linux-kernel - Re: [patch 7/7] powerpc: lockless get_user_pages

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Message-ID: <20080611031822.GA8228@wotan.suse.de>
Date:	Wed, 11 Jun 2008 05:18:22 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Christoph Lameter <clameter@....com>
Cc:	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	benh@...nel.crashing.org, paulus@...ba.org
Subject: Re: [patch 7/7] powerpc: lockless get_user_pages_fast

On Tue, Jun 10, 2008 at 12:00:48PM -0700, Christoph Lameter wrote:
> On Thu, 5 Jun 2008, npiggin@...e.de wrote:
> 
> > Index: linux-2.6/include/linux/mm.h
> > ===================================================================
> > --- linux-2.6.orig/include/linux/mm.h
> > +++ linux-2.6/include/linux/mm.h
> > @@ -244,7 +244,7 @@ static inline int put_page_testzero(stru
> >   */
> >  static inline int get_page_unless_zero(struct page *page)
> >  {
> > -	VM_BUG_ON(PageTail(page));
> > +	VM_BUG_ON(PageCompound(page));
> >  	return atomic_inc_not_zero(&page->_count);
> >  }
> 
> This is reversing the modification to make get_page_unless_zero() usable 
> with compound page heads. Will break the slab defrag patchset.

Is the slab defrag patchset in -mm? Because you ignored my comment about
this change that assertions should not be weakened until required by the
actual patchset. I wanted to have these assertions be as strong as
possible for the lockless pagecache patchset.


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