arch/powerpc/mm/numa.c

   1 /*
   2  * pSeries NUMA support
   3  *
   4  * Copyright (C) 2002 Anton Blanchard <anton@au.ibm.com>, IBM
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11 #include <linux/threads.h>
  12 #include <linux/bootmem.h>
  13 #include <linux/init.h>
  14 #include <linux/mm.h>
  15 #include <linux/mmzone.h>
  16 #include <linux/module.h>
  17 #include <linux/nodemask.h>
  18 #include <linux/cpu.h>
  19 #include <linux/notifier.h>
  20 #include <asm/sparsemem.h>
  21 #include <asm/lmb.h>
  22 #include <asm/system.h>
  23 #include <asm/smp.h>
  24
  25 static int numa_enabled = 1;
  26
  27 static int numa_debug;
  28 #define dbg(args...) if (numa_debug) { printk(KERN_INFO args); }
  29
  30 int numa_cpu_lookup_table[NR_CPUS];
  31 cpumask_t numa_cpumask_lookup_table[MAX_NUMNODES];
  32 struct pglist_data *node_data[MAX_NUMNODES];
  33
  34 EXPORT_SYMBOL(numa_cpu_lookup_table);
  35 EXPORT_SYMBOL(numa_cpumask_lookup_table);
  36 EXPORT_SYMBOL(node_data);
  37
  38 static bootmem_data_t __initdata plat_node_bdata[MAX_NUMNODES];
  39 static int min_common_depth;
  40 static int n_mem_addr_cells, n_mem_size_cells;
  41
  42 static void __cpuinit map_cpu_to_node(int cpu, int node)
  43 {
  44         numa_cpu_lookup_table[cpu] = node;
  45
  46         dbg("adding cpu %d to node %d\n", cpu, node);
  47
  48         if (!(cpu_isset(cpu, numa_cpumask_lookup_table[node])))
  49                 cpu_set(cpu, numa_cpumask_lookup_table[node]);
  50 }
  51
  52 #ifdef CONFIG_HOTPLUG_CPU
  53 static void unmap_cpu_from_node(unsigned long cpu)
  54 {
  55         int node = numa_cpu_lookup_table[cpu];
  56
  57         dbg("removing cpu %lu from node %d\n", cpu, node);
  58
  59         if (cpu_isset(cpu, numa_cpumask_lookup_table[node])) {
  60                 cpu_clear(cpu, numa_cpumask_lookup_table[node]);
  61         } else {
  62                 printk(KERN_ERR "WARNING: cpu %lu not found in node %d\n",
  63                        cpu, node);
  64         }
  65 }
  66 #endif /* CONFIG_HOTPLUG_CPU */
  67
  68 static struct device_node * __cpuinit find_cpu_node(unsigned int cpu)
  69 {
  70         unsigned int hw_cpuid = get_hard_smp_processor_id(cpu);
  71         struct device_node *cpu_node = NULL;
  72         const unsigned int *interrupt_server, *reg;
  73         int len;
  74
  75         while ((cpu_node = of_find_node_by_type(cpu_node, "cpu")) != NULL) {
  76                 /* Try interrupt server first */
  77                 interrupt_server = get_property(cpu_node,
  78                                         "ibm,ppc-interrupt-server#s", &len);
  79
  80                 len = len / sizeof(u32);
  81
  82                 if (interrupt_server && (len > 0)) {
  83                         while (len--) {
  84                                 if (interrupt_server[len] == hw_cpuid)
  85                                         return cpu_node;
  86                         }
  87                 } else {
  88                         reg = get_property(cpu_node, "reg", &len);
  89                         if (reg && (len > 0) && (reg[0] == hw_cpuid))
  90                                 return cpu_node;
  91                 }
  92         }
  93
  94         return NULL;
  95 }
  96
  97 /* must hold reference to node during call */
  98 static const int *of_get_associativity(struct device_node *dev)
  99 {
 100         return get_property(dev, "ibm,associativity", NULL);
 101 }
 102
 103 /* Returns nid in the range [0..MAX_NUMNODES-1], or -1 if no useful numa
 104  * info is found.
