Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758075Ab2HXJIq (ORCPT ); Fri, 24 Aug 2012 05:08:46 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:34991 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757496Ab2HXJIi (ORCPT ); Fri, 24 Aug 2012 05:08:38 -0400 MIME-Version: 1.0 In-Reply-To: <20120824080626.GC29282@dhcp22.suse.cz> References: <20120823095022.GB10685@dhcp22.suse.cz> <20120823135839.GB19968@dhcp22.suse.cz> <20120824080626.GC29282@dhcp22.suse.cz> Date: Fri, 24 Aug 2012 17:08:36 +0800 Message-ID: Subject: Re: Fixup the page of buddy_higher address's calculation From: Li Haifeng To: Michal Hocko Cc: Gavin Shan , Andrew Morton , Mel Gorman , Minchan Kim , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3603 Lines: 88 2012/8/24 Michal Hocko : > On Fri 24-08-12 10:08:20, Li Haifeng wrote: > [...] >> Subject: [PATCH] Fix the page address of higher page's buddy calculation >> >> Calculate the page address of higher page's buddy should be based >> higher_page with the offset between index of higher page and >> index of higher page's buddy. > > Sorry for insisting but could you add an information about when this has > been introduced (I have mentioned the commit in the other email) and the > effect of the bug so that we can consider whether this is worth > backporting to stable trees. > >> Signed-off-by: Haifeng Li >> Signed-off-by: Gavin Shan > > Other than that > Reviewed-by: Michal Hocko > >> --- >> mm/page_alloc.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index cdef1d4..642cd62 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -536,7 +536,7 @@ static inline void __free_one_page(struct page *page, >> combined_idx = buddy_idx & page_idx; >> higher_page = page + (combined_idx - page_idx); >> buddy_idx = __find_buddy_index(combined_idx, order + 1); >> - higher_buddy = page + (buddy_idx - combined_idx); >> + higher_buddy = higher_page + (buddy_idx - combined_idx); >> if (page_is_buddy(higher_page, higher_buddy, order + 1)) { >> list_add_tail(&page->lru, >> &zone->free_area[order].free_list[migratetype]); >> -- >> 1.7.5.4 > > -- > Michal Hocko > SUSE Labs I am sorry Michal. I misinterpreted what you mean. And the post blow is OK? ------------------------------------------> Subject: [PATCH] Fix the page address of higher page's buddy calculation The heuristic method for buddy has been introduced since 43506fad(mm/page_alloc.c: simplify calculation of combined index of adjacent buddy lists). But the page address of higher page's buddy was wrongly calculated, which will lead page_is_buddy to fail for ever. IOW, the heuristic method would be disabled with the wrong page address of higher page's buddy. Calculating the page address of higher page's buddy should be based higher_page with the offset between index of higher page and index of higher page's buddy. Signed-off-by: Haifeng Li Signed-off-by: Gavin Shan Reviewed-by: Michal Hocko --- mm/page_alloc.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ddbc17d..0754a3c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -579,7 +579,7 @@ static inline void __free_one_page(struct page *page, combined_idx = buddy_idx & page_idx; higher_page = page + (combined_idx - page_idx); buddy_idx = __find_buddy_index(combined_idx, order + 1); - higher_buddy = page + (buddy_idx - combined_idx); + higher_buddy = higher_page + (buddy_idx - combined_idx); if (page_is_buddy(higher_page, higher_buddy, order + 1)) { list_add_tail(&page->lru, &zone->free_area[order].free_list[migratetype]); -- 1.7.5.4 -- 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/