[dm-devel] Re: [PATCH resubmit] do_mount: reduce stack consumption
Neil Brown
neilb at suse.de
Sat Nov 5 05:37:01 UTC 2005
On Friday November 4, akpm at osdl.org wrote:
> 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.
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
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