mm/memory-tiers.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/slab.h>
   3 #include <linux/lockdep.h>
   4 #include <linux/sysfs.h>
   5 #include <linux/kobject.h>
   6 #include <linux/memory.h>
   7 #include <linux/memory-tiers.h>
   8
   9 #include "internal.h"
  10
  11 struct memory_tier {
  12         /* hierarchy of memory tiers */
  13         struct list_head list;
  14         /* list of all memory types part of this tier */
  15         struct list_head memory_types;
  16         /*
  17          * start value of abstract distance. memory tier maps
  18          * an abstract distance  range,
  19          * adistance_start .. adistance_start + MEMTIER_CHUNK_SIZE
  20          */
  21         int adistance_start;
  22         struct device dev;
  23         /* All the nodes that are part of all the lower memory tiers. */
  24         nodemask_t lower_tier_mask;
  25 };
  26
  27 struct demotion_nodes {
  28         nodemask_t preferred;
  29 };
  30
  31 struct node_memory_type_map {
  32         struct memory_dev_type *memtype;
  33         int map_count;
  34 };
  35
  36 static DEFINE_MUTEX(memory_tier_lock);
  37 static LIST_HEAD(memory_tiers);
  38 static struct node_memory_type_map node_memory_types[MAX_NUMNODES];
  39 static struct memory_dev_type *default_dram_type;
  40
  41 static struct bus_type memory_tier_subsys = {
  42         .name = "memory_tiering",
  43         .dev_name = "memory_tier",
  44 };
  45
  46 #ifdef CONFIG_MIGRATION
  47 static int top_tier_adistance;
  48 /*
  49  * node_demotion[] examples:
  50  *
  51  * Example 1:
  52  *
  53  * Node 0 & 1 are CPU + DRAM nodes, node 2 & 3 are PMEM nodes.
  54  *
  55  * node distances:
  56  * node   0    1    2    3
  57  *    0  10   20   30   40
  58  *    1  20   10   40   30
  59  *    2  30   40   10   40
  60  *    3  40   30   40   10
  61  *
  62  * memory_tiers0 = 0-1
  63  * memory_tiers1 = 2-3
  64  *
  65  * node_demotion[0].preferred = 2
  66  * node_demotion[1].preferred = 3
  67  * node_demotion[2].preferred = <empty>
  68  * node_demotion[3].preferred = <empty>
  69  *
  70  * Example 2:
  71  *
  72  * Node 0 & 1 are CPU + DRAM nodes, node 2 is memory-only DRAM node.
  73  *
  74  * node distances:
  75  * node   0    1    2
  76  *    0  10   20   30
  77  *    1  20   10   30
  78  *    2  30   30   10
  79  *
  80  * memory_tiers0 = 0-2
  81  *
  82  * node_demotion[0].preferred = <empty>
  83  * node_demotion[1].preferred = <empty>
  84  * node_demotion[2].preferred = <empty>
  85  *
  86  * Example 3:
  87  *
  88  * Node 0 is CPU + DRAM nodes, Node 1 is HBM node, node 2 is PMEM node.
  89  *
  90  * node distances:
  91  * node   0    1    2
  92  *    0  10   20   30
  93  *    1  20   10   40
  94  *    2  30   40   10
  95  *
  96  * memory_tiers0 = 1
  97  * memory_tiers1 = 0
  98  * memory_tiers2 = 2
  99  *
 100  * node_demotion[0].preferred = 2
 101  * node_demotion[1].preferred = 0
 102  * node_demotion[2].preferred = <empty>
 103  *
 104  */
 105 static struct demotion_nodes *node_demotion __read_mostly;
 106 #endif /* CONFIG_MIGRATION */
 107
 108 static inline struct memory_tier *to_memory_tier(struct device *device)
 109 {
 110         return container_of(device, struct memory_tier, dev);
 111 }
 112
 113 static __always_inline nodemask_t get_memtier_nodemask(struct memory_tier *memtier)
 114 {
 115         nodemask_t nodes = NODE_MASK_NONE;
 116         struct memory_dev_type *memtype;
 117
 118         list_for_each_entry(memtype, &memtier->memory_types, tier_sibiling)
 119                 nodes_or(nodes, nodes, memtype->nodes);
 120
 121         return nodes;
 122 }
 123
 124 static void memory_tier_device_release(struct device *dev)
 125 {
 126         struct memory_tier *tier = to_memory_tier(dev);
 127         /*
 128          * synchronize_rcu in clear_node_memory_tier makes sure
 129          * we don't have rcu access to this memory tier.
