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Date:   Tue, 6 Aug 2019 06:35:03 -0700
From:   Matthew Wilcox <willy@infradead.org>
To:     Pingfan Liu <kernelfans@gmail.com>
Cc:     linux-mm@kvack.org,
        =?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        Jan Kara <jack@suse.cz>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Michal Hocko <mhocko@suse.com>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] mm/migrate: clean up useless code in
 migrate_vma_collect_pmd()
Message-ID: <20190806133503.GC30179@bombadil.infradead.org>
References: <1565078411-27082-1-git-send-email-kernelfans@gmail.com>
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This needs something beyond the subject line.  Maybe ...

After these assignments, we either restart the loop with a fresh variable,
or we assign to the variable again without using the value we've assigned.

Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

>  			goto next;
>  		}
> -		pfn = page_to_pfn(page);

After you've done all this, as far as I can tell, the 'pfn' variable is
only used in one arm of the conditions, so it can be moved there.

ie something like:

-               unsigned long mpfn, pfn;
+               unsigned long mpfn;
...
-               pfn = pte_pfn(pte);
...
+                       unsigned long pfn = pte_pfn(pte);
+