int f2fs_migrate_page(struct address_space *mapping,
		struct page *newpage, struct page *page, enum migrate_mode mode)
{
	int rc, extra_count;
	struct f2fs_inode_info *fi = F2FS_I(mapping->host);
	bool atomic_written = IS_ATOMIC_WRITTEN_PAGE(page);

	BUG_ON(PageWriteback(page));

	/* migrating an atomic written page is safe with the inmem_lock hold */
	if (atomic_written && !mutex_trylock(&fi->inmem_lock))
		return -EAGAIN;

	/*
	 * A reference is expected if PagePrivate set when move mapping,
	 * however F2FS breaks this for maintaining dirty page counts when
	 * truncating pages. So here adjusting the 'extra_count' make it work.
	 */
	extra_count = (atomic_written ? 1 : 0) - page_has_private(page);
	rc = migrate_page_move_mapping(mapping, newpage,
				page, NULL, mode, extra_count);
	if (rc != MIGRATEPAGE_SUCCESS) {
		if (atomic_written)
			mutex_unlock(&fi->inmem_lock);
		return rc;
	}

	if (atomic_written) {
		struct inmem_pages *cur;
		list_for_each_entry(cur, &fi->inmem_pages, list)
			if (cur->page == page) {
				cur->page = newpage;
				break;
			}
		mutex_unlock(&fi->inmem_lock);
		put_page(page);
		get_page(newpage);
	}

	if (PagePrivate(page))
		SetPagePrivate(newpage);
	set_page_private(newpage, page_private(page));

	migrate_page_copy(newpage, page);

	return MIGRATEPAGE_SUCCESS;
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.