 130          */
 131         kfree(tier);
 132 }
 133
 134 static ssize_t nodelist_show(struct device *dev,
 135                              struct device_attribute *attr, char *buf)
 136 {
 137         int ret;
 138         nodemask_t nmask;
 139
 140         mutex_lock(&memory_tier_lock);
 141         nmask = get_memtier_nodemask(to_memory_tier(dev));
 142         ret = sysfs_emit(buf, "%*pbl\n", nodemask_pr_args(&nmask));
 143         mutex_unlock(&memory_tier_lock);
 144         return ret;
 145 }
 146 static DEVICE_ATTR_RO(nodelist);
 147
 148 static struct attribute *memtier_dev_attrs[] = {
 149         &dev_attr_nodelist.attr,
 150         NULL
 151 };
 152
 153 static const struct attribute_group memtier_dev_group = {
 154         .attrs = memtier_dev_attrs,
 155 };
 156
 157 static const struct attribute_group *memtier_dev_groups[] = {
 158         &memtier_dev_group,
 159         NULL
 160 };
 161
 162 static struct memory_tier *find_create_memory_tier(struct memory_dev_type *memtype)
 163 {
 164         int ret;
 165         bool found_slot = false;
 166         struct memory_tier *memtier, *new_memtier;
 167         int adistance = memtype->adistance;
 168         unsigned int memtier_adistance_chunk_size = MEMTIER_CHUNK_SIZE;
 169
 170         lockdep_assert_held_once(&memory_tier_lock);
 171
 172         adistance = round_down(adistance, memtier_adistance_chunk_size);
 173         /*
 174          * If the memtype is already part of a memory tier,
 175          * just return that.
 176          */
 177         if (!list_empty(&memtype->tier_sibiling)) {
 178                 list_for_each_entry(memtier, &memory_tiers, list) {
 179                         if (adistance == memtier->adistance_start)
 180                                 return memtier;
 181                 }
 182                 WARN_ON(1);
 183                 return ERR_PTR(-EINVAL);
 184         }
 185
 186         list_for_each_entry(memtier, &memory_tiers, list) {
 187                 if (adistance == memtier->adistance_start) {
 188                         goto link_memtype;
 189                 } else if (adistance < memtier->adistance_start) {
 190                         found_slot = true;
 191                         break;
 192                 }
 193         }
 194
 195         new_memtier = kzalloc(sizeof(struct memory_tier), GFP_KERNEL);
 196         if (!new_memtier)
 197                 return ERR_PTR(-ENOMEM);
 198
 199         new_memtier->adistance_start = adistance;
 200         INIT_LIST_HEAD(&new_memtier->list);
 201         INIT_LIST_HEAD(&new_memtier->memory_types);
 202         if (found_slot)
 203                 list_add_tail(&new_memtier->list, &memtier->list);
 204         else
 205                 list_add_tail(&new_memtier->list, &memory_tiers);
 206
 207         new_memtier->dev.id = adistance >> MEMTIER_CHUNK_BITS;
 208         new_memtier->dev.bus = &memory_tier_subsys;
 209         new_memtier->dev.release = memory_tier_device_release;
 210         new_memtier->dev.groups = memtier_dev_groups;
 211
 212         ret = device_register(&new_memtier->dev);
 213         if (ret) {
 214                 list_del(&new_memtier->list);
 215                 put_device(&new_memtier->dev);
 216                 return ERR_PTR(ret);
 217         }
 218         memtier = new_memtier;
 219
 220 link_memtype:
 221         list_add(&memtype->tier_sibiling, &memtier->memory_types);
 222         return memtier;
 223 }
 224
 225 static struct memory_tier *__node_get_memory_tier(int node)
 226 {
 227         pg_data_t *pgdat;
 228
 229         pgdat = NODE_DATA(node);
 230         if (!pgdat)
 231                 return NULL;
 232         /*
 233          * Since we hold memory_tier_lock, we can avoid
 234          * RCU read locks when accessing the details. No
 235          * parallel updates are possible here.
