linux-kernel - Re: [PATCH v2 2/2] mm/compaction: avoid rescanning pageblocks in isolate

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Message-ID: <alpine.DEB.2.02.1405211950430.13243@chino.kir.corp.google.com>
Date:	Wed, 21 May 2014 19:51:11 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Vlastimil Babka <vbabka@...e.cz>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Greg Thelen <gthelen@...gle.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Minchan Kim <minchan@...nel.org>,
	Mel Gorman <mgorman@...e.de>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH v2 2/2] mm/compaction: avoid rescanning pageblocks in
 isolate_freepages

On Mon, 19 May 2014, Vlastimil Babka wrote:

> Fix a (spurious) build warning:
> 
> mm/compaction.c:860:15: warning: ‘next_free_pfn’ may be used uninitialized in this function [-Wmaybe-uninitialized]
> 
> Seems like the compiler cannot prove that exiting the for loop without updating
> next_free_pfn there will mean that the check for crossing the scanners will
> trigger. So let's not confuse people who try to see why this warning occurs.
> 
> Instead of initializing next_free_pfn to zero with an explaining comment, just
> drop the damned variable altogether and work with cc->free_pfn directly as
> Nayoa originally suggested.
> 

s/Nayoa/Naoya/

> Suggested-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

Acked-by: David Rientjes <rientjes@...gle.com>