mm/slob.c

   1 /*
   2  * SLOB Allocator: Simple List Of Blocks
   3  *
   4  * Matt Mackall <mpm@selenic.com> 12/30/03
   5  *
   6  * NUMA support by Paul Mundt, 2007.
   7  *
   8  * How SLOB works:
   9  *
  10  * The core of SLOB is a traditional K&R style heap allocator, with
  11  * support for returning aligned objects. The granularity of this
  12  * allocator is as little as 2 bytes, however typically most architectures
  13  * will require 4 bytes on 32-bit and 8 bytes on 64-bit.
  14  *
  15  * The slob heap is a set of linked list of pages from alloc_pages(),
  16  * and within each page, there is a singly-linked list of free blocks
  17  * (slob_t). The heap is grown on demand. To reduce fragmentation,
  18  * heap pages are segregated into three lists, with objects less than
  19  * 256 bytes, objects less than 1024 bytes, and all other objects.
  20  *
  21  * Allocation from heap involves first searching for a page with
  22  * sufficient free blocks (using a next-fit-like approach) followed by
  23  * a first-fit scan of the page. Deallocation inserts objects back
  24  * into the free list in address order, so this is effectively an
  25  * address-ordered first fit.
  26  *
  27  * Above this is an implementation of kmalloc/kfree. Blocks returned
  28  * from kmalloc are prepended with a 4-byte header with the kmalloc size.
  29  * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
  30  * alloc_pages() directly, allocating compound pages so the page order
  31  * does not have to be separately tracked, and also stores the exact
  32  * allocation size in page->private so that it can be used to accurately
  33  * provide ksize(). These objects are detected in kfree() because slob_page()
  34  * is false for them.
  35  *
  36  * SLAB is emulated on top of SLOB by simply calling constructors and
  37  * destructors for every SLAB allocation. Objects are returned with the
  38  * 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which
  39  * case the low-level allocator will fragment blocks to create the proper
  40  * alignment. Again, objects of page-size or greater are allocated by
  41  * calling alloc_pages(). As SLAB objects know their size, no separate
  42  * size bookkeeping is necessary and there is essentially no allocation
  43  * space overhead, and compound pages aren't needed for multi-page
  44  * allocations.
  45  *
  46  * NUMA support in SLOB is fairly simplistic, pushing most of the real
  47  * logic down to the page allocator, and simply doing the node accounting
  48  * on the upper levels. In the event that a node id is explicitly
  49  * provided, alloc_pages_exact_node() with the specified node id is used
  50  * instead. The common case (or when the node id isn't explicitly provided)
  51  * will default to the current node, as per numa_node_id().
  52  *
  53  * Node aware pages are still inserted in to the global freelist, and
  54  * these are scanned for by matching against the node id encoded in the
  55  * page flags. As a result, block allocations that can be satisfied from
  56  * the freelist will only be done so on pages residing on the same node,
  57  * in order to prevent random node placement.
  58  */
  59
  60 #include <linux/kernel.h>
  61 #include <linux/slab.h>
  62 #include <linux/mm.h>
  63 #include <linux/swap.h> /* struct reclaim_state */
  64 #include <linux/cache.h>
  65 #include <linux/init.h>
  66 #include <linux/module.h>
  67 #include <linux/rcupdate.h>
  68 #include <linux/list.h>
  69 #include <linux/kmemtrace.h>
  70 #include <linux/kmemleak.h>
  71 #include <asm/atomic.h>
  72
  73 /*
  74  * slob_block has a field 'units', which indicates size of block if +ve,
  75  * or offset of next block if -ve (in SLOB_UNITs).
  76  *
  77  * Free blocks of size 1 unit simply contain the offset of the next block.
  78  * Those with larger size contain their size in the first SLOB_UNIT of
  79  * memory, and the offset of the next free block in the second SLOB_UNIT.
  80  */
  81 #if PAGE_SIZE <= (32767 * 2)
  82 typedef s16 slobidx_t;
  83 #else
  84 typedef s32 slobidx_t;
  85 #endif
  86
  87 struct slob_block {
  88         slobidx_t units;
  89 };
  90 typedef struct slob_block slob_t;
  91
  92 /*
  93  * We use struct page fields to manage some slob allocation aspects,
  94  * however to avoid the horrible mess in include/linux/mm_types.h, we'll
  95  * just define our own struct page type variant here.
