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Wed, 9 Sep 2020 08:26:06 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D15BC4C050; Wed, 9 Sep 2020 08:26:05 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 301504C04E; Wed, 9 Sep 2020 08:26:05 +0000 (GMT) Received: from pomme.local (unknown [9.145.19.60]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 9 Sep 2020 08:26:05 +0000 (GMT) Subject: Re: [PATCH] mm: don't rely on system state to detect hot-plug operations To: David Hildenbrand , Greg Kroah-Hartman Cc: akpm@linux-foundation.org, salvador@suse.de, rafael@kernel.org, nathanl@linux.ibm.com, mhocko@kernel.org, cheloha@linux.ibm.com, stable@vger.kernel.org, Linux-MM References: <5cbd92e1-c00a-4253-0119-c872bfa0f2bc@redhat.com> <20200908170835.85440-1-ldufour@linux.ibm.com> <20200908173113.GB218801@kroah.com> From: Laurent Dufour Message-ID: <7390116a-bfa9-9ad2-70fa-01be68035b7e@linux.ibm.com> Date: Wed, 9 Sep 2020 10:26:04 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-09-09_03:2020-09-08,2020-09-09 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 clxscore=1015 impostorscore=0 spamscore=0 suspectscore=0 malwarescore=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 mlxlogscore=999 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009090063 X-Rspamd-Queue-Id: 821EA180F8B80 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 Content-Transfer-Encoding: quoted-printable 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: Le 08/09/2020 =C3=A0 19:40, David Hildenbrand a =C3=A9crit=C2=A0: > On 08.09.20 19:31, Greg Kroah-Hartman wrote: >> On Tue, Sep 08, 2020 at 07:08:35PM +0200, Laurent Dufour wrote: >>> In register_mem_sect_under_node() the system_state=E2=80=99s value is= checked to >>> detect whether the operation the call is made during boot time or dur= ing an >>> hot-plug operation. Unfortunately, that check is wrong on some >>> architecture, and may lead to sections being registered under multipl= e >>> nodes if node's memory ranges are interleaved. >>> >>> This can be seen on PowerPC LPAR after multiple memory hot-plug and >>> hot-unplug operations are done. At the next reboot the node's memory = ranges >>> can be interleaved and since the call to link_mem_sections() is made = in >>> topology_init() while the system is in the SYSTEM_SCHEDULING state, t= he >>> node's id is not checked, and the sections registered multiple times.= In >>> that case, the system is able to boot but later hot-plug operation ma= y lead >>> to this panic because the node's links are correctly broken: >>> >>> ------------[ cut here ]------------ >>> kernel BUG at /Users/laurent/src/linux-ppc/mm/memory_hotplug.c:1084! >>> Oops: Exception in kernel mode, sig: 5 [#1] >>> LE PAGE_SIZE=3D64K MMU=3DHash SMP NR_CPUS=3D2048 NUMA pSeries >>> Modules linked in: rpadlpar_io rpaphp pseries_rng rng_core vmx_crypto= gf128mul binfmt_misc ip_tables x_tables xfs libcrc32c crc32c_vpmsum auto= fs4 >>> CPU: 8 PID: 10256 Comm: drmgr Not tainted 5.9.0-rc1+ #25 >>> NIP: c000000000403f34 LR: c000000000403f2c CTR: 0000000000000000 >>> REGS: c0000004876e3660 TRAP: 0700 Not tainted (5.9.0-rc1+) >>> MSR: 800000000282b033 CR: 2400044= 8 XER: 20040000 >>> CFAR: c000000000846d20 IRQMASK: 0 >>> GPR00: c000000000403f2c c0000004876e38f0 c0000000012f6f00 fffffffffff= fffef >>> GPR04: 0000000000000227 c0000004805ae680 0000000000000000 00000004886= f0000 >>> GPR08: 0000000000000226 0000000000000003 0000000000000002 fffffffffff= ffffd >>> GPR12: 0000000088000484 c00000001ec96280 0000000000000000 00000000000= 00000 >>> GPR16: 0000000000000000 0000000000000000 0000000000000004 00000000000= 00003 >>> GPR20: c00000047814ffe0 c0000007ffff7c08 0000000000000010 c0000000013= 332c8 >>> GPR24: 0000000000000000 c0000000011f6cc0 0000000000000000 00000000000= 00000 >>> GPR28: ffffffffffffffef 0000000000000001 0000000150000000 00000000100= 00000 >>> NIP [c000000000403f34] add_memory_resource+0x244/0x340 >>> LR [c000000000403f2c] add_memory_resource+0x23c/0x340 >>> Call Trace: >>> [c0000004876e38f0] [c000000000403f2c] add_memory_resource+0x23c/0x340= (unreliable) >>> [c0000004876e39c0] [c00000000040408c] __add_memory+0x5c/0xf0 >>> [c0000004876e39f0] [c0000000000e2b94] dlpar_add_lmb+0x1b4/0x500 >>> [c0000004876e3ad0] [c0000000000e3888] dlpar_memory+0x1f8/0xb80 >>> [c0000004876e3b60] [c0000000000dc0d0] handle_dlpar_errorlog+0xc0/0x19= 0 >>> [c0000004876e3bd0] [c0000000000dc398] dlpar_store+0x198/0x4a0 >>> [c0000004876e3c90] [c00000000072e630] kobj_attr_store+0x30/0x50 >>> [c0000004876e3cb0] [c00000000051f954] sysfs_kf_write+0x64/0x90 >>> [c0000004876e3cd0] [c00000000051ee40] kernfs_fop_write+0x1b0/0x290 >>> [c0000004876e3d20] [c000000000438dd8] vfs_write+0xe8/0x290 >>> [c0000004876e3d70] [c0000000004391ac] ksys_write+0xdc/0x130 >>> [c0000004876e3dc0] [c000000000034e40] system_call_exception+0x160/0x2= 70 >>> [c0000004876e3e20] [c00000000000d740] system_call_common+0xf0/0x27c >>> Instruction dump: >>> 48442e35 60000000 0b030000 3cbe0001 7fa3eb78 7bc48402 38a5fffe 7ca5fa= 14 >>> 78a58402 48442db1 60000000 7c7c1b78 <0b030000> 7f23cb78 4bda371d 6000= 0000 >>> ---[ end trace 562fd6c109cd0fb2 ]--- >>> >>> This patch addresses the root cause by not relying on the system_stat= e >>> value to detect whether the call is due to a hot-plug operation or no= t. An >>> additional parameter is added to link_mem_sections() to tell the cont= ext of >>> the call and this parameter is propagated to register_mem_sect_under_= node() >>> throuugh the walk_memory_blocks()'s call. >>> >>> Fixes: 4fbce633910e ("mm/memory_hotplug.c: make register_mem_sect_und= er_node() a callback of walk_memory_range()") >>> Signed-off-by: Laurent Dufour >>> Cc: stable@vger.kernel.org >>> Cc: Greg Kroah-Hartman >>> Cc: "Rafael J. Wysocki" >>> Cc: Andrew Morton >>> --- >>> drivers/base/node.c | 20 +++++++++++++++----- >>> include/linux/node.h | 6 +++--- >>> mm/memory_hotplug.c | 3 ++- >>> 3 files changed, 20 insertions(+), 9 deletions(-) >>> >>> diff --git a/drivers/base/node.c b/drivers/base/node.c >>> index 508b80f6329b..27f828eeb531 100644 >>> --- a/drivers/base/node.c >>> +++ b/drivers/base/node.c >>> @@ -762,14 +762,19 @@ static int __ref get_nid_for_pfn(unsigned long = pfn) >>> } >>> =20 >>> /* register memory section under specified node if it spans that no= de */ >>> +struct rmsun_args { >>> + int nid; >>> + bool hotadd; >>> +}; >>> static int register_mem_sect_under_node(struct memory_block *mem_bl= k, >>> - void *arg) >>> + void *args) >>> { >>> unsigned long