 236          */
 237         return rcu_dereference_check(pgdat->memtier,
 238                                      lockdep_is_held(&memory_tier_lock));
 239 }
 240
 241 #ifdef CONFIG_MIGRATION
 242 bool node_is_toptier(int node)
 243 {
 244         bool toptier;
 245         pg_data_t *pgdat;
 246         struct memory_tier *memtier;
 247
 248         pgdat = NODE_DATA(node);
 249         if (!pgdat)
 250                 return false;
 251
 252         rcu_read_lock();
 253         memtier = rcu_dereference(pgdat->memtier);
 254         if (!memtier) {
 255                 toptier = true;
 256                 goto out;
 257         }
 258         if (memtier->adistance_start <= top_tier_adistance)
 259                 toptier = true;
 260         else
 261                 toptier = false;
 262 out:
 263         rcu_read_unlock();
 264         return toptier;
 265 }
 266
 267 void node_get_allowed_targets(pg_data_t *pgdat, nodemask_t *targets)
 268 {
 269         struct memory_tier *memtier;
 270
 271         /*
 272          * pg_data_t.memtier updates includes a synchronize_rcu()
 273          * which ensures that we either find NULL or a valid memtier
 274          * in NODE_DATA. protect the access via rcu_read_lock();
 275          */
 276         rcu_read_lock();
 277         memtier = rcu_dereference(pgdat->memtier);
 278         if (memtier)
 279                 *targets = memtier->lower_tier_mask;
 280         else
 281                 *targets = NODE_MASK_NONE;
 282         rcu_read_unlock();
 283 }
 284
 285 /**
 286  * next_demotion_node() - Get the next node in the demotion path
 287  * @node: The starting node to lookup the next node
 288  *
 289  * Return: node id for next memory node in the demotion path hierarchy
 290  * from @node; NUMA_NO_NODE if @node is terminal.  This does not keep
 291  * @node online or guarantee that it *continues* to be the next demotion
 292  * target.
 293  */
 294 int next_demotion_node(int node)
 295 {
 296         struct demotion_nodes *nd;
 297         int target;
 298
 299         if (!node_demotion)
 300                 return NUMA_NO_NODE;
 301
 302         nd = &node_demotion[node];
 303
 304         /*
 305          * node_demotion[] is updated without excluding this
 306          * function from running.
 307          *
 308          * Make sure to use RCU over entire code blocks if
 309          * node_demotion[] reads need to be consistent.
 310          */
 311         rcu_read_lock();
 312         /*
 313          * If there are multiple target nodes, just select one
 314          * target node randomly.
 315          *
 316          * In addition, we can also use round-robin to select
 317          * target node, but we should introduce another variable
 318          * for node_demotion[] to record last selected target node,
 319          * that may cause cache ping-pong due to the changing of
 320          * last target node. Or introducing per-cpu data to avoid
 321          * caching issue, which seems more complicated. So selecting
 322          * target node randomly seems better until now.
 323          */
 324         target = node_random(&nd->preferred);
 325         rcu_read_unlock();
 326
 327         return target;
 328 }
 329
 330 static void disable_all_demotion_targets(void)
 331 {
 332         struct memory_tier *memtier;
 333         int node;
 334
 335         for_each_node_state(node, N_MEMORY) {
 336                 node_demotion[node].preferred = NODE_MASK_NONE;
 337                 /*
 338                  * We are holding memory_tier_lock, it is safe
 339                  * to access pgda->memtier.
 340                  */
 341                 memtier = __node_get_memory_tier(node);
 342                 if (memtier)
 343                         memtier->lower_tier_mask = NODE_MASK_NONE;
 344         }
 345         /*
 346          * Ensure that the "disable" is visible across the system.
 347          * Readers will see either a combination of before+disable
 348          * state or disable+after.  They will never see before and
 349          * after state together.
 350          */
 351         synchronize_rcu();
 352 }
 353
 354 /*
 355  * Find an automatic demotion target for all memory
 356  * nodes. Failing here is OK.  It might just indicate
 357  * being at the end of a chain.
 358  */
 359 static void establish_demotion_targets(void)
 360 {
 361         struct memory_tier *memtier;
 362         struct demotion_nodes *nd;
 363         int target = NUMA_NO_NODE, node;
 364         int distance, best_distance;
 365         nodemask_t tier_nodes, lower_tier;
 366
 367         lockdep_assert_held_once(&memory_tier_lock);
 368
 369         if (!node_demotion)
 370                 return;
 371
 372         disable_all_demotion_targets();
 373
 374         for_each_node_state(node, N_MEMORY) {
 375                 best_distance = -1;
 376                 nd = &node_demotion[node];
 377
 378                 memtier = __node_get_memory_tier(node);
 379                 if (!memtier || list_is_last(&memtier->list, &memory_tiers))
 380                         continue;
 381                 /*
 382                  * Get the lower memtier to find the  demotion node list.
