
		 * to split it, the pmd must remain marked huge at all
		 * times or the VM won't take the pmd_trans_huge paths
1568
		 * and it won't wait on the anon_vma->root->rwsem to
1569 1570
		 * serialize against split_huge_page*.
		 */
1571
		pmdp_splitting_flush(vma, address, pmd);
1572 1573 1574
		ret = 1;
	}
	spin_unlock(&mm->page_table_lock);
1575
	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1576 1577 1578 1579 1580 1581 1582 1583

	return ret;
}

static void __split_huge_page_refcount(struct page *page)
{
	int i;
	struct zone *zone = page_zone(page);
1584
	struct lruvec *lruvec;
1585
	int tail_count = 0;
1586 1587 1588

	/* prevent PageLRU to go away from under us, and freeze lru stats */
	spin_lock_irq(&zone->lru_lock);
1589 1590
	lruvec = mem_cgroup_page_lruvec(page, zone);

1591
	compound_lock(page);
1592 1593
	/* complete memcg works before add pages to LRU */
	mem_cgroup_split_huge_fixup(page);
1594

1595
	for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1596 1597
		struct page *page_tail = page + i;

1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618
		/* tail_page->_mapcount cannot change */
		BUG_ON(page_mapcount(page_tail) < 0);
		tail_count += page_mapcount(page_tail);
		/* check for overflow */
		BUG_ON(tail_count < 0);
		BUG_ON(atomic_read(&page_tail->_count) != 0);
		/*
		 * tail_page->_count is zero and not changing from
		 * under us. But get_page_unless_zero() may be running
		 * from under us on the tail_page. If we used
		 * atomic_set() below instead of atomic_add(), we
		 * would then run atomic_set() concurrently with
		 * get_page_unless_zero(), and atomic_set() is
		 * implemented in C not using locked ops. spin_unlock
		 * on x86 sometime uses locked ops because of PPro
		 * errata 66, 92, so unless somebody can guarantee
		 * atomic_set() here would be safe on all archs (and
		 * not only on x86), it's safer to use atomic_add().
		 */
		atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
			   &page_tail->_count);
1619 1620 1621 1622

		/* after clearing PageTail the gup refcount can be released */
		smp_mb();

1623 1624 1625 1626 1627 1628
		/*
		 * retain hwpoison flag of the poisoned tail page:
		 *   fix for the unsuitable process killed on Guest Machine(KVM)
		 *   by the memory-failure.
		 */
		page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1629 1630 1631 1632 1633 1634 1635
		page_tail->flags |= (page->flags &
				     ((1L << PG_referenced) |
				      (1L << PG_swapbacked) |
				      (1L << PG_mlocked) |
				      (1L << PG_uptodate)));
		page_tail->flags |= (1L << PG_dirty);

1636
		/* clear PageTail before overwriting first_page */
1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657
		smp_wmb();

		/*
		 * __split_huge_page_splitting() already set the
		 * splitting bit in all pmd that could map this
		 * hugepage, that will ensure no CPU can alter the
		 * mapcount on the head page. The mapcount is only
		 * accounted in the head page and it has to be
		 * transferred to all tail pages in the below code. So
		 * for this code to be safe, the split the mapcount
		 * can't change. But that doesn't mean userland can't
		 * keep changing and reading the page contents while
		 * we transfer the mapcount, so the pmd splitting
		 * status is achieved setting a reserved bit in the
		 * pmd, not by clearing the present bit.
		*/
		page_tail->_mapcount = page->_mapcount;

		BUG_ON(page_tail->mapping);
		page_tail->mapping = page->mapping;

1658
		page_tail->index = page->index + i;
1659
		page_xchg_last_nid(page_tail, page_last_nid(page));
1660 1661 1662 1663 1664 1665

		BUG_ON(!PageAnon(page_tail));
		BUG_ON(!PageUptodate(page_tail));
		BUG_ON(!PageDirty(page_tail));
		BUG_ON(!PageSwapBacked(page_tail));

1666
		lru_add_page_tail(page, page_tail, lruvec);
1667
	}
1668 1669
	atomic_sub(tail_count, &page->_count);
	BUG_ON(atomic_read(&page->_count) <= 0);
1670

1671
	__mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1672 1673
	__mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);

1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711
	ClearPageCompound(page);
	compound_unlock(page);
	spin_unlock_irq(&zone->lru_lock);

	for (i = 1; i < HPAGE_PMD_NR; i++) {
		struct page *page_tail = page + i;
		BUG_ON(page_count(page_tail) <= 0);
		/*
		 * Tail pages may be freed if there wasn't any mapping
		 * like if add_to_swap() is running on a lru page that
		 * had its mapping zapped. And freeing these pages
		 * requires taking the lru_lock so we do the put_page
		 * of the tail pages after the split is complete.
		 */
		put_page(page_tail);
	}

	/*
	 * Only the head page (now become a regular page) is required
	 * to be pinned by the caller.
	 */
	BUG_ON(page_count(page) <= 0);
}

static int __split_huge_page_map(struct page *page,
				 struct vm_area_struct *vma,
				 unsigned long address)
{
	struct mm_struct *mm = vma->vm_mm;
	pmd_t *pmd, _pmd;
	int ret = 0, i;
	pgtable_t pgtable;
	unsigned long haddr;

	spin_lock(&mm->page_table_lock);
	pmd = page_check_address_pmd(page, mm, address,
				     PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
	if (pmd) {
1712
		pgtable = pgtable_trans_huge_withdraw(mm);
1713 1714
		pmd_populate(mm, &_pmd, pgtable);

