linux-kernel - Re: [PATCH 0/2 v2] Make is_mem_section_removable more conformable with offlining code

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Message-ID: <20100903075437.GB10686@tiehlicka.suse.cz>
Date:	Fri, 3 Sep 2010 09:54:38 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Hiroyuki Kamezawa <kamezawa.hiroyuki@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kleen, Andi" <andi.kleen@...el.com>,
	Haicheng Li <haicheng.li@...ux.intel.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mel Gorman <mel@...ux.vnet.ibm.com>
Subject: Re: [PATCH 0/2 v2] Make is_mem_section_removable more conformable
 with offlining code

On Fri 03-09-10 12:10:03, KAMEZAWA Hiroyuki wrote:
> On Thu, 2 Sep 2010 17:05:54 +0200
> Michal Hocko <mhocko@...e.cz> wrote:
> 
> >  extern int mem_online_node(int nid);
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index a4cfcdc..2b736ed 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -569,16 +569,25 @@ out:
> >  EXPORT_SYMBOL_GPL(add_memory);
> >  
> >  #ifdef CONFIG_MEMORY_HOTREMOVE
> > +
> >  /*
> > - * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
> > - * set and the size of the free page is given by page_order(). Using this,
> > - * the function determines if the pageblock contains only free pages.
> > - * Due to buddy contraints, a free page at least the size of a pageblock will
> > - * be located at the start of the pageblock
> > + * A free or LRU pages block are removable
> > + * Do not use MIGRATE_MOVABLE because it can be insufficient and
> > + * other MIGRATE types are tricky.
> >   */
> > -static inline int pageblock_free(struct page *page)
> > -{
> > -	return PageBuddy(page) && page_order(page) >= pageblock_order;
> > +bool is_page_removable(struct page *page)
> > +{
> > +	int page_block = 1 << pageblock_order;
> > +	while (page_block > 0) {
> > +		if (PageBuddy(page)) {
> > +			page_block -= page_order(page);
> > +		} else if (PageLRU(page))
> > +			page_block--;
> > +		else 
> > +			return false;
> > +	}
> 
> still seems wrong..."page" pointer should be updated.

You are right. I should have double checked that (never send patches
before leaving from the office...).

-- 
Michal Hocko
L3 team 
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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