Re: [PATCH 03/15] mm: compaction: introduce isolate_migratepages_range().

Mel Gorman
2012-01-30T13:25:46Z

On Mon, Jan 30, 2012 at 01:42:50PM +0100, Michal Nazarewicz wrote:
> >On Thu, Jan 26, 2012 at 10:00:45AM +0100, Marek Szyprowski wrote:
> >>From: Michal Nazarewicz <mina86@mina86.com>
> >>@@ -313,7 +316,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
> >> } else if (!locked)
> >> spin_lock_irq(&zone->lru_lock);
> >>
> >>- if (!pfn_valid_within(low_pfn))
> >>+ if (!pfn_valid(low_pfn))
> >> continue;
> >> nr_scanned++;
> >>
>
> On Mon, 30 Jan 2012 12:24:28 +0100, Mel Gorman <mel@csn.ul.ie> wrote:
> >This chunk looks unrelated to the rest of the patch.
> >
> >I think what you are doing is patching around a bug that CMA exposed
> >which is very similar to the bug report at
> >http://www.spinics.net/lists/linux-mm/msg29260.html . Is this true?
> >
> >If so, I posted a fix that only calls pfn_valid() when necessary. Can
> >you check if that works for you and if so, drop this hunk please? If
> >the patch does not work for you, then this hunk still needs to be
> >in a separate patch and handled separately as it would also be a fix
> >for -stable.
>
> I'll actually never encountered this bug myself and CMA is unlikely to
> expose it, since it always operates on continuous memory regions with
> no holes.
>
> I've made this change because looking at the code it seemed like this
> may cause problems in some cases. The crash that you linked to looks
> like the kind of problem I was thinking about.
>
> I'll drop this hunk and let you resolve this independently of CMA.
>

Ok, thanks.

--
Mel Gorman
SUSE Labs