mm/slab: avoid returning values by reference

[linux-2.6-block.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 initializations 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 'slab_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/slab.h>
#include        <linux/mm.h>
#include        <linux/poison.h>
#include        <linux/swap.h>
#include        <linux/cache.h>
#include        <linux/interrupt.h>
#include        <linux/init.h>
#include        <linux/compiler.h>
#include        <linux/cpuset.h>
#include        <linux/proc_fs.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/uaccess.h>
#include        <linux/nodemask.h>
#include        <linux/kmemleak.h>
#include        <linux/mempolicy.h>
#include        <linux/mutex.h>
#include        <linux/fault-inject.h>
#include        <linux/rtmutex.h>
#include        <linux/reciprocal_div.h>
#include        <linux/debugobjects.h>
#include        <linux/kmemcheck.h>
#include        <linux/memory.h>
#include        <linux/prefetch.h>

#include        <net/sock.h>

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

#include <trace/events/kmem.h>

#include        "internal.h"

#include        "slab.h"

/*
 * DEBUG        - 1 for kmem_cache_create() to honour; 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 *)
#define REDZONE_ALIGN           max(BYTES_PER_WORD, __alignof__(unsigned long long))

#ifndef ARCH_KMALLOC_FLAGS
#define ARCH_KMALLOC_FLAGS SLAB_HWCACHE_ALIGN
#endif

#define FREELIST_BYTE_INDEX (((PAGE_SIZE >> BITS_PER_BYTE) \
                                <= SLAB_OBJ_MIN_SIZE) ? 1 : 0)

#if FREELIST_BYTE_INDEX
typedef unsigned char freelist_idx_t;
#else
typedef unsigned short freelist_idx_t;
#endif

#define SLAB_OBJ_MAX_NUM ((1 << sizeof(freelist_idx_t) * BITS_PER_BYTE) - 1)

/*
 * true if a page was allocated from pfmemalloc reserves for network-based
 * swap
 */
static bool pfmemalloc_active __read_mostly;

/*
 * 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;
        void *entry[];  /*
                         * Must have this definition in here for the proper
                         * alignment of array_cache. Also simplifies accessing
                         * the entries.
                         *
                         * Entries should not be directly dereferenced as
                         * entries belonging to slabs marked pfmemalloc will
                         * have the lower bits set SLAB_OBJ_PFMEMALLOC
                         */
};

struct alien_cache {
        spinlock_t lock;
        struct array_cache ac;
};

#define SLAB_OBJ_PFMEMALLOC     1
static inline bool is_obj_pfmemalloc(void *objp)
{
        return (unsigned long)objp & SLAB_OBJ_PFMEMALLOC;
}

static inline void set_obj_pfmemalloc(void **objp)
{
        *objp = (void *)((unsigned long)*objp | SLAB_OBJ_PFMEMALLOC);
        return;
}

static inline void clear_obj_pfmemalloc(void **objp)
{
        *objp = (void *)((unsigned long)*objp & ~SLAB_OBJ_PFMEMALLOC);
}

/*
 * Need this for bootstrapping a per node allocator.
 */
#define NUM_INIT_LISTS (2 * MAX_NUMNODES)
static struct kmem_cache_node __initdata init_kmem_cache_node[NUM_INIT_LISTS];
#define CACHE_CACHE 0
#define SIZE_NODE (MAX_NUMNODES)

static int drain_freelist(struct kmem_cache *cache,
                        struct kmem_cache_node *n, int tofree);
static void free_block(struct kmem_cache *cachep, void **objpp, int len,
                        int node, struct list_head *list);
static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list);
static int enable_cpucache(struct kmem_cache *cachep, gfp_t gfp);
static void cache_reap(struct work_struct *unused);

static int slab_early_init = 1;

#define INDEX_NODE kmalloc_index(sizeof(struct kmem_cache_node))

static void kmem_cache_node_init(struct kmem_cache_node *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(&get_node(cachep, 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)

#define CFLGS_OBJFREELIST_SLAB  (0x40000000UL)
#define CFLGS_OFF_SLAB          (0x80000000UL)
#define OBJFREELIST_SLAB(x)     ((x)->flags & CFLGS_OBJFREELIST_SLAB)
#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_AC          (2*HZ)
#define REAPTIMEOUT_NODE        (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_ADD_REAPED(x,y)   ((x)->reaped += (y))
#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_INC_ACOVERFLOW(x)   ((x)->node_overflow++)
#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_ADD_REAPED(x,y)   do { (void)(y); } 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_INC_ACOVERFLOW(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

/*
 * 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->size - 2* BYTES_PER_WORD: redzone word [BYTES_PER_WORD long]
 * cachep->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 unsigned long long *dbg_redzone1(struct kmem_cache *cachep, void *objp)
{
        BUG_ON(!(cachep->flags & SLAB_RED_ZONE));
        return (unsigned long long*) (objp + obj_offset(cachep) -
                                      sizeof(unsigned long long));
}

static unsigned long 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 long *)(objp + cachep->size -
                                              sizeof(unsigned long long) -
                                              REDZONE_ALIGN);
        return (unsigned long long *) (objp + cachep->size -
                                       sizeof(unsigned long long));
}

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

#else

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

#endif

#ifdef CONFIG_DEBUG_SLAB_LEAK

static inline bool is_store_user_clean(struct kmem_cache *cachep)
{
        return atomic_read(&cachep->store_user_clean) == 1;
}

static inline void set_store_user_clean(struct kmem_cache *cachep)
{
        atomic_set(&cachep->store_user_clean, 1);
}

static inline void set_store_user_dirty(struct kmem_cache *cachep)
{
        if (is_store_user_clean(cachep))
                atomic_set(&cachep->store_user_clean, 0);
}

#else
static inline void set_store_user_dirty(struct kmem_cache *cachep) {}

#endif

/*
 * Do not go above this order unless 0 objects fit into the slab or
 * overridden on the command line.
 */
#define SLAB_MAX_ORDER_HI       1
#define SLAB_MAX_ORDER_LO       0
static int slab_max_order = SLAB_MAX_ORDER_LO;
static bool slab_max_order_set __initdata;

static inline struct kmem_cache *virt_to_cache(const void *obj)
{
        struct page *page = virt_to_head_page(obj);
        return page->slab_cache;
}

static inline void *index_to_obj(struct kmem_cache *cache, struct page *page,
                                 unsigned int idx)
{
        return page->s_mem + cache->size * idx;
}

/*
 * We want to avoid an expensive divide : (offset / cache->size)
 *   Using the fact that size is a constant for a particular cache,
 *   we can replace (offset / cache->size) by
 *   reciprocal_divide(offset, cache->reciprocal_buffer_size)
 */
static inline unsigned int obj_to_index(const struct kmem_cache *cache,
                                        const struct page *page, void *obj)
{
        u32 offset = (obj - page->s_mem);
        return reciprocal_divide(offset, cache->reciprocal_buffer_size);
}

#define BOOT_CPUCACHE_ENTRIES   1
/* internal cache of cache description objs */
static struct kmem_cache kmem_cache_boot = {
        .batchcount = 1,
        .limit = BOOT_CPUCACHE_ENTRIES,
        .shared = 1,
        .size = sizeof(struct kmem_cache),
        .name = "kmem_cache",
};

#define BAD_ALIEN_MAGIC 0x01020304ul

static DEFINE_PER_CPU(struct delayed_work, slab_reap_work);

static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
{
        return this_cpu_ptr(cachep->cpu_cache);
}

/*
 * Calculate the number of objects and left-over bytes for a given buffer size.
 */
static unsigned int cache_estimate(unsigned long gfporder, size_t buffer_size,
                unsigned long flags, size_t *left_over)
{
        unsigned int num;
        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:
         *
         * - @buffer_size bytes for each object
         * - One freelist_idx_t for each object
         *
         * We don't need to consider alignment of freelist because
         * freelist will be at the end of slab page. The objects will be
         * at the correct alignment.
         *
         * 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_OBJFREELIST_SLAB | CFLGS_OFF_SLAB)) {
                num = slab_size / buffer_size;
                *left_over = slab_size % buffer_size;
        } else {
                num = slab_size / (buffer_size + sizeof(freelist_idx_t));
                *left_over = slab_size %
                        (buffer_size + sizeof(freelist_idx_t));
        }

        return num;
}

#if DEBUG
#define slab_error(cachep, msg) __slab_error(__func__, 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();
        add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
}
#endif

/*
 * By default on NUMA we use alien caches to stage the freeing of
 * objects allocated from other nodes. This causes massive memory
 * inefficiencies when using fake NUMA setup to split memory into a
 * large number of small nodes, so it can be disabled on the command
 * line
  */

static int use_alien_caches __read_mostly = 1;
static int __init noaliencache_setup(char *s)
{
        use_alien_caches = 0;
        return 1;
}
__setup("noaliencache", noaliencache_setup);

static int __init slab_max_order_setup(char *str)
{
        get_option(&str, &slab_max_order);
        slab_max_order = slab_max_order < 0 ? 0 :
                                min(slab_max_order, MAX_ORDER - 1);
        slab_max_order_set = true;

        return 1;
}
__setup("slab_max_order=", slab_max_order_setup);

#ifdef CONFIG_NUMA
/*
 * Special reaping functions for NUMA systems called from cache_reap().
 * These take care of doing round robin flushing of alien caches (containing
 * objects freed on different nodes from which they were allocated) and the
 * flushing of remote pcps by calling drain_node_pages.
 */
static DEFINE_PER_CPU(unsigned long, slab_reap_node);

static void init_reap_node(int cpu)
{
        int node;

        node = next_node(cpu_to_mem(cpu), node_online_map);
        if (node == MAX_NUMNODES)
                node = first_node(node_online_map);

        per_cpu(slab_reap_node, cpu) = node;
}

static void next_reap_node(void)
{
        int node = __this_cpu_read(slab_reap_node);

        node = next_node(node, node_online_map);
        if (unlikely(node >= MAX_NUMNODES))
                node = first_node(node_online_map);
        __this_cpu_write(slab_reap_node, node);
}

#else
#define init_reap_node(cpu) do { } while (0)
#define next_reap_node(void) do { } while (0)
#endif

/*
 * 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 start_cpu_timer(int cpu)
{
        struct delayed_work *reap_work = &per_cpu(slab_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->work.func == NULL) {
                init_reap_node(cpu);
                INIT_DEFERRABLE_WORK(reap_work, cache_reap);
                schedule_delayed_work_on(cpu, reap_work,
                                        __round_jiffies_relative(HZ, cpu));
        }
}

static void init_arraycache(struct array_cache *ac, int limit, int batch)
{
        /*
         * The array_cache structures contain pointers to free object.
         * However, when such objects are allocated or transferred to another
         * cache the pointers are not cleared and they could be counted as
         * valid references during a kmemleak scan. Therefore, kmemleak must
         * not scan such objects.
         */
        kmemleak_no_scan(ac);
        if (ac) {
                ac->avail = 0;
                ac->limit = limit;
                ac->batchcount = batch;
                ac->touched = 0;
        }
}

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

        ac = kmalloc_node(memsize, gfp, node);
        init_arraycache(ac, entries, batchcount);
        return ac;
}

static inline bool is_slab_pfmemalloc(struct page *page)
{
        return PageSlabPfmemalloc(page);
}

/* Clears pfmemalloc_active if no slabs have pfmalloc set */
static void recheck_pfmemalloc_active(struct kmem_cache *cachep,
                                                struct array_cache *ac)
{
        struct kmem_cache_node *n = get_node(cachep, numa_mem_id());
        struct page *page;
        unsigned long flags;

        if (!pfmemalloc_active)
                return;

        spin_lock_irqsave(&n->list_lock, flags);
        list_for_each_entry(page, &n->slabs_full, lru)
                if (is_slab_pfmemalloc(page))
                        goto out;

        list_for_each_entry(page, &n->slabs_partial, lru)
                if (is_slab_pfmemalloc(page))
                        goto out;

        list_for_each_entry(page, &n->slabs_free, lru)
                if (is_slab_pfmemalloc(page))
                        goto out;

        pfmemalloc_active = false;
out:
        spin_unlock_irqrestore(&n->list_lock, flags);
}

static void *__ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac,
                                                gfp_t flags, bool force_refill)
{
        int i;
        void *objp = ac->entry[--ac->avail];

        /* Ensure the caller is allowed to use objects from PFMEMALLOC slab */
        if (unlikely(is_obj_pfmemalloc(objp))) {
                struct kmem_cache_node *n;

                if (gfp_pfmemalloc_allowed(flags)) {
                        clear_obj_pfmemalloc(&objp);
                        return objp;
                }

