/*
 * 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 and only
 * uses a centralized lock to manage a pool of partial slabs.
 *
 * (C) 2007 SGI, Christoph Lameter
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/bit_spinlock.h>
#include <linux/interrupt.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/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>

/*
 * Lock order:
 *   1. slab_lock(page)
 *   2. slab->list_lock
 *
 *   The slab_lock protects operations on the object of a particular
 *   slab and its metadata in the page struct. If the slab lock
 *   has been taken then no allocations nor frees can be performed
 *   on the objects in the slab nor can the slab be added or removed
 *   from the partial or full lists since this would mean modifying
 *   the page_struct of the slab.
 *
 *   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.
 *
 *   The lock order is sometimes inverted when we are trying to get a slab
 *   off a list. We take the list_lock and then look for a page on the list
 *   to use. While we do that objects in the slabs may be freed. We can
 *   only operate on the slab if we have also taken the slab_lock. So we use
 *   a slab_trylock() on the slab. If trylock was successful then no frees
 *   can occur anymore and we can use the slab for allocations etc. If the
 *   slab_trylock() does not succeed then frees are in progress in the slab and
 *   we must stay away from it for a while since we may cause a bouncing
 *   cacheline if we try to acquire the lock. So go onto the next slab.
 *   If all pages are busy then we may allocate a new slab instead of reusing
 *   a partial slab. A new slab has noone operating on it and thus there is
 *   no danger of cacheline contention.
 *
 *   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.
 */

#ifdef CONFIG_SLUB_DEBUG
#define SLABDEBUG 1
#else
#define SLABDEBUG 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

/*
 * 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)

/*
 * 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)

#define SLUB_MERGE_SAME (SLAB_DEBUG_FREE | SLAB_RECLAIM_ACCOUNT | \
                SLAB_CACHE_DMA)

#ifndef ARCH_KMALLOC_MINALIGN
#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
#endif

#ifndef ARCH_SLAB_MINALIGN
#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
#endif

/* Internal SLUB flags */
#define __OBJECT_POISON         0x80000000 /* Poison object */
#define __SYSFS_ADD_DEFERRED    0x40000000 /* Not yet visible via sysfs */

static int kmem_size = sizeof(struct kmem_cache);

#ifdef CONFIG_SMP
static struct notifier_block slab_notifier;
#endif

static enum {
        DOWN,           /* No slab functionality available */
        PARTIAL,        /* kmem_cache_open() works but kmalloc does not */
        UP,             /* Everything works but does not show up in sysfs */
        SYSFS           /* Sysfs up */
} slab_state = DOWN;

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

/*
 * Tracking user of a slab.
 */
struct track {
        void *addr;             /* Called from address */
        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_SLUB_DEBUG
static int sysfs_slab_add(struct kmem_cache *);
static int sysfs_slab_alias(struct kmem_cache *, const char *);
static void sysfs_slab_remove(struct kmem_cache *);

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

#endif

static inline void stat(struct kmem_cache_cpu *c, enum stat_item si)
{
#ifdef CONFIG_SLUB_STATS
        c->stat[si]++;
#endif
}

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

int slab_is_available(void)
{
        return slab_state >= UP;
}

static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node)
{
#ifdef CONFIG_NUMA
        return s->node[node];
#else
        return &s->local_node;
#endif
}

static inline struct kmem_cache_cpu *get_cpu_slab(struct kmem_cache *s, int cpu)
{
#ifdef CONFIG_SMP
        return s->cpu_slab[cpu];
#else
        return &s->cpu_slab;
#endif
}

/* 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;
}

/*
 * Slow version of get and set free pointer.
 *
 * This version requires touching the cache lines of kmem_cache which
 * we avoid to do in the fast alloc free paths. There we obtain the offset
 * from the page struct.
 */
static inline void *get_freepointer(struct kmem_cache *s, void *object)
{
        return *(void **)(object + s->offset);
}

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)

/* Scan freelist */
#define for_each_free_object(__p, __s, __free) \
        for (__p = (__free); __p; __p = get_freepointer((__s), __p))

/* 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 struct kmem_cache_order_objects oo_make(int order,
                                                unsigned long size)
{
        struct kmem_cache_order_objects x = {
                (order << 16) + (PAGE_SIZE << order) / size
        };

        return x;
}

static inline int oo_order(struct kmem_cache_order_objects x)
{
        return x.x >> 16;
}

static inline int oo_objects(struct kmem_cache_order_objects x)
{
        return x.x & ((1 << 16) - 1);
}

#ifdef CONFIG_SLUB_DEBUG
/*
 * 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;

