slub.c 113 KB
Newer Older
Christoph Lameter's avatar
Christoph Lameter committed
1
2
3
4
5
6
7
/*
 * SLUB: A slab allocator that limits cache line use instead of queuing
 * objects in per cpu and per node lists.
 *
 * The allocator synchronizes using per slab locks and only
 * uses a centralized lock to manage a pool of partial slabs.
 *
Christoph Lameter's avatar
Christoph Lameter committed
8
 * (C) 2007 SGI, Christoph Lameter
Christoph Lameter's avatar
Christoph Lameter committed
9
10
11
 */

#include <linux/mm.h>
Nick Piggin's avatar
Nick Piggin committed
12
#include <linux/swap.h> /* struct reclaim_state */
Christoph Lameter's avatar
Christoph Lameter committed
13
14
15
16
17
#include <linux/module.h>
#include <linux/bit_spinlock.h>
#include <linux/interrupt.h>
#include <linux/bitops.h>
#include <linux/slab.h>
18
#include <linux/proc_fs.h>
Christoph Lameter's avatar
Christoph Lameter committed
19
#include <linux/seq_file.h>
20
#include <linux/kmemtrace.h>
Vegard Nossum's avatar
Vegard Nossum committed
21
#include <linux/kmemcheck.h>
Christoph Lameter's avatar
Christoph Lameter committed
22
23
24
25
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/mempolicy.h>
#include <linux/ctype.h>
26
#include <linux/debugobjects.h>
Christoph Lameter's avatar
Christoph Lameter committed
27
#include <linux/kallsyms.h>
28
#include <linux/memory.h>
Roman Zippel's avatar
Roman Zippel committed
29
#include <linux/math64.h>
Akinobu Mita's avatar
Akinobu Mita committed
30
#include <linux/fault-inject.h>
Christoph Lameter's avatar
Christoph Lameter committed
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76

/*
 * Lock order:
 *   1. slab_lock(page)
 *   2. slab->list_lock
 *
 *   The slab_lock protects operations on the object of a particular
 *   slab and its metadata in the page struct. If the slab lock
 *   has been taken then no allocations nor frees can be performed
 *   on the objects in the slab nor can the slab be added or removed
 *   from the partial or full lists since this would mean modifying
 *   the page_struct of the slab.
 *
 *   The list_lock protects the partial and full list on each node and
 *   the partial slab counter. If taken then no new slabs may be added or
 *   removed from the lists nor make the number of partial slabs be modified.
 *   (Note that the total number of slabs is an atomic value that may be
 *   modified without taking the list lock).
 *
 *   The list_lock is a centralized lock and thus we avoid taking it as
 *   much as possible. As long as SLUB does not have to handle partial
 *   slabs, operations can continue without any centralized lock. F.e.
 *   allocating a long series of objects that fill up slabs does not require
 *   the list lock.
 *
 *   The lock order is sometimes inverted when we are trying to get a slab
 *   off a list. We take the list_lock and then look for a page on the list
 *   to use. While we do that objects in the slabs may be freed. We can
 *   only operate on the slab if we have also taken the slab_lock. So we use
 *   a slab_trylock() on the slab. If trylock was successful then no frees
 *   can occur anymore and we can use the slab for allocations etc. If the
 *   slab_trylock() does not succeed then frees are in progress in the slab and
 *   we must stay away from it for a while since we may cause a bouncing
 *   cacheline if we try to acquire the lock. So go onto the next slab.
 *   If all pages are busy then we may allocate a new slab instead of reusing
 *   a partial slab. A new slab has noone operating on it and thus there is
 *   no danger of cacheline contention.
 *
 *   Interrupts are disabled during allocation and deallocation in order to
 *   make the slab allocator safe to use in the context of an irq. In addition
 *   interrupts are disabled to ensure that the processor does not change
 *   while handling per_cpu slabs, due to kernel preemption.
 *
 * SLUB assigns one slab for allocation to each processor.
 * Allocations only occur from these slabs called cpu slabs.
 *
Christoph Lameter's avatar
Christoph Lameter committed
77
78
 * Slabs with free elements are kept on a partial list and during regular
 * operations no list for full slabs is used. If an object in a full slab is
Christoph Lameter's avatar
Christoph Lameter committed
79
 * freed then the slab will show up again on the partial lists.
Christoph Lameter's avatar
Christoph Lameter committed
80
81
 * We track full slabs for debugging purposes though because otherwise we
 * cannot scan all objects.
Christoph Lameter's avatar
Christoph Lameter committed
82
83
84
85
86
87
88
 *
 * Slabs are freed when they become empty. Teardown and setup is
 * minimal so we rely on the page allocators per cpu caches for
 * fast frees and allocs.
 *
 * Overloading of page flags that are otherwise used for LRU management.
 *
89
90
91
92
93
94
95
96
97
98
99
100
 * PageActive 		The slab is frozen and exempt from list processing.
 * 			This means that the slab is dedicated to a purpose
 * 			such as satisfying allocations for a specific
 * 			processor. Objects may be freed in the slab while
 * 			it is frozen but slab_free will then skip the usual
 * 			list operations. It is up to the processor holding
 * 			the slab to integrate the slab into the slab lists
 * 			when the slab is no longer needed.
 *
 * 			One use of this flag is to mark slabs that are
 * 			used for allocations. Then such a slab becomes a cpu
 * 			slab. The cpu slab may be equipped with an additional
101
 * 			freelist that allows lockless access to
102
103
 * 			free objects in addition to the regular freelist
 * 			that requires the slab lock.
Christoph Lameter's avatar
Christoph Lameter committed
104
105
106
 *
 * PageError		Slab requires special handling due to debug
 * 			options set. This moves	slab handling out of
107
 * 			the fast path and disables lockless freelists.
Christoph Lameter's avatar
Christoph Lameter committed
108
109
 */