                /* The caller cannot use PFMEMALLOC objects, find another one */
                for (i = 0; i < ac->avail; i++) {
                        /* If a !PFMEMALLOC object is found, swap them */
                        if (!is_obj_pfmemalloc(ac->entry[i])) {
                                objp = ac->entry[i];
                                ac->entry[i] = ac->entry[ac->avail];
                                ac->entry[ac->avail] = objp;
                                return objp;
                        }
                }

                /*
                 * If there are empty slabs on the slabs_free list and we are
                 * being forced to refill the cache, mark this one !pfmemalloc.
                 */
                n = get_node(cachep, numa_mem_id());
                if (!list_empty(&n->slabs_free) && force_refill) {
                        struct page *page = virt_to_head_page(objp);
                        ClearPageSlabPfmemalloc(page);
                        clear_obj_pfmemalloc(&objp);
                        recheck_pfmemalloc_active(cachep, ac);
                        return objp;
                }

                /* No !PFMEMALLOC objects available */
                ac->avail++;
                objp = NULL;
        }

        return objp;
}

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

        if (unlikely(sk_memalloc_socks()))
                objp = __ac_get_obj(cachep, ac, flags, force_refill);
        else
                objp = ac->entry[--ac->avail];

        return objp;
}

static noinline void *__ac_put_obj(struct kmem_cache *cachep,
                        struct array_cache *ac, void *objp)
{
        if (unlikely(pfmemalloc_active)) {
                /* Some pfmemalloc slabs exist, check if this is one */
                struct page *page = virt_to_head_page(objp);
                if (PageSlabPfmemalloc(page))
                        set_obj_pfmemalloc(&objp);
        }

        return objp;
}

static inline void ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac,
                                                                void *objp)
{
        if (unlikely(sk_memalloc_socks()))
                objp = __ac_put_obj(cachep, ac, objp);

        ac->entry[ac->avail++] = objp;
}

/*
 * Transfer objects in one arraycache to another.
 * Locking must be handled by the caller.
 *
 * Return the number of entries transferred.
 */
static int transfer_objects(struct array_cache *to,
                struct array_cache *from, unsigned int max)
{
        /* Figure out how many entries to transfer */
        int nr = min3(from->avail, max, to->limit - to->avail);

        if (!nr)
                return 0;

        memcpy(to->entry + to->avail, from->entry + from->avail -nr,
                        sizeof(void *) *nr);

        from->avail -= nr;
        to->avail += nr;
        return nr;
}

#ifndef CONFIG_NUMA

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

static inline struct alien_cache **alloc_alien_cache(int node,
                                                int limit, gfp_t gfp)
{
        return (struct alien_cache **)BAD_ALIEN_MAGIC;
}

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

static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
{
        return 0;
}

static inline void *alternate_node_alloc(struct kmem_cache *cachep,
                gfp_t flags)
{
        return NULL;
}

static inline void *____cache_alloc_node(struct kmem_cache *cachep,
                 gfp_t flags, int nodeid)
{
        return NULL;
}

static inline gfp_t gfp_exact_node(gfp_t flags)
{
        return flags;
}

#else   /* CONFIG_NUMA */

static void *____cache_alloc_node(struct kmem_cache *, gfp_t, int);
static void *alternate_node_alloc(struct kmem_cache *, gfp_t);

static struct alien_cache *__alloc_alien_cache(int node, int entries,
                                                int batch, gfp_t gfp)
{
        size_t memsize = sizeof(void *) * entries + sizeof(struct alien_cache);
        struct alien_cache *alc = NULL;

        alc = kmalloc_node(memsize, gfp, node);
        init_arraycache(&alc->ac, entries, batch);
        spin_lock_init(&alc->lock);
        return alc;
}

static struct alien_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
{
        struct alien_cache **alc_ptr;
        size_t memsize = sizeof(void *) * nr_node_ids;
        int i;

        if (limit > 1)
                limit = 12;
        alc_ptr = kzalloc_node(memsize, gfp, node);
        if (!alc_ptr)
                return NULL;

        for_each_node(i) {
                if (i == node || !node_online(i))
                        continue;
                alc_ptr[i] = __alloc_alien_cache(node, limit, 0xbaadf00d, gfp);
                if (!alc_ptr[i]) {
                        for (i--; i >= 0; i--)
                                kfree(alc_ptr[i]);
                        kfree(alc_ptr);
                        return NULL;
                }
        }
        return alc_ptr;
}

static void free_alien_cache(struct alien_cache **alc_ptr)
{
        int i;

        if (!alc_ptr)
                return;
        for_each_node(i)
            kfree(alc_ptr[i]);
        kfree(alc_ptr);
}

static void __drain_alien_cache(struct kmem_cache *cachep,
                                struct array_cache *ac, int node,
                                struct list_head *list)
{
        struct kmem_cache_node *n = get_node(cachep, node);

        if (ac->avail) {
                spin_lock(&n->list_lock);
                /*
                 * Stuff objects into the remote nodes shared array first.
                 * That way we could avoid the overhead of putting the objects
                 * into the free lists and getting them back later.
                 */
                if (n->shared)
                        transfer_objects(n->shared, ac, ac->limit);

                free_block(cachep, ac->entry, ac->avail, node, list);
                ac->avail = 0;
                spin_unlock(&n->list_lock);
        }
}

/*
 * Called from cache_reap() to regularly drain alien caches round robin.
 */
static void reap_alien(struct kmem_cache *cachep, struct kmem_cache_node *n)
{
        int node = __this_cpu_read(slab_reap_node);

        if (n->alien) {
                struct alien_cache *alc = n->alien[node];
                struct array_cache *ac;

                if (alc) {
                        ac = &alc->ac;
                        if (ac->avail && spin_trylock_irq(&alc->lock)) {
                                LIST_HEAD(list);

                                __drain_alien_cache(cachep, ac, node, &list);
                                spin_unlock_irq(&alc->lock);
                                slabs_destroy(cachep, &list);
                        }
                }
        }
}

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

        for_each_online_node(i) {
                alc = alien[i];
                if (alc) {
                        LIST_HEAD(list);

                        ac = &alc->ac;
                        spin_lock_irqsave(&alc->lock, flags);
                        __drain_alien_cache(cachep, ac, i, &list);
                        spin_unlock_irqrestore(&alc->lock, flags);
                        slabs_destroy(cachep, &list);
                }
        }
}

static int __cache_free_alien(struct kmem_cache *cachep, void *objp,
                                int node, int page_node)
{
        struct kmem_cache_node *n;
        struct alien_cache *alien = NULL;
        struct array_cache *ac;
        LIST_HEAD(list);

        n = get_node(cachep, node);
        STATS_INC_NODEFREES(cachep);
        if (n->alien && n->alien[page_node]) {
                alien = n->alien[page_node];
                ac = &alien->ac;
                spin_lock(&alien->lock);
                if (unlikely(ac->avail == ac->limit)) {
                        STATS_INC_ACOVERFLOW(cachep);
                        __drain_alien_cache(cachep, ac, page_node, &list);
                }
                ac_put_obj(cachep, ac, objp);
                spin_unlock(&alien->lock);
                slabs_destroy(cachep, &list);
        } else {
                n = get_node(cachep, page_node);
                spin_lock(&n->list_lock);
                free_block(cachep, &objp, 1, page_node, &list);
                spin_unlock(&n->list_lock);
                slabs_destroy(cachep, &list);
        }
        return 1;
}

static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
{
        int page_node = page_to_nid(virt_to_page(objp));
        int node = numa_mem_id();
        /*
         * Make sure we are not freeing a object from another node to the array
         * cache on this cpu.
         */
        if (likely(node == page_node))
                return 0;

        return __cache_free_alien(cachep, objp, node, page_node);
}

/*
 * Construct gfp mask to allocate from a specific node but do not direct reclaim
 * or warn about failures. kswapd may still wake to reclaim in the background.
 */
static inline gfp_t gfp_exact_node(gfp_t flags)
{
        return (flags | __GFP_THISNODE | __GFP_NOWARN) & ~__GFP_DIRECT_RECLAIM;
}
#endif

/*
 * Allocates and initializes node for a node on each slab cache, used for
 * either memory or cpu hotplug.  If memory is being hot-added, the kmem_cache_node
 * will be allocated off-node since memory is not yet online for the new node.
 * When hotplugging memory or a cpu, existing node are not replaced if
 * already in use.
 *
 * Must hold slab_mutex.
 */
static int init_cache_node_node(int node)
{
        struct kmem_cache *cachep;
        struct kmem_cache_node *n;
        const size_t memsize = sizeof(struct kmem_cache_node);

        list_for_each_entry(cachep, &slab_caches, list) {
                /*
                 * Set up the kmem_cache_node for cpu before we can
                 * begin anything. Make sure some other cpu on this
                 * node has not already allocated this
                 */
                n = get_node(cachep, node);
                if (!n) {
                        n = kmalloc_node(memsize, GFP_KERNEL, node);
                        if (!n)
                                return -ENOMEM;
                        kmem_cache_node_init(n);
                        n->next_reap = jiffies + REAPTIMEOUT_NODE +
                            ((unsigned long)cachep) % REAPTIMEOUT_NODE;

                        /*
                         * The kmem_cache_nodes don't come and go as CPUs
                         * come and go.  slab_mutex is sufficient
                         * protection here.
                         */
                        cachep->node[node] = n;
                }

                spin_lock_irq(&n->list_lock);
                n->free_limit =
                        (1 + nr_cpus_node(node)) *
                        cachep->batchcount + cachep->num;
                spin_unlock_irq(&n->list_lock);
        }
        return 0;
}

static inline int slabs_tofree(struct kmem_cache *cachep,
                                                struct kmem_cache_node *n)
{
        return (n->free_objects + cachep->num - 1) / cachep->num;
}

static void cpuup_canceled(long cpu)
{
        struct kmem_cache *cachep;
        struct kmem_cache_node *n = NULL;
        int node = cpu_to_mem(cpu);
        const struct cpumask *mask = cpumask_of_node(node);

        list_for_each_entry(cachep, &slab_caches, list) {
                struct array_cache *nc;
                struct array_cache *shared;
                struct alien_cache **alien;
                LIST_HEAD(list);

                n = get_node(cachep, node);
                if (!n)
                        continue;

                spin_lock_irq(&n->list_lock);

                /* Free limit for this kmem_cache_node */
                n->free_limit -= cachep->batchcount;

                /* cpu is dead; no one can alloc from it. */
                nc = per_cpu_ptr(cachep->cpu_cache, cpu);
                if (nc) {
                        free_block(cachep, nc->entry, nc->avail, node, &list);
                        nc->avail = 0;
                }

                if (!cpumask_empty(mask)) {
                        spin_unlock_irq(&n->list_lock);
                        goto free_slab;
                }

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

                alien = n->alien;
                n->alien = NULL;

                spin_unlock_irq(&n->list_lock);

                kfree(shared);
                if (alien) {
                        drain_alien_cache(cachep, alien);
                        free_alien_cache(alien);
                }

free_slab:
                slabs_destroy(cachep, &list);
        }
        /*
         * 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, &slab_caches, list) {
                n = get_node(cachep, node);
                if (!n)
                        continue;
                drain_freelist(cachep, n, slabs_tofree(cachep, n));
        }
}

static int cpuup_prepare(long cpu)
{
        struct kmem_cache *cachep;
        struct kmem_cache_node *n = NULL;
        int node = cpu_to_mem(cpu);
        int err;

        /*
         * 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_cache_node and not this cpu's kmem_cache_node
         */
        err = init_cache_node_node(node);
        if (err < 0)
                goto bad;

        /*
         * Now we can go ahead with allocating the shared arrays and
         * array caches
         */
        list_for_each_entry(cachep, &slab_caches, list) {
                struct array_cache *shared = NULL;
                struct alien_cache **alien = NULL;

                if (cachep->shared) {
                        shared = alloc_arraycache(node,
                                cachep->shared * cachep->batchcount,
                                0xbaadf00d, GFP_KERNEL);
                        if (!shared)
                                goto bad;
                }
                if (use_alien_caches) {
                        alien = alloc_alien_cache(node, cachep->limit, GFP_KERNEL);
                        if (!alien) {
                                kfree(shared);
                                goto bad;
                        }
                }
                n = get_node(cachep, node);
                BUG_ON(!n);