 105  */
 106 static int of_node_to_nid_single(struct device_node *device)
 107 {
 108         int nid = -1;
 109         const unsigned int *tmp;
 110
 111         if (min_common_depth == -1)
 112                 goto out;
 113
 114         tmp = of_get_associativity(device);
 115         if (!tmp)
 116                 goto out;
 117
 118         if (tmp[0] >= min_common_depth)
 119                 nid = tmp[min_common_depth];
 120
 121         /* POWER4 LPAR uses 0xffff as invalid node */
 122         if (nid == 0xffff || nid >= MAX_NUMNODES)
 123                 nid = -1;
 124 out:
 125         return nid;
 126 }
 127
 128 /* Walk the device tree upwards, looking for an associativity id */
 129 int of_node_to_nid(struct device_node *device)
 130 {
 131         struct device_node *tmp;
 132         int nid = -1;
 133
 134         of_node_get(device);
 135         while (device) {
 136                 nid = of_node_to_nid_single(device);
 137                 if (nid != -1)
 138                         break;
 139
 140                 tmp = device;
 141                 device = of_get_parent(tmp);
 142                 of_node_put(tmp);
 143         }
 144         of_node_put(device);
 145
 146         return nid;
 147 }
 148 EXPORT_SYMBOL_GPL(of_node_to_nid);
 149
 150 /*
 151  * In theory, the "ibm,associativity" property may contain multiple
 152  * associativity lists because a resource may be multiply connected
 153  * into the machine.  This resource then has different associativity
 154  * characteristics relative to its multiple connections.  We ignore
 155  * this for now.  We also assume that all cpu and memory sets have
 156  * their distances represented at a common level.  This won't be
 157  * true for heirarchical NUMA.
 158  *
 159  * In any case the ibm,associativity-reference-points should give
 160  * the correct depth for a normal NUMA system.
 161  *
 162  * - Dave Hansen <haveblue@us.ibm.com>
 163  */
 164 static int __init find_min_common_depth(void)
 165 {
 166         int depth;
 167         const unsigned int *ref_points;
 168         struct device_node *rtas_root;
 169         unsigned int len;
 170
 171         rtas_root = of_find_node_by_path("/rtas");
 172
 173         if (!rtas_root)
 174                 return -1;
 175
 176         /*
 177          * this property is 2 32-bit integers, each representing a level of
 178          * depth in the associativity nodes.  The first is for an SMP
 179          * configuration (should be all 0's) and the second is for a normal
 180          * NUMA configuration.
 181          */
 182         ref_points = get_property(rtas_root,
 183                         "ibm,associativity-reference-points", &len);
 184
 185         if ((len >= 1) && ref_points) {
 186                 depth = ref_points[1];
 187         } else {
 188                 dbg("NUMA: ibm,associativity-reference-points not found.\n");
 189                 depth = -1;
 190         }
 191         of_node_put(rtas_root);
 192
 193         return depth;
 194 }
 195
 196 static void __init get_n_mem_cells(int *n_addr_cells, int *n_size_cells)
 197 {
 198         struct device_node *memory = NULL;
 199
 200         memory = of_find_node_by_type(memory, "memory");
 201         if (!memory)
 202                 panic("numa.c: No memory nodes found!");
 203
 204         *n_addr_cells = prom_n_addr_cells(memory);
 205         *n_size_cells = prom_n_size_cells(memory);
 206         of_node_put(memory);
 207 }
 208
 209 static unsigned long __devinit read_n_cells(int n, const unsigned int **buf)
 210 {
 211         unsigned long result = 0;
 212
 213         while (n--) {
 214                 result = (result << 32) | **buf;
 215                 (*buf)++;
 216         }
 217         return result;
 218 }
 219
 220 /*
 221  * Figure out to which domain a cpu belongs and stick it there.
 222  * Return the id of the domain used.
