Backport version to the 5.4-stable tree of: [ Upstream commit f85086f95fa36194eb0db5cd5c12e56801b98523 ]

In register_mem_sect_under_node() the system_state's value is checked to detect whether the call is made during boot time or during an hot-plug operation. Unfortunately, that check against SYSTEM_BOOTING is wrong because regular memory is registered at SYSTEM_SCHEDULING state. In addition, memory hot-plug operation can be triggered at this system state by the ACPI [1]. So checking against the system state is not enough.

The consequence is that on system with interleaved node's ranges like this:

Early memory node ranges node 1: [mem 0x0000000000000000-0x000000011fffffff] node 2: [mem 0x0000000120000000-0x000000014fffffff] node 1: [mem 0x0000000150000000-0x00000001ffffffff] node 0: [mem 0x0000000200000000-0x000000048fffffff] node 2: [mem 0x0000000490000000-0x00000007ffffffff]

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 to multiple nodes:

$ ls -l /sys/devices/system/memory/memory21/node* total 0 lrwxrwxrwx 1 root root 0 Aug 24 05:27 node1 -> ../../node/node1 lrwxrwxrwx 1 root root 0 Aug 24 05:27 node2 -> ../../node/node2

In that case, the system is able to boot but if later one of theses memory blocks is hot-unplugged and then hot-plugged, the sysfs inconsistency is detected and this is triggering a BUG_ON():

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 Call Trace: add_memory_resource+0x23c/0x340 (unreliable) __add_memory+0x5c/0xf0 dlpar_add_lmb+0x1b4/0x500 dlpar_memory+0x1f8/0xb80 handle_dlpar_errorlog+0xc0/0x190 dlpar_store+0x198/0x4a0 kobj_attr_store+0x30/0x50 sysfs_kf_write+0x64/0x90 kernfs_fop_write+0x1b0/0x290 vfs_write+0xe8/0x290 ksys_write+0xdc/0x130 system_call_exception+0x160/0x270 system_call_common+0xf0/0x27c

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. An extra parameter is added to link_mem_sections() detailing whether the operation is due to a hot-plug operation.

[1] According to Oscar Salvador, using this qemu command line, ACPI memory hotplug operations are raised at SYSTEM_SCHEDULING state:

$QEMU -enable-kvm -machine pc -smp 4,sockets=4,cores=1,threads=1 -cpu host -monitor pty \ -m size=$MEM,slots=255,maxmem=4294967296k \ -numa node,nodeid=0,cpus=0-3,mem=512 -numa node,nodeid=1,mem=512 \ -object memory-backend-ram,id=memdimm0,size=134217728 -device pc-dimm,node=0,memdev=memdimm0,id=dimm0,slot=0 \ -object memory-backend-ram,id=memdimm1,size=134217728 -device pc-dimm,node=0,memdev=memdimm1,id=dimm1,slot=1 \ -object memory-backend-ram,id=memdimm2,size=134217728 -device pc-dimm,node=0,memdev=memdimm2,id=dimm2,slot=2 \ -object memory-backend-ram,id=memdimm3,size=134217728 -device pc-dimm,node=0,memdev=memdimm3,id=dimm3,slot=3 \ -object memory-backend-ram,id=memdimm4,size=134217728 -device pc-dimm,node=1,memdev=memdimm4,id=dimm4,slot=4 \ -object memory-backend-ram,id=memdimm5,size=134217728 -device pc-dimm,node=1,memdev=memdimm5,id=dimm5,slot=5 \ -object memory-backend-ram,id=memdimm6,size=134217728 -device pc-dimm,node=1,memdev=memdimm6,id=dimm6,slot=6 \

Fixes: 4fbce633910e ("mm/memory_hotplug.c: make register_mem_sect_under_node() a callback of walk_memory_range()") Signed-off-by: Laurent Dufour ldufour@linux.ibm.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Reviewed-by: David Hildenbrand david@redhat.com Reviewed-by: Oscar Salvador osalvador@suse.de Acked-by: Michal Hocko mhocko@suse.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: "Rafael J. Wysocki" rafael@kernel.org Cc: Fenghua Yu fenghua.yu@intel.com Cc: Nathan Lynch nathanl@linux.ibm.com Cc: Scott Cheloha cheloha@linux.ibm.com Cc: Tony Luck tony.luck@intel.com Cc: stable@vger.kernel.org # 5.4.y Link: https://lkml.kernel.org/r/20200915094143.79181-3-ldufour@linux.ibm.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org --- drivers/base/node.c | 85 ++++++++++++++++++++++++++++---------------- include/linux/node.h | 11 +++--- mm/memory_hotplug.c | 3 +- 3 files changed, 64 insertions(+), 35 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c index 296546ffed6c..9c6e6a7b9354 100644 --- a/drivers/base/node.c +++ b/drivers/base/node.c @@ -758,14 +758,36 @@ static int __ref get_nid_for_pfn(unsigned long pfn) return pfn_to_nid(pfn); }

