/sound/isa/sb/

s-rt-imx6.git/blame/mm?id=a95f8817f8afa75ab41728bd1bb65024c65c91c3'>mm/slub.c
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/*
 * 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 or atomic operatios
 * and only uses a centralized lock to manage a pool of partial slabs.
 *
 * (C) 2007 SGI, Christoph Lameter
 * (C) 2011 Linux Foundation, Christoph Lameter
 */

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

#include <trace/events/kmem.h>

/*
 * Lock order:
 *   1. slub_lock (Global Semaphore)
 *   2. node->list_lock
 *   3. slab_lock(page) (Only on some arches and for debugging)
 *
 *   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.
 *
 *   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.
 *
 * 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
 * freed then the slab will show up again on the partial lists.
 * We track full slabs for debugging purposes though because otherwise we
 * cannot scan all objects.
 *
 * 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.
 *
 * 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
 * 			freelist that allows lockless access to
 * 			free objects in addition to the regular freelist
 * 			that requires the slab lock.
 *
 * PageError		Slab requires special handling due to debug
 * 			options set. This moves	slab handling out of
 * 			the fast path and disables lockless freelists.
 */

#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)
{
#ifdef CONFIG_SLUB_DEBUG
	return unlikely(s->flags & SLAB_DEBUG_FLAGS);
#else
	return 0;
#endif
}

/*
 * 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

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

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

/*
 * 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

#define DEBUG_DEFAULT_FLAGS (SLAB_DEBUG_FREE | SLAB_RED_ZONE | \
				SLAB_POISON | SLAB_STORE_USER)

/*
 * 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.
 */
#define DEBUG_METADATA_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)

/*
 * Set of flags that will prevent slab merging
 */
#define SLUB_NEVER_MERGE (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER | \
		SLAB_TRACE | SLAB_DESTROY_BY_RCU | SLAB_NOLEAKTRACE | \
		SLAB_FAILSLAB)

#define SLUB_MERGE_SAME (SLAB_DEBUG_FREE | SLAB_RECLAIM_ACCOUNT | \
		SLAB_CACHE_DMA | SLAB_NOTRACK)

#define OO_SHIFT	16
#define OO_MASK		((1 << OO_SHIFT) - 1)
#define MAX_OBJS_PER_PAGE	32767 /* since page.objects is u15 */

/* Internal SLUB flags */
#define __OBJECT_POISON		0x80000000UL /* Poison object */
#define __CMPXCHG_DOUBLE	0x40000000UL /* Use cmpxchg_double */

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_node works */
	UP,		/* Everything works but does not show up in sysfs */
	SYSFS		/* Sysfs up */
} slab_state = DOWN;

/* A list of all slab caches on the system */
static DECLARE_RWSEM(slub_lock);
static LIST_HEAD(slab_caches);

/*
 * Tracking user of a slab.
 */
#define TRACK_ADDRS_COUNT 16
struct track {
	unsigned long addr;	/* Called from address */
#ifdef CONFIG_STACKTRACE
	unsigned long addrs[TRACK_ADDRS_COUNT];	/* Called from address */
#endif
	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 };

#ifdef CONFIG_SYSFS
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 *);

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

#endif

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

/********************************************************************
 * 			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];
}

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

	if (!object)
		return 1;

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

	return 1;
}

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

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;
}

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

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;
}

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

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

	return x;
}

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

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

/*
 * 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);
}

/* 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());
#ifdef CONFIG_CMPXCHG_DOUBLE
	if (s->flags & __CMPXCHG_DOUBLE) {
		if (cmpxchg_double(&page->freelist,
			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;
}

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)
{
#ifdef CONFIG_CMPXCHG_DOUBLE
	if (s->flags & __CMPXCHG_DOUBLE) {
		if (cmpxchg_double(&page->freelist,
			freelist_old, counters_old,
			freelist_new, counters_new))
		return 1;
	} else
#endif
	{
		unsigned long flags;

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

	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;
}

#ifdef CONFIG_SLUB_DEBUG
/*
 * Determine a map of object in use on a page.
 *
 * Node listlock must be held to guarantee that the page does
 * 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);
}

/*
 * Debug settings:
 */
#ifdef CONFIG_SLUB_DEBUG_ON
static int slub_debug = DEBUG_DEFAULT_FLAGS;
#else
static int slub_debug;
#endif

static char *slub_debug_slabs;
static int disable_higher_order_debug;

/*
 * Object debugging
 */
static void print_section(char *text, u8 *addr, unsigned int length)
{
	print_hex_dump(KERN_ERR, text, DUMP_PREFIX_ADDRESS, 16, 1, addr,
			length, 1);
}

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,
			enum track_item alloc, unsigned long addr)
{
	struct track *p = get_track(s, object, alloc);

	if (addr) {
#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
		p->addr = addr;
		p->cpu = smp_processor_id();
		p->pid = current->pid;
		p->when = jiffies;
	} else
		memset(p, 0, sizeof(struct track));
}

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

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

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

	printk(KERN_ERR "INFO: %s in %pS age=%lu cpu=%u pid=%d\n",
		s, (void *)t->addr, jiffies - t->when, t->cpu, t->pid);
#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
}

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)
{
	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);

}

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");
}

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)
{
	unsigned int off;	/* Offset of last byte */
	u8 *addr = page_address(page);

	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);

	print_section("Object ", p, min_t(unsigned long, s->objsize,
				PAGE_SIZE));
	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;

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

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

	dump_stack();
}

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

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

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

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

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

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

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

	fault = memchr_inv(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;
}

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

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

/* Check the pad bytes at the end of a slab page */
static int slab_pad_check(struct kmem_cache *s, struct page *page)
{
	u8 *start;
	u8 *fault;
	u8 *end;
	int length;
	int remainder;

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

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

	fault = memchr_inv(end - remainder, POISON_INUSE, remainder);
	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);
	print_section("Padding ", end - remainder, remainder);

	restore_bytes(s, "slab padding", POISON_INUSE, end - remainder, end);
	return 0;
}

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

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

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

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

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

	VM_BUG_ON(!irqs_disabled());

	if (!PageSlab(page)) {
		slab_err(s, page, "Not a valid slab page");
		return 0;
	}

	maxobj = order_objects(compound_order(page), s->size, s->reserved);
	if (page->objects > maxobj) {
		slab_err(s, page, "objects %u > max %u",
			s->name, page->objects, maxobj);
		return 0;
	}
	if (page->inuse > page->objects) {
		slab_err(s, page, "inuse %u > max %u",
			s->name, page->inuse, page->objects);
		return 0;
	}
	/* Slab_pad_check fixes things up after itself */
	slab_pad_check(s, page);
	return 1;
}

