right. Samba doesn't care much about VFAT, and you don't care about
all the other attributes, so we should get along fine without treading
on each others toes too much.
I explained what Samba4 does as you asked about the user.DosAttrib
xattr that Steve put a placeholder for in cifsfs. That came from
Samba4, so if you suddenly started using it in a different way I would
get a sore toe :-)
Once the Samba LSM module is done and Wine and Samba start working
more together on all these extra bits of meta-data then we could
consider making your ioctl work on all filesystems when the LSM module
is loaded.