Re: [PATCH v2 0/8] MR924: ntdll: Add support for DOS file attributes

[Erich Hoover (＠ehoover)]

> ...
>
> My gut is that if extended attributes are "universal enough"
> (and usable enough), and we can easily implement DOS attributes over 
> them, modulo slight differences in the API, then there isn't really any 
> need to implement something truly portable. I could be wrong about this, 
> though.

What platforms do you consider to be important here?  I ask because the current implementation (without fallback) supports Linux, Mac OS, FreeBSD, and NetBSD.  That seems to me to be the "important" ones.
> > There is also the storage of [NT extended-attribute (EA)](https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntifs/nf-ntif...) values to consider, when we move toward a non-stub implementation of this feature.
> >
> > Perhaps it would be preferable to produce a design that can be encompass all these issues.

The NTFS spec separates DOS Attributes (Flags) from Extended Attributes (EA).  I would not recommend mixing the two, for fear of an accidental name collision.  If you want to design a fallback mechanism that supports both of these features the same way, then I would suggest structuring it like so:
```
.WINE_METADATA/<filename>/<feature>
```
That way when a copy/move operation is performed on a file then it's easier to copy both features together.
> I don't have a good read on this, personally. I suppose it at least 
> partly depends on whether NT extended attributes are used by any 
> program. I'm at least not aware of any usage?

I am not aware of any non-MS usage, but it is documented.  So, I would not be surprised if some copy protection mechanism does something with it our chooses to do so at some point in the future.  I do know that the Single Instance Storage (SIS) minifilter driver uses an extended attribute to "back reference" the single instance files to find the duplicates/originals.
> I think working out the design completely before submitting any patches 
> would probably be a good idea.
>
> ...

If the OS list above is sufficient then I think we're covered, if we need a fallback implementation then this probably needs a little more thought.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/924#note_9410