Merge branch 'upstream-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/linvil...

[mirror_ubuntu-bionic-kernel.git] / mm / slab.c

/*
 * linux/mm/slab.c
 * Written by Mark Hemment, 1996/97.
 * (markhe@nextd.demon.co.uk)
 *
 * kmem_cache_destroy() + some cleanup - 1999 Andrea Arcangeli
 *
 * Major cleanup, different bufctl logic, per-cpu arrays
 *      (c) 2000 Manfred Spraul
 *
 * Cleanup, make the head arrays unconditional, preparation for NUMA
 *      (c) 2002 Manfred Spraul
 *
 * An implementation of the Slab Allocator as described in outline in;
 *      UNIX Internals: The New Frontiers by Uresh Vahalia
 *      Pub: Prentice Hall      ISBN 0-13-101908-2
 * or with a little more detail in;
 *      The Slab Allocator: An Object-Caching Kernel Memory Allocator
 *      Jeff Bonwick (Sun Microsystems).
 *      Presented at: USENIX Summer 1994 Technical Conference
 *
 * The memory is organized in caches, one cache for each object type.
 * (e.g. inode_cache, dentry_cache, buffer_head, vm_area_struct)
 * Each cache consists out of many slabs (they are small (usually one
 * page long) and always contiguous), and each slab contains multiple
 * initialized objects.
 *
 * This means, that your constructor is used only for newly allocated
 * slabs and you must pass objects with the same intializations to
 * kmem_cache_free.
 *
 * Each cache can only support one memory type (GFP_DMA, GFP_HIGHMEM,
 * normal). If you need a special memory type, then must create a new
 * cache for that memory type.
 *
 * In order to reduce fragmentation, the slabs are sorted in 3 groups:
 *   full slabs with 0 free objects
 *   partial slabs
 *   empty slabs with no allocated objects
 *
 * If partial slabs exist, then new allocations come from these slabs,
 * otherwise from empty slabs or new slabs are allocated.
 *
 * kmem_cache_destroy() CAN CRASH if you try to allocate from the cache
 * during kmem_cache_destroy(). The caller must prevent concurrent allocs.
 *
 * Each cache has a short per-cpu head array, most allocs
 * and frees go into that array, and if that array overflows, then 1/2
 * of the entries in the array are given back into the global cache.
 * The head array is strictly LIFO and should improve the cache hit rates.
 * On SMP, it additionally reduces the spinlock operations.
 *
 * The c_cpuarray may not be read with enabled local interrupts - 
 * it's changed with a smp_call_function().
 *
 * SMP synchronization:
 *  constructors and destructors are called without any locking.
 *  Several members in struct kmem_cache and struct slab never change, they
 *      are accessed without any locking.
 *  The per-cpu arrays are never accessed from the wrong cpu, no locking,
 *      and local interrupts are disabled so slab code is preempt-safe.
 *  The non-constant members are protected with a per-cache irq spinlock.
 *
 * Many thanks to Mark Hemment, who wrote another per-cpu slab patch
 * in 2000 - many ideas in the current implementation are derived from
 * his patch.
 *
 * Further notes from the original documentation:
 *
 * 11 April '97.  Started multi-threading - markhe
 *      The global cache-chain is protected by the mutex 'cache_chain_mutex'.
 *      The sem is only needed when accessing/extending the cache-chain, which
 *      can never happen inside an interrupt (kmem_cache_create(),
 *      kmem_cache_shrink() and kmem_cache_reap()).
 *
 *      At present, each engine can be growing a cache.  This should be blocked.
 *
 * 15 March 2005. NUMA slab allocator.
 *      Shai Fultheim <shai@scalex86.org>.
 *      Shobhit Dayal <shobhit@calsoftinc.com>
 *      Alok N Kataria <alokk@calsoftinc.com>
 *      Christoph Lameter <christoph@lameter.com>
 *
 *      Modified the slab allocator to be node aware on NUMA systems.
 *      Each node has its own list of partial, free and full slabs.
 *      All object allocations for a node occur from node specific slab lists.
 */

#include        <linux/config.h>
#include        <linux/slab.h>
#include        <linux/mm.h>
#include        <linux/swap.h>
#include        <linux/cache.h>
#include        <linux/interrupt.h>
#include        <linux/init.h>
#include        <linux/compiler.h>
#include        <linux/seq_file.h>
#include        <linux/notifier.h>
#include        <linux/kallsyms.h>
#include        <linux/cpu.h>
#include        <linux/sysctl.h>
#include        <linux/module.h>
#include        <linux/rcupdate.h>
#include        <linux/string.h>
#include        <linux/nodemask.h>
#include        <linux/mempolicy.h>
#include        <linux/mutex.h>

#include        <asm/uaccess.h>
#include        <asm/cacheflush.h>
#include        <asm/tlbflush.h>
#include        <asm/page.h>

/*
 * DEBUG        - 1 for kmem_cache_create() to honour; SLAB_DEBUG_INITIAL,
 *                SLAB_RED_ZONE & SLAB_POISON.
 *                0 for faster, smaller code (especially in the critical paths).
 *
 * STATS        - 1 to collect stats for /proc/slabinfo.
 *                0 for faster, smaller code (especially in the critical paths).
 *
 * FORCED_DEBUG - 1 enables SLAB_RED_ZONE and SLAB_POISON (if possible)
 */

#ifdef CONFIG_DEBUG_SLAB
#define DEBUG           1
#define STATS           1
#define FORCED_DEBUG    1
#else
#define DEBUG           0
#define STATS           0
#define FORCED_DEBUG    0
#endif

/* Shouldn't this be in a header file somewhere? */
#define BYTES_PER_WORD          sizeof(void *)

#ifndef cache_line_size
#define cache_line_size()       L1_CACHE_BYTES
#endif

#ifndef ARCH_KMALLOC_MINALIGN
/*
 * Enforce a minimum alignment for the kmalloc caches.
 * Usually, the kmalloc caches are cache_line_size() aligned, except when
 * DEBUG and FORCED_DEBUG are enabled, then they are BYTES_PER_WORD aligned.
 * Some archs want to perform DMA into kmalloc caches and need a guaranteed
 * alignment larger than BYTES_PER_WORD. ARCH_KMALLOC_MINALIGN allows that.
 * Note that this flag disables some debug features.
 */
#define ARCH_KMALLOC_MINALIGN 0
#endif

#ifndef ARCH_SLAB_MINALIGN
/*
 * Enforce a minimum alignment for all caches.
 * Intended for archs that get misalignment faults even for BYTES_PER_WORD
 * aligned buffers. Includes ARCH_KMALLOC_MINALIGN.
 * If possible: Do not enable this flag for CONFIG_DEBUG_SLAB, it disables
 * some debug features.
 */
#define ARCH_SLAB_MINALIGN 0
#endif

#ifndef ARCH_KMALLOC_FLAGS
#define ARCH_KMALLOC_FLAGS SLAB_HWCACHE_ALIGN
#endif

/* Legal flag mask for kmem_cache_create(). */
#if DEBUG
# define CREATE_MASK    (SLAB_DEBUG_INITIAL | SLAB_RED_ZONE | \
                         SLAB_POISON | SLAB_HWCACHE_ALIGN | \
                         SLAB_NO_REAP | SLAB_CACHE_DMA | \
                         SLAB_MUST_HWCACHE_ALIGN | SLAB_STORE_USER | \
                         SLAB_RECLAIM_ACCOUNT | SLAB_PANIC | \
                         SLAB_DESTROY_BY_RCU)
#else
# define CREATE_MASK    (SLAB_HWCACHE_ALIGN | SLAB_NO_REAP | \
                         SLAB_CACHE_DMA | SLAB_MUST_HWCACHE_ALIGN | \
                         SLAB_RECLAIM_ACCOUNT | SLAB_PANIC | \
                         SLAB_DESTROY_BY_RCU)
#endif

/*
 * kmem_bufctl_t:
 *
 * Bufctl's are used for linking objs within a slab
 * linked offsets.
 *
 * This implementation relies on "struct page" for locating the cache &
 * slab an object belongs to.
 * This allows the bufctl structure to be small (one int), but limits
 * the number of objects a slab (not a cache) can contain when off-slab
 * bufctls are used. The limit is the size of the largest general cache
 * that does not use off-slab slabs.
 * For 32bit archs with 4 kB pages, is this 56.
 * This is not serious, as it is only for large objects, when it is unwise
 * to have too many per slab.
 * Note: This limit can be raised by introducing a general cache whose size
 * is less than 512 (PAGE_SIZE<<3), but greater than 256.
 */

typedef unsigned int kmem_bufctl_t;
#define BUFCTL_END      (((kmem_bufctl_t)(~0U))-0)
#define BUFCTL_FREE     (((kmem_bufctl_t)(~0U))-1)
#define SLAB_LIMIT      (((kmem_bufctl_t)(~0U))-2)

/* Max number of objs-per-slab for caches which use off-slab slabs.
 * Needed to avoid a possible looping condition in cache_grow().
 */
static unsigned long offslab_limit;

/*
 * struct slab
 *
 * Manages the objs in a slab. Placed either at the beginning of mem allocated
 * for a slab, or allocated from an general cache.
 * Slabs are chained into three list: fully used, partial, fully free slabs.
 */
struct slab {
        struct list_head list;
        unsigned long colouroff;
        void *s_mem;            /* including colour offset */
        unsigned int inuse;     /* num of objs active in slab */
        kmem_bufctl_t free;
        unsigned short nodeid;
};

/*
 * struct slab_rcu
 *
 * slab_destroy on a SLAB_DESTROY_BY_RCU cache uses this structure to
 * arrange for kmem_freepages to be called via RCU.  This is useful if
 * we need to approach a kernel structure obliquely, from its address
 * obtained without the usual locking.  We can lock the structure to
 * stabilize it and check it's still at the given address, only if we
 * can be sure that the memory has not been meanwhile reused for some
 * other kind of object (which our subsystem's lock might corrupt).
 *
 * rcu_read_lock before reading the address, then rcu_read_unlock after
 * taking the spinlock within the structure expected at that address.
 *
 * We assume struct slab_rcu can overlay struct slab when destroying.
 */
struct slab_rcu {
        struct rcu_head head;
        struct kmem_cache *cachep;
        void *addr;
};

/*
 * struct array_cache
 *
 * Purpose:
 * - LIFO ordering, to hand out cache-warm objects from _alloc
 * - reduce the number of linked list operations
 * - reduce spinlock operations
 *
 * The limit is stored in the per-cpu structure to reduce the data cache
 * footprint.
 *
 */
struct array_cache {
        unsigned int avail;
        unsigned int limit;
        unsigned int batchcount;
        unsigned int touched;
        spinlock_t lock;
        void *entry[0];         /*
                                 * Must have this definition in here for the proper
                                 * alignment of array_cache. Also simplifies accessing
                                 * the entries.
                                 * [0] is for gcc 2.95. It should really be [].
                                 */
};

/* bootstrap: The caches do not work without cpuarrays anymore,
 * but the cpuarrays are allocated from the generic caches...
 */
#define BOOT_CPUCACHE_ENTRIES   1
struct arraycache_init {
        struct array_cache cache;
        void *entries[BOOT_CPUCACHE_ENTRIES];
};

/*
 * The slab lists for all objects.
 */
struct kmem_list3 {
        struct list_head slabs_partial; /* partial list first, better asm code */
        struct list_head slabs_full;
        struct list_head slabs_free;
        unsigned long free_objects;
        unsigned long next_reap;
        int free_touched;
        unsigned int free_limit;
        unsigned int colour_next;       /* Per-node cache coloring */
        spinlock_t list_lock;
        struct array_cache *shared;     /* shared per node */
        struct array_cache **alien;     /* on other nodes */
};

/*
 * Need this for bootstrapping a per node allocator.
 */
#define NUM_INIT_LISTS (2 * MAX_NUMNODES + 1)
struct kmem_list3 __initdata initkmem_list3[NUM_INIT_LISTS];
#define CACHE_CACHE 0
#define SIZE_AC 1
#define SIZE_L3 (1 + MAX_NUMNODES)

/*
 * This function must be completely optimized away if
 * a constant is passed to it. Mostly the same as
 * what is in linux/slab.h except it returns an
 * index.
 */
static __always_inline int index_of(const size_t size)
{
        extern void __bad_size(void);

        if (__builtin_constant_p(size)) {
                int i = 0;

#define CACHE(x) \
        if (size <=x) \
                return i; \
        else \
                i++;
#include "linux/kmalloc_sizes.h"
#undef CACHE
                __bad_size();
        } else
                __bad_size();
        return 0;
}

#define INDEX_AC index_of(sizeof(struct arraycache_init))
#define INDEX_L3 index_of(sizeof(struct kmem_list3))

static void kmem_list3_init(struct kmem_list3 *parent)
{
        INIT_LIST_HEAD(&parent->slabs_full);
        INIT_LIST_HEAD(&parent->slabs_partial);
        INIT_LIST_HEAD(&parent->slabs_free);
        parent->shared = NULL;
        parent->alien = NULL;
        parent->colour_next = 0;
        spin_lock_init(&parent->list_lock);
        parent->free_objects = 0;
        parent->free_touched = 0;
}

#define MAKE_LIST(cachep, listp, slab, nodeid)  \
        do {    \
                INIT_LIST_HEAD(listp);          \
                list_splice(&(cachep->nodelists[nodeid]->slab), listp); \
        } while (0)

#define MAKE_ALL_LISTS(cachep, ptr, nodeid)                     \
        do {                                    \
        MAKE_LIST((cachep), (&(ptr)->slabs_full), slabs_full, nodeid);  \
        MAKE_LIST((cachep), (&(ptr)->slabs_partial), slabs_partial, nodeid); \
        MAKE_LIST((cachep), (&(ptr)->slabs_free), slabs_free, nodeid);  \
        } while (0)

/*
 * struct kmem_cache
 *
 * manages a cache.
 */

struct kmem_cache {
/* 1) per-cpu data, touched during every alloc/free */
        struct array_cache *array[NR_CPUS];
        unsigned int batchcount;
        unsigned int limit;
        unsigned int shared;
        unsigned int buffer_size;
/* 2) touched by every alloc & free from the backend */
        struct kmem_list3 *nodelists[MAX_NUMNODES];
        unsigned int flags;     /* constant flags */
        unsigned int num;       /* # of objs per slab */
        spinlock_t spinlock;

/* 3) cache_grow/shrink */
        /* order of pgs per slab (2^n) */
        unsigned int gfporder;

        /* force GFP flags, e.g. GFP_DMA */
        gfp_t gfpflags;

        size_t colour;          /* cache colouring range */
        unsigned int colour_off;        /* colour offset */
        struct kmem_cache *slabp_cache;
        unsigned int slab_size;
        unsigned int dflags;    /* dynamic flags */

        /* constructor func */
        void (*ctor) (void *, struct kmem_cache *, unsigned long);

        /* de-constructor func */
        void (*dtor) (void *, struct kmem_cache *, unsigned long);

/* 4) cache creation/removal */
        const char *name;
        struct list_head next;

/* 5) statistics */
#if STATS
        unsigned long num_active;
        unsigned long num_allocations;
        unsigned long high_mark;
        unsigned long grown;
        unsigned long reaped;
        unsigned long errors;
        unsigned long max_freeable;
        unsigned long node_allocs;
        unsigned long node_frees;
        atomic_t allochit;
        atomic_t allocmiss;
        atomic_t freehit;
        atomic_t freemiss;
#endif
#if DEBUG
        /*
         * If debugging is enabled, then the allocator can add additional
         * fields and/or padding to every object. buffer_size contains the total
         * object size including these internal fields, the following two
         * variables contain the offset to the user object and its size.
         */
        int obj_offset;
        int obj_size;
#endif
};

