slub.c

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

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

#include <trace/events/kmem.h>

#include "internal.h"

/*
 * Lock order:
 *   1. slab_mutex (Global Mutex)
 *   2. node->list_lock
 *   3. slab_lock(page) (Only on some arches and for debugging)
 *
 *   slab_mutex
 *
 *   The role of the slab_mutex is to protect the list of all the slabs
 *   and to synchronize major metadata changes to slab cache structures.
 *
 *   The slab_lock is only used for debugging and on arches that do not
 *   have the ability to do a cmpxchg_double. It only protects the second
 *   double word in the page struct. Meaning
 *  A. page->freelist   -> List of object free in a page
 *  B. page->counters   -> Counters of objects
 *  C. page->frozen     -> frozen state
 *
 *   If a slab is frozen then it is exempt from list management. It is not
 *   on any list. The processor that froze the slab is the one who can
 *   perform list operations on the page. Other processors may put objects
 *   onto the freelist but the processor that froze the slab is the only
 *   one that can retrieve the objects from the page's freelist.
 *
 *   The list_lock protects the partial and full list on each node and
 *   the partial slab counter. If taken then no new slabs may be added or
 *   removed from the lists nor make the number of partial slabs be modified.
 *   (Note that the total number of slabs is an atomic value that may be
 *   modified without taking the list lock).
 *
 *   The list_lock is a centralized lock and thus we avoid taking it as
 *   much as possible. As long as SLUB does not have to handle partial
 *   slabs, operations can continue without any centralized lock. F.e.
 *   allocating a long series of objects that fill up slabs does not require
 *   the list lock.
 *   Interrupts are disabled during allocation and deallocation in order to
 *   make the slab allocator safe to use in the context of an irq. In addition
 *   interrupts are disabled to ensure that the processor does not change
 *   while handling per_cpu slabs, due to kernel preemption.
 *
 * SLUB assigns one slab for allocation to each processor.
 * Allocations only occur from these slabs called cpu slabs.
 *
 * Slabs with free elements are kept on a partial list and during regular
 * operations no list for full slabs is used. If an object in a full slab is
 * freed then the slab will show up again on the partial lists.
 * We track full slabs for debugging purposes though because otherwise we
 * cannot scan all objects.
 *
 * Slabs are freed when they become empty. Teardown and setup is
 * minimal so we rely on the page allocators per cpu caches for
 * fast frees and allocs.
 *
 * Overloading of page flags that are otherwise used for LRU management.
 *
 * PageActive       The slab is frozen and exempt from list processing.
 *          This means that the slab is dedicated to a purpose
 *          such as satisfying allocations for a specific
 *          processor. Objects may be freed in the slab while
 *          it is frozen but slab_free will then skip the usual
 *          list operations. It is up to the processor holding
 *          the slab to integrate the slab into the slab lists
 *          when the slab is no longer needed.
 *
 *          One use of this flag is to mark slabs that are
 *          used for allocations. Then such a slab becomes a cpu
 *          slab. The cpu slab may be equipped with an additional
 *          freelist that allows lockless access to
 *          free objects in addition to the regular freelist
 *          that requires the slab lock.
 *
 * PageError        Slab requires special handling due to debug
 *          options set. This moves slab handling out of
 *          the fast path and disables lockless freelists.
 */

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

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

/*
 * Issues still to be resolved:
 *
 * - Support PAGE_ALLOC_DEBUG. Should be easy to do.
 *
 * - Variable sizing of the per node arrays
 */

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

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

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

/*
 * Maximum number of desirable partial slabs.
 * The existence of more partial slabs makes kmem_cache_shrink
 * sort the partial list by the number of objects in the.
 */
#define MAX_PARTIAL 10

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

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

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

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

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

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

static int kmem_size = sizeof(struct kmem_cache);

#ifdef CONFIG_SMP
static struct notifier_block slab_notifier;
#endif

/*
 * Tracking user of a slab.
 */
#define TRACK_ADDRS_COUNT 16
struct track {
    unsigned long addr; /* Called from address */
#ifdef CONFIG_STACKTRACE
    unsigned long addrs[TRACK_ADDRS_COUNT]; /* Called from address */
#endif
    int cpu;        /* Was running on cpu */
    int pid;        /* Pid context */
    unsigned long when; /* When did the operation occur */
};

enum track_item { TRACK_ALLOC, TRACK_FREE };

#ifdef CONFIG_SYSFS
static int sysfs_slab_add(struct kmem_cache *);
static int sysfs_slab_alias(struct kmem_cache *, const char *);
static void sysfs_slab_remove(struct kmem_cache *);

#else
static inline int sysfs_slab_add(struct kmem_cache *s) { return 0; }
static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
                            { return 0; }
static inline void sysfs_slab_remove(struct kmem_cache *s) { }

#endif

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

/********************************************************************
 *          Core slab cache functions
 *******************************************************************/

static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
{
    return s->node[node];
}

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

    if (!object)
        return 1;

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

    return 1;
}

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

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

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

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

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

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

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

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

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

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

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

    return x;
}

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

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

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

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

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

    cpu_relax();
    stat(s, CMPXCHG_DOUBLE_FAIL);

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

    return 0;
}

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

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

    cpu_relax();
    stat(s, CMPXCHG_DOUBLE_FAIL);

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

    return 0;
}

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

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

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

static char *slub_debug_slabs;
static int disable_higher_order_debug;

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

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

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

    return p + alloc;
}

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

    if (addr) {
#ifdef CONFIG_STACKTRACE
        struct stack_trace trace;
        int i;

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

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

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

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

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

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

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

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

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

static void print_page_info(struct page *page)
{
    printk(KERN_ERR "INFO: Slab 0x%p objects=%u used=%u fp=0x%p flags=0x%04lx\n",
        page, page->objects, page->inuse, page->freelist, page->flags);

}

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

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

    add_taint(TAINT_BAD_PAGE);
}

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

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

static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
{
    unsigned int off;   /* Offset of last byte */
    u8 *addr = page_address(page);

    print_tracking(s, p);

    print_page_info(page);

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

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

    print_section("Object ", p, min_t(unsigned long, s->object_size,
                PAGE_SIZE));
    if (s->flags & SLAB_RED_ZONE)
        print_section("Redzone ", p + s->object_size,
            s->inuse - s->object_size);

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

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

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

    dump_stack();
}

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

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

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

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

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

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

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

static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
            u8 *object, char *what,
            u8 *start, unsigned int value, unsigned int bytes)
{
    u8 *fault;
    u8 *end;

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

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

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

    restore_bytes(s, what, value, fault, end);
    return 0;
}

/*
 * Object layout:
 *
 * object address
 *  Bytes of the object to be managed.
 *  If the freepointer may overlay the object then the free
 *  pointer is the first word of the object.
 *
 *  Poisoning uses 0x6b (POISON_FREE) and the last byte is
 *  0xa5 (POISON_END)
 *
 * object + s->object_size
 *  Padding to reach word boundary. This is also used for Redzoning.
 *  Padding is extended by another word if Redzoning is enabled and
 *  object_size == inuse.
 *
 *  We fill with 0xbb (RED_INACTIVE) for inactive objects and with
 *  0xcc (RED_ACTIVE) for objects in use.
 *
 * object + s->inuse
 *  Meta data starts here.
 *
 *  A. Free pointer (if we cannot overwrite object on free)
 *  B. Tracking data for SLAB_STORE_USER
 *  C. Padding to reach required alignment boundary or at mininum
 *      one word if debugging is on to be able to detect writes
 *      before the word boundary.
 *
 *  Padding is done using 0x5a (POISON_INUSE)
 *
 * object + s->size
 *  Nothing is used beyond s->size.
 *
 * If slabcaches are merged then the object_size and inuse boundaries are mostly
 * ignored. And therefore no slab options that rely on these boundaries
 * may be used with merged slabcaches.
 */

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

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

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

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

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

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

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

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

    fault = memchr_inv(end - remainder, POISON_INUSE, remainder);
    if (!fault)
        return 1;
    while (end > fault && end[-1] == POISON_INUSE)
        end--;

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

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

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

    if (s->flags & SLAB_RED_ZONE) {
        if (!check_bytes_and_report(s, page, object, "Redzone",
            endobject, val, s->inuse - s->object_size))
            return 0;
    } else {
        if ((s->flags & SLAB_POISON) && s->object_size < s->inuse) {
            check_bytes_and_report(s, page, p, "Alignment padding",
                endobject, POISON_INUSE, s->inuse - s->object_size);
        }
    }

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

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

    /* Check free pointer validity */
    if (!check_valid_pointer(s, page, get_freepointer(s, p))) {
        object_err(s, page, p, "Freepointer corrupt");
        /*
         * No choice but to zap it and thus lose the remainder
         * of the free objects in this slab. May cause
         * another error because the object count is now wrong.
         */
        set_freepointer(s, p, NULL);
        return 0;
    }
    return 1;
}

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

    VM_BUG_ON(!irqs_disabled());

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

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

/*
 * Determine if a certain object on a page is on the freelist. Must hold the
 * slab lock to guarantee that the chains are in a consistent state.
 */
static int on_freelist(struct kmem_cache *s, struct page *page, void *search)
{
    int nr = 0;
    void *fp;
    void *object = NULL;
    unsigned long max_objects;

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

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

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

static void trace(struct kmem_cache *s, struct page *page, void *object,
                                int alloc)
{
    if (s->flags & SLAB_TRACE) {
        printk(KERN_INFO "TRACE %s %s 0x%p inuse=%d fp=0x%p\n",
            s->name,
            alloc ? "alloc" : "free",
            object, page->inuse,
            page->freelist);

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

        dump_stack();
    }
}

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

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

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

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

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

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

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

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

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

    list_del(&page->lru);
}

/* Tracking of the number of slabs for debugging purposes */
static inline unsigned long slabs_node(struct kmem_cache *s, int node)
{
    struct kmem_cache_node *n = get_node(s, node);

    return atomic_long_read(&n->nr_slabs);
}

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

static inline void inc_slabs_node(struct kmem_cache *s, int node, int objects)
{
    struct kmem_cache_node *n = get_node(s, node);

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

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

/* Object debug checks for alloc/free paths */
static void setup_object_debug(struct kmem_cache *s, struct page *page,
                                void *object)
{
    if (!(s->flags & (SLAB_STORE_USER|SLAB_RED_ZONE|__OBJECT_POISON)))
        return;

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

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

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

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

    /* Success perform special debug activities for allocs */
    if (s->flags & SLAB_STORE_USER)
        set_track(s, object, TRACK_ALLOC, addr);
    trace(s, page, object, 1);
    init_object(s, object, SLUB_RED_ACTIVE);
    return 1;

bad:
    if (PageSlab(page)) {
        /*
         * If this is a slab page then lets do the best we can
         * to avoid issues in the future. Marking all objects
         * as used avoids touching the remaining objects.
         */
        slab_fix(s, "Marking all objects used");
        page->inuse = page->objects;
        page->freelist = NULL;
    }
    return 0;
}

static noinline struct kmem_cache_node *free_debug_processing(
    struct kmem_cache *s, struct page *page, void *object,
    unsigned long addr, unsigned long *flags)
{
    struct kmem_cache_node *n = get_node(s, page_to_nid(page));

    spin_lock_irqsave(&n->list_lock, *flags);
    slab_lock(page);

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

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

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

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

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

    if (s->flags & SLAB_STORE_USER)
        set_track(s, object, TRACK_FREE, addr);
    trace(s, page, object, 0);
    init_object(s, object, SLUB_RED_INACTIVE);
out:
    slab_unlock(page);
    /*
     * Keep node_lock to preserve integrity
     * until the object is actually freed
     */
    return n;

fail:
    slab_unlock(page);
    spin_unlock_irqrestore(&n->list_lock, *flags);
    slab_fix(s, "Object at 0x%p not freed", object);
    return NULL;
}

static int __init setup_slub_debug(char *str)
{
    slub_debug = DEBUG_DEFAULT_FLAGS;
    if (*str++ != '=' || !*str)
        /*
         * No options specified. Switch on full debugging.
         */
        goto out;