/*
 * 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.
 */
static int on_freelist(struct kmem_cache *s, struct page *page, void *search)
{
	int nr = 0;
	void *fp;
	void *object = NULL;
	unsigned long max_objects;

	fp = page->freelist;
	while (fp && nr <= page->objects) {
		if (fp == search)
			return 1;
		if (!check_valid_pointer(s, page, fp)) {
			if (object) {
				object_err(s, page, object,
					"Freechain corrupt");
				set_freepointer(s, object, NULL);
				break;
			} else {
				slab_err(s, page, "Freepointer corrupt");
				page->freelist = NULL;
				page->inuse = page->objects;
				slab_fix(s, "Freelist cleared");
				return 0;
			}
			break;
		}
		object = fp;
		fp = get_freepointer(s, object);
		nr++;
	}

	max_objects = order_objects(compound_order(page), s->size, s->reserved);
	if (max_objects > MAX_OBJS_PER_PAGE)
		max_objects = MAX_OBJS_PER_PAGE;

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

static void trace(struct kmem_cache *s, struct page *page, void *object,
								int alloc)
{
	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();
	}
}

/*
 * 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)
{
	flags &= gfp_allowed_mask;
	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)
{
	flags &= gfp_allowed_mask;
	kmemcheck_slab_alloc(s, flags, object, slab_ksize(s));
	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);

	/*
	 * 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
	if (!(s->flags & SLAB_DEBUG_OBJECTS))
		debug_check_no_obj_freed(x, s->objsize);
}

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

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

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

	list_del(&page->lru);
}

/* 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);
}

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

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

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

/* Object debug checks for alloc/free paths */
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, SLUB_RED_INACTIVE);
	init_tracking(s, object);
}

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

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

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

	/* 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, SLUB_RED_ACTIVE);
	return 1;

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

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

	local_irq_save(flags);
	slab_lock(page);

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

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

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

	if (!check_object(s, page, object, SLUB_RED_ACTIVE))
		goto out;

	if (unlikely(s != page->slab)) {
		if (!PageSlab(page)) {
			slab_err(s, page, "Attempt to free object(0x%p) "
				"outside of slab", object);
		} else if (!page->slab) {
			printk(KERN_ERR
				"SLUB <none>: no slab for object 0x%p.\n",
						object);
			dump_stack();
		} else
			object_err(s, page, object,
					"page slab pointer corrupt.");
		goto fail;
	}

	if (s->flags & SLAB_STORE_USER)
		set_track(s, object, TRACK_FREE, addr);
	trace(s, page, object, 0);
	init_object(s, object, SLUB_RED_INACTIVE);
	rc = 1;
out:
	slab_unlock(page);
	local_irq_restore(flags);
	return rc;

fail:
	slab_fix(s, "Object at 0x%p not freed", object);
	goto out;
}

static int __init setup_slub_debug(char *str)
{
	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;

	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;
	}

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

	/*
	 * Determine which debug features should be switched on
	 */
	for (; *str && *str != ','; str++) {
		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;
		case 'a':
			slub_debug |= SLAB_FAILSLAB;
			break;
		default:
			printk(KERN_ERR "slub_debug option '%c' "
				"unknown. skipped\n", *str);
		}
	}

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

__setup("slub_debug", setup_slub_debug);

static unsigned long kmem_cache_flags(unsigned long objsize,
	unsigned long flags, const char *name,
	void (*ctor)(void *))
{
	/*
	 * Enable debugging if selected on the kernel commandline.
	 */
	if (slub_debug && (!slub_debug_slabs ||
		!strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs))))
		flags |= slub_debug;

	return flags;
}
#else
static inline void setup_object_debug(struct kmem_cache *s,
			struct page *page, void *object) {}

static inline int alloc_debug_processing(struct kmem_cache *s,
	struct page *page, void *object, unsigned long addr) { return 0; }

static inline int free_debug_processing(struct kmem_cache *s,
	struct page *page, void *object, unsigned long addr) { return 0; }

static inline int slab_pad_check(struct kmem_cache *s, struct page *page)
			{ return 1; }
static inline int check_object(struct kmem_cache *s, struct page *page,
			void *object, u8 val) { return 1; }
static inline void add_full(struct kmem_cache *s, struct kmem_cache_node *n,
					struct page *page) {}
static inline void remove_full(struct kmem_cache *s, struct page *page) {}
static inline unsigned long kmem_cache_flags(unsigned long objsize,
	unsigned long flags, const char *name,
	void (*ctor)(void *))
{
	return flags;
}
#define slub_debug 0

#define disable_higher_order_debug 0

static inline unsigned long slabs_node(struct kmem_cache *s, int node)
							{ return 0; }
static inline unsigned long node_nr_slabs(struct kmem_cache_node *n)
							{ return 0; }
static inline void inc_slabs_node(struct kmem_cache *s, int node,
							int objects) {}
static inline void dec_slabs_node(struct kmem_cache *s, int node,
							int objects) {}

static inline int slab_pre_alloc_hook(struct kmem_cache *s, gfp_t flags)
							{ return 0; }

static inline void slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags,
		void *object) {}

static inline void slab_free_hook(struct kmem_cache *s, void *x) {}

#endif /* CONFIG_SLUB_DEBUG */

/*
 * Slab allocation and freeing
 */
static inline struct page *alloc_slab_page(gfp_t flags, int node,
					struct kmem_cache_order_objects oo)
{
	int order = oo_order(oo);

	flags |= __GFP_NOTRACK;

	if (node == NUMA_NO_NODE)
		return alloc_pages(flags, order);
	else
		return alloc_pages_exact_node(node, flags, order);
}

static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
{
	struct page *page;
	struct kmem_cache_order_objects oo = s->oo;
	gfp_t alloc_gfp;

	flags &= gfp_allowed_mask;

	if (flags & __GFP_WAIT)
		local_irq_enable();

	flags |= s->allocflags;

	/*
	 * Let the initial higher-order allocation fail under memory pressure
	 * so we fall-back to the minimum order allocation.
	 */
	alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL;

	page = alloc_slab_page(alloc_gfp, node, oo);
	if (unlikely(!page)) {
		oo = s->min;
		/*
		 * Allocation may have failed due to fragmentation.
		 * Try a lower order alloc if possible
		 */
		page = alloc_slab_page(flags, node, oo);

		if (page)
			stat(s, ORDER_FALLBACK);
	}

	if (flags & __GFP_WAIT)
		local_irq_disable();

	if (!page)
		return NULL;

	if (kmemcheck_enabled
		&& !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
		int pages = 1 << oo_order(oo);

		kmemcheck_alloc_shadow(page, oo_order(oo), flags, node);

		/*
		 * Objects from caches that have a constructor don't get
		 * cleared when they're allocated, so we need to do it here.
		 */
		if (s->ctor)
			kmemcheck_mark_uninitialized_pages(page, pages);
		else
			kmemcheck_mark_unallocated_pages(page, pages);
	}

	page->objects = oo_objects(oo);
	mod_zone_page_state(page_zone(page),
		(s->flags & SLAB_RECLAIM_ACCOUNT) ?
		NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
		1 << oo_order(oo));

	return page;
}

static void setup_object(struct kmem_cache *s, struct page *page,
				void *object)
{
	setup_object_debug(s, page, object);
	if (unlikely(s->ctor))
		s->ctor(object);
}

static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
{
	struct page *page;
	void *start;
	void *last;
	void *p;

