Re: FAT, NTFS, CIFS and DOS attributes

[Nicholas Miell <nmiell@comcast.net>]

On Mon, 2005-01-03 at 14:24 -0800, H. Peter Anvin wrote:
> Hello all,
> 
> I recently posted to LKML a patch to get or set DOS attribute flags for 
> fatfs.  That patch used ioctl().  It was suggested that a better way 
> would be using xattrs, although the xattr mechanism seems clumsy to me, 
> and has namespace issues.
> 
> I also think it would be good to have a unified interface for FAT, NTFS 
> and CIFS for these attributes.
> 
> I noticed that CIFS has a placeholder "user.DosAttrib" in cifs/xattr.c, 
> although it doesn't seem to be implemented.
> 
> Questions:
> 
> a) is xattr the right thing?  It seems to be a fairly complex and 
> ill-thought-out mechanism all along, especially the whole namespace 
> business (what is a system attribute to one filesystem is a user 
> attribute to another, for example.)

More importantly, what has a defined meaning for one filesystem and is
interpreted and generated on demand by the kernel is irrelevant or
unsupported on other filesystems.

So, yes, you can't just copy a bunch of files from vfat to ext3 and
preserve the vfat attributes, but you should be able to stuff a bunch of
vfat files into a tar file and then restore them to a vfat filesystem
with all their original attributes intact.

> b) if xattr is the right thing, shouldn't this be in the system 
> namespace rather than the user namespace?

Yes.

> c) What should the representation be?  Binary byte?  String containing a 
> subset of "rhsvda67" (barf)?

ASCII strings require no special tools to manipulate from shell scripts
(or even for the end user to interpret).

-- 
Nicholas Miell <nmiell@comcast.net>