1715 1716
		haddr = address;
		for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1717 1718 1719 1720 1721 1722 1723 1724 1725 1726
			pte_t *pte, entry;
			BUG_ON(PageCompound(page+i));
			entry = mk_pte(page + i, vma->vm_page_prot);
			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
			if (!pmd_write(*pmd))
				entry = pte_wrprotect(entry);
			else
				BUG_ON(page_mapcount(page) != 1);
			if (!pmd_young(*pmd))
				entry = pte_mkold(entry);
1727 1728
			if (pmd_numa(*pmd))
				entry = pte_mknuma(entry);
1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761
			pte = pte_offset_map(&_pmd, haddr);
			BUG_ON(!pte_none(*pte));
			set_pte_at(mm, haddr, pte, entry);
			pte_unmap(pte);
		}

		smp_wmb(); /* make pte visible before pmd */
		/*
		 * Up to this point the pmd is present and huge and
		 * userland has the whole access to the hugepage
		 * during the split (which happens in place). If we
		 * overwrite the pmd with the not-huge version
		 * pointing to the pte here (which of course we could
		 * if all CPUs were bug free), userland could trigger
		 * a small page size TLB miss on the small sized TLB
		 * while the hugepage TLB entry is still established
		 * in the huge TLB. Some CPU doesn't like that. See
		 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
		 * Erratum 383 on page 93. Intel should be safe but is
		 * also warns that it's only safe if the permission
		 * and cache attributes of the two entries loaded in
		 * the two TLB is identical (which should be the case
		 * here). But it is generally safer to never allow
		 * small and huge TLB entries for the same virtual
		 * address to be loaded simultaneously. So instead of
		 * doing "pmd_populate(); flush_tlb_range();" we first
		 * mark the current pmd notpresent (atomically because
		 * here the pmd_trans_huge and pmd_trans_splitting
		 * must remain set at all times on the pmd until the
		 * split is complete for this pmd), then we flush the
		 * SMP TLB and finally we write the non-huge version
		 * of the pmd entry with pmd_populate.
		 */
G
Gerald Schaefer 已提交
1762
		pmdp_invalidate(vma, address, pmd);
1763 1764 1765 1766 1767 1768 1769 1770
		pmd_populate(mm, pmd, pgtable);
		ret = 1;
	}
	spin_unlock(&mm->page_table_lock);

	return ret;
}

1771
/* must be called with anon_vma->root->rwsem held */
1772 1773 1774 1775
static void __split_huge_page(struct page *page,
			      struct anon_vma *anon_vma)
{
	int mapcount, mapcount2;
1776
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1777 1778 1779 1780 1781 1782
	struct anon_vma_chain *avc;

	BUG_ON(!PageHead(page));
	BUG_ON(PageTail(page));

	mapcount = 0;
1783
	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1784 1785 1786 1787 1788
		struct vm_area_struct *vma = avc->vma;
		unsigned long addr = vma_address(page, vma);
		BUG_ON(is_vma_temporary_stack(vma));
		mapcount += __split_huge_page_splitting(page, vma, addr);
	}
1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801
	/*
	 * It is critical that new vmas are added to the tail of the
	 * anon_vma list. This guarantes that if copy_huge_pmd() runs
	 * and establishes a child pmd before
	 * __split_huge_page_splitting() freezes the parent pmd (so if
	 * we fail to prevent copy_huge_pmd() from running until the
	 * whole __split_huge_page() is complete), we will still see
	 * the newly established pmd of the child later during the
	 * walk, to be able to set it as pmd_trans_splitting too.
	 */
	if (mapcount != page_mapcount(page))
		printk(KERN_ERR "mapcount %d page_mapcount %d\n",
		       mapcount, page_mapcount(page));
1802 1803 1804 1805 1806
	BUG_ON(mapcount != page_mapcount(page));

	__split_huge_page_refcount(page);

	mapcount2 = 0;
1807
	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1808 1809 1810 1811 1812
		struct vm_area_struct *vma = avc->vma;
		unsigned long addr = vma_address(page, vma);
		BUG_ON(is_vma_temporary_stack(vma));
		mapcount2 += __split_huge_page_map(page, vma, addr);
	}
1813 1814 1815
	if (mapcount != mapcount2)
		printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
		       mapcount, mapcount2, page_mapcount(page));
1816 1817 1818 1819 1820 1821 1822 1823
	BUG_ON(mapcount != mapcount2);
}

int split_huge_page(struct page *page)
{
	struct anon_vma *anon_vma;
	int ret = 1;

1824
	BUG_ON(is_huge_zero_pfn(page_to_pfn(page)));
1825
	BUG_ON(!PageAnon(page));
1826 1827 1828 1829 1830 1831 1832 1833 1834

	/*
	 * The caller does not necessarily hold an mmap_sem that would prevent
	 * the anon_vma disappearing so we first we take a reference to it
	 * and then lock the anon_vma for write. This is similar to
	 * page_lock_anon_vma_read except the write lock is taken to serialise
	 * against parallel split or collapse operations.
	 */
	anon_vma = page_get_anon_vma(page);
1835 1836
	if (!anon_vma)
		goto out;
1837 1838
	anon_vma_lock_write(anon_vma);

1839 1840 1841 1842 1843 1844
	ret = 0;
	if (!PageCompound(page))
		goto out_unlock;

	BUG_ON(!PageSwapBacked(page));
	__split_huge_page(page, anon_vma);
1845
	count_vm_event(THP_SPLIT);
1846 1847 1848