 223  */
 224 static int __cpuinit numa_setup_cpu(unsigned long lcpu)
 225 {
 226         int nid = 0;
 227         struct device_node *cpu = find_cpu_node(lcpu);
 228
 229         if (!cpu) {
 230                 WARN_ON(1);
 231                 goto out;
 232         }
 233
 234         nid = of_node_to_nid_single(cpu);
 235
 236         if (nid < 0 || !node_online(nid))
 237                 nid = any_online_node(NODE_MASK_ALL);
 238 out:
 239         map_cpu_to_node(lcpu, nid);
 240
 241         of_node_put(cpu);
 242
 243         return nid;
 244 }
 245
 246 static int __cpuinit cpu_numa_callback(struct notifier_block *nfb,
 247                              unsigned long action,
 248                              void *hcpu)
 249 {
 250         unsigned long lcpu = (unsigned long)hcpu;
 251         int ret = NOTIFY_DONE;
 252
 253         switch (action) {
 254         case CPU_UP_PREPARE:
 255                 numa_setup_cpu(lcpu);
 256                 ret = NOTIFY_OK;
 257                 break;
 258 #ifdef CONFIG_HOTPLUG_CPU
 259         case CPU_DEAD:
 260         case CPU_UP_CANCELED:
 261                 unmap_cpu_from_node(lcpu);
 262                 break;
 263                 ret = NOTIFY_OK;
 264 #endif
 265         }
 266         return ret;
 267 }
 268
 269 /*
 270  * Check and possibly modify a memory region to enforce the memory limit.
 271  *
 272  * Returns the size the region should have to enforce the memory limit.
 273  * This will either be the original value of size, a truncated value,
 274  * or zero. If the returned value of size is 0 the region should be
 275  * discarded as it lies wholy above the memory limit.
 276  */
 277 static unsigned long __init numa_enforce_memory_limit(unsigned long start,
 278                                                       unsigned long size)
 279 {
 280         /*
 281          * We use lmb_end_of_DRAM() in here instead of memory_limit because
 282          * we've already adjusted it for the limit and it takes care of
 283          * having memory holes below the limit.
 284          */
 285
 286         if (! memory_limit)
 287                 return size;
 288
 289         if (start + size <= lmb_end_of_DRAM())
 290                 return size;
 291
 292         if (start >= lmb_end_of_DRAM())
 293                 return 0;
 294
 295         return lmb_end_of_DRAM() - start;
 296 }
 297
 298 static int __init parse_numa_properties(void)
 299 {
 300         struct device_node *cpu = NULL;
 301         struct device_node *memory = NULL;
 302         int default_nid = 0;
 303         unsigned long i;
 304
 305         if (numa_enabled == 0) {
 306                 printk(KERN_WARNING "NUMA disabled by user\n");
 307                 return -1;
 308         }
 309
 310         min_common_depth = find_min_common_depth();
 311
 312         if (min_common_depth < 0)
 313                 return min_common_depth;
 314
 315         dbg("NUMA associativity depth for CPU/Memory: %d\n", min_common_depth);
 316
 317         /*
 318          * Even though we connect cpus to numa domains later in SMP
 319          * init, we need to know the node ids now. This is because
 320          * each node to be onlined must have NODE_DATA etc backing it.
 321          */
 322         for_each_present_cpu(i) {
 323                 int nid;
 324
 325                 cpu = find_cpu_node(i);
 326                 BUG_ON(!cpu);
 327                 nid = of_node_to_nid_single(cpu);
 328                 of_node_put(cpu);
 329
 330                 /*
 331                  * Don't fall back to default_nid yet -- we will plug
 332                  * cpus into nodes once the memory scan has discovered
 333                  * the topology.
 334                  */
 335                 if (nid < 0)
 336                         continue;
 337                 node_set_online(nid);
 338         }
 339
 340         get_n_mem_cells(&n_mem_addr_cells, &n_mem_size_cells);
 341         memory = NULL;
 342         while ((memory = of_find_node_by_type(memory, "memory")) != NULL) {
 343                 unsigned long start;
 344                 unsigned long size;
 345                 int nid;
 346                 int ranges;
 347                 const unsigned int *memcell_buf;
 348                 unsigned int len;
 349
 350                 memcell_buf = get_property(memory,
 351                         "linux,usable-memory", &len);
 352                 if (!memcell_buf || len <= 0)
 353                         memcell_buf = get_property(memory, "reg", &len);
 354                 if (!memcell_buf || len <= 0)
 355                         continue;
 356
 357                 /* ranges in cell */
 358                 ranges = (len >> 2) / (n_mem_addr_cells + n_mem_size_cells);
 359 new_range:
 360                 /* these are order-sensitive, and modify the buffer pointer */
 361                 start = read_n_cells(n_mem_addr_cells, &memcell_buf);
 362                 size = read_n_cells(n_mem_size_cells, &memcell_buf);
 363
 364                 /*
 365                  * Assumption: either all memory nodes or none will
 366                  * have associativity properties.  If none, then
 367                  * everything goes to default_nid.
