JFFS2 error messages

[David Woodhouse]

On Tue, 2008-06-03 at 12:13 -0400, C. Scott Ananian wrote:
> 2008/6/3 Bill Mccormick <billmcc at nortel.com>:
> > A couple of my XOs are reporting what look like FS error messages on boot:
> >
> > [91.463670] JFFS2 notice:  (664) check_node_data:  wrong data CRC in data
> > node at 0x1ec215f0: read 0x3e7c7e03, calculated 0xf7e1d50c
> > ...
> >
> > is this a known problem?
> 
> According to Dave Woodhouse, who wrote JFFS2, these notices typically
> mean that at some point you've hard powered off, and as a result JFFS
> has some uncommitted data lying around on flash.  It's almost always
> harmless, a part of the journal which was never committed: "either it
> was a new write which hadn't yet been synced, or it was a GC write
> which just doesn't achieve anything now."  However, these messages
> *could* indicate an actual problem -- "we never came up with a good
> heuristic for when _not_ to complain".  Woodhouse suggests that in the
> future "perhaps we should write a 'yes, I know there's a CRC failure'
> node _after_ the offending node, when we reboot and find it" since
> directly rewriting the node is not an option due to the mechanics of
> NAND flash; that would help confine these messages to immediately
> after a hard reboot.  At present, you'll keep seeing a "bad CRC"
> message every time that particular JFFS node is accessed until it is
> eventually GC'ed.
> 
> Anyone want to volunteer to turn the above into a FAQ which would be
> discoverable on our wiki, so that future wonderers don't have to pry
> the information from the head of dwmw2?

I think it's already in trac as an RFE.

I even respond to email about it when the email in question isn't HTML.

-- 
dwmw2