On 09.09.20 10:26, Laurent Dufour wrote:
> Le 08/09/2020 à 19:40, David Hildenbrand a écrit :
>> 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’s value is checked to
>>>> detect whether the operation the call is made during boot time or during an
>>>> hot-plug operation. Unfortunately, that check is wrong on some
>>>> architecture, and may lead to sections being registered under multiple
>>>> 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, the
>>>> 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 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=64K MMU=Hash SMP NR_CPUS=2048 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 autofs4
>>>> 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 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24000448 XER: 20040000
>>>> CFAR: c000000000846d20 IRQMASK: 0
>>>> GPR00: c000000000403f2c c0000004876e38f0 c0000000012f6f00 ffffffffffffffef
>>>> GPR04: 0000000000000227 c0000004805ae680 0000000000000000 00000004886f0000
>>>> GPR08: 0000000000000226 0000000000000003 0000000000000002 fffffffffffffffd
>>>> GPR12: 0000000088000484 c00000001ec96280 0000000000000000 0000000000000000
>>>> GPR16: 0000000000000000 0000000000000000 0000000000000004 0000000000000003
>>>> GPR20: c00000047814ffe0 c0000007ffff7c08 0000000000000010 c0000000013332c8
>>>> GPR24: 0000000000000000 c0000000011f6cc0 0000000000000000 0000000000000000
>>>> GPR28: ffffffffffffffef 0000000000000001 0000000150000000 0000000010000000
>>>> 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+0xc0/0x190
>>>> [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+0x160/0x270
>>>> [c0000004876e3e20] [c00000000000d740] system_call_common+0xf0/0x27c
>>>> Instruction dump:
>>>> 48442e35 60000000 0b030000 3cbe0001 7fa3eb78 7bc48402 38a5fffe 7ca5fa14
>>>> 78a58402 48442db1 60000000 7c7c1b78 <0b030000> 7f23cb78 4bda371d 60000000
>>>> ---[ end trace 562fd6c109cd0fb2 ]---
>>>>
>>>> This patch addresses the root cause by not relying on the system_state
>>>> 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 context 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_under_node() a callback of walk_memory_range()")
>>>> Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxx>
>>>> Cc: stable@xxxxxxxxxxxxxxx
>>>> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>>>> Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
>>>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>>>> ---
>>>> 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)
>>>> }
>>>>
>>>> /* 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 = memory_block_size_bytes() / PAGE_SIZE;
>>>> unsigned long start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
>>>> unsigned long end_pfn = start_pfn + memory_block_pfns - 1;
>>>> - int ret, nid = *(int *)arg;
>>>> + int ret, nid = ((struct rmsun_args *)args)->nid;
>>>> unsigned long pfn;
>>>> + bool hotadd = ((struct rmsun_args *)args)->hotadd;
>>>>
>>>> for (pfn = start_pfn; pfn <= 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 == SYSTEM_BOOTING) {
>>>> + if (!hotadd) {
>>>> page_nid = 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));
>>>> }
>>>>
>>>> -int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn)
>>>> +int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn,
>>>> + bool hotadd)
>>>> {
>>>> + struct rmsun_args args;
>>>> +
>>>> + args.nid = nid;
>>>> + args.hotadd = 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);
>>>> }
>>>>
>>>> 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)(struct node *);
>>>>
>>>> #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 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.
>>
>> 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
> specific to the link operation, to be more explicit, something like:
>
> /*
> * When a hotplug operation is done, all pages in the memory block belong 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.
>
"context" does not really fit the two cases that rather tell you what to
do (like a single flag).
I would have renamed "enum memmap_context" to something like "enum
mp_context" ("memory plug") and used
MP_CONTEXT_EARLY / MP_CONTEXT_HOTPLUG
Instead of using fairly specific "LINKMEM_*_CHECK_NODE_ID" ...
I am, also bad at naming, so ... :)
--
Thanks,
David / dhildenb