	BUG_ON(flags & GFP_SLAB_BUG_MASK);

	page = allocate_slab(s,
		flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
	if (!page)
		goto out;

	inc_slabs_node(s, page_to_nid(page), page->objects);
	page->slab = s;
	page->flags |= 1 << PG_slab;

	start = page_address(page);

	if (unlikely(s->flags & SLAB_POISON))
		memset(start, POISON_INUSE, PAGE_SIZE << compound_order(page));

	last = start;
	for_each_object(p, s, start, page->objects) {
		setup_object(s, page, last);
		set_freepointer(s, last, p);
		last = p;
	}
	setup_object(s, page, last);
	set_freepointer(s, last, NULL);

	page->freelist = start;
	page->inuse = page->objects;
	page->frozen = 1;
out:
	return page;
}

static void __free_slab(struct kmem_cache *s, struct page *page)
{
	int order = compound_order(page);
	int pages = 1 << order;

	if (kmem_cache_debug(s)) {
		void *p;

		slab_pad_check(s, page);
		for_each_object(p, s, page_address(page),
						page->objects)
			check_object(s, page, p, SLUB_RED_INACTIVE);
	}

	kmemcheck_free_shadow(page, compound_order(page));

	mod_zone_page_state(page_zone(page),
		(s->flags & SLAB_RECLAIM_ACCOUNT) ?
		NR_SLAB_RECLAIMABLE : NR_SLAB_UNRECLAIMABLE,
		-pages);

	__ClearPageSlab(page);
	reset_page_mapcount(page);
	if (current->reclaim_state)
		current->reclaim_state->reclaimed_slab += pages;
	__free_pages(page, order);
}

#define need_reserve_slab_rcu						\
	(sizeof(((struct page *)NULL)->lru) < sizeof(struct rcu_head))

static void rcu_free_slab(struct rcu_head *h)
{
	struct page *page;

	if (need_reserve_slab_rcu)
		page = virt_to_head_page(h);
	else
		page = container_of((struct list_head *)h, struct page, lru);

	__free_slab(page->slab, page);
}

static void free_slab(struct kmem_cache *s, struct page *page)
{
	if (unlikely(s->flags & SLAB_DESTROY_BY_RCU)) {
		struct rcu_head *head;

		if (need_reserve_slab_rcu) {
			int order = compound_order(page);
			int offset = (PAGE_SIZE << order) - s->reserved;

			VM_BUG_ON(s->reserved != sizeof(*head));
			head = page_address(page) + offset;
		} else {
			/*
			 * RCU free overloads the RCU head over the LRU
			 */
			head = (void *)&page->lru;
		}

		call_rcu(head, rcu_free_slab);
	} else
		__free_slab(s, page);
}

static void discard_slab(struct kmem_cache *s, struct page *page)
{
	dec_slabs_node(s, page_to_nid(page), page->objects);
	free_slab(s, page);
}

/*
 * Management of partially allocated slabs.
 *
 * list_lock must be held.
 */
static inline void add_partial(struct kmem_cache_node *n,
				struct page *page, int tail)
{
	n->nr_partial++;
	if (tail == DEACTIVATE_TO_TAIL)
		list_add_tail(&page->lru, &n->partial);
	else
		list_add(&page->lru, &n->partial);
}

/*
 * list_lock must be held.
 */
static inline void remove_partial(struct kmem_cache_node *n,
					struct page *page)
{
	list_del(&page->lru);
	n->nr_partial--;
}

/*
 * Lock slab, remove from the partial list and put the object into the
 * per cpu freelist.
 *
 * Returns a list of objects or NULL if it fails.
 *
 * Must hold list_lock.
 */
static inline void *acquire_slab(struct kmem_cache *s,
		struct kmem_cache_node *n, struct page *page,
		int mode)
{
	void *freelist;
	unsigned long counters;
	struct page new;

	/*
	 * Zap the freelist and set the frozen bit.
	 * The old freelist is the list of objects for the
	 * per cpu allocation list.
	 */
	do {
		freelist = page->freelist;
		counters = page->counters;
		new.counters = counters;
		if (mode)
			new.inuse = page->objects;

		VM_BUG_ON(new.frozen);
		new.frozen = 1;

	} while (!__cmpxchg_double_slab(s, page,
			freelist, counters,
			NULL, new.counters,
			"lock and freeze"));

	remove_partial(n, page);
	return freelist;
}

static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain);

/*
 * Try to allocate a partial slab from a specific node.
 */
static void *get_partial_node(struct kmem_cache *s,
		struct kmem_cache_node *n, struct kmem_cache_cpu *c)
{
	struct page *page, *page2;
	void *object = NULL;

	/*
	 * Racy check. If we mistakenly see no partial slabs then we
	 * just allocate an empty slab. If we mistakenly try to get a
	 * partial slab and there is none available then get_partials()
	 * will return NULL.
	 */
	if (!n || !n->nr_partial)
		return NULL;

	spin_lock(&n->list_lock);
	list_for_each_entry_safe(page, page2, &n->partial, lru) {
		void *t = acquire_slab(s, n, page, object == NULL);
		int available;

		if (!t)
			break;

		if (!object) {
			c->page = page;
			c->node = page_to_nid(page);
			stat(s, ALLOC_FROM_PARTIAL);
			object = t;
			available =  page->objects - page->inuse;
		} else {
			page->freelist = t;
			available = put_cpu_partial(s, page, 0);
		}
		if (kmem_cache_debug(s) || available > s->cpu_partial / 2)
			break;

	}
	spin_unlock(&n->list_lock);
	return object;
}

/*
 * Get a page from somewhere. Search in increasing NUMA distances.
 */
static struct page *get_any_partial(struct kmem_cache *s, gfp_t flags,
		struct kmem_cache_cpu *c)
{
#ifdef CONFIG_NUMA
	struct zonelist *zonelist;
	struct zoneref *z;
	struct zone *zone;
	enum zone_type high_zoneidx = gfp_zone(flags);
	void *object;

	/*
	 * The defrag ratio allows a configuration of the tradeoffs between
	 * inter node defragmentation and node local allocations. A lower
	 * defrag_ratio increases the tendency to do local allocations
	 * instead of attempting to obtain partial slabs from other nodes.
	 *
	 * If the defrag_ratio is set to 0 then kmalloc() always
	 * returns node local objects. If the ratio is higher then kmalloc()
	 * may return off node objects because partial slabs are obtained
	 * from other nodes and filled up.
	 *
	 * If /sys/kernel/slab/xx/defrag_ratio is set to 100 (which makes
	 * defrag_ratio = 1000) then every (well almost) allocation will
	 * first attempt to defrag slab caches on other nodes. This means
	 * scanning over all nodes to look for partial slabs which may be
	 * expensive if we do it every time we are trying to find a slab
	 * with available objects.
	 */
	if (!s->remote_node_defrag_ratio ||
			get_cycles() % 1024 > s->remote_node_defrag_ratio)
		return NULL;

	get_mems_allowed();
	zonelist = node_zonelist(slab_node(current->mempolicy), flags);
	for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
		struct kmem_cache_node *n;

		n = get_node(s, zone_to_nid(zone));

		if (n && cpuset_zone_allowed_hardwall(zone, flags) &&
				n->nr_partial > s->min_partial) {
			object = get_partial_node(s, n, c);
			if (object) {
				put_mems_allowed();
				return object;
			}
		}
	}
	put_mems_allowed();
#endif
	return NULL;
}

