slub.c 129 KB
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/*
 * SLUB: A slab allocator that limits cache line use instead of queuing
 * objects in per cpu and per node lists.
 *
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 * The allocator synchronizes using per slab locks or atomic operatios
 * and only uses a centralized lock to manage a pool of partial slabs.
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 *
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 * (C) 2007 SGI, Christoph Lameter
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 * (C) 2011 Linux Foundation, Christoph Lameter
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 */

#include <linux/mm.h>
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#include <linux/swap.h> /* struct reclaim_state */
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#include <linux/module.h>
#include <linux/bit_spinlock.h>
#include <linux/interrupt.h>
#include <linux/bitops.h>
#include <linux/slab.h>
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#include <linux/proc_fs.h>
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#include <linux/seq_file.h>
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#include <linux/kmemcheck.h>
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#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/mempolicy.h>
#include <linux/ctype.h>
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#include <linux/debugobjects.h>
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#include <linux/kallsyms.h>
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#include <linux/memory.h>
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#include <linux/math64.h>
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#include <linux/fault-inject.h>
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#include <linux/stacktrace.h>
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#include <trace/events/kmem.h>

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/*
 * Lock order:
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 *   1. slub_lock (Global Semaphore)
 *   2. node->list_lock
 *   3. slab_lock(page) (Only on some arches and for debugging)
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 *
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 *   slub_lock
 *
 *   The role of the slub_lock is to protect the list of all the slabs
 *   and to synchronize major metadata changes to slab cache structures.
 *
 *   The slab_lock is only used for debugging and on arches that do not
 *   have the ability to do a cmpxchg_double. It only protects the second
 *   double word in the page struct. Meaning
 *	A. page->freelist	-> List of object free in a page
 *	B. page->counters	-> Counters of objects
 *	C. page->frozen		-> frozen state
 *
 *   If a slab is frozen then it is exempt from list management. It is not
 *   on any list. The processor that froze the slab is the one who can
 *   perform list operations on the page. Other processors may put objects
 *   onto the freelist but the processor that froze the slab is the only
 *   one that can retrieve the objects from the page's freelist.
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 *
 *   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.
 *   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.
 *
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 * 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
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 * freed then the slab will show up again on the partial lists.
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 * We track full slabs for debugging purposes though because otherwise we
 * cannot scan all objects.
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 *
 * 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.
 *
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 * 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
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 * 			freelist that allows lockless access to
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 * 			free objects in addition to the regular freelist
 * 			that requires the slab lock.
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 *
 * PageError		Slab requires special handling due to debug
 * 			options set. This moves	slab handling out of
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 * 			the fast path and disables lockless freelists.
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 */

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#define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
		SLAB_TRACE | SLAB_DEBUG_FREE)

static inline int kmem_cache_debug(struct kmem_cache *s)
{
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#ifdef CONFIG_SLUB_DEBUG
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	return unlikely(s->flags & SLAB_DEBUG_FLAGS);
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#else
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	return 0;
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#endif
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}
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/*
 * 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

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/* Enable to log cmpxchg failures */
#undef SLUB_DEBUG_CMPXCHG

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/*
 * Mininum number of partial slabs. These will be left on the partial
 * lists even if they are empty. kmem_cache_shrink may reclaim them.
 */
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#define MIN_PARTIAL 5
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/*
 * 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

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#define DEBUG_DEFAULT_FLAGS (SLAB_DEBUG_FREE | SLAB_RED_ZONE | \
				SLAB_POISON | SLAB_STORE_USER)
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/*
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 * 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.
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 */
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#define DEBUG_METADATA_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)
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/*
 * Set of flags that will prevent slab merging
 */
#define SLUB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
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		SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE | \
		SLAB_FAILSLAB)
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#define SLUB_MERGE_SAME (SLAB_DEBUG_FREE | SLAB_RECLAIM_ACCOUNT | \
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		SLAB_CACHE_DMA | SLAB_NOTRACK)
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#define OO_SHIFT	16
#define OO_MASK		((1 << OO_SHIFT) - 1)
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#define MAX_OBJS_PER_PAGE	32767 /* since page.objects is u15 */
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/* Internal SLUB flags */
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#define __OBJECT_POISON		0x80000000UL /* Poison object */
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#define __CMPXCHG_DOUBLE	0x40000000UL /* Use cmpxchg_double */
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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 */
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	PARTIAL,	/* Kmem_cache_node works */
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	UP,		/* Everything works but does not show up in sysfs */
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	SYSFS		/* Sysfs up */
} slab_state = DOWN;

