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From:   Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Date:   Mon, 19 Oct 2020 10:50:53 +0200
Message-ID: <CAM9Jb+iz3r3JeERmgvFeQfZ4vY7=TKtoXNEaDvmRPVAmhcyHnw@mail.gmail.com>
Subject: Re: [PATCH v2] mm/compaction: Rename 'start_pfn' to
 'iteration_start_pfn' in compact_zone()
To:     yanfei.xu@windriver.com
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        David Hildenbrand <david@redhat.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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> From: Yanfei Xu <yanfei.xu@windriver.com>
>
> There are two 'start_pfn' declared in compact_zone() which have
> different meaning. Rename the second one to 'iteration_start_pfn'
> to prevent trace_mm_compaction_end() from tracing an undesirable
> value.
>
> BTW, remove an useless semicolon.
>
> Acked-by: David Hildenbrand <david@redhat.com>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
> ---
> v1->v2:
> Rename 'start_pfn' to 'iteration_start_pfn' and change commit messages.
>
>  mm/compaction.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 176dcded298e..ccd27c739fd6 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -2272,7 +2272,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
>
>         while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) {
>                 int err;
> -               unsigned long start_pfn = cc->migrate_pfn;
> +               unsigned long iteration_start_pfn = cc->migrate_pfn;
>
>                 /*
>                  * Avoid multiple rescans which can happen if a page cannot be
> @@ -2284,7 +2284,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
>                  */
>                 cc->rescan = false;
>                 if (pageblock_start_pfn(last_migrated_pfn) ==
> -                   pageblock_start_pfn(start_pfn)) {
> +                   pageblock_start_pfn(iteration_start_pfn)) {
>                         cc->rescan = true;
>                 }
>
> @@ -2308,8 +2308,7 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
>                         goto check_drain;
>                 case ISOLATE_SUCCESS:
>                         update_cached = false;
> -                       last_migrated_pfn = start_pfn;
> -                       ;
> +                       last_migrated_pfn = iteration_start_pfn;
>                 }
>
>                 err = migrate_pages(&cc->migratepages, compaction_alloc,

Improves readability.
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>