/*
 * Object debugging
 */
static void print_section(char *text, u8 *addr, unsigned int length)
{
        int i, offset;
        int newline = 1;
        char ascii[17];

        ascii[16] = 0;

        for (i = 0; i < length; i++) {
                if (newline) {
                        printk(KERN_ERR "%8s 0x%p: ", text, addr + i);
                        newline = 0;
                }
                printk(KERN_CONT " %02x", addr[i]);
                offset = i % 16;
                ascii[offset] = isgraph(addr[i]) ? addr[i] : '.';
                if (offset == 15) {
                        printk(KERN_CONT " %s\n", ascii);
                        newline = 1;
                }
        }
        if (!newline) {
                i %= 16;
                while (i < 16) {
                        printk(KERN_CONT "   ");
                        ascii[i] = ' ';
                        i++;
                }
                printk(KERN_CONT " %s\n", ascii);
        }
}

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, void *addr)
{
        struct track *p;

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

        p += alloc;
        if (addr) {
                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, NULL);
        set_track(s, object, TRACK_ALLOC, NULL);
}

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, t->addr, jiffies - t->when, t->cpu, t->pid);
}

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

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

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

}

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

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

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

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

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

        print_tracking(s, p);

        print_page_info(page);

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

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

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

        if (s->flags & SLAB_RED_ZONE)
                print_section("Redzone", p + s->objsize,
                        s->inuse - s->objsize);

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

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

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

        dump_stack();
}

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

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

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

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

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

        if (s->flags & SLAB_RED_ZONE)
                memset(p + s->objsize,
                        active ? SLUB_RED_ACTIVE : SLUB_RED_INACTIVE,
                        s->inuse - s->objsize);
}

static u8 *check_bytes(u8 *start, unsigned int value, unsigned int bytes)
{
        while (bytes) {
                if (*start != (u8)value)
                        return start;
                start++;
                bytes--;
        }
        return NULL;
}

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

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

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

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

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

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

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

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

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

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

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

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

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

        fault = check_bytes(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, start, end);
        return 0;
}

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

        if (s->flags & SLAB_RED_ZONE) {
                unsigned int red =
                        active ? SLUB_RED_ACTIVE : SLUB_RED_INACTIVE;

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

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

        if (!s->offset && 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 loose 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 = (PAGE_SIZE << compound_order(page)) / s->size;
        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 = page->freelist;
        void *object = NULL;
        unsigned long max_objects;

        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 = (PAGE_SIZE << compound_order(page)) / s->size;
        if (max_objects > 65535)
                max_objects = 65535;

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

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

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

                dump_stack();
        }
}

/*
 * Tracking of fully allocated slabs for debugging purposes.
 */
static void add_full(struct kmem_cache_node *n, struct page *page)
{
        spin_lock(&n->list_lock);
        list_add(&page->lru, &n->full);
        spin_unlock(&n->list_lock);
}

static void remove_full(struct kmem_cache *s, struct page *page)
{
        struct kmem_cache_node *n;

        if (!(s->flags & SLAB_STORE_USER))
                return;

        n = get_node(s, page_to_nid(page));

        spin_lock(&n->list_lock);
        list_del(&page->lru);
        spin_unlock(&n->list_lock);
}

/* 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 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 (!NUMA_BUILD || 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, 0);
        init_tracking(s, object);
}

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

        if (!on_freelist(s, page, object)) {
                object_err(s, page, object, "Object already allocated");
                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, 0))
                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, 1);
        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 int free_debug_processing(struct kmem_cache *s, struct page *page,
                                                void *object, void *addr)
{
        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, 1))
                return 0;

        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;
        }

        /* Special debug activities for freeing objects */
        if (!PageSlubFrozen(page) && !page->freelist)
                remove_full(s, page);
        if (s->flags & SLAB_STORE_USER)
                set_track(s, object, TRACK_FREE, addr);
        trace(s, page, object, 0);
        init_object(s, object, 0);
        return 1;

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

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;

        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;
                default:
                        printk(KERN_ERR "slub_debug option '%c' "

                                "unknown. skipped\n", *str);
                }
        }

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

__setup("slub_debug", setup_slub_debug);

static unsigned long kmem_cache_flags(unsigned long objsize,
        unsigned long flags, const char *name,
        void (*ctor)(void *))
{
        /*
         * Enable debugging if selected on the kernel commandline.
         */
        if (slub_debug && (!slub_debug_slabs ||
            strncmp(slub_debug_slabs, name, strlen(slub_debug_slabs)) == 0))
                        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, void *addr) { return 0; }

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

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

static inline unsigned long slabs_node(struct kmem_cache *s, int node)
                                                        { 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) {}
#endif

/*
 * 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);

        if (node == -1)
                return alloc_pages(flags, order);
        else
                return alloc_pages_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;

        flags |= s->allocflags;

        page = alloc_slab_page(flags | __GFP_NOWARN | __GFP_NORETRY, 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)
                        return NULL;

