drivers/base/memory.c

   1 /*
   2  * Memory subsystem support
   3  *
   4  * Written by Matt Tolentino <matthew.e.tolentino@intel.com>
   5  *            Dave Hansen <haveblue@us.ibm.com>
   6  *
   7  * This file provides the necessary infrastructure to represent
   8  * a SPARSEMEM-memory-model system's physical memory in /sysfs.
   9  * All arch-independent code that assumes MEMORY_HOTPLUG requires
  10  * SPARSEMEM should be contained here, or in mm/memory_hotplug.c.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/init.h>
  15 #include <linux/topology.h>
  16 #include <linux/capability.h>
  17 #include <linux/device.h>
  18 #include <linux/memory.h>
  19 #include <linux/memory_hotplug.h>
  20 #include <linux/mm.h>
  21 #include <linux/mutex.h>
  22 #include <linux/stat.h>
  23 #include <linux/slab.h>
  24
  25 #include <linux/atomic.h>
  26 #include <asm/uaccess.h>
  27
  28 static DEFINE_MUTEX(mem_sysfs_mutex);
  29
  30 #define MEMORY_CLASS_NAME       "memory"
  31
  32 #define to_memory_block(dev) container_of(dev, struct memory_block, dev)
  33
  34 static int sections_per_block;
  35
  36 static inline int base_memory_block_id(int section_nr)
  37 {
  38         return section_nr / sections_per_block;
  39 }
  40
  41 static int memory_subsys_online(struct device *dev);
  42 static int memory_subsys_offline(struct device *dev);
  43
  44 static struct bus_type memory_subsys = {
  45         .name = MEMORY_CLASS_NAME,
  46         .dev_name = MEMORY_CLASS_NAME,
  47         .online = memory_subsys_online,
  48         .offline = memory_subsys_offline,
  49 };
  50
  51 static BLOCKING_NOTIFIER_HEAD(memory_chain);
  52
  53 int register_memory_notifier(struct notifier_block *nb)
  54 {
  55         return blocking_notifier_chain_register(&memory_chain, nb);
  56 }
  57 EXPORT_SYMBOL(register_memory_notifier);
  58
  59 void unregister_memory_notifier(struct notifier_block *nb)
  60 {
  61         blocking_notifier_chain_unregister(&memory_chain, nb);
  62 }
  63 EXPORT_SYMBOL(unregister_memory_notifier);
  64
  65 static ATOMIC_NOTIFIER_HEAD(memory_isolate_chain);
  66
  67 int register_memory_isolate_notifier(struct notifier_block *nb)
  68 {
  69         return atomic_notifier_chain_register(&memory_isolate_chain, nb);
  70 }
  71 EXPORT_SYMBOL(register_memory_isolate_notifier);
  72
  73 void unregister_memory_isolate_notifier(struct notifier_block *nb)
  74 {
  75         atomic_notifier_chain_unregister(&memory_isolate_chain, nb);
  76 }
  77 EXPORT_SYMBOL(unregister_memory_isolate_notifier);
  78
  79 static void memory_block_release(struct device *dev)
  80 {
  81         struct memory_block *mem = to_memory_block(dev);
  82
  83         kfree(mem);
  84 }
  85
  86 unsigned long __weak memory_block_size_bytes(void)
  87 {
  88         return MIN_MEMORY_BLOCK_SIZE;
  89 }
  90
  91 static unsigned long get_memory_block_size(void)
  92 {
  93         unsigned long block_sz;
  94
  95         block_sz = memory_block_size_bytes();
  96
  97         /* Validate blk_sz is a power of 2 and not less than section size */
  98         if ((block_sz & (block_sz - 1)) || (block_sz < MIN_MEMORY_BLOCK_SIZE)) {
  99                 WARN_ON(1);
 100                 block_sz = MIN_MEMORY_BLOCK_SIZE;
 101         }
 102
 103         return block_sz;
 104 }
 105
 106 /*
 107  * use this as the physical section index that this memsection
 108  * uses.
