From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754631AbbIINh3 (ORCPT ); Wed, 9 Sep 2015 09:37:29 -0400 Received: from m12-11.163.com ([220.181.12.11]:51480 "EHLO m12-11.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753338AbbIINhV (ORCPT ); Wed, 9 Sep 2015 09:37:21 -0400 Date: Wed, 9 Sep 2015 21:28:48 +0800 From: Yaowei Bai To: Vlastimil Babka Cc: akpm@linux-foundation.org, mgorman@suse.de, mhocko@kernel.org, js1304@gmail.com, hannes@cmpxchg.org, alexander.h.duyck@redhat.com, sasha.levin@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm/page_alloc: add a helper function to check page before alloc/free Message-ID: <20150909132848.GA3935@bbox> References: <1440679917-3507-1-git-send-email-bywxiaobai@163.com> <55EF34AB.5040003@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55EF34AB.5040003@suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) X-CM-TRANSID: C8CowEA5c04PNPBVXpfABg--.493S3 X-Coremail-Antispam: 1Uf129KBjvJXoWxAF4rWrW5Kr4fGryrAr4fZrb_yoWrtr13pa 1xAasrAa1rtasrKrs2qrnruF1rArn3tFW7Aa43K3W3ta42vr4SyryxJr1Ygr1fu3yxAr1I vF4Utr1fu3W5AFDanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jJuc_UUUUU= X-Originating-IP: [58.208.66.168] X-CM-SenderInfo: xe1z5x5dretxi6rwjhhfrp/1tbiUBVwT1WBP+393gAAsf Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 08, 2015 at 09:19:07PM +0200, Vlastimil Babka wrote: > On 08/27/2015 02:51 PM, Yaowei Bai wrote: > > The major portion of check_new_page() and free_pages_check() are same, > > introduce a helper function check_one_page() for simplification. > > > > Change in v3: > > - add the missed __PG_HWPOISON check per Michal Hocko > > Change in v2: > > - use bad_flags as parameter directly per Michal Hocko > > > > Signed-off-by: Yaowei Bai > > --- > > mm/page_alloc.c | 54 +++++++++++++++++++++++------------------------------- > > 1 file changed, 23 insertions(+), 31 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 5b5240b..0c9c82a 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -707,10 +707,9 @@ out: > > zone->free_area[order].nr_free++; > > } > > > > -static inline int free_pages_check(struct page *page) > > +static inline int check_one_page(struct page *page, unsigned long bad_flags) > > { > > const char *bad_reason = NULL; > > - unsigned long bad_flags = 0; > > > > if (unlikely(page_mapcount(page))) > > bad_reason = "nonzero mapcount"; > > @@ -718,9 +717,16 @@ static inline int free_pages_check(struct page *page) > > bad_reason = "non-NULL mapping"; > > if (unlikely(atomic_read(&page->_count) != 0)) > > bad_reason = "nonzero _count"; > > - if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_FREE)) { > > - bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set"; > > - bad_flags = PAGE_FLAGS_CHECK_AT_FREE; > > + if (bad_flags == PAGE_FLAGS_CHECK_AT_PREP) { > > + if (unlikely(page->flags & bad_flags)) > > + bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set"; > > + if (unlikely(page->flags & __PG_HWPOISON)) { > > + bad_reason = "HWPoisoned (hardware-corrupted)"; > > + bad_flags = __PG_HWPOISON; > > + } > > Before, HWPOISON was checked first, which means that it had lower priority than > PAGE_FLAGS_CHECK_AT_PREP (counter-intuitively). I can see why you switched that > though. You could fix that by changing the second nested "if" to "else if", but > I guess it doesn't matter. The "priorities" don't seem to be carefuly sorted anyway. OK, so let's leave as it is and see other guys' ideas. If there is any objection i will resend with fixing the priority. > > bloat-o-meter looks favorably with my gcc, although there shouldn't be a real > reason for it, as the inlining didn't change: > > add/remove: 1/1 grow/shrink: 1/1 up/down: 285/-336 (-51) > function old new delta > bad_page - 276 +276 > get_page_from_freelist 2521 2530 +9 > free_pages_prepare 745 667 -78 > bad_page.part 258 - -258 > > With that, > > Acked-by: Vlastimil Babka Thanks. > > > + } else if (bad_flags == PAGE_FLAGS_CHECK_AT_FREE) { > > + if (unlikely(page->flags & bad_flags)) > > + bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag set"; > > } > > #ifdef CONFIG_MEMCG > > if (unlikely(page->mem_cgroup)) > > @@ -730,6 +736,17 @@ static inline int free_pages_check(struct page *page) > > bad_page(page, bad_reason, bad_flags); > > return 1; > > } > > + return 0; > > +} > > + > > +static inline int free_pages_check(struct page *page) > > +{ > > + int ret = 0; > > + > > + ret = check_one_page(page, PAGE_FLAGS_CHECK_AT_FREE); > > + if (ret) > > + return ret; > > + > > page_cpupid_reset_last(page); > > if (page->flags & PAGE_FLAGS_CHECK_AT_PREP) > > page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > > @@ -1287,32 +1304,7 @@ static inline void expand(struct zone *zone, struct page *page, > > */ > > static inline int check_new_page(struct page *page) > > { > > - const char *bad_reason = NULL; > > - unsigned long bad_flags = 0; > > - > > - if (unlikely(page_mapcount(page))) > > - bad_reason = "nonzero mapcount"; > > - if (unlikely(page->mapping != NULL)) > > - bad_reason = "non-NULL mapping"; > > - if (unlikely(atomic_read(&page->_count) != 0)) > > - bad_reason = "nonzero _count"; > > - if (unlikely(page->flags & __PG_HWPOISON)) { > > - bad_reason = "HWPoisoned (hardware-corrupted)"; > > - bad_flags = __PG_HWPOISON; > > - } > > - if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) { > > - bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set"; > > - bad_flags = PAGE_FLAGS_CHECK_AT_PREP; > > - } > > -#ifdef CONFIG_MEMCG > > - if (unlikely(page->mem_cgroup)) > > - bad_reason = "page still charged to cgroup"; > > -#endif > > - if (unlikely(bad_reason)) { > > - bad_page(page, bad_reason, bad_flags); > > - return 1; > > - } > > - return 0; > > + return check_one_page(page, PAGE_FLAGS_CHECK_AT_PREP); > > } > > > > static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, > >