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

    if (tolower(*str) == 'o') {
        /*
         * Avoid enabling debugging on caches if its minimum order
         * would increase as a result.
         */
        disable_higher_order_debug = 1;
        goto out;
    }

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

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

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

__setup("slub_debug", setup_slub_debug);

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

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

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

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

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

#define disable_higher_order_debug 0

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

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

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

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

#endif /* CONFIG_SLUB_DEBUG */

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

    flags |= __GFP_NOTRACK;

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

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

    flags &= gfp_allowed_mask;

    if (flags & __GFP_WAIT)
        local_irq_enable();

    flags |= s->allocflags;

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

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

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

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

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

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

    if (flags & __GFP_WAIT)
        local_irq_disable();
    if (!page)
        return NULL;

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

    return page;
}

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

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

    BUG_ON(flags & GFP_SLAB_BUG_MASK);

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

    inc_slabs_node(s, page_to_nid(page), page->objects);
    page->slab = s;
    __SetPageSlab(page);
    if (page->pfmemalloc)
        SetPageSlabPfmemalloc(page);

    start = page_address(page);

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

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

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

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

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

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

    kmemcheck_free_shadow(page, compound_order(page));

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

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

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

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

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

    __free_slab(page->slab, page);
}

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

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

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

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

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

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

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

/*
 * Remove slab from the partial list, freeze it and
 * return the pointer to the freelist.
 *
 * Returns a list of objects or NULL if it fails.
 *
 * Must hold list_lock since we modify the partial list.
 */
static inline void *acquire_slab(struct kmem_cache *s,
        struct kmem_cache_node *n, struct page *page,
        int mode)
{
    void *freelist;
    unsigned long counters;
    struct page new;

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

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

    if (!__cmpxchg_double_slab(s, page,
            freelist, counters,
            new.freelist, new.counters,
            "acquire_slab"))
        return NULL;

    remove_partial(n, page);
    WARN_ON(!freelist);
    return freelist;
}

static int put_cpu_partial(struct kmem_cache *s, struct page *page, int drain);
static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags);

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

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

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

        if (!pfmemalloc_match(page, flags))
            continue;

        t = acquire_slab(s, n, page, object == NULL);
        if (!t)
            break;

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

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

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

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

    do {
        cpuset_mems_cookie = get_mems_allowed();
        zonelist = node_zonelist(slab_node(), flags);
        for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
            struct kmem_cache_node *n;

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

            if (n && cpuset_zone_allowed_hardwall(zone, flags) &&
                    n->nr_partial > s->min_partial) {
                object = get_partial_node(s, n, c, flags);
                if (object) {
                    /*
                     * Return the object even if
                     * put_mems_allowed indicated that
                     * the cpuset mems_allowed was
                     * updated in parallel. It's a
                     * harmless race between the alloc
                     * and the cpuset update.
                     */
                    put_mems_allowed(cpuset_mems_cookie);
                    return object;
                }
            }
        }
    } while (!put_mems_allowed(cpuset_mems_cookie));
#endif
    return NULL;
}

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

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

    return get_any_partial(s, flags, c);
}

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

        freelist = nextfree;
    }

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

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

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

    new.frozen = 0;

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

    if (l != m) {

        if (l == M_PARTIAL)

            remove_partial(n, page);

        else if (l == M_FULL)

            remove_full(s, page);

        if (m == M_PARTIAL) {

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

        } else if (m == M_FULL) {

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

        }
    }

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

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

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

/*
 * Unfreeze all the cpu partial slabs.
 *
 * This function must be called with interrupt disabled.
 */
static void unfreeze_partials(struct kmem_cache *s)
{
    struct kmem_cache_node *n = NULL, *n2 = NULL;
    struct kmem_cache_cpu *c = this_cpu_ptr(s->cpu_slab);
    struct page *page, *discard_page = NULL;

    while ((page = c->partial)) {
        struct page new;
        struct page old;

        c->partial = page->next;

        n2 = get_node(s, page_to_nid(page));
        if (n != n2) {
            if (n)
                spin_unlock(&n->list_lock);

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

        do {

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

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

            new.frozen = 0;

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

        if (unlikely(!new.inuse && n->nr_partial > s->min_partial)) {
            page->next = discard_page;
            discard_page = page;
        } else {
            add_partial(n, page, DEACTIVATE_TO_TAIL);
            stat(s, FREE_ADD_PARTIAL);
        }
    }

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

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

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

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

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

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

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

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

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

static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
{
    stat(s, CPUSLAB_FLUSH);
    deactivate_slab(s, c->page, c->freelist);

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

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

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

        unfreeze_partials(s);
    }
}

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

    __flush_cpu_slab(s, smp_processor_id());
}

static bool has_cpu_slab(int cpu, void *info)
{
    struct kmem_cache *s = info;
    struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);

    return c->page || c->partial;
}

static void flush_all(struct kmem_cache *s)
{
    on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1, GFP_ATOMIC);
}

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

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

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

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

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

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

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

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

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

        if (!n)
            continue;

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

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

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

    freelist = get_partial(s, flags, node, c);

    if (freelist)
        return freelist;

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

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

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

    return freelist;
}

static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags)
{
    if (unlikely(PageSlabPfmemalloc(page)))
        return gfp_pfmemalloc_allowed(gfpflags);

    return true;
}

/*
 * Check the page->freelist of a page and either transfer the freelist to the per cpu freelist
 * or deactivate the page.
 *
 * The page is still frozen if the return value is not NULL.
 *
 * If this function returns NULL then the page has been unfrozen.
 *
 * This function must be called with interrupt disabled.
 */
static inline void *get_freelist(struct kmem_cache *s, struct page *page)
{
    struct page new;
    unsigned long counters;
    void *freelist;

    do {
        freelist = page->freelist;
        counters = page->counters;

        new.counters = counters;
        VM_BUG_ON(!new.frozen);

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

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

    return freelist;
}

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

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

    page = c->page;
    if (!page)
        goto new_slab;
redo:

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

    /*
     * By rights, we should be searching for a slab page that was
     * PFMEMALLOC but right now, we are losing the pfmemalloc
     * information when the page leaves the per-cpu allocator
     */
    if (unlikely(!pfmemalloc_match(page, gfpflags))) {
        deactivate_slab(s, page, c->freelist);
        c->page = NULL;
        c->freelist = NULL;
        goto new_slab;
    }

    /* must check again c->freelist in case of cpu migration or IRQ */
    freelist = c->freelist;
    if (freelist)
        goto load_freelist;

    stat(s, ALLOC_SLOWPATH);

    freelist = get_freelist(s, page);

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

    stat(s, ALLOC_REFILL);

load_freelist:
    /*
     * freelist is pointing to the list of objects to be used.
     * page is pointing to the page from which the objects are obtained.
     * That page must be frozen for per cpu allocations to work.
     */
    VM_BUG_ON(!c->page->frozen);
    c->freelist = get_freepointer(s, freelist);
    c->tid = next_tid(c->tid);
    local_irq_restore(flags);
    return freelist;

new_slab:

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

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

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

        local_irq_restore(flags);
        return NULL;
    }

    page = c->page;
    if (likely(!kmem_cache_debug(s) && pfmemalloc_match(page, gfpflags)))
        goto load_freelist;

    /* Only entered in the debug case */
    if (kmem_cache_debug(s) && !alloc_debug_processing(s, page, freelist, addr))
        goto new_slab;  /* Slab failed checks. Next slab needed */

    deactivate_slab(s, page, get_freepointer(s, freelist));
    c->page = NULL;
    c->freelist = NULL;
    local_irq_restore(flags);
    return freelist;
}

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

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

redo:

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

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

    object = c->freelist;
    page = c->page;
    if (unlikely(!object || !node_match(page, node)))
        object = __slab_alloc(s, gfpflags, node, addr, c);

    else {
        void *next_object = get_freepointer_safe(s, object);

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

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

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

    slab_post_alloc_hook(s, gfpflags, object);

    return object;
}

static __always_inline void *slab_alloc(struct kmem_cache *s,
        gfp_t gfpflags, unsigned long addr)
{
    return slab_alloc_node(s, gfpflags, NUMA_NO_NODE, addr);
}

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

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

    return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc);

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

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

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

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

    return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_node);

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

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

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

    stat(s, FREE_SLOWPATH);

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

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

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

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

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

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

            }
        }
        inuse = new.inuse;

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

    if (likely(!n)) {

        /*
         * If we just froze the page then put it onto the
         * per cpu partial list.
         */
        if (new.frozen && !was_frozen) {
            put_cpu_partial(s, page, 1);
            stat(s, CPU_PARTIAL_FREE);
        }
        /*
         * The list lock was not taken therefore no list
         * activity can be necessary.
         */
                if (was_frozen)
                        stat(s, FREE_FROZEN);
                return;
        }

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

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

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

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

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

    slab_free_hook(s, x);

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

    tid = c->tid;
    barrier();

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

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

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

}

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

    page = virt_to_head_page(x);

    if (kmem_cache_debug(s) && page->slab != s) {
        pr_err("kmem_cache_free: Wrong slab cache. %s but object"
            " is from  %s\n", page->slab->name, s->name);
        WARN_ON_ONCE(1);
        return;
    }

    slab_free(s, page, x, _RET_IP_);

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

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

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

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

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

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

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

        unsigned long slab_size = PAGE_SIZE << order;

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

        rem = (slab_size - reserved) % size;

        if (rem <= slab_size / fract_leftover)
            break;

    }

    return order;
}

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

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

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

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

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

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

    if (align < ARCH_SLAB_MINALIGN)
        align = ARCH_SLAB_MINALIGN;

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

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

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

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

    if (!s->cpu_slab)
        return 0;

    init_kmem_cache_cpus(s);

    return 1;
}

static struct kmem_cache *kmem_cache_node;

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

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

    page = new_slab(kmem_cache_node, GFP_NOWAIT, node);

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

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

    add_partial(n, page, DEACTIVATE_TO_HEAD);
}

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

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

        if (n)
            kmem_cache_free(kmem_cache_node, n);

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

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

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

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

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

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

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

/*
 * calculate_sizes() determines the order and the distribution of data within
 * a slab object.
 */
static int calculate_sizes(struct kmem_cache *s, int forced_order)
{
    unsigned long flags = s->flags;
    unsigned long size = s->object_size;
    unsigned long align = s->align;
    int order;

    /*
     * Round up object size to the next word boundary. We can only
     * place the free pointer at word boundaries and this determines
     * the possible location of the free pointer.
     */
    size = ALIGN(size, sizeof(void *));

#ifdef CONFIG_SLUB_DEBUG
    /*
     * Determine if we can poison the object itself. If the user of
     * the slab may touch the object after free or before allocation
     * then we should never poison the object itself.
     */
    if ((flags & SLAB_POISON) && !(flags & SLAB_DESTROY_BY_RCU) &&
            !s->ctor)
        s->flags |= __OBJECT_POISON;
    else
        s->flags &= ~__OBJECT_POISON;


    /*
     * If we are Redzoning then check if there is some space between the
     * end of the object and the free pointer. If not then add an
     * additional word to have some bytes to store Redzone information.
     */
    if ((flags & SLAB_RED_ZONE) && size == s->object_size)
        size += sizeof(void *);
#endif

