static int coroutine_fn cow_co_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *num_same) { int64_t bitnum = sector_num + sizeof(struct cow_header_v2) * 8; uint64_t offset = (bitnum / 8) & -BDRV_SECTOR_SIZE; uint8_t bitmap[BDRV_SECTOR_SIZE]; int ret; int changed; ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap)); if (ret < 0) { return ret; } bitnum &= BITS_PER_BITMAP_SECTOR - 1; changed = cow_test_bit(bitnum, bitmap); *num_same = cow_find_streak(bitmap, changed, bitnum, nb_sectors); return changed; }