Re: silent semantic changes with reiser4

Jamie Lokier
2004-08-26T12:28:07Z

Rik van Riel wrote:
> > cat <a >b does not preserve following file properties even on standard
> > UNIX filesystems: name,owner,group,permissions.
>
> Losing permissions is one thing. Annoying, mostly.

I find losing mtime annoying. That's why I don't use Mozilla's
download manager (and Navigator's before it) because they presumed
that mtime isn't worth copying. ncftp and wget do the right thing,
but it's annoying that I can't use the fancy tools and get the
metadata _I_ want transferred by them.

> However, actual losing file data during such a copy is
> nothing short of a disaster, IMHO.

Note that file-as-directory doesn't imply that you can store just
anything into those directories.

Is it a problem to decree that "file data MUST NOT be stored in a
metadata directory; only non-essential metadata and data computed from
the file data may be stored"?

> In my opinion we shouldn't merge file-as-a-directory
> semantics into the kernel until we figure out how to
> fix the backup/restore problem and keep standard unix
> utilities work.

Same as xattrs, for data that should be stored.

But, unlike xattrs, while permissions and C-source-encoding should be
stored, some of this metadata should _not_ be stored when making an
archive and perhaps not when making a backup either.

Personally I wouldn't want an archive containing a file to save and
restore recomputable metadata like cached, extracted-on-demand MP3 id
tags and email headers-as-metadata. I'd rather they were recalculated
when needed, implying a stronger guarantee about their relationship to
the data from which they're extracted - and implying that a user
program might not be allowed to set them to inconsistent values.

-- Jamie