    /*
     * With that we have determined the number of bytes in actual use
     * by the object. This is the potential offset to the free pointer.
     */
    s->inuse = size;

    if (((flags & (SLAB_DESTROY_BY_RCU | SLAB_POISON)) ||
        s->ctor)) {
        /*
         * Relocate free pointer after the object if it is not
         * permitted to overwrite the first word of the object on
         * kmem_cache_free.
         *
         * This is the case if we do RCU, have a constructor or
         * destructor or are poisoning the objects.
         */
        s->offset = size;
        size += sizeof(void *);
    }

#ifdef CONFIG_SLUB_DEBUG
    if (flags & SLAB_STORE_USER)
        /*
         * Need to store information about allocs and frees after
         * the object.
         */
        size += 2 * sizeof(struct track);

    if (flags & SLAB_RED_ZONE)
        /*
         * Add some empty padding so that we can catch
         * overwrites from earlier objects rather than let
         * tracking information or the free pointer be
         * corrupted if a user writes before the start
         * of the object.
         */
        size += sizeof(void *);
#endif

    /*
     * Determine the alignment based on various parameters that the
     * user specified and the dynamic determination of cache line size
     * on bootup.
     */
    align = calculate_alignment(flags, align, s->object_size);
    s->align = align;

    /*
     * SLUB stores one object immediately after another beginning from
     * offset 0. In order to align the objects we have to simply size
     * each object to conform to the alignment.
     */
    size = ALIGN(size, align);
    s->size = size;
    if (forced_order >= 0)
        order = forced_order;
    else
        order = calculate_order(size, s->reserved);

    if (order < 0)
        return 0;

    s->allocflags = 0;
    if (order)
        s->allocflags |= __GFP_COMP;

    if (s->flags & SLAB_CACHE_DMA)
        s->allocflags |= SLUB_DMA;

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

    /*
     * Determine the number of objects per slab
     */
    s->oo = oo_make(order, size, s->reserved);
    s->min = oo_make(get_order(size), size, s->reserved);
    if (oo_objects(s->oo) > oo_objects(s->max))
        s->max = s->oo;

    return !!oo_objects(s->oo);

}

static int kmem_cache_open(struct kmem_cache *s, unsigned long flags)
{
    s->flags = kmem_cache_flags(s->size, flags, s->name, s->ctor);
    s->reserved = 0;

    if (need_reserve_slab_rcu && (s->flags & SLAB_DESTROY_BY_RCU))
        s->reserved = sizeof(struct rcu_head);

    if (!calculate_sizes(s, -1))
        goto error;
    if (disable_higher_order_debug) {
        /*
         * Disable debugging flags that store metadata if the min slab
         * order increased.
         */
        if (get_order(s->size) > get_order(s->object_size)) {
            s->flags &= ~DEBUG_METADATA_FLAGS;
            s->offset = 0;
            if (!calculate_sizes(s, -1))
                goto error;
        }
    }

#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
    if (system_has_cmpxchg_double() && (s->flags & SLAB_DEBUG_FLAGS) == 0)
        /* Enable fast mode */
        s->flags |= __CMPXCHG_DOUBLE;
#endif

    /*
     * The larger the object size is, the more pages we want on the partial
     * list to avoid pounding the page allocator excessively.
     */
    set_min_partial(s, ilog2(s->size) / 2);

    /*
     * cpu_partial determined the maximum number of objects kept in the
     * per cpu partial lists of a processor.
     *
     * Per cpu partial lists mainly contain slabs that just have one
     * object freed. If they are used for allocation then they can be
     * filled up again with minimal effort. The slab will never hit the
     * per node partial lists and therefore no locking will be required.
     *
     * This setting also determines
     *
     * A) The number of objects from per cpu partial slabs dumped to the
     *    per node list when we reach the limit.
     * B) The number of objects in cpu partial slabs to extract from the
     *    per node list when we run out of per cpu objects. We only fetch 50%
     *    to keep some capacity around for frees.
     */
    if (kmem_cache_debug(s))
        s->cpu_partial = 0;
    else if (s->size >= PAGE_SIZE)
        s->cpu_partial = 2;
    else if (s->size >= 1024)
        s->cpu_partial = 6;
    else if (s->size >= 256)
        s->cpu_partial = 13;
    else
        s->cpu_partial = 30;

#ifdef CONFIG_NUMA
    s->remote_node_defrag_ratio = 1000;
#endif
    if (!init_kmem_cache_nodes(s))
        goto error;

    if (alloc_kmem_cache_cpus(s))
        return 0;

    free_kmem_cache_nodes(s);
error:
    if (flags & SLAB_PANIC)
        panic("Cannot create slab %s size=%lu realsize=%u "
            "order=%u offset=%u flags=%lx\n",
            s->name, (unsigned long)s->size, s->size, oo_order(s->oo),
            s->offset, flags);
    return -EINVAL;
}

/*
 * Determine the size of a slab object
 */
unsigned int kmem_cache_size(struct kmem_cache *s)
{
    return s->object_size;
}
EXPORT_SYMBOL(kmem_cache_size);

static void list_slab_objects(struct kmem_cache *s, struct page *page,
                            const char *text)
{
#ifdef CONFIG_SLUB_DEBUG
    void *addr = page_address(page);
    void *p;
    unsigned long *map = kzalloc(BITS_TO_LONGS(page->objects) *
                     sizeof(long), GFP_ATOMIC);
    if (!map)
        return;
    slab_err(s, page, text, s->name);
    slab_lock(page);

    get_map(s, page, map);
    for_each_object(p, s, addr, page->objects) {

        if (!test_bit(slab_index(p, s, addr), map)) {
            printk(KERN_ERR "INFO: Object 0x%p @offset=%tu\n",
                            p, p - addr);
            print_tracking(s, p);
        }
    }
    slab_unlock(page);
    kfree(map);
#endif
}

/*
 * Attempt to free all partial slabs on a node.
 * This is called from kmem_cache_close(). We must be the last thread
 * using the cache and therefore we do not need to lock anymore.
 */
static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
{
    struct page *page, *h;

    list_for_each_entry_safe(page, h, &n->partial, lru) {
        if (!page->inuse) {
            remove_partial(n, page);
            discard_slab(s, page);
        } else {
            list_slab_objects(s, page,
            "Objects remaining in %s on kmem_cache_close()");
        }
    }
}

/*
 * Release all resources used by a slab cache.
 */
static inline int kmem_cache_close(struct kmem_cache *s)
{
    int node;

    flush_all(s);
    /* Attempt to free all objects */
    for_each_node_state(node, N_NORMAL_MEMORY) {
        struct kmem_cache_node *n = get_node(s, node);

        free_partial(s, n);
        if (n->nr_partial || slabs_node(s, node))
            return 1;
    }
    free_percpu(s->cpu_slab);
    free_kmem_cache_nodes(s);
    return 0;
}

int __kmem_cache_shutdown(struct kmem_cache *s)
{
    int rc = kmem_cache_close(s);

    if (!rc)
        sysfs_slab_remove(s);

    return rc;
}

/********************************************************************
 *      Kmalloc subsystem
 *******************************************************************/

struct kmem_cache *kmalloc_caches[SLUB_PAGE_SHIFT];
EXPORT_SYMBOL(kmalloc_caches);

#ifdef CONFIG_ZONE_DMA
static struct kmem_cache *kmalloc_dma_caches[SLUB_PAGE_SHIFT];
#endif

static int __init setup_slub_min_order(char *str)
{
    get_option(&str, &slub_min_order);

    return 1;
}

__setup("slub_min_order=", setup_slub_min_order);

static int __init setup_slub_max_order(char *str)
{
    get_option(&str, &slub_max_order);
    slub_max_order = min(slub_max_order, MAX_ORDER - 1);

    return 1;
}

__setup("slub_max_order=", setup_slub_max_order);

static int __init setup_slub_min_objects(char *str)
{
    get_option(&str, &slub_min_objects);

    return 1;
}

__setup("slub_min_objects=", setup_slub_min_objects);

static int __init setup_slub_nomerge(char *str)
{
    slub_nomerge = 1;
    return 1;
}

__setup("slub_nomerge", setup_slub_nomerge);

static struct kmem_cache *__init create_kmalloc_cache(const char *name,
                        int size, unsigned int flags)
{
    struct kmem_cache *s;

    s = kmem_cache_zalloc(kmem_cache, GFP_NOWAIT);

    s->name = name;
    s->size = s->object_size = size;
    s->align = ARCH_KMALLOC_MINALIGN;

    /*
     * This function is called with IRQs disabled during early-boot on
     * single CPU so there's no need to take slab_mutex here.
     */
    if (kmem_cache_open(s, flags))
        goto panic;

    list_add(&s->list, &slab_caches);
    return s;

panic:
    panic("Creation of kmalloc slab %s size=%d failed.\n", name, size);
    return NULL;
}

/*
 * Conversion table for small slabs sizes / 8 to the index in the
 * kmalloc array. This is necessary for slabs < 192 since we have non power
 * of two cache sizes there. The size of larger slabs can be determined using
 * fls.
 */
static s8 size_index[24] = {
    3,  /* 8 */
    4,  /* 16 */
    5,  /* 24 */
    5,  /* 32 */
    6,  /* 40 */
    6,  /* 48 */
    6,  /* 56 */
    6,  /* 64 */
    1,  /* 72 */
    1,  /* 80 */
    1,  /* 88 */
    1,  /* 96 */
    7,  /* 104 */
    7,  /* 112 */
    7,  /* 120 */
    7,  /* 128 */
    2,  /* 136 */
    2,  /* 144 */
    2,  /* 152 */
    2,  /* 160 */
    2,  /* 168 */
    2,  /* 176 */
    2,  /* 184 */
    2   /* 192 */
};

static inline int size_index_elem(size_t bytes)
{
    return (bytes - 1) / 8;
}

static struct kmem_cache *get_slab(size_t size, gfp_t flags)
{
    int index;

    if (size <= 192) {
        if (!size)
            return ZERO_SIZE_PTR;

        index = size_index[size_index_elem(size)];
    } else
        index = fls(size - 1);

#ifdef CONFIG_ZONE_DMA
    if (unlikely((flags & SLUB_DMA)))
        return kmalloc_dma_caches[index];

#endif
    return kmalloc_caches[index];
}

void *__kmalloc(size_t size, gfp_t flags)
{
    struct kmem_cache *s;
    void *ret;

    if (unlikely(size > SLUB_MAX_SIZE))
        return kmalloc_large(size, flags);

    s = get_slab(size, flags);

    if (unlikely(ZERO_OR_NULL_PTR(s)))
        return s;

    ret = slab_alloc(s, flags, _RET_IP_);

    trace_kmalloc(_RET_IP_, ret, size, s->size, flags);

    return ret;
}
EXPORT_SYMBOL(__kmalloc);

#ifdef CONFIG_NUMA
static void *kmalloc_large_node(size_t size, gfp_t flags, int node)
{
    struct page *page;
    void *ptr = NULL;

    flags |= __GFP_COMP | __GFP_NOTRACK;
    page = alloc_pages_node(node, flags, get_order(size));
    if (page)
        ptr = page_address(page);

    kmemleak_alloc(ptr, size, 1, flags);
    return ptr;
}

void *__kmalloc_node(size_t size, gfp_t flags, int node)
{
    struct kmem_cache *s;
    void *ret;

    if (unlikely(size > SLUB_MAX_SIZE)) {
        ret = kmalloc_large_node(size, flags, node);

        trace_kmalloc_node(_RET_IP_, ret,
                   size, PAGE_SIZE << get_order(size),
                   flags, node);

        return ret;
    }

    s = get_slab(size, flags);

    if (unlikely(ZERO_OR_NULL_PTR(s)))
        return s;

    ret = slab_alloc_node(s, flags, node, _RET_IP_);

    trace_kmalloc_node(_RET_IP_, ret, size, s->size, flags, node);

    return ret;
}
EXPORT_SYMBOL(__kmalloc_node);
#endif

size_t ksize(const void *object)
{
    struct page *page;

    if (unlikely(object == ZERO_SIZE_PTR))
        return 0;

    page = virt_to_head_page(object);

    if (unlikely(!PageSlab(page))) {
        WARN_ON(!PageCompound(page));
        return PAGE_SIZE << compound_order(page);
    }

    return slab_ksize(page->slab);
}
EXPORT_SYMBOL(ksize);

