void __pagevec_lru_add_active(struct pagevec *pvec)
{
	int i;
	struct zone *zone = NULL;

	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		struct zone *pagezone = page_zone(page);

		if (pagezone != zone) {
			if (zone)
				spin_unlock_irq(&zone->lru_lock);
			zone = pagezone;
			spin_lock_irq(&zone->lru_lock);
		}
		if (TestSetPageLRU(page))
			BUG();
		if (TestSetPageActive(page))
			BUG();
		add_page_to_active_list(zone, page);
	}
	if (zone)
		spin_unlock_irq(&zone->lru_lock);
	release_pages(pvec->pages, pvec->nr, pvec->cold);
	pagevec_reinit(pvec);
}

// dyc: add all pages into inactive list
void __pagevec_lru_add(struct pagevec *pvec)
{
	int i;
	struct zone *zone = NULL;
    // dyc: iterate all pages and add them to inactive list
	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		struct zone *pagezone = page_zone(page);
        // dyc: lock/unlock until next zone
		if (pagezone != zone) {
			if (zone)
				spin_unlock_irq(&zone->lru_lock);
			zone = pagezone;
			spin_lock_irq(&zone->lru_lock);
		}
		VM_BUG_ON(PageLRU(page));
        // dyc: set pg LRU flag
		SetPageLRU(page);
        // dyc: add to inactive list and increase vm_stat
		add_page_to_inactive_list(zone, page);
	}
	if (zone)
		spin_unlock_irq(&zone->lru_lock);
	release_pages(pvec->pages, pvec->nr, pvec->cold);
	pagevec_reinit(pvec);
}

static void pagevec_lru_move_fn(struct pagevec *pvec,
				void (*move_fn)(struct page *page, void *arg),
				void *arg)
{
	int i;
	struct zone *zone = NULL;
	unsigned long flags = 0;

	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		struct zone *pagezone = page_zone(page);

		if (pagezone != zone) {
			if (zone)
				spin_unlock_irqrestore(&zone->lru_lock, flags);
			zone = pagezone;
			spin_lock_irqsave(&zone->lru_lock, flags);
		}

		(*move_fn)(page, arg);
	}
	if (zone)
		spin_unlock_irqrestore(&zone->lru_lock, flags);
	release_pages(pvec->pages, pvec->nr, pvec->cold);
	pagevec_reinit(pvec);
}

/*
 * The pages which we're about to release may be in the deferred lru-addition
 * queues.  That would prevent them from really being freed right now.  That's
 * OK from a correctness point of view but is inefficient - those pages may be
 * cache-warm and we want to give them back to the page allocator as soon as possible
 *
 * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 * and __pagevec_lru_add_active() call release_pages() directly to avoid
 * mutual recursion.
 */
void __pagevec_release(struct pagevec *pvec)
{
	lru_add_drain();
	release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
    // dyc: set pvec->nr to 0
	pagevec_reinit(pvec);
}

/*
 * The pages which we're about to release may be in the deferred lru-addition
 * queues.  That would prevent them from really being freed right now.  That's
 * OK from a correctness point of view but is inefficient - those pages may be
 * cache-warm and we want to give them back to the page allocator ASAP.
 *
 * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 * and __pagevec_lru_add_active() call release_pages() directly to avoid
 * mutual recursion.
 */
void __pagevec_release(struct pagevec *pvec)
{
	if (!pvec->percpu_pvec_drained) {
		lru_add_drain();
		pvec->percpu_pvec_drained = true;
	}
	release_pages(pvec->pages, pagevec_count(pvec));
	pagevec_reinit(pvec);
}

/*
 * Passed an array of pages, drop them all from swapcache and then release
 * them.  They are removed from the LRU and freed if this is their last use.
 */
void free_pages_and_swap_cache(struct page **pages, int nr)
{
    struct page **pagep = pages;
    int i;

    lru_add_drain();
    for (i = 0; i < nr; i++)
        free_swap_cache(pagep[i]);
    release_pages(pagep, nr, false);
}

void my_free(void *ptr)
{
    header_t *header;

    if (ptr)
    {
        header = (header_t *)((UINTPTR_T)ptr - sizeof (header_t));
        add_to_list(header, header->list);
        merge_headers(header->list);
        release_pages(header->list);
    }
}

/*
 * Passed an array of pages, drop them all from swapcache and then release
 * them.  They are removed from the LRU and freed if this is their last use.
 */
void free_pages_and_swap_cache(struct page **pages, int nr)
{
	struct page **pagep = pages;

	lru_add_drain();
	while (nr) {
		int todo = min(nr, PAGEVEC_SIZE);
		int i;

		for (i = 0; i < todo; i++)
			free_swap_cache(pagep[i]);
		release_pages(pagep, todo, 0);
		pagep += todo;
		nr -= todo;
	}
}

static void ____pagevec_lru_deactivate(struct pagevec *pvec)
{
	int i;
	struct zone *zone = NULL;

