Slab allocators: Drop support for destructors

[usb.git] / mm / slub.c

/*
 * 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 <clameter@sgi.com>
 */

#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/seq_file.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/mempolicy.h>
#include <linux/ctype.h>
#include <linux/kallsyms.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 used as a cpu cache. Allocations
 *                      may be performed from the slab. The slab is not
 *                      on any slab list and cannot be moved onto one.
 *                      The cpu slab may be equipped with an additioanl
 *                      lockless_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.
 */

static inline int SlabDebug(struct page *page)
{
#ifdef CONFIG_SLUB_DEBUG
        return PageError(page);
#else
        return 0;
#endif
}

static inline void SetSlabDebug(struct page *page)
{
#ifdef CONFIG_SLUB_DEBUG
        SetPageError(page);
#endif
}

static inline void ClearSlabDebug(struct page *page)
{
#ifdef CONFIG_SLUB_DEBUG
        ClearPageError(page);
#endif
}

/*
 * Issues still to be resolved:
 *
 * - The per cpu array is updated for each new slab and and is a remote
 *   cacheline for most nodes. This could become a bouncing cacheline given
 *   enough frequent updates. There are 16 pointers in a cacheline, so at
 *   max 16 cpus could compete for the cacheline which may be okay.
 *
 * - 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

#if PAGE_SHIFT <= 12

/*
 * Small page size. Make sure that we do not fragment memory
 */
#define DEFAULT_MAX_ORDER 1
#define DEFAULT_MIN_OBJECTS 4

#else

/*
 * Large page machines are customarily able to handle larger
 * page orders.
 */
#define DEFAULT_MAX_ORDER 2
#define DEFAULT_MIN_OBJECTS 8

#endif

/*
 * 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 2

/*
 * 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 */

/* Not all arches define cache_line_size */
#ifndef cache_line_size
#define cache_line_size()       L1_CACHE_BYTES
#endif

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);
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 };

#if defined(CONFIG_SYSFS) && defined(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 int sysfs_slab_add(struct kmem_cache *s) { return 0; }
static int sysfs_slab_alias(struct kmem_cache *s, const char *p) { return 0; }
static void sysfs_slab_remove(struct kmem_cache *s) {}
#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 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 + s->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) \
        for (__p = (__addr); __p < (__addr) + (__s)->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;
}

#ifdef CONFIG_SLUB_DEBUG
/*
 * Debug settings:
 */
static int slub_debug;

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 "%10s 0x%p: ", text, addr + i);
                        newline = 0;
                }
                printk(" %02x", addr[i]);
                offset = i % 16;
                ascii[offset] = isgraph(addr[i]) ? addr[i] : '.';
                if (offset == 15) {
                        printk(" %s\n",ascii);
                        newline = 1;
                }
        }
        if (!newline) {
                i %= 16;
                while (i < 16) {
                        printk("   ");
                        ascii[i] = ' ';
                        i++;
                }
                printk(" %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 ? current->pid : -1;
                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) {
                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 "%s: ", s);
        __print_symbol("%s", (unsigned long)t->addr);
        printk(" jiffies_ago=%lu cpu=%u pid=%d\n", jiffies - t->when, t->cpu, t->pid);
}

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

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

        printk(KERN_ERR "FreePointer 0x%p -> 0x%p\n",
                        p + s->offset,
                        get_freepointer(s, p));

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

        if (s->flags & SLAB_STORE_USER) {
                print_track("Last alloc", get_track(s, p, TRACK_ALLOC));
                print_track("Last free ", get_track(s, p, TRACK_FREE));
                off += 2 * sizeof(struct track);
        }

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

static void object_err(struct kmem_cache *s, struct page *page,
                        u8 *object, char *reason)
{
        u8 *addr = page_address(page);

        printk(KERN_ERR "*** SLUB %s: %s@0x%p slab 0x%p\n",
                        s->name, reason, object, page);
        printk(KERN_ERR "    offset=%tu flags=0x%04lx inuse=%u freelist=0x%p\n",
                object - addr, page->flags, page->inuse, page->freelist);
        if (object > addr + 16)
                print_section("Bytes b4", object - 16, 16);
        print_section("Object", object, min(s->objsize, 128));
        print_trailer(s, object);
        dump_stack();
}