 109  */
 110
 111 static ssize_t show_mem_start_phys_index(struct device *dev,
 112                         struct device_attribute *attr, char *buf)
 113 {
 114         struct memory_block *mem = to_memory_block(dev);
 115         unsigned long phys_index;
 116
 117         phys_index = mem->start_section_nr / sections_per_block;
 118         return sprintf(buf, "%08lx\n", phys_index);
 119 }
 120
 121 /*
 122  * Show whether the section of memory is likely to be hot-removable
 123  */
 124 static ssize_t show_mem_removable(struct device *dev,
 125                         struct device_attribute *attr, char *buf)
 126 {
 127         unsigned long i, pfn;
 128         int ret = 1;
 129         struct memory_block *mem = to_memory_block(dev);
 130
 131         for (i = 0; i < sections_per_block; i++) {
 132                 if (!present_section_nr(mem->start_section_nr + i))
 133                         continue;
 134                 pfn = section_nr_to_pfn(mem->start_section_nr + i);
 135                 ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
 136         }
 137
 138         return sprintf(buf, "%d\n", ret);
 139 }
 140
 141 /*
 142  * online, offline, going offline, etc.
 143  */
 144 static ssize_t show_mem_state(struct device *dev,
 145                         struct device_attribute *attr, char *buf)
 146 {
 147         struct memory_block *mem = to_memory_block(dev);
 148         ssize_t len = 0;
 149
 150         /*
 151          * We can probably put these states in a nice little array
 152          * so that they're not open-coded
 153          */
 154         switch (mem->state) {
 155                 case MEM_ONLINE:
 156                         len = sprintf(buf, "online\n");
 157                         break;
 158                 case MEM_OFFLINE:
 159                         len = sprintf(buf, "offline\n");
 160                         break;
 161                 case MEM_GOING_OFFLINE:
 162                         len = sprintf(buf, "going-offline\n");
 163                         break;
 164                 default:
 165                         len = sprintf(buf, "ERROR-UNKNOWN-%ld\n",
 166                                         mem->state);
 167                         WARN_ON(1);
 168                         break;
 169         }
 170
 171         return len;
 172 }
 173
 174 int memory_notify(unsigned long val, void *v)
 175 {
 176         return blocking_notifier_call_chain(&memory_chain, val, v);
 177 }
 178
 179 int memory_isolate_notify(unsigned long val, void *v)
 180 {
 181         return atomic_notifier_call_chain(&memory_isolate_chain, val, v);
 182 }
 183
 184 /*
 185  * The probe routines leave the pages reserved, just as the bootmem code does.
 186  * Make sure they're still that way.
 187  */
 188 static bool pages_correctly_reserved(unsigned long start_pfn)
 189 {
 190         int i, j;
 191         struct page *page;
 192         unsigned long pfn = start_pfn;
 193
 194         /*
 195          * memmap between sections is not contiguous except with
 196          * SPARSEMEM_VMEMMAP. We lookup the page once per section
 197          * and assume memmap is contiguous within each section
 198          */
 199         for (i = 0; i < sections_per_block; i++, pfn += PAGES_PER_SECTION) {
 200                 if (WARN_ON_ONCE(!pfn_valid(pfn)))
 201                         return false;
 202                 page = pfn_to_page(pfn);
 203
 204                 for (j = 0; j < PAGES_PER_SECTION; j++) {
 205                         if (PageReserved(page + j))
 206                                 continue;
 207
 208                         printk(KERN_WARNING "section number %ld page number %d "
 209                                 "not reserved, was it already online?\n",
 210                                 pfn_to_section_nr(pfn), j);
 211
 212                         return false;
 213                 }
 214         }
 215
 216         return true;
 217 }
 218
 219 /*
 220  * MEMORY_HOTPLUG depends on SPARSEMEM in mm/Kconfig, so it is
 221  * OK to have direct references to sparsemem variables in here.
