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Message-ID: <7d687e10-32a8-1404-e714-4c6784e45f99@linux.alibaba.com>
Date:   Mon, 7 Aug 2023 17:42:10 +0800
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Subject: Re: [PATCH v3 4/8] mm/compaction: correct comment of
 fast_find_migrateblock in isolate_migratepages
To:     Kemeng Shi <shikemeng@huaweicloud.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        mgorman@techsingularity.net, david@redhat.com
References: <20230804110454.2935878-1-shikemeng@huaweicloud.com>
 <20230804110454.2935878-5-shikemeng@huaweicloud.com>
From:   Baolin Wang <baolin.wang@linux.alibaba.com>
In-Reply-To: <20230804110454.2935878-5-shikemeng@huaweicloud.com>
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On 8/4/2023 7:04 PM, Kemeng Shi wrote:
> After 90ed667c03fe5 ("Revert "Revert "mm/compaction: fix set skip in
> fast_find_migrateblock"""), we remove skip set in fast_find_migrateblock.
> Correct comment that fast_find_block is used to avoid isolation_suitable
> check for pageblock returned from fast_find_migrateblock because
> fast_find_migrateblock will mark found pageblock skipped.
> Instead, comment that fast_find_block is used to avoid a redundant check
> of fast found pageblock which is already checked skip flag inside
> fast_find_migrateblock.
> 
> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>

LGTM.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

> ---
>   mm/compaction.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 9a2f0bd5394a..4bf2dc936add 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1988,9 +1988,9 @@ static isolate_migrate_t isolate_migratepages(struct compact_control *cc)
>   		block_start_pfn = cc->zone->zone_start_pfn;
>   
>   	/*
> -	 * fast_find_migrateblock marks a pageblock skipped so to avoid
> -	 * the isolation_suitable check below, check whether the fast
> -	 * search was successful.
> +	 * fast_find_migrateblock() has already ensured the pageblock is not
> +	 * set with a skipped flag, so to avoid the isolation_suitable check
> +	 * below again, check whether the fast search was successful.
>   	 */
>   	fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail;
>