Upgrading cramfs root file system while running (DENX wrote that is not possible)

[Antonio Di Bacco]

How can I mark some RAM unusable by Linux at runtime? I know that it could be 
done before booting but not runtime.

Bye,
Antonio.

On Thursday 20 April 2006 23:03, Antonio Di Bacco wrote:
> Yes, I also thought this too. Anything important should stay already in RAM
> but there is a chance that something bad could happen. Probably the best
> thing is what you suggested as second option but I have not so much ram. My
> CGI writes the downloaded new software in RAM and then I should directly
> jump to u-boot without leaving Linux the chance to mix things up and then
> u-boot should copy the RAM to the flash. It seems a strange procedure but
> what else could be done with 4MB flash and 16 MB ram?
>
> Bye,
> Antonio.
>
> On Thursday 20 April 2006 22:18, White wrote:
> > make it easy: if you start an application which do the flash and after
> > this a reset.. nothing should happen. I do it that way.
> > the application resist completly in RAM .. and all important libs are
> > in RAm or in Filesystem Cache.
> > It's only important that you pretend any Application from accessing
> > Datafiles or start of new application ...
> >
> > Alternativly, you can put it in a reserved RAM Area ( mark it not
> > usable by Linux) and put a Flash Code in your Bootloader (U-boot?)
> > after a reset....
> >
> > But overwrite a cramfs works for me on >100 times without problems.
> >
> > Am Thu, 20 Apr 2006 21:54:45 +0200 schrieb Antonio Di Bacco
> >
> > <antonio.dibacco at aruba.it> :
> > > Yes you are right, it is not a good idea to overwrite working cramfs
> > > filesystem. But what happens if I download the new cramfs plus kernel
> > > in RAM, do a checksum and then, completely in kernel mode, disabling
> > > all the interrupts, I write to flash? No process could complain that I
> > > am overwriting because no one is executing.
> > >
> > > Bye,
> > > Antonio.
> > >
> > > On Wednesday 19 April 2006 09:42, Wojciech Kromer wrote:
> > > > Dnia 2006-04-06 22:38, Użytkownik Antonio Di Bacco napisał:
> > > > > Hi,
> > > > >
> > > > > how could I upgrade my cramfs rootfs? I have a CGI in the rootfs
> > > > > that receives the new rootfs from a web interface and then tries to
> > > > > write it in the flash. While overwriting the old cramfs, the CGI
> > > > > will continue to work? something weird could happen?
> > > >
> > > > Generally it's not a good idea to override working filesystem ( I've
> > > > tried to do it once).
> > > >
> > > > You can have two separate copies of filesystem, one to work with, and
> > > > another to overwrite, it requires more flash.
> > > > Another way is working in initrd, it requires more RAM.
> > > > You can also use jffs2 or jffs3 (experimental) to have read-write
> > > > filesystem, and change applications only, not whole filesystem (be
> > > > carefull with changing busybox or libraries!)
> > >
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