Re: [PATCH 4/6] xfs_db: fix metadump name obfuscation for ascii-ci filesystems

Christoph Hellwig
2023-04-12T12:10:10Z

On Tue, Apr 11, 2023 at 08:35:46AM -0700, Darrick J. Wong wrote:
> > obsfucate some names this really seems horribly ugly. I could
> > come up with ideas to fix some of that, but they'd be fairly invasive.
>
> Given that it's rol7 and xoring, I'd love it if someone came up with a
> gentler obfuscate_name() that at least tried to generate obfuscated
> names that weren't full of control characters and other junk that make
> ls output horrible.
>
> Buuuut doing that requires a deep understanding of how the math works.
> I think I've almost grokked it, but applied math has never been my
> specialty. Mark Adler's crc spoof looked promising if we ever follow
> through on Dave's suggestion to change the dahash to crc32c, but that's
> a whole different discussion.

Agreed on all counts.

> > Is there any reason we need to support obsfucatation for ascii-ci,
> > or could we just say we require "-o" to metadump ascii-ci file systems
> > and not deal with this at all given that it never actually worked?
>
> That would be simpler for metadump, yes.
>
> I'm going to introduce a followup series that adds a new xfs_db command
> to generate obfuscated filenames/attrs to exercise the dabtree hash
> collision resolution code. I should probably do that now, since I
> already sent xfs/861 that uses it.
>
> It wouldn't be the end of the world if hashcoll didn't work on asciici
> filesystems, but that /would/ be a testing gap.

Do we really care about that testing gap for a feature you just
deprecated and which has been pretty broken all this time?