 368                  */
 369                 nid = of_node_to_nid_single(memory);
 370                 if (nid < 0)
 371                         nid = default_nid;
 372                 node_set_online(nid);
 373
 374                 if (!(size = numa_enforce_memory_limit(start, size))) {
 375                         if (--ranges)
 376                                 goto new_range;
 377                         else
 378                                 continue;
 379                 }
 380
 381                 add_active_range(nid, start >> PAGE_SHIFT,
 382                                 (start >> PAGE_SHIFT) + (size >> PAGE_SHIFT));
 383
 384                 if (--ranges)
 385                         goto new_range;
 386         }
 387
 388         return 0;
 389 }
 390
 391 static void __init setup_nonnuma(void)
 392 {
 393         unsigned long top_of_ram = lmb_end_of_DRAM();
 394         unsigned long total_ram = lmb_phys_mem_size();
 395         unsigned long start_pfn, end_pfn;
 396         unsigned int i;
 397
 398         printk(KERN_DEBUG "Top of RAM: 0x%lx, Total RAM: 0x%lx\n",
 399                top_of_ram, total_ram);
 400         printk(KERN_DEBUG "Memory hole size: %ldMB\n",
 401                (top_of_ram - total_ram) >> 20);
 402
 403         for (i = 0; i < lmb.memory.cnt; ++i) {
 404                 start_pfn = lmb.memory.region[i].base >> PAGE_SHIFT;
 405                 end_pfn = start_pfn + lmb_size_pages(&lmb.memory, i);
 406                 add_active_range(0, start_pfn, end_pfn);
 407         }
 408         node_set_online(0);
 409 }
 410
 411 void __init dump_numa_cpu_topology(void)
 412 {
 413         unsigned int node;
 414         unsigned int cpu, count;
 415
 416         if (min_common_depth == -1 || !numa_enabled)
 417                 return;
 418
 419         for_each_online_node(node) {
 420                 printk(KERN_DEBUG "Node %d CPUs:", node);
 421
 422                 count = 0;
 423                 /*
 424                  * If we used a CPU iterator here we would miss printing
 425                  * the holes in the cpumap.
 426                  */
 427                 for (cpu = 0; cpu < NR_CPUS; cpu++) {
 428                         if (cpu_isset(cpu, numa_cpumask_lookup_table[node])) {
 429                                 if (count == 0)
 430                                         printk(" %u", cpu);
 431                                 ++count;
 432                         } else {
 433                                 if (count > 1)
 434                                         printk("-%u", cpu - 1);
 435                                 count = 0;
 436                         }
 437                 }
 438
 439                 if (count > 1)
 440                         printk("-%u", NR_CPUS - 1);
 441                 printk("\n");
 442         }
 443 }
 444
 445 static void __init dump_numa_memory_topology(void)
 446 {
 447         unsigned int node;
 448         unsigned int count;
 449
 450         if (min_common_depth == -1 || !numa_enabled)
 451                 return;
 452
 453         for_each_online_node(node) {
 454                 unsigned long i;
 455
 456                 printk(KERN_DEBUG "Node %d Memory:", node);
 457
 458                 count = 0;
 459
 460                 for (i = 0; i < lmb_end_of_DRAM();
 461                      i += (1 << SECTION_SIZE_BITS)) {
 462                         if (early_pfn_to_nid(i >> PAGE_SHIFT) == node) {
 463                                 if (count == 0)
 464                                         printk(" 0x%lx", i);
 465                                 ++count;
 466                         } else {
 467                                 if (count > 0)
 468                                         printk("-0x%lx", i);
 469                                 count = 0;
 470                         }
 471                 }
 472
 473                 if (count > 0)
 474                         printk("-0x%lx", i);
 475                 printk("\n");
 476         }
 477 }
 478
 479 /*
 480  * Allocate some memory, satisfying the lmb or bootmem allocator where
 481  * required. nid is the preferred node and end is the physical address of
 482  * the highest address in the node.
 483  *
 484  * Returns the physical address of the memory.
