Re: JFFS3 & performance

Artem B. Bityuckiy
2005-01-13T15:05:16Z

On Thu, 13 Jan 2005, Artem B. Bityuckiy wrote:

> > > 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?
Hmm, only one small note, putting CRC to the end does not allow us to
recognize unclean reboots and flash media corruptions :-) But we still may
do this putting some majic bitmask to the end of nodes.

>
> --
> Best Regards,
> Artem B. Bityuckiy,
> St.-Petersburg, Russia.
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>

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