No space left on device - Size=105G, Used=55G, Avail=0

My root filesystem claims I have no space left on device. I've done some searching and can't find anyone with the problem I'm having.

If you look at / you can see that the partition is 105G, used is 55G, yet avail is 0.

Filesystem      Size  Used Avail Use% Mounted on
udev            1.9G     0  1.9G   0% /dev
tmpfs           379M  5.7M  373M   2% /run
/dev/sdf2       105G   55G     0 100% /

df -hi gives this:

Filesystem     Inodes IUsed IFree IUse% Mounted on
udev             469K   492  468K    1% /dev
tmpfs            473K   699  473K    1% /run
/dev/sdf2           0     0     0     - /

I'm not sure what my problem is or how to fix it. Filesystem is btrfs

Edit:

sudo lsof | grep -i deleted

php-fpm7. 3062                  root    3u      REG               0,22        0    2909438 /tmp/.ZendSem.sB49NQ (deleted)
php-fpm7. 3086              www-data    3u      REG               0,22        0    2909438 /tmp/.ZendSem.sB49NQ (deleted)
php-fpm7. 3087              www-data    3u      REG               0,22        0    2909438 /tmp/.ZendSem.sB49NQ (deleted)

Edit 2:

sudo btrfs fi df /

Data, single: total=102.14GiB, used=52.38GiB
System, single: total=4.00MiB, used=16.00KiB
Metadata, single: total=2.01GiB, used=1.50GiB
GlobalReserve, single: total=512.00MiB, used=0.00B