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

        return 0;
bad:
        cpuup_canceled(cpu);
        return -ENOMEM;
}

static int cpuup_callback(struct notifier_block *nfb,
                                    unsigned long action, void *hcpu)
{
        long cpu = (long)hcpu;
        int err = 0;

        switch (action) {
        case CPU_UP_PREPARE:
        case CPU_UP_PREPARE_FROZEN:
                mutex_lock(&slab_mutex);
                err = cpuup_prepare(cpu);
                mutex_unlock(&slab_mutex);
                break;
        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
                start_cpu_timer(cpu);
                break;
#ifdef CONFIG_HOTPLUG_CPU
        case CPU_DOWN_PREPARE:
        case CPU_DOWN_PREPARE_FROZEN:
                /*
                 * Shutdown cache reaper. Note that the slab_mutex is
                 * held so that if cache_reap() is invoked it cannot do
                 * anything expensive but will only modify reap_work
                 * and reschedule the timer.
                */
                cancel_delayed_work_sync(&per_cpu(slab_reap_work, cpu));
                /* Now the cache_reaper is guaranteed to be not running. */
                per_cpu(slab_reap_work, cpu).work.func = NULL;
                break;
        case CPU_DOWN_FAILED:
        case CPU_DOWN_FAILED_FROZEN:
                start_cpu_timer(cpu);
                break;
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                /*
                 * Even if all the cpus of a node are down, we don't free the
                 * kmem_cache_node 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 node
                 * structure is usually allocated from kmem_cache_create() and
                 * gets destroyed at kmem_cache_destroy().
                 */
                /* fall through */
#endif
        case CPU_UP_CANCELED:
        case CPU_UP_CANCELED_FROZEN:
                mutex_lock(&slab_mutex);
                cpuup_canceled(cpu);
                mutex_unlock(&slab_mutex);
                break;
        }
        return notifier_from_errno(err);
}

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

#if defined(CONFIG_NUMA) && defined(CONFIG_MEMORY_HOTPLUG)
/*
 * Drains freelist for a node on each slab cache, used for memory hot-remove.
 * Returns -EBUSY if all objects cannot be drained so that the node is not
 * removed.
 *
 * Must hold slab_mutex.
 */
static int __meminit drain_cache_node_node(int node)
{
        struct kmem_cache *cachep;
        int ret = 0;

        list_for_each_entry(cachep, &slab_caches, list) {
                struct kmem_cache_node *n;

                n = get_node(cachep, node);
                if (!n)
                        continue;

                drain_freelist(cachep, n, slabs_tofree(cachep, n));

                if (!list_empty(&n->slabs_full) ||
                    !list_empty(&n->slabs_partial)) {
                        ret = -EBUSY;
                        break;
                }
        }
        return ret;
}

static int __meminit slab_memory_callback(struct notifier_block *self,
                                        unsigned long action, void *arg)
{
        struct memory_notify *mnb = arg;
        int ret = 0;
        int nid;

        nid = mnb->status_change_nid;
        if (nid < 0)
                goto out;

        switch (action) {
        case MEM_GOING_ONLINE:
                mutex_lock(&slab_mutex);
                ret = init_cache_node_node(nid);
                mutex_unlock(&slab_mutex);
                break;
        case MEM_GOING_OFFLINE:
                mutex_lock(&slab_mutex);
                ret = drain_cache_node_node(nid);
                mutex_unlock(&slab_mutex);
                break;
        case MEM_ONLINE:
        case MEM_OFFLINE:
        case MEM_CANCEL_ONLINE:
        case MEM_CANCEL_OFFLINE:
                break;
        }
out:
        return notifier_from_errno(ret);
}
#endif /* CONFIG_NUMA && CONFIG_MEMORY_HOTPLUG */

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

        ptr = kmalloc_node(sizeof(struct kmem_cache_node), GFP_NOWAIT, nodeid);
        BUG_ON(!ptr);

        memcpy(ptr, list, sizeof(struct kmem_cache_node));
        /*
         * Do not assume that spinlocks can be initialized via memcpy:
         */
        spin_lock_init(&ptr->list_lock);

        MAKE_ALL_LISTS(cachep, ptr, nodeid);
        cachep->node[nodeid] = ptr;
}

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

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

/*
 * Initialisation.  Called after the page allocator have been initialised and
 * before smp_init().
 */
void __init kmem_cache_init(void)
{
        int i;

        BUILD_BUG_ON(sizeof(((struct page *)NULL)->lru) <
                                        sizeof(struct rcu_head));
        kmem_cache = &kmem_cache_boot;

        if (num_possible_nodes() == 1)
                use_alien_caches = 0;

        for (i = 0; i < NUM_INIT_LISTS; i++)
                kmem_cache_node_init(&init_kmem_cache_node[i]);

        /*
         * Fragmentation resistance on low memory - only use bigger
         * page orders on machines with more than 32MB of memory if
         * not overridden on the command line.
         */
        if (!slab_max_order_set && totalram_pages > (32 << 20) >> PAGE_SHIFT)
                slab_max_order = SLAB_MAX_ORDER_HI;

        /* Bootstrap is tricky, because several objects are allocated
         * from caches that do not exist yet:
         * 1) initialize the kmem_cache cache: it contains the struct
         *    kmem_cache structures of all caches, except kmem_cache itself:
         *    kmem_cache is statically allocated.
         *    Initially an __init data area is used for the head array and the
         *    kmem_cache_node 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 kmem_cache and the first
         *    kmalloc cache with kmalloc allocated arrays.
         * 5) Replace the __init data for kmem_cache_node for kmem_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 kmem_cache */

        /*
         * struct kmem_cache size depends on nr_node_ids & nr_cpu_ids
         */
        create_boot_cache(kmem_cache, "kmem_cache",
                offsetof(struct kmem_cache, node) +
                                  nr_node_ids * sizeof(struct kmem_cache_node *),
                                  SLAB_HWCACHE_ALIGN);
        list_add(&kmem_cache->list, &slab_caches);
        slab_state = PARTIAL;

        /*
         * Initialize the caches that provide memory for the  kmem_cache_node
         * structures first.  Without this, further allocations will bug.
         */
        kmalloc_caches[INDEX_NODE] = create_kmalloc_cache("kmalloc-node",
                                kmalloc_size(INDEX_NODE), ARCH_KMALLOC_FLAGS);
        slab_state = PARTIAL_NODE;
        setup_kmalloc_cache_index_table();

        slab_early_init = 0;

        /* 5) Replace the bootstrap kmem_cache_node */
        {
                int nid;

                for_each_online_node(nid) {
                        init_list(kmem_cache, &init_kmem_cache_node[CACHE_CACHE + nid], nid);

                        init_list(kmalloc_caches[INDEX_NODE],
                                          &init_kmem_cache_node[SIZE_NODE + nid], nid);
                }
        }

        create_kmalloc_caches(ARCH_KMALLOC_FLAGS);
}

void __init kmem_cache_init_late(void)
{
        struct kmem_cache *cachep;

        slab_state = UP;

        /* 6) resize the head arrays to their final sizes */
        mutex_lock(&slab_mutex);
        list_for_each_entry(cachep, &slab_caches, list)
                if (enable_cpucache(cachep, GFP_NOWAIT))
                        BUG();
        mutex_unlock(&slab_mutex);

        /* Done! */
        slab_state = FULL;

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

#ifdef CONFIG_NUMA
        /*
         * Register a memory hotplug callback that initializes and frees
         * node.
         */
        hotplug_memory_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);
#endif

        /*
         * 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 the page allocator
         */
        for_each_online_cpu(cpu)
                start_cpu_timer(cpu);

        /* Done! */
        slab_state = FULL;
        return 0;
}
__initcall(cpucache_init);

static noinline void
slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid)
{
#if DEBUG
        struct kmem_cache_node *n;
        struct page *page;
        unsigned long flags;
        int node;
        static DEFINE_RATELIMIT_STATE(slab_oom_rs, DEFAULT_RATELIMIT_INTERVAL,
                                      DEFAULT_RATELIMIT_BURST);

        if ((gfpflags & __GFP_NOWARN) || !__ratelimit(&slab_oom_rs))
                return;

        printk(KERN_WARNING
                "SLAB: Unable to allocate memory on node %d (gfp=0x%x)\n",
                nodeid, gfpflags);
        printk(KERN_WARNING "  cache: %s, object size: %d, order: %d\n",
                cachep->name, cachep->size, cachep->gfporder);

        for_each_kmem_cache_node(cachep, node, n) {
                unsigned long active_objs = 0, num_objs = 0, free_objects = 0;
                unsigned long active_slabs = 0, num_slabs = 0;

                spin_lock_irqsave(&n->list_lock, flags);
                list_for_each_entry(page, &n->slabs_full, lru) {
                        active_objs += cachep->num;
                        active_slabs++;
                }
                list_for_each_entry(page, &n->slabs_partial, lru) {
                        active_objs += page->active;
                        active_slabs++;
                }
                list_for_each_entry(page, &n->slabs_free, lru)
                        num_slabs++;

                free_objects += n->free_objects;
                spin_unlock_irqrestore(&n->list_lock, flags);

                num_slabs += active_slabs;
                num_objs = num_slabs * cachep->num;
                printk(KERN_WARNING
                        "  node %d: slabs: %ld/%ld, objs: %ld/%ld, free: %ld\n",
                        node, active_slabs, num_slabs, active_objs, num_objs,
                        free_objects);
        }
#endif
}

/*
 * Interface to system's page allocator. No need to hold the
 * kmem_cache_node ->list_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 struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
                                                                int nodeid)
{
        struct page *page;
        int nr_pages;

        flags |= cachep->allocflags;
        if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
                flags |= __GFP_RECLAIMABLE;

        page = __alloc_pages_node(nodeid, flags | __GFP_NOTRACK, cachep->gfporder);
        if (!page) {
                slab_out_of_memory(cachep, flags, nodeid);
                return NULL;
        }

        if (memcg_charge_slab(page, flags, cachep->gfporder, cachep)) {
                __free_pages(page, cachep->gfporder);
                return NULL;
        }

        /* Record if ALLOC_NO_WATERMARKS was set when allocating the slab */
        if (page_is_pfmemalloc(page))
                pfmemalloc_active = true;

        nr_pages = (1 << cachep->gfporder);
        if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
                add_zone_page_state(page_zone(page),
                        NR_SLAB_RECLAIMABLE, nr_pages);
        else
                add_zone_page_state(page_zone(page),
                        NR_SLAB_UNRECLAIMABLE, nr_pages);
        __SetPageSlab(page);
        if (page_is_pfmemalloc(page))
                SetPageSlabPfmemalloc(page);

        if (kmemcheck_enabled && !(cachep->flags & SLAB_NOTRACK)) {
                kmemcheck_alloc_shadow(page, cachep->gfporder, flags, nodeid);

                if (cachep->ctor)
                        kmemcheck_mark_uninitialized_pages(page, nr_pages);
                else
                        kmemcheck_mark_unallocated_pages(page, nr_pages);
        }

        return page;
}

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

        kmemcheck_free_shadow(page, cachep->gfporder);

        if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
                sub_zone_page_state(page_zone(page),
                                NR_SLAB_RECLAIMABLE, nr_freed);
        else
                sub_zone_page_state(page_zone(page),
                                NR_SLAB_UNRECLAIMABLE, nr_freed);

        BUG_ON(!PageSlab(page));
        __ClearPageSlabPfmemalloc(page);
        __ClearPageSlab(page);
        page_mapcount_reset(page);
        page->mapping = NULL;

        if (current->reclaim_state)
                current->reclaim_state->reclaimed_slab += nr_freed;
        __free_kmem_pages(page, cachep->gfporder);
}

static void kmem_rcu_free(struct rcu_head *head)
{
        struct kmem_cache *cachep;
        struct page *page;

        page = container_of(head, struct page, rcu_head);
        cachep = page->slab_cache;

        kmem_freepages(cachep, page);
}

#if DEBUG
static bool is_debug_pagealloc_cache(struct kmem_cache *cachep)
{
        if (debug_pagealloc_enabled() && OFF_SLAB(cachep) &&
                (cachep->size % PAGE_SIZE) == 0)
                return true;

        return false;
}

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

        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;
}

static void slab_kernel_map(struct kmem_cache *cachep, void *objp,
                                int map, unsigned long caller)
{
        if (!is_debug_pagealloc_cache(cachep))
                return;

        if (caller)
                store_stackinfo(cachep, objp, caller);

        kernel_map_pages(virt_to_page(objp), cachep->size / PAGE_SIZE, map);
}

#else
static inline void slab_kernel_map(struct kmem_cache *cachep, void *objp,
                                int map, unsigned long caller) {}

