Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754281Ab3HBCbT (ORCPT ); Thu, 1 Aug 2013 22:31:19 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:15326 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751620Ab3HBCbS (ORCPT ); Thu, 1 Aug 2013 22:31:18 -0400 Message-ID: <51FB19D3.1090401@huawei.com> Date: Fri, 2 Aug 2013 10:30:43 +0800 From: Xishi Qiu User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20120428 Thunderbird/12.0.1 MIME-Version: 1.0 To: Cody P Schafer CC: Andrew Morton , Mel Gorman , Liujiang , Minchan Kim , Yasuaki Ishimatsu , , , LKML Subject: Re: [PATCH] mm/hotplug: fix a drain pcp bug when offline pages References: <51FA2800.9070706@huawei.com> <51FAB000.9050407@linux.vnet.ibm.com> In-Reply-To: <51FAB000.9050407@linux.vnet.ibm.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.74.196] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3754 Lines: 97 On 2013/8/2 2:59, Cody P Schafer wrote: > On 08/01/2013 02:18 AM, Xishi Qiu wrote: >> __offline_pages() >> start_isolate_page_range() >> set_migratetype_isolate() >> set_pageblock_migratetype() -> this pageblock will be marked as MIGRATE_ISOLATE >> move_freepages_block() -> pages in PageBuddy will be moved into MIGRATE_ISOLATE list >> drain_all_pages() -> drain PCP >> free_pcppages_bulk() >> mt = get_freepage_migratetype(page); -> PCP's migratetype is not MIGRATE_ISOLATE >> __free_one_page(page, zone, 0, mt); -> so PCP will not be freed into into MIGRATE_ISOLATE list >> >> In this case, the PCP may be allocated again, because they are not in >> PageBuddy's MIGRATE_ISOLATE list. This will cause offline_pages failed. >> >> Signed-off-by: Xishi Qiu >> --- >> mm/page_alloc.c | 10 ++++++---- >> mm/page_isolation.c | 15 ++++++++++++++- >> 2 files changed, 20 insertions(+), 5 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index b100255..d873471 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -965,11 +965,13 @@ int move_freepages(struct zone *zone, >> } >> >> order = page_order(page); >> - list_move(&page->lru, >> - &zone->free_area[order].free_list[migratetype]); >> - set_freepage_migratetype(page, migratetype); >> + if (get_freepage_migratetype(page) != migratetype) { >> + list_move(&page->lru, >> + &zone->free_area[order].free_list[migratetype]); >> + set_freepage_migratetype(page, migratetype); >> + pages_moved += 1 << order; >> + } >> page += 1 << order; >> - pages_moved += 1 << order; > > So this looks like it changes the return from move_freepages() to be the "pages moved" from "the pages now belonging to the passed migrate type". > > The user of move_freepages_block()'s return value (and thus the return value of move_freepages()) in mm/page_alloc.c expects that it is the original meaning. The users in page_isolation.c expect it is the new meaning. Those need to be reconciled. > >> } >> >> return pages_moved; >> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >> index 383bdbb..ba1afc9 100644 >> --- a/mm/page_isolation.c >> +++ b/mm/page_isolation.c >> @@ -65,8 +65,21 @@ out: >> } >> >> spin_unlock_irqrestore(&zone->lock, flags); >> - if (!ret) >> + >> + if (!ret) { >> drain_all_pages(); >> + /* >> + * When drain_all_pages() frees cached pages into the buddy >> + * system, it uses the stale migratetype cached in the >> + * page->index field, so try to move free pages to ISOLATE >> + * list again. >> + */ >> + spin_lock_irqsave(&zone->lock, flags); >> + nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE); >> + __mod_zone_freepage_state(zone, -nr_pages, migratetype); >> + spin_unlock_irqrestore(&zone->lock, flags); >> + } >> + > > Could we teach drain_all_pages() to use the right migrate type instead (or add something similar that does)? (pages could be reallocated between the drain_all_pages() and move_freepages_block()). > Sorry, I made a mistake. __test_page_isolated_in_pageblock() will catch the pages and move them into MIGRATE_ISOLATE list. So the code is right. Thanks, Xishi Qiu >> return ret; >> } >> > > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/