#define CFLGS_OFF_SLAB          (0x80000000UL)
#define OFF_SLAB(x)     ((x)->flags & CFLGS_OFF_SLAB)

#define BATCHREFILL_LIMIT       16
/* Optimization question: fewer reaps means less 
 * probability for unnessary cpucache drain/refill cycles.
 *
 * OTOH the cpuarrays can contain lots of objects,
 * which could lock up otherwise freeable slabs.
 */
#define REAPTIMEOUT_CPUC        (2*HZ)
#define REAPTIMEOUT_LIST3       (4*HZ)

#if STATS
#define STATS_INC_ACTIVE(x)     ((x)->num_active++)
#define STATS_DEC_ACTIVE(x)     ((x)->num_active--)
#define STATS_INC_ALLOCED(x)    ((x)->num_allocations++)
#define STATS_INC_GROWN(x)      ((x)->grown++)
#define STATS_INC_REAPED(x)     ((x)->reaped++)
#define STATS_SET_HIGH(x)       do { if ((x)->num_active > (x)->high_mark) \
                                        (x)->high_mark = (x)->num_active; \
                                } while (0)
#define STATS_INC_ERR(x)        ((x)->errors++)
#define STATS_INC_NODEALLOCS(x) ((x)->node_allocs++)
#define STATS_INC_NODEFREES(x)  ((x)->node_frees++)
#define STATS_SET_FREEABLE(x, i) \
                                do { if ((x)->max_freeable < i) \
                                        (x)->max_freeable = i; \
                                } while (0)

#define STATS_INC_ALLOCHIT(x)   atomic_inc(&(x)->allochit)
#define STATS_INC_ALLOCMISS(x)  atomic_inc(&(x)->allocmiss)
#define STATS_INC_FREEHIT(x)    atomic_inc(&(x)->freehit)
#define STATS_INC_FREEMISS(x)   atomic_inc(&(x)->freemiss)
#else
#define STATS_INC_ACTIVE(x)     do { } while (0)
#define STATS_DEC_ACTIVE(x)     do { } while (0)
#define STATS_INC_ALLOCED(x)    do { } while (0)
#define STATS_INC_GROWN(x)      do { } while (0)
#define STATS_INC_REAPED(x)     do { } while (0)
#define STATS_SET_HIGH(x)       do { } while (0)
#define STATS_INC_ERR(x)        do { } while (0)
#define STATS_INC_NODEALLOCS(x) do { } while (0)
#define STATS_INC_NODEFREES(x)  do { } while (0)
#define STATS_SET_FREEABLE(x, i) \
                                do { } while (0)

#define STATS_INC_ALLOCHIT(x)   do { } while (0)
#define STATS_INC_ALLOCMISS(x)  do { } while (0)
#define STATS_INC_FREEHIT(x)    do { } while (0)
#define STATS_INC_FREEMISS(x)   do { } while (0)
#endif

#if DEBUG
/* Magic nums for obj red zoning.
 * Placed in the first word before and the first word after an obj.
 */
#define RED_INACTIVE    0x5A2CF071UL    /* when obj is inactive */
#define RED_ACTIVE      0x170FC2A5UL    /* when obj is active */

/* ...and for poisoning */
#define POISON_INUSE    0x5a    /* for use-uninitialised poisoning */
#define POISON_FREE     0x6b    /* for use-after-free poisoning */
#define POISON_END      0xa5    /* end-byte of poisoning */

/* memory layout of objects:
 * 0            : objp
 * 0 .. cachep->obj_offset - BYTES_PER_WORD - 1: padding. This ensures that
 *              the end of an object is aligned with the end of the real
 *              allocation. Catches writes behind the end of the allocation.
 * cachep->obj_offset - BYTES_PER_WORD .. cachep->obj_offset - 1:
 *              redzone word.
 * cachep->obj_offset: The real object.
 * cachep->buffer_size - 2* BYTES_PER_WORD: redzone word [BYTES_PER_WORD long]
 * cachep->buffer_size - 1* BYTES_PER_WORD: last caller address [BYTES_PER_WORD long]
 */
static int obj_offset(struct kmem_cache *cachep)
{
        return cachep->obj_offset;
}

static int obj_size(struct kmem_cache *cachep)
{
        return cachep->obj_size;
}

static unsigned long *dbg_redzone1(struct kmem_cache *cachep, void *objp)
{
        BUG_ON(!(cachep->flags & SLAB_RED_ZONE));
        return (unsigned long*) (objp+obj_offset(cachep)-BYTES_PER_WORD);
}

static unsigned long *dbg_redzone2(struct kmem_cache *cachep, void *objp)
{
        BUG_ON(!(cachep->flags & SLAB_RED_ZONE));
        if (cachep->flags & SLAB_STORE_USER)
                return (unsigned long *)(objp + cachep->buffer_size -
                                         2 * BYTES_PER_WORD);
        return (unsigned long *)(objp + cachep->buffer_size - BYTES_PER_WORD);
}

static void **dbg_userword(struct kmem_cache *cachep, void *objp)
{
        BUG_ON(!(cachep->flags & SLAB_STORE_USER));
        return (void **)(objp + cachep->buffer_size - BYTES_PER_WORD);
}

#else

#define obj_offset(x)                   0
#define obj_size(cachep)                (cachep->buffer_size)
#define dbg_redzone1(cachep, objp)      ({BUG(); (unsigned long *)NULL;})
#define dbg_redzone2(cachep, objp)      ({BUG(); (unsigned long *)NULL;})
#define dbg_userword(cachep, objp)      ({BUG(); (void **)NULL;})

#endif

/*
 * Maximum size of an obj (in 2^order pages)
 * and absolute limit for the gfp order.
 */
#if defined(CONFIG_LARGE_ALLOCS)
#define MAX_OBJ_ORDER   13      /* up to 32Mb */
#define MAX_GFP_ORDER   13      /* up to 32Mb */
#elif defined(CONFIG_MMU)
#define MAX_OBJ_ORDER   5       /* 32 pages */
#define MAX_GFP_ORDER   5       /* 32 pages */
#else
#define MAX_OBJ_ORDER   8       /* up to 1Mb */
#define MAX_GFP_ORDER   8       /* up to 1Mb */
#endif

/*
 * Do not go above this order unless 0 objects fit into the slab.
 */
#define BREAK_GFP_ORDER_HI      1
#define BREAK_GFP_ORDER_LO      0
static int slab_break_gfp_order = BREAK_GFP_ORDER_LO;

/* Functions for storing/retrieving the cachep and or slab from the
 * global 'mem_map'. These are used to find the slab an obj belongs to.
 * With kfree(), these are used to find the cache which an obj belongs to.
 */
static inline void page_set_cache(struct page *page, struct kmem_cache *cache)
{
        page->lru.next = (struct list_head *)cache;
}

static inline struct kmem_cache *page_get_cache(struct page *page)
{
        return (struct kmem_cache *)page->lru.next;
}

static inline void page_set_slab(struct page *page, struct slab *slab)
{
        page->lru.prev = (struct list_head *)slab;
}

static inline struct slab *page_get_slab(struct page *page)
{
        return (struct slab *)page->lru.prev;
}

static inline struct kmem_cache *virt_to_cache(const void *obj)
{
        struct page *page = virt_to_page(obj);
        return page_get_cache(page);
}

static inline struct slab *virt_to_slab(const void *obj)
{
        struct page *page = virt_to_page(obj);
        return page_get_slab(page);
}

/* These are the default caches for kmalloc. Custom caches can have other sizes. */
struct cache_sizes malloc_sizes[] = {
#define CACHE(x) { .cs_size = (x) },
#include <linux/kmalloc_sizes.h>
        CACHE(ULONG_MAX)
#undef CACHE
};
EXPORT_SYMBOL(malloc_sizes);

/* Must match cache_sizes above. Out of line to keep cache footprint low. */
struct cache_names {
        char *name;
        char *name_dma;
};

static struct cache_names __initdata cache_names[] = {
#define CACHE(x) { .name = "size-" #x, .name_dma = "size-" #x "(DMA)" },
#include <linux/kmalloc_sizes.h>
        {NULL,}
#undef CACHE
};

static struct arraycache_init initarray_cache __initdata =
    { {0, BOOT_CPUCACHE_ENTRIES, 1, 0} };
static struct arraycache_init initarray_generic =
    { {0, BOOT_CPUCACHE_ENTRIES, 1, 0} };

/* internal cache of cache description objs */
static struct kmem_cache cache_cache = {
        .batchcount = 1,
        .limit = BOOT_CPUCACHE_ENTRIES,
        .shared = 1,
        .buffer_size = sizeof(struct kmem_cache),
        .flags = SLAB_NO_REAP,
        .spinlock = SPIN_LOCK_UNLOCKED,
        .name = "kmem_cache",
#if DEBUG
        .obj_size = sizeof(struct kmem_cache),
#endif
};

/* Guard access to the cache-chain. */
static DEFINE_MUTEX(cache_chain_mutex);
static struct list_head cache_chain;

/*
 * vm_enough_memory() looks at this to determine how many
 * slab-allocated pages are possibly freeable under pressure
 *
 * SLAB_RECLAIM_ACCOUNT turns this on per-slab
 */
atomic_t slab_reclaim_pages;

/*
 * chicken and egg problem: delay the per-cpu array allocation
 * until the general caches are up.
 */
static enum {
        NONE,
        PARTIAL_AC,
        PARTIAL_L3,
        FULL
} g_cpucache_up;

static DEFINE_PER_CPU(struct work_struct, reap_work);

static void free_block(struct kmem_cache *cachep, void **objpp, int len, int node);
static void enable_cpucache(struct kmem_cache *cachep);
static void cache_reap(void *unused);
static int __node_shrink(struct kmem_cache *cachep, int node);

static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
{
        return cachep->array[smp_processor_id()];
}

static inline struct kmem_cache *__find_general_cachep(size_t size, gfp_t gfpflags)
{
        struct cache_sizes *csizep = malloc_sizes;

#if DEBUG
        /* This happens if someone tries to call
         * kmem_cache_create(), or __kmalloc(), before
         * the generic caches are initialized.
         */
        BUG_ON(malloc_sizes[INDEX_AC].cs_cachep == NULL);
#endif
        while (size > csizep->cs_size)
                csizep++;

        /*
         * Really subtle: The last entry with cs->cs_size==ULONG_MAX
         * has cs_{dma,}cachep==NULL. Thus no special case
         * for large kmalloc calls required.
         */
        if (unlikely(gfpflags & GFP_DMA))
                return csizep->cs_dmacachep;
        return csizep->cs_cachep;
}

struct kmem_cache *kmem_find_general_cachep(size_t size, gfp_t gfpflags)
{
        return __find_general_cachep(size, gfpflags);
}
EXPORT_SYMBOL(kmem_find_general_cachep);

static size_t slab_mgmt_size(size_t nr_objs, size_t align)
{
        return ALIGN(sizeof(struct slab)+nr_objs*sizeof(kmem_bufctl_t), align);
}

/* Calculate the number of objects and left-over bytes for a given
   buffer size. */
static void cache_estimate(unsigned long gfporder, size_t buffer_size,
                           size_t align, int flags, size_t *left_over,
                           unsigned int *num)
{
        int nr_objs;
        size_t mgmt_size;
        size_t slab_size = PAGE_SIZE << gfporder;

        /*
         * The slab management structure can be either off the slab or
         * on it. For the latter case, the memory allocated for a
         * slab is used for:
         *
         * - The struct slab
         * - One kmem_bufctl_t for each object
         * - Padding to respect alignment of @align
         * - @buffer_size bytes for each object
         *
         * If the slab management structure is off the slab, then the
         * alignment will already be calculated into the size. Because
         * the slabs are all pages aligned, the objects will be at the
         * correct alignment when allocated.
         */
        if (flags & CFLGS_OFF_SLAB) {
                mgmt_size = 0;
                nr_objs = slab_size / buffer_size;

                if (nr_objs > SLAB_LIMIT)
                        nr_objs = SLAB_LIMIT;
        } else {
                /*
                 * Ignore padding for the initial guess. The padding
                 * is at most @align-1 bytes, and @buffer_size is at
                 * least @align. In the worst case, this result will
                 * be one greater than the number of objects that fit
                 * into the memory allocation when taking the padding
                 * into account.
                 */
                nr_objs = (slab_size - sizeof(struct slab)) /
                          (buffer_size + sizeof(kmem_bufctl_t));

                /*
                 * This calculated number will be either the right
                 * amount, or one greater than what we want.
                 */
                if (slab_mgmt_size(nr_objs, align) + nr_objs*buffer_size
                       > slab_size)
                        nr_objs--;

                if (nr_objs > SLAB_LIMIT)
                        nr_objs = SLAB_LIMIT;

                mgmt_size = slab_mgmt_size(nr_objs, align);
        }
        *num = nr_objs;
        *left_over = slab_size - nr_objs*buffer_size - mgmt_size;
}

#define slab_error(cachep, msg) __slab_error(__FUNCTION__, cachep, msg)

static void __slab_error(const char *function, struct kmem_cache *cachep, char *msg)
{
        printk(KERN_ERR "slab error in %s(): cache `%s': %s\n",
               function, cachep->name, msg);
        dump_stack();
}

/*
 * Initiate the reap timer running on the target CPU.  We run at around 1 to 2Hz
 * via the workqueue/eventd.
 * Add the CPU number into the expiration time to minimize the possibility of
 * the CPUs getting into lockstep and contending for the global cache chain
 * lock.
 */
static void __devinit start_cpu_timer(int cpu)
{
        struct work_struct *reap_work = &per_cpu(reap_work, cpu);

        /*
         * When this gets called from do_initcalls via cpucache_init(),
         * init_workqueues() has already run, so keventd will be setup
         * at that time.
         */
        if (keventd_up() && reap_work->func == NULL) {
                INIT_WORK(reap_work, cache_reap, NULL);
                schedule_delayed_work_on(cpu, reap_work, HZ + 3 * cpu);
        }
}

static struct array_cache *alloc_arraycache(int node, int entries,
                                            int batchcount)
{
        int memsize = sizeof(void *) * entries + sizeof(struct array_cache);
        struct array_cache *nc = NULL;

        nc = kmalloc_node(memsize, GFP_KERNEL, node);
        if (nc) {
                nc->avail = 0;
                nc->limit = entries;
                nc->batchcount = batchcount;
                nc->touched = 0;
                spin_lock_init(&nc->lock);
        }
        return nc;
}

#ifdef CONFIG_NUMA
static void *__cache_alloc_node(struct kmem_cache *, gfp_t, int);

static struct array_cache **alloc_alien_cache(int node, int limit)
{
        struct array_cache **ac_ptr;
        int memsize = sizeof(void *) * MAX_NUMNODES;
        int i;

        if (limit > 1)
                limit = 12;
        ac_ptr = kmalloc_node(memsize, GFP_KERNEL, node);
        if (ac_ptr) {
                for_each_node(i) {
                        if (i == node || !node_online(i)) {
                                ac_ptr[i] = NULL;
                                continue;
                        }
                        ac_ptr[i] = alloc_arraycache(node, limit, 0xbaadf00d);
                        if (!ac_ptr[i]) {
                                for (i--; i <= 0; i--)
                                        kfree(ac_ptr[i]);
                                kfree(ac_ptr);
                                return NULL;
                        }
                }
        }
        return ac_ptr;
}

static void free_alien_cache(struct array_cache **ac_ptr)
{
        int i;

        if (!ac_ptr)
                return;

        for_each_node(i)
            kfree(ac_ptr[i]);

        kfree(ac_ptr);
}

static void __drain_alien_cache(struct kmem_cache *cachep,
                                struct array_cache *ac, int node)
{
        struct kmem_list3 *rl3 = cachep->nodelists[node];

        if (ac->avail) {
                spin_lock(&rl3->list_lock);
                free_block(cachep, ac->entry, ac->avail, node);
                ac->avail = 0;
                spin_unlock(&rl3->list_lock);
        }
}

static void drain_alien_cache(struct kmem_cache *cachep, struct array_cache **alien)
{
        int i = 0;
        struct array_cache *ac;
        unsigned long flags;

        for_each_online_node(i) {
                ac = alien[i];
                if (ac) {
                        spin_lock_irqsave(&ac->lock, flags);
                        __drain_alien_cache(cachep, ac, i);
                        spin_unlock_irqrestore(&ac->lock, flags);
                }
        }
}
#else