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

        return page;
}

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

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

        BUG_ON(flags & GFP_SLAB_BUG_MASK);

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

        inc_slabs_node(s, page_to_nid(page), page->objects);
        page->slab = s;
        page->flags |= 1 << PG_slab;
        if (s->flags & (SLAB_DEBUG_FREE | SLAB_RED_ZONE | SLAB_POISON |
                        SLAB_STORE_USER | SLAB_TRACE))
                __SetPageSlubDebug(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 = 0;
out:
        return page;
}

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

        if (unlikely(SLABDEBUG && PageSlubDebug(page))) {
                void *p;

                slab_pad_check(s, page);
                for_each_object(p, s, page_address(page),
                                                page->objects)
                        check_object(s, page, p, 0);
                __ClearPageSlubDebug(page);
        }

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

        __ClearPageSlab(page);
        reset_page_mapcount(page);
        __free_pages(page, order);
}

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

        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)) {
                /*
                 * RCU free overloads the RCU head over the LRU
                 */
                struct rcu_head *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);
}

/*
 * 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);
}

static __always_inline int slab_trylock(struct page *page)
{
        int rc = 1;

        rc = bit_spin_trylock(PG_locked, &page->flags);
        return rc;
}

/*
 * Management of partially allocated slabs
 */
static void add_partial(struct kmem_cache_node *n,
                                struct page *page, int tail)
{
        spin_lock(&n->list_lock);
        n->nr_partial++;
        if (tail)
                list_add_tail(&page->lru, &n->partial);
        else
                list_add(&page->lru, &n->partial);
        spin_unlock(&n->list_lock);
}

static void remove_partial(struct kmem_cache *s, struct page *page)
{
        struct kmem_cache_node *n = get_node(s, page_to_nid(page));

        spin_lock(&n->list_lock);
        list_del(&page->lru);
        n->nr_partial--;
        spin_unlock(&n->list_lock);
}

/*
 * Lock slab and remove from the partial list.
 *
 * Must hold list_lock.
 */
static inline int lock_and_freeze_slab(struct kmem_cache_node *n,
                                                        struct page *page)
{
        if (slab_trylock(page)) {
                list_del(&page->lru);
                n->nr_partial--;
                __SetPageSlubFrozen(page);
                return 1;
        }
        return 0;
}

/*
 * Try to allocate a partial slab from a specific node.
 */
static struct page *get_partial_node(struct kmem_cache_node *n)
{
        struct page *page;

        /*
         * 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(page, &n->partial, lru)
                if (lock_and_freeze_slab(n, page))
                        goto out;
        page = NULL;
out:
        spin_unlock(&n->list_lock);
        return page;
}

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

        /*
         * 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;

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

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

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

/*
 * Get a partial page, lock it and return it.
 */
static struct page *get_partial(struct kmem_cache *s, gfp_t flags, int node)
{
        struct page *page;
        int searchnode = (node == -1) ? numa_node_id() : node;

        page = get_partial_node(get_node(s, searchnode));
        if (page || (flags & __GFP_THISNODE))
                return page;

        return get_any_partial(s, flags);
}

/*
 * Move a page back to the lists.
 *
 * Must be called with the slab lock held.
 *
 * On exit the slab lock will have been dropped.
 */
static void unfreeze_slab(struct kmem_cache *s, struct page *page, int tail)
{
        struct kmem_cache_node *n = get_node(s, page_to_nid(page));
        struct kmem_cache_cpu *c = get_cpu_slab(s, smp_processor_id());

        __ClearPageSlubFrozen(page);
        if (page->inuse) {

                if (page->freelist) {
                        add_partial(n, page, tail);
                        stat(c, tail ? DEACTIVATE_TO_TAIL : DEACTIVATE_TO_HEAD);
                } else {
                        stat(c, DEACTIVATE_FULL);
                        if (SLABDEBUG && PageSlubDebug(page) &&
                                                (s->flags & SLAB_STORE_USER))
                                add_full(n, page);
                }
                slab_unlock(page);
        } else {
                stat(c, DEACTIVATE_EMPTY);
                if (n->nr_partial < n->min_partial) {
                        /*
                         * Adding an empty slab to the partial slabs in order
                         * to avoid page allocator overhead. This slab needs
                         * to come after the other slabs with objects in
                         * so that the others get filled first. That way the
                         * size of the partial list stays small.
                         *
                         * kmem_cache_shrink can reclaim any empty slabs from
                         * the partial list.
                         */
                        add_partial(n, page, 1);
                        slab_unlock(page);
                } else {
                        slab_unlock(page);
                        stat(get_cpu_slab(s, raw_smp_processor_id()), FREE_SLAB);
                        discard_slab(s, page);
                }
        }
}