#ifdef CONFIG_SLUB_DEBUG
bool verify_mem_not_deleted(const void *x)
{
    struct page *page;
    void *object = (void *)x;
    unsigned long flags;
    bool rv;

    if (unlikely(ZERO_OR_NULL_PTR(x)))
        return false;

    local_irq_save(flags);

    page = virt_to_head_page(x);
    if (unlikely(!PageSlab(page))) {
        /* maybe it was from stack? */
        rv = true;
        goto out_unlock;
    }

    slab_lock(page);
    if (on_freelist(page->slab, page, object)) {
        object_err(page->slab, page, object, "Object is on free-list");
        rv = false;
    } else {
        rv = true;
    }
    slab_unlock(page);

out_unlock:
    local_irq_restore(flags);
    return rv;
}
EXPORT_SYMBOL(verify_mem_not_deleted);
#endif

void kfree(const void *x)
{
    struct page *page;
    void *object = (void *)x;

    trace_kfree(_RET_IP_, x);

    if (unlikely(ZERO_OR_NULL_PTR(x)))
        return;

    page = virt_to_head_page(x);
    if (unlikely(!PageSlab(page))) {
        BUG_ON(!PageCompound(page));
        kmemleak_free(x);
        __free_pages(page, compound_order(page));
        return;
    }
    slab_free(page->slab, page, object, _RET_IP_);
}
EXPORT_SYMBOL(kfree);

/*
 * kmem_cache_shrink removes empty slabs from the partial lists and sorts
 * the remaining slabs by the number of items in use. The slabs with the
 * most items in use come first. New allocations will then fill those up
 * and thus they can be removed from the partial lists.
 *
 * The slabs with the least items are placed last. This results in them
 * being allocated from last increasing the chance that the last objects
 * are freed in them.
 */
int kmem_cache_shrink(struct kmem_cache *s)
{
    int node;
    int i;
    struct kmem_cache_node *n;
    struct page *page;
    struct page *t;
    int objects = oo_objects(s->max);
    struct list_head *slabs_by_inuse =
        kmalloc(sizeof(struct list_head) * objects, GFP_KERNEL);
    unsigned long flags;

    if (!slabs_by_inuse)
        return -ENOMEM;

    flush_all(s);
    for_each_node_state(node, N_NORMAL_MEMORY) {
        n = get_node(s, node);

        if (!n->nr_partial)
            continue;

        for (i = 0; i < objects; i++)
            INIT_LIST_HEAD(slabs_by_inuse + i);

        spin_lock_irqsave(&n->list_lock, flags);

        /*
         * Build lists indexed by the items in use in each slab.
         *
         * Note that concurrent frees may occur while we hold the
         * list_lock. page->inuse here is the upper limit.
         */
        list_for_each_entry_safe(page, t, &n->partial, lru) {
            list_move(&page->lru, slabs_by_inuse + page->inuse);
            if (!page->inuse)
                n->nr_partial--;
        }

        /*
         * Rebuild the partial list with the slabs filled up most
         * first and the least used slabs at the end.
         */
        for (i = objects - 1; i > 0; i--)
            list_splice(slabs_by_inuse + i, n->partial.prev);

        spin_unlock_irqrestore(&n->list_lock, flags);

        /* Release empty slabs */
        list_for_each_entry_safe(page, t, slabs_by_inuse, lru)
            discard_slab(s, page);
    }

    kfree(slabs_by_inuse);
    return 0;
}
EXPORT_SYMBOL(kmem_cache_shrink);

#if defined(CONFIG_MEMORY_HOTPLUG)
static int slab_mem_going_offline_callback(void *arg)
{
    struct kmem_cache *s;

    mutex_lock(&slab_mutex);
    list_for_each_entry(s, &slab_caches, list)
        kmem_cache_shrink(s);
    mutex_unlock(&slab_mutex);

    return 0;
}

static void slab_mem_offline_callback(void *arg)
{
    struct kmem_cache_node *n;
    struct kmem_cache *s;
    struct memory_notify *marg = arg;
    int offline_node;

    offline_node = marg->status_change_nid;

    /*
     * If the node still has available memory. we need kmem_cache_node
     * for it yet.
     */
    if (offline_node < 0)
        return;

    mutex_lock(&slab_mutex);
    list_for_each_entry(s, &slab_caches, list) {
        n = get_node(s, offline_node);
        if (n) {
            /*
             * if n->nr_slabs > 0, slabs still exist on the node
             * that is going down. We were unable to free them,
             * and offline_pages() function shouldn't call this
             * callback. So, we must fail.
             */
            BUG_ON(slabs_node(s, offline_node));

            s->node[offline_node] = NULL;
            kmem_cache_free(kmem_cache_node, n);
        }
    }
    mutex_unlock(&slab_mutex);
}

static int slab_mem_going_online_callback(void *arg)
{
    struct kmem_cache_node *n;
    struct kmem_cache *s;
    struct memory_notify *marg = arg;
    int nid = marg->status_change_nid;
    int ret = 0;

    /*
     * If the node's memory is already available, then kmem_cache_node is
     * already created. Nothing to do.
     */
    if (nid < 0)
        return 0;

    /*
     * We are bringing a node online. No memory is available yet. We must
     * allocate a kmem_cache_node structure in order to bring the node
     * online.
     */
    mutex_lock(&slab_mutex);
    list_for_each_entry(s, &slab_caches, list) {
        /*
         * XXX: kmem_cache_alloc_node will fallback to other nodes
         *      since memory is not yet available from the node that
         *      is brought up.
         */
        n = kmem_cache_alloc(kmem_cache_node, GFP_KERNEL);
        if (!n) {
            ret = -ENOMEM;
            goto out;
        }
        init_kmem_cache_node(n);
        s->node[nid] = n;
    }
out:
    mutex_unlock(&slab_mutex);
    return ret;
}

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

    switch (action) {
    case MEM_GOING_ONLINE:
        ret = slab_mem_going_online_callback(arg);
        break;
    case MEM_GOING_OFFLINE:
        ret = slab_mem_going_offline_callback(arg);
        break;
    case MEM_OFFLINE:
    case MEM_CANCEL_ONLINE:
        slab_mem_offline_callback(arg);
        break;
    case MEM_ONLINE:
    case MEM_CANCEL_OFFLINE:
        break;
    }
    if (ret)
        ret = notifier_from_errno(ret);
    else
        ret = NOTIFY_OK;
    return ret;
}

#endif /* CONFIG_MEMORY_HOTPLUG */

/********************************************************************
 *          Basic setup of slabs
 *******************************************************************/

/*
 * Used for early kmem_cache structures that were allocated using
 * the page allocator
 */

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

    list_add(&s->list, &slab_caches);
    s->refcount = -1;

    for_each_node_state(node, N_NORMAL_MEMORY) {
        struct kmem_cache_node *n = get_node(s, node);
        struct page *p;

        if (n) {
            list_for_each_entry(p, &n->partial, lru)
                p->slab = s;

#ifdef CONFIG_SLUB_DEBUG
            list_for_each_entry(p, &n->full, lru)
                p->slab = s;
#endif
        }
    }
}

void __init kmem_cache_init(void)
{
    int i;
    int caches = 0;
    struct kmem_cache *temp_kmem_cache;
    int order;
    struct kmem_cache *temp_kmem_cache_node;
    unsigned long kmalloc_size;

    if (debug_guardpage_minorder())
        slub_max_order = 0;

    kmem_size = offsetof(struct kmem_cache, node) +
            nr_node_ids * sizeof(struct kmem_cache_node *);

    /* Allocate two kmem_caches from the page allocator */
    kmalloc_size = ALIGN(kmem_size, cache_line_size());
    order = get_order(2 * kmalloc_size);
    kmem_cache = (void *)__get_free_pages(GFP_NOWAIT | __GFP_ZERO, order);

    /*
     * Must first have the slab cache available for the allocations of the
     * struct kmem_cache_node's. There is special bootstrap code in
     * kmem_cache_open for slab_state == DOWN.
     */
    kmem_cache_node = (void *)kmem_cache + kmalloc_size;

    kmem_cache_node->name = "kmem_cache_node";
    kmem_cache_node->size = kmem_cache_node->object_size =
        sizeof(struct kmem_cache_node);
    kmem_cache_open(kmem_cache_node, SLAB_HWCACHE_ALIGN | SLAB_PANIC);

    hotplug_memory_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);

    /* Able to allocate the per node structures */
    slab_state = PARTIAL;

    temp_kmem_cache = kmem_cache;
    kmem_cache->name = "kmem_cache";
    kmem_cache->size = kmem_cache->object_size = kmem_size;
    kmem_cache_open(kmem_cache, SLAB_HWCACHE_ALIGN | SLAB_PANIC);

    kmem_cache = kmem_cache_alloc(kmem_cache, GFP_NOWAIT);
    memcpy(kmem_cache, temp_kmem_cache, kmem_size);

    /*
     * Allocate kmem_cache_node properly from the kmem_cache slab.
     * kmem_cache_node is separately allocated so no need to
     * update any list pointers.
     */
    temp_kmem_cache_node = kmem_cache_node;

    kmem_cache_node = kmem_cache_alloc(kmem_cache, GFP_NOWAIT);
    memcpy(kmem_cache_node, temp_kmem_cache_node, kmem_size);

    kmem_cache_bootstrap_fixup(kmem_cache_node);

    caches++;
    kmem_cache_bootstrap_fixup(kmem_cache);
    caches++;
    /* Free temporary boot structure */
    free_pages((unsigned long)temp_kmem_cache, order);

    /* Now we can use the kmem_cache to allocate kmalloc slabs */

    /*
     * Patch up the size_index table if we have strange large alignment
     * requirements for the kmalloc array. This is only the case for
     * MIPS it seems. The standard arches will not generate any code here.
     *
     * Largest permitted alignment is 256 bytes due to the way we
     * handle the index determination for the smaller caches.
     *
     * Make sure that nothing crazy happens if someone starts tinkering
     * around with ARCH_KMALLOC_MINALIGN
     */
    BUILD_BUG_ON(KMALLOC_MIN_SIZE > 256 ||
        (KMALLOC_MIN_SIZE & (KMALLOC_MIN_SIZE - 1)));

    for (i = 8; i < KMALLOC_MIN_SIZE; i += 8) {
        int elem = size_index_elem(i);
        if (elem >= ARRAY_SIZE(size_index))
            break;
        size_index[elem] = KMALLOC_SHIFT_LOW;
    }

    if (KMALLOC_MIN_SIZE == 64) {
        /*
         * The 96 byte size cache is not used if the alignment
         * is 64 byte.
         */
        for (i = 64 + 8; i <= 96; i += 8)
            size_index[size_index_elem(i)] = 7;
    } else if (KMALLOC_MIN_SIZE == 128) {
        /*
         * The 192 byte sized cache is not used if the alignment
         * is 128 byte. Redirect kmalloc to use the 256 byte cache
         * instead.
         */
        for (i = 128 + 8; i <= 192; i += 8)
            size_index[size_index_elem(i)] = 8;
    }

    /* Caches that are not of the two-to-the-power-of size */
    if (KMALLOC_MIN_SIZE <= 32) {
        kmalloc_caches[1] = create_kmalloc_cache("kmalloc-96", 96, 0);
        caches++;
    }

    if (KMALLOC_MIN_SIZE <= 64) {
        kmalloc_caches[2] = create_kmalloc_cache("kmalloc-192", 192, 0);
        caches++;
    }

    for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
        kmalloc_caches[i] = create_kmalloc_cache("kmalloc", 1 << i, 0);
        caches++;
    }

    slab_state = UP;