/* A list of all slab caches on the system */
static DECLARE_RWSEM(slub_lock);
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static LIST_HEAD(slab_caches);
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/*
 * Tracking user of a slab.
 */
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#define TRACK_ADDRS_COUNT 16
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struct track {
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	unsigned long addr;	/* Called from address */
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#ifdef CONFIG_STACKTRACE
	unsigned long addrs[TRACK_ADDRS_COUNT];	/* Called from address */
#endif
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	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 };

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#ifdef CONFIG_SYSFS
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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 *);
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#else
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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; }
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static inline void sysfs_slab_remove(struct kmem_cache *s)
{
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	kfree(s->name);
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	kfree(s);
}
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#endif

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static inline void stat(const struct kmem_cache *s, enum stat_item si)
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{
#ifdef CONFIG_SLUB_STATS
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	__this_cpu_inc(s->cpu_slab->stat[si]);
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#endif
}

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/********************************************************************
 * 			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)
{
	return s->node[node];
}

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/* Verify that a pointer has an address that is valid within a slab page */
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static inline int check_valid_pointer(struct kmem_cache *s,
				struct page *page, const void *object)
{
	void *base;

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	if (!object)
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		return 1;

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	base = page_address(page);
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	if (object < base || object >= base + page->objects * s->size ||
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		(object - base) % s->size) {
		return 0;
	}

	return 1;
}

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static inline void *get_freepointer(struct kmem_cache *s, void *object)
{
	return *(void **)(object + s->offset);
}

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static void prefetch_freepointer(const struct kmem_cache *s, void *object)
{
	prefetch(object + s->offset);
}

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static inline void *get_freepointer_safe(struct kmem_cache *s, void *object)
{
	void *p;

#ifdef CONFIG_DEBUG_PAGEALLOC
	probe_kernel_read(&p, (void **)(object + s->offset), sizeof(p));
#else
	p = get_freepointer(s, object);
#endif
	return p;
}

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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 */
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#define for_each_object(__p, __s, __addr, __objects) \
	for (__p = (__addr); __p < (__addr) + (__objects) * (__s)->size;\
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			__p += (__s)->size)

/* 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;
}

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static inline size_t slab_ksize(const struct kmem_cache *s)
{
#ifdef CONFIG_SLUB_DEBUG
	/*
	 * Debugging requires use of the padding between object
	 * and whatever may come after it.
	 */
	if (s->flags & (SLAB_RED_ZONE | SLAB_POISON))
		return s->objsize;

#endif
	/*
	 * If we have the need to store the freelist pointer
	 * back there or track user information then we can
	 * only use the space before that information.
	 */
	if (s->flags & (SLAB_DESTROY_BY_RCU | SLAB_STORE_USER))
		return s->inuse;
	/*
	 * Else we can use all the padding etc for the allocation
	 */
	return s->size;
}

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static inline int order_objects(int order, unsigned long size, int reserved)
{
	return ((PAGE_SIZE << order) - reserved) / size;
}

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static inline struct kmem_cache_order_objects oo_make(int order,
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		unsigned long size, int reserved)
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{
	struct kmem_cache_order_objects x = {
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		(order << OO_SHIFT) + order_objects(order, size, reserved)
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	};

	return x;
}

static inline int oo_order(struct kmem_cache_order_objects x)
{
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	return x.x >> OO_SHIFT;
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}

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

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/*
 * Per slab locking using the pagelock
 */
static __always_inline void slab_lock(struct page *page)
{
	bit_spin_lock(PG_locked, &page->flags);
}

static __always_inline void slab_unlock(struct page *page)
{
	__bit_spin_unlock(PG_locked, &page->flags);
}

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/* Interrupts must be disabled (for the fallback code to work right) */
static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
		void *freelist_old, unsigned long counters_old,
		void *freelist_new, unsigned long counters_new,
		const char *n)
{
	VM_BUG_ON(!irqs_disabled());
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#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
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	if (s->flags & __CMPXCHG_DOUBLE) {
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		if (cmpxchg_double(&page->freelist, &page->counters,
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			freelist_old, counters_old,
			freelist_new, counters_new))
		return 1;
	} else
#endif
	{
		slab_lock(page);
		if (page->freelist == freelist_old && page->counters == counters_old) {
			page->freelist = freelist_new;
			page->counters = counters_new;
			slab_unlock(page);
			return 1;
		}
		slab_unlock(page);
	}

	cpu_relax();
	stat(s, CMPXCHG_DOUBLE_FAIL);

