[lug] Rather disturbing

[Zan Lynx]

On Thu, 2004-02-26 at 15:41, Gary Hodges wrote:
> I reset my computer today after it hung up and I've noted two problems 
> since the reboot.
> 
> 1.  All my opera bookmarks and settings look to be the default values.  
> Actually, now that I'm looking again, there are no bookmarks at all.
> 
> 2.  I ran tin to check some news and the listed newsgroups I subscribe 
> to had changed to partial lines of data from a data file I recognize. 
> 
> SuSE 9.0 w/ReiserFS
> 
> Wow, what else happened?  Luckily I write to tape every night, so if 
> that process has been working I should be OK, but I guess I'm a little 
> surprised a journaling FS seems to have gotten pretty screwed up.

Reiser version 3 journals meta-data but not data.  There are patches
(which may be in SuSE 9, I don't know) to make Reiser journal in ordered
mode (write the data FIRST and then update meta-data), or even full data
journaling (very slow).

The meta-data only journalling means that your directories, file types
and names and permissions, things like that will be fine, but the actual
contents of files that were being modified during the crash may be
indeterminate.

What probably happened is that your bookmark file was being updated and
the filesystem had allocated some new blocks to it, but hadn't actually
written anything into those new blocks yet.  So, those new blocks
contained data from another older file.

This is pretty common for meta-data journaling filesystems.  XFS does it
too, although it tends to create files full of zeros instead of random
data.
-- 
Zan Lynx <zlynx at acm.org>
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