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[37.188.135.150]) by smtp.gmail.com with ESMTPSA id g14sm7306767wme.32.2020.03.27.00.47.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Mar 2020 00:47:20 -0700 (PDT) Date: Fri, 27 Mar 2020 08:47:18 +0100 From: Michal Hocko To: Dan Williams Cc: David Hildenbrand , Linux Kernel Mailing List , Linux MM , Greg Kroah-Hartman , "Rafael J. Wysocki" , Andrew Morton , powerpc-utils-devel@googlegroups.com, util-linux@vger.kernel.org, Badari Pulavarty , Nathan Fontenot , Robert Jennings , Heiko Carstens , Karel Zak , "Scargall, Steve" Subject: Re: [PATCH v1] drivers/base/memory.c: indicate all memory blocks as removable Message-ID: <20200327074718.GT27965@dhcp22.suse.cz> References: <20200128093542.6908-1-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Thu 26-03-20 23:24:08, Dan Williams wrote: [...] > David, Andrew, > > I'd like to recommend this patch for -stable as it likely (test > underway) solves this crash report from Steve: > > [ 148.796036] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > [ 148.796074] ------------[ cut here ]------------ > [ 148.796098] kernel BUG at include/linux/mm.h:1087! > [ 148.796126] invalid opcode: 0000 [#1] SMP NOPTI > [ 148.796146] CPU: 63 PID: 5471 Comm: lsmem Not tainted 5.5.10-200.fc31.x8= > 6_64+debug #1 > [ 148.796173] Hardware name: Intel Corporation S2600WFD/S2600WFD, BIOS SE5= > C620.86B.02.01.0010.010620200716 01/06/2020 > [ 148.796212] RIP: 0010:is_mem_section_removable+0x1a4/0x1b0 > [ 148.796561] Call Trace: > [ 148.796591] removable_show+0x6e/0xa0 > [ 148.796608] dev_attr_show+0x19/0x40 > [ 148.796625] sysfs_kf_seq_show+0xa9/0x100 > [ 148.796640] seq_read+0xd5/0x450 > [ 148.796657] vfs_read+0xc5/0x180 > [ 148.796672] ksys_read+0x68/0xe0 > [ 148.796688] do_syscall_64+0x5c/0xa0 > [ 148.796704] entry_SYSCALL_64_after_hwframe+0x49/0xbe > [ 148.796721] RIP: 0033:0x7f3ab1646412 > > ...on a non-debug kernel it just crashes. > > In this case lsmem is failing when reading memory96: > > openat(3, "memory96/removable", O_RDONLY|O_CLOEXEC) = 4 > fcntl(4, F_GETFL) = 0x8000 (flags O_RDONLY|O_LARGEFILE) > fstat(4, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0 > read(4, ) = ? > +++ killed by SIGSEGV +++ > Segmentation fault (core dumped) > > ...which is phys_index 0x60 => memory address 0x3000000000 > > On this platform that lands us here: > > 100000000-303fffffff : System RAM > 291f000000-291fe00f70 : Kernel code > 2920000000-292051efff : Kernel rodata > 2920600000-292093b0bf : Kernel data > 29214f3000-2922dfffff : Kernel bss > 3040000000-305fffffff : Reserved > 3060000000-1aa5fffffff : Persistent Memory OK, 2GB memblocks and that would mean [0x3000000000, 0x3080000000] > ...where the last memory block of System RAM is shared with persistent > memory. I.e. the block is only partially online which means that > page_to_nid() in is_mem_section_removable() will assert or crash for > some of the offline pages in that block. Yes, this patch is a simple workaround. Normal memory hotplug will not blow up because it should be able to find out that test_pages_in_a_zone is false. Who knows how other potential pfn walkers handle that. Risking to sound like a broken record I will remind that I have been pushing for having _all_ existing struct pages initialized and we wouldn't have problems like this popping out here and there. That being said, I do not have any objections to backporting to stable trees. -- Michal Hocko SUSE Labs