    /* Provide the correct kmalloc names now that the caches are up */
    if (KMALLOC_MIN_SIZE <= 32) {
        kmalloc_caches[1]->name = kstrdup(kmalloc_caches[1]->name, GFP_NOWAIT);
        BUG_ON(!kmalloc_caches[1]->name);
    }

    if (KMALLOC_MIN_SIZE <= 64) {
        kmalloc_caches[2]->name = kstrdup(kmalloc_caches[2]->name, GFP_NOWAIT);
        BUG_ON(!kmalloc_caches[2]->name);
    }

    for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
        char *s = kasprintf(GFP_NOWAIT, "kmalloc-%d", 1 << i);

        BUG_ON(!s);
        kmalloc_caches[i]->name = s;
    }

#ifdef CONFIG_SMP
    register_cpu_notifier(&slab_notifier);
#endif

#ifdef CONFIG_ZONE_DMA
    for (i = 0; i < SLUB_PAGE_SHIFT; i++) {
        struct kmem_cache *s = kmalloc_caches[i];

        if (s && s->size) {
            char *name = kasprintf(GFP_NOWAIT,
                 "dma-kmalloc-%d", s->object_size);

            BUG_ON(!name);
            kmalloc_dma_caches[i] = create_kmalloc_cache(name,
                s->object_size, SLAB_CACHE_DMA);
        }
    }
#endif
    printk(KERN_INFO
        "SLUB: Genslabs=%d, HWalign=%d, Order=%d-%d, MinObjects=%d,"
        " CPUs=%d, Nodes=%d\n",
        caches, cache_line_size(),
        slub_min_order, slub_max_order, slub_min_objects,
        nr_cpu_ids, nr_node_ids);
}

void __init kmem_cache_init_late(void)
{
}

/*
 * Find a mergeable slab cache
 */
static int slab_unmergeable(struct kmem_cache *s)
{
    if (slub_nomerge || (s->flags & SLUB_NEVER_MERGE))
        return 1;

    if (s->ctor)
        return 1;

    /*
     * We may have set a slab to be unmergeable during bootstrap.
     */
    if (s->refcount < 0)
        return 1;

    return 0;
}

static struct kmem_cache *find_mergeable(size_t size,
        size_t align, unsigned long flags, const char *name,
        void (*ctor)(void *))
{
    struct kmem_cache *s;

    if (slub_nomerge || (flags & SLUB_NEVER_MERGE))
        return NULL;

    if (ctor)
        return NULL;

    size = ALIGN(size, sizeof(void *));
    align = calculate_alignment(flags, align, size);
    size = ALIGN(size, align);
    flags = kmem_cache_flags(size, flags, name, NULL);

    list_for_each_entry(s, &slab_caches, list) {
        if (slab_unmergeable(s))
            continue;

        if (size > s->size)
            continue;

        if ((flags & SLUB_MERGE_SAME) != (s->flags & SLUB_MERGE_SAME))
                continue;
        /*
         * Check if alignment is compatible.
         * Courtesy of Adrian Drzewiecki
         */
        if ((s->size & ~(align - 1)) != s->size)
            continue;

        if (s->size - size >= sizeof(void *))
            continue;

        return s;
    }
    return NULL;
}

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

    s = find_mergeable(size, align, flags, name, ctor);
    if (s) {
        s->refcount++;
        /*
         * Adjust the object sizes so that we clear
         * the complete object on kzalloc.
         */
        s->object_size = max(s->object_size, (int)size);
        s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));

        if (sysfs_slab_alias(s, name)) {
            s->refcount--;
            s = NULL;
        }
    }

    return s;
}

int __kmem_cache_create(struct kmem_cache *s, unsigned long flags)
{
    int err;

    err = kmem_cache_open(s, flags);
    if (err)
        return err;

    mutex_unlock(&slab_mutex);
    err = sysfs_slab_add(s);
    mutex_lock(&slab_mutex);

    if (err)
        kmem_cache_close(s);

    return err;
}

#ifdef CONFIG_SMP
/*
 * Use the cpu notifier to insure that the cpu slabs are flushed when
 * necessary.
 */
static int __cpuinit slab_cpuup_callback(struct notifier_block *nfb,
        unsigned long action, void *hcpu)
{
    long cpu = (long)hcpu;
    struct kmem_cache *s;
    unsigned long flags;

    switch (action) {
    case CPU_UP_CANCELED:
    case CPU_UP_CANCELED_FROZEN:
    case CPU_DEAD:
    case CPU_DEAD_FROZEN:
        mutex_lock(&slab_mutex);
        list_for_each_entry(s, &slab_caches, list) {
            local_irq_save(flags);
            __flush_cpu_slab(s, cpu);
            local_irq_restore(flags);
        }
        mutex_unlock(&slab_mutex);
        break;
    default:
        break;
    }
    return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata slab_notifier = {
    .notifier_call = slab_cpuup_callback
};

#endif

void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, unsigned long caller)
{
    struct kmem_cache *s;
    void *ret;

    if (unlikely(size > SLUB_MAX_SIZE))
        return kmalloc_large(size, gfpflags);

    s = get_slab(size, gfpflags);

    if (unlikely(ZERO_OR_NULL_PTR(s)))
        return s;

    ret = slab_alloc(s, gfpflags, caller);

    /* Honor the call site pointer we received. */
    trace_kmalloc(caller, ret, size, s->size, gfpflags);

    return ret;
}

#ifdef CONFIG_NUMA
void *__kmalloc_node_track_caller(size_t size, gfp_t gfpflags,
                    int node, unsigned long caller)
{
    struct kmem_cache *s;
    void *ret;

    if (unlikely(size > SLUB_MAX_SIZE)) {
        ret = kmalloc_large_node(size, gfpflags, node);

        trace_kmalloc_node(caller, ret,
                   size, PAGE_SIZE << get_order(size),
                   gfpflags, node);

        return ret;
    }

    s = get_slab(size, gfpflags);

    if (unlikely(ZERO_OR_NULL_PTR(s)))
        return s;

    ret = slab_alloc_node(s, gfpflags, node, caller);

    /* Honor the call site pointer we received. */
    trace_kmalloc_node(caller, ret, size, s->size, gfpflags, node);

    return ret;
}
#endif

#ifdef CONFIG_SYSFS
static int count_inuse(struct page *page)
{
    return page->inuse;
}

static int count_total(struct page *page)
{
    return page->objects;
}
#endif

#ifdef CONFIG_SLUB_DEBUG
static int validate_slab(struct kmem_cache *s, struct page *page,
                        unsigned long *map)
{
    void *p;
    void *addr = page_address(page);

    if (!check_slab(s, page) ||
            !on_freelist(s, page, NULL))
        return 0;

    /* Now we know that a valid freelist exists */
    bitmap_zero(map, page->objects);

    get_map(s, page, map);
    for_each_object(p, s, addr, page->objects) {
        if (test_bit(slab_index(p, s, addr), map))
            if (!check_object(s, page, p, SLUB_RED_INACTIVE))
                return 0;
    }

    for_each_object(p, s, addr, page->objects)
        if (!test_bit(slab_index(p, s, addr), map))
            if (!check_object(s, page, p, SLUB_RED_ACTIVE))
                return 0;
    return 1;
}

static void validate_slab_slab(struct kmem_cache *s, struct page *page,
                        unsigned long *map)
{
    slab_lock(page);
    validate_slab(s, page, map);
    slab_unlock(page);
}

static int validate_slab_node(struct kmem_cache *s,
        struct kmem_cache_node *n, unsigned long *map)
{
    unsigned long count = 0;
    struct page *page;
    unsigned long flags;

    spin_lock_irqsave(&n->list_lock, flags);

    list_for_each_entry(page, &n->partial, lru) {
        validate_slab_slab(s, page, map);
        count++;
    }
    if (count != n->nr_partial)
        printk(KERN_ERR "SLUB %s: %ld partial slabs counted but "
            "counter=%ld\n", s->name, count, n->nr_partial);

    if (!(s->flags & SLAB_STORE_USER))
        goto out;

    list_for_each_entry(page, &n->full, lru) {
        validate_slab_slab(s, page, map);
        count++;
    }
    if (count != atomic_long_read(&n->nr_slabs))
        printk(KERN_ERR "SLUB: %s %ld slabs counted but "
            "counter=%ld\n", s->name, count,
            atomic_long_read(&n->nr_slabs));

out:
    spin_unlock_irqrestore(&n->list_lock, flags);
    return count;
}

static long validate_slab_cache(struct kmem_cache *s)
{
    int node;
    unsigned long count = 0;
    unsigned long *map = kmalloc(BITS_TO_LONGS(oo_objects(s->max)) *
                sizeof(unsigned long), GFP_KERNEL);

    if (!map)
        return -ENOMEM;

    flush_all(s);
    for_each_node_state(node, N_NORMAL_MEMORY) {
        struct kmem_cache_node *n = get_node(s, node);

        count += validate_slab_node(s, n, map);
    }
    kfree(map);
    return count;
}
/*
 * Generate lists of code addresses where slabcache objects are allocated
 * and freed.
 */

struct location {
    unsigned long count;
    unsigned long addr;
    long long sum_time;
    long min_time;
    long max_time;
    long min_pid;
    long max_pid;
    DECLARE_BITMAP(cpus, NR_CPUS);
    nodemask_t nodes;
};

struct loc_track {
    unsigned long max;
    unsigned long count;
    struct location *loc;
};

static void free_loc_track(struct loc_track *t)
{
    if (t->max)
        free_pages((unsigned long)t->loc,
            get_order(sizeof(struct location) * t->max));
}

static int alloc_loc_track(struct loc_track *t, unsigned long max, gfp_t flags)
{
    struct location *l;
    int order;

    order = get_order(sizeof(struct location) * max);

    l = (void *)__get_free_pages(flags, order);
    if (!l)
        return 0;

    if (t->count) {
        memcpy(l, t->loc, sizeof(struct location) * t->count);
        free_loc_track(t);
    }
    t->max = max;
    t->loc = l;
    return 1;
}

static int add_location(struct loc_track *t, struct kmem_cache *s,
                const struct track *track)
{
    long start, end, pos;
    struct location *l;
    unsigned long caddr;
    unsigned long age = jiffies - track->when;

    start = -1;
    end = t->count;

    for ( ; ; ) {
        pos = start + (end - start + 1) / 2;

        /*
         * There is nothing at "end". If we end up there
         * we need to add something to before end.
         */
        if (pos == end)
            break;

        caddr = t->loc[pos].addr;
        if (track->addr == caddr) {

            l = &t->loc[pos];
            l->count++;
            if (track->when) {
                l->sum_time += age;
                if (age < l->min_time)
                    l->min_time = age;
                if (age > l->max_time)
                    l->max_time = age;

                if (track->pid < l->min_pid)
                    l->min_pid = track->pid;
                if (track->pid > l->max_pid)
                    l->max_pid = track->pid;

                cpumask_set_cpu(track->cpu,
                        to_cpumask(l->cpus));
            }
            node_set(page_to_nid(virt_to_page(track)), l->nodes);
            return 1;
        }

        if (track->addr < caddr)
            end = pos;
        else
            start = pos;
    }

