Message-Id: <6.0.0.20.2.20070914162337.037e82e0@172.19.0.2>
Date: Fri, 14 Sep 2007 16:42:01 +0900
To: Andrew Morton <akpm@linux-foundation.org>
From: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Subject: Re: [PATCH] mm: use pagevec to rotate reclaimable page
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org
In-Reply-To: <20070913193711.ecc825f7.akpm@linux-foundation.org>
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 <20070913193711.ecc825f7.akpm@linux-foundation.org>
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Thank you for your comment.

At 11:37 07/09/14, Andrew Morton wrote:

 >The page_count() test here is a bit of a worry, too.  Why do we need it?
 >The caller must have pinned the page in some fashion else we couldn't use
 >it safely in this function at all.
 >
 >I assume that you discovered that once we've cleared PageWriteback(), the
 >page can get reclaimed elsewhere?  If so, that could still happen
 >immediately after the page_count() test.  It's all a bit of a worry.
 >Deferring the ClearPageWriteback() will fix any race concerns, but I do
 >think that we need to take a ref on the page for the pagevec ownership.
 >

Actually, I considered taking a ref to pin pages. But this could prevent 
the page
reclaiming activity so I did not use it.

I reflect your comment and send you modified patch.

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