/*
 * Get a partial page, lock it and return it.
 */
static void *get_partial(struct kmem_cache *s, gfp_t flags, int node,
		struct kmem_cache_cpu *c)
{
	void *object;
	int searchnode = (node == NUMA_NO_NODE) ? numa_node_id() : node;

	object = get_partial_node(s, get_node(s, searchnode), c);
	if (object || node != NUMA_NO_NODE)
		return object;

	return get_any_partial(s, flags, c);
}

#ifdef CONFIG_PREEMPT
/*
 * Calculate the next globally unique transaction for disambiguiation
 * during cmpxchg. The transactions start with the cpu number and are then
 * incremented by CONFIG_NR_CPUS.
 */
#define TID_STEP  roundup_pow_of_two(CONFIG_NR_CPUS)
#else
/*
 * No preemption supported therefore also no need to check for
 * different cpus.
 */
#define TID_STEP 1
#endif

static inline unsigned long next_tid(unsigned long tid)
{
	return tid + TID_STEP;
}

static inline unsigned int tid_to_cpu(unsigned long tid)
{
	return tid % TID_STEP;
}

static inline unsigned long tid_to_event(unsigned long tid)
{
	return tid / TID_STEP;
}

static inline unsigned int init_tid(int cpu)
{
	return cpu;
}

static inline void note_cmpxchg_failure(const char *n,
		const struct kmem_cache *s, unsigned long tid)
{
#ifdef SLUB_DEBUG_CMPXCHG
	unsigned long actual_tid = __this_cpu_read(s->cpu_slab->tid);

	printk(KERN_INFO "%s %s: cmpxchg redo ", n, s->name);

#ifdef CONFIG_PREEMPT
	if (tid_to_cpu(tid) != tid_to_cpu(actual_tid))
		printk("due to cpu change %d -> %d\n",
			tid_to_cpu(tid), tid_to_cpu(actual_tid));
	else
#endif
	if (tid_to_event(tid) != tid_to_event(actual_tid))
		printk("due to cpu running other code. Event %ld->%ld\n",
			tid_to_event(tid), tid_to_event(actual_tid));
	else
		printk("for unknown reason: actual=%lx was=%lx target=%lx\n",
			actual_tid, tid, next_tid(tid));
#endif
	stat(s, CMPXCHG_DOUBLE_CPU_FAIL);
}

void init_kmem_cache_cpus(struct kmem_cache *s)
{
	int cpu;

	for_each_possible_cpu(cpu)
		per_cpu_ptr(s->cpu_slab, cpu)->tid = init_tid(cpu);
}

/*
 * Remove the cpu slab
 */
static void deactivate_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
{
	enum slab_modes { M_NONE, M_PARTIAL, M_FULL, M_FREE };
	struct page *page = c->page;
	struct kmem_cache_node *n = get_node(s, page_to_nid(page));
	int lock = 0;
	enum slab_modes l = M_NONE, m = M_NONE;
	void *freelist;
	void *nextfree;
	int tail = DEACTIVATE_TO_HEAD;
	struct page new;
	struct page old;

	if (page->freelist) {
		stat(s, DEACTIVATE_REMOTE_FREES);
		tail = DEACTIVATE_TO_TAIL;
	}

	c->tid = next_tid(c->tid);
	c->page = NULL;
	freelist = c->freelist;
	c->freelist = NULL;

	/*
	 * Stage one: Free all available per cpu objects back
	 * to the page freelist while it is still frozen. Leave the
	 * last one.
	 *
	 * There is no need to take the list->lock because the page
	 * is still frozen.
	 */
	while (freelist && (nextfree = get_freepointer(s, freelist))) {
		void *prior;
		unsigned long counters;

		do {
			prior = page->freelist;
			counters = page->counters;
			set_freepointer(s, freelist, prior);
			new.counters = counters;
			new.inuse--;
			VM_BUG_ON(!new.frozen);

		} while (!__cmpxchg_double_slab(s, page,
			prior, counters,
			freelist, new.counters,
			"drain percpu freelist"));

		freelist = nextfree;
	}

	/*
	 * Stage two: Ensure that the page is unfrozen while the
	 * list presence reflects the actual number of objects
	 * during unfreeze.
	 *
	 * We setup the list membership and then perform a cmpxchg
	 * with the count. If there is a mismatch then the page
	 * is not unfrozen but the page is on the wrong list.
	 *
	 * Then we restart the process which may have to remove
	 * the page from the list that we just put it on again
	 * because the number of objects in the slab may have
	 * changed.
	 */
redo:

	old.freelist = page->freelist;
	old.counters = page->counters;
	VM_BUG_ON(!old.frozen);

	/* Determine target state of the slab */
	new.counters = old.counters;
	if (freelist) {
		new.inuse--;
		set_freepointer(s, freelist, old.freelist);
		new.freelist = freelist;
	} else
		new.freelist = old.freelist;

	new.frozen = 0;

	if (!new.inuse && n->nr_partial > s->min_partial)
		m = M_FREE;
	else if (new.freelist) {
		m = M_PARTIAL;
		if (!lock) {
			lock = 1;
			/*
			 * Taking the spinlock removes the possiblity
			 * that acquire_slab() will see a slab page that
			 * is frozen
			 */
			spin_lock(&n->list_lock);
		}
	} else {
		m = M_FULL;
		if (kmem_cache_debug(s) && !lock) {
			lock = 1;
			/*
			 * This also ensures that the scanning of full
			 * slabs from diagnostic functions will not see
			 * any frozen slabs.
			 */
			spin_lock(&n->list_lock);
		}
	}

	if (l != m) {

		if (l == M_PARTIAL)

			remove_partial(n, page);

		else if (l == M_FULL)

			remove_full(s, page);

		if (m == M_PARTIAL) {

			add_partial(n, page, tail);
			stat(s, tail);

		} else if (m == M_FULL) {

			stat(s, DEACTIVATE_FULL);
			add_full(s, n, page);

		}
	}

	l = m;
	if (!__cmpxchg_double_slab(s, page,
				old.freelist, old.counters,
				new.freelist, new.counters,
				"unfreezing slab"))
		goto redo;

	if (lock)
		spin_unlock(&n->list_lock);

	if (m == M_FREE) {
		stat(s, DEACTIVATE_EMPTY);
		discard_slab(s, page);
		stat(s, FREE_SLAB);
	}
}