#endif

static void poison_obj(struct kmem_cache *cachep, void *addr, unsigned char val)
{
        int size = cachep->object_size;
        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;
        unsigned char error = 0;
        int bad_count = 0;

        printk(KERN_ERR "%03x: ", offset);
        for (i = 0; i < limit; i++) {
                if (data[offset + i] != POISON_FREE) {
                        error = data[offset + i];
                        bad_count++;
                }
        }
        print_hex_dump(KERN_CONT, "", 0, 16, 1,
                        &data[offset], limit, 1);

        if (bad_count == 1) {
                error ^= POISON_FREE;
                if (!(error & (error - 1))) {
                        printk(KERN_ERR "Single bit error detected. Probably "
                                        "bad RAM.\n");
#ifdef CONFIG_X86
                        printk(KERN_ERR "Run memtest86+ or a similar memory "
                                        "test tool.\n");
#else
                        printk(KERN_ERR "Run a memory test tool.\n");
#endif
                }
        }
}
#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%llx/0x%llx.\n",
                        *dbg_redzone1(cachep, objp),
                        *dbg_redzone2(cachep, objp));
        }

        if (cachep->flags & SLAB_STORE_USER) {
                printk(KERN_ERR "Last user: [<%p>](%pSR)\n",
                       *dbg_userword(cachep, objp),
                       *dbg_userword(cachep, objp));
        }
        realobj = (char *)objp + obj_offset(cachep);
        size = cachep->object_size;
        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;

        if (is_debug_pagealloc_cache(cachep))
                return;

        realobj = (char *)objp + obj_offset(cachep);
        size = cachep->object_size;

        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 (%s): %s start=%p, len=%d\n",
                                        print_tainted(), cachep->name, 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 page *page = virt_to_head_page(objp);
                unsigned int objnr;

                objnr = obj_to_index(cachep, page, objp);
                if (objnr) {
                        objp = index_to_obj(cachep, page, objnr - 1);
                        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 = index_to_obj(cachep, page, objnr + 1);
                        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
static void slab_destroy_debugcheck(struct kmem_cache *cachep,
                                                struct page *page)
{
        int i;

        if (OBJFREELIST_SLAB(cachep) && cachep->flags & SLAB_POISON) {
                poison_obj(cachep, page->freelist - obj_offset(cachep),
                        POISON_FREE);
        }

        for (i = 0; i < cachep->num; i++) {
                void *objp = index_to_obj(cachep, page, i);

                if (cachep->flags & SLAB_POISON) {
                        check_poison_obj(cachep, objp);
                        slab_kernel_map(cachep, objp, 1, 0);
                }
                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");
                }
        }
}
#else
static void slab_destroy_debugcheck(struct kmem_cache *cachep,
                                                struct page *page)
{
}
#endif

/**
 * slab_destroy - destroy and release all objects in a slab
 * @cachep: cache pointer being destroyed
 * @page: page pointer being destroyed
 *
 * Destroy all the objs in a slab page, and release the mem back to the system.
 * Before calling the slab page must have been unlinked from the cache. The
 * kmem_cache_node ->list_lock is not held/needed.
 */
static void slab_destroy(struct kmem_cache *cachep, struct page *page)
{
        void *freelist;

        freelist = page->freelist;
        slab_destroy_debugcheck(cachep, page);
        if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU))
                call_rcu(&page->rcu_head, kmem_rcu_free);
        else
                kmem_freepages(cachep, page);

        /*
         * From now on, we don't use freelist
         * although actual page can be freed in rcu context
         */
        if (OFF_SLAB(cachep))
                kmem_cache_free(cachep->freelist_cache, freelist);
}

static void slabs_destroy(struct kmem_cache *cachep, struct list_head *list)
{
        struct page *page, *n;

        list_for_each_entry_safe(page, n, list, lru) {
                list_del(&page->lru);
                slab_destroy(cachep, page);
        }
}

/**
 * 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.
 * @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 size_t calculate_slab_order(struct kmem_cache *cachep,
                                size_t size, unsigned long flags)
{
        size_t left_over = 0;
        int gfporder;

        for (gfporder = 0; gfporder <= KMALLOC_MAX_ORDER; gfporder++) {
                unsigned int num;
                size_t remainder;

                num = cache_estimate(gfporder, size, flags, &remainder);
                if (!num)
                        continue;

                /* Can't handle number of objects more than SLAB_OBJ_MAX_NUM */
                if (num > SLAB_OBJ_MAX_NUM)
                        break;

                if (flags & CFLGS_OFF_SLAB) {
                        struct kmem_cache *freelist_cache;
                        size_t freelist_size;

                        freelist_size = num * sizeof(freelist_idx_t);
                        freelist_cache = kmalloc_slab(freelist_size, 0u);
                        if (!freelist_cache)
                                continue;

                        /*
                         * Needed to avoid possible looping condition
                         * in cache_grow()
                         */
                        if (OFF_SLAB(freelist_cache))
                                continue;

                        /* check if off slab has enough benefit */
                        if (freelist_cache->size > cachep->size / 2)
                                continue;
                }

                /* Found something acceptable - save it away */
                cachep->num = num;
                cachep->gfporder = gfporder;
                left_over = remainder;

                /*
                 * 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.
                 */
                if (flags & SLAB_RECLAIM_ACCOUNT)
                        break;

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

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

static struct array_cache __percpu *alloc_kmem_cache_cpus(
                struct kmem_cache *cachep, int entries, int batchcount)
{
        int cpu;
        size_t size;
        struct array_cache __percpu *cpu_cache;

        size = sizeof(void *) * entries + sizeof(struct array_cache);
        cpu_cache = __alloc_percpu(size, sizeof(void *));

        if (!cpu_cache)
                return NULL;

        for_each_possible_cpu(cpu) {
                init_arraycache(per_cpu_ptr(cpu_cache, cpu),
                                entries, batchcount);
        }

        return cpu_cache;
}

static int __init_refok setup_cpu_cache(struct kmem_cache *cachep, gfp_t gfp)
{
        if (slab_state >= FULL)
                return enable_cpucache(cachep, gfp);

        cachep->cpu_cache = alloc_kmem_cache_cpus(cachep, 1, 1);
        if (!cachep->cpu_cache)
                return 1;

        if (slab_state == DOWN) {
                /* Creation of first cache (kmem_cache). */
                set_up_node(kmem_cache, CACHE_CACHE);
        } else if (slab_state == PARTIAL) {
                /* For kmem_cache_node */
                set_up_node(cachep, SIZE_NODE);
        } else {
                int node;

                for_each_online_node(node) {
                        cachep->node[node] = kmalloc_node(
                                sizeof(struct kmem_cache_node), gfp, node);
                        BUG_ON(!cachep->node[node]);
                        kmem_cache_node_init(cachep->node[node]);
                }
        }

        cachep->node[numa_mem_id()]->next_reap =
                        jiffies + REAPTIMEOUT_NODE +
                        ((unsigned long)cachep) % REAPTIMEOUT_NODE;

        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;
        return 0;
}

unsigned long kmem_cache_flags(unsigned long object_size,
        unsigned long flags, const char *name,
        void (*ctor)(void *))
{
        return flags;
}

struct kmem_cache *
__kmem_cache_alias(const char *name, size_t size, size_t align,
                   unsigned long flags, void (*ctor)(void *))
{
        struct kmem_cache *cachep;

        cachep = find_mergeable(size, align, flags, name, ctor);
        if (cachep) {
                cachep->refcount++;

                /*
                 * Adjust the object sizes so that we clear
                 * the complete object on kzalloc.
                 */
                cachep->object_size = max_t(int, cachep->object_size, size);
        }
        return cachep;
}

static bool set_objfreelist_slab_cache(struct kmem_cache *cachep,
                        size_t size, unsigned long flags)
{
        size_t left;

        cachep->num = 0;

        if (cachep->ctor || flags & SLAB_DESTROY_BY_RCU)
                return false;

        left = calculate_slab_order(cachep, size,
                        flags | CFLGS_OBJFREELIST_SLAB);
        if (!cachep->num)
                return false;

        if (cachep->num * sizeof(freelist_idx_t) > cachep->object_size)
                return false;

        cachep->colour = left / cachep->colour_off;

        return true;
}

static bool set_off_slab_cache(struct kmem_cache *cachep,
                        size_t size, unsigned long flags)
{
        size_t left;

        cachep->num = 0;

        /*
         * Always use on-slab management when SLAB_NOLEAKTRACE
         * to avoid recursive calls into kmemleak.
         */
        if (flags & SLAB_NOLEAKTRACE)
                return false;

        /*
         * Size is large, assume best to place the slab management obj
         * off-slab (should allow better packing of objs).
         */
        left = calculate_slab_order(cachep, size, flags | CFLGS_OFF_SLAB);
        if (!cachep->num)
                return false;

        /*
         * 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 (left >= cachep->num * sizeof(freelist_idx_t))
                return false;

        cachep->colour = left / cachep->colour_off;

        return true;
}

static bool set_on_slab_cache(struct kmem_cache *cachep,
                        size_t size, unsigned long flags)
{
        size_t left;

        cachep->num = 0;

        left = calculate_slab_order(cachep, size, flags);
        if (!cachep->num)
                return false;

        cachep->colour = left / cachep->colour_off;

        return true;
}

/**
 * __kmem_cache_create - Create a cache.
 * @cachep: cache management descriptor
 * @flags: SLAB flags
 *
 * 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.
 *
 * 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_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.
 */
int
__kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
{
        size_t ralign = BYTES_PER_WORD;
        gfp_t gfp;
        int err;
        size_t size = cachep->size;

#if DEBUG
#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 + REDZONE_ALIGN +
                                                2 * sizeof(unsigned long long)))
                flags |= SLAB_RED_ZONE | SLAB_STORE_USER;
        if (!(flags & SLAB_DESTROY_BY_RCU))
                flags |= SLAB_POISON;
#endif
#endif

        /*
         * 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);
        }

        if (flags & SLAB_RED_ZONE) {
                ralign = REDZONE_ALIGN;
                /* If redzoning, ensure that the second redzone is suitably
                 * aligned, by adjusting the object size accordingly. */
                size += REDZONE_ALIGN - 1;
                size &= ~(REDZONE_ALIGN - 1);
        }

        /* 3) caller mandated alignment */
        if (ralign < cachep->align) {
                ralign = cachep->align;
        }
        /* disable debug if necessary */
        if (ralign > __alignof__(unsigned long long))
                flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
        /*
         * 4) Store it.
         */
        cachep->align = ralign;
        cachep->colour_off = cache_line_size();
        /* Offset must be a multiple of the alignment. */
        if (cachep->colour_off < cachep->align)
                cachep->colour_off = cachep->align;

        if (slab_is_available())
                gfp = GFP_KERNEL;
        else
                gfp = GFP_NOWAIT;

#if DEBUG

        /*
         * Both debugging options require word-alignment which is calculated
         * into align above.
         */
        if (flags & SLAB_RED_ZONE) {
                /* add space for red zone words */
                cachep->obj_offset += sizeof(unsigned long long);
                size += 2 * sizeof(unsigned long long);
        }
        if (flags & SLAB_STORE_USER) {
                /* user store requires one word storage behind the end of
                 * the real object. But if the second red zone needs to be
                 * aligned to 64 bits, we must allow that much space.
                 */
                if (flags & SLAB_RED_ZONE)
                        size += REDZONE_ALIGN;
                else
                        size += BYTES_PER_WORD;
        }
#endif

        size = ALIGN(size, cachep->align);
        /*
         * We should restrict the number of objects in a slab to implement
         * byte sized index. Refer comment on SLAB_OBJ_MIN_SIZE definition.
         */
        if (FREELIST_BYTE_INDEX && size < SLAB_OBJ_MIN_SIZE)
                size = ALIGN(SLAB_OBJ_MIN_SIZE, cachep->align);

#if DEBUG
        /*
         * To activate debug pagealloc, off-slab management is necessary
         * requirement. In early phase of initialization, small sized slab
         * doesn't get initialized so it would not be possible. So, we need
         * to check size >= 256. It guarantees that all necessary small
         * sized slab is initialized in current slab initialization sequence.
         */
        if (debug_pagealloc_enabled() && (flags & SLAB_POISON) &&
                size >= 256 && cachep->object_size > cache_line_size()) {
                if (size < PAGE_SIZE || size % PAGE_SIZE == 0) {
                        size_t tmp_size = ALIGN(size, PAGE_SIZE);