#define drain_alien_cache(cachep, alien) do { } while (0)

static inline struct array_cache **alloc_alien_cache(int node, int limit)
{
        return (struct array_cache **) 0x01020304ul;
}

static inline void free_alien_cache(struct array_cache **ac_ptr)
{
}

#endif

static int __devinit cpuup_callback(struct notifier_block *nfb,
                                    unsigned long action, void *hcpu)
{
        long cpu = (long)hcpu;
        struct kmem_cache *cachep;
        struct kmem_list3 *l3 = NULL;
        int node = cpu_to_node(cpu);
        int memsize = sizeof(struct kmem_list3);

        switch (action) {
        case CPU_UP_PREPARE:
                mutex_lock(&cache_chain_mutex);
                /* we need to do this right in the beginning since
                 * alloc_arraycache's are going to use this list.
                 * kmalloc_node allows us to add the slab to the right
                 * kmem_list3 and not this cpu's kmem_list3
                 */

                list_for_each_entry(cachep, &cache_chain, next) {
                        /* setup the size64 kmemlist for cpu before we can
                         * begin anything. Make sure some other cpu on this
                         * node has not already allocated this
                         */
                        if (!cachep->nodelists[node]) {
                                if (!(l3 = kmalloc_node(memsize,
                                                        GFP_KERNEL, node)))
                                        goto bad;
                                kmem_list3_init(l3);
                                l3->next_reap = jiffies + REAPTIMEOUT_LIST3 +
                                    ((unsigned long)cachep) % REAPTIMEOUT_LIST3;

                                /*
                                 * The l3s don't come and go as CPUs come and
                                 * go.  cache_chain_mutex is sufficient
                                 * protection here.
                                 */
                                cachep->nodelists[node] = l3;
                        }

                        spin_lock_irq(&cachep->nodelists[node]->list_lock);
                        cachep->nodelists[node]->free_limit =
                            (1 + nr_cpus_node(node)) *
                            cachep->batchcount + cachep->num;
                        spin_unlock_irq(&cachep->nodelists[node]->list_lock);
                }

                /* Now we can go ahead with allocating the shared array's
                   & array cache's */
                list_for_each_entry(cachep, &cache_chain, next) {
                        struct array_cache *nc;
                        struct array_cache *shared;
                        struct array_cache **alien;

                        nc = alloc_arraycache(node, cachep->limit,
                                                cachep->batchcount);
                        if (!nc)
                                goto bad;
                        shared = alloc_arraycache(node,
                                        cachep->shared * cachep->batchcount,
                                        0xbaadf00d);
                        if (!shared)
                                goto bad;

                        alien = alloc_alien_cache(node, cachep->limit);
                        if (!alien)
                                goto bad;
                        cachep->array[cpu] = nc;

                        l3 = cachep->nodelists[node];
                        BUG_ON(!l3);

                        spin_lock_irq(&l3->list_lock);
                        if (!l3->shared) {
                                /*
                                 * We are serialised from CPU_DEAD or
                                 * CPU_UP_CANCELLED by the cpucontrol lock
                                 */
                                l3->shared = shared;
                                shared = NULL;
                        }
#ifdef CONFIG_NUMA
                        if (!l3->alien) {
                                l3->alien = alien;
                                alien = NULL;
                        }
#endif
                        spin_unlock_irq(&l3->list_lock);

                        kfree(shared);
                        free_alien_cache(alien);
                }
                mutex_unlock(&cache_chain_mutex);
                break;
        case CPU_ONLINE:
                start_cpu_timer(cpu);
                break;
#ifdef CONFIG_HOTPLUG_CPU
        case CPU_DEAD:
                /*
                 * Even if all the cpus of a node are down, we don't free the
                 * kmem_list3 of any cache. This to avoid a race between
                 * cpu_down, and a kmalloc allocation from another cpu for
                 * memory from the node of the cpu going down.  The list3
                 * structure is usually allocated from kmem_cache_create() and
                 * gets destroyed at kmem_cache_destroy().
                 */
                /* fall thru */
        case CPU_UP_CANCELED:
                mutex_lock(&cache_chain_mutex);

                list_for_each_entry(cachep, &cache_chain, next) {
                        struct array_cache *nc;
                        struct array_cache *shared;
                        struct array_cache **alien;
                        cpumask_t mask;

                        mask = node_to_cpumask(node);
                        /* cpu is dead; no one can alloc from it. */
                        nc = cachep->array[cpu];
                        cachep->array[cpu] = NULL;
                        l3 = cachep->nodelists[node];

                        if (!l3)
                                goto free_array_cache;

                        spin_lock_irq(&l3->list_lock);

                        /* Free limit for this kmem_list3 */
                        l3->free_limit -= cachep->batchcount;
                        if (nc)
                                free_block(cachep, nc->entry, nc->avail, node);

                        if (!cpus_empty(mask)) {
                                spin_unlock_irq(&l3->list_lock);
                                goto free_array_cache;
                        }

                        shared = l3->shared;
                        if (shared) {
                                free_block(cachep, l3->shared->entry,
                                           l3->shared->avail, node);
                                l3->shared = NULL;
                        }

                        alien = l3->alien;
                        l3->alien = NULL;

                        spin_unlock_irq(&l3->list_lock);

                        kfree(shared);
                        if (alien) {
                                drain_alien_cache(cachep, alien);
                                free_alien_cache(alien);
                        }
free_array_cache:
                        kfree(nc);
                }
                /*
                 * In the previous loop, all the objects were freed to
                 * the respective cache's slabs,  now we can go ahead and
                 * shrink each nodelist to its limit.
                 */
                list_for_each_entry(cachep, &cache_chain, next) {
                        l3 = cachep->nodelists[node];
                        if (!l3)
                                continue;
                        spin_lock_irq(&l3->list_lock);
                        /* free slabs belonging to this node */
                        __node_shrink(cachep, node);
                        spin_unlock_irq(&l3->list_lock);
                }
                mutex_unlock(&cache_chain_mutex);
                break;
#endif
        }
        return NOTIFY_OK;
      bad:
        mutex_unlock(&cache_chain_mutex);
        return NOTIFY_BAD;
}

static struct notifier_block cpucache_notifier = { &cpuup_callback, NULL, 0 };

/*
 * swap the static kmem_list3 with kmalloced memory
 */
static void init_list(struct kmem_cache *cachep, struct kmem_list3 *list, int nodeid)
{
        struct kmem_list3 *ptr;

        BUG_ON(cachep->nodelists[nodeid] != list);
        ptr = kmalloc_node(sizeof(struct kmem_list3), GFP_KERNEL, nodeid);
        BUG_ON(!ptr);

        local_irq_disable();
        memcpy(ptr, list, sizeof(struct kmem_list3));
        MAKE_ALL_LISTS(cachep, ptr, nodeid);
        cachep->nodelists[nodeid] = ptr;
        local_irq_enable();
}

/* Initialisation.
 * Called after the gfp() functions have been enabled, and before smp_init().
 */
void __init kmem_cache_init(void)
{
        size_t left_over;
        struct cache_sizes *sizes;
        struct cache_names *names;
        int i;

        for (i = 0; i < NUM_INIT_LISTS; i++) {
                kmem_list3_init(&initkmem_list3[i]);
                if (i < MAX_NUMNODES)
                        cache_cache.nodelists[i] = NULL;
        }

        /*
         * Fragmentation resistance on low memory - only use bigger
         * page orders on machines with more than 32MB of memory.
         */
        if (num_physpages > (32 << 20) >> PAGE_SHIFT)
                slab_break_gfp_order = BREAK_GFP_ORDER_HI;

        /* Bootstrap is tricky, because several objects are allocated
         * from caches that do not exist yet:
         * 1) initialize the cache_cache cache: it contains the struct kmem_cache
         *    structures of all caches, except cache_cache itself: cache_cache
         *    is statically allocated.
         *    Initially an __init data area is used for the head array and the
         *    kmem_list3 structures, it's replaced with a kmalloc allocated
         *    array at the end of the bootstrap.
         * 2) Create the first kmalloc cache.
         *    The struct kmem_cache for the new cache is allocated normally.
         *    An __init data area is used for the head array.
         * 3) Create the remaining kmalloc caches, with minimally sized
         *    head arrays.
         * 4) Replace the __init data head arrays for cache_cache and the first
         *    kmalloc cache with kmalloc allocated arrays.
         * 5) Replace the __init data for kmem_list3 for cache_cache and
         *    the other cache's with kmalloc allocated memory.
         * 6) Resize the head arrays of the kmalloc caches to their final sizes.
         */

        /* 1) create the cache_cache */
        INIT_LIST_HEAD(&cache_chain);
        list_add(&cache_cache.next, &cache_chain);
        cache_cache.colour_off = cache_line_size();
        cache_cache.array[smp_processor_id()] = &initarray_cache.cache;
        cache_cache.nodelists[numa_node_id()] = &initkmem_list3[CACHE_CACHE];

        cache_cache.buffer_size = ALIGN(cache_cache.buffer_size, cache_line_size());

        cache_estimate(0, cache_cache.buffer_size, cache_line_size(), 0,
                       &left_over, &cache_cache.num);
        if (!cache_cache.num)
                BUG();

        cache_cache.colour = left_over / cache_cache.colour_off;
        cache_cache.slab_size = ALIGN(cache_cache.num * sizeof(kmem_bufctl_t) +
                                      sizeof(struct slab), cache_line_size());

        /* 2+3) create the kmalloc caches */
        sizes = malloc_sizes;
        names = cache_names;

        /* Initialize the caches that provide memory for the array cache
         * and the kmem_list3 structures first.
         * Without this, further allocations will bug
         */

        sizes[INDEX_AC].cs_cachep = kmem_cache_create(names[INDEX_AC].name,
                                                      sizes[INDEX_AC].cs_size,
                                                      ARCH_KMALLOC_MINALIGN,
                                                      (ARCH_KMALLOC_FLAGS |
                                                       SLAB_PANIC), NULL, NULL);

        if (INDEX_AC != INDEX_L3)
                sizes[INDEX_L3].cs_cachep =
                    kmem_cache_create(names[INDEX_L3].name,
                                      sizes[INDEX_L3].cs_size,
                                      ARCH_KMALLOC_MINALIGN,
                                      (ARCH_KMALLOC_FLAGS | SLAB_PANIC), NULL,
                                      NULL);

        while (sizes->cs_size != ULONG_MAX) {
                /*
                 * For performance, all the general caches are L1 aligned.
                 * This should be particularly beneficial on SMP boxes, as it
                 * eliminates "false sharing".
                 * Note for systems short on memory removing the alignment will
                 * allow tighter packing of the smaller caches.
                 */
                if (!sizes->cs_cachep)
                        sizes->cs_cachep = kmem_cache_create(names->name,
                                                             sizes->cs_size,
                                                             ARCH_KMALLOC_MINALIGN,
                                                             (ARCH_KMALLOC_FLAGS
                                                              | SLAB_PANIC),
                                                             NULL, NULL);

                /* Inc off-slab bufctl limit until the ceiling is hit. */
                if (!(OFF_SLAB(sizes->cs_cachep))) {
                        offslab_limit = sizes->cs_size - sizeof(struct slab);
                        offslab_limit /= sizeof(kmem_bufctl_t);
                }

                sizes->cs_dmacachep = kmem_cache_create(names->name_dma,
                                                        sizes->cs_size,
                                                        ARCH_KMALLOC_MINALIGN,
                                                        (ARCH_KMALLOC_FLAGS |
                                                         SLAB_CACHE_DMA |
                                                         SLAB_PANIC), NULL,
                                                        NULL);

                sizes++;
                names++;
        }
        /* 4) Replace the bootstrap head arrays */
        {
                void *ptr;

                ptr = kmalloc(sizeof(struct arraycache_init), GFP_KERNEL);

                local_irq_disable();
                BUG_ON(cpu_cache_get(&cache_cache) != &initarray_cache.cache);
                memcpy(ptr, cpu_cache_get(&cache_cache),
                       sizeof(struct arraycache_init));
                cache_cache.array[smp_processor_id()] = ptr;
                local_irq_enable();

                ptr = kmalloc(sizeof(struct arraycache_init), GFP_KERNEL);

                local_irq_disable();
                BUG_ON(cpu_cache_get(malloc_sizes[INDEX_AC].cs_cachep)
                       != &initarray_generic.cache);
                memcpy(ptr, cpu_cache_get(malloc_sizes[INDEX_AC].cs_cachep),
                       sizeof(struct arraycache_init));
                malloc_sizes[INDEX_AC].cs_cachep->array[smp_processor_id()] =
                    ptr;
                local_irq_enable();
        }
        /* 5) Replace the bootstrap kmem_list3's */
        {
                int node;
                /* Replace the static kmem_list3 structures for the boot cpu */
                init_list(&cache_cache, &initkmem_list3[CACHE_CACHE],
                          numa_node_id());

                for_each_online_node(node) {
                        init_list(malloc_sizes[INDEX_AC].cs_cachep,
                                  &initkmem_list3[SIZE_AC + node], node);

                        if (INDEX_AC != INDEX_L3) {
                                init_list(malloc_sizes[INDEX_L3].cs_cachep,
                                          &initkmem_list3[SIZE_L3 + node],
                                          node);
                        }
                }
        }

        /* 6) resize the head arrays to their final sizes */
        {
                struct kmem_cache *cachep;
                mutex_lock(&cache_chain_mutex);
                list_for_each_entry(cachep, &cache_chain, next)
                    enable_cpucache(cachep);
                mutex_unlock(&cache_chain_mutex);
        }

        /* Done! */
        g_cpucache_up = FULL;

        /* Register a cpu startup notifier callback
         * that initializes cpu_cache_get for all new cpus
         */
        register_cpu_notifier(&cpucache_notifier);

        /* The reap timers are started later, with a module init call:
         * That part of the kernel is not yet operational.
         */
}

static int __init cpucache_init(void)
{
        int cpu;

        /* 
         * Register the timers that return unneeded
         * pages to gfp.
         */
        for_each_online_cpu(cpu)
            start_cpu_timer(cpu);

        return 0;
}

__initcall(cpucache_init);

/*
 * Interface to system's page allocator. No need to hold the cache-lock.
 *
 * If we requested dmaable memory, we will get it. Even if we
 * did not request dmaable memory, we might get it, but that
 * would be relatively rare and ignorable.
 */
static void *kmem_getpages(struct kmem_cache *cachep, gfp_t flags, int nodeid)
{
        struct page *page;
        void *addr;
        int i;

        flags |= cachep->gfpflags;
        page = alloc_pages_node(nodeid, flags, cachep->gfporder);
        if (!page)
                return NULL;
        addr = page_address(page);

        i = (1 << cachep->gfporder);
        if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
                atomic_add(i, &slab_reclaim_pages);
        add_page_state(nr_slab, i);
        while (i--) {
                SetPageSlab(page);
                page++;
        }
        return addr;
}