	BUG_ON(PageCompound(page));
out_unlock:
1849 1850
	anon_vma_unlock(anon_vma);
	put_anon_vma(anon_vma);
1851 1852 1853 1854
out:
	return ret;
}

1855
#define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1856

1857 1858
int hugepage_madvise(struct vm_area_struct *vma,
		     unsigned long *vm_flags, int advice)
A
Andrea Arcangeli 已提交
1859
{
1860 1861
	struct mm_struct *mm = vma->vm_mm;

A
Andrea Arcangeli 已提交
1862 1863 1864 1865 1866
	switch (advice) {
	case MADV_HUGEPAGE:
		/*
		 * Be somewhat over-protective like KSM for now!
		 */
1867
		if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
A
Andrea Arcangeli 已提交
1868
			return -EINVAL;
1869 1870
		if (mm->def_flags & VM_NOHUGEPAGE)
			return -EINVAL;
A
Andrea Arcangeli 已提交
1871 1872
		*vm_flags &= ~VM_NOHUGEPAGE;
		*vm_flags |= VM_HUGEPAGE;
1873 1874 1875 1876 1877 1878 1879
		/*
		 * If the vma become good for khugepaged to scan,
		 * register it here without waiting a page fault that
		 * may not happen any time soon.
		 */
		if (unlikely(khugepaged_enter_vma_merge(vma)))
			return -ENOMEM;
A
Andrea Arcangeli 已提交
1880 1881 1882 1883 1884
		break;
	case MADV_NOHUGEPAGE:
		/*
		 * Be somewhat over-protective like KSM for now!
		 */
1885
		if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
A
Andrea Arcangeli 已提交
1886 1887 1888
			return -EINVAL;
		*vm_flags &= ~VM_HUGEPAGE;
		*vm_flags |= VM_NOHUGEPAGE;
1889 1890 1891 1892 1893
		/*
		 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
		 * this vma even if we leave the mm registered in khugepaged if
		 * it got registered before VM_NOHUGEPAGE was set.
		 */
A
Andrea Arcangeli 已提交
1894 1895
		break;
	}
A
Andrea Arcangeli 已提交
1896 1897 1898 1899

	return 0;
}

A
Andrea Arcangeli 已提交
1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
static int __init khugepaged_slab_init(void)
{
	mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
					  sizeof(struct mm_slot),
					  __alignof__(struct mm_slot), 0, NULL);
	if (!mm_slot_cache)
		return -ENOMEM;

	return 0;
}

static void __init khugepaged_slab_free(void)
{
	kmem_cache_destroy(mm_slot_cache);
	mm_slot_cache = NULL;
}

static inline struct mm_slot *alloc_mm_slot(void)
{
	if (!mm_slot_cache)	/* initialization failed */
		return NULL;
	return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
}

static inline void free_mm_slot(struct mm_slot *mm_slot)
{
	kmem_cache_free(mm_slot_cache, mm_slot);
}

static int __init mm_slots_hash_init(void)
{
	mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
				GFP_KERNEL);
	if (!mm_slots_hash)
		return -ENOMEM;
	return 0;
}

#if 0
static void __init mm_slots_hash_free(void)
{
	kfree(mm_slots_hash);
	mm_slots_hash = NULL;
}
#endif

static struct mm_slot *get_mm_slot(struct mm_struct *mm)
{
	struct mm_slot *mm_slot;
	struct hlist_head *bucket;
	struct hlist_node *node;

	bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
				% MM_SLOTS_HASH_HEADS];
	hlist_for_each_entry(mm_slot, node, bucket, hash) {
		if (mm == mm_slot->mm)
			return mm_slot;
	}
	return NULL;
}

static void insert_to_mm_slots_hash(struct mm_struct *mm,
				    struct mm_slot *mm_slot)
{
	struct hlist_head *bucket;

	bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
				% MM_SLOTS_HASH_HEADS];
	mm_slot->mm = mm;
	hlist_add_head(&mm_slot->hash, bucket);
}

static inline int khugepaged_test_exit(struct mm_struct *mm)
{
	return atomic_read(&mm->mm_users) == 0;
}

int __khugepaged_enter(struct mm_struct *mm)
{
	struct mm_slot *mm_slot;
	int wakeup;

	mm_slot = alloc_mm_slot();
	if (!mm_slot)
		return -ENOMEM;

	/* __khugepaged_exit() must not run from under us */
	VM_BUG_ON(khugepaged_test_exit(mm));
	if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
		free_mm_slot(mm_slot);
		return 0;
	}

	spin_lock(&khugepaged_mm_lock);
	insert_to_mm_slots_hash(mm, mm_slot);
	/*
	 * Insert just behind the scanning cursor, to let the area settle
	 * down a little.
	 */
	wakeup = list_empty(&khugepaged_scan.mm_head);
	list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
	spin_unlock(&khugepaged_mm_lock);

	atomic_inc(&mm->mm_count);
	if (wakeup)
		wake_up_interruptible(&khugepaged_wait);

	return 0;
}

int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
{
	unsigned long hstart, hend;
	if (!vma->anon_vma)
		/*
		 * Not yet faulted in so we will register later in the
		 * page fault if needed.
		 */
		return 0;
2019
	if (vma->vm_ops)
A
Andrea Arcangeli 已提交
2020 2021
		/* khugepaged not yet working on file or special mappings */
		return 0;
2022
	VM_BUG_ON(vma->vm_flags & VM_NO_THP);
A
Andrea Arcangeli 已提交
2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041
	hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
	hend = vma->vm_end & HPAGE_PMD_MASK;
	if (hstart < hend)
		return khugepaged_enter(vma);
	return 0;
}

