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[209.132.183.28]) by mx.google.com with ESMTPS id 31si6775818qvt.57.2019.06.17.00.26.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 17 Jun 2019 00:26:30 -0700 (PDT) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B45FA30872F1; Mon, 17 Jun 2019 07:26:17 +0000 (UTC) Received: from [10.36.116.141] (ovpn-116-141.ams2.redhat.com [10.36.116.141]) by smtp.corp.redhat.com (Postfix) with ESMTP id E866468405; Mon, 17 Jun 2019 07:26:07 +0000 (UTC) Subject: Re: [PATCH 2/5] mm: don't hide potentially null memmap pointer in sparse_remove_one_section To: Alastair D'Silva , alastair@d-silva.org Cc: Andrew Morton , Oscar Salvador , Michal Hocko , Pavel Tatashin , Wei Yang , Juergen Gross , Qian Cai , Thomas Gleixner , Ingo Molnar , Josh Poimboeuf , Konrad Rzeszutek Wilk , Jiri Kosina , Peter Zijlstra , Mukesh Ojha , Arun KS , Mike Rapoport , Baoquan He , Logan Gunthorpe , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190617043635.13201-1-alastair@au1.ibm.com> <20190617043635.13201-3-alastair@au1.ibm.com> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190617043635.13201-3-alastair@au1.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Mon, 17 Jun 2019 07:26:24 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 17.06.19 06:36, Alastair D'Silva wrote: > From: Alastair D'Silva > > By adding offset to memmap before passing it in to clear_hwpoisoned_pages, > is hides a potentially null memmap from the null check inside > clear_hwpoisoned_pages. > > This patch passes the offset to clear_hwpoisoned_pages instead, allowing > memmap to successfully peform it's null check. > > Signed-off-by: Alastair D'Silva > --- > mm/sparse.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 104a79fedd00..66a99da9b11b 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -746,12 +746,14 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn, > kfree(usemap); > __kfree_section_memmap(memmap, altmap); > } > + > return ret; > } > > #ifdef CONFIG_MEMORY_HOTREMOVE > #ifdef CONFIG_MEMORY_FAILURE > -static void clear_hwpoisoned_pages(struct page *memmap, int nr_pages) > +static void clear_hwpoisoned_pages(struct page *memmap, > + unsigned long map_offset, int nr_pages) > { > int i; > > @@ -767,7 +769,7 @@ static void clear_hwpoisoned_pages(struct page *memmap, int nr_pages) > if (atomic_long_read(&num_poisoned_pages) == 0) > return; > > - for (i = 0; i < nr_pages; i++) { > + for (i = map_offset; i < nr_pages; i++) { > if (PageHWPoison(&memmap[i])) { > atomic_long_sub(1, &num_poisoned_pages); > ClearPageHWPoison(&memmap[i]); > @@ -775,7 +777,8 @@ static void clear_hwpoisoned_pages(struct page *memmap, int nr_pages) > } > } > #else > -static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages) > +static inline void clear_hwpoisoned_pages(struct page *memmap, > + unsigned long map_offset, int nr_pages) I somewhat dislike that map_offset modifies nr_pages internally. I would prefer decoupling both and passing the actual number of pages to clear instead: clear_hwpoisoned_pages(memmap, map_offset, PAGES_PER_SECTION - map_offset); > { > } > #endif > @@ -822,8 +825,7 @@ void sparse_remove_one_section(struct zone *zone, struct mem_section *ms, > ms->pageblock_flags = NULL; > } > > - clear_hwpoisoned_pages(memmap + map_offset, > - PAGES_PER_SECTION - map_offset); > + clear_hwpoisoned_pages(memmap, map_offset, PAGES_PER_SECTION); > free_section_usemap(memmap, usemap, altmap); > } > #endif /* CONFIG_MEMORY_HOTREMOVE */ > -- Thanks, David / dhildenb