110
#ifdef CONFIG_SLUB_DEBUG
111
#define SLABDEBUG 1
112
113
114
115
#else
#define SLABDEBUG 0
#endif

Christoph Lameter's avatar
Christoph Lameter committed
116
117
118
119
120
121
122
123
124
125
126
/*
 * Issues still to be resolved:
 *
 * - Support PAGE_ALLOC_DEBUG. Should be easy to do.
 *
 * - Variable sizing of the per node arrays
 */

/* Enable to test recovery from slab corruption on boot */
#undef SLUB_RESILIENCY_TEST

127
128
129
130
/*
 * Mininum number of partial slabs. These will be left on the partial
 * lists even if they are empty. kmem_cache_shrink may reclaim them.
 */
131
#define MIN_PARTIAL 5
Christoph Lameter's avatar
Christoph Lameter committed
132

133
134
135
136
137
138
139
/*
 * Maximum number of desirable partial slabs.
 * The existence of more partial slabs makes kmem_cache_shrink
 * sort the partial list by the number of objects in the.
 */
#define MAX_PARTIAL 10

Christoph Lameter's avatar
Christoph Lameter committed
140
141
#define DEBUG_DEFAULT_FLAGS (SLAB_DEBUG_FREE | SLAB_RED_ZONE | \
				SLAB_POISON | SLAB_STORE_USER)
Christoph Lameter's avatar
Christoph Lameter committed
142

143
/*
144
145
146
 * Debugging flags that require metadata to be stored in the slab.  These get
 * disabled when slub_debug=O is used and a cache's min order increases with
 * metadata.
147
 */
148
#define DEBUG_METADATA_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)
149

Christoph Lameter's avatar
Christoph Lameter committed
150
151
152
153
/*
 * Set of flags that will prevent slab merging
 */
#define SLUB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
154
		SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE)
Christoph Lameter's avatar
Christoph Lameter committed
155
156

#define SLUB_MERGE_SAME (SLAB_DEBUG_FREE | SLAB_RECLAIM_ACCOUNT | \
Vegard Nossum's avatar
Vegard Nossum committed
157
		SLAB_CACHE_DMA | SLAB_NOTRACK)
Christoph Lameter's avatar
Christoph Lameter committed
158
159

#ifndef ARCH_KMALLOC_MINALIGN
160
#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
Christoph Lameter's avatar
Christoph Lameter committed
161
162
163
#endif

#ifndef ARCH_SLAB_MINALIGN
164
#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
Christoph Lameter's avatar
Christoph Lameter committed
165
166
#endif

167
168
169
170
#define OO_SHIFT	16
#define OO_MASK		((1 << OO_SHIFT) - 1)
#define MAX_OBJS_PER_PAGE	65535 /* since page.objects is u16 */

Christoph Lameter's avatar
Christoph Lameter committed
171
/* Internal SLUB flags */
172
173
#define __OBJECT_POISON		0x80000000 /* Poison object */
#define __SYSFS_ADD_DEFERRED	0x40000000 /* Not yet visible via sysfs */
Christoph Lameter's avatar
Christoph Lameter committed
174
175
176
177
178
179
180
181
182
183

static int kmem_size = sizeof(struct kmem_cache);

#ifdef CONFIG_SMP
static struct notifier_block slab_notifier;
#endif

static enum {
	DOWN,		/* No slab functionality available */
	PARTIAL,	/* kmem_cache_open() works but kmalloc does not */
Christoph Lameter's avatar
Christoph Lameter committed
184
	UP,		/* Everything works but does not show up in sysfs */
Christoph Lameter's avatar
Christoph Lameter committed
185
186
187
188
189
	SYSFS		/* Sysfs up */
} slab_state = DOWN;

/* A list of all slab caches on the system */
static DECLARE_RWSEM(slub_lock);
Adrian Bunk's avatar
Adrian Bunk committed
190
static LIST_HEAD(slab_caches);
Christoph Lameter's avatar
Christoph Lameter committed
191

192
193
194
195
/*
 * Tracking user of a slab.
 */
struct track {
196
	unsigned long addr;	/* Called from address */
197
198
199
200
201
202
203
	int cpu;		/* Was running on cpu */
	int pid;		/* Pid context */
	unsigned long when;	/* When did the operation occur */
};

enum track_item { TRACK_ALLOC, TRACK_FREE };

