Re: ramdisk driver in 2.6.6 has a severe bug

[Robert M. Stockmann]

On Mon, 17 May 2004, Andrew Morton wrote:

> "Robert M. Stockmann" <stock@xxxxxxxxxxx> wrote:
> >
> > Be aware of other problems when using the linux ramdisk driver,
> > loosing its contents. Especially the use of mkinitrd might result in 
> > unexpected problems. googling for "kernel 2.6.6 ramdisk problem" shows lots
> > of people with problems mounting their root filesystems and loading modules
> > from ramdisk. Klaus Knopper (knoppix) is not amused, neither am i :)
> 
> Well in that case perhaps something else broke.  I've seen no such reports
> of recent regressions in the ramdisk driver.
> 
> The two problems of which I am aware are:
> 
> a) It loses its brains across umount.  Seems that it's very rare that
>    anyone actually cares about this, which is why it has not been fixed in
>    well over a year.
> 
> b) It loses data under heavy I/O loads.  I _think_ this has been
>    observed only on ppc64 and might be a cache writeback/invalidate thing.
> 
> If there are new post-2.6.5 problems then I'm all ears.

Well i think a problem has risen due to people allocating huge ramdisks with
sizes over 128Mb RAM. This is biting into the virtual memory management
system. For people using the ramdisk driver as a permanent runtime
root filesystem, maybe create a boot option : 

ramdisk=persistent	(or =solid or =sticky )

Robert
-- 
Robert M. Stockmann - RHCE
Network Engineer - UNIX/Linux Specialist
crashrecovery.org  stock@xxxxxxxxxxx

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