#ifdef SLUB_DEBUG_CMPXCHG
	printk(KERN_INFO "%s %s: cmpxchg double redo ", n, s->name);
#endif

	return 0;
}

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static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
		void *freelist_old, unsigned long counters_old,
		void *freelist_new, unsigned long counters_new,
		const char *n)
{
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#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
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	if (s->flags & __CMPXCHG_DOUBLE) {
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		if (cmpxchg_double(&page->freelist, &page->counters,
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			freelist_old, counters_old,
			freelist_new, counters_new))
		return 1;
	} else
#endif
	{
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		unsigned long flags;

		local_irq_save(flags);
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		slab_lock(page);
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		if (page->freelist == freelist_old && page->counters == counters_old) {
			page->freelist = freelist_new;
			page->counters = counters_new;
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			slab_unlock(page);
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			local_irq_restore(flags);
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			return 1;
		}
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		slab_unlock(page);
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		local_irq_restore(flags);
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	}

	cpu_relax();
	stat(s, CMPXCHG_DOUBLE_FAIL);

#ifdef SLUB_DEBUG_CMPXCHG
	printk(KERN_INFO "%s %s: cmpxchg double redo ", n, s->name);
#endif

	return 0;
}

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#ifdef CONFIG_SLUB_DEBUG
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/*
 * Determine a map of object in use on a page.
 *
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 * Node listlock must be held to guarantee that the page does
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 * not vanish from under us.
 */
static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map)
{
	void *p;
	void *addr = page_address(page);

	for (p = page->freelist; p; p = get_freepointer(s, p))
		set_bit(slab_index(p, s, addr), map);
}

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/*
 * Debug settings:
 */
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#ifdef CONFIG_SLUB_DEBUG_ON
static int slub_debug = DEBUG_DEFAULT_FLAGS;
#else
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static int slub_debug;
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#endif
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static char *slub_debug_slabs;
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static int disable_higher_order_debug;
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/*
 * Object debugging
 */
static void print_section(char *text, u8 *addr, unsigned int length)
{
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	print_hex_dump(KERN_ERR, text, DUMP_PREFIX_ADDRESS, 16, 1, addr,
			length, 1);
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}

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,
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			enum track_item alloc, unsigned long addr)
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{
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	struct track *p = get_track(s, object, alloc);
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	if (addr) {
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#ifdef CONFIG_STACKTRACE
		struct stack_trace trace;
		int i;

		trace.nr_entries = 0;
		trace.max_entries = TRACK_ADDRS_COUNT;
		trace.entries = p->addrs;
		trace.skip = 3;
		save_stack_trace(&trace);

		/* See rant in lockdep.c */
		if (trace.nr_entries != 0 &&
		    trace.entries[trace.nr_entries - 1] == ULONG_MAX)
			trace.nr_entries--;

		for (i = trace.nr_entries; i < TRACK_ADDRS_COUNT; i++)
			p->addrs[i] = 0;
#endif
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		p->addr = addr;
		p->cpu = smp_processor_id();
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		p->pid = current->pid;
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		p->when = jiffies;
	} else
		memset(p, 0, sizeof(struct track));
}

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

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	set_track(s, object, TRACK_FREE, 0UL);
	set_track(s, object, TRACK_ALLOC, 0UL);
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}

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

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	printk(KERN_ERR "INFO: %s in %pS age=%lu cpu=%u pid=%d\n",
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		s, (void *)t->addr, jiffies - t->when, t->cpu, t->pid);
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#ifdef CONFIG_STACKTRACE
	{
		int i;
		for (i = 0; i < TRACK_ADDRS_COUNT; i++)
			if (t->addrs[i])
				printk(KERN_ERR "\t%pS\n", (void *)t->addrs[i]);
			else
				break;
	}
#endif
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}

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)
{
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	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);
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}

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");
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	printk(KERN_ERR "BUG %s (%s): %s\n", s->name, print_tainted(), buf);
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	printk(KERN_ERR "----------------------------------------"
			"-------------------------------------\n\n");
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}

