linux-kernel - Re: [PATCH 4.6 1/3] mm, cma: prevent nr_isolated

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Message-ID: <20160427005718.GB6336@js1304-P5Q-DELUXE>
Date:	Wed, 27 Apr 2016 09:57:18 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michal Hocko <mhocko@...e.com>,
	Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>, stable@...r.kernel.org
Subject: Re: [PATCH 4.6 1/3] mm, cma: prevent nr_isolated_* counters from
 going negative

On Mon, Apr 25, 2016 at 03:35:48PM +0200, Vlastimil Babka wrote:
> From: Hugh Dickins <hughd@...gle.com>
> 
> /proc/sys/vm/stat_refresh warns nr_isolated_anon and nr_isolated_file
> go increasingly negative under compaction: which would add delay when
> should be none, or no delay when should delay. The bug in compaction was
> due to a recent mmotm patch, but much older instance of the bug was also
> noticed in isolate_migratepages_range() which is used for CMA and
> gigantic hugepage allocations.
> 
> The bug is caused by putback_movable_pages() in an error path decrementing
> the isolated counters without them being previously incremented by
> acct_isolated(). Fix isolate_migratepages_range() by removing the error-path
> putback, thus reaching acct_isolated() with migratepages still isolated, and
> leaving putback to caller like most other places do.
> 
> [vbabka@...e.cz: expanded the changelog]
> Fixes: edc2ca612496 ("mm, compaction: move pageblock checks up from isolate_migratepages_range()")
> Cc: stable@...r.kernel.org
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

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

Thanks.