memory_block_pfns =3D memory_block_size_bytes() / PA= GE_SIZE; >>> unsigned long start_pfn =3D section_nr_to_pfn(mem_blk->start_secti= on_nr); >>> unsigned long end_pfn =3D start_pfn + memory_block_pfns - 1; >>> - int ret, nid =3D *(int *)arg; >>> + int ret, nid =3D ((struct rmsun_args *)args)->nid; >>> unsigned long pfn; >>> + bool hotadd =3D ((struct rmsun_args *)args)->hotadd; >>> =20 >>> for (pfn =3D start_pfn; pfn <=3D end_pfn; pfn++) { >>> int page_nid; >>> @@ -789,7 +794,7 @@ static int register_mem_sect_under_node(struct me= mory_block *mem_blk, >>> * case, during hotplug we know that all pages in the memory >>> * block belong to the same node. >>> */ >>> - if (system_state =3D=3D SYSTEM_BOOTING) { >>> + if (!hotadd) { >>> page_nid =3D get_nid_for_pfn(pfn); >>> if (page_nid < 0) >>> continue; >>> @@ -832,10 +837,15 @@ void unregister_memory_block_under_nodes(struct= memory_block *mem_blk) >>> kobject_name(&node_devices[mem_blk->nid]->dev.kobj)); >>> } >>> =20 >>> -int link_mem_sections(int nid, unsigned long start_pfn, unsigned lon= g end_pfn) >>> +int link_mem_sections(int nid, unsigned long start_pfn, unsigned lon= g end_pfn, >>> + bool hotadd) >>> { >>> + struct rmsun_args args; >>> + >>> + args.nid =3D nid; >>> + args.hotadd =3D hotadd; >>> return walk_memory_blocks(PFN_PHYS(start_pfn), >>> - PFN_PHYS(end_pfn - start_pfn), (void *)&nid, >>> + PFN_PHYS(end_pfn - start_pfn), (void *)&args, >>> register_mem_sect_under_node); >>> } >>> =20 >>> diff --git a/include/linux/node.h b/include/linux/node.h >>> index 4866f32a02d8..6df9a4548650 100644 >>> --- a/include/linux/node.h >>> +++ b/include/linux/node.h >>> @@ -100,10 +100,10 @@ typedef void (*node_registration_func_t)(struc= t node *); >>> =20 >>> #if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_NUMA) >>> extern int link_mem_sections(int nid, unsigned long start_pfn, >>> - unsigned long end_pfn); >>> + unsigned long end_pfn, bool hotadd); >>> #else >>> static inline int link_mem_sections(int nid, unsigned long start_pf= n, >>> - unsigned long end_pfn) >>> + unsigned long end_pfn, bool hotadd) >> >> Adding a random boolean flag to a function is a horrible way to do >> anything. >> >> Now you need to look up what that flag means every time you run across= a >> caller, breaking your reading of what is happening. >> >> Make this two different functions please, that describe what they do, >> and have them call a common "helper function" that does the work with >> the flag if you really want to do this type of thing. >> >> link_mem_sections() and link_mem_sections_hotadd()? >> >> But not this way, please no. >=20 > For memmap_init_zone() we solved it via an enum with MEMMAP_HOTPLUG vs > MEMMAP_EARLY. Maybe we can generalize, because it tries to tackle > roughly the same thing. Thanks Dacid, I like this idea. However, I think I'll not reuse the memmap_context enum, but introduce a = new one=20 specific to the link operation, to be more explicit, something like: /* * When a hotplug operation is done, all pages in the memory block belon= g to the * same node, so there is no need to do such a check in that case. */ enum linkmem_context { LINKMEM_NO_CHECK_NODE_ID, LINKMEM_CHECK_NODE_ID, } I'm bad at naming so feel free to argue. Cheers, Laurent.