[Libguestfs] Should umask takes effect when we create device file via mknod?

[Yufang Zhang]

Hi all,
Currently, umask takes effect when we create device file via mknod, as 
bellow commands show:
 ><fs> mknod-b 0760 8 1 /dev/sdf
 ><fs> ll /dev/sdf
brwxr----- 1 root root 8, 1 Apr 15 11:10 /sysroot/dev/sdf

But I wonder whether it is reasonable? For mknod(1), when we use option 
-m mode, we set file permission bits to MODE, not a=rw - umask. Should 
this also be applicable to mknod in guestfish, thus when we create 
device file with mode set, umask doesn't take effect?