                        if (set_off_slab_cache(cachep, tmp_size, flags)) {
                                flags |= CFLGS_OFF_SLAB;
                                cachep->obj_offset += tmp_size - size;
                                size = tmp_size;
                                goto done;
                        }
                }
        }
#endif

        if (set_objfreelist_slab_cache(cachep, size, flags)) {
                flags |= CFLGS_OBJFREELIST_SLAB;
                goto done;
        }

        if (set_off_slab_cache(cachep, size, flags)) {
                flags |= CFLGS_OFF_SLAB;
                goto done;
        }

        if (set_on_slab_cache(cachep, size, flags))
                goto done;

        return -E2BIG;

done:
        cachep->freelist_size = cachep->num * sizeof(freelist_idx_t);
        cachep->flags = flags;
        cachep->allocflags = __GFP_COMP;
        if (CONFIG_ZONE_DMA_FLAG && (flags & SLAB_CACHE_DMA))
                cachep->allocflags |= GFP_DMA;
        cachep->size = size;
        cachep->reciprocal_buffer_size = reciprocal_value(size);

#if DEBUG
        /*
         * If we're going to use the generic kernel_map_pages()
         * poisoning, then it's going to smash the contents of
         * the redzone and userword anyhow, so switch them off.
         */
        if (IS_ENABLED(CONFIG_PAGE_POISONING) &&
                (cachep->flags & SLAB_POISON) &&
                is_debug_pagealloc_cache(cachep))
                cachep->flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
#endif

        if (OFF_SLAB(cachep)) {
                cachep->freelist_cache =
                        kmalloc_slab(cachep->freelist_size, 0u);
        }

        err = setup_cpu_cache(cachep, gfp);
        if (err) {
                __kmem_cache_release(cachep);
                return err;
        }

        return 0;
}

#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(&get_node(cachep, numa_mem_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(&get_node(cachep, 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

static void drain_array(struct kmem_cache *cachep, struct kmem_cache_node *n,
                        struct array_cache *ac,
                        int force, int node);

static void do_drain(void *arg)
{
        struct kmem_cache *cachep = arg;
        struct array_cache *ac;
        int node = numa_mem_id();
        struct kmem_cache_node *n;
        LIST_HEAD(list);

        check_irq_off();
        ac = cpu_cache_get(cachep);
        n = get_node(cachep, node);
        spin_lock(&n->list_lock);
        free_block(cachep, ac->entry, ac->avail, node, &list);
        spin_unlock(&n->list_lock);
        slabs_destroy(cachep, &list);
        ac->avail = 0;
}

static void drain_cpu_caches(struct kmem_cache *cachep)
{
        struct kmem_cache_node *n;
        int node;

        on_each_cpu(do_drain, cachep, 1);
        check_irq_on();
        for_each_kmem_cache_node(cachep, node, n)
                if (n->alien)
                        drain_alien_cache(cachep, n->alien);

        for_each_kmem_cache_node(cachep, node, n)
                drain_array(cachep, n, n->shared, 1, node);
}

/*
 * Remove slabs from the list of free slabs.
 * Specify the number of slabs to drain in tofree.
 *
 * Returns the actual number of slabs released.
 */
static int drain_freelist(struct kmem_cache *cache,
                        struct kmem_cache_node *n, int tofree)
{
        struct list_head *p;
        int nr_freed;
        struct page *page;

        nr_freed = 0;
        while (nr_freed < tofree && !list_empty(&n->slabs_free)) {

                spin_lock_irq(&n->list_lock);
                p = n->slabs_free.prev;
                if (p == &n->slabs_free) {
                        spin_unlock_irq(&n->list_lock);
                        goto out;
                }

                page = list_entry(p, struct page, lru);
                list_del(&page->lru);
                /*
                 * Safe to drop the lock. The slab is no longer linked
                 * to the cache.
                 */
                n->free_objects -= cache->num;
                spin_unlock_irq(&n->list_lock);
                slab_destroy(cache, page);
                nr_freed++;
        }
out:
        return nr_freed;
}

int __kmem_cache_shrink(struct kmem_cache *cachep, bool deactivate)
{
        int ret = 0;
        int node;
        struct kmem_cache_node *n;

        drain_cpu_caches(cachep);

        check_irq_on();
        for_each_kmem_cache_node(cachep, node, n) {
                drain_freelist(cachep, n, slabs_tofree(cachep, n));

                ret += !list_empty(&n->slabs_full) ||
                        !list_empty(&n->slabs_partial);
        }
        return (ret ? 1 : 0);
}

int __kmem_cache_shutdown(struct kmem_cache *cachep)
{
        return __kmem_cache_shrink(cachep, false);
}

void __kmem_cache_release(struct kmem_cache *cachep)
{
        int i;
        struct kmem_cache_node *n;

        free_percpu(cachep->cpu_cache);

        /* NUMA: free the node structures */
        for_each_kmem_cache_node(cachep, i, n) {
                kfree(n->shared);
                free_alien_cache(n->alien);
                kfree(n);
                cachep->node[i] = NULL;
        }
}

/*
 * Get the memory for a slab management obj.
 *
 * For a slab cache when the slab descriptor is off-slab, the
 * slab descriptor can't come from the same cache which is being created,
 * Because if it is the case, that means we defer the creation of
 * the kmalloc_{dma,}_cache of size sizeof(slab descriptor) to this point.
 * And we eventually call down to __kmem_cache_create(), which
 * in turn looks up in the kmalloc_{dma,}_caches for the disired-size one.
 * This is a "chicken-and-egg" problem.
 *
 * So the off-slab slab descriptor shall come from the kmalloc_{dma,}_caches,
 * which are all initialized during kmem_cache_init().
 */
static void *alloc_slabmgmt(struct kmem_cache *cachep,
                                   struct page *page, int colour_off,
                                   gfp_t local_flags, int nodeid)
{
        void *freelist;
        void *addr = page_address(page);

        page->s_mem = addr + colour_off;
        page->active = 0;

        if (OBJFREELIST_SLAB(cachep))
                freelist = NULL;
        else if (OFF_SLAB(cachep)) {
                /* Slab management obj is off-slab. */
                freelist = kmem_cache_alloc_node(cachep->freelist_cache,
                                              local_flags, nodeid);
                if (!freelist)
                        return NULL;
        } else {
                /* We will use last bytes at the slab for freelist */
                freelist = addr + (PAGE_SIZE << cachep->gfporder) -
                                cachep->freelist_size;
        }

        return freelist;
}

static inline freelist_idx_t get_free_obj(struct page *page, unsigned int idx)
{
        return ((freelist_idx_t *)page->freelist)[idx];
}

static inline void set_free_obj(struct page *page,
                                        unsigned int idx, freelist_idx_t val)
{
        ((freelist_idx_t *)(page->freelist))[idx] = val;
}

static void cache_init_objs_debug(struct kmem_cache *cachep, struct page *page)
{
#if DEBUG
        int i;

        for (i = 0; i < cachep->num; i++) {
                void *objp = index_to_obj(cachep, page, i);

                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));

                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");
                }
                /* need to poison the objs? */
                if (cachep->flags & SLAB_POISON) {
                        poison_obj(cachep, objp, POISON_FREE);
                        slab_kernel_map(cachep, objp, 0, 0);
                }
        }
#endif
}

static void cache_init_objs(struct kmem_cache *cachep,
                            struct page *page)
{
        int i;

        cache_init_objs_debug(cachep, page);

        if (OBJFREELIST_SLAB(cachep)) {
                page->freelist = index_to_obj(cachep, page, cachep->num - 1) +
                                                obj_offset(cachep);
        }

        for (i = 0; i < cachep->num; i++) {
                /* constructor could break poison info */
                if (DEBUG == 0 && cachep->ctor)
                        cachep->ctor(index_to_obj(cachep, page, i));

                set_free_obj(page, i, i);
        }
}

static void kmem_flagcheck(struct kmem_cache *cachep, gfp_t flags)
{
        if (CONFIG_ZONE_DMA_FLAG) {
                if (flags & GFP_DMA)
                        BUG_ON(!(cachep->allocflags & GFP_DMA));
                else
                        BUG_ON(cachep->allocflags & GFP_DMA);
        }
}

static void *slab_get_obj(struct kmem_cache *cachep, struct page *page)
{
        void *objp;

        objp = index_to_obj(cachep, page, get_free_obj(page, page->active));
        page->active++;

#if DEBUG
        if (cachep->flags & SLAB_STORE_USER)
                set_store_user_dirty(cachep);
#endif

        return objp;
}

static void slab_put_obj(struct kmem_cache *cachep,
                        struct page *page, void *objp)
{
        unsigned int objnr = obj_to_index(cachep, page, objp);
#if DEBUG
        unsigned int i;

        /* Verify double free bug */
        for (i = page->active; i < cachep->num; i++) {
                if (get_free_obj(page, i) == objnr) {
                        printk(KERN_ERR "slab: double free detected in cache "
                                        "'%s', objp %p\n", cachep->name, objp);
                        BUG();
                }
        }
#endif
        page->active--;
        if (!page->freelist)
                page->freelist = objp + obj_offset(cachep);

        set_free_obj(page, page->active, objnr);
}

/*
 * Map pages beginning at addr to the given cache and slab. This is required
 * for the slab allocator to be able to lookup the cache and slab of a
 * virtual address for kfree, ksize, and slab debugging.
 */
static void slab_map_pages(struct kmem_cache *cache, struct page *page,
                           void *freelist)
{
        page->slab_cache = cache;
        page->freelist = freelist;
}

/*
 * 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 page *page)
{
        void *freelist;
        size_t offset;
        gfp_t local_flags;
        struct kmem_cache_node *n;

        /*
         * Be lazy and only check for valid flags here,  keeping it out of the
         * critical path in kmem_cache_alloc().
         */
        if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
                pr_emerg("gfp: %u\n", flags & GFP_SLAB_BUG_MASK);
                BUG();
        }
        local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);

        /* Take the node list lock to change the colour_next on this node */
        check_irq_off();
        n = get_node(cachep, nodeid);
        spin_lock(&n->list_lock);

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

        offset *= cachep->colour_off;

        if (gfpflags_allow_blocking(local_flags))
                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 (!page)
                page = kmem_getpages(cachep, local_flags, nodeid);
        if (!page)
                goto failed;

        /* Get slab management. */
        freelist = alloc_slabmgmt(cachep, page, offset,
                        local_flags & ~GFP_CONSTRAINT_MASK, nodeid);
        if (OFF_SLAB(cachep) && !freelist)
                goto opps1;

        slab_map_pages(cachep, page, freelist);

        cache_init_objs(cachep, page);

        if (gfpflags_allow_blocking(local_flags))
                local_irq_disable();
        check_irq_off();
        spin_lock(&n->list_lock);

        /* Make slab active. */
        list_add_tail(&page->lru, &(n->slabs_free));
        STATS_INC_GROWN(cachep);
        n->free_objects += cachep->num;
        spin_unlock(&n->list_lock);
        return 1;
opps1:
        kmem_freepages(cachep, page);
failed:
        if (gfpflags_allow_blocking(local_flags))
                local_irq_disable();
        return 0;
}

#if DEBUG

/*
 * Perform extra freeing checks:
 * - detect bad pointers.
 * - POISON/RED_ZONE checking
 */
static void kfree_debugcheck(const void *objp)
{
        if (!virt_addr_valid(objp)) {
                printk(KERN_ERR "kfree_debugcheck: out of range ptr %lxh.\n",
                       (unsigned long)objp);
                BUG();
        }
}

static inline void verify_redzone_free(struct kmem_cache *cache, void *obj)
{
        unsigned long long redzone1, redzone2;

        redzone1 = *dbg_redzone1(cache, obj);
        redzone2 = *dbg_redzone2(cache, obj);

        /*
         * Redzone is ok.
         */
        if (redzone1 == RED_ACTIVE && redzone2 == RED_ACTIVE)
                return;

        if (redzone1 == RED_INACTIVE && redzone2 == RED_INACTIVE)
                slab_error(cache, "double free detected");
        else
                slab_error(cache, "memory outside object was overwritten");

        printk(KERN_ERR "%p: redzone 1:0x%llx, redzone 2:0x%llx.\n",
                        obj, redzone1, redzone2);
}

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

        BUG_ON(virt_to_cache(objp) != cachep);

