/*
 * This must be called only on pages that have
 * been verified to be in the swap cache.
 */
void __delete_from_swap_cache(struct page *page)
{
	swp_entry_t entry;
	struct address_space *address_space;

	VM_BUG_ON(!PageLocked(page));
	VM_BUG_ON(!PageSwapCache(page));
	VM_BUG_ON(PageWriteback(page));

	entry.val = page_private(page);
	address_space = swap_address_space(entry);
	radix_tree_delete(&address_space->page_tree, page_private(page));
	set_page_private(page, 0);
	ClearPageSwapCache(page);
	address_space->nrpages--;
	__dec_zone_page_state(page, NR_FILE_PAGES);
	INC_CACHE_INFO(del_total);
}

static inline void pgd_list_del(pgd_t *pgd)
{
	struct page *next, **pprev, *page = virt_to_page(pgd);
	next = (struct page *) page->index;
	pprev = (struct page **) page_private(page);
	*pprev = next;
	if (next)
		set_page_private(next, (unsigned long) pprev);
}

void fscrypt_restore_control_page(struct page *page)
{
	struct fscrypt_ctx *ctx;

	ctx = (struct fscrypt_ctx *)page_private(page);
	set_page_private(page, (unsigned long)NULL);
	ClearPagePrivate(page);
	unlock_page(page);
	fscrypt_release_ctx(ctx);
}

static void put_compound_page(struct page *page)
{
	page = (struct page *)page_private(page);
	if (put_page_testzero(page)) {
		void (*dtor)(struct page *page);

		dtor = (void (*)(struct page *))page[1].lru.next;
		(*dtor)(page);
	}
}

static void kimage_free_pages(struct page *page)
{
	unsigned int order, count, i;

	order = page_private(page);
	count = 1 << order;
	for (i = 0; i < count; i++)
		ClearPageReserved(page + i);
	__free_pages(page, order);
}

void ext4_restore_control_page(struct page *data_page)
{
	struct ext4_crypto_ctx *ctx =
		(struct ext4_crypto_ctx *)page_private(data_page);

	set_page_private(data_page, (unsigned long)NULL);
	ClearPagePrivate(data_page);
	unlock_page(data_page);
	ext4_release_crypto_ctx(ctx);
}

static struct nfs_page *nfs_page_find_request_locked(struct page *page)
{
	struct nfs_page *req = NULL;

	if (PagePrivate(page)) {
		req = (struct nfs_page *)page_private(page);
		if (req != NULL)
			kref_get(&req->wb_kref);
	}
	return req;
}

/**
 * __delete_from_swap_cache:page从交换区高速缓存中删去
 */
void __delete_from_swap_cache(struct page *page)
{
	VM_BUG_ON(!PageLocked(page));
	VM_BUG_ON(!PageSwapCache(page));
	VM_BUG_ON(PageWriteback(page));

	radix_tree_delete(&swapper_space.page_tree, page_private(page));
	set_page_private(page, 0);
	ClearPageSwapCache(page);
	total_swapcache_pages--;
	__dec_zone_page_state(page, NR_FILE_PAGES);
	INC_CACHE_INFO(del_total);
}

/**
 * delete_from_swap_cache:page从交换区高速缓存中删除
 */
void delete_from_swap_cache(struct page *page)
{
	swp_entry_t entry;

	entry.val = page_private(page);

	spin_lock_irq(&swapper_space.tree_lock);
	__delete_from_swap_cache(page);
	spin_unlock_irq(&swapper_space.tree_lock);

	swapcache_free(entry, page);
	page_cache_release(page);
}

/**
 * gnttab_free_pages - free pages allocated by gnttab_alloc_pages()
 * @nr_pages; number of pages to free
 * @pages: the pages
 */
void gnttab_free_pages(int nr_pages, struct page **pages)
{
	int i;

	for (i = 0; i < nr_pages; i++) {
		if (PagePrivate(pages[i])) {
#if BITS_PER_LONG < 64
			kfree((void *)page_private(pages[i]));
#endif
			ClearPagePrivate(pages[i]);
		}
	}
	free_xenballooned_pages(nr_pages, pages);
}

/*
 * This must be called only on pages that have
 * been verified to be in the swap cache.
 */
void __delete_from_swap_cache(struct page *page)
{
	BUG_ON(!PageLocked(page));
	BUG_ON(!PageSwapCache(page));
	BUG_ON(PageWriteback(page));
	BUG_ON(PagePrivate(page));

	radix_tree_delete(&swapper_space.page_tree, page_private(page));
	set_page_private(page, 0);
	ClearPageSwapCache(page);
	total_swapcache_pages--;
	pagecache_acct(-1);
	INC_CACHE_INFO(del_total);
}