/*
 * Remove the cpu slab
 */
static void deactivate_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
{
        struct page *page = c->page;
        int tail = 1;

        if (page->freelist)
                stat(c, DEACTIVATE_REMOTE_FREES);
        /*
         * Merge cpu freelist into slab freelist. Typically we get here
         * because both freelists are empty. So this is unlikely
         * to occur.
         */
        while (unlikely(c->freelist)) {
                void **object;

                tail = 0;       /* Hot objects. Put the slab first */

                /* Retrieve object from cpu_freelist */
                object = c->freelist;
                c->freelist = c->freelist[c->offset];

                /* And put onto the regular freelist */
                object[c->offset] = page->freelist;
                page->freelist = object;
                page->inuse--;
        }
        c->page = NULL;
        unfreeze_slab(s, page, tail);
}

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

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

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

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

        __flush_cpu_slab(s, smp_processor_id());
}

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

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

/*
 * Slow path. The lockless freelist is empty or we need to perform
 * debugging duties.
 *
 * Interrupts are disabled.
 *
 * 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, void *addr, struct kmem_cache_cpu *c)
{
        void **object;
        struct page *new;

        /* We handle __GFP_ZERO in the caller */
        gfpflags &= ~__GFP_ZERO;

        if (!c->page)
                goto new_slab;

        slab_lock(c->page);
        if (unlikely(!node_match(c, node)))
                goto another_slab;

        stat(c, ALLOC_REFILL);

load_freelist:
        object = c->page->freelist;
        if (unlikely(!object))
                goto another_slab;
        if (unlikely(SLABDEBUG && PageSlubDebug(c->page)))
                goto debug;

        c->freelist = object[c->offset];
        c->page->inuse = c->page->objects;
        c->page->freelist = NULL;
        c->node = page_to_nid(c->page);
unlock_out:
        slab_unlock(c->page);
        stat(c, ALLOC_SLOWPATH);
        return object;

another_slab:
        deactivate_slab(s, c);

new_slab:
        new = get_partial(s, gfpflags, node);
        if (new) {
                c->page = new;
                stat(c, ALLOC_FROM_PARTIAL);
                goto load_freelist;
        }

        if (gfpflags & __GFP_WAIT)
                local_irq_enable();

        new = new_slab(s, gfpflags, node);

        if (gfpflags & __GFP_WAIT)
                local_irq_disable();

        if (new) {
                c = get_cpu_slab(s, smp_processor_id());
                stat(c, ALLOC_SLAB);
                if (c->page)
                        flush_slab(s, c);
                slab_lock(new);
                __SetPageSlubFrozen(new);
                c->page = new;
                goto load_freelist;
        }
        return NULL;
debug:
        if (!alloc_debug_processing(s, c->page, object, addr))
                goto another_slab;

        c->page->inuse++;
        c->page->freelist = object[c->offset];
        c->node = -1;
        goto unlock_out;
}

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

        local_irq_save(flags);
        c = get_cpu_slab(s, smp_processor_id());
        objsize = c->objsize;
        if (unlikely(!c->freelist || !node_match(c, node)))

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

        else {
                object = c->freelist;
                c->freelist = object[c->offset];
                stat(c, ALLOC_FASTPATH);
        }
        local_irq_restore(flags);

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

        return object;
}

void *kmem_cache_alloc(struct kmem_cache *s, gfp_t gfpflags)
{
        return slab_alloc(s, gfpflags, -1, __builtin_return_address(0));
}
EXPORT_SYMBOL(kmem_cache_alloc);

#ifdef CONFIG_NUMA
void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node)
{
        return slab_alloc(s, gfpflags, node, __builtin_return_address(0));
}
EXPORT_SYMBOL(kmem_cache_alloc_node);
#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, void *addr, unsigned int offset)
{
        void *prior;
        void **object = (void *)x;
        struct kmem_cache_cpu *c;

        c = get_cpu_slab(s, raw_smp_processor_id());
        stat(c, FREE_SLOWPATH);
        slab_lock(page);

        if (unlikely(SLABDEBUG && PageSlubDebug(page)))
                goto debug;

checks_ok:
        prior = object[offset] = page->freelist;
        page->freelist = object;
        page->inuse--;

        if (unlikely(PageSlubFrozen(page))) {
                stat(c, FREE_FROZEN);
                goto out_unlock;
        }

        if (unlikely(!page->inuse))
                goto slab_empty;