 383                  */
 384                 memtier = list_next_entry(memtier, list);
 385                 tier_nodes = get_memtier_nodemask(memtier);
 386                 /*
 387                  * find_next_best_node, use 'used' nodemask as a skip list.
 388                  * Add all memory nodes except the selected memory tier
 389                  * nodelist to skip list so that we find the best node from the
 390                  * memtier nodelist.
 391                  */
 392                 nodes_andnot(tier_nodes, node_states[N_MEMORY], tier_nodes);
 393
 394                 /*
 395                  * Find all the nodes in the memory tier node list of same best distance.
 396                  * add them to the preferred mask. We randomly select between nodes
 397                  * in the preferred mask when allocating pages during demotion.
 398                  */
 399                 do {
 400                         target = find_next_best_node(node, &tier_nodes);
 401                         if (target == NUMA_NO_NODE)
 402                                 break;
 403
 404                         distance = node_distance(node, target);
 405                         if (distance == best_distance || best_distance == -1) {
 406                                 best_distance = distance;
 407                                 node_set(target, nd->preferred);
 408                         } else {
 409                                 break;
 410                         }
 411                 } while (1);
 412         }
 413         /*
 414          * Promotion is allowed from a memory tier to higher
 415          * memory tier only if the memory tier doesn't include
 416          * compute. We want to skip promotion from a memory tier,
 417          * if any node that is part of the memory tier have CPUs.
 418          * Once we detect such a memory tier, we consider that tier
 419          * as top tiper from which promotion is not allowed.
 420          */
 421         list_for_each_entry_reverse(memtier, &memory_tiers, list) {
 422                 tier_nodes = get_memtier_nodemask(memtier);
 423                 nodes_and(tier_nodes, node_states[N_CPU], tier_nodes);
 424                 if (!nodes_empty(tier_nodes)) {
 425                         /*
 426                          * abstract distance below the max value of this memtier
 427                          * is considered toptier.
 428                          */
 429                         top_tier_adistance = memtier->adistance_start +
 430                                                 MEMTIER_CHUNK_SIZE - 1;
 431                         break;
 432                 }
 433         }
 434         /*
 435          * Now build the lower_tier mask for each node collecting node mask from
 436          * all memory tier below it. This allows us to fallback demotion page
 437          * allocation to a set of nodes that is closer the above selected
 438          * perferred node.
 439          */
 440         lower_tier = node_states[N_MEMORY];
 441         list_for_each_entry(memtier, &memory_tiers, list) {
 442                 /*
 443                  * Keep removing current tier from lower_tier nodes,
 444                  * This will remove all nodes in current and above
 445                  * memory tier from the lower_tier mask.
 446                  */
 447                 tier_nodes = get_memtier_nodemask(memtier);
 448                 nodes_andnot(lower_tier, lower_tier, tier_nodes);
 449                 memtier->lower_tier_mask = lower_tier;
 450         }
 451 }
 452
 453 #else
 454 static inline void establish_demotion_targets(void) {}
 455 #endif /* CONFIG_MIGRATION */
 456
 457 static inline void __init_node_memory_type(int node, struct memory_dev_type *memtype)
 458 {
 459         if (!node_memory_types[node].memtype)
 460                 node_memory_types[node].memtype = memtype;
 461         /*
 462          * for each device getting added in the same NUMA node
 463          * with this specific memtype, bump the map count. We
 464          * Only take memtype device reference once, so that
 465          * changing a node memtype can be done by droping the
 466          * only reference count taken here.
