btrfs_test_range_bit_exists
if (btrfs_test_range_bit_exists(&inode->io_tree, cur, cur + range_len - 1,
bool btrfs_test_range_bit_exists(struct extent_io_tree *tree, u64 start, u64 end, u32 bit);
if (btrfs_test_range_bit_exists(io_tree, em->start,
btrfs_test_range_bit_exists(&inode->io_tree, start, end, EXTENT_DEFRAG))
ret = btrfs_test_range_bit_exists(io_tree, offset, range_end,