/*
 * Interface to system's page release.
 */
static void kmem_freepages(struct kmem_cache *cachep, void *addr)
{
        unsigned long i = (1 << cachep->gfporder);
        struct page *page = virt_to_page(addr);
        const unsigned long nr_freed = i;

        while (i--) {
                if (!TestClearPageSlab(page))
                        BUG();
                page++;
        }
        sub_page_state(nr_slab, nr_freed);
        if (current->reclaim_state)
                current->reclaim_state->reclaimed_slab += nr_freed;
        free_pages((unsigned long)addr, cachep->gfporder);
        if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
                atomic_sub(1 << cachep->gfporder, &slab_reclaim_pages);
}

static void kmem_rcu_free(struct rcu_head *head)
{
        struct slab_rcu *slab_rcu = (struct slab_rcu *)head;
        struct kmem_cache *cachep = slab_rcu->cachep;

        kmem_freepages(cachep, slab_rcu->addr);
        if (OFF_SLAB(cachep))
                kmem_cache_free(cachep->slabp_cache, slab_rcu);
}

#if DEBUG

#ifdef CONFIG_DEBUG_PAGEALLOC
static void store_stackinfo(struct kmem_cache *cachep, unsigned long *addr,
                            unsigned long caller)
{
        int size = obj_size(cachep);

        addr = (unsigned long *)&((char *)addr)[obj_offset(cachep)];

        if (size < 5 * sizeof(unsigned long))
                return;

        *addr++ = 0x12345678;
        *addr++ = caller;
        *addr++ = smp_processor_id();
        size -= 3 * sizeof(unsigned long);
        {
                unsigned long *sptr = &caller;
                unsigned long svalue;

                while (!kstack_end(sptr)) {
                        svalue = *sptr++;
                        if (kernel_text_address(svalue)) {
                                *addr++ = svalue;
                                size -= sizeof(unsigned long);
                                if (size <= sizeof(unsigned long))
                                        break;
                        }
                }

        }
        *addr++ = 0x87654321;
}
#endif

static void poison_obj(struct kmem_cache *cachep, void *addr, unsigned char val)
{
        int size = obj_size(cachep);
        addr = &((char *)addr)[obj_offset(cachep)];

        memset(addr, val, size);
        *(unsigned char *)(addr + size - 1) = POISON_END;
}

static void dump_line(char *data, int offset, int limit)
{
        int i;
        printk(KERN_ERR "%03x:", offset);
        for (i = 0; i < limit; i++) {
                printk(" %02x", (unsigned char)data[offset + i]);
        }
        printk("\n");
}
#endif

#if DEBUG

static void print_objinfo(struct kmem_cache *cachep, void *objp, int lines)
{
        int i, size;
        char *realobj;

        if (cachep->flags & SLAB_RED_ZONE) {
                printk(KERN_ERR "Redzone: 0x%lx/0x%lx.\n",
                       *dbg_redzone1(cachep, objp),
                       *dbg_redzone2(cachep, objp));
        }

        if (cachep->flags & SLAB_STORE_USER) {
                printk(KERN_ERR "Last user: [<%p>]",
                       *dbg_userword(cachep, objp));
                print_symbol("(%s)",
                             (unsigned long)*dbg_userword(cachep, objp));
                printk("\n");
        }
        realobj = (char *)objp + obj_offset(cachep);
        size = obj_size(cachep);
        for (i = 0; i < size && lines; i += 16, lines--) {
                int limit;
                limit = 16;
                if (i + limit > size)
                        limit = size - i;
                dump_line(realobj, i, limit);
        }
}

static void check_poison_obj(struct kmem_cache *cachep, void *objp)
{
        char *realobj;
        int size, i;
        int lines = 0;

        realobj = (char *)objp + obj_offset(cachep);
        size = obj_size(cachep);

        for (i = 0; i < size; i++) {
                char exp = POISON_FREE;
                if (i == size - 1)
                        exp = POISON_END;
                if (realobj[i] != exp) {
                        int limit;
                        /* Mismatch ! */
                        /* Print header */
                        if (lines == 0) {
                                printk(KERN_ERR
                                       "Slab corruption: start=%p, len=%d\n",
                                       realobj, size);
                                print_objinfo(cachep, objp, 0);
                        }
                        /* Hexdump the affected line */
                        i = (i / 16) * 16;
                        limit = 16;
                        if (i + limit > size)
                                limit = size - i;
                        dump_line(realobj, i, limit);
                        i += 16;
                        lines++;
                        /* Limit to 5 lines */
                        if (lines > 5)
                                break;
                }
        }
        if (lines != 0) {
                /* Print some data about the neighboring objects, if they
                 * exist:
                 */
                struct slab *slabp = virt_to_slab(objp);
                int objnr;

                objnr = (unsigned)(objp - slabp->s_mem) / cachep->buffer_size;
                if (objnr) {
                        objp = slabp->s_mem + (objnr - 1) * cachep->buffer_size;
                        realobj = (char *)objp + obj_offset(cachep);
                        printk(KERN_ERR "Prev obj: start=%p, len=%d\n",
                               realobj, size);
                        print_objinfo(cachep, objp, 2);
                }
                if (objnr + 1 < cachep->num) {
                        objp = slabp->s_mem + (objnr + 1) * cachep->buffer_size;
                        realobj = (char *)objp + obj_offset(cachep);
                        printk(KERN_ERR "Next obj: start=%p, len=%d\n",
                               realobj, size);
                        print_objinfo(cachep, objp, 2);
                }
        }
}
#endif

#if DEBUG
/**
 * slab_destroy_objs - call the registered destructor for each object in
 *      a slab that is to be destroyed.
 */
static void slab_destroy_objs(struct kmem_cache *cachep, struct slab *slabp)
{
        int i;
        for (i = 0; i < cachep->num; i++) {
                void *objp = slabp->s_mem + cachep->buffer_size * i;

                if (cachep->flags & SLAB_POISON) {
#ifdef CONFIG_DEBUG_PAGEALLOC
                        if ((cachep->buffer_size % PAGE_SIZE) == 0
                            && OFF_SLAB(cachep))
                                kernel_map_pages(virt_to_page(objp),
                                                 cachep->buffer_size / PAGE_SIZE,
                                                 1);
                        else
                                check_poison_obj(cachep, objp);
#else
                        check_poison_obj(cachep, objp);
#endif
                }
                if (cachep->flags & SLAB_RED_ZONE) {
                        if (*dbg_redzone1(cachep, objp) != RED_INACTIVE)
                                slab_error(cachep, "start of a freed object "
                                           "was overwritten");
                        if (*dbg_redzone2(cachep, objp) != RED_INACTIVE)
                                slab_error(cachep, "end of a freed object "
                                           "was overwritten");
                }
                if (cachep->dtor && !(cachep->flags & SLAB_POISON))
                        (cachep->dtor) (objp + obj_offset(cachep), cachep, 0);
        }
}
#else
static void slab_destroy_objs(struct kmem_cache *cachep, struct slab *slabp)
{
        if (cachep->dtor) {
                int i;
                for (i = 0; i < cachep->num; i++) {
                        void *objp = slabp->s_mem + cachep->buffer_size * i;
                        (cachep->dtor) (objp, cachep, 0);
                }
        }
}
#endif

/**
 * Destroy all the objs in a slab, and release the mem back to the system.
 * Before calling the slab must have been unlinked from the cache.
 * The cache-lock is not held/needed.
 */
static void slab_destroy(struct kmem_cache *cachep, struct slab *slabp)
{
        void *addr = slabp->s_mem - slabp->colouroff;

        slab_destroy_objs(cachep, slabp);
        if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU)) {
                struct slab_rcu *slab_rcu;

                slab_rcu = (struct slab_rcu *)slabp;
                slab_rcu->cachep = cachep;
                slab_rcu->addr = addr;
                call_rcu(&slab_rcu->head, kmem_rcu_free);
        } else {
                kmem_freepages(cachep, addr);
                if (OFF_SLAB(cachep))
                        kmem_cache_free(cachep->slabp_cache, slabp);
        }
}

/* For setting up all the kmem_list3s for cache whose buffer_size is same
   as size of kmem_list3. */
static void set_up_list3s(struct kmem_cache *cachep, int index)
{
        int node;

        for_each_online_node(node) {
                cachep->nodelists[node] = &initkmem_list3[index + node];
                cachep->nodelists[node]->next_reap = jiffies +
                    REAPTIMEOUT_LIST3 +
                    ((unsigned long)cachep) % REAPTIMEOUT_LIST3;
        }
}

/**
 * calculate_slab_order - calculate size (page order) of slabs
 * @cachep: pointer to the cache that is being created
 * @size: size of objects to be created in this cache.
 * @align: required alignment for the objects.
 * @flags: slab allocation flags
 *
 * Also calculates the number of objects per slab.
 *
 * This could be made much more intelligent.  For now, try to avoid using
 * high order pages for slabs.  When the gfp() functions are more friendly
 * towards high-order requests, this should be changed.
 */
static inline size_t calculate_slab_order(struct kmem_cache *cachep,
                        size_t size, size_t align, unsigned long flags)
{
        size_t left_over = 0;

        for (;; cachep->gfporder++) {
                unsigned int num;
                size_t remainder;

                if (cachep->gfporder > MAX_GFP_ORDER) {
                        cachep->num = 0;
                        break;
                }

                cache_estimate(cachep->gfporder, size, align, flags,
                               &remainder, &num);
                if (!num)
                        continue;
                /* More than offslab_limit objects will cause problems */
                if (flags & CFLGS_OFF_SLAB && cachep->num > offslab_limit)
                        break;

                cachep->num = num;
                left_over = remainder;

                /*
                 * Large number of objects is good, but very large slabs are
                 * currently bad for the gfp()s.
                 */
                if (cachep->gfporder >= slab_break_gfp_order)
                        break;

                if ((left_over * 8) <= (PAGE_SIZE << cachep->gfporder))
                        /* Acceptable internal fragmentation */
                        break;
        }
        return left_over;
}

/**
 * kmem_cache_create - Create a cache.
 * @name: A string which is used in /proc/slabinfo to identify this cache.
 * @size: The size of objects to be created in this cache.
 * @align: The required alignment for the objects.
 * @flags: SLAB flags
 * @ctor: A constructor for the objects.
 * @dtor: A destructor for the objects.
 *
 * Returns a ptr to the cache on success, NULL on failure.
 * Cannot be called within a int, but can be interrupted.
 * The @ctor is run when new pages are allocated by the cache
 * and the @dtor is run before the pages are handed back.
 *
 * @name must be valid until the cache is destroyed. This implies that
 * the module calling this has to destroy the cache before getting 
 * unloaded.
 * 
 * The flags are
 *
 * %SLAB_POISON - Poison the slab with a known test pattern (a5a5a5a5)
 * to catch references to uninitialised memory.
 *
 * %SLAB_RED_ZONE - Insert `Red' zones around the allocated memory to check
 * for buffer overruns.
 *
 * %SLAB_NO_REAP - Don't automatically reap this cache when we're under
 * memory pressure.
 *
 * %SLAB_HWCACHE_ALIGN - Align the objects in this cache to a hardware
 * cacheline.  This can be beneficial if you're counting cycles as closely
 * as davem.
 */
struct kmem_cache *
kmem_cache_create (const char *name, size_t size, size_t align,
        unsigned long flags, void (*ctor)(void*, struct kmem_cache *, unsigned long),
        void (*dtor)(void*, struct kmem_cache *, unsigned long))
{
        size_t left_over, slab_size, ralign;
        struct kmem_cache *cachep = NULL;
        struct list_head *p;

        /*
         * Sanity checks... these are all serious usage bugs.
         */
        if ((!name) ||
            in_interrupt() ||
            (size < BYTES_PER_WORD) ||
            (size > (1 << MAX_OBJ_ORDER) * PAGE_SIZE) || (dtor && !ctor)) {
                printk(KERN_ERR "%s: Early error in slab %s\n",
                       __FUNCTION__, name);
                BUG();
        }

        /*
         * Prevent CPUs from coming and going.
         * lock_cpu_hotplug() nests outside cache_chain_mutex
         */
        lock_cpu_hotplug();

        mutex_lock(&cache_chain_mutex);

        list_for_each(p, &cache_chain) {
                struct kmem_cache *pc = list_entry(p, struct kmem_cache, next);
                mm_segment_t old_fs = get_fs();
                char tmp;
                int res;

                /*
                 * This happens when the module gets unloaded and doesn't
                 * destroy its slab cache and no-one else reuses the vmalloc
                 * area of the module.  Print a warning.
                 */
                set_fs(KERNEL_DS);
                res = __get_user(tmp, pc->name);
                set_fs(old_fs);
                if (res) {
                        printk("SLAB: cache with size %d has lost its name\n",
                               pc->buffer_size);
                        continue;
                }

                if (!strcmp(pc->name, name)) {
                        printk("kmem_cache_create: duplicate cache %s\n", name);
                        dump_stack();
                        goto oops;
                }
        }

#if DEBUG
        WARN_ON(strchr(name, ' '));     /* It confuses parsers */
        if ((flags & SLAB_DEBUG_INITIAL) && !ctor) {
                /* No constructor, but inital state check requested */
                printk(KERN_ERR "%s: No con, but init state check "
                       "requested - %s\n", __FUNCTION__, name);
                flags &= ~SLAB_DEBUG_INITIAL;
        }
#if FORCED_DEBUG
        /*
         * Enable redzoning and last user accounting, except for caches with
         * large objects, if the increased size would increase the object size
         * above the next power of two: caches with object sizes just above a
         * power of two have a significant amount of internal fragmentation.
         */
        if ((size < 4096
             || fls(size - 1) == fls(size - 1 + 3 * BYTES_PER_WORD)))
                flags |= SLAB_RED_ZONE | SLAB_STORE_USER;
        if (!(flags & SLAB_DESTROY_BY_RCU))
                flags |= SLAB_POISON;
#endif
        if (flags & SLAB_DESTROY_BY_RCU)
                BUG_ON(flags & SLAB_POISON);
#endif
        if (flags & SLAB_DESTROY_BY_RCU)
                BUG_ON(dtor);

        /*
         * Always checks flags, a caller might be expecting debug
         * support which isn't available.
         */
        if (flags & ~CREATE_MASK)
                BUG();

        /* Check that size is in terms of words.  This is needed to avoid
         * unaligned accesses for some archs when redzoning is used, and makes
         * sure any on-slab bufctl's are also correctly aligned.
         */
        if (size & (BYTES_PER_WORD - 1)) {
                size += (BYTES_PER_WORD - 1);
                size &= ~(BYTES_PER_WORD - 1);
        }

        /* calculate out the final buffer alignment: */
        /* 1) arch recommendation: can be overridden for debug */
        if (flags & SLAB_HWCACHE_ALIGN) {
                /* Default alignment: as specified by the arch code.
                 * Except if an object is really small, then squeeze multiple
                 * objects into one cacheline.
                 */
                ralign = cache_line_size();
                while (size <= ralign / 2)
                        ralign /= 2;
        } else {
                ralign = BYTES_PER_WORD;
        }
        /* 2) arch mandated alignment: disables debug if necessary */
        if (ralign < ARCH_SLAB_MINALIGN) {
                ralign = ARCH_SLAB_MINALIGN;
                if (ralign > BYTES_PER_WORD)
                        flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
        }
        /* 3) caller mandated alignment: disables debug if necessary */
        if (ralign < align) {
                ralign = align;
                if (ralign > BYTES_PER_WORD)
                        flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
        }
        /* 4) Store it. Note that the debug code below can reduce
         *    the alignment to BYTES_PER_WORD.
         */
        align = ralign;