 467          */
 468
 469         if (node_memory_types[node].memtype == memtype) {
 470                 if (!node_memory_types[node].map_count++)
 471                         kref_get(&memtype->kref);
 472         }
 473 }
 474
 475 static struct memory_tier *set_node_memory_tier(int node)
 476 {
 477         struct memory_tier *memtier;
 478         struct memory_dev_type *memtype;
 479         pg_data_t *pgdat = NODE_DATA(node);
 480
 481
 482         lockdep_assert_held_once(&memory_tier_lock);
 483
 484         if (!node_state(node, N_MEMORY))
 485                 return ERR_PTR(-EINVAL);
 486
 487         __init_node_memory_type(node, default_dram_type);
 488
 489         memtype = node_memory_types[node].memtype;
 490         node_set(node, memtype->nodes);
 491         memtier = find_create_memory_tier(memtype);
 492         if (!IS_ERR(memtier))
 493                 rcu_assign_pointer(pgdat->memtier, memtier);
 494         return memtier;
 495 }
 496
 497 static void destroy_memory_tier(struct memory_tier *memtier)
 498 {
 499         list_del(&memtier->list);
 500         device_unregister(&memtier->dev);
 501 }
 502
 503 static bool clear_node_memory_tier(int node)
 504 {
 505         bool cleared = false;
 506         pg_data_t *pgdat;
 507         struct memory_tier *memtier;
 508
 509         pgdat = NODE_DATA(node);
 510         if (!pgdat)
 511                 return false;
 512
 513         /*
 514          * Make sure that anybody looking at NODE_DATA who finds
 515          * a valid memtier finds memory_dev_types with nodes still
 516          * linked to the memtier. We achieve this by waiting for
 517          * rcu read section to finish using synchronize_rcu.
 518          * This also enables us to free the destroyed memory tier
 519          * with kfree instead of kfree_rcu
 520          */
 521         memtier = __node_get_memory_tier(node);
 522         if (memtier) {
 523                 struct memory_dev_type *memtype;
 524
 525                 rcu_assign_pointer(pgdat->memtier, NULL);
 526                 synchronize_rcu();
 527                 memtype = node_memory_types[node].memtype;
 528                 node_clear(node, memtype->nodes);
 529                 if (nodes_empty(memtype->nodes)) {
 530                         list_del_init(&memtype->tier_sibiling);
 531                         if (list_empty(&memtier->memory_types))
 532                                 destroy_memory_tier(memtier);
 533                 }
 534                 cleared = true;
 535         }
 536         return cleared;
 537 }
 538
 539 static void release_memtype(struct kref *kref)
 540 {
 541         struct memory_dev_type *memtype;
 542
 543         memtype = container_of(kref, struct memory_dev_type, kref);
 544         kfree(memtype);
 545 }
 546
 547 struct memory_dev_type *alloc_memory_type(int adistance)
 548 {
 549         struct memory_dev_type *memtype;
 550
 551         memtype = kmalloc(sizeof(*memtype), GFP_KERNEL);
 552         if (!memtype)
 553                 return ERR_PTR(-ENOMEM);
 554
 555         memtype->adistance = adistance;
 556         INIT_LIST_HEAD(&memtype->tier_sibiling);
 557         memtype->nodes  = NODE_MASK_NONE;
 558         kref_init(&memtype->kref);
 559         return memtype;
 560 }
 561 EXPORT_SYMBOL_GPL(alloc_memory_type);
 562
 563 void put_memory_type(struct memory_dev_type *memtype)
 564 {
 565         kref_put(&memtype->kref, release_memtype);
 566 }
 567 EXPORT_SYMBOL_GPL(put_memory_type);
 568
 569 void init_node_memory_type(int node, struct memory_dev_type *memtype)
 570 {
 571
 572         mutex_lock(&memory_tier_lock);
 573         __init_node_memory_type(node, memtype);
 574         mutex_unlock(&memory_tier_lock);
 575 }
 576 EXPORT_SYMBOL_GPL(init_node_memory_type);
 577
 578 void clear_node_memory_type(int node, struct memory_dev_type *memtype)
 579 {
 580         mutex_lock(&memory_tier_lock);
 581         if (node_memory_types[node].memtype == memtype)
 582                 node_memory_types[node].map_count--;
 583         /*
 584          * If we umapped all the attached devices to this node,
 585          * clear the node memory type.
 586          */
 587         if (!node_memory_types[node].map_count) {
 588                 node_memory_types[node].memtype = NULL;
 589                 put_memory_type(memtype);
 590         }
 591         mutex_unlock(&memory_tier_lock);
 592 }
 593 EXPORT_SYMBOL_GPL(clear_node_memory_type);
 594
 595 static int __meminit memtier_hotplug_callback(struct notifier_block *self,
 596                                               unsigned long action, void *_arg)
 597 {
 598         struct memory_tier *memtier;
 599         struct memory_notify *arg = _arg;
 600
 601         /*
 602          * Only update the node migration order when a node is
 603          * changing status, like online->offline.
