Re: [PATCH 4/4] mm/compaction: respect ignore_skip_hint in update_pageblock_skip

[Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>]

On Fri, Dec 06, 2013 at 05:41:50PM +0900, Joonsoo Kim wrote:
> update_pageblock_skip() only fits to compaction which tries to isolate by
> pageblock unit. If isolate_migratepages_range() is called by CMA, it try to
> isolate regardless of pageblock unit and it don't reference
> get_pageblock_skip() by ignore_skip_hint. We should also respect it on
> update_pageblock_skip() to prevent from setting the wrong information.
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Yes, get/set_pageblock_skip() is irrelevant if ignore_skip_hint is true.
This bug was introduced in v3.7-rc, so this patch would go to stable-3.7
and later.

Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

Thanks,
Naoya

> diff --git a/mm/compaction.c b/mm/compaction.c
> index 805165b..f58bcd0 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -134,6 +134,10 @@ static void update_pageblock_skip(struct compact_control *cc,
>  			bool migrate_scanner)
>  {
>  	struct zone *zone = cc->zone;
> +
> +	if (cc->ignore_skip_hint)
> +		return;
> +
>  	if (!page)
>  		return;
>  
> -- 
> 1.7.9.5
> 
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