Re: [PATCH 2/2] mm/page_alloc: DEBUG_VM checks for free_list placement of CMA and RESERVE pages

[Joonsoo Kim]

On Thu, Apr 03, 2014 at 05:40:18PM +0200, Vlastimil Babka wrote:
> For the MIGRATE_RESERVE pages, it is important they do not get misplaced
> on free_list of other migratetype, otherwise the whole MIGRATE_RESERVE
> pageblock might be changed to other migratetype in try_to_steal_freepages().
> For MIGRATE_CMA, the pages also must not go to a different free_list, otherwise
> they could get allocated as unmovable and result in CMA failure.
> 
> This is ensured by setting the freepage_migratetype appropriately when placing
> pages on pcp lists, and using the information when releasing them back to
> free_list. It is also assumed that CMA and RESERVE pageblocks are created only
> in the init phase. This patch adds DEBUG_VM checks to catch any regressions
> introduced for this invariant.

Hello, Vlastimil.

Idea looks good to me.

> 
> Cc: Yong-Taek Lee <ytk.lee@xxxxxxxxxxx>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>
> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>
> Cc: Michal Nazarewicz <mina86@xxxxxxxxxx>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>

Acked-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
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