    /*
     * Not found. Insert new tracking element.
     */
    if (t->count >= t->max && !alloc_loc_track(t, 2 * t->max, GFP_ATOMIC))
        return 0;

    l = t->loc + pos;
    if (pos < t->count)
        memmove(l + 1, l,
            (t->count - pos) * sizeof(struct location));
    t->count++;
    l->count = 1;
    l->addr = track->addr;
    l->sum_time = age;
    l->min_time = age;
    l->max_time = age;
    l->min_pid = track->pid;
    l->max_pid = track->pid;
    cpumask_clear(to_cpumask(l->cpus));
    cpumask_set_cpu(track->cpu, to_cpumask(l->cpus));
    nodes_clear(l->nodes);
    node_set(page_to_nid(virt_to_page(track)), l->nodes);
    return 1;
}

static void process_slab(struct loc_track *t, struct kmem_cache *s,
        struct page *page, enum track_item alloc,
        unsigned long *map)
{
    void *addr = page_address(page);
    void *p;

    bitmap_zero(map, page->objects);
    get_map(s, page, map);

    for_each_object(p, s, addr, page->objects)
        if (!test_bit(slab_index(p, s, addr), map))
            add_location(t, s, get_track(s, p, alloc));
}

static int list_locations(struct kmem_cache *s, char *buf,
                    enum track_item alloc)
{
    int len = 0;
    unsigned long i;
    struct loc_track t = { 0, 0, NULL };
    int node;
    unsigned long *map = kmalloc(BITS_TO_LONGS(oo_objects(s->max)) *
                     sizeof(unsigned long), GFP_KERNEL);

    if (!map || !alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location),
                     GFP_TEMPORARY)) {
        kfree(map);
        return sprintf(buf, "Out of memory\n");
    }
    /* Push back cpu slabs */
    flush_all(s);

    for_each_node_state(node, N_NORMAL_MEMORY) {
        struct kmem_cache_node *n = get_node(s, node);
        unsigned long flags;
        struct page *page;

        if (!atomic_long_read(&n->nr_slabs))
            continue;

        spin_lock_irqsave(&n->list_lock, flags);
        list_for_each_entry(page, &n->partial, lru)
            process_slab(&t, s, page, alloc, map);
        list_for_each_entry(page, &n->full, lru)
            process_slab(&t, s, page, alloc, map);
        spin_unlock_irqrestore(&n->list_lock, flags);
    }

    for (i = 0; i < t.count; i++) {
        struct location *l = &t.loc[i];

        if (len > PAGE_SIZE - KSYM_SYMBOL_LEN - 100)
            break;
        len += sprintf(buf + len, "%7ld ", l->count);

        if (l->addr)
            len += sprintf(buf + len, "%pS", (void *)l->addr);
        else
            len += sprintf(buf + len, "<not-available>");

        if (l->sum_time != l->min_time) {
            len += sprintf(buf + len, " age=%ld/%ld/%ld",
                l->min_time,
                (long)div_u64(l->sum_time, l->count),
                l->max_time);
        } else
            len += sprintf(buf + len, " age=%ld",
                l->min_time);

        if (l->min_pid != l->max_pid)
            len += sprintf(buf + len, " pid=%ld-%ld",
                l->min_pid, l->max_pid);
        else
            len += sprintf(buf + len, " pid=%ld",
                l->min_pid);

        if (num_online_cpus() > 1 &&
                !cpumask_empty(to_cpumask(l->cpus)) &&
                len < PAGE_SIZE - 60) {
            len += sprintf(buf + len, " cpus=");
            len += cpulist_scnprintf(buf + len, PAGE_SIZE - len - 50,
                         to_cpumask(l->cpus));
        }

        if (nr_online_nodes > 1 && !nodes_empty(l->nodes) &&
                len < PAGE_SIZE - 60) {
            len += sprintf(buf + len, " nodes=");
            len += nodelist_scnprintf(buf + len, PAGE_SIZE - len - 50,
                    l->nodes);
        }

        len += sprintf(buf + len, "\n");
    }

    free_loc_track(&t);
    kfree(map);
    if (!t.count)
        len += sprintf(buf, "No data\n");
    return len;
}
#endif

#ifdef SLUB_RESILIENCY_TEST
static void resiliency_test(void)
{
    u8 *p;

    BUILD_BUG_ON(KMALLOC_MIN_SIZE > 16 || SLUB_PAGE_SHIFT < 10);

    printk(KERN_ERR "SLUB resiliency testing\n");
    printk(KERN_ERR "-----------------------\n");
    printk(KERN_ERR "A. Corruption after allocation\n");

    p = kzalloc(16, GFP_KERNEL);
    p[16] = 0x12;
    printk(KERN_ERR "\n1. kmalloc-16: Clobber Redzone/next pointer"
            " 0x12->0x%p\n\n", p + 16);

    validate_slab_cache(kmalloc_caches[4]);

    /* Hmmm... The next two are dangerous */
    p = kzalloc(32, GFP_KERNEL);
    p[32 + sizeof(void *)] = 0x34;
    printk(KERN_ERR "\n2. kmalloc-32: Clobber next pointer/next slab"
            " 0x34 -> -0x%p\n", p);
    printk(KERN_ERR
        "If allocated object is overwritten then not detectable\n\n");

    validate_slab_cache(kmalloc_caches[5]);
    p = kzalloc(64, GFP_KERNEL);
    p += 64 + (get_cycles() & 0xff) * sizeof(void *);
    *p = 0x56;
    printk(KERN_ERR "\n3. kmalloc-64: corrupting random byte 0x56->0x%p\n",
                                    p);
    printk(KERN_ERR
        "If allocated object is overwritten then not detectable\n\n");
    validate_slab_cache(kmalloc_caches[6]);

    printk(KERN_ERR "\nB. Corruption after free\n");
    p = kzalloc(128, GFP_KERNEL);
    kfree(p);
    *p = 0x78;
    printk(KERN_ERR "1. kmalloc-128: Clobber first word 0x78->0x%p\n\n", p);
    validate_slab_cache(kmalloc_caches[7]);

    p = kzalloc(256, GFP_KERNEL);
    kfree(p);
    p[50] = 0x9a;
    printk(KERN_ERR "\n2. kmalloc-256: Clobber 50th byte 0x9a->0x%p\n\n",
            p);
    validate_slab_cache(kmalloc_caches[8]);

    p = kzalloc(512, GFP_KERNEL);
    kfree(p);
    p[512] = 0xab;
    printk(KERN_ERR "\n3. kmalloc-512: Clobber redzone 0xab->0x%p\n\n", p);
    validate_slab_cache(kmalloc_caches[9]);
}
#else
#ifdef CONFIG_SYSFS
static void resiliency_test(void) {};
#endif
#endif

#ifdef CONFIG_SYSFS
enum slab_stat_type {
    SL_ALL,         /* All slabs */
    SL_PARTIAL,     /* Only partially allocated slabs */
    SL_CPU,         /* Only slabs used for cpu caches */
    SL_OBJECTS,     /* Determine allocated objects not slabs */
    SL_TOTAL        /* Determine object capacity not slabs */
};

#define SO_ALL      (1 << SL_ALL)
#define SO_PARTIAL  (1 << SL_PARTIAL)
#define SO_CPU      (1 << SL_CPU)
#define SO_OBJECTS  (1 << SL_OBJECTS)
#define SO_TOTAL    (1 << SL_TOTAL)

static ssize_t show_slab_objects(struct kmem_cache *s,
                char *buf, unsigned long flags)
{
    unsigned long total = 0;
    int node;
    int x;
    unsigned long *nodes;
    unsigned long *per_cpu;

    nodes = kzalloc(2 * sizeof(unsigned long) * nr_node_ids, GFP_KERNEL);
    if (!nodes)
        return -ENOMEM;
    per_cpu = nodes + nr_node_ids;

    if (flags & SO_CPU) {
        int cpu;

        for_each_possible_cpu(cpu) {
            struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
            int node;
            struct page *page;

            page = ACCESS_ONCE(c->page);
            if (!page)
                continue;

            node = page_to_nid(page);
            if (flags & SO_TOTAL)
                x = page->objects;
            else if (flags & SO_OBJECTS)
                x = page->inuse;
            else
                x = 1;

            total += x;
            nodes[node] += x;

            page = ACCESS_ONCE(c->partial);
            if (page) {
                x = page->pobjects;
                total += x;
                nodes[node] += x;
            }

            per_cpu[node]++;
        }
    }

    lock_memory_hotplug();
#ifdef CONFIG_SLUB_DEBUG
    if (flags & SO_ALL) {
        for_each_node_state(node, N_NORMAL_MEMORY) {
            struct kmem_cache_node *n = get_node(s, node);

        if (flags & SO_TOTAL)
            x = atomic_long_read(&n->total_objects);
        else if (flags & SO_OBJECTS)
            x = atomic_long_read(&n->total_objects) -
                count_partial(n, count_free);

            else
                x = atomic_long_read(&n->nr_slabs);
            total += x;
            nodes[node] += x;
        }

    } else
#endif
    if (flags & SO_PARTIAL) {
        for_each_node_state(node, N_NORMAL_MEMORY) {
            struct kmem_cache_node *n = get_node(s, node);

            if (flags & SO_TOTAL)
                x = count_partial(n, count_total);
            else if (flags & SO_OBJECTS)
                x = count_partial(n, count_inuse);
            else
                x = n->nr_partial;
            total += x;
            nodes[node] += x;
        }
    }
    x = sprintf(buf, "%lu", total);
#ifdef CONFIG_NUMA
    for_each_node_state(node, N_NORMAL_MEMORY)
        if (nodes[node])
            x += sprintf(buf + x, " N%d=%lu",
                    node, nodes[node]);
#endif
    unlock_memory_hotplug();
    kfree(nodes);
    return x + sprintf(buf + x, "\n");
}

#ifdef CONFIG_SLUB_DEBUG
static int any_slab_objects(struct kmem_cache *s)
{
    int node;

    for_each_online_node(node) {
        struct kmem_cache_node *n = get_node(s, node);

        if (!n)
            continue;

        if (atomic_long_read(&n->total_objects))
            return 1;
    }
    return 0;
}
#endif

#define to_slab_attr(n) container_of(n, struct slab_attribute, attr)
#define to_slab(n) container_of(n, struct kmem_cache, kobj)

struct slab_attribute {
    struct attribute attr;
    ssize_t (*show)(struct kmem_cache *s, char *buf);
    ssize_t (*store)(struct kmem_cache *s, const char *x, size_t count);
};

#define SLAB_ATTR_RO(_name) \
    static struct slab_attribute _name##_attr = \
    __ATTR(_name, 0400, _name##_show, NULL)

