Date: Wed, 16 Apr 2014 10:09:17 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Mel Gorman <mgorman@suse.de>, Yong-Taek Lee <ytk.lee@samsung.com>,
        Minchan Kim <minchan@kernel.org>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Hugh Dickins <hughd@google.com>, Rik van Riel <riel@redhat.com>,
        Michal Nazarewicz <mina86@mina86.com>
Subject: Re: [PATCH 2/2] mm/page_alloc: DEBUG_VM checks for free_list
 placement of CMA and RESERVE pages
Message-ID: <20140416010917.GA17653@js1304-P5Q-DELUXE>
References: <533D8015.1000106@suse.cz>
 <1396539618-31362-1-git-send-email-vbabka@suse.cz>
 <1396539618-31362-2-git-send-email-vbabka@suse.cz>
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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@samsung.com>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Michal Nazarewicz <mina86@mina86.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

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