/* Unfreeze all the cpu partial slabs */
static void unfreeze_partials(struct kmem_cache *s)
{
	struct kmem_cache_node *n = NULL;
	struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab);
	struct page *page, *discard_page = NULL;

	while ((page = c->partial)) {
		enum slab_modes { M_PARTIAL, M_FREE };
		enum slab_modes l, m;
		struct page new;
		struct page old;

		c->partial = page->next;
		l = M_FREE;

		do {

			old.freelist = page->freelist;
			old.counters = page->counters;
			VM_BUG_ON(!old.frozen);

			new.counters = old.counters;
			new.freelist = old.freelist;

			new.frozen = 0;

			if (!new.inuse && (!n || n->nr_partial > s->min_partial))
				m = M_FREE;
			else {
				struct kmem_cache_node *n2 = get_node(s,
							page_to_nid(page));

				m = M_PARTIAL;
				if (n != n2) {
					if (n)
						spin_unlock(&n->list_lock);

					n = n2;
					spin_lock(&n->list_lock);
				}
			}

			if (l != m) {
				if (l == M_PARTIAL)
					remove_partial(n, page);
				else
					add_partial(n, page,
						DEACTIVATE_TO_TAIL);

				l = m;
			}

		} while (!cmpxchg_double_slab(s, page,
				old.freelist, old.counters,
				new.freelist, new.counters,
				"unfreezing slab"));

		if (m == M_FREE) {
			page->next = discard_page;
			discard_page = page;
		}
	}

	if (n)
		spin_unlock(&n->list_lock);

	while (discard_page) {
		page = discard_page;
		discard_page = discard_page->next;

		stat(s, DEACTIVATE_EMPTY);
		discard_slab(s, page);
		stat(s, FREE_SLAB);
	}
}

/*
 * Put a page that was just frozen (in __slab_free) into a partial page
 * slot if available. This is done without interrupts disabled and without
 * preemption disabled. The cmpxchg is racy and may put the partial page
 * onto a random cpus partial slot.
 *
 * If we did not find a slot then simply move all the partials to the
 * per node partial list.
 */
int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
{
	struct page *oldpage;
	int pages;
	int pobjects;

	do {
		pages = 0;
		pobjects = 0;
		oldpage = this_cpu_read(s->cpu_slab->partial);

		if (oldpage) {
			pobjects = oldpage->pobjects;
			pages = oldpage->pages;
			if (drain && pobjects > s->cpu_partial) {
				unsigned long flags;
				/*
				 * partial array is full. Move the existing
				 * set to the per node partial list.
				 */
				local_irq_save(flags);
				unfreeze_partials(s);
				local_irq_restore(flags);
				pobjects = 0;
				pages = 0;
			}
		}

		pages++;
		pobjects += page->objects - page->inuse;

		page->pages = pages;
		page->pobjects = pobjects;
		page->next = oldpage;

	} while (irqsafe_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page) != oldpage);
	stat(s, CPU_PARTIAL_FREE);
	return pobjects;
}

static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
{
	stat(s, CPUSLAB_FLUSH);
	deactivate_slab(s, c);
}

/*
 * Flush cpu slab.
 *
 * Called from IPI handler with interrupts disabled.
 */
static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu)
{
	struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);

	if (likely(c)) {
		if (c->page)
			flush_slab(s, c);

		unfreeze_partials(s);
	}
}

static void flush_cpu_slab(void *d)
{
	struct kmem_cache *s = d;

	__flush_cpu_slab(s, smp_processor_id());
}

static void flush_all(struct kmem_cache *s)
{
	on_each_cpu(flush_cpu_slab, s, 1);
}

/*
 * Check if the objects in a per cpu structure fit numa
 * locality expectations.
 */
static inline int node_match(struct kmem_cache_cpu *c, int node)
{
#ifdef CONFIG_NUMA
	if (node != NUMA_NO_NODE && c->node != node)
		return 0;
#endif
	return 1;
}

static int count_free(struct page *page)
{
	return page->objects - page->inuse;
}

static unsigned long count_partial(struct kmem_cache_node *n,
					int (*get_count)(struct page *))
{
	unsigned long flags;
	unsigned long x = 0;
	struct page *page;

	spin_lock_irqsave(&n->list_lock, flags);
	list_for_each_entry(page, &n->partial, lru)
		x += get_count(page);
	spin_unlock_irqrestore(&n->list_lock, flags);
	return x;
}

static inline unsigned long node_nr_objs(struct kmem_cache_node *n)
{
#ifdef CONFIG_SLUB_DEBUG
	return atomic_long_read(&n->total_objects);
#else
	return 0;
#endif
}

static noinline void
slab_out_of_memory(struct kmem_cache *s, gfp_t gfpflags, int nid)
{
	int node;

	printk(KERN_WARNING
		"SLUB: Unable to allocate memory on node %d (gfp=0x%x)\n",
		nid, gfpflags);
	printk(KERN_WARNING "  cache: %s, object size: %d, buffer size: %d, "
		"default order: %d, min order: %d\n", s->name, s->objsize,
		s->size, oo_order(s->oo), oo_order(s->min));

	if (oo_order(s->min) > get_order(s->objsize))
		printk(KERN_WARNING "  %s debugging increased min order, use "
		       "slub_debug=O to disable.\n", s->name);

	for_each_online_node(node) {
		struct kmem_cache_node *n = get_node(s, node);
		unsigned long nr_slabs;
		unsigned long nr_objs;
		unsigned long nr_free;

		if (!n)
			continue;

		nr_free  = count_partial(n, count_free);
		nr_slabs = node_nr_slabs(n);
		nr_objs  = node_nr_objs(n);

		printk(KERN_WARNING
			"  node %d: slabs: %ld, objs: %ld, free: %ld\n",
			node, nr_slabs, nr_objs, nr_free);
	}
}

static inline void *new_slab_objects(struct kmem_cache *s, gfp_t flags,
			int node, struct kmem_cache_cpu **pc)
{
	void *object;
	struct kmem_cache_cpu *c;
	struct page *page = new_slab(s, flags, node);

	if (page) {
		c = __this_cpu_ptr(s->cpu_slab);
		if (c->page)
			flush_slab(s, c);