  96  */
  97 struct slob_page {
  98         union {
  99                 struct {
 100                         unsigned long flags;    /* mandatory */
 101                         atomic_t _count;        /* mandatory */
 102                         slobidx_t units;        /* free units left in page */
 103                         unsigned long pad[2];
 104                         slob_t *free;           /* first free slob_t in page */
 105                         struct list_head list;  /* linked list of free pages */
 106                 };
 107                 struct page page;
 108         };
 109 };
 110 static inline void struct_slob_page_wrong_size(void)
 111 { BUILD_BUG_ON(sizeof(struct slob_page) != sizeof(struct page)); }
 112
 113 /*
 114  * free_slob_page: call before a slob_page is returned to the page allocator.
 115  */
 116 static inline void free_slob_page(struct slob_page *sp)
 117 {
 118         reset_page_mapcount(&sp->page);
 119         sp->page.mapping = NULL;
 120 }
 121
 122 /*
 123  * All partially free slob pages go on these lists.
 124  */
 125 #define SLOB_BREAK1 256
 126 #define SLOB_BREAK2 1024
 127 static LIST_HEAD(free_slob_small);
 128 static LIST_HEAD(free_slob_medium);
 129 static LIST_HEAD(free_slob_large);
 130
 131 /*
 132  * is_slob_page: True for all slob pages (false for bigblock pages)
 133  */
 134 static inline int is_slob_page(struct slob_page *sp)
 135 {
 136         return PageSlab((struct page *)sp);
 137 }
 138
 139 static inline void set_slob_page(struct slob_page *sp)
 140 {
 141         __SetPageSlab((struct page *)sp);
 142 }
 143
 144 static inline void clear_slob_page(struct slob_page *sp)
 145 {
 146         __ClearPageSlab((struct page *)sp);
 147 }
 148
 149 static inline struct slob_page *slob_page(const void *addr)
 150 {
 151         return (struct slob_page *)virt_to_page(addr);
 152 }
 153
 154 /*
 155  * slob_page_free: true for pages on free_slob_pages list.
 156  */
 157 static inline int slob_page_free(struct slob_page *sp)
 158 {
 159         return PageSlobFree((struct page *)sp);
 160 }
 161
 162 static void set_slob_page_free(struct slob_page *sp, struct list_head *list)
 163 {
 164         list_add(&sp->list, list);
 165         __SetPageSlobFree((struct page *)sp);
 166 }
 167
 168 static inline void clear_slob_page_free(struct slob_page *sp)
 169 {
 170         list_del(&sp->list);
 171         __ClearPageSlobFree((struct page *)sp);
 172 }
 173
 174 #define SLOB_UNIT sizeof(slob_t)
 175 #define SLOB_UNITS(size) (((size) + SLOB_UNIT - 1)/SLOB_UNIT)
 176 #define SLOB_ALIGN L1_CACHE_BYTES
 177
 178 /*
 179  * struct slob_rcu is inserted at the tail of allocated slob blocks, which
 180  * were created with a SLAB_DESTROY_BY_RCU slab. slob_rcu is used to free
 181  * the block using call_rcu.
 182  */
 183 struct slob_rcu {
 184         struct rcu_head head;
 185         int size;
 186 };
 187
 188 /*
 189  * slob_lock protects all slob allocator structures.
 190  */
 191 static DEFINE_SPINLOCK(slob_lock);
 192
 193 /*
 194  * Encode the given size and next info into a free slob block s.
 195  */
 196 static void set_slob(slob_t *s, slobidx_t size, slob_t *next)
 197 {
 198         slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
 199         slobidx_t offset = next - base;
 200
 201         if (size > 1) {
 202                 s[0].units = size;
 203                 s[1].units = offset;
 204         } else
 205                 s[0].units = -offset;
 206 }
 207
 208 /*
 209  * Return the size of a slob block.