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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)
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{
	unsigned int off;	/* Offset of last byte */
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	u8 *addr = page_address(page);
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	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)
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		print_section("Bytes b4 ", p - 16, 16);
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	print_section("Object ", p, min_t(unsigned long, s->objsize,
				PAGE_SIZE));
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	if (s->flags & SLAB_RED_ZONE)
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		print_section("Redzone ", p + s->objsize,
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			s->inuse - s->objsize);

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

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	if (s->flags & SLAB_STORE_USER)
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		off += 2 * sizeof(struct track);

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

static void object_err(struct kmem_cache *s, struct page *page,
			u8 *object, char *reason)
{
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	slab_bug(s, "%s", reason);
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	print_trailer(s, page, object);
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}

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

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	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
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	va_end(args);
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	slab_bug(s, "%s", buf);
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	print_page_info(page);
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	dump_stack();
}

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

	if (s->flags & __OBJECT_POISON) {
		memset(p, POISON_FREE, s->objsize - 1);
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		p[s->objsize - 1] = POISON_END;
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	}

	if (s->flags & SLAB_RED_ZONE)
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		memset(p + s->objsize, val, s->inuse - s->objsize);
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}

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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,
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			u8 *start, unsigned int value, unsigned int bytes)
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{
	u8 *fault;
	u8 *end;

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	fault = memchr_inv(start, value, bytes);
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	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;
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}

/*
 * 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.
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 *
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 * 	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.
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 * 	Padding is extended by another word if Redzoning is enabled and
 * 	objsize == inuse.
 *
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 * 	We fill with 0xbb (RED_INACTIVE) for inactive objects and with
 * 	0xcc (RED_ACTIVE) for objects in use.
 *
 * object + s->inuse
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 * 	Meta data starts here.
 *
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 * 	A. Free pointer (if we cannot overwrite object on free)
 * 	B. Tracking data for SLAB_STORE_USER
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 * 	C. Padding to reach required alignment boundary or at mininum
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 * 		one word if debugging is on to be able to detect writes
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 * 		before the word boundary.
 *
 *	Padding is done using 0x5a (POISON_INUSE)
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 *
 * object + s->size
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 * 	Nothing is used beyond s->size.
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 *
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 * If slabcaches are merged then the objsize and inuse boundaries are mostly
 * ignored. And therefore no slab options that rely on these boundaries
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 * 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;

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	return check_bytes_and_report(s, page, p, "Object padding",
				p + off, POISON_INUSE, s->size - off);
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}

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/* Check the pad bytes at the end of a slab page */
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static int slab_pad_check(struct kmem_cache *s, struct page *page)
{
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	u8 *start;
	u8 *fault;
	u8 *end;
	int length;
	int remainder;
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	if (!(s->flags & SLAB_POISON))
		return 1;

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	start = page_address(page);
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	length = (PAGE_SIZE << compound_order(page)) - s->reserved;
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	end = start + length;
	remainder = length % s->size;
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	if (!remainder)
		return 1;

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	fault = memchr_inv(end - remainder, POISON_INUSE, remainder);
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	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);
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	print_section("Padding ", end - remainder, remainder);
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	restore_bytes(s, "slab padding", POISON_INUSE, end - remainder, end);
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	return 0;
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}

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

	if (s->flags & SLAB_RED_ZONE) {
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		if (!check_bytes_and_report(s, page, object, "Redzone",
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			endobject, val, s->inuse - s->objsize))
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			return 0;
	} else {
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		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);
		}
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	}

	if (s->flags & SLAB_POISON) {
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		if (val != SLUB_RED_ACTIVE && (s->flags & __OBJECT_POISON) &&
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			(!check_bytes_and_report(s, page, p, "Poison", p,
					POISON_FREE, s->objsize - 1) ||
			 !check_bytes_and_report(s, page, p, "Poison",
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				p + s->objsize - 1, POISON_END, 1)))
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			return 0;
		/*
		 * check_pad_bytes cleans up on its own.
		 */
		check_pad_bytes(s, page, p);
	}

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	if (!s->offset && val == SLUB_RED_ACTIVE)
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		/*
		 * 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");
		/*
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		 * No choice but to zap it and thus lose the remainder
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		 * of the free objects in this slab. May cause
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		 * another error because the object count is now wrong.
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		 */
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		set_freepointer(s, p, NULL);
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		return 0;
	}
	return 1;
}