        /* Get cache's description obj. */
        cachep = kmem_cache_alloc(&cache_cache, SLAB_KERNEL);
        if (!cachep)
                goto oops;
        memset(cachep, 0, sizeof(struct kmem_cache));

#if DEBUG
        cachep->obj_size = size;

        if (flags & SLAB_RED_ZONE) {
                /* redzoning only works with word aligned caches */
                align = BYTES_PER_WORD;

                /* add space for red zone words */
                cachep->obj_offset += BYTES_PER_WORD;
                size += 2 * BYTES_PER_WORD;
        }
        if (flags & SLAB_STORE_USER) {
                /* user store requires word alignment and
                 * one word storage behind the end of the real
                 * object.
                 */
                align = BYTES_PER_WORD;
                size += BYTES_PER_WORD;
        }
#if FORCED_DEBUG && defined(CONFIG_DEBUG_PAGEALLOC)
        if (size >= malloc_sizes[INDEX_L3 + 1].cs_size
            && cachep->obj_size > cache_line_size() && size < PAGE_SIZE) {
                cachep->obj_offset += PAGE_SIZE - size;
                size = PAGE_SIZE;
        }
#endif
#endif

        /* Determine if the slab management is 'on' or 'off' slab. */
        if (size >= (PAGE_SIZE >> 3))
                /*
                 * Size is large, assume best to place the slab management obj
                 * off-slab (should allow better packing of objs).
                 */
                flags |= CFLGS_OFF_SLAB;

        size = ALIGN(size, align);

        if ((flags & SLAB_RECLAIM_ACCOUNT) && size <= PAGE_SIZE) {
                /*
                 * A VFS-reclaimable slab tends to have most allocations
                 * as GFP_NOFS and we really don't want to have to be allocating
                 * higher-order pages when we are unable to shrink dcache.
                 */
                cachep->gfporder = 0;
                cache_estimate(cachep->gfporder, size, align, flags,
                               &left_over, &cachep->num);
        } else
                left_over = calculate_slab_order(cachep, size, align, flags);

        if (!cachep->num) {
                printk("kmem_cache_create: couldn't create cache %s.\n", name);
                kmem_cache_free(&cache_cache, cachep);
                cachep = NULL;
                goto oops;
        }
        slab_size = ALIGN(cachep->num * sizeof(kmem_bufctl_t)
                          + sizeof(struct slab), align);

        /*
         * If the slab has been placed off-slab, and we have enough space then
         * move it on-slab. This is at the expense of any extra colouring.
         */
        if (flags & CFLGS_OFF_SLAB && left_over >= slab_size) {
                flags &= ~CFLGS_OFF_SLAB;
                left_over -= slab_size;
        }

        if (flags & CFLGS_OFF_SLAB) {
                /* really off slab. No need for manual alignment */
                slab_size =
                    cachep->num * sizeof(kmem_bufctl_t) + sizeof(struct slab);
        }

        cachep->colour_off = cache_line_size();
        /* Offset must be a multiple of the alignment. */
        if (cachep->colour_off < align)
                cachep->colour_off = align;
        cachep->colour = left_over / cachep->colour_off;
        cachep->slab_size = slab_size;
        cachep->flags = flags;
        cachep->gfpflags = 0;
        if (flags & SLAB_CACHE_DMA)
                cachep->gfpflags |= GFP_DMA;
        spin_lock_init(&cachep->spinlock);
        cachep->buffer_size = size;

        if (flags & CFLGS_OFF_SLAB)
                cachep->slabp_cache = kmem_find_general_cachep(slab_size, 0u);
        cachep->ctor = ctor;
        cachep->dtor = dtor;
        cachep->name = name;


        if (g_cpucache_up == FULL) {
                enable_cpucache(cachep);
        } else {
                if (g_cpucache_up == NONE) {
                        /* Note: the first kmem_cache_create must create
                         * the cache that's used by kmalloc(24), otherwise
                         * the creation of further caches will BUG().
                         */
                        cachep->array[smp_processor_id()] =
                            &initarray_generic.cache;

                        /* If the cache that's used by
                         * kmalloc(sizeof(kmem_list3)) is the first cache,
                         * then we need to set up all its list3s, otherwise
                         * the creation of further caches will BUG().
                         */
                        set_up_list3s(cachep, SIZE_AC);
                        if (INDEX_AC == INDEX_L3)
                                g_cpucache_up = PARTIAL_L3;
                        else
                                g_cpucache_up = PARTIAL_AC;
                } else {
                        cachep->array[smp_processor_id()] =
                            kmalloc(sizeof(struct arraycache_init), GFP_KERNEL);

                        if (g_cpucache_up == PARTIAL_AC) {
                                set_up_list3s(cachep, SIZE_L3);
                                g_cpucache_up = PARTIAL_L3;
                        } else {
                                int node;
                                for_each_online_node(node) {

                                        cachep->nodelists[node] =
                                            kmalloc_node(sizeof
                                                         (struct kmem_list3),
                                                         GFP_KERNEL, node);
                                        BUG_ON(!cachep->nodelists[node]);
                                        kmem_list3_init(cachep->
                                                        nodelists[node]);
                                }
                        }
                }
                cachep->nodelists[numa_node_id()]->next_reap =
                    jiffies + REAPTIMEOUT_LIST3 +
                    ((unsigned long)cachep) % REAPTIMEOUT_LIST3;

                BUG_ON(!cpu_cache_get(cachep));
                cpu_cache_get(cachep)->avail = 0;
                cpu_cache_get(cachep)->limit = BOOT_CPUCACHE_ENTRIES;
                cpu_cache_get(cachep)->batchcount = 1;
                cpu_cache_get(cachep)->touched = 0;
                cachep->batchcount = 1;
                cachep->limit = BOOT_CPUCACHE_ENTRIES;
        }

        /* cache setup completed, link it into the list */
        list_add(&cachep->next, &cache_chain);
      oops:
        if (!cachep && (flags & SLAB_PANIC))
                panic("kmem_cache_create(): failed to create slab `%s'\n",
                      name);
        mutex_unlock(&cache_chain_mutex);
        unlock_cpu_hotplug();
        return cachep;
}
EXPORT_SYMBOL(kmem_cache_create);

#if DEBUG
static void check_irq_off(void)
{
        BUG_ON(!irqs_disabled());
}

static void check_irq_on(void)
{
        BUG_ON(irqs_disabled());
}

static void check_spinlock_acquired(struct kmem_cache *cachep)
{
#ifdef CONFIG_SMP
        check_irq_off();
        assert_spin_locked(&cachep->nodelists[numa_node_id()]->list_lock);
#endif
}

static void check_spinlock_acquired_node(struct kmem_cache *cachep, int node)
{
#ifdef CONFIG_SMP
        check_irq_off();
        assert_spin_locked(&cachep->nodelists[node]->list_lock);
#endif
}

#else
#define check_irq_off() do { } while(0)
#define check_irq_on()  do { } while(0)
#define check_spinlock_acquired(x) do { } while(0)
#define check_spinlock_acquired_node(x, y) do { } while(0)
#endif

/*
 * Waits for all CPUs to execute func().
 */
static void smp_call_function_all_cpus(void (*func)(void *arg), void *arg)
{
        check_irq_on();
        preempt_disable();

        local_irq_disable();
        func(arg);
        local_irq_enable();

        if (smp_call_function(func, arg, 1, 1))
                BUG();

        preempt_enable();
}

static void drain_array_locked(struct kmem_cache *cachep, struct array_cache *ac,
                                int force, int node);

static void do_drain(void *arg)
{
        struct kmem_cache *cachep = (struct kmem_cache *) arg;
        struct array_cache *ac;
        int node = numa_node_id();

        check_irq_off();
        ac = cpu_cache_get(cachep);
        spin_lock(&cachep->nodelists[node]->list_lock);
        free_block(cachep, ac->entry, ac->avail, node);
        spin_unlock(&cachep->nodelists[node]->list_lock);
        ac->avail = 0;
}

static void drain_cpu_caches(struct kmem_cache *cachep)
{
        struct kmem_list3 *l3;
        int node;

        smp_call_function_all_cpus(do_drain, cachep);
        check_irq_on();
        for_each_online_node(node) {
                l3 = cachep->nodelists[node];
                if (l3) {
                        spin_lock_irq(&l3->list_lock);
                        drain_array_locked(cachep, l3->shared, 1, node);
                        spin_unlock_irq(&l3->list_lock);
                        if (l3->alien)
                                drain_alien_cache(cachep, l3->alien);
                }
        }
}

static int __node_shrink(struct kmem_cache *cachep, int node)
{
        struct slab *slabp;
        struct kmem_list3 *l3 = cachep->nodelists[node];
        int ret;

        for (;;) {
                struct list_head *p;

                p = l3->slabs_free.prev;
                if (p == &l3->slabs_free)
                        break;

                slabp = list_entry(l3->slabs_free.prev, struct slab, list);
#if DEBUG
                if (slabp->inuse)
                        BUG();
#endif
                list_del(&slabp->list);

                l3->free_objects -= cachep->num;
                spin_unlock_irq(&l3->list_lock);
                slab_destroy(cachep, slabp);
                spin_lock_irq(&l3->list_lock);
        }
        ret = !list_empty(&l3->slabs_full) || !list_empty(&l3->slabs_partial);
        return ret;
}

static int __cache_shrink(struct kmem_cache *cachep)
{
        int ret = 0, i = 0;
        struct kmem_list3 *l3;

        drain_cpu_caches(cachep);

        check_irq_on();
        for_each_online_node(i) {
                l3 = cachep->nodelists[i];
                if (l3) {
                        spin_lock_irq(&l3->list_lock);
                        ret += __node_shrink(cachep, i);
                        spin_unlock_irq(&l3->list_lock);
                }
        }
        return (ret ? 1 : 0);
}

/**
 * kmem_cache_shrink - Shrink a cache.
 * @cachep: The cache to shrink.
 *
 * Releases as many slabs as possible for a cache.
 * To help debugging, a zero exit status indicates all slabs were released.
 */
int kmem_cache_shrink(struct kmem_cache *cachep)
{
        if (!cachep || in_interrupt())
                BUG();

        return __cache_shrink(cachep);
}
EXPORT_SYMBOL(kmem_cache_shrink);

/**
 * kmem_cache_destroy - delete a cache
 * @cachep: the cache to destroy
 *
 * Remove a struct kmem_cache object from the slab cache.
 * Returns 0 on success.
 *
 * It is expected this function will be called by a module when it is
 * unloaded.  This will remove the cache completely, and avoid a duplicate
 * cache being allocated each time a module is loaded and unloaded, if the
 * module doesn't have persistent in-kernel storage across loads and unloads.
 *
 * The cache must be empty before calling this function.
 *
 * The caller must guarantee that noone will allocate memory from the cache
 * during the kmem_cache_destroy().
 */
int kmem_cache_destroy(struct kmem_cache *cachep)
{
        int i;
        struct kmem_list3 *l3;

        if (!cachep || in_interrupt())
                BUG();

        /* Don't let CPUs to come and go */
        lock_cpu_hotplug();

        /* Find the cache in the chain of caches. */
        mutex_lock(&cache_chain_mutex);
        /*
         * the chain is never empty, cache_cache is never destroyed
         */
        list_del(&cachep->next);
        mutex_unlock(&cache_chain_mutex);

        if (__cache_shrink(cachep)) {
                slab_error(cachep, "Can't free all objects");
                mutex_lock(&cache_chain_mutex);
                list_add(&cachep->next, &cache_chain);
                mutex_unlock(&cache_chain_mutex);
                unlock_cpu_hotplug();
                return 1;
        }

        if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU))
                synchronize_rcu();

        for_each_online_cpu(i)
            kfree(cachep->array[i]);

        /* NUMA: free the list3 structures */
        for_each_online_node(i) {
                if ((l3 = cachep->nodelists[i])) {
                        kfree(l3->shared);
                        free_alien_cache(l3->alien);
                        kfree(l3);
                }
        }
        kmem_cache_free(&cache_cache, cachep);

        unlock_cpu_hotplug();

        return 0;
}
EXPORT_SYMBOL(kmem_cache_destroy);

/* Get the memory for a slab management obj. */
static struct slab *alloc_slabmgmt(struct kmem_cache *cachep, void *objp,
                                   int colour_off, gfp_t local_flags)
{
        struct slab *slabp;

        if (OFF_SLAB(cachep)) {
                /* Slab management obj is off-slab. */
                slabp = kmem_cache_alloc(cachep->slabp_cache, local_flags);
                if (!slabp)
                        return NULL;
        } else {
                slabp = objp + colour_off;
                colour_off += cachep->slab_size;
        }
        slabp->inuse = 0;
        slabp->colouroff = colour_off;
        slabp->s_mem = objp + colour_off;

        return slabp;
}

static inline kmem_bufctl_t *slab_bufctl(struct slab *slabp)
{
        return (kmem_bufctl_t *) (slabp + 1);
}

static void cache_init_objs(struct kmem_cache *cachep,
                            struct slab *slabp, unsigned long ctor_flags)
{
        int i;

        for (i = 0; i < cachep->num; i++) {
                void *objp = slabp->s_mem + cachep->buffer_size * i;
#if DEBUG
                /* need to poison the objs? */
                if (cachep->flags & SLAB_POISON)
                        poison_obj(cachep, objp, POISON_FREE);
                if (cachep->flags & SLAB_STORE_USER)
                        *dbg_userword(cachep, objp) = NULL;

                if (cachep->flags & SLAB_RED_ZONE) {
                        *dbg_redzone1(cachep, objp) = RED_INACTIVE;
                        *dbg_redzone2(cachep, objp) = RED_INACTIVE;
                }
                /*
                 * Constructors are not allowed to allocate memory from
                 * the same cache which they are a constructor for.
                 * Otherwise, deadlock. They must also be threaded.
                 */
                if (cachep->ctor && !(cachep->flags & SLAB_POISON))
                        cachep->ctor(objp + obj_offset(cachep), cachep,
                                     ctor_flags);

                if (cachep->flags & SLAB_RED_ZONE) {
                        if (*dbg_redzone2(cachep, objp) != RED_INACTIVE)
                                slab_error(cachep, "constructor overwrote the"
                                           " end of an object");
                        if (*dbg_redzone1(cachep, objp) != RED_INACTIVE)
                                slab_error(cachep, "constructor overwrote the"
                                           " start of an object");
                }
                if ((cachep->buffer_size % PAGE_SIZE) == 0 && OFF_SLAB(cachep)
                    && cachep->flags & SLAB_POISON)
                        kernel_map_pages(virt_to_page(objp),
                                         cachep->buffer_size / PAGE_SIZE, 0);
#else
                if (cachep->ctor)
                        cachep->ctor(objp, cachep, ctor_flags);
#endif
                slab_bufctl(slabp)[i] = i + 1;
        }
        slab_bufctl(slabp)[i - 1] = BUFCTL_END;
        slabp->free = 0;
}

static void kmem_flagcheck(struct kmem_cache *cachep, gfp_t flags)
{
        if (flags & SLAB_DMA) {
                if (!(cachep->gfpflags & GFP_DMA))
                        BUG();
        } else {
                if (cachep->gfpflags & GFP_DMA)
                        BUG();
        }
}

static void *slab_get_obj(struct kmem_cache *cachep, struct slab *slabp, int nodeid)
{
        void *objp = slabp->s_mem + (slabp->free * cachep->buffer_size);
        kmem_bufctl_t next;

        slabp->inuse++;
        next = slab_bufctl(slabp)[slabp->free];
#if DEBUG
        slab_bufctl(slabp)[slabp->free] = BUFCTL_FREE;
        WARN_ON(slabp->nodeid != nodeid);
#endif
        slabp->free = next;

        return objp;
}

static void slab_put_obj(struct kmem_cache *cachep, struct slab *slabp, void *objp,
                          int nodeid)
{
        unsigned int objnr = (unsigned)(objp-slabp->s_mem) / cachep->buffer_size;