 210  */
 211 static slobidx_t slob_units(slob_t *s)
 212 {
 213         if (s->units > 0)
 214                 return s->units;
 215         return 1;
 216 }
 217
 218 /*
 219  * Return the next free slob block pointer after this one.
 220  */
 221 static slob_t *slob_next(slob_t *s)
 222 {
 223         slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
 224         slobidx_t next;
 225
 226         if (s[0].units < 0)
 227                 next = -s[0].units;
 228         else
 229                 next = s[1].units;
 230         return base+next;
 231 }
 232
 233 /*
 234  * Returns true if s is the last free block in its page.
 235  */
 236 static int slob_last(slob_t *s)
 237 {
 238         return !((unsigned long)slob_next(s) & ~PAGE_MASK);
 239 }
 240
 241 static void *slob_new_pages(gfp_t gfp, int order, int node)
 242 {
 243         void *page;
 244
 245 #ifdef CONFIG_NUMA
 246         if (node != -1)
 247                 page = alloc_pages_exact_node(node, gfp, order);
 248         else
 249 #endif
 250                 page = alloc_pages(gfp, order);
 251
 252         if (!page)
 253                 return NULL;
 254
 255         return page_address(page);
 256 }
 257
 258 static void slob_free_pages(void *b, int order)
 259 {
 260         if (current->reclaim_state)
 261                 current->reclaim_state->reclaimed_slab += 1 << order;
 262         free_pages((unsigned long)b, order);
 263 }
 264
 265 /*
 266  * Allocate a slob block within a given slob_page sp.
 267  */
 268 static void *slob_page_alloc(struct slob_page *sp, size_t size, int align)
 269 {
 270         slob_t *prev, *cur, *aligned = NULL;
 271         int delta = 0, units = SLOB_UNITS(size);
 272
 273         for (prev = NULL, cur = sp->free; ; prev = cur, cur = slob_next(cur)) {
 274                 slobidx_t avail = slob_units(cur);
 275
 276                 if (align) {
 277                         aligned = (slob_t *)ALIGN((unsigned long)cur, align);
 278                         delta = aligned - cur;
 279                 }
 280                 if (avail >= units + delta) { /* room enough? */
 281                         slob_t *next;
 282
 283                         if (delta) { /* need to fragment head to align? */
 284                                 next = slob_next(cur);
 285                                 set_slob(aligned, avail - delta, next);
 286                                 set_slob(cur, delta, aligned);
 287                                 prev = cur;
 288                                 cur = aligned;
 289                                 avail = slob_units(cur);
 290                         }
 291
 292                         next = slob_next(cur);
 293                         if (avail == units) { /* exact fit? unlink. */
 294                                 if (prev)
 295                                         set_slob(prev, slob_units(prev), next);
 296                                 else
 297                                         sp->free = next;
 298                         } else { /* fragment */
 299                                 if (prev)
 300                                         set_slob(prev, slob_units(prev), cur + units);
 301                                 else
 302                                         sp->free = cur + units;
 303                                 set_slob(cur + units, avail - units, next);
 304                         }
 305
 306                         sp->units -= units;
 307                         if (!sp->units)
 308                                 clear_slob_page_free(sp);
 309                         return cur;
 310                 }
 311                 if (slob_last(cur))
 312                         return NULL;
 313         }
 314 }
 315
 316 /*
 317  * slob_alloc: entry point into the slob allocator.
 318  */
 319 static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
 320 {
 321         struct slob_page *sp;
 322         struct list_head *prev;
 323         struct list_head *slob_list;
 324         slob_t *b = NULL;
 325         unsigned long flags;
 326
 327         if (size < SLOB_BREAK1)
 328                 slob_list = &free_slob_small;
 329         else if (size < SLOB_BREAK2)
 330                 slob_list = &free_slob_medium;
 331         else
 332                 slob_list = &free_slob_large;
 333
 334         spin_lock_irqsave(&slob_lock, flags);
 335         /* Iterate through each partially free page, try to find room */
 336         list_for_each_entry(sp, slob_list, list) {
 337 #ifdef CONFIG_NUMA
 338                 /*
 339                  * If there's a node specification, search for a partial
 340                  * page with a matching node id in the freelist.