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

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	VM_BUG_ON(!irqs_disabled());

	if (!PageSlab(page)) {
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		slab_err(s, page, "Not a valid slab page");
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		return 0;
	}
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	maxobj = order_objects(compound_order(page), s->size, s->reserved);
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	if (page->objects > maxobj) {
		slab_err(s, page, "objects %u > max %u",
			s->name, page->objects, maxobj);
		return 0;
	}
	if (page->inuse > page->objects) {
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		slab_err(s, page, "inuse %u > max %u",
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			s->name, page->inuse, page->objects);
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		return 0;
	}
	/* Slab_pad_check fixes things up after itself */
	slab_pad_check(s, page);
	return 1;
}

/*
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 * 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.
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 */
static int on_freelist(struct kmem_cache *s, struct page *page, void *search)
{
	int nr = 0;
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	void *fp;
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	void *object = NULL;
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	unsigned long max_objects;
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	fp = page->freelist;
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	while (fp && nr <= page->objects) {
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		if (fp == search)
			return 1;
		if (!check_valid_pointer(s, page, fp)) {
			if (object) {
				object_err(s, page, object,
					"Freechain corrupt");
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				set_freepointer(s, object, NULL);
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				break;
			} else {
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				slab_err(s, page, "Freepointer corrupt");
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				page->freelist = NULL;
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				page->inuse = page->objects;
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				slab_fix(s, "Freelist cleared");
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				return 0;
			}
			break;
		}
		object = fp;
		fp = get_freepointer(s, object);
		nr++;
	}

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	max_objects = order_objects(compound_order(page), s->size, s->reserved);
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	if (max_objects > MAX_OBJS_PER_PAGE)
		max_objects = MAX_OBJS_PER_PAGE;
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	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.");
	}
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	if (page->inuse != page->objects - nr) {
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		slab_err(s, page, "Wrong object count. Counter is %d but "
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			"counted were %d", page->inuse, page->objects - nr);
		page->inuse = page->objects - nr;
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		slab_fix(s, "Object count adjusted.");
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	}
	return search == NULL;
}

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static void trace(struct kmem_cache *s, struct page *page, void *object,
								int alloc)
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{
	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)
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			print_section("Object ", (void *)object, s->objsize);
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		dump_stack();
	}
}

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/*
 * Hooks for other subsystems that check memory allocations. In a typical
 * production configuration these hooks all should produce no code at all.
 */
static inline int slab_pre_alloc_hook(struct kmem_cache *s, gfp_t flags)
{
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	flags &= gfp_allowed_mask;
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	lockdep_trace_alloc(flags);
	might_sleep_if(flags & __GFP_WAIT);

	return should_failslab(s->objsize, flags, s->flags);
}

static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags, void *object)
{
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	flags &= gfp_allowed_mask;
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	kmemcheck_slab_alloc(s, flags, object, slab_ksize(s));
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	kmemleak_alloc_recursive(object, s->objsize, 1, s->flags, flags);
}

static inline void slab_free_hook(struct kmem_cache *s, void *x)
{
	kmemleak_free_recursive(x, s->flags);

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	/*
	 * Trouble is that we may no longer disable interupts in the fast path
	 * So in order to make the debug calls that expect irqs to be
	 * disabled we need to disable interrupts temporarily.
	 */
#if defined(CONFIG_KMEMCHECK) || defined(CONFIG_LOCKDEP)
	{
		unsigned long flags;

		local_irq_save(flags);
		kmemcheck_slab_free(s, x, s->objsize);
		debug_check_no_locks_freed(x, s->objsize);
		local_irq_restore(flags);
	}
#endif
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	if (!(s->flags & SLAB_DEBUG_OBJECTS))
		debug_check_no_obj_freed(x, s->objsize);
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}

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/*
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 * Tracking of fully allocated slabs for debugging purposes.
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 *
 * list_lock must be held.
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 */
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static void add_full(struct kmem_cache *s,
	struct kmem_cache_node *n, struct page *page)
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{
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	if (!(s->flags & SLAB_STORE_USER))
		return;

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	list_add(&page->lru, &n->full);
}

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/*
 * list_lock must be held.
 */
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static void remove_full(struct kmem_cache *s, struct page *page)
{
	if (!(s->flags & SLAB_STORE_USER))
		return;

	list_del(&page->lru);
}

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/* 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);
}

