From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 442656B007E for ; Fri, 27 May 2016 16:17:23 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id g64so149871295pfb.2 for ; Fri, 27 May 2016 13:17:23 -0700 (PDT) Received: from mail-pa0-x235.google.com (mail-pa0-x235.google.com. [2607:f8b0:400e:c03::235]) by mx.google.com with ESMTPS id c1si30480884pas.37.2016.05.27.13.17.21 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 27 May 2016 13:17:21 -0700 (PDT) Received: by mail-pa0-x235.google.com with SMTP id bz2so13336644pad.1 for ; Fri, 27 May 2016 13:17:21 -0700 (PDT) Subject: Re: [PATCH] mm: check the return value of lookup_page_ext for all call sites References: <1464023768-31025-1-git-send-email-yang.shi@linaro.org> <20160524025811.GA29094@bbox> <20160526003719.GB9661@bbox> <8ae0197c-47b7-e5d2-20c3-eb9d01e6b65c@linaro.org> <20160527130246.4adb78f29e15d19fae80419a@linux-foundation.org> From: "Shi, Yang" Message-ID: Date: Fri, 27 May 2016 13:17:19 -0700 MIME-Version: 1.0 In-Reply-To: <20160527130246.4adb78f29e15d19fae80419a@linux-foundation.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Minchan Kim , iamjoonsoo.kim@lge.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linaro-kernel@lists.linaro.org On 5/27/2016 1:02 PM, Andrew Morton wrote: > On Thu, 26 May 2016 16:15:28 -0700 "Shi, Yang" wrote: > >>>> >>>> I hope we consider this direction, too. >>> >>> Yang, Could you think about this? >> >> Thanks a lot for the suggestion. Sorry for the late reply, I was busy on >> preparing patches. I do agree this is a direction we should look into, >> but I haven't got time to think about it deeper. I hope Joonsoo could >> chime in too since he is the original author for page extension. >> >>> >>> Even, your patch was broken, I think. >>> It doesn't work with !CONFIG_DEBUG_VM && !CONFIG_PAGE_POISONING because >>> lookup_page_ext doesn't return NULL in that case. >> >> Actually, I think the #ifdef should be removed if lookup_page_ext() is >> possible to return NULL. It sounds not make sense returning NULL only >> when DEBUG_VM is enabled. It should return NULL no matter what debug >> config is selected. If Joonsoo agrees with me I'm going to come up with >> a patch to fix it. >> > > I've lost the plot here. What is the status of this patch? > > Latest version: Yes, this is the latest version. We are discussing about some future optimization. And, Minchan Kim pointed out a possible race condition which exists even before this patch. I proposed a quick fix, as long as they are happy to the fix, I will post it to the mailing list. Thanks, Yang > > From: Yang Shi > Subject: mm: check the return value of lookup_page_ext for all call sites > > Per the discussion with Joonsoo Kim [1], we need check the return value of > lookup_page_ext() for all call sites since it might return NULL in some > cases, although it is unlikely, i.e. memory hotplug. > > Tested with ltp with "page_owner=0". > > [1] http://lkml.kernel.org/r/20160519002809.GA10245@js1304-P5Q-DELUXE > > [akpm@linux-foundation.org: fix build-breaking typos] > [arnd@arndb.de: fix build problems from lookup_page_ext] > Link: http://lkml.kernel.org/r/6285269.2CksypHdYp@wuerfel > [akpm@linux-foundation.org: coding-style fixes] > Link: http://lkml.kernel.org/r/1464023768-31025-1-git-send-email-yang.shi@linaro.org > Signed-off-by: Yang Shi > Signed-off-by: Arnd Bergmann > Cc: Joonsoo Kim > Signed-off-by: Andrew Morton > --- > > include/linux/page_idle.h | 43 ++++++++++++++++++++++++++++++------ > mm/page_alloc.c | 6 +++++ > mm/page_owner.c | 26 +++++++++++++++++++++ > mm/page_poison.c | 8 +++++- > mm/vmstat.c | 2 + > 5 files changed, 77 insertions(+), 8 deletions(-) > > diff -puN include/linux/page_idle.h~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites include/linux/page_idle.h > --- a/include/linux/page_idle.h~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites > +++ a/include/linux/page_idle.h > @@ -46,33 +46,62 @@ extern struct page_ext_operations page_i > > static inline bool page_is_young(struct page *page) > { > - return test_bit(PAGE_EXT_YOUNG, &lookup_page_ext(page)->flags); > + struct page_ext *page_ext = lookup_page_ext(page); > + > + if (unlikely(!page_ext)) > + return false; > + > + return test_bit(PAGE_EXT_YOUNG, &page_ext->flags); > } > > static inline void set_page_young(struct page *page) > { > - set_bit(PAGE_EXT_YOUNG, &lookup_page_ext(page)->flags); > + struct page_ext *page_ext = lookup_page_ext(page); > + > + if (unlikely(!page_ext)) > + return; > + > + set_bit(PAGE_EXT_YOUNG, &page_ext->flags); > } > > static inline bool test_and_clear_page_young(struct page *page) > { > - return test_and_clear_bit(PAGE_EXT_YOUNG, > - &lookup_page_ext(page)->flags); > + struct page_ext *page_ext = lookup_page_ext(page); > + > + if (unlikely(!page_ext)) > + return false; > + > + return test_and_clear_bit(PAGE_EXT_YOUNG, &page_ext->flags); > } > > static inline bool page_is_idle(struct page *page) > { > - return test_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags); > + struct page_ext *page_ext = lookup_page_ext(page); > + > + if (unlikely(!page_ext)) > + return false; > + > + return test_bit(PAGE_EXT_IDLE, &page_ext->flags); > } > > static inline void set_page_idle(struct page *page) > { > - set_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags); > + struct