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

[Neil Brown <neilb suse de>]

On Friday November 4, akpm osdl org wrote:
> cplk 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.

Ok, I'll dust it off, make sure it seems to work (at the time I first
wrote it, I think it caused 'md' to deadlock) and submit it.

NeilBrown