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

        if (cachep->flags & SLAB_RED_ZONE) {
                verify_redzone_free(cachep, objp);
                *dbg_redzone1(cachep, objp) = RED_INACTIVE;
                *dbg_redzone2(cachep, objp) = RED_INACTIVE;
        }
        if (cachep->flags & SLAB_STORE_USER) {
                set_store_user_dirty(cachep);
                *dbg_userword(cachep, objp) = (void *)caller;
        }

        objnr = obj_to_index(cachep, page, objp);

        BUG_ON(objnr >= cachep->num);
        BUG_ON(objp != index_to_obj(cachep, page, objnr));

        if (cachep->flags & SLAB_POISON) {
                poison_obj(cachep, objp, POISON_FREE);
                slab_kernel_map(cachep, objp, 0, caller);
        }
        return objp;
}

#else
#define kfree_debugcheck(x) do { } while(0)
#define cache_free_debugcheck(x,objp,z) (objp)
#endif

static inline void fixup_objfreelist_debug(struct kmem_cache *cachep,
                                                void **list)
{
#if DEBUG
        void *next = *list;
        void *objp;

        while (next) {
                objp = next - obj_offset(cachep);
                next = *(void **)next;
                poison_obj(cachep, objp, POISON_FREE);
        }
#endif
}

static inline void fixup_slab_list(struct kmem_cache *cachep,
                                struct kmem_cache_node *n, struct page *page,
                                void **list)
{
        /* move slabp to correct slabp list: */
        list_del(&page->lru);
        if (page->active == cachep->num) {
                list_add(&page->lru, &n->slabs_full);
                if (OBJFREELIST_SLAB(cachep)) {
#if DEBUG
                        /* Poisoning will be done without holding the lock */
                        if (cachep->flags & SLAB_POISON) {
                                void **objp = page->freelist;

                                *objp = *list;
                                *list = objp;
                        }
#endif
                        page->freelist = NULL;
                }
        } else
                list_add(&page->lru, &n->slabs_partial);
}

static struct page *get_first_slab(struct kmem_cache_node *n)
{
        struct page *page;

        page = list_first_entry_or_null(&n->slabs_partial,
                        struct page, lru);
        if (!page) {
                n->free_touched = 1;
                page = list_first_entry_or_null(&n->slabs_free,
                                struct page, lru);
        }

        return page;
}

static void *cache_alloc_refill(struct kmem_cache *cachep, gfp_t flags,
                                                        bool force_refill)
{
        int batchcount;
        struct kmem_cache_node *n;
        struct array_cache *ac;
        int node;
        void *list = NULL;

        check_irq_off();
        node = numa_mem_id();
        if (unlikely(force_refill))
                goto force_grow;
retry:
        ac = cpu_cache_get(cachep);
        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;
        }
        n = get_node(cachep, node);

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

        /* See if we can refill from the shared array */
        if (n->shared && transfer_objects(ac, n->shared, batchcount)) {
                n->shared->touched = 1;
                goto alloc_done;
        }

        while (batchcount > 0) {
                struct page *page;
                /* Get slab alloc is to come from. */
                page = get_first_slab(n);
                if (!page)
                        goto must_grow;

                check_spinlock_acquired(cachep);

                /*
                 * The slab was either on partial or free list so
                 * there must be at least one object available for
                 * allocation.
                 */
                BUG_ON(page->active >= cachep->num);

                while (page->active < cachep->num && batchcount--) {
                        STATS_INC_ALLOCED(cachep);
                        STATS_INC_ACTIVE(cachep);
                        STATS_SET_HIGH(cachep);

                        ac_put_obj(cachep, ac, slab_get_obj(cachep, page));
                }

                fixup_slab_list(cachep, n, page, &list);
        }

must_grow:
        n->free_objects -= ac->avail;
alloc_done:
        spin_unlock(&n->list_lock);
        fixup_objfreelist_debug(cachep, &list);

        if (unlikely(!ac->avail)) {
                int x;
force_grow:
                x = cache_grow(cachep, gfp_exact_node(flags), node, NULL);

                /* cache_grow can reenable interrupts, then ac could change. */
                ac = cpu_cache_get(cachep);
                node = numa_mem_id();

                /* no objects in sight? abort */
                if (!x && (ac->avail == 0 || force_refill))
                        return NULL;

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

        return ac_get_obj(cachep, ac, flags, force_refill);
}

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

#if DEBUG
static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep,
                                gfp_t flags, void *objp, unsigned long caller)
{
        if (!objp)
                return objp;
        if (cachep->flags & SLAB_POISON) {
                check_poison_obj(cachep, objp);
                slab_kernel_map(cachep, objp, 1, 0);
                poison_obj(cachep, objp, POISON_INUSE);
        }
        if (cachep->flags & SLAB_STORE_USER)
                *dbg_userword(cachep, objp) = (void *)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%llx, redzone 2:0x%llx\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)
                cachep->ctor(objp);
        if (ARCH_SLAB_MINALIGN &&
            ((unsigned long)objp & (ARCH_SLAB_MINALIGN-1))) {
                printk(KERN_ERR "0x%p: not aligned to ARCH_SLAB_MINALIGN=%d\n",
                       objp, (int)ARCH_SLAB_MINALIGN);
        }
        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;
        bool force_refill = false;

        check_irq_off();

        ac = cpu_cache_get(cachep);
        if (likely(ac->avail)) {
                ac->touched = 1;
                objp = ac_get_obj(cachep, ac, flags, false);

                /*
                 * Allow for the possibility all avail objects are not allowed
                 * by the current flags
                 */
                if (objp) {
                        STATS_INC_ALLOCHIT(cachep);
                        goto out;
                }
                force_refill = true;
        }

        STATS_INC_ALLOCMISS(cachep);
        objp = cache_alloc_refill(cachep, flags, force_refill);
        /*
         * the 'ac' may be updated by cache_alloc_refill(),
         * and kmemleak_erase() requires its correct value.
         */
        ac = cpu_cache_get(cachep);

out:
        /*
         * To avoid a false negative, if an object that is in one of the
         * per-CPU caches is leaked, we need to make sure kmemleak doesn't
         * treat the array pointers as a reference to the object.
         */
        if (objp)
                kmemleak_erase(&ac->entry[ac->avail]);
        return objp;
}

#ifdef CONFIG_NUMA
/*
 * Try allocating on another node if PFA_SPREAD_SLAB is a mempolicy is set.
 *
 * If we are in_interrupt, then process context, including cpusets and
 * mempolicy, may not apply and should not be used for allocation policy.
 */
static void *alternate_node_alloc(struct kmem_cache *cachep, gfp_t flags)
{
        int nid_alloc, nid_here;

        if (in_interrupt() || (flags & __GFP_THISNODE))
                return NULL;
        nid_alloc = nid_here = numa_mem_id();
        if (cpuset_do_slab_mem_spread() && (cachep->flags & SLAB_MEM_SPREAD))
                nid_alloc = cpuset_slab_spread_node();
        else if (current->mempolicy)
                nid_alloc = mempolicy_slab_node();
        if (nid_alloc != nid_here)
                return ____cache_alloc_node(cachep, flags, nid_alloc);
        return NULL;
}

/*
 * Fallback function if there was no memory available and no objects on a
 * certain node and fall back is permitted. First we scan all the
 * available node for available objects. If that fails then we
 * perform an allocation without specifying a node. This allows the page
 * allocator to do its reclaim / fallback magic. We then insert the
 * slab into the proper nodelist and then allocate from it.
 */
static void *fallback_alloc(struct kmem_cache *cache, gfp_t flags)
{
        struct zonelist *zonelist;
        gfp_t local_flags;
        struct zoneref *z;
        struct zone *zone;
        enum zone_type high_zoneidx = gfp_zone(flags);
        void *obj = NULL;
        int nid;
        unsigned int cpuset_mems_cookie;

        if (flags & __GFP_THISNODE)
                return NULL;

        local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);

retry_cpuset:
        cpuset_mems_cookie = read_mems_allowed_begin();
        zonelist = node_zonelist(mempolicy_slab_node(), flags);

retry:
        /*
         * Look through allowed nodes for objects available
         * from existing per node queues.
         */
        for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
                nid = zone_to_nid(zone);

                if (cpuset_zone_allowed(zone, flags) &&
                        get_node(cache, nid) &&
                        get_node(cache, nid)->free_objects) {
                                obj = ____cache_alloc_node(cache,
                                        gfp_exact_node(flags), nid);
                                if (obj)
                                        break;
                }
        }

        if (!obj) {
                /*
                 * This allocation will be performed within the constraints
                 * of the current cpuset / memory policy requirements.
                 * We may trigger various forms of reclaim on the allowed
                 * set and go into memory reserves if necessary.
                 */
                struct page *page;

                if (gfpflags_allow_blocking(local_flags))
                        local_irq_enable();
                kmem_flagcheck(cache, flags);
                page = kmem_getpages(cache, local_flags, numa_mem_id());
                if (gfpflags_allow_blocking(local_flags))
                        local_irq_disable();
                if (page) {
                        /*
                         * Insert into the appropriate per node queues
                         */
                        nid = page_to_nid(page);
                        if (cache_grow(cache, flags, nid, page)) {
                                obj = ____cache_alloc_node(cache,
                                        gfp_exact_node(flags), nid);
                                if (!obj)
                                        /*
                                         * Another processor may allocate the
                                         * objects in the slab since we are
                                         * not holding any locks.
                                         */
                                        goto retry;
                        } else {
                                /* cache_grow already freed obj */
                                obj = NULL;
                        }
                }
        }

        if (unlikely(!obj && read_mems_allowed_retry(cpuset_mems_cookie)))
                goto retry_cpuset;
        return obj;
}

/*
 * A interface to enable slab creation on nodeid
 */
static void *____cache_alloc_node(struct kmem_cache *cachep, gfp_t flags,
                                int nodeid)
{
        struct page *page;
        struct kmem_cache_node *n;
        void *obj;
        void *list = NULL;
        int x;

        VM_BUG_ON(nodeid < 0 || nodeid >= MAX_NUMNODES);
        n = get_node(cachep, nodeid);
        BUG_ON(!n);

retry:
        check_irq_off();
        spin_lock(&n->list_lock);
        page = get_first_slab(n);
        if (!page)
                goto must_grow;

        check_spinlock_acquired_node(cachep, nodeid);

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

        BUG_ON(page->active == cachep->num);

        obj = slab_get_obj(cachep, page);
        n->free_objects--;

        fixup_slab_list(cachep, n, page, &list);

        spin_unlock(&n->list_lock);
        fixup_objfreelist_debug(cachep, &list);
        goto done;

must_grow:
        spin_unlock(&n->list_lock);
        x = cache_grow(cachep, gfp_exact_node(flags), nodeid, NULL);
        if (x)
                goto retry;

        return fallback_alloc(cachep, flags);

done:
        return obj;
}

static __always_inline void *
slab_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid,
                   unsigned long caller)
{
        unsigned long save_flags;
        void *ptr;
        int slab_node = numa_mem_id();

        flags &= gfp_allowed_mask;
        cachep = slab_pre_alloc_hook(cachep, flags);
        if (unlikely(!cachep))
                return NULL;

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

        if (nodeid == NUMA_NO_NODE)
                nodeid = slab_node;

        if (unlikely(!get_node(cachep, nodeid))) {
                /* Node not bootstrapped yet */
                ptr = fallback_alloc(cachep, flags);
                goto out;
        }

        if (nodeid == slab_node) {
                /*
                 * Use the locally cached objects if possible.
                 * However ____cache_alloc does not allow fallback
                 * to other nodes. It may fail while we still have
                 * objects on other nodes available.
                 */
                ptr = ____cache_alloc(cachep, flags);
                if (ptr)
                        goto out;
        }
        /* ___cache_alloc_node can fall back to other nodes */
        ptr = ____cache_alloc_node(cachep, flags, nodeid);
  out:
        local_irq_restore(save_flags);
        ptr = cache_alloc_debugcheck_after(cachep, flags, ptr, caller);

        if (unlikely(flags & __GFP_ZERO) && ptr)
                memset(ptr, 0, cachep->object_size);

        slab_post_alloc_hook(cachep, flags, 1, &ptr);
        return ptr;
}

static __always_inline void *
__do_cache_alloc(struct kmem_cache *cache, gfp_t flags)
{
        void *objp;

        if (current->mempolicy || cpuset_do_slab_mem_spread()) {
                objp = alternate_node_alloc(cache, flags);
                if (objp)
                        goto out;
        }
        objp = ____cache_alloc(cache, flags);