 341                  */
 342                 if (node != -1 && page_to_nid(&sp->page) != node)
 343                         continue;
 344 #endif
 345                 /* Enough room on this page? */
 346                 if (sp->units < SLOB_UNITS(size))
 347                         continue;
 348
 349                 /* Attempt to alloc */
 350                 prev = sp->list.prev;
 351                 b = slob_page_alloc(sp, size, align);
 352                 if (!b)
 353                         continue;
 354
 355                 /* Improve fragment distribution and reduce our average
 356                  * search time by starting our next search here. (see
 357                  * Knuth vol 1, sec 2.5, pg 449) */
 358                 if (prev != slob_list->prev &&
 359                                 slob_list->next != prev->next)
 360                         list_move_tail(slob_list, prev->next);
 361                 break;
 362         }
 363         spin_unlock_irqrestore(&slob_lock, flags);
 364
 365         /* Not enough space: must allocate a new page */
 366         if (!b) {
 367                 b = slob_new_pages(gfp & ~__GFP_ZERO, 0, node);
 368                 if (!b)
 369                         return NULL;
 370                 sp = slob_page(b);
 371                 set_slob_page(sp);
 372
 373                 spin_lock_irqsave(&slob_lock, flags);
 374                 sp->units = SLOB_UNITS(PAGE_SIZE);
 375                 sp->free = b;
 376                 INIT_LIST_HEAD(&sp->list);
 377                 set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
 378                 set_slob_page_free(sp, slob_list);
 379                 b = slob_page_alloc(sp, size, align);
 380                 BUG_ON(!b);
 381                 spin_unlock_irqrestore(&slob_lock, flags);
 382         }
 383         if (unlikely((gfp & __GFP_ZERO) && b))
 384                 memset(b, 0, size);
 385         return b;
 386 }
 387
 388 /*
 389  * slob_free: entry point into the slob allocator.
 390  */
 391 static void slob_free(void *block, int size)
 392 {
 393         struct slob_page *sp;
 394         slob_t *prev, *next, *b = (slob_t *)block;
 395         slobidx_t units;
 396         unsigned long flags;
 397
 398         if (unlikely(ZERO_OR_NULL_PTR(block)))
 399                 return;
 400         BUG_ON(!size);
 401
 402         sp = slob_page(block);
 403         units = SLOB_UNITS(size);
 404
 405         spin_lock_irqsave(&slob_lock, flags);
 406
 407         if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) {
 408                 /* Go directly to page allocator. Do not pass slob allocator */
 409                 if (slob_page_free(sp))
 410                         clear_slob_page_free(sp);
 411                 spin_unlock_irqrestore(&slob_lock, flags);
 412                 clear_slob_page(sp);
 413                 free_slob_page(sp);
 414                 slob_free_pages(b, 0);
 415                 return;
 416         }
 417
 418         if (!slob_page_free(sp)) {
 419                 /* This slob page is about to become partially free. Easy! */
 420                 sp->units = units;
 421                 sp->free = b;
 422                 set_slob(b, units,
 423                         (void *)((unsigned long)(b +
 424                                         SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));
 425                 set_slob_page_free(sp, &free_slob_small);
 426                 goto out;
 427         }
 428
 429         /*
 430          * Otherwise the page is already partially free, so find reinsertion
 431          * point.
