There are two "find" related bugs in /etc/sysconfig/btrfsmaintenance and
/usr/share/btrfsmaintenance/btrfs-defrag.sh:

1. The default value for BTRFS_DEFRAG_MIN_SIZE is "+1m"; find complains about
this because it should be spelled "+1M"

2. The "-xdev" parameter must occur *before* any non-option argument; here is
the error message when running the /usr/share/btrfsmaintenance/btrfs-defrag.sh
script:

  find: warning: you have specified the -xdev option after a non-option
argument -size, but options are not positional (-xdev affects tests specified
before it as well as those specified after it).  Please specify options before
other arguments.

   The "-xdev" should be moved right after "$P" and before the "-size ..."