        /*
         * We may just have run out of memory on the local node.
         * ____cache_alloc_node() knows how to locate memory on other nodes
         */
        if (!objp)
                objp = ____cache_alloc_node(cache, flags, numa_mem_id());

  out:
        return objp;
}
#else

static __always_inline void *
__do_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
{
        return ____cache_alloc(cachep, flags);
}

#endif /* CONFIG_NUMA */

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

        flags &= gfp_allowed_mask;
        cachep = slab_pre_alloc_hook(cachep, flags);
        if (unlikely(!cachep))
                return NULL;

        cache_alloc_debugcheck_before(cachep, flags);
        local_irq_save(save_flags);
        objp = __do_cache_alloc(cachep, flags);
        local_irq_restore(save_flags);
        objp = cache_alloc_debugcheck_after(cachep, flags, objp, caller);
        prefetchw(objp);

        if (unlikely(flags & __GFP_ZERO) && objp)
                memset(objp, 0, cachep->object_size);

        slab_post_alloc_hook(cachep, flags, 1, &objp);
        return objp;
}

/*
 * Caller needs to acquire correct kmem_cache_node's list_lock
 * @list: List of detached free slabs should be freed by caller
 */
static void free_block(struct kmem_cache *cachep, void **objpp,
                        int nr_objects, int node, struct list_head *list)
{
        int i;
        struct kmem_cache_node *n = get_node(cachep, node);

        for (i = 0; i < nr_objects; i++) {
                void *objp;
                struct page *page;

                clear_obj_pfmemalloc(&objpp[i]);
                objp = objpp[i];

                page = virt_to_head_page(objp);
                list_del(&page->lru);
                check_spinlock_acquired_node(cachep, node);
                slab_put_obj(cachep, page, objp);
                STATS_DEC_ACTIVE(cachep);
                n->free_objects++;

                /* fixup slab chains */
                if (page->active == 0) {
                        if (n->free_objects > n->free_limit) {
                                n->free_objects -= cachep->num;
                                list_add_tail(&page->lru, list);
                        } else {
                                list_add(&page->lru, &n->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(&page->lru, &n->slabs_partial);
                }
        }
}

static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac)
{
        int batchcount;
        struct kmem_cache_node *n;
        int node = numa_mem_id();
        LIST_HEAD(list);

        batchcount = ac->batchcount;

        check_irq_off();
        n = get_node(cachep, node);
        spin_lock(&n->list_lock);
        if (n->shared) {
                struct array_cache *shared_array = n->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, &list);
free_done:
#if STATS
        {
                int i = 0;
                struct page *page;

                list_for_each_entry(page, &n->slabs_free, lru) {
                        BUG_ON(page->active);

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

/*
 * 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,
                                unsigned long caller)
{
        struct array_cache *ac = cpu_cache_get(cachep);

        check_irq_off();
        kmemleak_free_recursive(objp, cachep->flags);
        objp = cache_free_debugcheck(cachep, objp, caller);

        kmemcheck_slab_free(cachep, objp, cachep->object_size);

        /*
         * Skip calling cache_free_alien() when the platform is not numa.
         * This will avoid cache misses that happen while accessing slabp (which
         * is per page memory  reference) to get nodeid. Instead use a global
         * variable to skip the call, which is mostly likely to be present in
         * the cache.
         */
        if (nr_online_nodes > 1 && cache_free_alien(cachep, objp))
                return;

        if (ac->avail < ac->limit) {
                STATS_INC_FREEHIT(cachep);
        } else {
                STATS_INC_FREEMISS(cachep);
                cache_flusharray(cachep, ac);
        }

        ac_put_obj(cachep, ac, 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)
{
        void *ret = slab_alloc(cachep, flags, _RET_IP_);

        trace_kmem_cache_alloc(_RET_IP_, ret,
                               cachep->object_size, cachep->size, flags);

        return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc);

static __always_inline void
cache_alloc_debugcheck_after_bulk(struct kmem_cache *s, gfp_t flags,
                                  size_t size, void **p, unsigned long caller)
{
        size_t i;

        for (i = 0; i < size; i++)
                p[i] = cache_alloc_debugcheck_after(s, flags, p[i], caller);
}

int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
                          void **p)
{
        size_t i;

        s = slab_pre_alloc_hook(s, flags);
        if (!s)
                return 0;

        cache_alloc_debugcheck_before(s, flags);

        local_irq_disable();
        for (i = 0; i < size; i++) {
                void *objp = __do_cache_alloc(s, flags);

                if (unlikely(!objp))
                        goto error;
                p[i] = objp;
        }
        local_irq_enable();

        cache_alloc_debugcheck_after_bulk(s, flags, size, p, _RET_IP_);

        /* Clear memory outside IRQ disabled section */
        if (unlikely(flags & __GFP_ZERO))
                for (i = 0; i < size; i++)
                        memset(p[i], 0, s->object_size);

        slab_post_alloc_hook(s, flags, size, p);
        /* FIXME: Trace call missing. Christoph would like a bulk variant */
        return size;
error:
        local_irq_enable();
        cache_alloc_debugcheck_after_bulk(s, flags, i, p, _RET_IP_);
        slab_post_alloc_hook(s, flags, i, p);
        __kmem_cache_free_bulk(s, i, p);
        return 0;
}
EXPORT_SYMBOL(kmem_cache_alloc_bulk);

#ifdef CONFIG_TRACING
void *
kmem_cache_alloc_trace(struct kmem_cache *cachep, gfp_t flags, size_t size)
{
        void *ret;

        ret = slab_alloc(cachep, flags, _RET_IP_);

        trace_kmalloc(_RET_IP_, ret,
                      size, cachep->size, flags);
        return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_trace);
#endif

#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 but it will allocate memory on the given
 * node, which can improve the performance for cpu bound structures.
 *
 * Fallback to other node is possible if __GFP_THISNODE is not set.
 */
void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t flags, int nodeid)
{
        void *ret = slab_alloc_node(cachep, flags, nodeid, _RET_IP_);

        trace_kmem_cache_alloc_node(_RET_IP_, ret,
                                    cachep->object_size, cachep->size,
                                    flags, nodeid);

        return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_node);

#ifdef CONFIG_TRACING
void *kmem_cache_alloc_node_trace(struct kmem_cache *cachep,
                                  gfp_t flags,
                                  int nodeid,
                                  size_t size)
{
        void *ret;

        ret = slab_alloc_node(cachep, flags, nodeid, _RET_IP_);

        trace_kmalloc_node(_RET_IP_, ret,
                           size, cachep->size,
                           flags, nodeid);
        return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_node_trace);
#endif

static __always_inline void *
__do_kmalloc_node(size_t size, gfp_t flags, int node, unsigned long caller)
{
        struct kmem_cache *cachep;

        cachep = kmalloc_slab(size, flags);
        if (unlikely(ZERO_OR_NULL_PTR(cachep)))
                return cachep;
        return kmem_cache_alloc_node_trace(cachep, flags, node, size);
}

void *__kmalloc_node(size_t size, gfp_t flags, int node)
{
        return __do_kmalloc_node(size, flags, node, _RET_IP_);
}
EXPORT_SYMBOL(__kmalloc_node);

void *__kmalloc_node_track_caller(size_t size, gfp_t flags,
                int node, unsigned long caller)
{
        return __do_kmalloc_node(size, flags, node, caller);
}
EXPORT_SYMBOL(__kmalloc_node_track_caller);
#endif /* CONFIG_NUMA */

/**
 * __do_kmalloc - allocate memory
 * @size: how many bytes of memory are required.
 * @flags: the type of memory to allocate (see kmalloc).
 * @caller: function caller for debug tracking of the caller
 */
static __always_inline void *__do_kmalloc(size_t size, gfp_t flags,
                                          unsigned long caller)
{
        struct kmem_cache *cachep;
        void *ret;

        cachep = kmalloc_slab(size, flags);
        if (unlikely(ZERO_OR_NULL_PTR(cachep)))
                return cachep;
        ret = slab_alloc(cachep, flags, caller);

        trace_kmalloc(caller, ret,
                      size, cachep->size, flags);

        return ret;
}

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

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

/**
 * 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;
        cachep = cache_from_obj(cachep, objp);
        if (!cachep)
                return;

        local_irq_save(flags);
        debug_check_no_locks_freed(objp, cachep->object_size);
        if (!(cachep->flags & SLAB_DEBUG_OBJECTS))
                debug_check_no_obj_freed(objp, cachep->object_size);
        __cache_free(cachep, objp, _RET_IP_);
        local_irq_restore(flags);

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

void kmem_cache_free_bulk(struct kmem_cache *orig_s, size_t size, void **p)
{
        struct kmem_cache *s;
        size_t i;

        local_irq_disable();
        for (i = 0; i < size; i++) {
                void *objp = p[i];

                if (!orig_s) /* called via kfree_bulk */
                        s = virt_to_cache(objp);
                else
                        s = cache_from_obj(orig_s, objp);

                debug_check_no_locks_freed(objp, s->object_size);
                if (!(s->flags & SLAB_DEBUG_OBJECTS))
                        debug_check_no_obj_freed(objp, s->object_size);

                __cache_free(s, objp, _RET_IP_);
        }
        local_irq_enable();

        /* FIXME: add tracing */
}
EXPORT_SYMBOL(kmem_cache_free_bulk);

/**
 * 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;

        trace_kfree(_RET_IP_, objp);

        if (unlikely(ZERO_OR_NULL_PTR(objp)))
                return;
        local_irq_save(flags);
        kfree_debugcheck(objp);
        c = virt_to_cache(objp);
        debug_check_no_locks_freed(objp, c->object_size);

        debug_check_no_obj_freed(objp, c->object_size);
        __cache_free(c, (void *)objp, _RET_IP_);
        local_irq_restore(flags);
}
EXPORT_SYMBOL(kfree);

/*
 * This initializes kmem_cache_node or resizes various caches for all nodes.
 */
static int alloc_kmem_cache_node(struct kmem_cache *cachep, gfp_t gfp)
{
        int node;
        struct kmem_cache_node *n;
        struct array_cache *new_shared;
        struct alien_cache **new_alien = NULL;

        for_each_online_node(node) {

                if (use_alien_caches) {
                        new_alien = alloc_alien_cache(node, cachep->limit, gfp);
                        if (!new_alien)
                                goto fail;
                }

                new_shared = NULL;
                if (cachep->shared) {
                        new_shared = alloc_arraycache(node,
                                cachep->shared*cachep->batchcount,
                                        0xbaadf00d, gfp);
                        if (!new_shared) {
                                free_alien_cache(new_alien);
                                goto fail;
                        }
                }

                n = get_node(cachep, node);
                if (n) {
                        struct array_cache *shared = n->shared;
                        LIST_HEAD(list);

                        spin_lock_irq(&n->list_lock);

                        if (shared)
                                free_block(cachep, shared->entry,
                                                shared->avail, node, &list);

                        n->shared = new_shared;
                        if (!n->alien) {
                                n->alien = new_alien;
                                new_alien = NULL;
                        }
                        n->free_limit = (1 + nr_cpus_node(node)) *
                                        cachep->batchcount + cachep->num;
                        spin_unlock_irq(&n->list_lock);
                        slabs_destroy(cachep, &list);
                        kfree(shared);
                        free_alien_cache(new_alien);
                        continue;
                }
                n = kmalloc_node(sizeof(struct kmem_cache_node), gfp, node);
                if (!n) {
                        free_alien_cache(new_alien);
                        kfree(new_shared);
                        goto fail;
                }

                kmem_cache_node_init(n);
                n->next_reap = jiffies + REAPTIMEOUT_NODE +
                                ((unsigned long)cachep) % REAPTIMEOUT_NODE;
                n->shared = new_shared;
                n->alien = new_alien;
                n->free_limit = (1 + nr_cpus_node(node)) *
                                        cachep->batchcount + cachep->num;
                cachep->node[node] = n;
        }
        return 0;

fail:
        if (!cachep->list.next) {
                /* Cache is not active yet. Roll back what we did */
                node--;
                while (node >= 0) {
                        n = get_node(cachep, node);
                        if (n) {
                                kfree(n->shared);
                                free_alien_cache(n->alien);
                                kfree(n);
                                cachep->node[node] = NULL;
                        }
                        node--;
                }
        }
        return -ENOMEM;
}