void __khugepaged_exit(struct mm_struct *mm)
{
	struct mm_slot *mm_slot;
	int free = 0;

	spin_lock(&khugepaged_mm_lock);
	mm_slot = get_mm_slot(mm);
	if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
		hlist_del(&mm_slot->hash);
		list_del(&mm_slot->mm_node);
		free = 1;
	}
2042
	spin_unlock(&khugepaged_mm_lock);
A
Andrea Arcangeli 已提交
2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058

	if (free) {
		clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
		free_mm_slot(mm_slot);
		mmdrop(mm);
	} else if (mm_slot) {
		/*
		 * This is required to serialize against
		 * khugepaged_test_exit() (which is guaranteed to run
		 * under mmap sem read mode). Stop here (after we
		 * return all pagetables will be destroyed) until
		 * khugepaged has finished working on the pagetables
		 * under the mmap_sem.
		 */
		down_write(&mm->mmap_sem);
		up_write(&mm->mmap_sem);
2059
	}
A
Andrea Arcangeli 已提交
2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084
}

static void release_pte_page(struct page *page)
{
	/* 0 stands for page_is_file_cache(page) == false */
	dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
	unlock_page(page);
	putback_lru_page(page);
}

static void release_pte_pages(pte_t *pte, pte_t *_pte)
{
	while (--_pte >= pte) {
		pte_t pteval = *_pte;
		if (!pte_none(pteval))
			release_pte_page(pte_page(pteval));
	}
}

static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
					unsigned long address,
					pte_t *pte)
{
	struct page *page;
	pte_t *_pte;
2085
	int referenced = 0, none = 0;
A
Andrea Arcangeli 已提交
2086 2087 2088 2089 2090 2091
	for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
	     _pte++, address += PAGE_SIZE) {
		pte_t pteval = *_pte;
		if (pte_none(pteval)) {
			if (++none <= khugepaged_max_ptes_none)
				continue;
2092
			else
A
Andrea Arcangeli 已提交
2093 2094
				goto out;
		}
2095
		if (!pte_present(pteval) || !pte_write(pteval))
A
Andrea Arcangeli 已提交
2096 2097
			goto out;
		page = vm_normal_page(vma, address, pteval);
2098
		if (unlikely(!page))
A
Andrea Arcangeli 已提交
2099
			goto out;
2100

A
Andrea Arcangeli 已提交
2101 2102 2103 2104 2105
		VM_BUG_ON(PageCompound(page));
		BUG_ON(!PageAnon(page));
		VM_BUG_ON(!PageSwapBacked(page));

		/* cannot use mapcount: can't collapse if there's a gup pin */
2106
		if (page_count(page) != 1)
A
Andrea Arcangeli 已提交
2107 2108 2109 2110 2111 2112 2113
			goto out;
		/*
		 * We can do it before isolate_lru_page because the
		 * page can't be freed from under us. NOTE: PG_lock
		 * is needed to serialize against split_huge_page
		 * when invoked from the VM.
		 */
2114
		if (!trylock_page(page))
A
Andrea Arcangeli 已提交
2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129
			goto out;
		/*
		 * Isolate the page to avoid collapsing an hugepage
		 * currently in use by the VM.
		 */
		if (isolate_lru_page(page)) {
			unlock_page(page);
			goto out;
		}
		/* 0 stands for page_is_file_cache(page) == false */
		inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
		VM_BUG_ON(!PageLocked(page));
		VM_BUG_ON(PageLRU(page));

		/* If there is no mapped pte young don't collapse the page */
A
Andrea Arcangeli 已提交
2130 2131
		if (pte_young(pteval) || PageReferenced(page) ||
		    mmu_notifier_test_young(vma->vm_mm, address))
A
Andrea Arcangeli 已提交
2132 2133
			referenced = 1;
	}
2134 2135
	if (likely(referenced))
		return 1;
A
Andrea Arcangeli 已提交
2136
out:
2137 2138
	release_pte_pages(pte, _pte);
	return 0;
A
Andrea Arcangeli 已提交
2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179
}

static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
				      struct vm_area_struct *vma,
				      unsigned long address,
				      spinlock_t *ptl)
{
	pte_t *_pte;
	for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
		pte_t pteval = *_pte;
		struct page *src_page;

		if (pte_none(pteval)) {
			clear_user_highpage(page, address);
			add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
		} else {
			src_page = pte_page(pteval);
			copy_user_highpage(page, src_page, address, vma);
			VM_BUG_ON(page_mapcount(src_page) != 1);
			release_pte_page(src_page);
			/*
			 * ptl mostly unnecessary, but preempt has to
			 * be disabled to update the per-cpu stats
			 * inside page_remove_rmap().
			 */
			spin_lock(ptl);
			/*
			 * paravirt calls inside pte_clear here are
			 * superfluous.
			 */
			pte_clear(vma->vm_mm, address, _pte);
			page_remove_rmap(src_page);
			spin_unlock(ptl);
			free_page_and_swap_cache(src_page);
		}

		address += PAGE_SIZE;
		page++;
	}
}

2180
static void khugepaged_alloc_sleep(void)
A
Andrea Arcangeli 已提交
2181
{
2182 2183 2184
	wait_event_freezable_timeout(khugepaged_wait, false,
			msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
}
A
Andrea Arcangeli 已提交
2185

2186 2187 2188 2189 2190 2191 2192 2193
#ifdef CONFIG_NUMA
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
{
	if (IS_ERR(*hpage)) {
		if (!*wait)
			return false;