 432          */
 433         sp->units += units;
 434
 435         if (b < sp->free) {
 436                 if (b + units == sp->free) {
 437                         units += slob_units(sp->free);
 438                         sp->free = slob_next(sp->free);
 439                 }
 440                 set_slob(b, units, sp->free);
 441                 sp->free = b;
 442         } else {
 443                 prev = sp->free;
 444                 next = slob_next(prev);
 445                 while (b > next) {
 446                         prev = next;
 447                         next = slob_next(prev);
 448                 }
 449
 450                 if (!slob_last(prev) && b + units == next) {
 451                         units += slob_units(next);
 452                         set_slob(b, units, slob_next(next));
 453                 } else
 454                         set_slob(b, units, next);
 455
 456                 if (prev + slob_units(prev) == b) {
 457                         units = slob_units(b) + slob_units(prev);
 458                         set_slob(prev, units, slob_next(b));
 459                 } else
 460                         set_slob(prev, slob_units(prev), b);
 461         }
 462 out:
 463         spin_unlock_irqrestore(&slob_lock, flags);
 464 }
 465
 466 /*
 467  * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
 468  */
 469
 470 #ifndef ARCH_KMALLOC_MINALIGN
 471 #define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long)
 472 #endif
 473
 474 #ifndef ARCH_SLAB_MINALIGN
 475 #define ARCH_SLAB_MINALIGN __alignof__(unsigned long)
 476 #endif
 477
 478 void *__kmalloc_node(size_t size, gfp_t gfp, int node)
 479 {
 480         unsigned int *m;
 481         int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
 482         void *ret;
 483
 484         lockdep_trace_alloc(gfp);
 485
 486         if (size < PAGE_SIZE - align) {
 487                 if (!size)
 488                         return ZERO_SIZE_PTR;
 489
 490                 m = slob_alloc(size + align, gfp, align, node);
 491
 492                 if (!m)
 493                         return NULL;
 494                 *m = size;
 495                 ret = (void *)m + align;
 496
 497                 trace_kmalloc_node(_RET_IP_, ret,
 498                                    size, size + align, gfp, node);
 499         } else {
 500                 unsigned int order = get_order(size);
 501
 502                 ret = slob_new_pages(gfp | __GFP_COMP, get_order(size), node);
 503                 if (ret) {
 504                         struct page *page;
 505                         page = virt_to_page(ret);
 506                         page->private = size;
 507                 }
 508
 509                 trace_kmalloc_node(_RET_IP_, ret,
 510                                    size, PAGE_SIZE << order, gfp, node);
 511         }
 512
 513         kmemleak_alloc(ret, size, 1, gfp);
 514         return ret;
 515 }
 516 EXPORT_SYMBOL(__kmalloc_node);
 517
 518 void kfree(const void *block)
 519 {
 520         struct slob_page *sp;
 521
 522         trace_kfree(_RET_IP_, block);
 523
 524         if (unlikely(ZERO_OR_NULL_PTR(block)))
 525                 return;
 526         kmemleak_free(block);
 527
 528         sp = slob_page(block);
 529         if (is_slob_page(sp)) {
 530                 int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
 531                 unsigned int *m = (unsigned int *)(block - align);
 532                 slob_free(m, *m + align);
 533         } else
 534                 put_page(&sp->page);
 535 }
 536 EXPORT_SYMBOL(kfree);
 537
 538 /* can't use ksize for kmem_cache_alloc memory, only kmalloc */
 539 size_t ksize(const void *block)
 540 {
 541         struct slob_page *sp;
 542
 543         BUG_ON(!block);
 544         if (unlikely(block == ZERO_SIZE_PTR))
 545                 return 0;
 546
 547         sp = slob_page(block);
 548         if (is_slob_page(sp)) {
 549                 int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
 550                 unsigned int *m = (unsigned int *)(block - align);
 551                 return SLOB_UNITS(*m) * SLOB_UNIT;
 552         } else
 553                 return sp->page.private;
 554 }
 555 EXPORT_SYMBOL(ksize);
 556
 557 struct kmem_cache {
 558         unsigned int size, align;
 559         unsigned long flags;
 560         const char *name;
 561         void (*ctor)(void *);
 562 };
 563