/* Always called with the slab_mutex held */
static int __do_tune_cpucache(struct kmem_cache *cachep, int limit,
                                int batchcount, int shared, gfp_t gfp)
{
        struct array_cache __percpu *cpu_cache, *prev;
        int cpu;

        cpu_cache = alloc_kmem_cache_cpus(cachep, limit, batchcount);
        if (!cpu_cache)
                return -ENOMEM;

        prev = cachep->cpu_cache;
        cachep->cpu_cache = cpu_cache;
        kick_all_cpus_sync();

        check_irq_on();
        cachep->batchcount = batchcount;
        cachep->limit = limit;
        cachep->shared = shared;

        if (!prev)
                goto alloc_node;

        for_each_online_cpu(cpu) {
                LIST_HEAD(list);
                int node;
                struct kmem_cache_node *n;
                struct array_cache *ac = per_cpu_ptr(prev, cpu);

                node = cpu_to_mem(cpu);
                n = get_node(cachep, node);
                spin_lock_irq(&n->list_lock);
                free_block(cachep, ac->entry, ac->avail, node, &list);
                spin_unlock_irq(&n->list_lock);
                slabs_destroy(cachep, &list);
        }
        free_percpu(prev);

alloc_node:
        return alloc_kmem_cache_node(cachep, gfp);
}

static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
                                int batchcount, int shared, gfp_t gfp)
{
        int ret;
        struct kmem_cache *c;

        ret = __do_tune_cpucache(cachep, limit, batchcount, shared, gfp);

        if (slab_state < FULL)
                return ret;

        if ((ret < 0) || !is_root_cache(cachep))
                return ret;

        lockdep_assert_held(&slab_mutex);
        for_each_memcg_cache(c, cachep) {
                /* return value determined by the root cache only */
                __do_tune_cpucache(c, limit, batchcount, shared, gfp);
        }

        return ret;
}

/* Called with slab_mutex held always */
static int enable_cpucache(struct kmem_cache *cachep, gfp_t gfp)
{
        int err;
        int limit = 0;
        int shared = 0;
        int batchcount = 0;

        if (!is_root_cache(cachep)) {
                struct kmem_cache *root = memcg_root_cache(cachep);
                limit = root->limit;
                shared = root->shared;
                batchcount = root->batchcount;
        }

        if (limit && shared && batchcount)
                goto skip_setup;
        /*
         * 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->size > 131072)
                limit = 1;
        else if (cachep->size > PAGE_SIZE)
                limit = 8;
        else if (cachep->size > 1024)
                limit = 24;
        else if (cachep->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;
        if (cachep->size <= PAGE_SIZE && num_possible_cpus() > 1)
                shared = 8;

#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
        batchcount = (limit + 1) / 2;
skip_setup:
        err = do_tune_cpucache(cachep, limit, batchcount, shared, gfp);
        if (err)
                printk(KERN_ERR "enable_cpucache failed for %s, error %d.\n",
                       cachep->name, -err);
        return err;
}

/*
 * Drain an array if it contains any elements taking the node lock only if
 * necessary. Note that the node listlock also protects the array_cache
 * if drain_array() is used on the shared array.
 */
static void drain_array(struct kmem_cache *cachep, struct kmem_cache_node *n,
                         struct array_cache *ac, int force, int node)
{
        LIST_HEAD(list);
        int tofree;

        if (!ac || !ac->avail)
                return;
        if (ac->touched && !force) {
                ac->touched = 0;
        } else {
                spin_lock_irq(&n->list_lock);
                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, &list);
                        ac->avail -= tofree;
                        memmove(ac->entry, &(ac->entry[tofree]),
                                sizeof(void *) * ac->avail);
                }
                spin_unlock_irq(&n->list_lock);
                slabs_destroy(cachep, &list);
        }
}

/**
 * cache_reap - Reclaim memory from caches.
 * @w: work descriptor
 *
 * 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(struct work_struct *w)
{
        struct kmem_cache *searchp;
        struct kmem_cache_node *n;
        int node = numa_mem_id();
        struct delayed_work *work = to_delayed_work(w);

        if (!mutex_trylock(&slab_mutex))
                /* Give up. Setup the next iteration. */
                goto out;

        list_for_each_entry(searchp, &slab_caches, list) {
                check_irq_on();

                /*
                 * We only take the node lock if absolutely necessary and we
                 * have established with reasonable certainty that
                 * we can do some work if the lock was obtained.
                 */
                n = get_node(searchp, node);

                reap_alien(searchp, n);

                drain_array(searchp, n, cpu_cache_get(searchp), 0, node);

                /*
                 * These are racy checks but it does not matter
                 * if we skip one check or scan twice.
                 */
                if (time_after(n->next_reap, jiffies))
                        goto next;

                n->next_reap = jiffies + REAPTIMEOUT_NODE;

                drain_array(searchp, n, n->shared, 0, node);

                if (n->free_touched)
                        n->free_touched = 0;
                else {
                        int freed;

                        freed = drain_freelist(searchp, n, (n->free_limit +
                                5 * searchp->num - 1) / (5 * searchp->num));
                        STATS_ADD_REAPED(searchp, freed);
                }
next:
                cond_resched();
        }
        check_irq_on();
        mutex_unlock(&slab_mutex);
        next_reap_node();
out:
        /* Set up the next iteration */
        schedule_delayed_work(work, round_jiffies_relative(REAPTIMEOUT_AC));
}

#ifdef CONFIG_SLABINFO
void get_slabinfo(struct kmem_cache *cachep, struct slabinfo *sinfo)
{
        struct page *page;
        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_cache_node *n;

        active_objs = 0;
        num_slabs = 0;
        for_each_kmem_cache_node(cachep, node, n) {

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

                list_for_each_entry(page, &n->slabs_full, lru) {
                        if (page->active != cachep->num && !error)
                                error = "slabs_full accounting error";
                        active_objs += cachep->num;
                        active_slabs++;
                }
                list_for_each_entry(page, &n->slabs_partial, lru) {
                        if (page->active == cachep->num && !error)
                                error = "slabs_partial accounting error";
                        if (!page->active && !error)
                                error = "slabs_partial accounting error";
                        active_objs += page->active;
                        active_slabs++;
                }
                list_for_each_entry(page, &n->slabs_free, lru) {
                        if (page->active && !error)
                                error = "slabs_free accounting error";
                        num_slabs++;
                }
                free_objects += n->free_objects;
                if (n->shared)
                        shared_avail += n->shared->avail;

                spin_unlock_irq(&n->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);

        sinfo->active_objs = active_objs;
        sinfo->num_objs = num_objs;
        sinfo->active_slabs = active_slabs;
        sinfo->num_slabs = num_slabs;
        sinfo->shared_avail = shared_avail;
        sinfo->limit = cachep->limit;
        sinfo->batchcount = cachep->batchcount;
        sinfo->shared = cachep->shared;
        sinfo->objects_per_slab = cachep->num;
        sinfo->cache_order = cachep->gfporder;
}

void slabinfo_show_stats(struct seq_file *m, struct kmem_cache *cachep)
{
#if STATS
        {                       /* node 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;
                unsigned long overflows = cachep->node_overflow;

                seq_printf(m, " : globalstat %7lu %6lu %5lu %4lu "
                           "%4lu %4lu %4lu %4lu %4lu",
                           allocs, high, grown,
                           reaped, errors, max_freeable, node_allocs,
                           node_frees, overflows);
        }
        /* 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
}

#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 kmem_cache *cachep;

        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(&slab_mutex);
        res = -EINVAL;
        list_for_each_entry(cachep, &slab_caches, list) {
                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,
                                                       GFP_KERNEL);
                        }
                        break;
                }
        }
        mutex_unlock(&slab_mutex);
        if (res >= 0)
                res = count;
        return res;
}

#ifdef CONFIG_DEBUG_SLAB_LEAK

static inline int add_caller(unsigned long *n, unsigned long v)
{
        unsigned long *p;
        int l;
        if (!v)
                return 1;
        l = n[1];
        p = n + 2;
        while (l) {
                int i = l/2;
                unsigned long *q = p + 2 * i;
                if (*q == v) {
                        q[1]++;
                        return 1;
                }
                if (*q > v) {
                        l = i;
                } else {
                        p = q + 2;
                        l -= i + 1;
                }
        }
        if (++n[1] == n[0])
                return 0;
        memmove(p + 2, p, n[1] * 2 * sizeof(unsigned long) - ((void *)p - (void *)n));
        p[0] = v;
        p[1] = 1;
        return 1;
}

static void handle_slab(unsigned long *n, struct kmem_cache *c,
                                                struct page *page)
{
        void *p;
        int i, j;
        unsigned long v;

        if (n[0] == n[1])
                return;
        for (i = 0, p = page->s_mem; i < c->num; i++, p += c->size) {
                bool active = true;

                for (j = page->active; j < c->num; j++) {
                        if (get_free_obj(page, j) == i) {
                                active = false;
                                break;
                        }
                }

                if (!active)
                        continue;

                /*
                 * probe_kernel_read() is used for DEBUG_PAGEALLOC. page table
                 * mapping is established when actual object allocation and
                 * we could mistakenly access the unmapped object in the cpu
                 * cache.
                 */
                if (probe_kernel_read(&v, dbg_userword(c, p), sizeof(v)))
                        continue;

                if (!add_caller(n, v))
                        return;
        }
}

static void show_symbol(struct seq_file *m, unsigned long address)
{
#ifdef CONFIG_KALLSYMS
        unsigned long offset, size;
        char modname[MODULE_NAME_LEN], name[KSYM_NAME_LEN];

        if (lookup_symbol_attrs(address, &size, &offset, modname, name) == 0) {
                seq_printf(m, "%s+%#lx/%#lx", name, offset, size);
                if (modname[0])
                        seq_printf(m, " [%s]", modname);
                return;
        }
#endif
        seq_printf(m, "%p", (void *)address);
}

static int leaks_show(struct seq_file *m, void *p)
{
        struct kmem_cache *cachep = list_entry(p, struct kmem_cache, list);
        struct page *page;
        struct kmem_cache_node *n;
        const char *name;
        unsigned long *x = m->private;
        int node;
        int i;

        if (!(cachep->flags & SLAB_STORE_USER))
                return 0;
        if (!(cachep->flags & SLAB_RED_ZONE))
                return 0;

        /*
         * Set store_user_clean and start to grab stored user information
         * for all objects on this cache. If some alloc/free requests comes
         * during the processing, information would be wrong so restart
         * whole processing.
         */
        do {
                set_store_user_clean(cachep);
                drain_cpu_caches(cachep);

                x[1] = 0;

                for_each_kmem_cache_node(cachep, node, n) {

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

                        list_for_each_entry(page, &n->slabs_full, lru)
                                handle_slab(x, cachep, page);
                        list_for_each_entry(page, &n->slabs_partial, lru)
                                handle_slab(x, cachep, page);
                        spin_unlock_irq(&n->list_lock);
                }
        } while (!is_store_user_clean(cachep));

        name = cachep->name;
        if (x[0] == x[1]) {
                /* Increase the buffer size */
                mutex_unlock(&slab_mutex);
                m->private = kzalloc(x[0] * 4 * sizeof(unsigned long), GFP_KERNEL);
                if (!m->private) {
                        /* Too bad, we are really out */
                        m->private = x;
                        mutex_lock(&slab_mutex);
                        return -ENOMEM;
                }
                *(unsigned long *)m->private = x[0] * 2;
                kfree(x);
                mutex_lock(&slab_mutex);
                /* Now make sure this entry will be retried */
                m->count = m->size;
                return 0;
        }
        for (i = 0; i < x[1]; i++) {
                seq_printf(m, "%s: %lu ", name, x[2*i+3]);
                show_symbol(m, x[2*i+2]);
                seq_putc(m, '\n');
        }

        return 0;
}

static const struct seq_operations slabstats_op = {
        .start = slab_start,
        .next = slab_next,
        .stop = slab_stop,
        .show = leaks_show,
};

static int slabstats_open(struct inode *inode, struct file *file)
{
        unsigned long *n;

        n = __seq_open_private(file, &slabstats_op, PAGE_SIZE);
        if (!n)
                return -ENOMEM;

        *n = PAGE_SIZE / (2 * sizeof(unsigned long));

        return 0;
}

static const struct file_operations proc_slabstats_operations = {
        .open           = slabstats_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = seq_release_private,
};
#endif

static int __init slab_proc_init(void)
{
#ifdef CONFIG_DEBUG_SLAB_LEAK
        proc_create("slab_allocators", 0, NULL, &proc_slabstats_operations);
#endif
        return 0;
}
module_init(slab_proc_init);
#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.
 */
size_t ksize(const void *objp)
{
        BUG_ON(!objp);
        if (unlikely(objp == ZERO_SIZE_PTR))
                return 0;

        return virt_to_cache(objp)->object_size;
}
EXPORT_SYMBOL(ksize);