#if DEBUG
        /* Verify that the slab belongs to the intended node */
        WARN_ON(slabp->nodeid != nodeid);

        if (slab_bufctl(slabp)[objnr] != BUFCTL_FREE) {
                printk(KERN_ERR "slab: double free detected in cache "
                       "'%s', objp %p\n", cachep->name, objp);
                BUG();
        }
#endif
        slab_bufctl(slabp)[objnr] = slabp->free;
        slabp->free = objnr;
        slabp->inuse--;
}

static void set_slab_attr(struct kmem_cache *cachep, struct slab *slabp, void *objp)
{
        int i;
        struct page *page;

        /* Nasty!!!!!! I hope this is OK. */
        i = 1 << cachep->gfporder;
        page = virt_to_page(objp);
        do {
                page_set_cache(page, cachep);
                page_set_slab(page, slabp);
                page++;
        } while (--i);
}

/*
 * Grow (by 1) the number of slabs within a cache.  This is called by
 * kmem_cache_alloc() when there are no active objs left in a cache.
 */
static int cache_grow(struct kmem_cache *cachep, gfp_t flags, int nodeid)
{
        struct slab *slabp;
        void *objp;
        size_t offset;
        gfp_t local_flags;
        unsigned long ctor_flags;
        struct kmem_list3 *l3;

        /* Be lazy and only check for valid flags here,
         * keeping it out of the critical path in kmem_cache_alloc().
         */
        if (flags & ~(SLAB_DMA | SLAB_LEVEL_MASK | SLAB_NO_GROW))
                BUG();
        if (flags & SLAB_NO_GROW)
                return 0;

        ctor_flags = SLAB_CTOR_CONSTRUCTOR;
        local_flags = (flags & SLAB_LEVEL_MASK);
        if (!(local_flags & __GFP_WAIT))
                /*
                 * Not allowed to sleep.  Need to tell a constructor about
                 * this - it might need to know...
                 */
                ctor_flags |= SLAB_CTOR_ATOMIC;

        /* Take the l3 list lock to change the colour_next on this node */
        check_irq_off();
        l3 = cachep->nodelists[nodeid];
        spin_lock(&l3->list_lock);

        /* Get colour for the slab, and cal the next value. */
        offset = l3->colour_next;
        l3->colour_next++;
        if (l3->colour_next >= cachep->colour)
                l3->colour_next = 0;
        spin_unlock(&l3->list_lock);

        offset *= cachep->colour_off;

        if (local_flags & __GFP_WAIT)
                local_irq_enable();

        /*
         * The test for missing atomic flag is performed here, rather than
         * the more obvious place, simply to reduce the critical path length
         * in kmem_cache_alloc(). If a caller is seriously mis-behaving they
         * will eventually be caught here (where it matters).
         */
        kmem_flagcheck(cachep, flags);

        /* Get mem for the objs.
         * Attempt to allocate a physical page from 'nodeid',
         */
        if (!(objp = kmem_getpages(cachep, flags, nodeid)))
                goto failed;

        /* Get slab management. */
        if (!(slabp = alloc_slabmgmt(cachep, objp, offset, local_flags)))
                goto opps1;

        slabp->nodeid = nodeid;
        set_slab_attr(cachep, slabp, objp);

        cache_init_objs(cachep, slabp, ctor_flags);

        if (local_flags & __GFP_WAIT)
                local_irq_disable();
        check_irq_off();
        spin_lock(&l3->list_lock);

        /* Make slab active. */
        list_add_tail(&slabp->list, &(l3->slabs_free));
        STATS_INC_GROWN(cachep);
        l3->free_objects += cachep->num;
        spin_unlock(&l3->list_lock);
        return 1;
      opps1:
        kmem_freepages(cachep, objp);
      failed:
        if (local_flags & __GFP_WAIT)
                local_irq_disable();
        return 0;
}

#if DEBUG

/*
 * Perform extra freeing checks:
 * - detect bad pointers.
 * - POISON/RED_ZONE checking
 * - destructor calls, for caches with POISON+dtor
 */
static void kfree_debugcheck(const void *objp)
{
        struct page *page;

        if (!virt_addr_valid(objp)) {
                printk(KERN_ERR "kfree_debugcheck: out of range ptr %lxh.\n",
                       (unsigned long)objp);
                BUG();
        }
        page = virt_to_page(objp);
        if (!PageSlab(page)) {
                printk(KERN_ERR "kfree_debugcheck: bad ptr %lxh.\n",
                       (unsigned long)objp);
                BUG();
        }
}

static void *cache_free_debugcheck(struct kmem_cache *cachep, void *objp,
                                   void *caller)
{
        struct page *page;
        unsigned int objnr;
        struct slab *slabp;

        objp -= obj_offset(cachep);
        kfree_debugcheck(objp);
        page = virt_to_page(objp);

        if (page_get_cache(page) != cachep) {
                printk(KERN_ERR
                       "mismatch in kmem_cache_free: expected cache %p, got %p\n",
                       page_get_cache(page), cachep);
                printk(KERN_ERR "%p is %s.\n", cachep, cachep->name);
                printk(KERN_ERR "%p is %s.\n", page_get_cache(page),
                       page_get_cache(page)->name);
                WARN_ON(1);
        }
        slabp = page_get_slab(page);

        if (cachep->flags & SLAB_RED_ZONE) {
                if (*dbg_redzone1(cachep, objp) != RED_ACTIVE
                    || *dbg_redzone2(cachep, objp) != RED_ACTIVE) {
                        slab_error(cachep,
                                   "double free, or memory outside"
                                   " object was overwritten");
                        printk(KERN_ERR
                               "%p: redzone 1: 0x%lx, redzone 2: 0x%lx.\n",
                               objp, *dbg_redzone1(cachep, objp),
                               *dbg_redzone2(cachep, objp));
                }
                *dbg_redzone1(cachep, objp) = RED_INACTIVE;
                *dbg_redzone2(cachep, objp) = RED_INACTIVE;
        }
        if (cachep->flags & SLAB_STORE_USER)
                *dbg_userword(cachep, objp) = caller;

        objnr = (unsigned)(objp - slabp->s_mem) / cachep->buffer_size;

        BUG_ON(objnr >= cachep->num);
        BUG_ON(objp != slabp->s_mem + objnr * cachep->buffer_size);

        if (cachep->flags & SLAB_DEBUG_INITIAL) {
                /* Need to call the slab's constructor so the
                 * caller can perform a verify of its state (debugging).
                 * Called without the cache-lock held.
                 */
                cachep->ctor(objp + obj_offset(cachep),
                             cachep, SLAB_CTOR_CONSTRUCTOR | SLAB_CTOR_VERIFY);
        }
        if (cachep->flags & SLAB_POISON && cachep->dtor) {
                /* we want to cache poison the object,
                 * call the destruction callback
                 */
                cachep->dtor(objp + obj_offset(cachep), cachep, 0);
        }
        if (cachep->flags & SLAB_POISON) {
#ifdef CONFIG_DEBUG_PAGEALLOC
                if ((cachep->buffer_size % PAGE_SIZE) == 0 && OFF_SLAB(cachep)) {
                        store_stackinfo(cachep, objp, (unsigned long)caller);
                        kernel_map_pages(virt_to_page(objp),
                                         cachep->buffer_size / PAGE_SIZE, 0);
                } else {
                        poison_obj(cachep, objp, POISON_FREE);
                }
#else
                poison_obj(cachep, objp, POISON_FREE);
#endif
        }
        return objp;
}

static void check_slabp(struct kmem_cache *cachep, struct slab *slabp)
{
        kmem_bufctl_t i;
        int entries = 0;

        /* Check slab's freelist to see if this obj is there. */
        for (i = slabp->free; i != BUFCTL_END; i = slab_bufctl(slabp)[i]) {
                entries++;
                if (entries > cachep->num || i >= cachep->num)
                        goto bad;
        }
        if (entries != cachep->num - slabp->inuse) {
              bad:
                printk(KERN_ERR
                       "slab: Internal list corruption detected in cache '%s'(%d), slabp %p(%d). Hexdump:\n",
                       cachep->name, cachep->num, slabp, slabp->inuse);
                for (i = 0;
                     i < sizeof(slabp) + cachep->num * sizeof(kmem_bufctl_t);
                     i++) {
                        if ((i % 16) == 0)
                                printk("\n%03x:", i);
                        printk(" %02x", ((unsigned char *)slabp)[i]);
                }
                printk("\n");
                BUG();
        }
}
#else
#define kfree_debugcheck(x) do { } while(0)
#define cache_free_debugcheck(x,objp,z) (objp)
#define check_slabp(x,y) do { } while(0)
#endif

static void *cache_alloc_refill(struct kmem_cache *cachep, gfp_t flags)
{
        int batchcount;
        struct kmem_list3 *l3;
        struct array_cache *ac;

        check_irq_off();
        ac = cpu_cache_get(cachep);
      retry:
        batchcount = ac->batchcount;
        if (!ac->touched && batchcount > BATCHREFILL_LIMIT) {
                /* if there was little recent activity on this
                 * cache, then perform only a partial refill.
                 * Otherwise we could generate refill bouncing.
                 */
                batchcount = BATCHREFILL_LIMIT;
        }
        l3 = cachep->nodelists[numa_node_id()];

        BUG_ON(ac->avail > 0 || !l3);
        spin_lock(&l3->list_lock);

        if (l3->shared) {
                struct array_cache *shared_array = l3->shared;
                if (shared_array->avail) {
                        if (batchcount > shared_array->avail)
                                batchcount = shared_array->avail;
                        shared_array->avail -= batchcount;
                        ac->avail = batchcount;
                        memcpy(ac->entry,
                               &(shared_array->entry[shared_array->avail]),
                               sizeof(void *) * batchcount);
                        shared_array->touched = 1;
                        goto alloc_done;
                }
        }
        while (batchcount > 0) {
                struct list_head *entry;
                struct slab *slabp;
                /* Get slab alloc is to come from. */
                entry = l3->slabs_partial.next;
                if (entry == &l3->slabs_partial) {
                        l3->free_touched = 1;
                        entry = l3->slabs_free.next;
                        if (entry == &l3->slabs_free)
                                goto must_grow;
                }

                slabp = list_entry(entry, struct slab, list);
                check_slabp(cachep, slabp);
                check_spinlock_acquired(cachep);
                while (slabp->inuse < cachep->num && batchcount--) {
                        STATS_INC_ALLOCED(cachep);
                        STATS_INC_ACTIVE(cachep);
                        STATS_SET_HIGH(cachep);

                        ac->entry[ac->avail++] = slab_get_obj(cachep, slabp,
                                                            numa_node_id());
                }
                check_slabp(cachep, slabp);

                /* move slabp to correct slabp list: */
                list_del(&slabp->list);
                if (slabp->free == BUFCTL_END)
                        list_add(&slabp->list, &l3->slabs_full);
                else
                        list_add(&slabp->list, &l3->slabs_partial);
        }

      must_grow:
        l3->free_objects -= ac->avail;
      alloc_done:
        spin_unlock(&l3->list_lock);

        if (unlikely(!ac->avail)) {
                int x;
                x = cache_grow(cachep, flags, numa_node_id());

                // cache_grow can reenable interrupts, then ac could change.
                ac = cpu_cache_get(cachep);
                if (!x && ac->avail == 0)       // no objects in sight? abort
                        return NULL;

                if (!ac->avail) // objects refilled by interrupt?
                        goto retry;
        }
        ac->touched = 1;
        return ac->entry[--ac->avail];
}

static inline void
cache_alloc_debugcheck_before(struct kmem_cache *cachep, gfp_t flags)
{
        might_sleep_if(flags & __GFP_WAIT);
#if DEBUG
        kmem_flagcheck(cachep, flags);
#endif
}

#if DEBUG
static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep, gfp_t flags,
                                        void *objp, void *caller)
{
        if (!objp)
                return objp;
        if (cachep->flags & SLAB_POISON) {
#ifdef CONFIG_DEBUG_PAGEALLOC
                if ((cachep->buffer_size % PAGE_SIZE) == 0 && OFF_SLAB(cachep))
                        kernel_map_pages(virt_to_page(objp),
                                         cachep->buffer_size / PAGE_SIZE, 1);
                else
                        check_poison_obj(cachep, objp);
#else
                check_poison_obj(cachep, objp);
#endif
                poison_obj(cachep, objp, POISON_INUSE);
        }
        if (cachep->flags & SLAB_STORE_USER)
                *dbg_userword(cachep, objp) = caller;

        if (cachep->flags & SLAB_RED_ZONE) {
                if (*dbg_redzone1(cachep, objp) != RED_INACTIVE
                    || *dbg_redzone2(cachep, objp) != RED_INACTIVE) {
                        slab_error(cachep,
                                   "double free, or memory outside"
                                   " object was overwritten");
                        printk(KERN_ERR
                               "%p: redzone 1: 0x%lx, redzone 2: 0x%lx.\n",
                               objp, *dbg_redzone1(cachep, objp),
                               *dbg_redzone2(cachep, objp));
                }
                *dbg_redzone1(cachep, objp) = RED_ACTIVE;
                *dbg_redzone2(cachep, objp) = RED_ACTIVE;
        }
        objp += obj_offset(cachep);
        if (cachep->ctor && cachep->flags & SLAB_POISON) {
                unsigned long ctor_flags = SLAB_CTOR_CONSTRUCTOR;

                if (!(flags & __GFP_WAIT))
                        ctor_flags |= SLAB_CTOR_ATOMIC;

                cachep->ctor(objp, cachep, ctor_flags);
        }
        return objp;
}
#else
#define cache_alloc_debugcheck_after(a,b,objp,d) (objp)
#endif

static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
{
        void *objp;
        struct array_cache *ac;

#ifdef CONFIG_NUMA
        if (unlikely(current->mempolicy && !in_interrupt())) {
                int nid = slab_node(current->mempolicy);

                if (nid != numa_node_id())
                        return __cache_alloc_node(cachep, flags, nid);
        }
#endif

        check_irq_off();
        ac = cpu_cache_get(cachep);
        if (likely(ac->avail)) {
                STATS_INC_ALLOCHIT(cachep);
                ac->touched = 1;
                objp = ac->entry[--ac->avail];
        } else {
                STATS_INC_ALLOCMISS(cachep);
                objp = cache_alloc_refill(cachep, flags);
        }
        return objp;
}

static __always_inline void *
__cache_alloc(struct kmem_cache *cachep, gfp_t flags, void *caller)
{
        unsigned long save_flags;
        void *objp;

        cache_alloc_debugcheck_before(cachep, flags);

        local_irq_save(save_flags);
        objp = ____cache_alloc(cachep, flags);
        local_irq_restore(save_flags);
        objp = cache_alloc_debugcheck_after(cachep, flags, objp,
                                            caller);
        prefetchw(objp);
        return objp;
}

