Hi,

I get a enospc to remount-ro with 5.4.21. Details:

Linux 5.4.21 #1 SMP Fri Feb 21 03:20:26 CET 2020 x86_64 GNU/Linux

btrfs fi usage /media/btrfs (after remount-ro)
Overall:
    Device size:                 511.99GiB
    Device allocated:            511.99GiB
    Device unallocated:              0.00B
    Device missing:                  0.00B
    Used:                        443.68GiB
    Free (estimated):             54.94GiB      (min: 54.94GiB)
    Data ratio:                       1.00
    Metadata ratio:                   1.00
    Global reserve:              512.00MiB      (used: 0.00B)

Data,single: Size:490.98GiB, Used:436.04GiB (88.81%)
   /dev/mapper/LUKS-RC-cd46b6b4909845918eaa285c532476dc  490.98GiB

Metadata,single: Size:21.01GiB, Used:7.65GiB (36.40%)
   /dev/mapper/LUKS-RC-cd46b6b4909845918eaa285c532476dc   21.01GiB

System,single: Size:4.00MiB, Used:80.00KiB (1.95%)
   /dev/mapper/LUKS-RC-cd46b6b4909845918eaa285c532476dc    4.00MiB

Unallocated:
   /dev/mapper/LUKS-RC-cd46b6b4909845918eaa285c532476dc      0.00B

Mount options:
/dev/mapper/LUKS-RC-cd46b6b4909845918eaa285c532476dc on /media/btrfs
type btrfs
(ro,noatime,compress-force=zstd:3,nossd,space_cache=v2,enospc_debug,skip_balance,metadata_ratio=8,subvolid=5,subvol=/)

btrfs fi df /media/btrfs
Data, single: total=490.98GiB, used=436.04GiB
System, single: total=4.00MiB, used=80.00KiB
Metadata, single: total=21.01GiB, used=7.65GiB
GlobalReserve, single: total=512.00MiB, used=0.00B

dmesg attached.