On Thu, Dec 16, 2010 at 09:06:57AM +0900, KAMEZAWA Hiroyuki wrote: > On Wed, 15 Dec 2010 10:25:51 +0100 > Ingo Korb <ingo@xxxxxxxx> wrote: > > > On 15.12.2010 01:21, KAMEZAWA Hiroyuki wrote: > > > > > It's designed for offline memory section> MAX_ORDER. pageblock_nr_pages > > > is tend to be smaller than that. > > > > > > Do you see the problem with _exsisting_ user interface of memory hotplug ? > > > I think we have no control other than memory section. > > > > The existing, exported interface (remove_memory() - the check itself is > > in offline_pages()) only checks if both start and end of the > > to-be-removed block are aligned to pageblock_nr_pages. As you noted the > > actual size and alignment requirements in __offline_isolated_pages can > > be larger that that, so I think the checks in offline_pages() should be > > changed (if 1<<MAX_ORDER is always >= pageblock_nr_pages) or extended > > (if there can be any relation between the two). > > > > Ok, maybe my mistake. This is a fix. Thank you for reporting. > == > > offline_pages()'s sanity check of given range is wrong. It should > be aligned to MAX_ORDER. Current exsiting caller uses SECTION_SIZE > alignment, so this change has no influence to exsisting callers. > > Reported-by: Ingo Korb <ingo@xxxxxxxx> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Other than the spelling mistakes in the changelog and the lack of a subject; Acked-by: Mel Gorman <mel@xxxxxxxxx> > --- > mm/memory_hotplug.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > Index: linux-2.6.37-rc5/mm/memory_hotplug.c > =================================================================== > --- linux-2.6.37-rc5.orig/mm/memory_hotplug.c > +++ linux-2.6.37-rc5/mm/memory_hotplug.c > @@ -798,10 +798,14 @@ static int offline_pages(unsigned long s > struct memory_notify arg; > > BUG_ON(start_pfn >= end_pfn); > - /* at least, alignment against pageblock is necessary */ > - if (!IS_ALIGNED(start_pfn, pageblock_nr_pages)) > + /* > + * Considering buddy allocator which joins nearby pages, the range > + * in offline should be aligned to MAX_ORDER. If not, isolated > + * page will be joined to other (not isolated) pages. > + */ > + if (!IS_ALIGNED(start_pfn, MAX_ORDER_NR_PAGES)) > return -EINVAL; > - if (!IS_ALIGNED(end_pfn, pageblock_nr_pages)) > + if (!IS_ALIGNED(end_pfn, MAX_ORDER_NR_PAGES)) > return -EINVAL; > /* This makes hotplug much easier...and readable. > we assume this for now. .*/ > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>