Date: Wed, 27 Apr 2016 09:57:18 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Michal Hocko <mhocko@suse.com>,
        Hugh Dickins <hughd@google.com>, Rik van Riel <riel@redhat.com>,
        stable@vger.kernel.org
Subject: Re: [PATCH 4.6 1/3] mm, cma: prevent nr_isolated_* counters from
 going negative
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On Mon, Apr 25, 2016 at 03:35:48PM +0200, Vlastimil Babka wrote:
> From: Hugh Dickins <hughd@google.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@suse.cz: expanded the changelog]
> Fixes: edc2ca612496 ("mm, compaction: move pageblock checks up from isolate_migratepages_range()")
> Cc: stable@vger.kernel.org
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

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

Thanks.