#ifdef CONFIG_NUMA
/*
 * A interface to enable slab creation on nodeid
 */
static void *__cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid)
{
        struct list_head *entry;
        struct slab *slabp;
        struct kmem_list3 *l3;
        void *obj;
        int x;

        l3 = cachep->nodelists[nodeid];
        BUG_ON(!l3);

      retry:
        check_irq_off();
        spin_lock(&l3->list_lock);
        entry = l3->slabs_partial.next;
        if (entry == &l3->slabs_partial) {
                l3->free_touched = 1;
                entry = l3->slabs_free.next;
                if (entry == &l3->slabs_free)
                        goto must_grow;
        }

        slabp = list_entry(entry, struct slab, list);
        check_spinlock_acquired_node(cachep, nodeid);
        check_slabp(cachep, slabp);

        STATS_INC_NODEALLOCS(cachep);
        STATS_INC_ACTIVE(cachep);
        STATS_SET_HIGH(cachep);

        BUG_ON(slabp->inuse == cachep->num);

        obj = slab_get_obj(cachep, slabp, nodeid);
        check_slabp(cachep, slabp);
        l3->free_objects--;
        /* move slabp to correct slabp list: */
        list_del(&slabp->list);

        if (slabp->free == BUFCTL_END) {
                list_add(&slabp->list, &l3->slabs_full);
        } else {
                list_add(&slabp->list, &l3->slabs_partial);
        }

        spin_unlock(&l3->list_lock);
        goto done;

      must_grow:
        spin_unlock(&l3->list_lock);
        x = cache_grow(cachep, flags, nodeid);

        if (!x)
                return NULL;

        goto retry;
      done:
        return obj;
}
#endif

/*
 * Caller needs to acquire correct kmem_list's list_lock
 */
static void free_block(struct kmem_cache *cachep, void **objpp, int nr_objects,
                       int node)
{
        int i;
        struct kmem_list3 *l3;

        for (i = 0; i < nr_objects; i++) {
                void *objp = objpp[i];
                struct slab *slabp;

                slabp = virt_to_slab(objp);
                l3 = cachep->nodelists[node];
                list_del(&slabp->list);
                check_spinlock_acquired_node(cachep, node);
                check_slabp(cachep, slabp);
                slab_put_obj(cachep, slabp, objp, node);
                STATS_DEC_ACTIVE(cachep);
                l3->free_objects++;
                check_slabp(cachep, slabp);

                /* fixup slab chains */
                if (slabp->inuse == 0) {
                        if (l3->free_objects > l3->free_limit) {
                                l3->free_objects -= cachep->num;
                                slab_destroy(cachep, slabp);
                        } else {
                                list_add(&slabp->list, &l3->slabs_free);
                        }
                } else {
                        /* Unconditionally move a slab to the end of the
                         * partial list on free - maximum time for the
                         * other objects to be freed, too.
                         */
                        list_add_tail(&slabp->list, &l3->slabs_partial);
                }
        }
}

static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac)
{
        int batchcount;
        struct kmem_list3 *l3;
        int node = numa_node_id();

        batchcount = ac->batchcount;
#if DEBUG
        BUG_ON(!batchcount || batchcount > ac->avail);
#endif
        check_irq_off();
        l3 = cachep->nodelists[node];
        spin_lock(&l3->list_lock);
        if (l3->shared) {
                struct array_cache *shared_array = l3->shared;
                int max = shared_array->limit - shared_array->avail;
                if (max) {
                        if (batchcount > max)
                                batchcount = max;
                        memcpy(&(shared_array->entry[shared_array->avail]),
                               ac->entry, sizeof(void *) * batchcount);
                        shared_array->avail += batchcount;
                        goto free_done;
                }
        }

        free_block(cachep, ac->entry, batchcount, node);
      free_done:
#if STATS
        {
                int i = 0;
                struct list_head *p;

                p = l3->slabs_free.next;
                while (p != &(l3->slabs_free)) {
                        struct slab *slabp;

                        slabp = list_entry(p, struct slab, list);
                        BUG_ON(slabp->inuse);

                        i++;
                        p = p->next;
                }
                STATS_SET_FREEABLE(cachep, i);
        }
#endif
        spin_unlock(&l3->list_lock);
        ac->avail -= batchcount;
        memmove(ac->entry, &(ac->entry[batchcount]),
                sizeof(void *) * ac->avail);
}

/*
 * __cache_free
 * Release an obj back to its cache. If the obj has a constructed
 * state, it must be in this state _before_ it is released.
 *
 * Called with disabled ints.
 */
static inline void __cache_free(struct kmem_cache *cachep, void *objp)
{
        struct array_cache *ac = cpu_cache_get(cachep);

        check_irq_off();
        objp = cache_free_debugcheck(cachep, objp, __builtin_return_address(0));

        /* Make sure we are not freeing a object from another
         * node to the array cache on this cpu.
         */
#ifdef CONFIG_NUMA
        {
                struct slab *slabp;
                slabp = virt_to_slab(objp);
                if (unlikely(slabp->nodeid != numa_node_id())) {
                        struct array_cache *alien = NULL;
                        int nodeid = slabp->nodeid;
                        struct kmem_list3 *l3 =
                            cachep->nodelists[numa_node_id()];

                        STATS_INC_NODEFREES(cachep);
                        if (l3->alien && l3->alien[nodeid]) {
                                alien = l3->alien[nodeid];
                                spin_lock(&alien->lock);
                                if (unlikely(alien->avail == alien->limit))
                                        __drain_alien_cache(cachep,
                                                            alien, nodeid);
                                alien->entry[alien->avail++] = objp;
                                spin_unlock(&alien->lock);
                        } else {
                                spin_lock(&(cachep->nodelists[nodeid])->
                                          list_lock);
                                free_block(cachep, &objp, 1, nodeid);
                                spin_unlock(&(cachep->nodelists[nodeid])->
                                            list_lock);
                        }
                        return;
                }
        }
#endif
        if (likely(ac->avail < ac->limit)) {
                STATS_INC_FREEHIT(cachep);
                ac->entry[ac->avail++] = objp;
                return;
        } else {
                STATS_INC_FREEMISS(cachep);
                cache_flusharray(cachep, ac);
                ac->entry[ac->avail++] = objp;
        }
}

/**
 * kmem_cache_alloc - Allocate an object
 * @cachep: The cache to allocate from.
 * @flags: See kmalloc().
 *
 * Allocate an object from this cache.  The flags are only relevant
 * if the cache has no available objects.
 */
void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
{
        return __cache_alloc(cachep, flags, __builtin_return_address(0));
}
EXPORT_SYMBOL(kmem_cache_alloc);

/**
 * kmem_ptr_validate - check if an untrusted pointer might
 *      be a slab entry.
 * @cachep: the cache we're checking against
 * @ptr: pointer to validate
 *
 * This verifies that the untrusted pointer looks sane:
 * it is _not_ a guarantee that the pointer is actually
 * part of the slab cache in question, but it at least
 * validates that the pointer can be dereferenced and
 * looks half-way sane.
 *
 * Currently only used for dentry validation.
 */
int fastcall kmem_ptr_validate(struct kmem_cache *cachep, void *ptr)
{
        unsigned long addr = (unsigned long)ptr;
        unsigned long min_addr = PAGE_OFFSET;
        unsigned long align_mask = BYTES_PER_WORD - 1;
        unsigned long size = cachep->buffer_size;
        struct page *page;

        if (unlikely(addr < min_addr))
                goto out;
        if (unlikely(addr > (unsigned long)high_memory - size))
                goto out;
        if (unlikely(addr & align_mask))
                goto out;
        if (unlikely(!kern_addr_valid(addr)))
                goto out;
        if (unlikely(!kern_addr_valid(addr + size - 1)))
                goto out;
        page = virt_to_page(ptr);
        if (unlikely(!PageSlab(page)))
                goto out;
        if (unlikely(page_get_cache(page) != cachep))
                goto out;
        return 1;
      out:
        return 0;
}

#ifdef CONFIG_NUMA
/**
 * kmem_cache_alloc_node - Allocate an object on the specified node
 * @cachep: The cache to allocate from.
 * @flags: See kmalloc().
 * @nodeid: node number of the target node.
 *
 * Identical to kmem_cache_alloc, except that this function is slow
 * and can sleep. And it will allocate memory on the given node, which
 * can improve the performance for cpu bound structures.
 * New and improved: it will now make sure that the object gets
 * put on the correct node list so that there is no false sharing.
 */
void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid)
{
        unsigned long save_flags;
        void *ptr;

        cache_alloc_debugcheck_before(cachep, flags);
        local_irq_save(save_flags);

        if (nodeid == -1 || nodeid == numa_node_id() ||
            !cachep->nodelists[nodeid])
                ptr = ____cache_alloc(cachep, flags);
        else
                ptr = __cache_alloc_node(cachep, flags, nodeid);
        local_irq_restore(save_flags);

        ptr = cache_alloc_debugcheck_after(cachep, flags, ptr,
                                           __builtin_return_address(0));

        return ptr;
}
EXPORT_SYMBOL(kmem_cache_alloc_node);

void *kmalloc_node(size_t size, gfp_t flags, int node)
{
        struct kmem_cache *cachep;

        cachep = kmem_find_general_cachep(size, flags);
        if (unlikely(cachep == NULL))
                return NULL;
        return kmem_cache_alloc_node(cachep, flags, node);
}
EXPORT_SYMBOL(kmalloc_node);
#endif

/**
 * kmalloc - allocate memory
 * @size: how many bytes of memory are required.
 * @flags: the type of memory to allocate.
 *
 * kmalloc is the normal method of allocating memory
 * in the kernel.
 *
 * The @flags argument may be one of:
 *
 * %GFP_USER - Allocate memory on behalf of user.  May sleep.
 *
 * %GFP_KERNEL - Allocate normal kernel ram.  May sleep.
 *
 * %GFP_ATOMIC - Allocation will not sleep.  Use inside interrupt handlers.
 *
 * Additionally, the %GFP_DMA flag may be set to indicate the memory
 * must be suitable for DMA.  This can mean different things on different
 * platforms.  For example, on i386, it means that the memory must come
 * from the first 16MB.
 */
static __always_inline void *__do_kmalloc(size_t size, gfp_t flags,
                                          void *caller)
{
        struct kmem_cache *cachep;

        /* If you want to save a few bytes .text space: replace
         * __ with kmem_.
         * Then kmalloc uses the uninlined functions instead of the inline
         * functions.
         */
        cachep = __find_general_cachep(size, flags);
        if (unlikely(cachep == NULL))
                return NULL;
        return __cache_alloc(cachep, flags, caller);
}

#ifndef CONFIG_DEBUG_SLAB

void *__kmalloc(size_t size, gfp_t flags)
{
        return __do_kmalloc(size, flags, NULL);
}
EXPORT_SYMBOL(__kmalloc);

#else

void *__kmalloc_track_caller(size_t size, gfp_t flags, void *caller)
{
        return __do_kmalloc(size, flags, caller);
}
EXPORT_SYMBOL(__kmalloc_track_caller);

#endif

#ifdef CONFIG_SMP
/**
 * __alloc_percpu - allocate one copy of the object for every present
 * cpu in the system, zeroing them.
 * Objects should be dereferenced using the per_cpu_ptr macro only.
 *
 * @size: how many bytes of memory are required.
 */
void *__alloc_percpu(size_t size)
{
        int i;
        struct percpu_data *pdata = kmalloc(sizeof(*pdata), GFP_KERNEL);

        if (!pdata)
                return NULL;

        /*
         * Cannot use for_each_online_cpu since a cpu may come online
         * and we have no way of figuring out how to fix the array
         * that we have allocated then....
         */
        for_each_cpu(i) {
                int node = cpu_to_node(i);

                if (node_online(node))
                        pdata->ptrs[i] = kmalloc_node(size, GFP_KERNEL, node);
                else
                        pdata->ptrs[i] = kmalloc(size, GFP_KERNEL);

                if (!pdata->ptrs[i])
                        goto unwind_oom;
                memset(pdata->ptrs[i], 0, size);
        }

        /* Catch derefs w/o wrappers */
        return (void *)(~(unsigned long)pdata);

      unwind_oom:
        while (--i >= 0) {
                if (!cpu_possible(i))
                        continue;
                kfree(pdata->ptrs[i]);
        }
        kfree(pdata);
        return NULL;
}
EXPORT_SYMBOL(__alloc_percpu);
#endif

/**
 * kmem_cache_free - Deallocate an object
 * @cachep: The cache the allocation was from.
 * @objp: The previously allocated object.
 *
 * Free an object which was previously allocated from this
 * cache.
 */
void kmem_cache_free(struct kmem_cache *cachep, void *objp)
{
        unsigned long flags;

        local_irq_save(flags);
        __cache_free(cachep, objp);
        local_irq_restore(flags);
}
EXPORT_SYMBOL(kmem_cache_free);

/**
 * kfree - free previously allocated memory
 * @objp: pointer returned by kmalloc.
 *
 * If @objp is NULL, no operation is performed.
 *
 * Don't free memory not originally allocated by kmalloc()
 * or you will run into trouble.
 */
void kfree(const void *objp)
{
        struct kmem_cache *c;
        unsigned long flags;

        if (unlikely(!objp))
                return;
        local_irq_save(flags);
        kfree_debugcheck(objp);
        c = virt_to_cache(objp);
        mutex_debug_check_no_locks_freed(objp, obj_size(c));
        __cache_free(c, (void *)objp);
        local_irq_restore(flags);
}
EXPORT_SYMBOL(kfree);

#ifdef CONFIG_SMP
/**
 * free_percpu - free previously allocated percpu memory
 * @objp: pointer returned by alloc_percpu.
 *
 * Don't free memory not originally allocated by alloc_percpu()
 * The complemented objp is to check for that.
 */
void free_percpu(const void *objp)
{
        int i;
        struct percpu_data *p = (struct percpu_data *)(~(unsigned long)objp);

        /*
         * We allocate for all cpus so we cannot use for online cpu here.
         */
        for_each_cpu(i)
            kfree(p->ptrs[i]);
        kfree(p);
}
EXPORT_SYMBOL(free_percpu);
#endif

unsigned int kmem_cache_size(struct kmem_cache *cachep)
{
        return obj_size(cachep);
}
EXPORT_SYMBOL(kmem_cache_size);

const char *kmem_cache_name(struct kmem_cache *cachep)
{
        return cachep->name;
}
EXPORT_SYMBOL_GPL(kmem_cache_name);

/*
 * This initializes kmem_list3 for all nodes.
 */
static int alloc_kmemlist(struct kmem_cache *cachep)
{
        int node;
        struct kmem_list3 *l3;
        int err = 0;

        for_each_online_node(node) {
                struct array_cache *nc = NULL, *new;
                struct array_cache **new_alien = NULL;
#ifdef CONFIG_NUMA
                if (!(new_alien = alloc_alien_cache(node, cachep->limit)))
                        goto fail;
#endif
                if (!(new = alloc_arraycache(node, (cachep->shared *
                                                    cachep->batchcount),
                                             0xbaadf00d)))
                        goto fail;
                if ((l3 = cachep->nodelists[node])) {

                        spin_lock_irq(&l3->list_lock);

                        if ((nc = cachep->nodelists[node]->shared))
                                free_block(cachep, nc->entry, nc->avail, node);

