btrfs how to resize a mounted partition?

Question

btrfs

on the server, they incorrectly marked the disk, asked to make all the free space on /, but no, they threw only 16.
Actually, I never worked with btrfs, you need to throw all the free space on /.
resize2fs is obviously not going to work here ;(
As you can see from 320, quite a bit is occupied.

sda      8:0    0  321G  0 disk
├─sda1   8:1    0  200M  0 part /boot/efi
├─sda2   8:2    0    1G  0 part /boot
├─sda3   8:3    0    2G  0 part [SWAP]
└─sda4   8:4    0   16G  0 part /
sr0     11:0    1 1024M  0 rom

Che tried

parted print
Number  Start   End     Size    File system     Name                  Flags
 1      1049kB  211MB   210MB   fat16           EFI System Partition  boot
 2      211MB   1285MB  1074MB  xfs
 3      1285MB  3432MB  2147MB  linux-swap(v1)
 4      3432MB  20.6GB  17.2GB  btrfs

well, resize

resizepart
Partition number? 4
Error: Partition /dev/sda4 is being used. You must unmount it before you modify
it with Parted.