	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];
		struct zone *pagezone = page_zone(page);

		if (pagezone != zone) {
			if (zone)
				spin_unlock_irq(&zone->lru_lock);
			zone = pagezone;
			spin_lock_irq(&zone->lru_lock);
		}
		lru_deactivate(page, zone);
	}
	if (zone)
		spin_unlock_irq(&zone->lru_lock);

	release_pages(pvec->pages, pvec->nr, pvec->cold);
	pagevec_reinit(pvec);
}

void fis_free(void *address){
    if(release_pages(address)!=0) printf("Error\n");
}

static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
{
	const int num_pages = obj->base.size >> PAGE_SHIFT;
	struct mm_struct *mm = obj->userptr.mm->mm;
	struct page **pvec;
	struct sg_table *pages;
	bool active;
	int pinned;

	/* If userspace should engineer that these pages are replaced in
	 * the vma between us binding this page into the GTT and completion
	 * of rendering... Their loss. If they change the mapping of their
	 * pages they need to create a new bo to point to the new vma.
	 *
	 * However, that still leaves open the possibility of the vma
	 * being copied upon fork. Which falls under the same userspace
	 * synchronisation issue as a regular bo, except that this time
	 * the process may not be expecting that a particular piece of
	 * memory is tied to the GPU.
	 *
	 * Fortunately, we can hook into the mmu_notifier in order to
	 * discard the page references prior to anything nasty happening
	 * to the vma (discard or cloning) which should prevent the more
	 * egregious cases from causing harm.
	 */

	if (obj->userptr.work) {
		/* active flag should still be held for the pending work */
		if (IS_ERR(obj->userptr.work))
			return PTR_ERR(obj->userptr.work);
		else
			return -EAGAIN;
	}

	pvec = NULL;
	pinned = 0;

	if (mm == current->mm) {
		pvec = kvmalloc_array(num_pages, sizeof(struct page *),
				      GFP_KERNEL |
				      __GFP_NORETRY |
				      __GFP_NOWARN);
		if (pvec) /* defer to worker if malloc fails */
			pinned = __get_user_pages_fast(obj->userptr.ptr,
						       num_pages,
						       !i915_gem_object_is_readonly(obj),
						       pvec);
	}

	active = false;
	if (pinned < 0) {
		pages = ERR_PTR(pinned);
		pinned = 0;
	} else if (pinned < num_pages) {
		pages = __i915_gem_userptr_get_pages_schedule(obj);
		active = pages == ERR_PTR(-EAGAIN);
	} else {
		pages = __i915_gem_userptr_alloc_pages(obj, pvec, num_pages);
		active = !IS_ERR(pages);
	}
	if (active)
		__i915_gem_userptr_set_active(obj, true);

	if (IS_ERR(pages))
		release_pages(pvec, pinned);
	kvfree(pvec);

	return PTR_ERR_OR_ZERO(pages);
}

static void
__i915_gem_userptr_get_pages_worker(struct work_struct *_work)
{
	struct get_pages_work *work = container_of(_work, typeof(*work), work);
	struct drm_i915_gem_object *obj = work->obj;
	const int npages = obj->base.size >> PAGE_SHIFT;
	struct page **pvec;
	int pinned, ret;

	ret = -ENOMEM;
	pinned = 0;

	pvec = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
	if (pvec != NULL) {
		struct mm_struct *mm = obj->userptr.mm->mm;
		unsigned int flags = 0;

		if (!i915_gem_object_is_readonly(obj))
			flags |= FOLL_WRITE;

		ret = -EFAULT;
		if (mmget_not_zero(mm)) {
			down_read(&mm->mmap_sem);
			while (pinned < npages) {
				ret = get_user_pages_remote
					(work->task, mm,
					 obj->userptr.ptr + pinned * PAGE_SIZE,
					 npages - pinned,
					 flags,
					 pvec + pinned, NULL, NULL);
				if (ret < 0)
					break;

				pinned += ret;
			}
			up_read(&mm->mmap_sem);
			mmput(mm);
		}
	}

	mutex_lock(&obj->mm.lock);
	if (obj->userptr.work == &work->work) {
		struct sg_table *pages = ERR_PTR(ret);

		if (pinned == npages) {
			pages = __i915_gem_userptr_alloc_pages(obj, pvec,
							       npages);
			if (!IS_ERR(pages)) {
				pinned = 0;
				pages = NULL;
			}
		}

		obj->userptr.work = ERR_CAST(pages);
		if (IS_ERR(pages))
			__i915_gem_userptr_set_active(obj, false);
	}
	mutex_unlock(&obj->mm.lock);

	release_pages(pvec, pinned);
	kvfree(pvec);

	i915_gem_object_put(obj);
	put_task_struct(work->task);
	kfree(work);
}