		*wait = false;
2194
		*hpage = NULL;
2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208
		khugepaged_alloc_sleep();
	} else if (*hpage) {
		put_page(*hpage);
		*hpage = NULL;
	}

	return true;
}

static struct page
*khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
		       struct vm_area_struct *vma, unsigned long address,
		       int node)
{
2209
	VM_BUG_ON(*hpage);
2210 2211 2212 2213 2214 2215 2216 2217 2218 2219
	/*
	 * Allocate the page while the vma is still valid and under
	 * the mmap_sem read mode so there is no memory allocation
	 * later when we take the mmap_sem in write mode. This is more
	 * friendly behavior (OTOH it may actually hide bugs) to
	 * filesystems in userland with daemons allocating memory in
	 * the userland I/O paths.  Allocating memory with the
	 * mmap_sem in read mode is good idea also to allow greater
	 * scalability.
	 */
2220
	*hpage  = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
2221
				      node, __GFP_OTHER_NODE);
2222 2223 2224 2225 2226 2227

	/*
	 * After allocating the hugepage, release the mmap_sem read lock in
	 * preparation for taking it in write mode.
	 */
	up_read(&mm->mmap_sem);
2228
	if (unlikely(!*hpage)) {
2229
		count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2230
		*hpage = ERR_PTR(-ENOMEM);
2231
		return NULL;
2232
	}
2233

2234
	count_vm_event(THP_COLLAPSE_ALLOC);
2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277
	return *hpage;
}
#else
static struct page *khugepaged_alloc_hugepage(bool *wait)
{
	struct page *hpage;

	do {
		hpage = alloc_hugepage(khugepaged_defrag());
		if (!hpage) {
			count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
			if (!*wait)
				return NULL;

			*wait = false;
			khugepaged_alloc_sleep();
		} else
			count_vm_event(THP_COLLAPSE_ALLOC);
	} while (unlikely(!hpage) && likely(khugepaged_enabled()));

	return hpage;
}

static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
{
	if (!*hpage)
		*hpage = khugepaged_alloc_hugepage(wait);

	if (unlikely(!*hpage))
		return false;

	return true;
}

static struct page
*khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
		       struct vm_area_struct *vma, unsigned long address,
		       int node)
{
	up_read(&mm->mmap_sem);
	VM_BUG_ON(!*hpage);
	return  *hpage;
}
2278 2279
#endif

B
Bob Liu 已提交
2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293
static bool hugepage_vma_check(struct vm_area_struct *vma)
{
	if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
	    (vma->vm_flags & VM_NOHUGEPAGE))
		return false;

	if (!vma->anon_vma || vma->vm_ops)
		return false;
	if (is_vma_temporary_stack(vma))
		return false;
	VM_BUG_ON(vma->vm_flags & VM_NO_THP);
	return true;
}

2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306
static void collapse_huge_page(struct mm_struct *mm,
				   unsigned long address,
				   struct page **hpage,
				   struct vm_area_struct *vma,
				   int node)
{
	pmd_t *pmd, _pmd;
	pte_t *pte;
	pgtable_t pgtable;
	struct page *new_page;
	spinlock_t *ptl;
	int isolated;
	unsigned long hstart, hend;
2307 2308
	unsigned long mmun_start;	/* For mmu_notifiers */
	unsigned long mmun_end;		/* For mmu_notifiers */
2309 2310 2311 2312 2313 2314 2315 2316

	VM_BUG_ON(address & ~HPAGE_PMD_MASK);

	/* release the mmap_sem read lock. */
	new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
	if (!new_page)
		return;

2317
	if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
2318
		return;
A
Andrea Arcangeli 已提交
2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333

	/*
	 * Prevent all access to pagetables with the exception of
	 * gup_fast later hanlded by the ptep_clear_flush and the VM
	 * handled by the anon_vma lock + PG_lock.
	 */
	down_write(&mm->mmap_sem);
	if (unlikely(khugepaged_test_exit(mm)))
		goto out;

	vma = find_vma(mm, address);
	hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
	hend = vma->vm_end & HPAGE_PMD_MASK;
	if (address < hstart || address + HPAGE_PMD_SIZE > hend)
		goto out;
B
Bob Liu 已提交
2334
	if (!hugepage_vma_check(vma))
2335
		goto out;
B
Bob Liu 已提交
2336 2337
	pmd = mm_find_pmd(mm, address);
	if (!pmd)
A
Andrea Arcangeli 已提交
2338
		goto out;
B
Bob Liu 已提交
2339
	if (pmd_trans_huge(*pmd))
A
Andrea Arcangeli 已提交
2340 2341
		goto out;

2342
	anon_vma_lock_write(vma->anon_vma);
A
Andrea Arcangeli 已提交
2343 2344 2345 2346

	pte = pte_offset_map(pmd, address);
	ptl = pte_lockptr(mm, pmd);

2347 2348 2349
	mmun_start = address;
	mmun_end   = address + HPAGE_PMD_SIZE;
	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
A
Andrea Arcangeli 已提交
2350 2351 2352 2353 2354 2355 2356
	spin_lock(&mm->page_table_lock); /* probably unnecessary */
	/*
	 * After this gup_fast can't run anymore. This also removes
	 * any huge TLB entry from the CPU so we won't allow
	 * huge and small TLB entries for the same virtual address
	 * to avoid the risk of CPU bugs in that area.
	 */
2357
	_pmd = pmdp_clear_flush(vma, address, pmd);
A
Andrea Arcangeli 已提交
2358
	spin_unlock(&mm->page_table_lock);
2359
	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
A
Andrea Arcangeli 已提交
2360 2361 2362 2363 2364 2365

	spin_lock(ptl);
	isolated = __collapse_huge_page_isolate(vma, address, pte);
	spin_unlock(ptl);

	if (unlikely(!isolated)) {
2366
		pte_unmap(pte);
A
Andrea Arcangeli 已提交
2367 2368 2369 2370 2371
		spin_lock(&mm->page_table_lock);
		BUG_ON(!pmd_none(*pmd));
		set_pmd_at(mm, address, pmd, _pmd);
		spin_unlock(&mm->page_table_lock);
		anon_vma_unlock(vma->anon_vma);
2372
		goto out;
A
Andrea Arcangeli 已提交
2373 2374 2375 2376 2377 2378 2379 2380 2381
	}

