Re: I request inclusion of reiser4 in the mainline kernel

Theodore Ts'o
2005-09-21T00:04:54Z

On Tue, Sep 20, 2005 at 09:51:33AM +0200, Pavel Machek wrote:
> Do you have working fsck for V4? Until then, you should not claim that
> users should switch. Journalling does not help you, if you have
> unexpected kernel problem or hardware trouble, fsck _is_ mandatory.
>
> Can V4 survive few hours of test below?

The script could be improved by select random locations to damage the
filesystem, instead of hard-coding the seek=7 value. Seek=7 is good
for testing ext2/ext3 filesystems, but it may not be ideal for other
filesystems.

Another interesting refinement would be to analyze the resulting
filesystem after it has been repaired to determine how much data could
be salvaged by the fsck program.

There is a very interesting paper that I coincidentally just came
across today that talks about making filesystems robust against
various different forms of failures of modern disk systems. It is
going to be presented at the upcoming 2005 SOSP conference.

http://www.cs.wisc.edu/adsl/Publications/iron-sosp05.pdf

It's definitely worth a read. A few comments about it; first of all,
I know nothing about this modified "iron ext3" (ixt3) discussed in the
paper aside from what's the paper itself. It would be interesting to
see what they have done with it. Secondly, I _think_ sct has already
fixed the problems discussed in the paper with respect to inadequate
write squelching after an I/O failure writing to the ext3 journal, but
we need to chat with the paper's authors to confirm that, and if there
still is a problem, obviously we need to fix it. Third of all, I'll
note that the paper does takes an approving note of the fact that
Reiserfs (v3) always panic's when it detects a write fault, so for
those folks in the Reiser team who might have a persecution complex,
relax, the whole world isn't out to get you. :-)

- Ted