		/*
		 * No other reference to the page yet so we can
		 * muck around with it freely without cmpxchg
		 */
		object = page->freelist;
		page->freelist = NULL;

		stat(s, ALLOC_SLAB);
		c->node = page_to_nid(page);
		c->page = page;
		*pc = c;
	} else
		object = NULL;

	return object;
}

/*
 * Slow path. The lockless freelist is empty or we need to perform
 * debugging duties.
 *
 * Processing is still very fast if new objects have been freed to the
 * regular freelist. In that case we simply take over the regular freelist
 * as the lockless freelist and zap the regular freelist.
 *
 * If that is not working then we fall back to the partial lists. We take the
 * first element of the freelist as the object to allocate now and move the
 * rest of the freelist to the lockless freelist.
 *
 * And if we were unable to get a new slab from the partial slab lists then
 * we need to allocate a new slab. This is the slowest path since it involves
 * a call to the page allocator and the setup of a new slab.
 */
static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
			  unsigned long addr, struct kmem_cache_cpu *c)
{
	void **object;
	unsigned long flags;
	struct page new;
	unsigned long counters;

	local_irq_save(flags);
#ifdef CONFIG_PREEMPT
	/*
	 * We may have been preempted and rescheduled on a different
	 * cpu before disabling interrupts. Need to reload cpu area
	 * pointer.
	 */
	c = this_cpu_ptr(s->cpu_slab);
#endif

	if (!c->page)
		goto new_slab;
redo:
	if (unlikely(!node_match(c, node))) {
		stat(s, ALLOC_NODE_MISMATCH);
		deactivate_slab(s, c);
		goto new_slab;
	}

	stat(s, ALLOC_SLOWPATH);

	do {
		object = c->page->freelist;
		counters = c->page->counters;
		new.counters = counters;
		VM_BUG_ON(!new.frozen);

		/*
		 * If there is no object left then we use this loop to
		 * deactivate the slab which is simple since no objects
		 * are left in the slab and therefore we do not need to
		 * put the page back onto the partial list.
		 *
		 * If there are objects left then we retrieve them
		 * and use them to refill the per cpu queue.
		 */

		new.inuse = c->page->objects;
		new.frozen = object != NULL;

	} while (!__cmpxchg_double_slab(s, c->page,
			object, counters,
			NULL, new.counters,
			"__slab_alloc"));

	if (!object) {
		c->page = NULL;
		stat(s, DEACTIVATE_BYPASS);
		goto new_slab;
	}

	stat(s, ALLOC_REFILL);

load_freelist:
	c->freelist = get_freepointer(s, object);
	c->tid = next_tid(c->tid);
	local_irq_restore(flags);
	return object;

new_slab:

	if (c->partial) {
		c->page = c->partial;
		c->partial = c->page->next;
		c->node = page_to_nid(c->page);
		stat(s, CPU_PARTIAL_ALLOC);
		c->freelist = NULL;
		goto redo;
	}

	/* Then do expensive stuff like retrieving pages from the partial lists */
	object = get_partial(s, gfpflags, node, c);

	if (unlikely(!object)) {

		object = new_slab_objects(s, gfpflags, node, &c);

		if (unlikely(!object)) {
			if (!(gfpflags & __GFP_NOWARN) && printk_ratelimit())
				slab_out_of_memory(s, gfpflags, node);

			local_irq_restore(flags);
			return NULL;
		}
	}

	if (likely(!kmem_cache_debug(s)))
		goto load_freelist;

	/* Only entered in the debug case */
	if (!alloc_debug_processing(s, c->page, object, addr))
		goto new_slab;	/* Slab failed checks. Next slab needed */

	c->freelist = get_freepointer(s, object);
	deactivate_slab(s, c);
	c->node = NUMA_NO_NODE;
	local_irq_restore(flags);
	return object;
}

/*
 * Inlined fastpath so that allocation functions (kmalloc, kmem_cache_alloc)
 * have the fastpath folded into their functions. So no function call
 * overhead for requests that can be satisfied on the fastpath.
 *
 * The fastpath works by first checking if the lockless freelist can be used.
 * If not then __slab_alloc is called for slow processing.
 *
 * Otherwise we can simply pick the next object from the lockless free list.
 */
static __always_inline void *slab_alloc(struct kmem_cache *s,
		gfp_t gfpflags, int node, unsigned long addr)
{
	void **object;
	struct kmem_cache_cpu *c;
	unsigned long tid;

	if (slab_pre_alloc_hook(s, gfpflags))
		return NULL;

redo:

	/*
	 * Must read kmem_cache cpu data via this cpu ptr. Preemption is
	 * enabled. We may switch back and forth between cpus while
	 * reading from one cpu area. That does not matter as long
	 * as we end up on the original cpu again when doing the cmpxchg.
	 */
	c = __this_cpu_ptr(s->cpu_slab);

	/*
	 * The transaction ids are globally unique per cpu and per operation on
	 * a per cpu queue. Thus they can be guarantee that the cmpxchg_double
	 * occurs on the right processor and that there was no operation on the
	 * linked list in between.
	 */
	tid = c->tid;
	barrier();

	object = c->freelist;
	if (unlikely(!object || !node_match(c, node)))

		object = __slab_alloc(s, gfpflags, node, addr, c);

	else {
		/*
		 * The cmpxchg will only match if there was no additional
		 * operation and if we are on the right processor.
		 *
		 * The cmpxchg does the following atomically (without lock semantics!)
		 * 1. Relocate first pointer to the current per cpu area.
		 * 2. Verify that tid and freelist have not been changed
		 * 3. If they were not changed replace tid and freelist
		 *
		 * Since this is without lock semantics the protection is only against
		 * code executing on this cpu *not* from access by other cpus.
		 */
		if (unlikely(!irqsafe_cpu_cmpxchg_double(
				s->cpu_slab->freelist, s->cpu_slab->tid,
				object, tid,
				get_freepointer_safe(s, object), next_tid(tid)))) {

			note_cmpxchg_failure("slab_alloc", s, tid);
			goto redo;
		}
		stat(s, ALLOC_FASTPATH);
	}

	if (unlikely(gfpflags & __GFP_ZERO) && object)
		memset(object, 0, s->objsize);

	slab_post_alloc_hook(s, gfpflags, object);

	return object;
}

void *kmem_cache_alloc(struct kmem_cache *s, gfp_t gfpflags)
{
	void *ret = slab_alloc(s, gfpflags, NUMA_NO_NODE, _RET_IP_);

	trace_kmem_cache_alloc(_RET_IP_, ret, s->objsize, s->size, gfpflags);

	return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc);

#ifdef CONFIG_TRACING
void *kmem_cache_alloc_trace(struct kmem_cache *s, gfp_t gfpflags, size_t size)
{
	void *ret = slab_alloc(s, gfpflags, NUMA_NO_NODE, _RET_IP_);
	trace_kmalloc(_RET_IP_, ret, size, s->size, gfpflags);
	return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_trace);

void *kmalloc_order_trace(size_t size, gfp_t flags, unsigned int order)
{
	void *ret = kmalloc_order(size, flags, order);
	trace_kmalloc(_RET_IP_, ret, size, PAGE_SIZE << order, flags);
	return ret;
}
EXPORT_SYMBOL(kmalloc_order_trace);
#endif

#ifdef CONFIG_NUMA
void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node)
{
	void *ret = slab_alloc(s, gfpflags, node, _RET_IP_);

	trace_kmem_cache_alloc_node(_RET_IP_, ret,
				    s->objsize, s->size, gfpflags, node);

	return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_node);

#ifdef CONFIG_TRACING
void *kmem_cache_alloc_node_trace(struct kmem_cache *s,
				    gfp_t gfpflags,
				    int node, size_t size)
{
	void *ret = slab_alloc(s, gfpflags, node, _RET_IP_);

	trace_kmalloc_node(_RET_IP_, ret,
			   size, s->size, gfpflags, node);
	return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_node_trace);
#endif
#endif