 604          */
 605         if (arg->status_change_nid < 0)
 606                 return notifier_from_errno(0);
 607
 608         switch (action) {
 609         case MEM_OFFLINE:
 610                 mutex_lock(&memory_tier_lock);
 611                 if (clear_node_memory_tier(arg->status_change_nid))
 612                         establish_demotion_targets();
 613                 mutex_unlock(&memory_tier_lock);
 614                 break;
 615         case MEM_ONLINE:
 616                 mutex_lock(&memory_tier_lock);
 617                 memtier = set_node_memory_tier(arg->status_change_nid);
 618                 if (!IS_ERR(memtier))
 619                         establish_demotion_targets();
 620                 mutex_unlock(&memory_tier_lock);
 621                 break;
 622         }
 623
 624         return notifier_from_errno(0);
 625 }
 626
 627 static int __init memory_tier_init(void)
 628 {
 629         int ret, node;
 630         struct memory_tier *memtier;
 631
 632         ret = subsys_virtual_register(&memory_tier_subsys, NULL);
 633         if (ret)
 634                 panic("%s() failed to register memory tier subsystem\n", __func__);
 635
 636 #ifdef CONFIG_MIGRATION
 637         node_demotion = kcalloc(nr_node_ids, sizeof(struct demotion_nodes),
 638                                 GFP_KERNEL);
 639         WARN_ON(!node_demotion);
 640 #endif
 641         mutex_lock(&memory_tier_lock);
 642         /*
 643          * For now we can have 4 faster memory tiers with smaller adistance
 644          * than default DRAM tier.
 645          */
 646         default_dram_type = alloc_memory_type(MEMTIER_ADISTANCE_DRAM);
 647         if (IS_ERR(default_dram_type))
 648                 panic("%s() failed to allocate default DRAM tier\n", __func__);
 649
 650         /*
 651          * Look at all the existing N_MEMORY nodes and add them to
 652          * default memory tier or to a tier if we already have memory
 653          * types assigned.
 654          */
 655         for_each_node_state(node, N_MEMORY) {
 656                 memtier = set_node_memory_tier(node);
 657                 if (IS_ERR(memtier))
 658                         /*
 659                          * Continue with memtiers we are able to setup
 660                          */
 661                         break;
 662         }
 663         establish_demotion_targets();
 664         mutex_unlock(&memory_tier_lock);
 665
 666         hotplug_memory_notifier(memtier_hotplug_callback, MEMTIER_HOTPLUG_PRI);
 667         return 0;
 668 }
 669 subsys_initcall(memory_tier_init);
 670
 671 bool numa_demotion_enabled = false;
 672
 673 #ifdef CONFIG_MIGRATION
 674 #ifdef CONFIG_SYSFS
 675 static ssize_t demotion_enabled_show(struct kobject *kobj,
 676                                      struct kobj_attribute *attr, char *buf)
 677 {
 678         return sysfs_emit(buf, "%s\n",
 679                           numa_demotion_enabled ? "true" : "false");
 680 }
 681
 682 static ssize_t demotion_enabled_store(struct kobject *kobj,
 683                                       struct kobj_attribute *attr,
 684                                       const char *buf, size_t count)
 685 {
 686         ssize_t ret;
 687
 688         ret = kstrtobool(buf, &numa_demotion_enabled);
 689         if (ret)
 690                 return ret;
 691
 692         return count;
 693 }
 694
 695 static struct kobj_attribute numa_demotion_enabled_attr =
 696         __ATTR_RW(demotion_enabled);
 697
 698 static struct attribute *numa_attrs[] = {
 699         &numa_demotion_enabled_attr.attr,
 700         NULL,
 701 };
 702
 703 static const struct attribute_group numa_attr_group = {
 704         .attrs = numa_attrs,
 705 };
 706
 707 static int __init numa_init_sysfs(void)
 708 {
 709         int err;
 710         struct kobject *numa_kobj;
 711
 712         numa_kobj = kobject_create_and_add("numa", mm_kobj);
 713         if (!numa_kobj) {
 714                 pr_err("failed to create numa kobject\n");
 715                 return -ENOMEM;
 716         }
 717         err = sysfs_create_group(numa_kobj, &numa_attr_group);
 718         if (err) {
 719                 pr_err("failed to register numa group\n");
 720                 goto delete_obj;
 721         }
 722         return 0;
 723
 724 delete_obj:
 725         kobject_put(numa_kobj);
 726         return err;
 727 }
 728 subsys_initcall(numa_init_sysfs);
 729 #endif /* CONFIG_SYSFS */
 730 #endif