Re: inconsistent xfs log record

[Michael Nishimoto <miken@agami.com>]

David Chinner wrote:
> On Mon, Apr 07, 2008 at 06:54:21PM -0700, Michael Nishimoto wrote:
>  > I've just finished analyzing an xfs filesystem which won't recover.
>  > An inconsistent log record has 332 log operations but the num_logop field
>  > in the record header says 333 log operations.  The result is that xfs
>  > recovery
>  > complains with "bad clientid" because recovery eventually attempts to 
> decode
>  > garbage.
>  >
>  > The log record really has 332 log ops (I counted!).
>  >
>  > Looking through xlog_write(), I don't see any way that record_cnt can be
>  > bumped
>  > without also writing out a log operation.
> 
> Yeah, i remember going through this a while back tracking done the same
> error on snapshot images (was a freeze problem) and I couldn't see how
> it would happen, either.
> 
> Still, it's a single bit error so that's always suspicious - can you
> reproduce this error reliably?

We haven't tried doing this yet, but I doubt we will because the test that
found this problem is not unusual.  We just pulled power while alot of
activity was present.

A single bit, but also off-by-one. :-)

> 
>  > Does this issue ring a bell with anyone?
> 
> FWIW, I have had 2-3 failures with a "bad clientid" on a 64k page size ia64
> box since I switched from 16k page size about a month ago. I haven't 
> seen any
> consistent pattern to the failure yet, nor had a chance to perform any
> sort of triage on the problem so I can't say whether I'm seeing the same
> issue...
> 
> Cheers,
> 
> Dave.
> --
> Dave Chinner
> Principal Engineer
> SGI Australian Software Group
>