204
#ifdef CONFIG_SLUB_DEBUG
Christoph Lameter's avatar
Christoph Lameter committed
205
206
207
static int sysfs_slab_add(struct kmem_cache *);
static int sysfs_slab_alias(struct kmem_cache *, const char *);
static void sysfs_slab_remove(struct kmem_cache *);
208

Christoph Lameter's avatar
Christoph Lameter committed
209
#else
210
211
212
static inline int sysfs_slab_add(struct kmem_cache *s) { return 0; }
static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
							{ return 0; }
213
214
215
216
static inline void sysfs_slab_remove(struct kmem_cache *s)
{
	kfree(s);
}
217

Christoph Lameter's avatar
Christoph Lameter committed
218
219
#endif

220
221
222
223
224
225
226
static inline void stat(struct kmem_cache_cpu *c, enum stat_item si)
{
#ifdef CONFIG_SLUB_STATS
	c->stat[si]++;
#endif
}

Christoph Lameter's avatar
Christoph Lameter committed
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
/********************************************************************
 * 			Core slab cache functions
 *******************************************************************/

int slab_is_available(void)
{
	return slab_state >= UP;
}

static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
{
#ifdef CONFIG_NUMA
	return s->node[node];
#else
	return &s->local_node;
#endif
}

245
246
static inline struct kmem_cache_cpu *get_cpu_slab(struct kmem_cache *s, int cpu)
{
247
248
249
250
251
#ifdef CONFIG_SMP
	return s->cpu_slab[cpu];
#else
	return &s->cpu_slab;
#endif
252
253
}

Christoph Lameter's avatar
Christoph Lameter committed
254
/* Verify that a pointer has an address that is valid within a slab page */
255
256
257
258
259
static inline int check_valid_pointer(struct kmem_cache *s,
				struct page *page, const void *object)
{
	void *base;

260
	if (!object)
261
262
		return 1;

263
	base = page_address(page);
264
	if (object < base || object >= base + page->objects * s->size ||
265
266
267
268
269
270
271
		(object - base) % s->size) {
		return 0;
	}

	return 1;
}

272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
/*
 * Slow version of get and set free pointer.
 *
 * This version requires touching the cache lines of kmem_cache which
 * we avoid to do in the fast alloc free paths. There we obtain the offset
 * from the page struct.
 */
static inline void *get_freepointer(struct kmem_cache *s, void *object)
{
	return *(void **)(object + s->offset);
}

static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
{
	*(void **)(object + s->offset) = fp;
}

/* Loop over all objects in a slab */
290
291
#define for_each_object(__p, __s, __addr, __objects) \
	for (__p = (__addr); __p < (__addr) + (__objects) * (__s)->size;\
292
293
294
295
			__p += (__s)->size)

/* Scan freelist */
#define for_each_free_object(__p, __s, __free) \
296
	for (__p = (__free); __p; __p = get_freepointer((__s), __p))
297
298
299
300
301
302
303

/* Determine object index from a given position */
static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
{
	return (p - addr) / s->size;
}

304
305
306
307
static inline struct kmem_cache_order_objects oo_make(int order,
						unsigned long size)
{
	struct kmem_cache_order_objects x = {
308
		(order << OO_SHIFT) + (PAGE_SIZE << order) / size
309
310
311
312
313
314
315
	};

	return x;
}

static inline int oo_order(struct kmem_cache_order_objects x)
{
316
	return x.x >> OO_SHIFT;
317
318
319
320
}

static inline int oo_objects(struct kmem_cache_order_objects x)
{
321
	return x.x & OO_MASK;
322
323
}

324
325
326
327
#ifdef CONFIG_SLUB_DEBUG
/*
 * Debug settings:
 */
328
329
330
#ifdef CONFIG_SLUB_DEBUG_ON
static int slub_debug = DEBUG_DEFAULT_FLAGS;
#else
331
static int slub_debug;
332
#endif
333
334

static char *slub_debug_slabs;
335
static int disable_higher_order_debug;
336

Christoph Lameter's avatar
Christoph Lameter committed
337
338
339
340
341
342
343
344
345
346
347
348
349
/*
 * Object debugging
 */
static void print_section(char *text, u8 *addr, unsigned int length)
{
	int i, offset;
	int newline = 1;
	char ascii[17];

	ascii[16] = 0;

	for (i = 0; i < length; i++) {
		if (newline) {
350
			printk(KERN_ERR "%8s 0x%p: ", text, addr + i);
Christoph Lameter's avatar
Christoph Lameter committed
351
352
			newline = 0;
		}
353
		printk(KERN_CONT " %02x", addr[i]);
Christoph Lameter's avatar
Christoph Lameter committed
354
355
356
		offset = i % 16;
		ascii[offset] = isgraph(addr[i]) ? addr[i] : '.';
		if (offset == 15) {
357
			printk(KERN_CONT " %s\n", ascii);
Christoph Lameter's avatar
Christoph Lameter committed
358
359
360
361
362
363
			newline = 1;
		}
	}
	if (!newline) {
		i %= 16;
		while (i < 16) {
364
			printk(KERN_CONT "   ");
Christoph Lameter's avatar
Christoph Lameter committed
365
366
367
			ascii[i] = ' ';
			i++;
		}
368
		printk(KERN_CONT " %s\n", ascii);
Christoph Lameter's avatar
Christoph Lameter committed
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
	}
}

