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

[Nick Piggin]

Andrew Morton wrote:
> Neil Brown <neilb@xxxxxxx> wrote:
>
> > ...
> > Reduce stack usage with stacked block devices
> >
> > ...
> > diff ./include/linux/sched.h~current~ ./include/linux/sched.h
> > --- ./include/linux/sched.h~current~	2005-11-07 10:01:36.000000000 +1100
> > +++ ./include/linux/sched.h	2005-11-07 10:02:23.000000000 +1100
> > @@ -829,6 +829,9 @@ struct task_struct {
> > /* journalling filesystem info */
> > 	void *journal_info;
> >
> > +/* stacked block device info */
> > +	struct bio *bio_list, **bio_tail;
> > +
> > /* VM state */
> > 	struct reclaim_state *reclaim_state;
>
>
> More state in the task_strut is a bit sad, but not nearly as sad as deep
> recursion in our deepest codepath..
>
> Possibly one could do:
>
> struct make_request_state {
> 	struct bio *bio_list;
> 	struct bio **bio_tail;
> };
>
> and stick a `struct make_request_state *' into the task_struct and actually
> allocate the thing on the stack.  That's not much nicer though.

Possibly it could go into struct io_context?

--
SUSE Labs, Novell Inc.

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