mm: don't rely on system state to detect hot-plug operations
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: 4fbce63391 ("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>
Link: https://lkml.kernel.org/r/20200915094143.79181-3-ldufour@linux.ibm.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Laurent Dufour
Linus Torvalds
parent
c1d0da8335
commit
f85086f95f
3 changed files with 64 additions and 35 deletions
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@ -761,41 +761,10 @@ static int __ref get_nid_for_pfn(unsigned long pfn)
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return pfn_to_nid(pfn);
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}
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/* register memory section under specified node if it spans that node */
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static int register_mem_sect_under_node(struct memory_block *mem_blk,
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void *arg)
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static int do_register_memory_block_under_node(int nid,
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struct memory_block *mem_blk)
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{
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unsigned long memory_block_pfns = memory_block_size_bytes() / PAGE_SIZE;
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unsigned long start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
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unsigned long end_pfn = start_pfn + memory_block_pfns - 1;
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int ret, nid = *(int *)arg;
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unsigned long pfn;
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for (pfn = start_pfn; pfn <= end_pfn; pfn++) {
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int page_nid;
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/*
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* memory block could have several absent sections from start.
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* skip pfn range from absent section
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*/
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if (!pfn_in_present_section(pfn)) {
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pfn = round_down(pfn + PAGES_PER_SECTION,
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PAGES_PER_SECTION) - 1;
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continue;
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}
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/*
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* We need to check if page belongs to nid only for the boot
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* case, during hotplug we know that all pages in the memory
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* block belong to the same node.
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*/
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if (system_state == SYSTEM_BOOTING) {
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page_nid = get_nid_for_pfn(pfn);
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if (page_nid < 0)
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continue;
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if (page_nid != nid)
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continue;
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}
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int ret;
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/*
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* If this memory block spans multiple nodes, we only indicate
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@ -812,11 +781,59 @@ static int register_mem_sect_under_node(struct memory_block *mem_blk,
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return sysfs_create_link_nowarn(&mem_blk->dev.kobj,
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&node_devices[nid]->dev.kobj,
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kobject_name(&node_devices[nid]->dev.kobj));
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}
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/* register memory section under specified node if it spans that node */
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static int register_mem_block_under_node_early(struct memory_block *mem_blk,
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void *arg)
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{
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unsigned long memory_block_pfns = memory_block_size_bytes() / PAGE_SIZE;
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unsigned long start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
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unsigned long end_pfn = start_pfn + memory_block_pfns - 1;
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int nid = *(int *)arg;
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unsigned long pfn;
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for (pfn = start_pfn; pfn <= end_pfn; pfn++) {
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int page_nid;
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/*
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* memory block could have several absent sections from start.
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* skip pfn range from absent section
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*/
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if (!pfn_in_present_section(pfn)) {
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pfn = round_down(pfn + PAGES_PER_SECTION,
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PAGES_PER_SECTION) - 1;
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continue;
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}
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/*
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* We need to check if page belongs to nid only at the boot
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* case because node's ranges can be interleaved.
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*/
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page_nid = get_nid_for_pfn(pfn);
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if (page_nid < 0)
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continue;
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if (page_nid != nid)
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continue;
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return do_register_memory_block_under_node(nid, mem_blk);
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}
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/* mem section does not span the specified node */
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return 0;
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}
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/*
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* During hotplug we know that all pages in the memory block belong to the same
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* node.
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*/
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static int register_mem_block_under_node_hotplug(struct memory_block *mem_blk,
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void *arg)
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{
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int nid = *(int *)arg;
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return do_register_memory_block_under_node(nid, mem_blk);
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}
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/*
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* Unregister a memory block device under the node it spans. Memory blocks
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* with multiple nodes cannot be offlined and therefore also never be removed.
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@ -832,11 +849,19 @@ void unregister_memory_block_under_nodes(struct memory_block *mem_blk)
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kobject_name(&node_devices[mem_blk->nid]->dev.kobj));
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}
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int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn)
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int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn,
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enum meminit_context context)
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{
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walk_memory_blocks_func_t func;
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if (context == MEMINIT_HOTPLUG)
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func = register_mem_block_under_node_hotplug;
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else
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func = register_mem_block_under_node_early;
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return walk_memory_blocks(PFN_PHYS(start_pfn),
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PFN_PHYS(end_pfn - start_pfn), (void *)&nid,
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register_mem_sect_under_node);
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func);
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}
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#ifdef CONFIG_HUGETLBFS
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@ -99,11 +99,13 @@ extern struct node *node_devices[];
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typedef void (*node_registration_func_t)(struct node *);
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#if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_NUMA)
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extern int link_mem_sections(int nid, unsigned long start_pfn,
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unsigned long end_pfn);
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int link_mem_sections(int nid, unsigned long start_pfn,
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unsigned long end_pfn,
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enum meminit_context context);
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#else
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static inline int link_mem_sections(int nid, unsigned long start_pfn,
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unsigned long end_pfn)
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unsigned long end_pfn,
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enum meminit_context context)
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{
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return 0;
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}
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@ -128,7 +130,8 @@ static inline int register_one_node(int nid)
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if (error)
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return error;
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/* link memory sections under this node */
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error = link_mem_sections(nid, start_pfn, end_pfn);
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error = link_mem_sections(nid, start_pfn, end_pfn,
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MEMINIT_EARLY);
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}
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return error;
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@ -1080,7 +1080,8 @@ int __ref add_memory_resource(int nid, struct resource *res)
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}
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/* link memory sections under this node.*/
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ret = link_mem_sections(nid, PFN_DOWN(start), PFN_UP(start + size - 1));
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ret = link_mem_sections(nid, PFN_DOWN(start), PFN_UP(start + size - 1),
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MEMINIT_HOTPLUG);
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BUG_ON(ret);
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/* create new memmap entry */
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