        /*
         * Objects left in the slab. If it was not on the partial list before
         * then add it.
         */
        if (unlikely(!prior)) {
                add_partial(get_node(s, page_to_nid(page)), page, 1);
                stat(c, FREE_ADD_PARTIAL);
        }

out_unlock:
        slab_unlock(page);
        return;

slab_empty:
        if (prior) {
                /*
                 * Slab still on the partial list.
                 */
                remove_partial(s, page);
                stat(c, FREE_REMOVE_PARTIAL);
        }
        slab_unlock(page);
        stat(c, FREE_SLAB);
        discard_slab(s, page);
        return;

debug:
        if (!free_debug_processing(s, page, x, addr))
                goto out_unlock;
        goto checks_ok;
}

/*
 * 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, void *addr)
{
        void **object = (void *)x;
        struct kmem_cache_cpu *c;
        unsigned long flags;

        local_irq_save(flags);
        c = get_cpu_slab(s, smp_processor_id());
        debug_check_no_locks_freed(object, c->objsize);
        if (!(s->flags & SLAB_DEBUG_OBJECTS))
                debug_check_no_obj_freed(object, s->objsize);
        if (likely(page == c->page && c->node >= 0)) {
                object[c->offset] = c->freelist;
                c->freelist = object;
                stat(c, FREE_FASTPATH);
        } else
                __slab_free(s, page, x, addr, c->offset);

        local_irq_restore(flags);
}

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

        page = virt_to_head_page(x);

        slab_free(s, page, x, __builtin_return_address(0));
}
EXPORT_SYMBOL(kmem_cache_free);

/* Figure out on which slab object the object resides */
static struct page *get_object_page(const void *x)
{
        struct page *page = virt_to_head_page(x);

        if (!PageSlab(page))
                return NULL;

        return page;
}

/*
 * 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 order;
        int rem;
        int min_order = slub_min_order;

        if ((PAGE_SIZE << min_order) / size > 65535)
                return get_order(size * 65535) - 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)
                        continue;

                rem = slab_size % size;

                if (rem <= slab_size / fract_leftover)
                        break;

        }

        return order;
}

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

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

        /*
         * 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);
        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);
        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_cpu(struct kmem_cache *s,
                        struct kmem_cache_cpu *c)
{
        c->page = NULL;
        c->freelist = NULL;
        c->node = 0;
        c->offset = s->offset / sizeof(void *);
        c->objsize = s->objsize;
#ifdef CONFIG_SLUB_STATS
        memset(c->stat, 0, NR_SLUB_STAT_ITEMS * sizeof(unsigned));
#endif
}

static void
init_kmem_cache_node(struct kmem_cache_node *n, struct kmem_cache *s)
{
        n->nr_partial = 0;

        /*
         * The larger the object size is, the more pages we want on the partial
         * list to avoid pounding the page allocator excessively.
         */
        n->min_partial = ilog2(s->size);
        if (n->min_partial < MIN_PARTIAL)
                n->min_partial = MIN_PARTIAL;
        else if (n->min_partial > MAX_PARTIAL)
                n->min_partial = MAX_PARTIAL;

        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
}

#ifdef CONFIG_SMP
/*
 * Per cpu array for per cpu structures.
 *
 * The per cpu array places all kmem_cache_cpu structures from one processor
 * close together meaning that it becomes possible that multiple per cpu
 * structures are contained in one cacheline. This may be particularly
 * beneficial for the kmalloc caches.
 *
 * A desktop system typically has around 60-80 slabs. With 100 here we are
 * likely able to get per cpu structures for all caches from the array defined
 * here. We must be able to cover all kmalloc caches during bootstrap.
 *
 * If the per cpu array is exhausted then fall back to kmalloc
 * of individual cachelines. No sharing is possible then.
 */
#define NR_KMEM_CACHE_CPU 100

static DEFINE_PER_CPU(struct kmem_cache_cpu,
                                kmem_cache_cpu)[NR_KMEM_CACHE_CPU];

static DEFINE_PER_CPU(struct kmem_cache_cpu *, kmem_cache_cpu_free);
static cpumask_t kmem_cach_cpu_free_init_once = CPU_MASK_NONE;

static struct kmem_cache_cpu *alloc_kmem_cache_cpu(struct kmem_cache *s,
                                                        int cpu, gfp_t flags)
{
        struct kmem_cache_cpu *c = per_cpu(kmem_cache_cpu_free, cpu);

        if (c)
                per_cpu(kmem_cache_cpu_free, cpu) =
                                (void *)c->freelist;
        else {
                /* Table overflow: So allocate ourselves */
                c = kmalloc_node(
                        ALIGN(sizeof(struct kmem_cache_cpu), cache_line_size()),
                        flags, cpu_to_node(cpu));
                if (!c)
                        return NULL;
        }

        init_kmem_cache_cpu(s, c);
        return c;
}

static void free_kmem_cache_cpu(struct kmem_cache_cpu *c, int cpu)
{
        if (c < per_cpu(kmem_cache_cpu, cpu) ||
                        c > per_cpu(kmem_cache_cpu, cpu) + NR_KMEM_CACHE_CPU) {
                kfree(c);
                return;
        }
        c->freelist = (void *)per_cpu(kmem_cache_cpu_free, cpu);
        per_cpu(kmem_cache_cpu_free, cpu) = c;
}