/*
 * Slow patch handling. This may still be called frequently since objects
 * have a longer lifetime than the cpu slabs in most processing loads.
 *
 * So we still attempt to reduce cache line usage. Just take the slab
 * lock and free the item. If there is no additional partial page
 * handling required then we can return immediately.
 */
static void __slab_free(struct kmem_cache *s, struct page *page,
			void *x, unsigned long addr)
{
	void *prior;
	void **object = (void *)x;
	int was_frozen;
	int inuse;
	struct page new;
	unsigned long counters;
	struct kmem_cache_node *n = NULL;
	unsigned long uninitialized_var(flags);

	stat(s, FREE_SLOWPATH);

	if (kmem_cache_debug(s) && !free_debug_processing(s, page, x, addr))
		return;

	do {
		prior = page->freelist;
		counters = page->counters;
		set_freepointer(s, object, prior);
		new.counters = counters;
		was_frozen = new.frozen;
		new.inuse--;
		if ((!new.inuse || !prior) && !was_frozen && !n) {

			if (!kmem_cache_debug(s) && !prior)

				/*
				 * Slab was on no list before and will be partially empty
				 * We can defer the list move and instead freeze it.
				 */
				new.frozen = 1;

			else { /* Needs to be taken off a list */

	                        n = get_node(s, page_to_nid(page));
				/*
				 * Speculatively acquire the list_lock.
				 * If the cmpxchg does not succeed then we may
				 * drop the list_lock without any processing.
				 *
				 * Otherwise the list_lock will synchronize with
				 * other processors updating the list of slabs.
				 */
				spin_lock_irqsave(&n->list_lock, flags);

			}
		}
		inuse = new.inuse;

	} while (!cmpxchg_double_slab(s, page,
		prior, counters,
		object, new.counters,
		"__slab_free"));

	if (likely(!n)) {

		/*
		 * If we just froze the page then put it onto the
		 * per cpu partial list.
		 */
		if (new.frozen && !was_frozen)
			put_cpu_partial(s, page, 1);

		/*
		 * The list lock was not taken therefore no list
		 * activity can be necessary.
		 */
                if (was_frozen)
                        stat(s, FREE_FROZEN);
                return;
        }

	/*
	 * was_frozen may have been set after we acquired the list_lock in
	 * an earlier loop. So we need to check it here again.
	 */
	if (was_frozen)
		stat(s, FREE_FROZEN);
	else {
		if (unlikely(!inuse && n->nr_partial > s->min_partial))
                        goto slab_empty;

		/*
		 * Objects left in the slab. If it was not on the partial list before
		 * then add it.
		 */
		if (unlikely(!prior)) {
			remove_full(s, page);
			add_partial(n, page, DEACTIVATE_TO_TAIL);
			stat(s, FREE_ADD_PARTIAL);
		}
	}
	spin_unlock_irqrestore(&n->list_lock, flags);
	return;

slab_empty:
	if (prior) {
		/*
		 * Slab on the partial list.
		 */
		remove_partial(n, page);
		stat(s, FREE_REMOVE_PARTIAL);
	} else
		/* Slab must be on the full list */
		remove_full(s, page);

	spin_unlock_irqrestore(&n->list_lock, flags);
	stat(s, FREE_SLAB);
	discard_slab(s, page);
}

/*
 * Fastpath with forced inlining to produce a kfree and kmem_cache_free that
 * can perform fastpath freeing without additional function calls.
 *
 * The fastpath is only possible if we are freeing to the current cpu slab
 * of this processor. This typically the case if we have just allocated
 * the item before.
 *
 * If fastpath is not possible then fall back to __slab_free where we deal
 * with all sorts of special processing.
 */
static __always_inline void slab_free(struct kmem_cache *s,
			struct page *page, void *x, unsigned long addr)
{
	void **object = (void *)x;
	struct kmem_cache_cpu *c;
	unsigned long tid;

	slab_free_hook(s, x);

redo:
	/*
	 * Determine the currently cpus per cpu slab.
	 * The cpu may change afterward. However that does not matter since
	 * data is retrieved via this pointer. If we are on the same cpu
	 * during the cmpxchg then the free will succedd.
	 */
	c = __this_cpu_ptr(s->cpu_slab);

	tid = c->tid;
	barrier();

	if (likely(page == c->page)) {
		set_freepointer(s, object, c->freelist);

		if (unlikely(!irqsafe_cpu_cmpxchg_double(
				s->cpu_slab->freelist, s->cpu_slab->tid,
				c->freelist, tid,
				object, next_tid(tid)))) {

			note_cmpxchg_failure("slab_free", s, tid);
			goto redo;
		}
		stat(s, FREE_FASTPATH);
	} else
		__slab_free(s, page, x, addr);

}

void kmem_cache_free(struct kmem_cache *s, void *x)
{
	struct page *page;

	page = virt_to_head_page(x);

	slab_free(s, page, x, _RET_IP_);

	trace_kmem_cache_free(_RET_IP_, x);
}
EXPORT_SYMBOL(kmem_cache_free);

/*
 * Object placement in a slab is made very easy because we always start at
 * offset 0. If we tune the size of the object to the alignment then we can
 * get the required alignment by putting one properly sized object after
 * another.
 *
 * Notice that the allocation order determines the sizes of the per cpu
 * caches. Each processor has always one slab available for allocations.
 * Increasing the allocation order reduces the number of times that slabs
 * must be moved on and off the partial lists and is therefore a factor in
 * locking overhead.
 */

/*
 * Mininum / Maximum order of slab pages. This influences locking overhead
 * and slab fragmentation. A higher order reduces the number of partial slabs
 * and increases the number of allocations possible without having to
 * take the list_lock.
 */
static int slub_min_order;
static int slub_max_order = PAGE_ALLOC_COSTLY_ORDER;
static int slub_min_objects;

/*
 * Merge control. If this is set then no merging of slab caches will occur.
 * (Could be removed. This was introduced to pacify the merge skeptics.)
 */
static int slub_nomerge;

/*
 * Calculate the order of allocation given an slab object size.
 *
 * The order of allocation has significant impact on performance and other
 * system components. Generally order 0 allocations should be preferred since
 * order 0 does not cause fragmentation in the page allocator. Larger objects
 * be problematic to put into order 0 slabs because there may be too much
 * unused space left. We go to a higher order if more than 1/16th of the slab
 * would be wasted.
 *
 * In order to reach satisfactory performance we must ensure that a minimum
 * number of objects is in one slab. Otherwise we may generate too much
 * activity on the partial lists which requires taking the list_lock. This is
 * less a concern for large slabs though which are rarely used.
 *
 * slub_max_order specifies the order where we begin to stop considering the
 * number of objects in a slab as critical. If we reach slub_max_order then
 * we try to keep the page order as low as possible. So we accept more waste
 * of space in favor of a small page order.
 *
 * Higher order allocations also allow the placement of more objects in a
 * slab and thereby reduce object handling overhead. If the user has
 * requested a higher mininum order then we start with that one instead of
 * the smallest order which will fit the object.
 */
static inline int slab_order(int size, int min_objects,
				int max_order, int fract_leftover, int reserved)
{
	int order;
	int rem;
	int min_order = slub_min_order;

	if (order_objects(min_order, size, reserved) > MAX_OBJS_PER_PAGE)
		return get_order(size * MAX_OBJS_PER_PAGE) - 1;

	for (order = max(min_order,
				fls(min_objects * size - 1) - PAGE_SHIFT);
			order <= max_order; order++) {

		unsigned long slab_size = PAGE_SIZE << order;

		if (slab_size < min_objects * size + reserved)
			continue;

		rem = (slab_size - reserved) % size;

		if (rem <= slab_size / fract_leftover)
			break;