#define SLAB_ATTR(_name) \
    static struct slab_attribute _name##_attr =  \
    __ATTR(_name, 0600, _name##_show, _name##_store)

static ssize_t slab_size_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", s->size);
}
SLAB_ATTR_RO(slab_size);

static ssize_t align_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", s->align);
}
SLAB_ATTR_RO(align);

static ssize_t object_size_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", s->object_size);
}
SLAB_ATTR_RO(object_size);

static ssize_t objs_per_slab_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", oo_objects(s->oo));
}
SLAB_ATTR_RO(objs_per_slab);

static ssize_t order_store(struct kmem_cache *s,
                const char *buf, size_t length)
{
    unsigned long order;
    int err;

    err = strict_strtoul(buf, 10, &order);
    if (err)
        return err;

    if (order > slub_max_order || order < slub_min_order)
        return -EINVAL;

    calculate_sizes(s, order);
    return length;
}

static ssize_t order_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", oo_order(s->oo));
}
SLAB_ATTR(order);

static ssize_t min_partial_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%lu\n", s->min_partial);
}

static ssize_t min_partial_store(struct kmem_cache *s, const char *buf,
                 size_t length)
{
    unsigned long min;
    int err;

    err = strict_strtoul(buf, 10, &min);
    if (err)
        return err;

    set_min_partial(s, min);
    return length;
}
SLAB_ATTR(min_partial);

static ssize_t cpu_partial_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%u\n", s->cpu_partial);
}

static ssize_t cpu_partial_store(struct kmem_cache *s, const char *buf,
                 size_t length)
{
    unsigned long objects;
    int err;

    err = strict_strtoul(buf, 10, &objects);
    if (err)
        return err;
    if (objects && kmem_cache_debug(s))
        return -EINVAL;

    s->cpu_partial = objects;
    flush_all(s);
    return length;
}
SLAB_ATTR(cpu_partial);

static ssize_t ctor_show(struct kmem_cache *s, char *buf)
{
    if (!s->ctor)
        return 0;
    return sprintf(buf, "%pS\n", s->ctor);
}
SLAB_ATTR_RO(ctor);

static ssize_t aliases_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", s->refcount - 1);
}
SLAB_ATTR_RO(aliases);

static ssize_t partial_show(struct kmem_cache *s, char *buf)
{
    return show_slab_objects(s, buf, SO_PARTIAL);
}
SLAB_ATTR_RO(partial);

static ssize_t cpu_slabs_show(struct kmem_cache *s, char *buf)
{
    return show_slab_objects(s, buf, SO_CPU);
}
SLAB_ATTR_RO(cpu_slabs);

static ssize_t objects_show(struct kmem_cache *s, char *buf)
{
    return show_slab_objects(s, buf, SO_ALL|SO_OBJECTS);
}
SLAB_ATTR_RO(objects);

static ssize_t objects_partial_show(struct kmem_cache *s, char *buf)
{
    return show_slab_objects(s, buf, SO_PARTIAL|SO_OBJECTS);
}
SLAB_ATTR_RO(objects_partial);

static ssize_t slabs_cpu_partial_show(struct kmem_cache *s, char *buf)
{
    int objects = 0;
    int pages = 0;
    int cpu;
    int len;

    for_each_online_cpu(cpu) {
        struct page *page = per_cpu_ptr(s->cpu_slab, cpu)->partial;

        if (page) {
            pages += page->pages;
            objects += page->pobjects;
        }
    }

    len = sprintf(buf, "%d(%d)", objects, pages);

#ifdef CONFIG_SMP
    for_each_online_cpu(cpu) {
        struct page *page = per_cpu_ptr(s->cpu_slab, cpu) ->partial;

        if (page && len < PAGE_SIZE - 20)
            len += sprintf(buf + len, " C%d=%d(%d)", cpu,
                page->pobjects, page->pages);
    }
#endif
    return len + sprintf(buf + len, "\n");
}
SLAB_ATTR_RO(slabs_cpu_partial);

static ssize_t reclaim_account_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_RECLAIM_ACCOUNT));
}

static ssize_t reclaim_account_store(struct kmem_cache *s,
                const char *buf, size_t length)
{
    s->flags &= ~SLAB_RECLAIM_ACCOUNT;
    if (buf[0] == '1')
        s->flags |= SLAB_RECLAIM_ACCOUNT;
    return length;
}
SLAB_ATTR(reclaim_account);

static ssize_t hwcache_align_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_HWCACHE_ALIGN));
}
SLAB_ATTR_RO(hwcache_align);

#ifdef CONFIG_ZONE_DMA
static ssize_t cache_dma_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_CACHE_DMA));
}
SLAB_ATTR_RO(cache_dma);
#endif

static ssize_t destroy_by_rcu_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_DESTROY_BY_RCU));
}
SLAB_ATTR_RO(destroy_by_rcu);

static ssize_t reserved_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", s->reserved);
}
SLAB_ATTR_RO(reserved);

#ifdef CONFIG_SLUB_DEBUG
static ssize_t slabs_show(struct kmem_cache *s, char *buf)
{
    return show_slab_objects(s, buf, SO_ALL);
}
SLAB_ATTR_RO(slabs);

static ssize_t total_objects_show(struct kmem_cache *s, char *buf)
{
    return show_slab_objects(s, buf, SO_ALL|SO_TOTAL);
}
SLAB_ATTR_RO(total_objects);

static ssize_t sanity_checks_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_DEBUG_FREE));
}

static ssize_t sanity_checks_store(struct kmem_cache *s,
                const char *buf, size_t length)
{
    s->flags &= ~SLAB_DEBUG_FREE;
    if (buf[0] == '1') {
        s->flags &= ~__CMPXCHG_DOUBLE;
        s->flags |= SLAB_DEBUG_FREE;
    }
    return length;
}
SLAB_ATTR(sanity_checks);

static ssize_t trace_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_TRACE));
}

static ssize_t trace_store(struct kmem_cache *s, const char *buf,
                            size_t length)
{
    s->flags &= ~SLAB_TRACE;
    if (buf[0] == '1') {
        s->flags &= ~__CMPXCHG_DOUBLE;
        s->flags |= SLAB_TRACE;
    }
    return length;
}
SLAB_ATTR(trace);

static ssize_t red_zone_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_RED_ZONE));
}

static ssize_t red_zone_store(struct kmem_cache *s,
                const char *buf, size_t length)
{
    if (any_slab_objects(s))
        return -EBUSY;

    s->flags &= ~SLAB_RED_ZONE;
    if (buf[0] == '1') {
        s->flags &= ~__CMPXCHG_DOUBLE;
        s->flags |= SLAB_RED_ZONE;
    }
    calculate_sizes(s, -1);
    return length;
}
SLAB_ATTR(red_zone);

static ssize_t poison_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_POISON));
}

static ssize_t poison_store(struct kmem_cache *s,
                const char *buf, size_t length)
{
    if (any_slab_objects(s))
        return -EBUSY;

    s->flags &= ~SLAB_POISON;
    if (buf[0] == '1') {
        s->flags &= ~__CMPXCHG_DOUBLE;
        s->flags |= SLAB_POISON;
    }
    calculate_sizes(s, -1);
    return length;
}
SLAB_ATTR(poison);

static ssize_t store_user_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_STORE_USER));
}

static ssize_t store_user_store(struct kmem_cache *s,
                const char *buf, size_t length)
{
    if (any_slab_objects(s))
        return -EBUSY;

    s->flags &= ~SLAB_STORE_USER;
    if (buf[0] == '1') {
        s->flags &= ~__CMPXCHG_DOUBLE;
        s->flags |= SLAB_STORE_USER;
    }
    calculate_sizes(s, -1);
    return length;
}
SLAB_ATTR(store_user);

static ssize_t validate_show(struct kmem_cache *s, char *buf)
{
    return 0;
}

static ssize_t validate_store(struct kmem_cache *s,
            const char *buf, size_t length)
{
    int ret = -EINVAL;

    if (buf[0] == '1') {
        ret = validate_slab_cache(s);
        if (ret >= 0)
            ret = length;
    }
    return ret;
}
SLAB_ATTR(validate);

static ssize_t alloc_calls_show(struct kmem_cache *s, char *buf)
{
    if (!(s->flags & SLAB_STORE_USER))
        return -ENOSYS;
    return list_locations(s, buf, TRACK_ALLOC);
}
SLAB_ATTR_RO(alloc_calls);

static ssize_t free_calls_show(struct kmem_cache *s, char *buf)
{
    if (!(s->flags & SLAB_STORE_USER))
        return -ENOSYS;
    return list_locations(s, buf, TRACK_FREE);
}
SLAB_ATTR_RO(free_calls);
#endif /* CONFIG_SLUB_DEBUG */

#ifdef CONFIG_FAILSLAB
static ssize_t failslab_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", !!(s->flags & SLAB_FAILSLAB));
}

static ssize_t failslab_store(struct kmem_cache *s, const char *buf,
                            size_t length)
{
    s->flags &= ~SLAB_FAILSLAB;
    if (buf[0] == '1')
        s->flags |= SLAB_FAILSLAB;
    return length;
}
SLAB_ATTR(failslab);
#endif

static ssize_t shrink_show(struct kmem_cache *s, char *buf)
{
    return 0;
}

static ssize_t shrink_store(struct kmem_cache *s,
            const char *buf, size_t length)
{
    if (buf[0] == '1') {
        int rc = kmem_cache_shrink(s);

        if (rc)
            return rc;
    } else
        return -EINVAL;
    return length;
}
SLAB_ATTR(shrink);

#ifdef CONFIG_NUMA
static ssize_t remote_node_defrag_ratio_show(struct kmem_cache *s, char *buf)
{
    return sprintf(buf, "%d\n", s->remote_node_defrag_ratio / 10);
}

static ssize_t remote_node_defrag_ratio_store(struct kmem_cache *s,
                const char *buf, size_t length)
{
    unsigned long ratio;
    int err;

    err = strict_strtoul(buf, 10, &ratio);
    if (err)
        return err;

    if (ratio <= 100)
        s->remote_node_defrag_ratio = ratio * 10;

    return length;
}
SLAB_ATTR(remote_node_defrag_ratio);
#endif

#ifdef CONFIG_SLUB_STATS
static int show_stat(struct kmem_cache *s, char *buf, enum stat_item si)
{
    unsigned long sum  = 0;
    int cpu;
    int len;
    int *data = kmalloc(nr_cpu_ids * sizeof(int), GFP_KERNEL);

    if (!data)
        return -ENOMEM;

    for_each_online_cpu(cpu) {
        unsigned x = per_cpu_ptr(s->cpu_slab, cpu)->stat[si];

        data[cpu] = x;
        sum += x;
    }

    len = sprintf(buf, "%lu", sum);

#ifdef CONFIG_SMP
    for_each_online_cpu(cpu) {
        if (data[cpu] && len < PAGE_SIZE - 20)
            len += sprintf(buf + len, " C%d=%u", cpu, data[cpu]);
    }
#endif
    kfree(data);
    return len + sprintf(buf + len, "\n");
}

static void clear_stat(struct kmem_cache *s, enum stat_item si)
{
    int cpu;

    for_each_online_cpu(cpu)
        per_cpu_ptr(s->cpu_slab, cpu)->stat[si] = 0;
}

#define STAT_ATTR(si, text)                     \
static ssize_t text##_show(struct kmem_cache *s, char *buf) \
{                               \
    return show_stat(s, buf, si);               \
}                               \
static ssize_t text##_store(struct kmem_cache *s,       \
                const char *buf, size_t length) \
{                               \
    if (buf[0] != '0')                  \
        return -EINVAL;                 \
    clear_stat(s, si);                  \
    return length;                      \
}                               \
SLAB_ATTR(text);                        \

