From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f179.google.com (mail-wi0-f179.google.com [209.85.212.179]) by kanga.kvack.org (Postfix) with ESMTP id F3AC26B0038 for ; Tue, 8 Sep 2015 15:19:12 -0400 (EDT) Received: by wiclk2 with SMTP id lk2so126829872wic.1 for ; Tue, 08 Sep 2015 12:19:12 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id t16si7747029wjr.209.2015.09.08.12.19.10 for (version=TLS1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 08 Sep 2015 12:19:11 -0700 (PDT) Subject: Re: [PATCH v3] mm/page_alloc: add a helper function to check page before alloc/free References: <1440679917-3507-1-git-send-email-bywxiaobai@163.com> From: Vlastimil Babka Message-ID: <55EF34AB.5040003@suse.cz> Date: Tue, 8 Sep 2015 21:19:07 +0200 MIME-Version: 1.0 In-Reply-To: <1440679917-3507-1-git-send-email-bywxiaobai@163.com> Content-Type: text/plain; charset=iso-8859-2 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Yaowei Bai , 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 Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org 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. 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 > + } 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, > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org