The library function fuse_loop_mt() is currently unimplemented. It should return -1 to indicate failure rather than claim success when it clearly didn't do anything useful. fuse_loop_mt() should never be called by file systems since fuse_parse_cmdline() and fuse_setup() alway return 0 as the value of the mt back to callers.
Index: fuse.c =================================================================== RCS file: /cvs/src/lib/libfuse/fuse.c,v retrieving revision 1.32 diff -u -p -r1.32 fuse.c --- fuse.c 2 Nov 2017 13:55:37 -0000 1.32 +++ fuse.c 3 Nov 2017 17:33:58 -0000 @@ -236,7 +236,7 @@ fuse_get_session(struct fuse *f) int fuse_loop_mt(unused struct fuse *fuse) { - return (0); + return (-1); } struct fuse *