STAT_ATTR(ALLOC_FASTPATH, alloc_fastpath);
STAT_ATTR(ALLOC_SLOWPATH, alloc_slowpath);
STAT_ATTR(FREE_FASTPATH, free_fastpath);
STAT_ATTR(FREE_SLOWPATH, free_slowpath);
STAT_ATTR(FREE_FROZEN, free_frozen);
STAT_ATTR(FREE_ADD_PARTIAL, free_add_partial);
STAT_ATTR(FREE_REMOVE_PARTIAL, free_remove_partial);
STAT_ATTR(ALLOC_FROM_PARTIAL, alloc_from_partial);
STAT_ATTR(ALLOC_SLAB, alloc_slab);
STAT_ATTR(ALLOC_REFILL, alloc_refill);
STAT_ATTR(ALLOC_NODE_MISMATCH, alloc_node_mismatch);
STAT_ATTR(FREE_SLAB, free_slab);
STAT_ATTR(CPUSLAB_FLUSH, cpuslab_flush);
STAT_ATTR(DEACTIVATE_FULL, deactivate_full);
STAT_ATTR(DEACTIVATE_EMPTY, deactivate_empty);
STAT_ATTR(DEACTIVATE_TO_HEAD, deactivate_to_head);
STAT_ATTR(DEACTIVATE_TO_TAIL, deactivate_to_tail);
STAT_ATTR(DEACTIVATE_REMOTE_FREES, deactivate_remote_frees);
STAT_ATTR(DEACTIVATE_BYPASS, deactivate_bypass);
STAT_ATTR(ORDER_FALLBACK, order_fallback);
STAT_ATTR(CMPXCHG_DOUBLE_CPU_FAIL, cmpxchg_double_cpu_fail);
STAT_ATTR(CMPXCHG_DOUBLE_FAIL, cmpxchg_double_fail);
STAT_ATTR(CPU_PARTIAL_ALLOC, cpu_partial_alloc);
STAT_ATTR(CPU_PARTIAL_FREE, cpu_partial_free);
STAT_ATTR(CPU_PARTIAL_NODE, cpu_partial_node);
STAT_ATTR(CPU_PARTIAL_DRAIN, cpu_partial_drain);
#endif

static struct attribute *slab_attrs[] = {
    &slab_size_attr.attr,
    &object_size_attr.attr,
    &objs_per_slab_attr.attr,
    &order_attr.attr,
    &min_partial_attr.attr,
    &cpu_partial_attr.attr,
    &objects_attr.attr,
    &objects_partial_attr.attr,
    &partial_attr.attr,
    &cpu_slabs_attr.attr,
    &ctor_attr.attr,
    &aliases_attr.attr,
    &align_attr.attr,
    &hwcache_align_attr.attr,
    &reclaim_account_attr.attr,
    &destroy_by_rcu_attr.attr,
    &shrink_attr.attr,
    &reserved_attr.attr,
    &slabs_cpu_partial_attr.attr,
#ifdef CONFIG_SLUB_DEBUG
    &total_objects_attr.attr,
    &slabs_attr.attr,
    &sanity_checks_attr.attr,
    &trace_attr.attr,
    &red_zone_attr.attr,
    &poison_attr.attr,
    &store_user_attr.attr,
    &validate_attr.attr,
    &alloc_calls_attr.attr,
    &free_calls_attr.attr,
#endif
#ifdef CONFIG_ZONE_DMA
    &cache_dma_attr.attr,
#endif
#ifdef CONFIG_NUMA
    &remote_node_defrag_ratio_attr.attr,
#endif
#ifdef CONFIG_SLUB_STATS
    &alloc_fastpath_attr.attr,
    &alloc_slowpath_attr.attr,
    &free_fastpath_attr.attr,
    &free_slowpath_attr.attr,
    &free_frozen_attr.attr,
    &free_add_partial_attr.attr,
    &free_remove_partial_attr.attr,
    &alloc_from_partial_attr.attr,
    &alloc_slab_attr.attr,
    &alloc_refill_attr.attr,
    &alloc_node_mismatch_attr.attr,
    &free_slab_attr.attr,
    &cpuslab_flush_attr.attr,
    &deactivate_full_attr.attr,
    &deactivate_empty_attr.attr,
    &deactivate_to_head_attr.attr,
    &deactivate_to_tail_attr.attr,
    &deactivate_remote_frees_attr.attr,
    &deactivate_bypass_attr.attr,
    &order_fallback_attr.attr,
    &cmpxchg_double_fail_attr.attr,
    &cmpxchg_double_cpu_fail_attr.attr,
    &cpu_partial_alloc_attr.attr,
    &cpu_partial_free_attr.attr,
    &cpu_partial_node_attr.attr,
    &cpu_partial_drain_attr.attr,
#endif
#ifdef CONFIG_FAILSLAB
    &failslab_attr.attr,
#endif

    NULL
};

static struct attribute_group slab_attr_group = {
    .attrs = slab_attrs,
};

static ssize_t slab_attr_show(struct kobject *kobj,
                struct attribute *attr,
                char *buf)
{
    struct slab_attribute *attribute;
    struct kmem_cache *s;
    int err;

    attribute = to_slab_attr(attr);
    s = to_slab(kobj);

    if (!attribute->show)
        return -EIO;

    err = attribute->show(s, buf);

    return err;
}

static ssize_t slab_attr_store(struct kobject *kobj,
                struct attribute *attr,
                const char *buf, size_t len)
{
    struct slab_attribute *attribute;
    struct kmem_cache *s;
    int err;

    attribute = to_slab_attr(attr);
    s = to_slab(kobj);

    if (!attribute->store)
        return -EIO;

    err = attribute->store(s, buf, len);

    return err;
}

static const struct sysfs_ops slab_sysfs_ops = {
    .show = slab_attr_show,
    .store = slab_attr_store,
};

static struct kobj_type slab_ktype = {
    .sysfs_ops = &slab_sysfs_ops,
};

static int uevent_filter(struct kset *kset, struct kobject *kobj)
{
    struct kobj_type *ktype = get_ktype(kobj);

    if (ktype == &slab_ktype)
        return 1;
    return 0;
}

static const struct kset_uevent_ops slab_uevent_ops = {
    .filter = uevent_filter,
};

static struct kset *slab_kset;

#define ID_STR_LENGTH 64

/* Create a unique string id for a slab cache:
 *
 * Format   :[flags-]size
 */
static char *create_unique_id(struct kmem_cache *s)
{
    char *name = kmalloc(ID_STR_LENGTH, GFP_KERNEL);
    char *p = name;

    BUG_ON(!name);

    *p++ = ':';
    /*
     * First flags affecting slabcache operations. We will only
     * get here for aliasable slabs so we do not need to support
     * too many flags. The flags here must cover all flags that
     * are matched during merging to guarantee that the id is
     * unique.
     */
    if (s->flags & SLAB_CACHE_DMA)
        *p++ = 'd';
    if (s->flags & SLAB_RECLAIM_ACCOUNT)
        *p++ = 'a';
    if (s->flags & SLAB_DEBUG_FREE)
        *p++ = 'F';
    if (!(s->flags & SLAB_NOTRACK))
        *p++ = 't';
    if (p != name + 1)
        *p++ = '-';
    p += sprintf(p, "%07d", s->size);
    BUG_ON(p > name + ID_STR_LENGTH - 1);
    return name;
}

static int sysfs_slab_add(struct kmem_cache *s)
{
    int err;
    const char *name;
    int unmergeable;

    if (slab_state < FULL)
        /* Defer until later */
        return 0;

    unmergeable = slab_unmergeable(s);
    if (unmergeable) {
        /*
         * Slabcache can never be merged so we can use the name proper.
         * This is typically the case for debug situations. In that
         * case we can catch duplicate names easily.
         */
        sysfs_remove_link(&slab_kset->kobj, s->name);
        name = s->name;
    } else {
        /*
         * Create a unique name for the slab as a target
         * for the symlinks.
         */
        name = create_unique_id(s);
    }

    s->kobj.kset = slab_kset;
    err = kobject_init_and_add(&s->kobj, &slab_ktype, NULL, name);
    if (err) {
        kobject_put(&s->kobj);
        return err;
    }

    err = sysfs_create_group(&s->kobj, &slab_attr_group);
    if (err) {
        kobject_del(&s->kobj);
        kobject_put(&s->kobj);
        return err;
    }
    kobject_uevent(&s->kobj, KOBJ_ADD);
    if (!unmergeable) {
        /* Setup first alias */
        sysfs_slab_alias(s, s->name);
        kfree(name);
    }
    return 0;
}

static void sysfs_slab_remove(struct kmem_cache *s)
{
    if (slab_state < FULL)
        /*
         * Sysfs has not been setup yet so no need to remove the
         * cache from sysfs.
         */
        return;

    kobject_uevent(&s->kobj, KOBJ_REMOVE);
    kobject_del(&s->kobj);
    kobject_put(&s->kobj);
}

/*
 * Need to buffer aliases during bootup until sysfs becomes
 * available lest we lose that information.
 */
struct saved_alias {
    struct kmem_cache *s;
    const char *name;
    struct saved_alias *next;
};

static struct saved_alias *alias_list;

static int sysfs_slab_alias(struct kmem_cache *s, const char *name)
{
    struct saved_alias *al;

    if (slab_state == FULL) {
        /*
         * If we have a leftover link then remove it.
         */
        sysfs_remove_link(&slab_kset->kobj, name);
        return sysfs_create_link(&slab_kset->kobj, &s->kobj, name);
    }

    al = kmalloc(sizeof(struct saved_alias), GFP_KERNEL);
    if (!al)
        return -ENOMEM;

    al->s = s;
    al->name = name;
    al->next = alias_list;
    alias_list = al;
    return 0;
}

static int __init slab_sysfs_init(void)
{
    struct kmem_cache *s;
    int err;

    mutex_lock(&slab_mutex);

    slab_kset = kset_create_and_add("slab", &slab_uevent_ops, kernel_kobj);
    if (!slab_kset) {
        mutex_unlock(&slab_mutex);
        printk(KERN_ERR "Cannot register slab subsystem.\n");
        return -ENOSYS;
    }

    slab_state = FULL;

    list_for_each_entry(s, &slab_caches, list) {
        err = sysfs_slab_add(s);
        if (err)
            printk(KERN_ERR "SLUB: Unable to add boot slab %s"
                        " to sysfs\n", s->name);
    }

    while (alias_list) {
        struct saved_alias *al = alias_list;

        alias_list = alias_list->next;
        err = sysfs_slab_alias(al->s, al->name);
        if (err)
            printk(KERN_ERR "SLUB: Unable to add boot slab alias"
                    " %s to sysfs\n", al->name);
        kfree(al);
    }

    mutex_unlock(&slab_mutex);
    resiliency_test();
    return 0;
}

__initcall(slab_sysfs_init);
#endif /* CONFIG_SYSFS */

/*
 * The /proc/slabinfo ABI
 */
#ifdef CONFIG_SLABINFO
static void print_slabinfo_header(struct seq_file *m)
{
    seq_puts(m, "slabinfo - version: 2.1\n");
    seq_puts(m, "# name            <active_objs> <num_objs> <object_size> "
         "<objperslab> <pagesperslab>");
    seq_puts(m, " : tunables <limit> <batchcount> <sharedfactor>");
    seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail>");
    seq_putc(m, '\n');
}

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

    mutex_lock(&slab_mutex);
    if (!n)
        print_slabinfo_header(m);

    return seq_list_start(&slab_caches, *pos);
}

static void *s_next(struct seq_file *m, void *p, loff_t *pos)
{
    return seq_list_next(p, &slab_caches, pos);
}

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

static int s_show(struct seq_file *m, void *p)
{
    unsigned long nr_partials = 0;
    unsigned long nr_slabs = 0;
    unsigned long nr_inuse = 0;
    unsigned long nr_objs = 0;
    unsigned long nr_free = 0;
    struct kmem_cache *s;
    int node;

    s = list_entry(p, struct kmem_cache, list);

    for_each_online_node(node) {
        struct kmem_cache_node *n = get_node(s, node);

        if (!n)
            continue;

        nr_partials += n->nr_partial;
        nr_slabs += atomic_long_read(&n->nr_slabs);
        nr_objs += atomic_long_read(&n->total_objects);
        nr_free += count_partial(n, count_free);
    }

    nr_inuse = nr_objs - nr_free;

    seq_printf(m, "%-17s %6lu %6lu %6u %4u %4d", s->name, nr_inuse,
           nr_objs, s->size, oo_objects(s->oo),
           (1 << oo_order(s->oo)));
    seq_printf(m, " : tunables %4u %4u %4u", 0, 0, 0);
    seq_printf(m, " : slabdata %6lu %6lu %6lu", nr_slabs, nr_slabs,
           0UL);
    seq_putc(m, '\n');
    return 0;
}

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

static int slabinfo_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &slabinfo_op);
}

static const struct file_operations proc_slabinfo_operations = {
    .open       = slabinfo_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};

static int __init slab_proc_init(void)
{
    proc_create("slabinfo", S_IRUSR, NULL, &proc_slabinfo_operations);
    return 0;
}
module_init(slab_proc_init);
#endif /* CONFIG_SLABINFO */