Re: Warning on memory offline (and possible in usual migration?)

[Nick Piggin <npiggin@suse.de>]

On Tue, Apr 29, 2008 at 04:20:16PM +0900, KAMEZAWA Hiroyuki wrote:
> I myself want to this patch to be included (to next -mm) and put this under
> test. How do you think ? Nick ? Christoph ?

I think it should go upstream, yes. I imagine Andrew is probably just busy
with merging at the moment. I guess we should resubmit if it isn't picked
up in the next few days.

Thanks,
Nick

> 
> Thanks,
> -Kame
> 
> 
> On Wed, 23 Apr 2008 02:48:04 +0200
> Nick Piggin <npiggin@suse.de> wrote:
> > What was happening is that migrate_page_copy wants to transfer the PG_dirty
> > bit from old page to new page, so what it would do is set_page_dirty(newpage).
> > However set_page_dirty() is used to set the entire page dirty, wheras in
> > this case, only part of the page was dirty, and it also was not uptodate.
> > 
> > Marking the whole page dirty with set_page_dirty would lead to corruption or
> > unresolvable conditions -- a dirty && !uptodate page and dirty && !uptodate
> > buffers.
> > 
> > Possibly we could just ClearPageDirty(oldpage); SetPageDirty(newpage);
> > however in the interests of keeping the change minimal...
> > 
> > Signed-off-by: Nick Piggin <npiggin@suse.de>
> > ---
> > Index: linux-2.6/mm/migrate.c
> > ===================================================================
> > --- linux-2.6.orig/mm/migrate.c
> > +++ linux-2.6/mm/migrate.c
> > @@ -383,7 +383,14 @@ static void migrate_page_copy(struct pag
> >  
> >  	if (PageDirty(page)) {
> >  		clear_page_dirty_for_io(page);
> > -		set_page_dirty(newpage);
> > +		/*
> > +		 * Want to mark the page and the radix tree as dirty, and
> > +		 * redo the accounting that clear_page_dirty_for_io undid,
> > +		 * but we can't use set_page_dirty because that function
> > +		 * is actually a signal that all of the page has become dirty.
> > +		 * Wheras only part of our page may be dirty.
> > +		 */
> > +		__set_page_dirty_nobuffers(newpage);
> >   	}
> >  
> >  #ifdef CONFIG_SWAP

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