 222  */
 223 static int
 224 memory_block_action(unsigned long phys_index, unsigned long action, int online_type)
 225 {
 226         unsigned long start_pfn;
 227         unsigned long nr_pages = PAGES_PER_SECTION * sections_per_block;
 228         struct page *first_page;
 229         int ret;
 230
 231         first_page = pfn_to_page(phys_index << PFN_SECTION_SHIFT);
 232         start_pfn = page_to_pfn(first_page);
 233
 234         switch (action) {
 235                 case MEM_ONLINE:
 236                         if (!pages_correctly_reserved(start_pfn))
 237                                 return -EBUSY;
 238
 239                         ret = online_pages(start_pfn, nr_pages, online_type);
 240                         break;
 241                 case MEM_OFFLINE:
 242                         ret = offline_pages(start_pfn, nr_pages);
 243                         break;
 244                 default:
 245                         WARN(1, KERN_WARNING "%s(%ld, %ld) unknown action: "
 246                              "%ld\n", __func__, phys_index, action, action);
 247                         ret = -EINVAL;
 248         }
 249
 250         return ret;
 251 }
 252
 253 static int memory_block_change_state(struct memory_block *mem,
 254                 unsigned long to_state, unsigned long from_state_req)
 255 {
 256         int ret = 0;
 257
 258         if (mem->state != from_state_req)
 259                 return -EINVAL;
 260
 261         if (to_state == MEM_OFFLINE)
 262                 mem->state = MEM_GOING_OFFLINE;
 263
 264         ret = memory_block_action(mem->start_section_nr, to_state,
 265                                 mem->online_type);
 266
 267         mem->state = ret ? from_state_req : to_state;
 268
 269         return ret;
 270 }
 271
 272 /* The device lock serializes operations on memory_subsys_[online|offline] */
 273 static int memory_subsys_online(struct device *dev)
 274 {
 275         struct memory_block *mem = to_memory_block(dev);
 276         int ret;
 277
 278         if (mem->state == MEM_ONLINE)
 279                 return 0;
 280
 281         /*
 282          * If we are called from store_mem_state(), online_type will be
 283          * set >= 0 Otherwise we were called from the device online
 284          * attribute and need to set the online_type.
 285          */
 286         if (mem->online_type < 0)
 287                 mem->online_type = MMOP_ONLINE_KEEP;
 288
 289         ret = memory_block_change_state(mem, MEM_ONLINE, MEM_OFFLINE);
 290
 291         /* clear online_type */
 292         mem->online_type = -1;
 293
 294         return ret;
 295 }
 296
 297 static int memory_subsys_offline(struct device *dev)
 298 {
 299         struct memory_block *mem = to_memory_block(dev);
 300
 301         if (mem->state == MEM_OFFLINE)
 302                 return 0;
 303
 304         return memory_block_change_state(mem, MEM_OFFLINE, MEM_ONLINE);
 305 }
 306
 307 static ssize_t
 308 store_mem_state(struct device *dev,
 309                 struct device_attribute *attr, const char *buf, size_t count)
 310 {
 311         struct memory_block *mem = to_memory_block(dev);
 312         int ret, online_type;
 313
 314         ret = lock_device_hotplug_sysfs();
 315         if (ret)
 316                 return ret;
 317
 318         if (sysfs_streq(buf, "online_kernel"))
 319                 online_type = MMOP_ONLINE_KERNEL;
 320         else if (sysfs_streq(buf, "online_movable"))
 321                 online_type = MMOP_ONLINE_MOVABLE;
 322         else if (sysfs_streq(buf, "online"))
 323                 online_type = MMOP_ONLINE_KEEP;
 324         else if (sysfs_streq(buf, "offline"))
 325                 online_type = MMOP_OFFLINE;
 326         else {
 327                 ret = -EINVAL;
 328                 goto err;
 329         }
 330
 331         switch (online_type) {
 332         case MMOP_ONLINE_KERNEL:
 333         case MMOP_ONLINE_MOVABLE:
 334         case MMOP_ONLINE_KEEP:
 335                 /*
 336                  * mem->online_type is not protected so there can be a
 337                  * race here.  However, when racing online, the first
 338                  * will succeed and the second will just return as the
 339                  * block will already be online.  The online type
 340                  * could be either one, but that is expected.
 341                  */
 342                 mem->online_type = online_type;
 343                 ret = device_online(&mem->dev);
 344                 break;
 345         case MMOP_OFFLINE:
 346                 ret = device_offline(&mem->dev);
 347                 break;
 348         default:
 349                 ret = -EINVAL; /* should never happen */
 350         }
 351
 352 err:
 353         unlock_device_hotplug();
 354
 355         if (ret)
 356                 return ret;
 357         return count;
 358 }
 359
 360 /*
 361  * phys_device is a bad name for this.  What I really want
 362  * is a way to differentiate between memory ranges that
 363  * are part of physical devices that constitute
 364  * a complete removable unit or fru.