static struct track *get_track(struct kmem_cache *s, void *object,
	enum track_item alloc)
{
	struct track *p;

	if (s->offset)
		p = object + s->offset + sizeof(void *);
	else
		p = object + s->inuse;

	return p + alloc;
}

static void set_track(struct kmem_cache *s, void *object,
386
			enum track_item alloc, unsigned long addr)
Christoph Lameter's avatar
Christoph Lameter committed
387
{
Akinobu Mita's avatar
Akinobu Mita committed
388
	struct track *p = get_track(s, object, alloc);
Christoph Lameter's avatar
Christoph Lameter committed
389
390
391
392

	if (addr) {
		p->addr = addr;
		p->cpu = smp_processor_id();
393
		p->pid = current->pid;
Christoph Lameter's avatar
Christoph Lameter committed
394
395
396
397
398
399
400
		p->when = jiffies;
	} else
		memset(p, 0, sizeof(struct track));
}

static void init_tracking(struct kmem_cache *s, void *object)
{
401
402
403
	if (!(s->flags & SLAB_STORE_USER))
		return;

404
405
	set_track(s, object, TRACK_FREE, 0UL);
	set_track(s, object, TRACK_ALLOC, 0UL);
Christoph Lameter's avatar
Christoph Lameter committed
406
407
408
409
410
411
412
}

static void print_track(const char *s, struct track *t)
{
	if (!t->addr)
		return;

413
	printk(KERN_ERR "INFO: %s in %pS age=%lu cpu=%u pid=%d\n",
414
		s, (void *)t->addr, jiffies - t->when, t->cpu, t->pid);
415
416
417
418
419
420
421
422
423
424
425
426
427
}

static void print_tracking(struct kmem_cache *s, void *object)
{
	if (!(s->flags & SLAB_STORE_USER))
		return;

	print_track("Allocated", get_track(s, object, TRACK_ALLOC));
	print_track("Freed", get_track(s, object, TRACK_FREE));
}

static void print_page_info(struct page *page)
{
428
429
	printk(KERN_ERR "INFO: Slab 0x%p objects=%u used=%u fp=0x%p flags=0x%04lx\n",
		page, page->objects, page->inuse, page->freelist, page->flags);
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445

}

static void slab_bug(struct kmem_cache *s, char *fmt, ...)
{
	va_list args;
	char buf[100];

	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
	va_end(args);
	printk(KERN_ERR "========================================"
			"=====================================\n");
	printk(KERN_ERR "BUG %s: %s\n", s->name, buf);
	printk(KERN_ERR "----------------------------------------"
			"-------------------------------------\n\n");
Christoph Lameter's avatar
Christoph Lameter committed
446
447
}

448
449
450
451
452
453
454
455
456
457
458
459
static void slab_fix(struct kmem_cache *s, char *fmt, ...)
{
	va_list args;
	char buf[100];

	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
	va_end(args);
	printk(KERN_ERR "FIX %s: %s\n", s->name, buf);
}

static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
Christoph Lameter's avatar
Christoph Lameter committed
460
461
{
	unsigned int off;	/* Offset of last byte */
462
	u8 *addr = page_address(page);
463
464
465
466
467
468
469
470
471
472
473

	print_tracking(s, p);

	print_page_info(page);

	printk(KERN_ERR "INFO: Object 0x%p @offset=%tu fp=0x%p\n\n",
			p, p - addr, get_freepointer(s, p));

	if (p > addr + 16)
		print_section("Bytes b4", p - 16, 16);

474
	print_section("Object", p, min_t(unsigned long, s->objsize, PAGE_SIZE));
Christoph Lameter's avatar
Christoph Lameter committed
475
476
477
478
479
480
481
482
483
484

	if (s->flags & SLAB_RED_ZONE)
		print_section("Redzone", p + s->objsize,
			s->inuse - s->objsize);

	if (s->offset)
		off = s->offset + sizeof(void *);
	else
		off = s->inuse;

485
	if (s->flags & SLAB_STORE_USER)
Christoph Lameter's avatar
Christoph Lameter committed
486
487
488
489
		off += 2 * sizeof(struct track);

	if (off != s->size)
		/* Beginning of the filler is the free pointer */
490
491
492
		print_section("Padding", p + off, s->size - off);

	dump_stack();
Christoph Lameter's avatar
Christoph Lameter committed
493
494
495
496
497
}

static void object_err(struct kmem_cache *s, struct page *page,
			u8 *object, char *reason)
{
498
	slab_bug(s, "%s", reason);
499
	print_trailer(s, page, object);
Christoph Lameter's avatar
Christoph Lameter committed
500
501
}

502
static void slab_err(struct kmem_cache *s, struct page *page, char *fmt, ...)
Christoph Lameter's avatar
Christoph Lameter committed
503
504
505
506
{
	va_list args;
	char buf[100];

