linux-kernel - Re: [patch 0/3] 2.6.20 fix for PageUptodate memorder problem (try 3)

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Message-Id: <1171147495.31563.5.camel@localhost>
Date:	Sat, 10 Feb 2007 23:44:55 +0100
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Andrew Morton <akpm@...l.org>, Hugh Dickins <hugh@...itas.com>,
	Linux Memory Management <linux-mm@...ck.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch 0/3] 2.6.20 fix for PageUptodate memorder problem (try
	3)

On Sat, 2007-02-10 at 03:31 +0100, Nick Piggin wrote:
> SetNewPageUptodate does not do the S390 page_test_and_clear_dirty, so
> I'd like to make sure that's OK.

An I/O operation on s390 will set the dirty bit for a page. That is the
reason to have SetPageUptodate clear the per page dirty bit when the
page is made uptodate the first time. Otherwise we end up writing each
page back to its backing device at least once. If SetNewPageUptodate is
used on new anonymous pages exclusively I don't see a problem in
omitting the page_test_clear_dirty.

-- 
blue skies,
  Martin.

Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH

"Reality continues to ruin my life." - Calvin.

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