Panic in recent 7.2-Stable

[Kostik Belousov]

On Sun, Sep 06, 2009 at 05:37:52PM +0200, A.J. Fonz van Werven wrote:
> Kostik Belousov wrote:
> 
> > I expect that the following patch, that is the partial merge of r194459,
> > would fix it. It patches sys/vm/vm_phys.c.
> > 
> > Index: vm_phys.c
> > ===================================================================
> > --- vm_phys.c	(revision 194458)
> > +++ vm_phys.c	(revision 194459)
> > @@ -382,8 +382,7 @@
> >  		if (pa >= seg->start && pa < seg->end)
> >  			return (&seg->first_page[atop(pa - seg->start)]);
> >  	}
> > -	panic("vm_phys_paddr_to_vm_page: paddr %#jx is not in any segment",
> > -	    (uintmax_t)pa);
> > +	return (NULL);
> >  }
> >  
> >  /*
> 
> Hi,
> 
> A quick grep on the file in question revealed that there are two
> functions that may panic() with "page not in any segment": the
> vm_phys_paddr_to_vm_page() being patched and also the next function
> vm_phys_paddr_to_segind(). I'm not exactly current with the memory
> management code so this may be a very stupid question, but I'll ask it
> anyway: don't both functions need to be patched?

vm_phys_paddr_to_segind is used during vm bootstrap, the call sequence
is vm_page_startup->vm_phys_add_page->vm_phys_paddr_to_segind.

vm_page_startup calls vm_phys_add_page only for pages
that should not cause the mentioned panic in vm_phys_paddr_to_segind,
since it iterates over the pages of the segments created by
vm_phys_create_seg() in vm_phys_init().
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