• Create a separate swap volume (not necessary)

  sudo btrfs subvolume create /mnt/btrfsbase/swap

  • Add it to /etc/fstab

  UUID=8f9ede3a-912f-40d6-9335-90ed3186e3e4 /swap btrfs defaults,noatime,subvol=swap 0 0

• Be sure there is no discard nor autodefrag options activated for this subvolume
• Create a swapfile

  cd /swap sudo truncate -s 0 swapfile sudo chattr +C swapfile btrfs property set swapfile compression none sudo chmod 600 swapfile sudo dd if=/dev/zero of=swapfile bs=1M count=24576 #reserve 24GB sudo mkswap /swap/swapfile

• Find out resume device:

  sudo findmnt -no UUID -T /swap/swapfile

• swapoffset command doesn't work correctly with btrfs. Download this https://github.com/osandov/osandov-linux/blob/master/scripts/btrfs_map_physical.c and compile it: gcc -O2 -o btrfsmapphysical btrfsmap_physical.c
• Calculate offset
• Write down the last number from the output of the following command:

  sudo btrfsmapphysical /swap/swapfile | head -n 2

• Result:

  FILE OFFSET FILE SIZE EXTENT OFFSET EXTENT TYPE LOGICAL SIZE LOGICAL OFFSET PHYSICAL SIZE DEVID PHYSICAL OFFSET 0 134217728 0 regular 134217728 4594864128 134217728 1 4594864128

• Write down the output of the following command:

  sudo getconf PAGESIZE

  Result: 4096

• Calculate offset: Divide the first number under the PAGESIZE: offset = PHYSICAL_OFFSET/PAGESIZE

4594864128/4096=1121793

• Install u