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

        for_each_online_cpu(cpu) {
                struct kmem_cache_cpu *c = get_cpu_slab(s, cpu);

                if (c) {
                        s->cpu_slab[cpu] = NULL;
                        free_kmem_cache_cpu(c, cpu);
                }
        }
}

static int alloc_kmem_cache_cpus(struct kmem_cache *s, gfp_t flags)
{
        int cpu;

        for_each_online_cpu(cpu) {
                struct kmem_cache_cpu *c = get_cpu_slab(s, cpu);

                if (c)
                        continue;

                c = alloc_kmem_cache_cpu(s, cpu, flags);
                if (!c) {
                        free_kmem_cache_cpus(s);
                        return 0;
                }
                s->cpu_slab[cpu] = c;
        }
        return 1;
}

/*
 * Initialize the per cpu array.
 */
static void init_alloc_cpu_cpu(int cpu)
{
        int i;

        if (cpu_isset(cpu, kmem_cach_cpu_free_init_once))
                return;

        for (i = NR_KMEM_CACHE_CPU - 1; i >= 0; i--)
                free_kmem_cache_cpu(&per_cpu(kmem_cache_cpu, cpu)[i], cpu);

        cpu_set(cpu, kmem_cach_cpu_free_init_once);
}

static void __init init_alloc_cpu(void)
{
        int cpu;

        for_each_online_cpu(cpu)
                init_alloc_cpu_cpu(cpu);
  }

#else
static inline void free_kmem_cache_cpus(struct kmem_cache *s) {}
static inline void init_alloc_cpu(void) {}

static inline int alloc_kmem_cache_cpus(struct kmem_cache *s, gfp_t flags)
{
        init_kmem_cache_cpu(s, &s->cpu_slab);
        return 1;
}
#endif

#ifdef CONFIG_NUMA
/*
 * 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 struct kmem_cache_node *early_kmem_cache_node_alloc(gfp_t gfpflags,
                                                           int node)
{
        struct page *page;
        struct kmem_cache_node *n;
        unsigned long flags;

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

        page = new_slab(kmalloc_caches, gfpflags, 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(kmalloc_caches, n);
        page->inuse++;
        kmalloc_caches->node[node] = n;
#ifdef CONFIG_SLUB_DEBUG
        init_object(kmalloc_caches, n, 1);
        init_tracking(kmalloc_caches, n);
#endif
        init_kmem_cache_node(n, kmalloc_caches);
        inc_slabs_node(kmalloc_caches, node, page->objects);

        /*
         * lockdep requires consistent irq usage for each lock
         * so even though there cannot be a race this early in
         * the boot sequence, we still disable irqs.
         */
        local_irq_save(flags);
        add_partial(n, page, 0);
        local_irq_restore(flags);
        return n;
}

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 && n != &s->local_node)
                        kmem_cache_free(kmalloc_caches, n);
                s->node[node] = NULL;
        }
}

static int init_kmem_cache_nodes(struct kmem_cache *s, gfp_t gfpflags)
{
        int node;
        int local_node;

        if (slab_state >= UP)
                local_node = page_to_nid(virt_to_page(s));
        else
                local_node = 0;

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

                if (local_node == node)
                        n = &s->local_node;
                else {
                        if (slab_state == DOWN) {
                                n = early_kmem_cache_node_alloc(gfpflags,
                                                                node);
                                continue;
                        }
                        n = kmem_cache_alloc_node(kmalloc_caches,
                                                        gfpflags, node);

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

                }
                s->node[node] = n;
                init_kmem_cache_node(n, s);
        }
        return 1;
}
#else
static void free_kmem_cache_nodes(struct kmem_cache *s)
{
}

static int init_kmem_cache_nodes(struct kmem_cache *s, gfp_t gfpflags)
{
        init_kmem_cache_node(&s->local_node, s);
        return 1;
}
#endif

/*
 * 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->objsize;
        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->objsize)
                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 an 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->objsize);

        /*
         * 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);