page_ext *page_ext = lookup_page_ext(page); > + > + if (unlikely(!page_ext)) > + return; > + > + set_bit(PAGE_EXT_IDLE, &page_ext->flags); > } > > static inline void clear_page_idle(struct page *page) > { > - clear_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags); > + struct page_ext *page_ext = lookup_page_ext(page); > + > + if (unlikely(!page_ext)) > + return; > + > + clear_bit(PAGE_EXT_IDLE, &page_ext->flags); > } > #endif /* CONFIG_64BIT */ > > diff -puN mm/page_alloc.c~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites mm/page_alloc.c > --- a/mm/page_alloc.c~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites > +++ a/mm/page_alloc.c > @@ -656,6 +656,9 @@ static inline void set_page_guard(struct > return; > > page_ext = lookup_page_ext(page); > + if (unlikely(!page_ext)) > + return; > + > __set_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags); > > INIT_LIST_HEAD(&page->lru); > @@ -673,6 +676,9 @@ static inline void clear_page_guard(stru > return; > > page_ext = lookup_page_ext(page); > + if (unlikely(!page_ext)) > + return; > + > __clear_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags); > > set_page_private(page, 0); > diff -puN mm/page_owner.c~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites mm/page_owner.c > --- a/mm/page_owner.c~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites > +++ a/mm/page_owner.c > @@ -55,6 +55,8 @@ void __reset_page_owner(struct page *pag > > for (i = 0; i < (1 << order); i++) { > page_ext = lookup_page_ext(page + i); > + if (unlikely(!page_ext)) > + continue; > __clear_bit(PAGE_EXT_OWNER, &page_ext->flags); > } > } > @@ -62,6 +64,7 @@ void __reset_page_owner(struct page *pag > void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask) > { > struct page_ext *page_ext = lookup_page_ext(page); > + > struct stack_trace trace = { > .nr_entries = 0, > .max_entries = ARRAY_SIZE(page_ext->trace_entries), > @@ -69,6 +72,9 @@ void __set_page_owner(struct page *page, > .skip = 3, > }; > > + if (unlikely(!page_ext)) > + return; > + > save_stack_trace(&trace); > > page_ext->order = order; > @@ -82,6 +88,8 @@ void __set_page_owner(struct page *page, > void __set_page_owner_migrate_reason(struct page *page, int reason) > { > struct page_ext *page_ext = lookup_page_ext(page); > + if (unlikely(!page_ext)) > + return; > > page_ext->last_migrate_reason = reason; > } > @@ -89,6 +97,12 @@ void __set_page_owner_migrate_reason(str > gfp_t __get_page_owner_gfp(struct page *page) > { > struct page_ext *page_ext = lookup_page_ext(page); > + if (unlikely(!page_ext)) > + /* > + * The caller just returns 0 if no valid gfp > + * So return 0 here too. > + */ > + return 0; > > return page_ext->gfp_mask; > } > @@ -99,6 +113,9 @@ void __copy_page_owner(struct page *oldp > struct page_ext *new_ext = lookup_page_ext(newpage); > int i; > > + if (unlikely(!old_ext || !new_ext)) > + return; > + > new_ext->order = old_ext->order; > new_ext->gfp_mask = old_ext->gfp_mask; > new_ext->nr_entries = old_ext->nr_entries; > @@ -193,6 +210,11 @@ void __dump_page_owner(struct page *page > gfp_t gfp_mask = page_ext->gfp_mask; > int mt = gfpflags_to_migratetype(gfp_mask); > > + if (unlikely(!page_ext)) { > + pr_alert("There is not page extension available.\n"); > + return; > + } > + > if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) { > pr_alert("page_owner info is not active (free page?)\n"); > return; > @@ -251,6 +273,8 @@ read_page_owner(struct file *file, char > } > > page_ext = lookup_page_ext(page); > + if (unlikely(!page_ext)) > + continue; > > /* > * Some pages could be missed by concurrent allocation or free, > @@ -317,6 +341,8 @@ static void init_pages_in_zone(pg_data_t > continue; > > page_ext = lookup_page_ext(page); > + if (unlikely(!page_ext)) > + continue; > > /* Maybe overraping zone */ > if (test_bit(PAGE_EXT_OWNER, &page_ext->flags)) > diff -puN mm/page_poison.c~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites mm/page_poison.c > --- a/mm/page_poison.c~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites > +++ a/mm/page_poison.c > @@ -54,6 +54,9 @@ static inline void set_page_poison(struc > struct page_ext *page_ext; > > page_ext = lookup_page_ext(page); > + if (unlikely(!page_ext)) > + return; > + > __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); > } > > @@ -62,6 +65,9 @@ static inline void clear_page_poison(str > struct page_ext *page_ext; > > page_ext = lookup_page_ext(page); > + if (unlikely(!page_ext)) > + return; > + > __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); > } > > @@ -70,7 +76,7 @@ bool page_is_poisoned(struct page *page) > struct page_ext *page_ext; > > page_ext = lookup_page_ext(page); > - if (!page_ext) > + if (unlikely(!page_ext)) > return false; > > return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); > diff -puN mm/vmstat.c~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites mm/vmstat.c > --- a/mm/vmstat.c~mm-check-the-return-value-of-lookup_page_ext-for-all-call-sites > +++ a/mm/vmstat.c > @@ -1061,6 +1061,8 @@ static void pagetypeinfo_showmixedcount_ > continue; > > page_ext = lookup_page_ext(page); > + if (unlikely(!page_ext)) > + continue; > > if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) > continue; 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