Date: Thu, 4 Oct 2007 14:26:41 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: linux-kernel@vger.kernel.org, dgc@sgi.com, kenchen@google.com,
       mrubin@google.com
Subject: Re: [PATCH 4/5] writeback: remove pages_skipped accounting in
 __block_write_full_page()
Message-Id: <20071004142641.9de1ef66.akpm@linux-foundation.org>
In-Reply-To: <391315778.53500@ustc.edu.cn>
References: <20071002084143.110486039@mail.ustc.edu.cn>
	<391315778.53500@ustc.edu.cn>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 836
Lines: 19

On Tue, 02 Oct 2007 16:41:47 +0800
Fengguang Wu <wfg@mail.ustc.edu.cn> wrote:

> This patch fixes this bug. Though I'm not sure why __block_write_full_page()
> is called only to do nothing and who actually issued the writeback for us.

kjourald wrote the page's buffers back (ext3 in ordered-data mode).  The VM
didn't know about that, so we have a PageDirty page which has clean
buffers.

We rely upon the VFS writeback code to "discover" that this dirty page has
clean buffers: the VFS will attempt to write the dirty page and will end up
marking the page clean without performing any IO.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/