/* Convert DMA address to offset into virtually contiguous buffer. */
size_t fw_iso_buffer_lookup(struct fw_iso_buffer *buffer, dma_addr_t completed)
{
	int i;
	dma_addr_t address;
	ssize_t offset;

	for (i = 0; i < buffer->page_count; i++) {
		address = page_private(buffer->pages[i]);
		offset = (ssize_t)completed - (ssize_t)address;
		if (offset > 0 && offset <= PAGE_SIZE)
			return (i << PAGE_SHIFT) + offset;
	}

	return 0;
}

/*
 * How many references to page are currently swapped out?
 */
static inline int page_swapcount(struct page *page)
{
	int count = 0;
	struct swap_info_struct *p;
	swp_entry_t entry;

	entry.val = page_private(page);
	p = swap_info_get(entry);
	if (p) {
		/* Subtract the 1 for the swap cache itself */
		count = p->swap_map[swp_offset(entry)] - 1;
		spin_unlock(&swap_lock);
	}
	return count;
}

void put_page(struct page *page)
{
	if (unlikely(PageCompound(page))) {
		page = (struct page *)page_private(page);
		if (put_page_testzero(page)) {
			void (*dtor)(struct page *page);

			dtor = (void (*)(struct page *))page[1].mapping;
			(*dtor)(page);
		}
		return;
	}
	if (put_page_testzero(page))
		__page_cache_release(page);
}

/*
 * This must be called only on pages that have
 * been verified to be in the swap cache and locked.
 * It will never put the page into the free list,
 * the caller has a reference on the page.
 */
void delete_from_swap_cache(struct page *page)
{
    swp_entry_t entry;
    struct address_space *address_space;

    entry.val = page_private(page);

    address_space = swap_address_space(entry);
    spin_lock_irq(&address_space->tree_lock);
    __delete_from_swap_cache(page);
    spin_unlock_irq(&address_space->tree_lock);

    swapcache_free(entry);
    put_page(page);
}

void fw_iso_buffer_destroy(struct fw_iso_buffer *buffer,
			   struct fw_card *card)
{
	int i;
	dma_addr_t address;

	for (i = 0; i < buffer->page_count; i++) {
		address = page_private(buffer->pages[i]);
		dma_unmap_page(card->device, address,
			       PAGE_SIZE, buffer->direction);
		__free_page(buffer->pages[i]);
	}

	kfree(buffer->pages);
	buffer->pages = NULL;
}

void f2fs_restore_and_release_control_page(struct page **page)
{
	struct f2fs_crypto_ctx *ctx;
	struct page *bounce_page;

	/* The bounce data pages are unmapped. */
	if ((*page)->mapping)
		return;

	/* The bounce data page is unmapped. */
	bounce_page = *page;
	ctx = (struct f2fs_crypto_ctx *)page_private(bounce_page);

	/* restore control page */
	*page = ctx->w.control_page;

	f2fs_restore_control_page(bounce_page);
}

void fscrypt_pullback_bio_page(struct page **page, bool restore)
{
	struct fscrypt_ctx *ctx;
	struct page *bounce_page;

	/* The bounce data pages are unmapped. */
	if ((*page)->mapping)
		return;

	/* The bounce data page is unmapped. */
	bounce_page = *page;
	ctx = (struct fscrypt_ctx *)page_private(bounce_page);

	/* restore control page */
	*page = ctx->w.control_page;

	if (restore)
		fscrypt_restore_control_page(bounce_page);
}

int fw_iso_buffer_init(struct fw_iso_buffer *buffer, struct fw_card *card,
		       int page_count, enum dma_data_direction direction)
{
	int i, j;
	dma_addr_t address;

	buffer->page_count = page_count;
	buffer->direction = direction;

	buffer->pages = kmalloc(page_count * sizeof(buffer->pages[0]),
				GFP_KERNEL);
	if (buffer->pages == NULL)
		goto out;

	for (i = 0; i < buffer->page_count; i++) {
		buffer->pages[i] = alloc_page(GFP_KERNEL | GFP_DMA32 | __GFP_ZERO);
		if (buffer->pages[i] == NULL)
			goto out_pages;

		address = dma_map_page(card->device, buffer->pages[i],
				       0, PAGE_SIZE, direction);
		if (dma_mapping_error(card->device, address)) {
			__free_page(buffer->pages[i]);
			goto out_pages;
		}
		set_page_private(buffer->pages[i], address);
	}

	return 0;

 out_pages:
	for (j = 0; j < i; j++) {
		address = page_private(buffer->pages[j]);
		dma_unmap_page(card->device, address,
			       PAGE_SIZE, direction);
		__free_page(buffer->pages[j]);
	}
	kfree(buffer->pages);
 out:
	buffer->pages = NULL;

	return -ENOMEM;
}

/*
 * Work out if there are any other processes sharing this
 * swap cache page. Free it if you can. Return success.
 */
int remove_exclusive_swap_page(struct page *page)
{
	int retval;
	struct swap_info_struct * p;
	swp_entry_t entry;

	BUG_ON(PagePrivate(page));
	BUG_ON(!PageLocked(page));

	if (!PageSwapCache(page))
		return 0;
	if (PageWriteback(page))
		return 0;
	if (page_count(page) != 2) /* 2: us + cache */
		return 0;

	entry.val = page_private(page);
	p = swap_info_get(entry);
	if (!p)
		return 0;

	/* Is the only swap cache user the cache itself? */
	retval = 0;
	if (p->swap_map[swp_offset(entry)] == 1) {
		/* Recheck the page count with the swapcache lock held.. */
		write_lock_irq(&swapper_space.tree_lock);
		if ((page_count(page) == 2) && !PageWriteback(page)) {
			__delete_from_swap_cache(page);
			SetPageDirty(page);
			retval = 1;
		}
		write_unlock_irq(&swapper_space.tree_lock);
	}
	spin_unlock(&swap_lock);

	if (retval) {
		swap_free(entry);
		page_cache_release(page);
	}

	return retval;
}