 485  */
 486 static void __init *careful_allocation(int nid, unsigned long size,
 487                                        unsigned long align,
 488                                        unsigned long end_pfn)
 489 {
 490         int new_nid;
 491         unsigned long ret = __lmb_alloc_base(size, align, end_pfn << PAGE_SHIFT);
 492
 493         /* retry over all memory */
 494         if (!ret)
 495                 ret = __lmb_alloc_base(size, align, lmb_end_of_DRAM());
 496
 497         if (!ret)
 498                 panic("numa.c: cannot allocate %lu bytes on node %d",
 499                       size, nid);
 500
 501         /*
 502          * If the memory came from a previously allocated node, we must
 503          * retry with the bootmem allocator.
 504          */
 505         new_nid = early_pfn_to_nid(ret >> PAGE_SHIFT);
 506         if (new_nid < nid) {
 507                 ret = (unsigned long)__alloc_bootmem_node(NODE_DATA(new_nid),
 508                                 size, align, 0);
 509
 510                 if (!ret)
 511                         panic("numa.c: cannot allocate %lu bytes on node %d",
 512                               size, new_nid);
 513
 514                 ret = __pa(ret);
 515
 516                 dbg("alloc_bootmem %lx %lx\n", ret, size);
 517         }
 518
 519         return (void *)ret;
 520 }
 521
 522 static struct notifier_block __cpuinitdata ppc64_numa_nb = {
 523         .notifier_call = cpu_numa_callback,
 524         .priority = 1 /* Must run before sched domains notifier. */
 525 };
 526
 527 void __init do_init_bootmem(void)
 528 {
 529         int nid;
 530         unsigned int i;
 531
 532         min_low_pfn = 0;
 533         max_low_pfn = lmb_end_of_DRAM() >> PAGE_SHIFT;
 534         max_pfn = max_low_pfn;
 535
 536         if (parse_numa_properties())
 537                 setup_nonnuma();
 538         else
 539                 dump_numa_memory_topology();
 540
 541         register_cpu_notifier(&ppc64_numa_nb);
 542         cpu_numa_callback(&ppc64_numa_nb, CPU_UP_PREPARE,
 543                           (void *)(unsigned long)boot_cpuid);
 544
 545         for_each_online_node(nid) {
 546                 unsigned long start_pfn, end_pfn;
 547                 unsigned long bootmem_paddr;
 548                 unsigned long bootmap_pages;
 549
 550                 get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
 551
 552                 /* Allocate the node structure node local if possible */
 553                 NODE_DATA(nid) = careful_allocation(nid,
 554                                         sizeof(struct pglist_data),
 555                                         SMP_CACHE_BYTES, end_pfn);
 556                 NODE_DATA(nid) = __va(NODE_DATA(nid));
 557                 memset(NODE_DATA(nid), 0, sizeof(struct pglist_data));
 558
 559                 dbg("node %d\n", nid);
 560                 dbg("NODE_DATA() = %p\n", NODE_DATA(nid));
 561
 562                 NODE_DATA(nid)->bdata = &plat_node_bdata[nid];
 563                 NODE_DATA(nid)->node_start_pfn = start_pfn;
 564                 NODE_DATA(nid)->node_spanned_pages = end_pfn - start_pfn;
 565
 566                 if (NODE_DATA(nid)->node_spanned_pages == 0)
 567                         continue;
 568
 569                 dbg("start_paddr = %lx\n", start_pfn << PAGE_SHIFT);
 570                 dbg("end_paddr = %lx\n", end_pfn << PAGE_SHIFT);
 571
 572                 bootmap_pages = bootmem_bootmap_pages(end_pfn - start_pfn);
 573                 bootmem_paddr = (unsigned long)careful_allocation(nid,
 574                                         bootmap_pages << PAGE_SHIFT,
 575                                         PAGE_SIZE, end_pfn);
 576                 memset(__va(bootmem_paddr), 0, bootmap_pages << PAGE_SHIFT);
 577
 578                 dbg("bootmap_paddr = %lx\n", bootmem_paddr);
 579
 580                 init_bootmem_node(NODE_DATA(nid), bootmem_paddr >> PAGE_SHIFT,
 581                                   start_pfn, end_pfn);
 582
 583                 free_bootmem_with_active_regions(nid, end_pfn);
 584
 585                 /* Mark reserved regions on this node */
 586                 for (i = 0; i < lmb.reserved.cnt; i++) {
 587                         unsigned long physbase = lmb.reserved.region[i].base;
 588                         unsigned long size = lmb.reserved.region[i].size;