507
508
	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
Christoph Lameter's avatar
Christoph Lameter committed
509
	va_end(args);
510
	slab_bug(s, "%s", buf);
511
	print_page_info(page);
Christoph Lameter's avatar
Christoph Lameter committed
512
513
514
515
516
517
518
519
520
	dump_stack();
}

static void init_object(struct kmem_cache *s, void *object, int active)
{
	u8 *p = object;

	if (s->flags & __OBJECT_POISON) {
		memset(p, POISON_FREE, s->objsize - 1);
521
		p[s->objsize - 1] = POISON_END;
Christoph Lameter's avatar
Christoph Lameter committed
522
523
524
525
526
527
528
529
	}

	if (s->flags & SLAB_RED_ZONE)
		memset(p + s->objsize,
			active ? SLUB_RED_ACTIVE : SLUB_RED_INACTIVE,
			s->inuse - s->objsize);
}

530
static u8 *check_bytes(u8 *start, unsigned int value, unsigned int bytes)
Christoph Lameter's avatar
Christoph Lameter committed
531
532
533
{
	while (bytes) {
		if (*start != (u8)value)
534
			return start;
Christoph Lameter's avatar
Christoph Lameter committed
535
536
537
		start++;
		bytes--;
	}
538
539
540
541
542
543
544
545
546
547
548
549
	return NULL;
}

static void restore_bytes(struct kmem_cache *s, char *message, u8 data,
						void *from, void *to)
{
	slab_fix(s, "Restoring 0x%p-0x%p=0x%x\n", from, to - 1, data);
	memset(from, data, to - from);
}

static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
			u8 *object, char *what,
550
			u8 *start, unsigned int value, unsigned int bytes)
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
{
	u8 *fault;
	u8 *end;

	fault = check_bytes(start, value, bytes);
	if (!fault)
		return 1;

	end = start + bytes;
	while (end > fault && end[-1] == value)
		end--;

	slab_bug(s, "%s overwritten", what);
	printk(KERN_ERR "INFO: 0x%p-0x%p. First byte 0x%x instead of 0x%x\n",
					fault, end - 1, fault[0], value);
	print_trailer(s, page, object);

	restore_bytes(s, what, value, fault, end);
	return 0;
Christoph Lameter's avatar
Christoph Lameter committed
570
571
572
573
574
575
576
577
578
}

/*
 * Object layout:
 *
 * object address
 * 	Bytes of the object to be managed.
 * 	If the freepointer may overlay the object then the free
 * 	pointer is the first word of the object.
Christoph Lameter's avatar
Christoph Lameter committed
579
 *
Christoph Lameter's avatar
Christoph Lameter committed
580
581
582
583
584
 * 	Poisoning uses 0x6b (POISON_FREE) and the last byte is
 * 	0xa5 (POISON_END)
 *
 * object + s->objsize
 * 	Padding to reach word boundary. This is also used for Redzoning.
Christoph Lameter's avatar
Christoph Lameter committed
585
586
587
 * 	Padding is extended by another word if Redzoning is enabled and
 * 	objsize == inuse.
 *
Christoph Lameter's avatar
Christoph Lameter committed
588
589
590
591
 * 	We fill with 0xbb (RED_INACTIVE) for inactive objects and with
 * 	0xcc (RED_ACTIVE) for objects in use.
 *
 * object + s->inuse
Christoph Lameter's avatar
Christoph Lameter committed
592
593
 * 	Meta data starts here.
 *
Christoph Lameter's avatar
Christoph Lameter committed
594
595
 * 	A. Free pointer (if we cannot overwrite object on free)
 * 	B. Tracking data for SLAB_STORE_USER
Christoph Lameter's avatar
Christoph Lameter committed
596
 * 	C. Padding to reach required alignment boundary or at mininum
Christoph Lameter's avatar
Christoph Lameter committed
597
 * 		one word if debugging is on to be able to detect writes
Christoph Lameter's avatar
Christoph Lameter committed
598
599
600
 * 		before the word boundary.
 *
 *	Padding is done using 0x5a (POISON_INUSE)
Christoph Lameter's avatar
Christoph Lameter committed
601
602
 *
 * object + s->size
Christoph Lameter's avatar
Christoph Lameter committed
603
 * 	Nothing is used beyond s->size.
Christoph Lameter's avatar
Christoph Lameter committed
604
 *
Christoph Lameter's avatar
Christoph Lameter committed
605
606
 * If slabcaches are merged then the objsize and inuse boundaries are mostly
 * ignored. And therefore no slab options that rely on these boundaries
Christoph Lameter's avatar
Christoph Lameter committed
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
 * may be used with merged slabcaches.
 */

static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p)
{
	unsigned long off = s->inuse;	/* The end of info */

	if (s->offset)
		/* Freepointer is placed after the object. */
		off += sizeof(void *);

	if (s->flags & SLAB_STORE_USER)
		/* We also have user information there */
		off += 2 * sizeof(struct track);

	if (s->size == off)
		return 1;

625
626
	return check_bytes_and_report(s, page, p, "Object padding",
				p + off, POISON_INUSE, s->size - off);
Christoph Lameter's avatar
Christoph Lameter committed
627
628
}

