Re: [PATCH 4/5] writeback: remove pages_skipped accounting in__block_write_full_page()

From: Andrew Morton
Date: Thu Oct 04 2007 - 17:27:35 EST


On Tue, 02 Oct 2007 16:41:47 +0800
Fengguang Wu <wfg@xxxxxxxxxxxxxxxx> 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.

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