 365  * i.e. do these ranges belong to the same physical device,
 366  * s.t. if I offline all of these sections I can then
 367  * remove the physical device?
 368  */
 369 static ssize_t show_phys_device(struct device *dev,
 370                                 struct device_attribute *attr, char *buf)
 371 {
 372         struct memory_block *mem = to_memory_block(dev);
 373         return sprintf(buf, "%d\n", mem->phys_device);
 374 }
 375
 376 static DEVICE_ATTR(phys_index, 0444, show_mem_start_phys_index, NULL);
 377 static DEVICE_ATTR(state, 0644, show_mem_state, store_mem_state);
 378 static DEVICE_ATTR(phys_device, 0444, show_phys_device, NULL);
 379 static DEVICE_ATTR(removable, 0444, show_mem_removable, NULL);
 380
 381 /*
 382  * Block size attribute stuff
 383  */
 384 static ssize_t
 385 print_block_size(struct device *dev, struct device_attribute *attr,
 386                  char *buf)
 387 {
 388         return sprintf(buf, "%lx\n", get_memory_block_size());
 389 }
 390
 391 static DEVICE_ATTR(block_size_bytes, 0444, print_block_size, NULL);
 392
 393 /*
 394  * Some architectures will have custom drivers to do this, and
 395  * will not need to do it from userspace.  The fake hot-add code
 396  * as well as ppc64 will do all of their discovery in userspace
 397  * and will require this interface.
 398  */
 399 #ifdef CONFIG_ARCH_MEMORY_PROBE
 400 static ssize_t
 401 memory_probe_store(struct device *dev, struct device_attribute *attr,
 402                    const char *buf, size_t count)
 403 {
 404         u64 phys_addr;
 405         int nid;
 406         int i, ret;
 407         unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block;
 408
 409         ret = kstrtoull(buf, 0, &phys_addr);
 410         if (ret)
 411                 return ret;
 412
 413         if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1))
 414                 return -EINVAL;
 415
 416         for (i = 0; i < sections_per_block; i++) {
 417                 nid = memory_add_physaddr_to_nid(phys_addr);
 418                 ret = add_memory(nid, phys_addr,
 419                                  PAGES_PER_SECTION << PAGE_SHIFT);
 420                 if (ret)
 421                         goto out;
 422
 423                 phys_addr += MIN_MEMORY_BLOCK_SIZE;
 424         }
 425
 426         ret = count;
 427 out:
 428         return ret;
 429 }
 430
 431 static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store);
 432 #endif
 433
 434 #ifdef CONFIG_MEMORY_FAILURE
 435 /*
 436  * Support for offlining pages of memory
 437  */
 438
 439 /* Soft offline a page */
 440 static ssize_t
 441 store_soft_offline_page(struct device *dev,
 442                         struct device_attribute *attr,
 443                         const char *buf, size_t count)
 444 {
 445         int ret;
 446         u64 pfn;
 447         if (!capable(CAP_SYS_ADMIN))
 448                 return -EPERM;
 449         if (kstrtoull(buf, 0, &pfn) < 0)
 450                 return -EINVAL;
 451         pfn >>= PAGE_SHIFT;
 452         if (!pfn_valid(pfn))
 453                 return -ENXIO;
 454         ret = soft_offline_page(pfn_to_page(pfn), 0);
 455         return ret == 0 ? count : ret;
 456 }
 457
 458 /* Forcibly offline a page, including killing processes. */
 459 static ssize_t
 460 store_hard_offline_page(struct device *dev,
 461                         struct device_attribute *attr,
 462                         const char *buf, size_t count)
 463 {
 464         int ret;
 465         u64 pfn;
 466         if (!capable(CAP_SYS_ADMIN))
 467                 return -EPERM;
 468         if (kstrtoull(buf, 0, &pfn) < 0)
 469                 return -EINVAL;
 470         pfn >>= PAGE_SHIFT;
 471         ret = memory_failure(pfn, 0, 0);
 472         return ret ? ret : count;
 473 }
 474
 475 static DEVICE_ATTR(soft_offline_page, S_IWUSR, NULL, store_soft_offline_page);
 476 static DEVICE_ATTR(hard_offline_page, S_IWUSR, NULL, store_hard_offline_page);
 477 #endif
 478
 479 /*
 480  * Note that phys_device is optional.  It is here to allow for
 481  * differentiation between which *physical* devices each
 482  * section belongs to...