                        l3->shared = new;
                        if (!cachep->nodelists[node]->alien) {
                                l3->alien = new_alien;
                                new_alien = NULL;
                        }
                        l3->free_limit = (1 + nr_cpus_node(node)) *
                            cachep->batchcount + cachep->num;
                        spin_unlock_irq(&l3->list_lock);
                        kfree(nc);
                        free_alien_cache(new_alien);
                        continue;
                }
                if (!(l3 = kmalloc_node(sizeof(struct kmem_list3),
                                        GFP_KERNEL, node)))
                        goto fail;

                kmem_list3_init(l3);
                l3->next_reap = jiffies + REAPTIMEOUT_LIST3 +
                    ((unsigned long)cachep) % REAPTIMEOUT_LIST3;
                l3->shared = new;
                l3->alien = new_alien;
                l3->free_limit = (1 + nr_cpus_node(node)) *
                    cachep->batchcount + cachep->num;
                cachep->nodelists[node] = l3;
        }
        return err;
      fail:
        err = -ENOMEM;
        return err;
}

struct ccupdate_struct {
        struct kmem_cache *cachep;
        struct array_cache *new[NR_CPUS];
};

static void do_ccupdate_local(void *info)
{
        struct ccupdate_struct *new = (struct ccupdate_struct *)info;
        struct array_cache *old;

        check_irq_off();
        old = cpu_cache_get(new->cachep);

        new->cachep->array[smp_processor_id()] = new->new[smp_processor_id()];
        new->new[smp_processor_id()] = old;
}

static int do_tune_cpucache(struct kmem_cache *cachep, int limit, int batchcount,
                            int shared)
{
        struct ccupdate_struct new;
        int i, err;

        memset(&new.new, 0, sizeof(new.new));
        for_each_online_cpu(i) {
                new.new[i] =
                    alloc_arraycache(cpu_to_node(i), limit, batchcount);
                if (!new.new[i]) {
                        for (i--; i >= 0; i--)
                                kfree(new.new[i]);
                        return -ENOMEM;
                }
        }
        new.cachep = cachep;

        smp_call_function_all_cpus(do_ccupdate_local, (void *)&new);

        check_irq_on();
        spin_lock(&cachep->spinlock);
        cachep->batchcount = batchcount;
        cachep->limit = limit;
        cachep->shared = shared;
        spin_unlock(&cachep->spinlock);

        for_each_online_cpu(i) {
                struct array_cache *ccold = new.new[i];
                if (!ccold)
                        continue;
                spin_lock_irq(&cachep->nodelists[cpu_to_node(i)]->list_lock);
                free_block(cachep, ccold->entry, ccold->avail, cpu_to_node(i));
                spin_unlock_irq(&cachep->nodelists[cpu_to_node(i)]->list_lock);
                kfree(ccold);
        }

        err = alloc_kmemlist(cachep);
        if (err) {
                printk(KERN_ERR "alloc_kmemlist failed for %s, error %d.\n",
                       cachep->name, -err);
                BUG();
        }
        return 0;
}

static void enable_cpucache(struct kmem_cache *cachep)
{
        int err;
        int limit, shared;

        /* The head array serves three purposes:
         * - create a LIFO ordering, i.e. return objects that are cache-warm
         * - reduce the number of spinlock operations.
         * - reduce the number of linked list operations on the slab and 
         *   bufctl chains: array operations are cheaper.
         * The numbers are guessed, we should auto-tune as described by
         * Bonwick.
         */
        if (cachep->buffer_size > 131072)
                limit = 1;
        else if (cachep->buffer_size > PAGE_SIZE)
                limit = 8;
        else if (cachep->buffer_size > 1024)
                limit = 24;
        else if (cachep->buffer_size > 256)
                limit = 54;
        else
                limit = 120;

        /* Cpu bound tasks (e.g. network routing) can exhibit cpu bound
         * allocation behaviour: Most allocs on one cpu, most free operations
         * on another cpu. For these cases, an efficient object passing between
         * cpus is necessary. This is provided by a shared array. The array
         * replaces Bonwick's magazine layer.
         * On uniprocessor, it's functionally equivalent (but less efficient)
         * to a larger limit. Thus disabled by default.
         */
        shared = 0;
#ifdef CONFIG_SMP
        if (cachep->buffer_size <= PAGE_SIZE)
                shared = 8;
#endif

#if DEBUG
        /* With debugging enabled, large batchcount lead to excessively
         * long periods with disabled local interrupts. Limit the 
         * batchcount
         */
        if (limit > 32)
                limit = 32;
#endif
        err = do_tune_cpucache(cachep, limit, (limit + 1) / 2, shared);
        if (err)
                printk(KERN_ERR "enable_cpucache failed for %s, error %d.\n",
                       cachep->name, -err);
}

static void drain_array_locked(struct kmem_cache *cachep, struct array_cache *ac,
                                int force, int node)
{
        int tofree;

        check_spinlock_acquired_node(cachep, node);
        if (ac->touched && !force) {
                ac->touched = 0;
        } else if (ac->avail) {
                tofree = force ? ac->avail : (ac->limit + 4) / 5;
                if (tofree > ac->avail) {
                        tofree = (ac->avail + 1) / 2;
                }
                free_block(cachep, ac->entry, tofree, node);
                ac->avail -= tofree;
                memmove(ac->entry, &(ac->entry[tofree]),
                        sizeof(void *) * ac->avail);
        }
}

/**
 * cache_reap - Reclaim memory from caches.
 * @unused: unused parameter
 *
 * Called from workqueue/eventd every few seconds.
 * Purpose:
 * - clear the per-cpu caches for this CPU.
 * - return freeable pages to the main free memory pool.
 *
 * If we cannot acquire the cache chain mutex then just give up - we'll
 * try again on the next iteration.
 */
static void cache_reap(void *unused)
{
        struct list_head *walk;
        struct kmem_list3 *l3;

        if (!mutex_trylock(&cache_chain_mutex)) {
                /* Give up. Setup the next iteration. */
                schedule_delayed_work(&__get_cpu_var(reap_work),
                                      REAPTIMEOUT_CPUC);
                return;
        }

        list_for_each(walk, &cache_chain) {
                struct kmem_cache *searchp;
                struct list_head *p;
                int tofree;
                struct slab *slabp;

                searchp = list_entry(walk, struct kmem_cache, next);

                if (searchp->flags & SLAB_NO_REAP)
                        goto next;

                check_irq_on();

                l3 = searchp->nodelists[numa_node_id()];
                if (l3->alien)
                        drain_alien_cache(searchp, l3->alien);
                spin_lock_irq(&l3->list_lock);

                drain_array_locked(searchp, cpu_cache_get(searchp), 0,
                                   numa_node_id());

                if (time_after(l3->next_reap, jiffies))
                        goto next_unlock;

                l3->next_reap = jiffies + REAPTIMEOUT_LIST3;

                if (l3->shared)
                        drain_array_locked(searchp, l3->shared, 0,
                                           numa_node_id());

                if (l3->free_touched) {
                        l3->free_touched = 0;
                        goto next_unlock;
                }

                tofree =
                    (l3->free_limit + 5 * searchp->num -
                     1) / (5 * searchp->num);
                do {
                        p = l3->slabs_free.next;
                        if (p == &(l3->slabs_free))
                                break;

                        slabp = list_entry(p, struct slab, list);
                        BUG_ON(slabp->inuse);
                        list_del(&slabp->list);
                        STATS_INC_REAPED(searchp);

                        /* Safe to drop the lock. The slab is no longer
                         * linked to the cache.
                         * searchp cannot disappear, we hold
                         * cache_chain_lock
                         */
                        l3->free_objects -= searchp->num;
                        spin_unlock_irq(&l3->list_lock);
                        slab_destroy(searchp, slabp);
                        spin_lock_irq(&l3->list_lock);
                } while (--tofree > 0);
              next_unlock:
                spin_unlock_irq(&l3->list_lock);
              next:
                cond_resched();
        }
        check_irq_on();
        mutex_unlock(&cache_chain_mutex);
        drain_remote_pages();
        /* Setup the next iteration */
        schedule_delayed_work(&__get_cpu_var(reap_work), REAPTIMEOUT_CPUC);
}

#ifdef CONFIG_PROC_FS

static void print_slabinfo_header(struct seq_file *m)
{
        /*
         * Output format version, so at least we can change it
         * without _too_ many complaints.
         */
#if STATS
        seq_puts(m, "slabinfo - version: 2.1 (statistics)\n");
#else
        seq_puts(m, "slabinfo - version: 2.1\n");
#endif
        seq_puts(m, "# name            <active_objs> <num_objs> <objsize> "
                 "<objperslab> <pagesperslab>");
        seq_puts(m, " : tunables <limit> <batchcount> <sharedfactor>");
        seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail>");
#if STATS
        seq_puts(m, " : globalstat <listallocs> <maxobjs> <grown> <reaped> "
                 "<error> <maxfreeable> <nodeallocs> <remotefrees>");
        seq_puts(m, " : cpustat <allochit> <allocmiss> <freehit> <freemiss>");
#endif
        seq_putc(m, '\n');
}

static void *s_start(struct seq_file *m, loff_t *pos)
{
        loff_t n = *pos;
        struct list_head *p;

        mutex_lock(&cache_chain_mutex);
        if (!n)
                print_slabinfo_header(m);
        p = cache_chain.next;
        while (n--) {
                p = p->next;
                if (p == &cache_chain)
                        return NULL;
        }
        return list_entry(p, struct kmem_cache, next);
}

static void *s_next(struct seq_file *m, void *p, loff_t *pos)
{
        struct kmem_cache *cachep = p;
        ++*pos;
        return cachep->next.next == &cache_chain ? NULL
            : list_entry(cachep->next.next, struct kmem_cache, next);
}

static void s_stop(struct seq_file *m, void *p)
{
        mutex_unlock(&cache_chain_mutex);
}

static int s_show(struct seq_file *m, void *p)
{
        struct kmem_cache *cachep = p;
        struct list_head *q;
        struct slab *slabp;
        unsigned long active_objs;
        unsigned long num_objs;
        unsigned long active_slabs = 0;
        unsigned long num_slabs, free_objects = 0, shared_avail = 0;
        const char *name;
        char *error = NULL;
        int node;
        struct kmem_list3 *l3;

        spin_lock(&cachep->spinlock);
        active_objs = 0;
        num_slabs = 0;
        for_each_online_node(node) {
                l3 = cachep->nodelists[node];
                if (!l3)
                        continue;

                check_irq_on();
                spin_lock_irq(&l3->list_lock);

                list_for_each(q, &l3->slabs_full) {
                        slabp = list_entry(q, struct slab, list);
                        if (slabp->inuse != cachep->num && !error)
                                error = "slabs_full accounting error";
                        active_objs += cachep->num;
                        active_slabs++;
                }
                list_for_each(q, &l3->slabs_partial) {
                        slabp = list_entry(q, struct slab, list);
                        if (slabp->inuse == cachep->num && !error)
                                error = "slabs_partial inuse accounting error";
                        if (!slabp->inuse && !error)
                                error = "slabs_partial/inuse accounting error";
                        active_objs += slabp->inuse;
                        active_slabs++;
                }
                list_for_each(q, &l3->slabs_free) {
                        slabp = list_entry(q, struct slab, list);
                        if (slabp->inuse && !error)
                                error = "slabs_free/inuse accounting error";
                        num_slabs++;
                }
                free_objects += l3->free_objects;
                if (l3->shared)
                        shared_avail += l3->shared->avail;

                spin_unlock_irq(&l3->list_lock);
        }
        num_slabs += active_slabs;
        num_objs = num_slabs * cachep->num;
        if (num_objs - active_objs != free_objects && !error)
                error = "free_objects accounting error";

        name = cachep->name;
        if (error)
                printk(KERN_ERR "slab: cache %s error: %s\n", name, error);

        seq_printf(m, "%-17s %6lu %6lu %6u %4u %4d",
                   name, active_objs, num_objs, cachep->buffer_size,
                   cachep->num, (1 << cachep->gfporder));
        seq_printf(m, " : tunables %4u %4u %4u",
                   cachep->limit, cachep->batchcount, cachep->shared);
        seq_printf(m, " : slabdata %6lu %6lu %6lu",
                   active_slabs, num_slabs, shared_avail);
#if STATS
        {                       /* list3 stats */
                unsigned long high = cachep->high_mark;
                unsigned long allocs = cachep->num_allocations;
                unsigned long grown = cachep->grown;
                unsigned long reaped = cachep->reaped;
                unsigned long errors = cachep->errors;
                unsigned long max_freeable = cachep->max_freeable;
                unsigned long node_allocs = cachep->node_allocs;
                unsigned long node_frees = cachep->node_frees;

                seq_printf(m, " : globalstat %7lu %6lu %5lu %4lu \
                                %4lu %4lu %4lu %4lu", allocs, high, grown, reaped, errors, max_freeable, node_allocs, node_frees);
        }
        /* cpu stats */
        {
                unsigned long allochit = atomic_read(&cachep->allochit);
                unsigned long allocmiss = atomic_read(&cachep->allocmiss);
                unsigned long freehit = atomic_read(&cachep->freehit);
                unsigned long freemiss = atomic_read(&cachep->freemiss);

                seq_printf(m, " : cpustat %6lu %6lu %6lu %6lu",
                           allochit, allocmiss, freehit, freemiss);
        }
#endif
        seq_putc(m, '\n');
        spin_unlock(&cachep->spinlock);
        return 0;
}

/*
 * slabinfo_op - iterator that generates /proc/slabinfo
 *
 * Output layout:
 * cache-name
 * num-active-objs
 * total-objs
 * object size
 * num-active-slabs
 * total-slabs
 * num-pages-per-slab
 * + further values on SMP and with statistics enabled
 */

struct seq_operations slabinfo_op = {
        .start = s_start,
        .next = s_next,
        .stop = s_stop,
        .show = s_show,
};

#define MAX_SLABINFO_WRITE 128
/**
 * slabinfo_write - Tuning for the slab allocator
 * @file: unused
 * @buffer: user buffer
 * @count: data length
 * @ppos: unused
 */
ssize_t slabinfo_write(struct file *file, const char __user * buffer,
                       size_t count, loff_t *ppos)
{
        char kbuf[MAX_SLABINFO_WRITE + 1], *tmp;
        int limit, batchcount, shared, res;
        struct list_head *p;

        if (count > MAX_SLABINFO_WRITE)
                return -EINVAL;
        if (copy_from_user(&kbuf, buffer, count))
                return -EFAULT;
        kbuf[MAX_SLABINFO_WRITE] = '\0';

        tmp = strchr(kbuf, ' ');
        if (!tmp)
                return -EINVAL;
        *tmp = '\0';
        tmp++;
        if (sscanf(tmp, " %d %d %d", &limit, &batchcount, &shared) != 3)
                return -EINVAL;

        /* Find the cache in the chain of caches. */
        mutex_lock(&cache_chain_mutex);
        res = -EINVAL;
        list_for_each(p, &cache_chain) {
                struct kmem_cache *cachep = list_entry(p, struct kmem_cache,
                                                       next);

                if (!strcmp(cachep->name, kbuf)) {
                        if (limit < 1 ||
                            batchcount < 1 ||
                            batchcount > limit || shared < 0) {
                                res = 0;
                        } else {
                                res = do_tune_cpucache(cachep, limit,
                                                       batchcount, shared);
                        }
                        break;
                }
        }
        mutex_unlock(&cache_chain_mutex);
        if (res >= 0)
                res = count;
        return res;
}
#endif

/**
 * ksize - get the actual amount of memory allocated for a given object
 * @objp: Pointer to the object
 *
 * kmalloc may internally round up allocations and return more memory
 * than requested. ksize() can be used to determine the actual amount of
 * memory allocated. The caller may use this additional memory, even though
 * a smaller amount of memory was initially specified with the kmalloc call.
 * The caller must guarantee that objp points to a valid object previously
 * allocated with either kmalloc() or kmem_cache_alloc(). The object
 * must not be freed during the duration of the call.
 */
unsigned int ksize(const void *objp)
{
        if (unlikely(objp == NULL))
                return 0;

        return obj_size(virt_to_cache(objp));
}