	/*
	 * All pages are isolated and locked so anon_vma rmap
	 * can't run anymore.
	 */
	anon_vma_unlock(vma->anon_vma);

	__collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2382
	pte_unmap(pte);
A
Andrea Arcangeli 已提交
2383 2384 2385
	__SetPageUptodate(new_page);
	pgtable = pmd_pgtable(_pmd);

B
Bob Liu 已提交
2386
	_pmd = mk_huge_pmd(new_page, vma);
A
Andrea Arcangeli 已提交
2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398

	/*
	 * spin_lock() below is not the equivalent of smp_wmb(), so
	 * this is needed to avoid the copy_huge_page writes to become
	 * visible after the set_pmd_at() write.
	 */
	smp_wmb();

	spin_lock(&mm->page_table_lock);
	BUG_ON(!pmd_none(*pmd));
	page_add_new_anon_rmap(new_page, vma, address);
	set_pmd_at(mm, address, pmd, _pmd);
2399
	update_mmu_cache_pmd(vma, address, pmd);
2400
	pgtable_trans_huge_deposit(mm, pgtable);
A
Andrea Arcangeli 已提交
2401 2402 2403
	spin_unlock(&mm->page_table_lock);

	*hpage = NULL;
2404

A
Andrea Arcangeli 已提交
2405
	khugepaged_pages_collapsed++;
2406
out_up_write:
A
Andrea Arcangeli 已提交
2407
	up_write(&mm->mmap_sem);
2408 2409
	return;

2410
out:
2411
	mem_cgroup_uncharge_page(new_page);
2412
	goto out_up_write;
A
Andrea Arcangeli 已提交
2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425
}

static int khugepaged_scan_pmd(struct mm_struct *mm,
			       struct vm_area_struct *vma,
			       unsigned long address,
			       struct page **hpage)
{
	pmd_t *pmd;
	pte_t *pte, *_pte;
	int ret = 0, referenced = 0, none = 0;
	struct page *page;
	unsigned long _address;
	spinlock_t *ptl;
2426
	int node = -1;
A
Andrea Arcangeli 已提交
2427 2428 2429

	VM_BUG_ON(address & ~HPAGE_PMD_MASK);

B
Bob Liu 已提交
2430 2431
	pmd = mm_find_pmd(mm, address);
	if (!pmd)
A
Andrea Arcangeli 已提交
2432
		goto out;
B
Bob Liu 已提交
2433
	if (pmd_trans_huge(*pmd))
A
Andrea Arcangeli 已提交
2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450
		goto out;

	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
	for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
	     _pte++, _address += PAGE_SIZE) {
		pte_t pteval = *_pte;
		if (pte_none(pteval)) {
			if (++none <= khugepaged_max_ptes_none)
				continue;
			else
				goto out_unmap;
		}
		if (!pte_present(pteval) || !pte_write(pteval))
			goto out_unmap;
		page = vm_normal_page(vma, _address, pteval);
		if (unlikely(!page))
			goto out_unmap;
2451 2452 2453 2454 2455 2456 2457
		/*
		 * Chose the node of the first page. This could
		 * be more sophisticated and look at more pages,
		 * but isn't for now.
		 */
		if (node == -1)
			node = page_to_nid(page);
A
Andrea Arcangeli 已提交
2458 2459 2460 2461 2462 2463
		VM_BUG_ON(PageCompound(page));
		if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
			goto out_unmap;
		/* cannot use mapcount: can't collapse if there's a gup pin */
		if (page_count(page) != 1)
			goto out_unmap;
A
Andrea Arcangeli 已提交
2464 2465
		if (pte_young(pteval) || PageReferenced(page) ||
		    mmu_notifier_test_young(vma->vm_mm, address))
A
Andrea Arcangeli 已提交
2466 2467 2468 2469 2470 2471
			referenced = 1;
	}
	if (referenced)
		ret = 1;
out_unmap:
	pte_unmap_unlock(pte, ptl);
2472 2473
	if (ret)
		/* collapse_huge_page will return with the mmap_sem released */
2474
		collapse_huge_page(mm, address, hpage, vma, node);
A
Andrea Arcangeli 已提交
2475 2476 2477 2478 2479 2480 2481 2482
out:
	return ret;
}

static void collect_mm_slot(struct mm_slot *mm_slot)
{
	struct mm_struct *mm = mm_slot->mm;

2483
	VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
A
Andrea Arcangeli 已提交
2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503

	if (khugepaged_test_exit(mm)) {
		/* free mm_slot */
		hlist_del(&mm_slot->hash);
		list_del(&mm_slot->mm_node);

		/*
		 * Not strictly needed because the mm exited already.
		 *
		 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
		 */

