This is an old revision of the document!
https://www.cyberciti.biz/faq/linux-btrfs-fstab-entry-to-mount-filesystem-at-startup/
How to balance a btrfs (when running out of free space even when there is really free space)
https://ohthehugemanatee.org/blog/2019/02/11/btrfs-out-of-space-emergency-response/
The code “btrfs_map_physical.c” for finding out the swap file offset for hibernation resume doesn't work on 32bits.
Change:
fd = open(argv[optind], O_RDONLY);
For:
fd = open(argv[optind], O_RDONLY |O_LARGEFILE );
and compile using the following command line:
gcc -O2 -o btrfs_map_physical -D_FILE_OFFSET_BITS=64 btrfs_map_physical.c