Re: JFFS3 & performance

Artem B. Bityuckiy
2005-01-13T14:49:40Z

> > P.S. By the way, we could put CRCs at the end of blocks (*after* data)
> > in this case CRC well be extremely strong detecting unclean reboots,
> > isn't it?
>
> Interesting idea. Will make the code slightly messy, but it should be
> worth it.
Now I like this Idea more.

See the benefits:
1. We are able to use weaker then CRC32 checksums and still be good in
detecting wrong due to unclean reboot nodes.
2. We have principal ability to distingush between nodes corrupted due to
flash problems and due to unclean reboots.
This is extreemly good do be able to distinguish. (JFFS2 has no such
ability).

Examples:
a. We will not print frightfull messges like "CRC ERROR!!!!
You'ra going to die!" and will not make users worry if the error was
cased by unclean reboot. Unclean reboots is qute frequent thing.
b. When do iget() on file and see corrupted nodes, we just ignore
them if they are due to unclean reboot. But we return -EIO if they are due
to flash corruptions. Currently JFFS2 happily ignores corrupted nodes and
still keeps working with the corrupted file. That is no good.
It is better, for example, to regect opening corrupted /lib/libc.o then
just open but corrupted file.

Thoughts?

--
Best Regards,
Artem B. Bityuckiy,
St.-Petersburg, Russia.