		/* khugepaged_mm_lock actually not necessary for the below */
		free_mm_slot(mm_slot);
		mmdrop(mm);
	}
}

static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
					    struct page **hpage)
2504 2505
	__releases(&khugepaged_mm_lock)
	__acquires(&khugepaged_mm_lock)
A
Andrea Arcangeli 已提交
2506 2507 2508 2509 2510 2511 2512
{
	struct mm_slot *mm_slot;
	struct mm_struct *mm;
	struct vm_area_struct *vma;
	int progress = 0;

	VM_BUG_ON(!pages);
2513
	VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
A
Andrea Arcangeli 已提交
2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540

	if (khugepaged_scan.mm_slot)
		mm_slot = khugepaged_scan.mm_slot;
	else {
		mm_slot = list_entry(khugepaged_scan.mm_head.next,
				     struct mm_slot, mm_node);
		khugepaged_scan.address = 0;
		khugepaged_scan.mm_slot = mm_slot;
	}
	spin_unlock(&khugepaged_mm_lock);

	mm = mm_slot->mm;
	down_read(&mm->mmap_sem);
	if (unlikely(khugepaged_test_exit(mm)))
		vma = NULL;
	else
		vma = find_vma(mm, khugepaged_scan.address);

	progress++;
	for (; vma; vma = vma->vm_next) {
		unsigned long hstart, hend;

		cond_resched();
		if (unlikely(khugepaged_test_exit(mm))) {
			progress++;
			break;
		}
B
Bob Liu 已提交
2541 2542
		if (!hugepage_vma_check(vma)) {
skip:
A
Andrea Arcangeli 已提交
2543 2544 2545 2546 2547
			progress++;
			continue;
		}
		hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
		hend = vma->vm_end & HPAGE_PMD_MASK;
2548 2549 2550 2551
		if (hstart >= hend)
			goto skip;
		if (khugepaged_scan.address > hend)
			goto skip;
A
Andrea Arcangeli 已提交
2552 2553
		if (khugepaged_scan.address < hstart)
			khugepaged_scan.address = hstart;
2554
		VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
A
Andrea Arcangeli 已提交
2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582

		while (khugepaged_scan.address < hend) {
			int ret;
			cond_resched();
			if (unlikely(khugepaged_test_exit(mm)))
				goto breakouterloop;

			VM_BUG_ON(khugepaged_scan.address < hstart ||
				  khugepaged_scan.address + HPAGE_PMD_SIZE >
				  hend);
			ret = khugepaged_scan_pmd(mm, vma,
						  khugepaged_scan.address,
						  hpage);
			/* move to next address */
			khugepaged_scan.address += HPAGE_PMD_SIZE;
			progress += HPAGE_PMD_NR;
			if (ret)
				/* we released mmap_sem so break loop */
				goto breakouterloop_mmap_sem;
			if (progress >= pages)
				goto breakouterloop;
		}
	}
breakouterloop:
	up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
breakouterloop_mmap_sem:

	spin_lock(&khugepaged_mm_lock);
2583
	VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
A
Andrea Arcangeli 已提交
2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618
	/*
	 * Release the current mm_slot if this mm is about to die, or
	 * if we scanned all vmas of this mm.
	 */
	if (khugepaged_test_exit(mm) || !vma) {
		/*
		 * Make sure that if mm_users is reaching zero while
		 * khugepaged runs here, khugepaged_exit will find
		 * mm_slot not pointing to the exiting mm.
		 */
		if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
			khugepaged_scan.mm_slot = list_entry(
				mm_slot->mm_node.next,
				struct mm_slot, mm_node);
			khugepaged_scan.address = 0;
		} else {
			khugepaged_scan.mm_slot = NULL;
			khugepaged_full_scans++;
		}

		collect_mm_slot(mm_slot);
	}

	return progress;
}

static int khugepaged_has_work(void)
{
	return !list_empty(&khugepaged_scan.mm_head) &&
		khugepaged_enabled();
}

static int khugepaged_wait_event(void)
{
	return !list_empty(&khugepaged_scan.mm_head) ||
2619
		kthread_should_stop();
A
Andrea Arcangeli 已提交
2620 2621
}

2622
static void khugepaged_do_scan(void)
A
Andrea Arcangeli 已提交
2623
{
2624
	struct page *hpage = NULL;
A
Andrea Arcangeli 已提交
2625 2626
	unsigned int progress = 0, pass_through_head = 0;
	unsigned int pages = khugepaged_pages_to_scan;
2627
	bool wait = true;
A
Andrea Arcangeli 已提交
2628 2629 2630 2631

	barrier(); /* write khugepaged_pages_to_scan to local stack */

	while (progress < pages) {
2632
		if (!khugepaged_prealloc_page(&hpage, &wait))
2633
			break;
2634

2635
		cond_resched();
A
Andrea Arcangeli 已提交
2636

2637 2638 2639
		if (unlikely(kthread_should_stop() || freezing(current)))
			break;

A
Andrea Arcangeli 已提交
2640 2641 2642 2643 2644 2645
		spin_lock(&khugepaged_mm_lock);
		if (!khugepaged_scan.mm_slot)
			pass_through_head++;
		if (khugepaged_has_work() &&
		    pass_through_head < 2)
			progress += khugepaged_scan_mm_slot(pages - progress,
2646
							    &hpage);
A
Andrea Arcangeli 已提交
2647 2648 2649 2650 2651
		else
			progress = pages;
		spin_unlock(&khugepaged_mm_lock);
	}

2652 2653
	if (!IS_ERR_OR_NULL(hpage))
		put_page(hpage);
2654 2655
}

2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673
static void khugepaged_wait_work(void)
{
	try_to_freeze();

	if (khugepaged_has_work()) {
		if (!khugepaged_scan_sleep_millisecs)
			return;

		wait_event_freezable_timeout(khugepaged_wait,
					     kthread_should_stop(),
			msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
		return;
	}

	if (khugepaged_enabled())
		wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
}

