Re: [PATCH] memory hotplug: fix page_zone() calculation in test_pages_isolated()

KAMEZAWA Hiroyuki
2008-10-30T00:10:29Z

On Wed, 29 Oct 2008 15:25:30 +0100
Gerald Schaefer <gerald.schaefer@de.ibm.com> wrote:

> From: Gerald Schaefer <gerald.schaefer@de.ibm.com>
>
> My last bugfix here (adding zone->lock) introduced a new problem: Using
> page_zone(pfn_to_page(pfn)) to get the zone after the for() loop is wrong.
> pfn will then be >= end_pfn, which may be in a different zone or not
> present at all. This may lead to an addressing exception in page_zone()
> or spin_lock_irqsave().
>
> Now I use __first_valid_page() again after the loop to find a valid page
> for page_zone().
>
> Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
>
Thanks.

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

> ---
> mm/page_isolation.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/mm/page_isolation.c
> ===================================================================
> --- linux-2.6.orig/mm/page_isolation.c
> +++ linux-2.6/mm/page_isolation.c
> @@ -130,10 +130,11 @@ int test_pages_isolated(unsigned long st
> if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
> break;
> }
> - if (pfn < end_pfn)
> + page = __first_valid_page(start_pfn, end_pfn - start_pfn);
> + if ((pfn < end_pfn) || !page)
> return -EBUSY;
> /* Check all pages are free or Marked as ISOLATED */
> - zone = page_zone(pfn_to_page(pfn));
> + zone = page_zone(page);
> spin_lock_irqsave(&zone->lock, flags);
> ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn);
> spin_unlock_irqrestore(&zone->lock, flags);