 483  */
 484 int __weak arch_get_memory_phys_device(unsigned long start_pfn)
 485 {
 486         return 0;
 487 }
 488
 489 /*
 490  * A reference for the returned object is held and the reference for the
 491  * hinted object is released.
 492  */
 493 struct memory_block *find_memory_block_hinted(struct mem_section *section,
 494                                               struct memory_block *hint)
 495 {
 496         int block_id = base_memory_block_id(__section_nr(section));
 497         struct device *hintdev = hint ? &hint->dev : NULL;
 498         struct device *dev;
 499
 500         dev = subsys_find_device_by_id(&memory_subsys, block_id, hintdev);
 501         if (hint)
 502                 put_device(&hint->dev);
 503         if (!dev)
 504                 return NULL;
 505         return to_memory_block(dev);
 506 }
 507
 508 /*
 509  * For now, we have a linear search to go find the appropriate
 510  * memory_block corresponding to a particular phys_index. If
 511  * this gets to be a real problem, we can always use a radix
 512  * tree or something here.
 513  *
 514  * This could be made generic for all device subsystems.
 515  */
 516 struct memory_block *find_memory_block(struct mem_section *section)
 517 {
 518         return find_memory_block_hinted(section, NULL);
 519 }
 520
 521 static struct attribute *memory_memblk_attrs[] = {
 522         &dev_attr_phys_index.attr,
 523         &dev_attr_state.attr,
 524         &dev_attr_phys_device.attr,
 525         &dev_attr_removable.attr,
 526         NULL
 527 };
 528
 529 static struct attribute_group memory_memblk_attr_group = {
 530         .attrs = memory_memblk_attrs,
 531 };
 532
 533 static const struct attribute_group *memory_memblk_attr_groups[] = {
 534         &memory_memblk_attr_group,
 535         NULL,
 536 };
 537
 538 /*
 539  * register_memory - Setup a sysfs device for a memory block
 540  */
 541 static
 542 int register_memory(struct memory_block *memory)
 543 {
 544         memory->dev.bus = &memory_subsys;
 545         memory->dev.id = memory->start_section_nr / sections_per_block;
 546         memory->dev.release = memory_block_release;
 547         memory->dev.groups = memory_memblk_attr_groups;
 548         memory->dev.offline = memory->state == MEM_OFFLINE;
 549
 550         return device_register(&memory->dev);
 551 }
 552
 553 static int init_memory_block(struct memory_block **memory,
 554                              struct mem_section *section, unsigned long state)
 555 {
 556         struct memory_block *mem;
 557         unsigned long start_pfn;
 558         int scn_nr;
 559         int ret = 0;
 560
 561         mem = kzalloc(sizeof(*mem), GFP_KERNEL);
 562         if (!mem)
 563                 return -ENOMEM;
 564
 565         scn_nr = __section_nr(section);
 566         mem->start_section_nr =
 567                         base_memory_block_id(scn_nr) * sections_per_block;
 568         mem->end_section_nr = mem->start_section_nr + sections_per_block - 1;
 569         mem->state = state;
 570         mem->section_count++;
 571         start_pfn = section_nr_to_pfn(mem->start_section_nr);
 572         mem->phys_device = arch_get_memory_phys_device(start_pfn);
 573
 574         ret = register_memory(mem);
 575
 576         *memory = mem;
 577         return ret;
 578 }
 579
 580 static int add_memory_block(int base_section_nr)
 581 {
 582         struct memory_block *mem;
 583         int i, ret, section_count = 0, section_nr;
 584
 585         for (i = base_section_nr;
 586              (i < base_section_nr + sections_per_block) && i < NR_MEM_SECTIONS;
 587              i++) {
 588                 if (!present_section_nr(i))
 589                         continue;
 590                 if (section_count == 0)
 591                         section_nr = i;
 592                 section_count++;
 593         }
 594
 595         if (section_count == 0)
 596                 return 0;
 597         ret = init_memory_block(&mem, __nr_to_section(section_nr), MEM_ONLINE);
 598         if (ret)
 599                 return ret;
 600         mem->section_count = section_count;
 601         return 0;
 602 }
 603
 604
 605 /*
 606  * need an interface for the VM to add new memory regions,
 607  * but without onlining it.