+static int do_register_memory_block_under_node(int nid, + struct memory_block *mem_blk) +{ + int ret; + + /* + * If this memory block spans multiple nodes, we only indicate + * the last processed node. + */ + mem_blk->nid = nid; + + ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj, + &mem_blk->dev.kobj, + kobject_name(&mem_blk->dev.kobj)); + if (ret) + return ret; + + return sysfs_create_link_nowarn(&mem_blk->dev.kobj, + &node_devices[nid]->dev.kobj, + kobject_name(&node_devices[nid]->dev.kobj)); +} + /* register memory section under specified node if it spans that node */ -static int register_mem_sect_under_node(struct memory_block *mem_blk, - void *arg) +static int register_mem_block_under_node_early(struct memory_block *mem_blk, + void *arg) { 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 nid = *(int *)arg; unsigned long pfn;

for (pfn = start_pfn; pfn <= end_pfn; pfn++) { @@ -782,38 +804,33 @@ static int register_mem_sect_under_node(struct memory_block *mem_blk, }

/* - * We need to check if page belongs to nid only for the boot - * case, during hotplug we know that all pages in the memory - * block belong to the same node. - */ - if (system_state == SYSTEM_BOOTING) { - page_nid = get_nid_for_pfn(pfn); - if (page_nid < 0) - continue; - if (page_nid != nid) - continue; - } - - /* - * If this memory block spans multiple nodes, we only indicate - * the last processed node. + * We need to check if page belongs to nid only at the boot + * case because node's ranges can be interleaved. */ - mem_blk->nid = nid; - - ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj, - &mem_blk->dev.kobj, - kobject_name(&mem_blk->dev.kobj)); - if (ret) - return ret; + page_nid = get_nid_for_pfn(pfn); + if (page_nid < 0) + continue; + if (page_nid != nid) + continue;

- return sysfs_create_link_nowarn(&mem_blk->dev.kobj, - &node_devices[nid]->dev.kobj, - kobject_name(&node_devices[nid]->dev.kobj)); + return do_register_memory_block_under_node(nid, mem_blk); } /* mem section does not span the specified node */ return 0; }

+/* + * During hotplug we know that all pages in the memory block belong to the same + * node. + */ +static int register_mem_block_under_node_hotplug(struct memory_block *mem_blk, + void *arg) +{ + int nid = *(int *)arg; + + return do_register_memory_block_under_node(nid, mem_blk); +} + /* * Unregister a memory block device under the node it spans. Memory blocks * with multiple nodes cannot be offlined and therefore also never be removed. @@ -829,11 +846,19 @@ 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, + enum meminit_context context) { + walk_memory_blocks_func_t func; + + if (context == MEMINIT_HOTPLUG) + func = register_mem_block_under_node_hotplug; + else + func = register_mem_block_under_node_early; + return walk_memory_blocks(PFN_PHYS(start_pfn), PFN_PHYS(end_pfn - start_pfn), (void *)&nid, - register_mem_sect_under_node); + func); }

#ifdef CONFIG_HUGETLBFS diff --git a/include/linux/node.h b/include/linux/node.h index 4866f32a02d8..014ba3ab2efd 100644 --- a/include/linux/node.h +++ b/include/linux/node.h @@ -99,11 +99,13 @@ extern struct node *node_devices[]; 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); +int link_mem_sections(int nid, unsigned long start_pfn, + unsigned long end_pfn, + enum meminit_context context); #else static inline int link_mem_sections(int nid, unsigned long start_pfn, - unsigned long end_pfn) + unsigned long end_pfn, + enum meminit_context context) { return 0; } @@ -128,7 +130,8 @@ static inline int register_one_node(int nid) if (error) return error; /* link memory sections under this node */ - error = link_mem_sections(nid, start_pfn, end_pfn); + error = link_mem_sections(nid, start_pfn, end_pfn, + MEMINIT_EARLY); }

return error; diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 6a4b3a01e1b6..308beca3ffeb 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1082,7 +1082,8 @@ int __ref add_memory_resource(int nid, struct resource *res) }

/* link memory sections under this node.*/ - ret = link_mem_sections(nid, PFN_DOWN(start), PFN_UP(start + size - 1)); + ret = link_mem_sections(nid, PFN_DOWN(start), PFN_UP(start + size - 1), + MEMINIT_HOTPLUG); BUG_ON(ret);

/* create new memmap entry */