Re: [Jfs-discussion] Strange behavior after a crash

[John G. <jgo...@co...>]

On Fri, Jan 07, 2005 at 05:47:28PM -0600, Dave Kleikamp wrote:
> On Fri, 2005-01-07 at 17:03 -0600, John Goerzen wrote:
> > > Actually, jfs does the equivalent of data=writeback.  In the 2.4 kernel,
> > > it does the equivalent of data=ordered, but I changed the behavior do
> > > avoid a deadlock in 2.6 which I never found the correct fix for.
> > 
> > You might consider this one vote for the data=ordered behavior.  This is
> > probably why I haven't noticed this problem from ext3 filesystems.
> 
> Noted.  For what it's worth, I haven't personally noticed this kind of
> corruption, and haven't had reports of it, so I have assumed that in
> practice it is a kind of rare problem.  Maybe you crashed at an unlucky
> point, or it may be more common than I'm aware of.

I've actually experienced it several times, on several different
machines, but this was the first time that it took longer to fix than
writing an e-mail reporting the problem would take :-)

> > I believe -- but can't prove at the moment -- that these files would
> > have been written to sequentially.
> 
> That may be true, and the nulls you saw in the files could have just
> been the same kind of random data, that happened to be null, due to some
> past use of the disk blocks.

Hmm.  That could make sense.  In some cases, I was seeing it in files
(eg, /etc/group) that were recently modified.  I guess I didn't consider
that the editor may have created a new file, then renamed it over the
old (or opened it with O_TRUNC).

> Yes, I did mean sparse files.

I've definately seen it in non-sparse files.

-- John