A
Andrea Arcangeli 已提交
2674 2675 2676 2677
static int khugepaged(void *none)
{
	struct mm_slot *mm_slot;

2678
	set_freezable();
A
Andrea Arcangeli 已提交
2679 2680
	set_user_nice(current, 19);

X
Xiao Guangrong 已提交
2681 2682 2683 2684
	while (!kthread_should_stop()) {
		khugepaged_do_scan();
		khugepaged_wait_work();
	}
A
Andrea Arcangeli 已提交
2685 2686 2687 2688 2689 2690 2691 2692 2693 2694

	spin_lock(&khugepaged_mm_lock);
	mm_slot = khugepaged_scan.mm_slot;
	khugepaged_scan.mm_slot = NULL;
	if (mm_slot)
		collect_mm_slot(mm_slot);
	spin_unlock(&khugepaged_mm_lock);
	return 0;
}

2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719
static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
		unsigned long haddr, pmd_t *pmd)
{
	struct mm_struct *mm = vma->vm_mm;
	pgtable_t pgtable;
	pmd_t _pmd;
	int i;

	pmdp_clear_flush(vma, haddr, pmd);
	/* leave pmd empty until pte is filled */

	pgtable = pgtable_trans_huge_withdraw(mm);
	pmd_populate(mm, &_pmd, pgtable);

	for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
		pte_t *pte, entry;
		entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
		entry = pte_mkspecial(entry);
		pte = pte_offset_map(&_pmd, haddr);
		VM_BUG_ON(!pte_none(*pte));
		set_pte_at(mm, haddr, pte, entry);
		pte_unmap(pte);
	}
	smp_wmb(); /* make pte visible before pmd */
	pmd_populate(mm, pmd, pgtable);
2720
	put_huge_zero_page();
2721 2722
}

2723 2724
void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
		pmd_t *pmd)
2725 2726
{
	struct page *page;
2727
	struct mm_struct *mm = vma->vm_mm;
2728 2729 2730
	unsigned long haddr = address & HPAGE_PMD_MASK;
	unsigned long mmun_start;	/* For mmu_notifiers */
	unsigned long mmun_end;		/* For mmu_notifiers */
2731 2732

	BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2733

2734 2735 2736
	mmun_start = haddr;
	mmun_end   = haddr + HPAGE_PMD_SIZE;
	mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2737 2738 2739
	spin_lock(&mm->page_table_lock);
	if (unlikely(!pmd_trans_huge(*pmd))) {
		spin_unlock(&mm->page_table_lock);
2740 2741 2742 2743 2744 2745 2746
		mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
		return;
	}
	if (is_huge_zero_pmd(*pmd)) {
		__split_huge_zero_page_pmd(vma, haddr, pmd);
		spin_unlock(&mm->page_table_lock);
		mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2747 2748 2749 2750 2751 2752
		return;
	}
	page = pmd_page(*pmd);
	VM_BUG_ON(!page_count(page));
	get_page(page);
	spin_unlock(&mm->page_table_lock);
2753
	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2754 2755 2756 2757 2758 2759

	split_huge_page(page);

	put_page(page);
	BUG_ON(pmd_trans_huge(*pmd));
}
2760

2761 2762 2763 2764 2765 2766 2767 2768 2769 2770
void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
		pmd_t *pmd)
{
	struct vm_area_struct *vma;

	vma = find_vma(mm, address);
	BUG_ON(vma == NULL);
	split_huge_page_pmd(vma, address, pmd);
}

2771 2772 2773 2774 2775 2776 2777
static void split_huge_page_address(struct mm_struct *mm,
				    unsigned long address)
{
	pmd_t *pmd;

	VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));

B
Bob Liu 已提交
2778 2779
	pmd = mm_find_pmd(mm, address);
	if (!pmd)
2780 2781 2782 2783 2784
		return;
	/*
	 * Caller holds the mmap_sem write mode, so a huge pmd cannot
	 * materialize from under us.
	 */
2785
	split_huge_page_pmd_mm(mm, address, pmd);
2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827
}

void __vma_adjust_trans_huge(struct vm_area_struct *vma,
			     unsigned long start,
			     unsigned long end,
			     long adjust_next)
{
	/*
	 * If the new start address isn't hpage aligned and it could
	 * previously contain an hugepage: check if we need to split
	 * an huge pmd.
	 */
	if (start & ~HPAGE_PMD_MASK &&
	    (start & HPAGE_PMD_MASK) >= vma->vm_start &&
	    (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
		split_huge_page_address(vma->vm_mm, start);

	/*
	 * If the new end address isn't hpage aligned and it could
	 * previously contain an hugepage: check if we need to split
	 * an huge pmd.
	 */
	if (end & ~HPAGE_PMD_MASK &&
	    (end & HPAGE_PMD_MASK) >= vma->vm_start &&
	    (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
		split_huge_page_address(vma->vm_mm, end);

	/*
	 * If we're also updating the vma->vm_next->vm_start, if the new
	 * vm_next->vm_start isn't page aligned and it could previously
	 * contain an hugepage: check if we need to split an huge pmd.
	 */
	if (adjust_next > 0) {
		struct vm_area_struct *next = vma->vm_next;
		unsigned long nstart = next->vm_start;
		nstart += adjust_next << PAGE_SHIFT;
		if (nstart & ~HPAGE_PMD_MASK &&
		    (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
		    (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
			split_huge_page_address(next->vm_mm, nstart);
	}
}