Re: [PATCH 1/3] mm: tracking shared dirty pages

[Christoph Lameter]

On Thu, 25 May 2006, Jeff Anderson-Lee wrote:

> Christoph Lameter wrote:
> 
> > I am a bit confused about the need for Davids patch. set_page_dirty() is 
> > already a notification that a page is to be dirtied. Why do we need it 
> > twice? set_page_dirty could return an error code and the file system can 
> > use the set_page_dirty() hook to get its notification. What we would need 
> > to do is to make sure that set_page_dirty can sleep.
> 
> set_page_dirty() is actually called fairly late in the game by
> zap_pte_range() and follow_page().  Thus, it is a notification that a page
> HAS BEEN dirtied and needs a writeback.

The tracking patch changes that behavior. set_page_dirty is called before 
the write to the page occurs and so its similar to the new method 
introduced by David's patch.