 608  */
 609 int register_new_memory(int nid, struct mem_section *section)
 610 {
 611         int ret = 0;
 612         struct memory_block *mem;
 613
 614         mutex_lock(&mem_sysfs_mutex);
 615
 616         mem = find_memory_block(section);
 617         if (mem) {
 618                 mem->section_count++;
 619                 put_device(&mem->dev);
 620         } else {
 621                 ret = init_memory_block(&mem, section, MEM_OFFLINE);
 622                 if (ret)
 623                         goto out;
 624         }
 625
 626         if (mem->section_count == sections_per_block)
 627                 ret = register_mem_sect_under_node(mem, nid);
 628 out:
 629         mutex_unlock(&mem_sysfs_mutex);
 630         return ret;
 631 }
 632
 633 #ifdef CONFIG_MEMORY_HOTREMOVE
 634 static void
 635 unregister_memory(struct memory_block *memory)
 636 {
 637         BUG_ON(memory->dev.bus != &memory_subsys);
 638
 639         /* drop the ref. we got in remove_memory_block() */
 640         put_device(&memory->dev);
 641         device_unregister(&memory->dev);
 642 }
 643
 644 static int remove_memory_block(unsigned long node_id,
 645                                struct mem_section *section, int phys_device)
 646 {
 647         struct memory_block *mem;
 648
 649         mutex_lock(&mem_sysfs_mutex);
 650         mem = find_memory_block(section);
 651         unregister_mem_sect_under_nodes(mem, __section_nr(section));
 652
 653         mem->section_count--;
 654         if (mem->section_count == 0)
 655                 unregister_memory(mem);
 656         else
 657                 put_device(&mem->dev);
 658
 659         mutex_unlock(&mem_sysfs_mutex);
 660         return 0;
 661 }
 662
 663 int unregister_memory_section(struct mem_section *section)
 664 {
 665         if (!present_section(section))
 666                 return -EINVAL;
 667
 668         return remove_memory_block(0, section, 0);
 669 }
 670 #endif /* CONFIG_MEMORY_HOTREMOVE */
 671
 672 /* return true if the memory block is offlined, otherwise, return false */
 673 bool is_memblock_offlined(struct memory_block *mem)
 674 {
 675         return mem->state == MEM_OFFLINE;
 676 }
 677
 678 static struct attribute *memory_root_attrs[] = {
 679 #ifdef CONFIG_ARCH_MEMORY_PROBE
 680         &dev_attr_probe.attr,
 681 #endif
 682
 683 #ifdef CONFIG_MEMORY_FAILURE
 684         &dev_attr_soft_offline_page.attr,
 685         &dev_attr_hard_offline_page.attr,
 686 #endif
 687
 688         &dev_attr_block_size_bytes.attr,
 689         NULL
 690 };
 691
 692 static struct attribute_group memory_root_attr_group = {
 693         .attrs = memory_root_attrs,
 694 };
 695
 696 static const struct attribute_group *memory_root_attr_groups[] = {
 697         &memory_root_attr_group,
 698         NULL,
 699 };
 700
 701 /*
 702  * Initialize the sysfs support for memory devices...
 703  */
 704 int __init memory_dev_init(void)
 705 {
 706         unsigned int i;
 707         int ret;
 708         int err;
 709         unsigned long block_sz;
 710
 711         ret = subsys_system_register(&memory_subsys, memory_root_attr_groups);
 712         if (ret)
 713                 goto out;
 714
 715         block_sz = get_memory_block_size();
 716         sections_per_block = block_sz / MIN_MEMORY_BLOCK_SIZE;
 717
 718         /*
 719          * Create entries for memory sections that were found
 720          * during boot and have been initialized
 721          */
 722         mutex_lock(&mem_sysfs_mutex);
 723         for (i = 0; i < NR_MEM_SECTIONS; i += sections_per_block) {
 724                 err = add_memory_block(i);
 725                 if (!ret)
 726                         ret = err;
 727         }
 728         mutex_unlock(&mem_sysfs_mutex);
 729
 730 out:
 731         if (ret)
 732                 printk(KERN_ERR "%s() failed: %d\n", __func__, ret);
 733         return ret;
 734 }