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

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static inline void inc_slabs_node(struct kmem_cache *s, int node, int objects)
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{
	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).
	 */
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	if (n) {
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		atomic_long_inc(&n->nr_slabs);
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		atomic_long_add(objects, &n->total_objects);
	}
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}
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static inline void dec_slabs_node(struct kmem_cache *s, int node, int objects)
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{
	struct kmem_cache_node *n = get_node(s, node);

	atomic_long_dec(&n->nr_slabs);
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	atomic_long_sub(objects, &n->total_objects);
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}

/* Object debug checks for alloc/free paths */
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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;

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

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static noinline int alloc_debug_processing(struct kmem_cache *s, struct page *page,
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					void *object, unsigned long addr)
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{
	if (!check_slab(s, page))
		goto bad;

	if (!check_valid_pointer(s, page, object)) {
		object_err(s, page, object, "Freelist Pointer check fails");
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		goto bad;
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	}

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	if (!check_object(s, page, object, SLUB_RED_INACTIVE))
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		goto bad;

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	/* 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);
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	init_object(s, object, SLUB_RED_ACTIVE);
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	return 1;
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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
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		 * as used avoids touching the remaining objects.
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		 */
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		slab_fix(s, "Marking all objects used");
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		page->inuse = page->objects;
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		page->freelist = NULL;
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	}
	return 0;
}

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static noinline int free_debug_processing(struct kmem_cache *s,
		 struct page *page, void *object, unsigned long addr)
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{
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	unsigned long flags;
	int rc = 0;

	local_irq_save(flags);
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	slab_lock(page);

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	if (!check_slab(s, page))
		goto fail;

	if (!check_valid_pointer(s, page, object)) {
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		slab_err(s, page, "Invalid object pointer 0x%p", object);
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		goto fail;
	}

	if (on_freelist(s, page, object)) {
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		object_err(s, page, object, "Object already free");
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		goto fail;
	}

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	if (!check_object(s, page, object, SLUB_RED_ACTIVE))
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		goto out;
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	if (unlikely(s != page->slab)) {
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		if (!PageSlab(page)) {
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			slab_err(s, page, "Attempt to free object(0x%p) "
				"outside of slab", object);
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		} else if (!page->slab) {
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			printk(KERN_ERR
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				"SLUB <none>: no slab for object 0x%p.\n",
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						object);
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			dump_stack();
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		} else
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			object_err(s, page, object,
					"page slab pointer corrupt.");
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		goto fail;
	}
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	if (s->flags & SLAB_STORE_USER)
		set_track(s, object, TRACK_FREE, addr);
	trace(s, page, object, 0);
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	init_object(s, object, SLUB_RED_INACTIVE);
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	rc = 1;
out:
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	slab_unlock(page);
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	local_irq_restore(flags);
	return rc;
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fail:
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	slab_fix(s, "Object at 0x%p not freed", object);
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	goto out;
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}

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static int __init setup_slub_debug(char *str)
{
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	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;

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	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;
	}

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	slub_debug = 0;
	if (*str == '-')
		/*
		 * Switch off all debugging measures.
		 */
		goto out;

	/*
	 * Determine which debug features should be switched on
	 */
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	for (; *str && *str != ','; str++) {
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		switch (tolower(*str)) {
		case 'f':
			slub_debug |= SLAB_DEBUG_FREE;
			break;
		case 'z':
			slub_debug |= SLAB_RED_ZONE;
			break;
		case 'p':
			slub_debug |= SLAB_POISON;
			break;
		case 'u':
			slub_debug |= SLAB_STORE_USER;
			break;
		case 't':
			slub_debug |= SLAB_TRACE;
			break;
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		case 'a':
			slub_debug |= SLAB_FAILSLAB;
			break;
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		default:
			printk(KERN_ERR "slub_debug option '%c' "
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				"unknown. skipped\n", *str);
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		}
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	}

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check_slabs:
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	if (*str == ',')
		slub_debug_slabs = str + 1;
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out:
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	return 1;
}

__setup("slub_debug", setup_slub_debug);

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static unsigned long kmem_cache_flags(unsigned long objsize,
	unsigned long flags, const char *name,
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	void (*ctor)(void *))
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{
	/*
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	 * Enable debugging if selected on the kernel commandline.
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	 */
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	if (slub_debug && (!slub_debug_slabs ||
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		!strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs))))
		flags |= slub_debug;
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	return flags;
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}
#else
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static inline void setup_object_debug(struct kmem_cache *s,
			struct page *page, void *object) {}
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static inline int alloc_debug_processing(struct kmem_cache *s,
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	struct page *page, void *object, unsigned long addr) { return 0; }
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