mount function call

In the library reference for the fonction call “mount”, Can someone explain
me what return code -1 mean in this case. Does the function fail for any

"Returns: -1 on failure; no server supports the request (errno is set). "

I’m trying to mount a file in this way, what could be wrong, it return -1.

int rc = mount ("/mds/bin01/mds.qfs","/fs/NewOs",_MOUNT_FORCE |
_MOUNT_REMOUNT ,“cifs”,NULL,0); sed in <anidcu$r6s$>

int rc = mount ("/mds/bin01/mds.qfs","/fs/NewOs",_MOUNT_FORCE |

isn’t that “qnx4” type image?

Oh, if /mds/bin01 is over fs-cifs then it seems to fail anyway
(fs-cifs lacking some func for image mounting?)