629
/* Check the pad bytes at the end of a slab page */
Christoph Lameter's avatar
Christoph Lameter committed
630
631
static int slab_pad_check(struct kmem_cache *s, struct page *page)
{
632
633
634
635
636
	u8 *start;
	u8 *fault;
	u8 *end;
	int length;
	int remainder;
Christoph Lameter's avatar
Christoph Lameter committed
637
638
639
640

	if (!(s->flags & SLAB_POISON))
		return 1;

641
	start = page_address(page);
642
	length = (PAGE_SIZE << compound_order(page));
643
644
	end = start + length;
	remainder = length % s->size;
Christoph Lameter's avatar
Christoph Lameter committed
645
646
647
	if (!remainder)
		return 1;

648
	fault = check_bytes(end - remainder, POISON_INUSE, remainder);
649
650
651
652
653
654
	if (!fault)
		return 1;
	while (end > fault && end[-1] == POISON_INUSE)
		end--;

	slab_err(s, page, "Padding overwritten. 0x%p-0x%p", fault, end - 1);
655
	print_section("Padding", end - remainder, remainder);
656

Eric Dumazet's avatar
Eric Dumazet committed
657
	restore_bytes(s, "slab padding", POISON_INUSE, end - remainder, end);
658
	return 0;
Christoph Lameter's avatar
Christoph Lameter committed
659
660
661
662
663
664
665
666
667
668
669
670
}

static int check_object(struct kmem_cache *s, struct page *page,
					void *object, int active)
{
	u8 *p = object;
	u8 *endobject = object + s->objsize;

	if (s->flags & SLAB_RED_ZONE) {
		unsigned int red =
			active ? SLUB_RED_ACTIVE : SLUB_RED_INACTIVE;

671
672
		if (!check_bytes_and_report(s, page, object, "Redzone",
			endobject, red, s->inuse - s->objsize))
Christoph Lameter's avatar
Christoph Lameter committed
673
674
			return 0;
	} else {
Ingo Molnar's avatar
Ingo Molnar committed
675
676
677
678
		if ((s->flags & SLAB_POISON) && s->objsize < s->inuse) {
			check_bytes_and_report(s, page, p, "Alignment padding",
				endobject, POISON_INUSE, s->inuse - s->objsize);
		}
Christoph Lameter's avatar
Christoph Lameter committed
679
680
681
682
	}

	if (s->flags & SLAB_POISON) {
		if (!active && (s->flags & __OBJECT_POISON) &&
683
684
685
			(!check_bytes_and_report(s, page, p, "Poison", p,
					POISON_FREE, s->objsize - 1) ||
			 !check_bytes_and_report(s, page, p, "Poison",
686
				p + s->objsize - 1, POISON_END, 1)))
Christoph Lameter's avatar
Christoph Lameter committed
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
			return 0;
		/*
		 * check_pad_bytes cleans up on its own.
		 */
		check_pad_bytes(s, page, p);
	}

	if (!s->offset && active)
		/*
		 * Object and freepointer overlap. Cannot check
		 * freepointer while object is allocated.
		 */
		return 1;

	/* Check free pointer validity */
	if (!check_valid_pointer(s, page, get_freepointer(s, p))) {
		object_err(s, page, p, "Freepointer corrupt");
		/*
Nick Andrew's avatar
Nick Andrew committed
705
		 * No choice but to zap it and thus lose the remainder
Christoph Lameter's avatar
Christoph Lameter committed
706
		 * of the free objects in this slab. May cause
Christoph Lameter's avatar
Christoph Lameter committed
707
		 * another error because the object count is now wrong.
Christoph Lameter's avatar
Christoph Lameter committed
708
		 */
709
		set_freepointer(s, p, NULL);
Christoph Lameter's avatar
Christoph Lameter committed
710
711
712
713
714
715
716
		return 0;
	}
	return 1;
}

static int check_slab(struct kmem_cache *s, struct page *page)
{
717
718
	int maxobj;

Christoph Lameter's avatar
Christoph Lameter committed
719
720
721
	VM_BUG_ON(!irqs_disabled());

	if (!PageSlab(page)) {
722
		slab_err(s, page, "Not a valid slab page");
Christoph Lameter's avatar
Christoph Lameter committed
723
724
		return 0;
	}
725
726
727
728
729
730
731
732

	maxobj = (PAGE_SIZE << compound_order(page)) / s->size;
	if (page->objects > maxobj) {
		slab_err(s, page, "objects %u > max %u",
			s->name, page->objects, maxobj);
		return 0;
	}
	if (page->inuse > page->objects) {
733
		slab_err(s, page, "inuse %u > max %u",
734
			s->name, page->inuse, page->objects);
Christoph Lameter's avatar
Christoph Lameter committed
735
736
737
738
739
740
741
742
		return 0;
	}
	/* Slab_pad_check fixes things up after itself */
	slab_pad_check(s, page);
	return 1;
}

/*
Christoph Lameter's avatar
Christoph Lameter committed
743
744
 * Determine if a certain object on a page is on the freelist. Must hold the
 * slab lock to guarantee that the chains are in a consistent state.
Christoph Lameter's avatar
Christoph Lameter committed
745
746
747
748
749
750
 */
static int on_freelist(struct kmem_cache *s, struct page *page, void *search)
{
	int nr = 0;
	void *fp = page->freelist;
	void *object = NULL;
751
	unsigned long max_objects;
Christoph Lameter's avatar
Christoph Lameter committed
752

