Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753246AbaGGOvI (ORCPT ); Mon, 7 Jul 2014 10:51:08 -0400 Received: from cantor2.suse.de ([195.135.220.15]:33500 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751005AbaGGOvF (ORCPT ); Mon, 7 Jul 2014 10:51:05 -0400 Message-ID: <53BAB3D3.6060603@suse.cz> Date: Mon, 07 Jul 2014 16:50:59 +0200 From: Vlastimil Babka User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Joonsoo Kim , Andrew Morton CC: "Kirill A. Shutemov" , Rik van Riel , Peter Zijlstra , Mel Gorman , Johannes Weiner , Minchan Kim , Yasuaki Ishimatsu , Zhang Yanfei , "Srivatsa S. Bhat" , Tang Chen , Naoya Horiguchi , Bartlomiej Zolnierkiewicz , Wen Congyang , Marek Szyprowski , Michal Nazarewicz , Laura Abbott , Heesub Shin , "Aneesh Kumar K.V" , Ritesh Harjani , t.stanislaws@samsung.com, Gioh Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 02/10] mm/page_alloc: correct to clear guard attribute in DEBUG_PAGEALLOC References: <1404460675-24456-1-git-send-email-iamjoonsoo.kim@lge.com> <1404460675-24456-3-git-send-email-iamjoonsoo.kim@lge.com> In-Reply-To: <1404460675-24456-3-git-send-email-iamjoonsoo.kim@lge.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/04/2014 09:57 AM, Joonsoo Kim wrote: > In __free_one_page(), we check the buddy page if it is guard page. > And, if so, we should clear guard attribute on the buddy page. But, > currently, we clear original page's order rather than buddy one's. > This doesn't have any problem, because resetting buddy's order > is useless Well it might theoretically confuse someone examining a crash dump, to see an unexpected page->private value. So I agree it should be corrected. > and the original page's order is re-assigned soon. > But, it is better to correct code. > > Additionally, I change (set/clear)_page_guard_flag() to > (set/clear)_page_guard() and makes these functions do all works > needed for guard page. This may make code more understandable. > > One more thing, I did in this patch, is that fixing freepage accounting. > If we clear guard page and link it onto isolate buddy list, we should > not increase freepage count. OK, since this is under CONFIG_DEBUG_PAGEALLOC, and I don't see other solution in this case, I agree. > Signed-off-by: Joonsoo Kim Acked-by: Vlastimil Babka > --- > mm/page_alloc.c | 29 ++++++++++++++++------------- > 1 file changed, 16 insertions(+), 13 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0d4cf7a..aeb51d1 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -441,18 +441,28 @@ static int __init debug_guardpage_minorder_setup(char *buf) > } > __setup("debug_guardpage_minorder=", debug_guardpage_minorder_setup); > > -static inline void set_page_guard_flag(struct page *page) > +static inline void set_page_guard(struct zone *zone, struct page *page, > + unsigned int order, int migratetype) > { > __set_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags); > + set_page_private(page, order); > + /* Guard pages are not available for any usage */ > + __mod_zone_freepage_state(zone, -(1 << order), migratetype); > } > > -static inline void clear_page_guard_flag(struct page *page) > +static inline void clear_page_guard(struct zone *zone, struct page *page, > + unsigned int order, int migratetype) > { > __clear_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags); > + set_page_private(page, 0); > + if (!is_migrate_isolate(migratetype)) > + __mod_zone_freepage_state(zone, (1 << order), migratetype); > } > #else > -static inline void set_page_guard_flag(struct page *page) { } > -static inline void clear_page_guard_flag(struct page *page) { } > +static inline void set_page_guard(struct zone *zone, struct page *page, > + unsigned int order, int migratetype) {} > +static inline void clear_page_guard(struct zone *zone, struct page *page, > + unsigned int order, int migratetype) {} > #endif > > static inline void set_page_order(struct page *page, unsigned int order) > @@ -594,10 +604,7 @@ static inline void __free_one_page(struct page *page, > * merge with it and move up one order. > */ > if (page_is_guard(buddy)) { > - clear_page_guard_flag(buddy); > - set_page_private(page, 0); > - __mod_zone_freepage_state(zone, 1 << order, > - migratetype); > + clear_page_guard(zone, buddy, order, migratetype); > } else { > list_del(&buddy->lru); > zone->free_area[order].nr_free--; > @@ -919,11 +926,7 @@ static inline void expand(struct zone *zone, struct page *page, > * pages will stay not present in virtual address space > */ > INIT_LIST_HEAD(&page[size].lru); > - set_page_guard_flag(&page[size]); > - set_page_private(&page[size], high); > - /* Guard pages are not available for any usage */ > - __mod_zone_freepage_state(zone, -(1 << high), > - migratetype); > + set_page_guard(zone, &page[size], high, migratetype); > continue; > } > #endif > -- 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/