        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->min = oo_make(get_order(size), size);
        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, gfp_t gfpflags,
                const char *name, size_t size,
                size_t align, unsigned long flags,
                void (*ctor)(void *))
{
        memset(s, 0, kmem_size);
        s->name = name;
        s->ctor = ctor;
        s->objsize = size;
        s->align = align;
        s->flags = kmem_cache_flags(size, flags, name, ctor);

        if (!calculate_sizes(s, -1))
                goto error;

        s->refcount = 1;
#ifdef CONFIG_NUMA
        s->remote_node_defrag_ratio = 1000;
#endif
        if (!init_kmem_cache_nodes(s, gfpflags & ~SLUB_DMA))
                goto error;

        if (alloc_kmem_cache_cpus(s, gfpflags & ~SLUB_DMA))
                return 1;
        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)size, s->size, oo_order(s->oo),
                        s->offset, flags);
        return 0;
}

/*
 * Check if a given pointer is valid
 */
int kmem_ptr_validate(struct kmem_cache *s, const void *object)
{
        struct page *page;

        page = get_object_page(object);

        if (!page || s != page->slab)
                /* No slab or wrong slab */
                return 0;

        if (!check_valid_pointer(s, page, object))
                return 0;

        /*
         * We could also check if the object is on the slabs freelist.
         * But this would be too expensive and it seems that the main
         * purpose of kmem_ptr_valid() is to check if the object belongs
         * to a certain slab.
         */
        return 1;
}
EXPORT_SYMBOL(kmem_ptr_validate);

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

const char *kmem_cache_name(struct kmem_cache *s)
{
        return s->name;
}
EXPORT_SYMBOL(kmem_cache_name);

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;
        DECLARE_BITMAP(map, page->objects);

        bitmap_zero(map, page->objects);
        slab_err(s, page, "%s", text);
        slab_lock(page);
        for_each_free_object(p, s, page->freelist)
                set_bit(slab_index(p, s, addr), 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);
#endif
}

/*
 * Attempt to free all partial slabs on a node.
 */
static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
{
        unsigned long flags;
        struct page *page, *h;

        spin_lock_irqsave(&n->list_lock, flags);
        list_for_each_entry_safe(page, h, &n->partial, lru) {
                if (!page->inuse) {
                        list_del(&page->lru);
                        discard_slab(s, page);
                        n->nr_partial--;
                } else {
                        list_slab_objects(s, page,
                                "Objects remaining on kmem_cache_close()");
                }
        }
        spin_unlock_irqrestore(&n->list_lock, flags);
}

/*
 * 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 */
        free_kmem_cache_cpus(s);
        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_kmem_cache_nodes(s);
        return 0;
}

/*
 * Close a cache and release the kmem_cache structure
 * (must be used for caches created using kmem_cache_create)
 */
void kmem_cache_destroy(struct kmem_cache *s)
{
        down_write(&slub_lock);
        s->refcount--;
        if (!s->refcount) {
                list_del(&s->list);
                up_write(&slub_lock);
                if (kmem_cache_close(s)) {
                        printk(KERN_ERR "SLUB %s: %s called for cache that "
                                "still has objects.\n", s->name, __func__);
                        dump_stack();
                }
                sysfs_slab_remove(s);
        } else
                up_write(&slub_lock);
}
EXPORT_SYMBOL(kmem_cache_destroy);

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

struct kmem_cache kmalloc_caches[PAGE_SHIFT + 1] __cacheline_aligned;
EXPORT_SYMBOL(kmalloc_caches);

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);

        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 *create_kmalloc_cache(struct kmem_cache *s,
                const char *name, int size, gfp_t gfp_flags)
{
        unsigned int flags = 0;

        if (gfp_flags & SLUB_DMA)
                flags = SLAB_CACHE_DMA;

        down_write(&slub_lock);
        if (!kmem_cache_open(s, gfp_flags, name, size, ARCH_KMALLOC_MINALIGN,
                                                                flags, NULL))
                goto panic;

        list_add(&s->list, &slab_caches);
        up_write(&slub_lock);
        if (sysfs_slab_add(s))
                goto panic;
        return s;

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

#ifdef CONFIG_ZONE_DMA
static struct kmem_cache *kmalloc_caches_dma[PAGE_SHIFT + 1];

static void sysfs_add_func(struct work_struct *w)
{
        struct kmem_cache *s;

        down_write(&slub_lock);
        list_for_each_entry(s, &slab_caches, list) {
                if (s->flags & __SYSFS_ADD_DEFERRED) {
                        s->flags &= ~__SYSFS_ADD_DEFERRED;
                        sysfs_slab_add(s);
                }
        }
        up_write(&slub_lock);
}

static DECLARE_WORK(sysfs_add_work, sysfs_add_func);

static noinline struct kmem_cache *dma_kmalloc_cache(int index, gfp_t flags)
{
        struct kmem_cache *s;
        char *text;
        size_t realsize;

        s = kmalloc_caches_dma[index];
        if (s)
                return s;

