Re: [PATCH 1/1] ipc/shm: fix the historical/wrong mm->start_stack check

[Oleg Nesterov <oleg@redhat.com>]

On 08/25, Hugh Dickins wrote:
>
> On Mon, 25 Aug 2014, Oleg Nesterov wrote:
> > On 08/25, Hugh Dickins wrote:
> >
> > > And I think I'll let Linus's guard page justify your 4 (to match comment)
> > > in place of the original's mysterious 5.
> >
> > Ah, thanks again. Yes, if we want to guarantee 4 pages we should check 5.
> >
> > Although obviously this doesn't explain the original's 5, this was
> > written before check_stack_guard_page().
>
> I meant, you changed the coded 5 to 4, to match the comment above it;
> and if I were insistent on maximizing back-compatible-safety, I would
> say that 4 should go back to 5;

I already did this ;) I'll send v2 patch in a minute.

> But I didn't understand your "to guarantee 4 we should check 5".

I just tried to say that I fully agree with your point.

I didn't dare to preserve your acks although the patch is almost the
same, I'll appreciate it if you can ack v2 too.

Oleg.