 564 struct kmem_cache *kmem_cache_create(const char *name, size_t size,
 565         size_t align, unsigned long flags, void (*ctor)(void *))
 566 {
 567         struct kmem_cache *c;
 568
 569         c = slob_alloc(sizeof(struct kmem_cache),
 570                 GFP_KERNEL, ARCH_KMALLOC_MINALIGN, -1);
 571
 572         if (c) {
 573                 c->name = name;
 574                 c->size = size;
 575                 if (flags & SLAB_DESTROY_BY_RCU) {
 576                         /* leave room for rcu footer at the end of object */
 577                         c->size += sizeof(struct slob_rcu);
 578                 }
 579                 c->flags = flags;
 580                 c->ctor = ctor;
 581                 /* ignore alignment unless it's forced */
 582                 c->align = (flags & SLAB_HWCACHE_ALIGN) ? SLOB_ALIGN : 0;
 583                 if (c->align < ARCH_SLAB_MINALIGN)
 584                         c->align = ARCH_SLAB_MINALIGN;
 585                 if (c->align < align)
 586                         c->align = align;
 587         } else if (flags & SLAB_PANIC)
 588                 panic("Cannot create slab cache %s\n", name);
 589
 590         kmemleak_alloc(c, sizeof(struct kmem_cache), 1, GFP_KERNEL);
 591         return c;
 592 }
 593 EXPORT_SYMBOL(kmem_cache_create);
 594
 595 void kmem_cache_destroy(struct kmem_cache *c)
 596 {
 597         kmemleak_free(c);
 598         if (c->flags & SLAB_DESTROY_BY_RCU)
 599                 rcu_barrier();
 600         slob_free(c, sizeof(struct kmem_cache));
 601 }
 602 EXPORT_SYMBOL(kmem_cache_destroy);
 603
 604 void *kmem_cache_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
 605 {
 606         void *b;
 607
 608         if (c->size < PAGE_SIZE) {
 609                 b = slob_alloc(c->size, flags, c->align, node);
 610                 trace_kmem_cache_alloc_node(_RET_IP_, b, c->size,
 611                                             SLOB_UNITS(c->size) * SLOB_UNIT,
 612                                             flags, node);
 613         } else {
 614                 b = slob_new_pages(flags, get_order(c->size), node);
 615                 trace_kmem_cache_alloc_node(_RET_IP_, b, c->size,
 616                                             PAGE_SIZE << get_order(c->size),
 617                                             flags, node);
 618         }
 619
 620         if (c->ctor)
 621                 c->ctor(b);
 622
 623         kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
 624         return b;
 625 }
 626 EXPORT_SYMBOL(kmem_cache_alloc_node);
 627
 628 static void __kmem_cache_free(void *b, int size)
 629 {
 630         if (size < PAGE_SIZE)
 631                 slob_free(b, size);
 632         else
 633                 slob_free_pages(b, get_order(size));
 634 }
 635
 636 static void kmem_rcu_free(struct rcu_head *head)
 637 {
 638         struct slob_rcu *slob_rcu = (struct slob_rcu *)head;
 639         void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu));
 640
 641         __kmem_cache_free(b, slob_rcu->size);
 642 }
 643
 644 void kmem_cache_free(struct kmem_cache *c, void *b)
 645 {
 646         kmemleak_free_recursive(b, c->flags);
 647         if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) {
 648                 struct slob_rcu *slob_rcu;
 649                 slob_rcu = b + (c->size - sizeof(struct slob_rcu));
 650                 INIT_RCU_HEAD(&slob_rcu->head);
 651                 slob_rcu->size = c->size;
 652                 call_rcu(&slob_rcu->head, kmem_rcu_free);
 653         } else {
 654                 __kmem_cache_free(b, c->size);
 655         }
 656
 657         trace_kmem_cache_free(_RET_IP_, b);
 658 }
 659 EXPORT_SYMBOL(kmem_cache_free);
 660
 661 unsigned int kmem_cache_size(struct kmem_cache *c)
 662 {
 663         return c->size;
 664 }
 665 EXPORT_SYMBOL(kmem_cache_size);
 666
 667 const char *kmem_cache_name(struct kmem_cache *c)
 668 {
 669         return c->name;
 670 }
 671 EXPORT_SYMBOL(kmem_cache_name);
 672
 673 int kmem_cache_shrink(struct kmem_cache *d)
 674 {
 675         return 0;
 676 }
 677 EXPORT_SYMBOL(kmem_cache_shrink);
 678
 679 int kmem_ptr_validate(struct kmem_cache *a, const void *b)
 680 {
 681         return 0;
 682 }
 683
 684 static unsigned int slob_ready __read_mostly;
 685
 686 int slab_is_available(void)
 687 {
 688         return slob_ready;
 689 }
 690
 691 void __init kmem_cache_init(void)
 692 {
 693         slob_ready = 1;
 694 }