Re: xfs_scrub: call for testing

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Feb 02, 2018 at 03:36:33PM -0600, Eric Sandeen wrote:
> Hey all - 
> 
> Darrick's done a great job with landing the xfs_scrub code in
> upstream kernel v4.15, and now merged on the for-next branch of
> xfsprogs to be released in xfsprogs-4.15.0.
> 
> As with any big new body of code, there might be some rough
> edges despite best efforts.  It'd be great to have people do
> some testing at this semi-early stage.
> 
> The 10,000ft overview is that the new xfs_scrub command can
> /validate/ a lot of what's on disk while the filesystem
> is mounted; and the ability to repair will come in the future.
> 
> For now, with the 4.15 kernel, functionality is limited to
> "scrubbing" meaning that it will simply check for consistency;
> in 4.15 there is no facility to repair or optimize/preen the
> filesystem.

FWIW the 4.16 kernel enhances scrub to cross-reference metadata with
each other for strengthened checking (not to mention picking up a pile
of bug fixes), so eventually you'll want to move on to that for testing.
Ofc we're not even to -rc1 yet so meh. :)

Longer term, I also have landed the dangerous_repair xfstest group that
uses xfs_db to fuzz every field in a filesystem to see if scrub will
complain and xfs_repair does something about it.  Right now it's a bit
of a mess because it'll trip over scrub/repair not complaining about
fields that have no bad values (think inode timestamps) but I'm working
on a larger analysis of triaging known failures and fixing things that
the tools should catch but don't.

> I'd really value feedback on scrub as it stand at this point -
> Is the documentation clear?  Is the output correct?  Do the
> tool's arguments make sense?  Does it segfault?  Does it
> find real errors?  Does it crash your kernel? Does it
> eat your data?

Yes, please look at those things!


Thanks to Eric for reviewing all the userspace patches, and Dave and
Brian for reviewing all the kernel patches!

--D

> (haha no it won't eat your data)
> ((haha no can't promise that with 100% certainty))
> 
> Thanks,
> -Eric
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