linux-kernel - Re: [PATCH 1/3] mm/migrate: clean up useless code in migrate_vma_collect

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Message-ID: <20190807052858.GA9749@mypc>
Date:   Wed, 7 Aug 2019 13:28:58 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-mm@...ck.org,
        Jérôme Glisse <jglisse@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Jan Kara <jack@...e.cz>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mm/migrate: clean up useless code in
 migrate_vma_collect_pmd()

On Tue, Aug 06, 2019 at 06:35:03AM -0700, Matthew Wilcox wrote:
> 
> 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@...radead.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);
> +
> 
This makes code better. Thank you for the suggestion. Will send v2 for
this patch.

Regards,
	Pingfan