BTRFS_MAX_BLOCKS_PER_FOLIO
max_size = min(BTRFS_MAX_BLOCKS_PER_FOLIO << sectorsize_bits,
unsigned long submit_bitmap[BITS_TO_LONGS(BTRFS_MAX_BLOCKS_PER_FOLIO)];
unsigned long delalloc_bitmap[BITS_TO_LONGS(BTRFS_MAX_BLOCKS_PER_FOLIO)] = { 0 };
ASSERT(blocks_per_folio <= BTRFS_MAX_BLOCKS_PER_FOLIO);