Displaying streams as xattrs

ronnie sahlberg ronniesahlberg at gmail.com
Tue May 23 00:59:27 UTC 2023

Yeah, I don't think we should surface these as xattrs.
Xattrs are already way too small for most of the usecases of ADS on
windows (file metadata for explorer etc)
and they are also just an atomic blob and not a proper filedescriptor.
Since ADS is still just a file, any application that in the future
will use ADS features should only do so via
a proper filedescriptors, where it is possible to
seek/read/write/truncate/...  so IMHO we shouldn't offer them an
alternative but inferior API. Because they might mistakenly start to use it. :-(

There are no real applications, yet, for linux that uses ADS but there
are many that potentially could use ADS or
become ADS aware. GUI Filebrowsers would be a nice usecase. As would
making 'cp', 'mv', 'tar', 'rsync', ... ADS aware.

So let's not do it with xattrs.
No one needs/asks for this right now so it would be code we will have
to maintain but has no users.

What we should do though is think about and talk with the NTFS folks
so that we make sure our aims and APIs will align with the plans they
And once we have multiple filesystems supporting it (cifs.ko and ntfs)
then we can start thinking about how to encourage external users and
applications to use it.
There are really nice use-cases for ADS where one can store additional
metadata within the "file" itself.

ronnie s

On Tue, 23 May 2023 at 02:21, Jeremy Allison <jra at samba.org> wrote:
> On Mon, May 22, 2023 at 01:39:50AM -0500, Steve French wrote:
> >On Sun, May 21, 2023 at 11:33 PM ronnie sahlberg
> ><ronniesahlberg at gmail.com> wrote:
> >>
> >> A problem  we have with xattrs today is that we use EAs and these are
> >> case insensitive.
> >> Even worse I think windows may also convert the names to uppercase :-(
> >> And there is no way to change it in the registry :-(
> >
> >But for alternate data streams if we allowed them to be retrieved via xattrs,
> >would case sensitivity matter?  Alternate data streams IIRC are already
> >case preserving.   Presumably the more common case is for a Linux user
> >to read (or backup) an existing alternate data stream (which are usually
> >created by Windows so case sensitivity would not be relevant).
> Warning Will Robinson ! Mixing ADS and xattrs on the client side is a receipe for
> confusion and disaster IMHO.
> They really are different things. No good will come of trying to mix
> the two into one client namespace.

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