        /* Dynamically create dma cache */
        if (flags & __GFP_WAIT)
                down_write(&slub_lock);
        else {
                if (!down_write_trylock(&slub_lock))
                        goto out;
        }

        if (kmalloc_caches_dma[index])
                goto unlock_out;

        realsize = kmalloc_caches[index].objsize;
        text = kasprintf(flags & ~SLUB_DMA, "kmalloc_dma-%d",
                         (unsigned int)realsize);
        s = kmalloc(kmem_size, flags & ~SLUB_DMA);

        if (!s || !text || !kmem_cache_open(s, flags, text,
                        realsize, ARCH_KMALLOC_MINALIGN,
                        SLAB_CACHE_DMA|__SYSFS_ADD_DEFERRED, NULL)) {
                kfree(s);
                kfree(text);
                goto unlock_out;
        }

        list_add(&s->list, &slab_caches);
        kmalloc_caches_dma[index] = s;

        schedule_work(&sysfs_add_work);

unlock_out:
        up_write(&slub_lock);
out:
        return kmalloc_caches_dma[index];
}
#endif

/*
 * 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 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 - 1) / 8];
        } else
                index = fls(size - 1);

#ifdef CONFIG_ZONE_DMA
        if (unlikely((flags & SLUB_DMA)))
                return dma_kmalloc_cache(index, flags);

#endif
        return &kmalloc_caches[index];
}

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

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

        s = get_slab(size, flags);

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

        return slab_alloc(s, flags, -1, __builtin_return_address(0));
}
EXPORT_SYMBOL(__kmalloc);

static void *kmalloc_large_node(size_t size, gfp_t flags, int node)
{
        struct page *page = alloc_pages_node(node, flags | __GFP_COMP,
                                                get_order(size));

        if (page)
                return page_address(page);
        else
                return NULL;
}

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

        if (unlikely(size > PAGE_SIZE))
                return kmalloc_large_node(size, flags, node);

        s = get_slab(size, flags);

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

        return slab_alloc(s, flags, node, __builtin_return_address(0));
}
EXPORT_SYMBOL(__kmalloc_node);
#endif

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

        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);
        }
        s = page->slab;

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

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

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

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

        page = virt_to_head_page(x);
        if (unlikely(!PageSlab(page))) {
                BUG_ON(!PageCompound(page));
                put_page(page);
                return;
        }
        slab_free(page->slab, page, object, __builtin_return_address(0));
}
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) {
                        if (!page->inuse && slab_trylock(page)) {
                                /*
                                 * Must hold slab lock here because slab_free
                                 * may have freed the last object and be
                                 * waiting to release the slab.
                                 */
                                list_del(&page->lru);
                                n->nr_partial--;
                                slab_unlock(page);
                                discard_slab(s, page);
                        } else {
                                list_move(&page->lru,
                                slabs_by_inuse + page->inuse);
                        }
                }

                /*
                 * 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);
        }

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

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

        down_read(&slub_lock);
        list_for_each_entry(s, &slab_caches, list)
                kmem_cache_shrink(s);
        up_read(&slub_lock);

        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;

        down_read(&slub_lock);
        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 shoudn't call this
                         * callback. So, we must fail.
                         */
                        BUG_ON(slabs_node(s, offline_node));

                        s->node[offline_node] = NULL;
                        kmem_cache_free(kmalloc_caches, n);
                }
        }
        up_read(&slub_lock);
}

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.
         */
        down_read(&slub_lock);
        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(kmalloc_caches, GFP_KERNEL);
                if (!n) {
                        ret = -ENOMEM;
                        goto out;
                }
                init_kmem_cache_node(n, s);
                s->node[nid] = n;
        }
out:
        up_read(&slub_lock);
        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
 *******************************************************************/

void __init kmem_cache_init(void)
{
        int i;
        int caches = 0;

        init_alloc_cpu();

#ifdef CONFIG_NUMA
        /*
         * 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.
         */
        create_kmalloc_cache(&kmalloc_caches[0], "kmem_cache_node",
                sizeof(struct kmem_cache_node), GFP_KERNEL);
        kmalloc_caches[0].refcount = -1;
        caches++;

        hotplug_memory_notifier(slab_memory_callback, SLAB_CALLBACK_PRI);
#endif

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

        /* Caches that are not of the two-to-the-power-of size */
        if (KMALLOC_MIN_SIZE <= 64) {
                create_kmalloc_cache(&kmalloc_caches[1],
                                "kmalloc-96", 96, GFP_KERNEL);
                caches++;
                create_kmalloc_cache(&kmalloc_caches[2],
                                "kmalloc-192", 192, GFP_KERNEL);
                caches++;
        }

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


        /*
         * 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)));