753
	while (fp && nr <= page->objects) {
Christoph Lameter's avatar
Christoph Lameter committed
754
755
756
757
758
759
		if (fp == search)
			return 1;
		if (!check_valid_pointer(s, page, fp)) {
			if (object) {
				object_err(s, page, object,
					"Freechain corrupt");
760
				set_freepointer(s, object, NULL);
Christoph Lameter's avatar
Christoph Lameter committed
761
762
				break;
			} else {
763
				slab_err(s, page, "Freepointer corrupt");
764
				page->freelist = NULL;
765
				page->inuse = page->objects;
766
				slab_fix(s, "Freelist cleared");
Christoph Lameter's avatar
Christoph Lameter committed
767
768
769
770
771
772
773
774
775
				return 0;
			}
			break;
		}
		object = fp;
		fp = get_freepointer(s, object);
		nr++;
	}

776
	max_objects = (PAGE_SIZE << compound_order(page)) / s->size;
777
778
	if (max_objects > MAX_OBJS_PER_PAGE)
		max_objects = MAX_OBJS_PER_PAGE;
779
780
781
782
783
784
785

	if (page->objects != max_objects) {
		slab_err(s, page, "Wrong number of objects. Found %d but "
			"should be %d", page->objects, max_objects);
		page->objects = max_objects;
		slab_fix(s, "Number of objects adjusted.");
	}
786
	if (page->inuse != page->objects - nr) {
787
		slab_err(s, page, "Wrong object count. Counter is %d but "
788
789
			"counted were %d", page->inuse, page->objects - nr);
		page->inuse = page->objects - nr;
790
		slab_fix(s, "Object count adjusted.");
Christoph Lameter's avatar
Christoph Lameter committed
791
792
793
794
	}
	return search == NULL;
}

795
796
static void trace(struct kmem_cache *s, struct page *page, void *object,
								int alloc)
Christoph Lameter's avatar
Christoph Lameter committed
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
{
	if (s->flags & SLAB_TRACE) {
		printk(KERN_INFO "TRACE %s %s 0x%p inuse=%d fp=0x%p\n",
			s->name,
			alloc ? "alloc" : "free",
			object, page->inuse,
			page->freelist);

		if (!alloc)
			print_section("Object", (void *)object, s->objsize);

		dump_stack();
	}
}

812
/*
Christoph Lameter's avatar
Christoph Lameter committed
813
 * Tracking of fully allocated slabs for debugging purposes.
814
 */
Christoph Lameter's avatar
Christoph Lameter committed
815
static void add_full(struct kmem_cache_node *n, struct page *page)
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
{
	spin_lock(&n->list_lock);
	list_add(&page->lru, &n->full);
	spin_unlock(&n->list_lock);
}

static void remove_full(struct kmem_cache *s, struct page *page)
{
	struct kmem_cache_node *n;

	if (!(s->flags & SLAB_STORE_USER))
		return;

	n = get_node(s, page_to_nid(page));

	spin_lock(&n->list_lock);
	list_del(&page->lru);
	spin_unlock(&n->list_lock);
}

836
837
838
839
840
841
842
843
/* Tracking of the number of slabs for debugging purposes */
static inline unsigned long slabs_node(struct kmem_cache *s, int node)
{
	struct kmem_cache_node *n = get_node(s, node);

	return atomic_long_read(&n->nr_slabs);
}

844
845
846
847
848
static inline unsigned long node_nr_slabs(struct kmem_cache_node *n)
{
	return atomic_long_read(&n->nr_slabs);
}

849
static inline void inc_slabs_node(struct kmem_cache *s, int node, int objects)
850
851
852
853
854
855
856
857
858
{
	struct kmem_cache_node *n = get_node(s, node);

	/*
	 * May be called early in order to allocate a slab for the
	 * kmem_cache_node structure. Solve the chicken-egg
	 * dilemma by deferring the increment of the count during
	 * bootstrap (see early_kmem_cache_node_alloc).
	 */
859
	if (!NUMA_BUILD || n) {
860
		atomic_long_inc(&n->nr_slabs);
861
862
		atomic_long_add(objects, &n->total_objects);
	}
863
}
864
static inline void dec_slabs_node(struct kmem_cache *s, int node, int objects)
865
866
867
868
{
	struct kmem_cache_node *n = get_node(s, node);

	atomic_long_dec(&n->nr_slabs);
869
	atomic_long_sub(objects, &n->total_objects);
870
871
872
}

/* Object debug checks for alloc/free paths */
Christoph Lameter's avatar
Christoph Lameter committed
873
874
875
876
877
878
879
880
881
882
883
static void setup_object_debug(struct kmem_cache *s, struct page *page,
								void *object)
{
	if (!(s->flags & (SLAB_STORE_USER|SLAB_RED_ZONE|__OBJECT_POISON)))
		return;

	init_object(s, object, 0);
	init_tracking(s, object);
}

static int alloc_debug_processing(struct kmem_cache *s, struct page *page,
884
					void *object, unsigned long addr)
Christoph Lameter's avatar
Christoph Lameter committed
885
886
887
888
{
	if (!check_slab(s, page))
		goto bad;