 589                         unsigned long start_paddr = start_pfn << PAGE_SHIFT;
 590                         unsigned long end_paddr = end_pfn << PAGE_SHIFT;
 591
 592                         if (early_pfn_to_nid(physbase >> PAGE_SHIFT) != nid &&
 593                             early_pfn_to_nid((physbase+size-1) >> PAGE_SHIFT) != nid)
 594                                 continue;
 595
 596                         if (physbase < end_paddr &&
 597                             (physbase+size) > start_paddr) {
 598                                 /* overlaps */
 599                                 if (physbase < start_paddr) {
 600                                         size -= start_paddr - physbase;
 601                                         physbase = start_paddr;
 602                                 }
 603
 604                                 if (size > end_paddr - physbase)
 605                                         size = end_paddr - physbase;
 606
 607                                 dbg("reserve_bootmem %lx %lx\n", physbase,
 608                                     size);
 609                                 reserve_bootmem_node(NODE_DATA(nid), physbase,
 610                                                      size);
 611                         }
 612                 }
 613
 614                 sparse_memory_present_with_active_regions(nid);
 615         }
 616 }
 617
 618 void __init paging_init(void)
 619 {
 620         unsigned long max_zone_pfns[MAX_NR_ZONES];
 621         memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
 622         max_zone_pfns[ZONE_DMA] = lmb_end_of_DRAM() >> PAGE_SHIFT;
 623         free_area_init_nodes(max_zone_pfns);
 624 }
 625
 626 static int __init early_numa(char *p)
 627 {
 628         if (!p)
 629                 return 0;
 630
 631         if (strstr(p, "off"))
 632                 numa_enabled = 0;
 633
 634         if (strstr(p, "debug"))
 635                 numa_debug = 1;
 636
 637         return 0;
 638 }
 639 early_param("numa", early_numa);
 640
 641 #ifdef CONFIG_MEMORY_HOTPLUG
 642 /*
 643  * Find the node associated with a hot added memory section.  Section
 644  * corresponds to a SPARSEMEM section, not an LMB.  It is assumed that
 645  * sections are fully contained within a single LMB.
 646  */
 647 int hot_add_scn_to_nid(unsigned long scn_addr)
 648 {
 649         struct device_node *memory = NULL;
 650         nodemask_t nodes;
 651         int default_nid = any_online_node(NODE_MASK_ALL);
 652         int nid;
 653
 654         if (!numa_enabled || (min_common_depth < 0))
 655                 return default_nid;
 656
 657         while ((memory = of_find_node_by_type(memory, "memory")) != NULL) {
 658                 unsigned long start, size;
 659                 int ranges;
 660                 const unsigned int *memcell_buf;
 661                 unsigned int len;
 662
 663                 memcell_buf = get_property(memory, "reg", &len);
 664                 if (!memcell_buf || len <= 0)
 665                         continue;
 666
 667                 /* ranges in cell */
 668                 ranges = (len >> 2) / (n_mem_addr_cells + n_mem_size_cells);
 669 ha_new_range:
 670                 start = read_n_cells(n_mem_addr_cells, &memcell_buf);
 671                 size = read_n_cells(n_mem_size_cells, &memcell_buf);
 672                 nid = of_node_to_nid_single(memory);
 673
 674                 /* Domains not present at boot default to 0 */
 675                 if (nid < 0 || !node_online(nid))
 676                         nid = default_nid;
 677
 678                 if ((scn_addr >= start) && (scn_addr < (start + size))) {
 679                         of_node_put(memory);
 680                         goto got_nid;
 681                 }
 682
 683                 if (--ranges)           /* process all ranges in cell */
 684                         goto ha_new_range;
 685         }
 686         BUG();  /* section address should be found above */
 687         return 0;
 688
 689         /* Temporary code to ensure that returned node is not empty */
 690 got_nid:
 691         nodes_setall(nodes);
 692         while (NODE_DATA(nid)->node_spanned_pages == 0) {
 693                 node_clear(nid, nodes);
 694                 nid = any_online_node(nodes);
 695         }
 696         return nid;
 697 }
 698 #endif /* CONFIG_MEMORY_HOTPLUG */