* Re: [patch 6/12] mm: remove bad_range
[not found] ` <1132662725.6696.45.camel@localhost>
@ 2005-11-23 2:09 ` Nick Piggin
0 siblings, 0 replies; only message in thread
From: Nick Piggin @ 2005-11-23 2:09 UTC (permalink / raw)
To: Dave Hansen
Cc: Linux Kernel Mailing List, Andrew Morton, Linux Memory Management
Dave Hansen wrote:
>
> I seem to also remember a case with this bad_range() check was useful
> for zones that don't have their boundaries aligned on a MAX_ORDER
> boundary. Would this change break such a zone? Do we care?
>
Hmm, I guess that would be covered by the:
if (page_to_pfn(page) >= zone->zone_start_pfn + zone->spanned_pages)
return 1;
if (page_to_pfn(page) < zone->zone_start_pfn)
return 1;
checks in bad_range. ISTR some "warning: zone not aligned, kernel
*will* crash" message got printed in that case. I always thought
that zones were supposed to be MAX_ORDER aligned, but I can see how
that restriction might be relaxed with these checks in place.
This commit introduced the change:
http://www.kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commitdiff;h=d60c9dbc4589766ef5fe88f082052ccd4ecaea59
I think this basically says that architectures who care need to define
CONFIG_HOLES_IN_ZONE and handle this in pfn_valid.
Unless this is a very common requirement and such a solution would have
too much performance cost? Anyone?
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