889
	if (!on_freelist(s, page, object)) {
890
		object_err(s, page, object, "Object already allocated");
891
		goto bad;
Christoph Lameter's avatar
Christoph Lameter committed
892
893
894
895
	}

	if (!check_valid_pointer(s, page, object)) {
		object_err(s, page, object, "Freelist Pointer check fails");
896
		goto bad;
Christoph Lameter's avatar
Christoph Lameter committed
897
898
	}

899
	if (!check_object(s, page, object, 0))
Christoph Lameter's avatar
Christoph Lameter committed
900
901
		goto bad;

Christoph Lameter's avatar
Christoph Lameter committed
902
903
904
905
906
	/* Success perform special debug activities for allocs */
	if (s->flags & SLAB_STORE_USER)
		set_track(s, object, TRACK_ALLOC, addr);
	trace(s, page, object, 1);
	init_object(s, object, 1);
Christoph Lameter's avatar
Christoph Lameter committed
907
	return 1;
Christoph Lameter's avatar
Christoph Lameter committed
908

Christoph Lameter's avatar
Christoph Lameter committed
909
910
911
912
913
bad:
	if (PageSlab(page)) {
		/*
		 * If this is a slab page then lets do the best we can
		 * to avoid issues in the future. Marking all objects
Christoph Lameter's avatar
Christoph Lameter committed
914
		 * as used avoids touching the remaining objects.
Christoph Lameter's avatar
Christoph Lameter committed
915
		 */
916
		slab_fix(s, "Marking all objects used");
917
		page->inuse = page->objects;
918
		page->freelist = NULL;
Christoph Lameter's avatar
Christoph Lameter committed
919
920
921
922
	}
	return 0;
}

Christoph Lameter's avatar
Christoph Lameter committed
923
static int free_debug_processing(struct kmem_cache *s, struct page *page,
924
					void *object, unsigned long addr)
Christoph Lameter's avatar
Christoph Lameter committed
925
926
927
928
929
{
	if (!check_slab(s, page))
		goto fail;

	if (!check_valid_pointer(s, page, object)) {
930
		slab_err(s, page, "Invalid object pointer 0x%p", object);
Christoph Lameter's avatar
Christoph Lameter committed
931
932
933
934
		goto fail;
	}

	if (on_freelist(s, page, object)) {
935
		object_err(s, page, object, "Object already free");
Christoph Lameter's avatar
Christoph Lameter committed
936
937
938
939
940
941
942
		goto fail;
	}

	if (!check_object(s, page, object, 1))
		return 0;

	if (unlikely(s != page->slab)) {
Ingo Molnar's avatar
Ingo Molnar committed
943
		if (!PageSlab(page)) {
944
945
			slab_err(s, page, "Attempt to free object(0x%p) "
				"outside of slab", object);
Ingo Molnar's avatar
Ingo Molnar committed
946
		} else if (!page->slab) {
Christoph Lameter's avatar
Christoph Lameter committed
947
			printk(KERN_ERR
948
				"SLUB <none>: no slab for object 0x%p.\n",
Christoph Lameter's avatar
Christoph Lameter committed
949
						object);
950
			dump_stack();
951
		} else
952
953
			object_err(s, page, object,
					"page slab pointer corrupt.");
Christoph Lameter's avatar
Christoph Lameter committed
954
955
		goto fail;
	}
Christoph Lameter's avatar
Christoph Lameter committed
956
957

	/* Special debug activities for freeing objects */
958
	if (!PageSlubFrozen(page) && !page->freelist)
Christoph Lameter's avatar
Christoph Lameter committed
959
960
961
962
963
		remove_full(s, page);
	if (s->flags & SLAB_STORE_USER)
		set_track(s, object, TRACK_FREE, addr);
	trace(s, page, object, 0);
	init_object(s, object, 0);
Christoph Lameter's avatar
Christoph Lameter committed
964
	return 1;
Christoph Lameter's avatar
Christoph Lameter committed
965

Christoph Lameter's avatar
Christoph Lameter committed
966
fail:
967
	slab_fix(s, "Object at 0x%p not freed", object);
Christoph Lameter's avatar
Christoph Lameter committed
968
969
970
	return 0;
}

971
972
static int __init setup_slub_debug(char *str)
{
973
974
975
976
977
978
979
980
981
982
983
984
985
986
	slub_debug = DEBUG_DEFAULT_FLAGS;
	if (*str++ != '=' || !*str)
		/*
		 * No options specified. Switch on full debugging.
		 */
		goto out;

	if (*str == ',')
		/*
		 * No options but restriction on slabs. This means full
		 * debugging for slabs matching a pattern.
		 */
		goto check_slabs;

987
988
989
990
991
992
993
994
995
	if (tolower(*str) == 'o') {
		/*
		 * Avoid enabling debugging on caches if its minimum order
		 * would increase as a result.
		 */
		disable_higher_order_debug = 1;
		goto out;
	}

996
997
998
999
1000
	slub_debug = 0;
	if (*str == '-')
		/*
		 * Switch off all debugging measures.
		 */