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Wed, 9 Sep 2020 09:33:51 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 463684C04E; Wed, 9 Sep 2020 09:35:24 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A0D294C05C; Wed, 9 Sep 2020 09:35:23 +0000 (GMT) Received: from pomme.local (unknown [9.145.19.60]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 9 Sep 2020 09:35:23 +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> <7390116a-bfa9-9ad2-70fa-01be68035b7e@linux.ibm.com> From: Laurent Dufour Message-ID: <25f5e732-8086-6f96-7b64-688f7138b538@linux.ibm.com> Date: Wed, 9 Sep 2020 11:35:23 +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 lowpriorityscore=0 mlxscore=0 mlxlogscore=999 malwarescore=0 clxscore=1015 adultscore=0 priorityscore=1501 bulkscore=0 suspectscore=0 impostorscore=0 phishscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009090081 X-Rspamd-Queue-Id: 7C64C180BFBD8 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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 09/09/2020 =C3=A0 10:31, David Hildenbrand a =C3=A9crit=C2=A0: > On 09.09.20 10:26, Laurent Dufour wrote: >> 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 d= uring an >>>>> hot-plug operation. Unfortunately, that check is wrong on some >>>>> architecture, and may lead to sections being registered under multi= ple >>>>> 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 memor= y ranges >>>>> can be interleaved and since the call to link_mem_sections() is mad= e in >>>>> topology_init() while the system is in the SYSTEM_SCHEDULING state,= the >>>>> node's id is not checked, and the sections registered multiple time= s. In >>>>> that case, the system is able to boot but later hot-plug operation = may 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_cryp= to gf128mul binfmt_misc ip_tables x_tables xfs libcrc32c crc32c_vpmsum au= tofs4 >>>>> 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: 24000= 448 XER: 20040000 >>>>> CFAR: c000000000846d20 IRQMASK: 0 >>>>> GPR00: c000000000403f2c c0000004876e38f0 c0000000012f6f00 fffffffff= fffffef >>>>> GPR04: 0000000000000227 c0000004805ae680 0000000000000000 000000048= 86f0000 >>>>> GPR08: 0000000000000226 0000000000000003 0000000000000002 fffffffff= ffffffd >>>>> GPR12: 0000000088000484 c00000001ec96280 0000000000000000 000000000= 0000000 >>>>> GPR16: 0000000000000000 0000000000000000 0000000000000004 000000000= 0000003 >>>>> GPR20: c00000047814ffe0 c0000007ffff7c08 0000000000000010 c00000000= 13332c8 >>>>> GPR24: 0000000000000000 c0000000011f6cc0 0000000000000000 000000000= 0000000 >>>>> GPR28: ffffffffffffffef 0000000000000001 0000000150000000 000000001= 0000000 >>>>> NIP [c000000000403f34] add_memory_resource+0x244/0x340 >>>>> LR [c000000000403f2c] add_memory_resource+0x23c/0x340 >>>>> Call Trace: >>>>> [c0000004876e38f0] [c000000000403f2c] add_memory_resource+0x23c/0x3= 40 (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+0xc0/0x= 190 >>>>> [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+0x160/0= x270 >>>>> [c0000004876e3e20] [c00000000000d740] system_call_common+0xf0/0x27c >>>>> Instruction dump: >>>>> 48442e35 60000000 0b030000 3cbe0001 7fa3eb78 7bc48402 38a5fffe 7ca5= fa14 >>>>> 78a58402 48442db1 60000000 7c7c1b78 <0b030000> 7f23cb78 4bda371d 60= 000000 >>>>> ---[ end trace 562fd6c109cd0fb2 ]--- >>>>> >>>>> This patch addresses the root cause by not relying on the system_st= ate >>>>> value to detect whether the call is due to a hot-plug operation or = not. An >>>>> additional parameter is added to link_mem_sections() to tell the co= ntext of >>>>> the call and this parameter is propagated to register_mem_sect_unde= r_node() >>>>> throuugh the walk_memory_blocks()'s call. >>>>> >>>>> Fixes: 4fbce633910e ("mm/memory_hotplug.c: make register_mem_sect_u= nder_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 lon= g pfn) >>>>> } >>>>> =20 >>>>> /* register memory section under specified node if it spans that= node */ >>>>> +struct rmsun_args { >>>>> + int nid; >>>>> + bool hotadd; >>>>> +}; >>>>> static int register_mem_sect_under_node(struct memory_block *mem= _blk, >>>>> - void *arg) >>>>> + void *args) >>>>> { >>>>> unsigned long memory_block_pfns =3D memory_block_size_bytes() /= PAGE_SIZE; >>>>> unsigned long start_pfn =3D section_nr_to_pfn(mem_blk->start_se= ction_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 = memory_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(stru= ct 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 l= ong end_pfn) >>>>> +int link_mem_sections(int nid, unsigned long start_pfn, unsigned l= ong 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)(str= uct 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= _pfn, >>>>> - 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 acro= ss 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 wit= h >>>> 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. >>> >>> For memmap_init_zone() we solved it via an enum with MEMMAP_HOTPLUG v= s >>> 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 >> specific to the link operation, to be more explicit, something like: >> >> /* >> * When a hotplug operation is done, all pages in the memory block b= elong 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. >> >=20 > "context" does not really fit the two cases that rather tell you what t= o > do (like a single flag). I agree "linkmem_option" might be better, isn't it? > I would have renamed "enum memmap_context" to something like "enum > mp_context" ("memory plug") and used >=20 > MP_CONTEXT_EARLY / MP_CONTEXT_HOTPLUG >=20 > Instead of using fairly specific "LINKMEM_*_CHECK_NODE_ID" ... My point was to explicitly show by the enum name, why there is a differen= t=20 processing done. Showing that we are at boot or hot-plug time is not tell= ing the=20 caller that the node id check will be by-passed and that the assumption i= s made=20 that all pages belong to the same node. I think it may be good to be explicit about that. > I am, also bad at naming, so ... :) So I'm arguing, but ... ;)