	}

	return order;
}

static inline int calculate_order(int size, int reserved)
{
	int order;
	int min_objects;
	int fraction;
	int max_objects;

	/*
	 * Attempt to find best configuration for a slab. This
	 * works by first attempting to generate a layout with
	 * the best configuration and backing off gradually.
	 *
	 * First we reduce the acceptable waste in a slab. Then
	 * we reduce the minimum objects required in a slab.
	 */
	min_objects = slub_min_objects;
	if (!min_objects)
		min_objects = 4 * (fls(nr_cpu_ids) + 1);
	max_objects = order_objects(slub_max_order, size, reserved);
	min_objects = min(min_objects, max_objects);

	while (min_objects > 1) {
		fraction = 16;
		while (fraction >= 4) {
			order = slab_order(size, min_objects,
					slub_max_order, fraction, reserved);
			if (order <= slub_max_order)
				return order;
			fraction /= 2;
		}
		min_objects--;
	}

	/*
	 * We were unable to place multiple objects in a slab. Now
	 * lets see if we can place a single object there.
	 */
	order = slab_order(size, 1, slub_max_order, 1, reserved);
	if (order <= slub_max_order)
		return order;

	/*
	 * Doh this slab cannot be placed using slub_max_order.
	 */
	order = slab_order(size, 1, MAX_ORDER, 1, reserved);
	if (order < MAX_ORDER)
		return order;
	return -ENOSYS;
}

/*
 * Figure out what the alignment of the objects will be.
 */
static unsigned long calculate_alignment(unsigned long flags,
		unsigned long align, unsigned long size)
{
	/*
	 * If the user wants hardware cache aligned objects then follow that
	 * suggestion if the object is sufficiently large.
	 *
	 * The hardware cache alignment cannot override the specified
	 * alignment though. If that is greater then use it.
	 */
	if (flags & SLAB_HWCACHE_ALIGN) {
		unsigned long ralign = cache_line_size();
		while (size <= ralign / 2)
			ralign /= 2;
		align = max(align, ralign);
	}

	if (align < ARCH_SLAB_MINALIGN)
		align = ARCH_SLAB_MINALIGN;

	return ALIGN(align, sizeof(void *));
}

static void
init_kmem_cache_node(struct kmem_cache_node *n, struct kmem_cache *s)
{
	n->nr_partial = 0;
	spin_lock_init(&n->list_lock);
	INIT_LIST_HEAD(&n->partial);
#ifdef CONFIG_SLUB_DEBUG
	atomic_long_set(&n->nr_slabs, 0);
	atomic_long_set(&n->total_objects, 0);
	INIT_LIST_HEAD(&n->full);
#endif
}

static inline int alloc_kmem_cache_cpus(struct kmem_cache *s)
{
	BUILD_BUG_ON(PERCPU_DYNAMIC_EARLY_SIZE <
			SLUB_PAGE_SHIFT * sizeof(struct kmem_cache_cpu));

	/*
	 * Must align to double word boundary for the double cmpxchg
	 * instructions to work; see __pcpu_double_call_return_bool().
	 */
	s->cpu_slab = __alloc_percpu(sizeof(struct kmem_cache_cpu),
				     2 * sizeof(void *));

	if (!s->cpu_slab)
		return 0;

	init_kmem_cache_cpus(s);

	return 1;
}

static struct kmem_cache *kmem_cache_node;

/*
 * No kmalloc_node yet so do it by hand. We know that this is the first
 * slab on the node for this slabcache. There are no concurrent accesses
 * possible.
 *
 * Note that this function only works on the kmalloc_node_cache
 * when allocating for the kmalloc_node_cache. This is used for bootstrapping
 * memory on a fresh node that has no slab structures yet.
 */
static void early_kmem_cache_node_alloc(int node)
{
	struct page *page;
	struct kmem_cache_node *n;

	BUG_ON(kmem_cache_node->size < sizeof(struct kmem_cache_node));

	page = new_slab(kmem_cache_node, GFP_NOWAIT, node);

	BUG_ON(!page);
	if (page_to_nid(page) != node) {
		printk(KERN_ERR "SLUB: Unable to allocate memory from "
				"node %d\n", node);
		printk(KERN_ERR "SLUB: Allocating a useless per node structure "
				"in order to be able to continue\n");
	}

	n = page->freelist;
	BUG_ON(!n);
	page->freelist = get_freepointer(kmem_cache_node, n);
	page->inuse = 1;
	page->frozen = 0;
	kmem_cache_node->node[node] = n;
#ifdef CONFIG_SLUB_DEBUG
	init_object(kmem_cache_node, n, SLUB_RED_ACTIVE);
	init_tracking(kmem_cache_node, n);
#endif
	init_kmem_cache_node(n, kmem_cache_node);
	inc_slabs_node(kmem_cache_node, node, page->objects);

	add_partial(n, page, DEACTIVATE_TO_HEAD);
}

static void free_kmem_cache_nodes(struct kmem_cache *s)
{
	int node;

	for_each_node_state(node, N_NORMAL_MEMORY) {
		struct kmem_cache_node *n = s->node[node];

		if (n)
			kmem_cache_free(kmem_cache_node, n);

		s->node[node] = NULL;
	}
}

static int init_kmem_cache_nodes(struct kmem_cache *s)
{
	int node;

	for_each_node_state(node, N_NORMAL_MEMORY) {
		struct kmem_cache_node *n;

		if (slab_state == DOWN) {
			early_kmem_cache_node_alloc(node);
			continue;
		}
		n = kmem_cache_alloc_node(kmem_cache_node,
						GFP_KERNEL, node);

		if (!n) {
			free_kmem_cache_nodes(s);
			return 0;
		}

		s->node[node] = n;
		init_kmem_cache_node(n, s);
	}
	return 1;
}

static void set_min_partial(struct kmem_cache *s, unsigned long min)
{
	if (min < MIN_PARTIAL)
		min = MIN_PARTIAL;
	else if (min > MAX_PARTIAL)
		min = MAX_PARTIAL;
	s->min_partial = min;
}

/*
 * calculate_sizes() determines the order and the distribution of data within
 * a slab object.
 */