Get the current supplementary group IDs for the current request
Similar to the getgroups(2) system call, except the return value is always the total number of group IDs, even if it is larger than the specified size.
The current fuse kernel module in linux (as of 2.6.30) doesn't pass the group list to userspace, hence this function needs to parse "/proc/$TID/task/$TID/status" to get the group IDs.
This feature may not be supported on all operating systems. In such a case this function will return -ENOSYS.
Referenced by fuse_getgroups().