[dm-devel] Re: [PATCH resubmit] do_mount: reduce stack consumption

[Andrew Morton]

cplk at itee.uq.edu.au wrote:
>
> > > > This part of the call trace is actually good for >1500 bytes of stack
> > > > usage and is what kills us and should be fixed.
> > > > I'm surprised that there are no other bug reports regarding DM and
> > > > stack overflow with 4k stacks.
> > > >...
> > > 
> > > There were some reports of dm+xfs overflows with 4k stacks on i386.
> > > 
> > > The xfs side was sorted out, but I son't know the state of the dm part.
> > > 
> > 
> > The state is Very Bad, IMO.  At the very least, DM should struggle to the
> > utmost to reduce the stack utilisation around that recursion point.
> 
> Neil Brown suggested a change to generic_make_request to convert recursion 
> through it into iteration (see http://lkml.org/lkml/2005/9/2/34 ), but 
> there was no discussion at the time.  Would this help with this case?

It certainly would.  That looks like a good thing to do some more work on.