btrfs_alloc_page_array
ret = btrfs_alloc_page_array(num_pages, page_array, nofail);
int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array,
ret = btrfs_alloc_page_array(nr_pages, pages, false);
ret = btrfs_alloc_page_array(nr_pages, pages, 0);
ret = btrfs_alloc_page_array(rbio->nr_pages, rbio->stripe_pages, false);
ret = btrfs_alloc_page_array(rbio->nr_pages - data_pages,
ret = btrfs_alloc_page_array(data_pages, rbio->stripe_pages, false);
ret = btrfs_alloc_page_array(nr_pages, pages, 0);