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Wed, 7 Sep 2022 17:33:00 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id RcMNH8zVGGMDCwAAMHmgww (envelope-from ); Wed, 07 Sep 2022 17:33:00 +0000 Date: Wed, 7 Sep 2022 19:32:59 +0200 From: Michal Hocko To: Naoya Horiguchi Cc: David Hildenbrand , linux-mm@kvack.org, Andrew Morton , Muchun Song , Miaohe Lin , Matthew Wilcox , Yang Shi , Naoya Horiguchi Subject: Re: [PATCH] mm/huge_memory: use pfn_to_online_page() in split_huge_pages_all() Message-ID: References: <20220907100855.GA2894785@ik1-406-35019.vs.sakura.ne.jp> <1481ce19-0a64-d1dc-4d89-4db71d6f7eb3@redhat.com> <20220907121157.GA2954283@ik1-406-35019.vs.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220907121157.GA2954283@ik1-406-35019.vs.sakura.ne.jp> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662571982; a=rsa-sha256; cv=none; b=mCld8DG0giDYA3/g24Ry/HJvYI0okzLfL8dVKUreo5/MPuwZyK7xGTpIyTEjdlA4xzSM3n CuYIyseKJnXDlSg+ke0FFdvYVyFCY+d9zvOGkGd/7q9H5cfCLSCBEEAHrmVx9UDf7CSGxw FIBVsXjcVERbq5X86vqysBVUt0CivyM= ARC-Authentication-Results: i=1; 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dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf21.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=mhocko@suse.com X-Stat-Signature: 4ph43y85otk41b6u4pby41eehoxt3fp5 X-Rspam-User: X-HE-Tag: 1662571981-851486 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 Wed 07-09-22 21:11:57, Naoya Horiguchi wrote: [...] > >From 8a5c284df732943065d23838090d15c94cd10395 Mon Sep 17 00:00:00 2001 > From: Naoya Horiguchi > Date: Wed, 7 Sep 2022 20:58:44 +0900 > Subject: [PATCH] mm/huge_memory: use pfn_to_online_page() in > split_huge_pages_all() > > NULL pointer dereference is triggered when calling thp split via debugfs > on the system with offlined memory blocks. With debug option enabled, > the following kernel messages are printed out: > > page:00000000467f4890 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x121c000 > flags: 0x17fffc00000000(node=0|zone=2|lastcpupid=0x1ffff) > raw: 0017fffc00000000 0000000000000000 dead000000000122 0000000000000000 > raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000 > page dumped because: unmovable page > page:000000007d7ab72e is uninitialized and poisoned > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > ------------[ cut here ]------------ > kernel BUG at include/linux/mm.h:1248! > invalid opcode: 0000 [#1] PREEMPT SMP PTI > CPU: 16 PID: 20964 Comm: bash Tainted: G I 6.0.0-rc3-foll-numa+ #41 > ... > RIP: 0010:split_huge_pages_write+0xcf4/0xe30 > > This shows that page_to_nid() in page_zone() is unexpectedly called for an > offlined memmap. > > Use pfn_to_online_page() to get struct page in PFN walker. > > Fixes: 49071d436b51 ("thp: add debugfs handle to split all huge pages") > Suggested-by: David Hildenbrand > Signed-off-by: Naoya Horiguchi > Cc: With changes proposed by David Acked-by: Michal Hocko Thanks! > --- > mm/huge_memory.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 5fa2ba86dae4..03149a8f46f9 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2894,11 +2894,8 @@ static void split_huge_pages_all(void) > max_zone_pfn = zone_end_pfn(zone); > for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { > int nr_pages; > - if (!pfn_valid(pfn)) > - continue; > - > - page = pfn_to_page(pfn); > - if (!get_page_unless_zero(page)) > + page = pfn_to_online_page(pfn); > + if (!page || !get_page_unless_zero(page)) > continue; > > if (zone != page_zone(page)) > -- > 2.26.1.8815.g6a475b71f8 > -- Michal Hocko SUSE Labs