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

        va_start(args, reason);
        vsnprintf(buf, sizeof(buf), reason, args);
        va_end(args);
        printk(KERN_ERR "*** SLUB %s: %s in slab @0x%p\n", s->name, buf,
                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 int check_bytes(u8 *start, unsigned int value, unsigned int bytes)
{
        while (bytes) {
                if (*start != (u8)value)
                        return 0;
                start++;
                bytes--;
        }
        return 1;
}

/*
 * 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 debuggin 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 void restore_bytes(struct kmem_cache *s, char *message, u8 data,
                                                void *from, void *to)
{
        printk(KERN_ERR "@@@ SLUB %s: Restoring %s (0x%x) from 0x%p-0x%p\n",
                s->name, message, data, from, to - 1);
        memset(from, data, to - from);
}

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;

        if (check_bytes(p + off, POISON_INUSE, s->size - off))
                return 1;

        object_err(s, page, p, "Object padding check fails");

        /*
         * Restore padding
         */
        restore_bytes(s, "object padding", POISON_INUSE, p + off, p + s->size);
        return 0;
}

static int slab_pad_check(struct kmem_cache *s, struct page *page)
{
        u8 *p;
        int length, remainder;

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

        p = page_address(page);
        length = s->objects * s->size;
        remainder = (PAGE_SIZE << s->order) - length;
        if (!remainder)
                return 1;

        if (!check_bytes(p + length, POISON_INUSE, remainder)) {
                slab_err(s, page, "Padding check failed");
                restore_bytes(s, "slab padding", POISON_INUSE, p + length,
                        p + length + remainder);
                return 0;
        }
        return 1;
}

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(endobject, red, s->inuse - s->objsize)) {
                        object_err(s, page, object,
                        active ? "Redzone Active" : "Redzone Inactive");
                        restore_bytes(s, "redzone", red,
                                endobject, object + s->inuse);
                        return 0;
                }
        } else {
                if ((s->flags & SLAB_POISON) && s->objsize < s->inuse &&
                        !check_bytes(endobject, POISON_INUSE,
                                        s->inuse - s->objsize)) {
                object_err(s, page, p, "Alignment padding check fails");
                /*
                 * Fix it so that there will not be another report.
                 *
                 * Hmmm... We may be corrupting an object that now expects
                 * to be longer than allowed.
                 */
                restore_bytes(s, "alignment padding", POISON_INUSE,
                        endobject, object + s->inuse);
                }
        }

        if (s->flags & SLAB_POISON) {
                if (!active && (s->flags & __OBJECT_POISON) &&
                        (!check_bytes(p, POISON_FREE, s->objsize - 1) ||
                                p[s->objsize - 1] != POISON_END)) {

                        object_err(s, page, p, "Poison check failed");
                        restore_bytes(s, "Poison", POISON_FREE,
                                                p, p + s->objsize -1);
                        restore_bytes(s, "Poison", POISON_END,
                                        p + s->objsize - 1, p + s->objsize);
                        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)
{
        VM_BUG_ON(!irqs_disabled());

        if (!PageSlab(page)) {
                slab_err(s, page, "Not a valid slab page flags=%lx "
                        "mapping=0x%p count=%d", page->flags, page->mapping,
                        page_count(page));
                return 0;
        }
        if (page->offset * sizeof(void *) != s->offset) {
                slab_err(s, page, "Corrupted offset %lu flags=0x%lx "
                        "mapping=0x%p count=%d",
                        (unsigned long)(page->offset * sizeof(void *)),
                        page->flags,
                        page->mapping,
                        page_count(page));
                return 0;
        }
        if (page->inuse > s->objects) {
                slab_err(s, page, "inuse %u > max %u @0x%p flags=%lx "
                        "mapping=0x%p count=%d",
                        s->name, page->inuse, s->objects, page->flags,
                        page->mapping, page_count(page));
                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;

        while (fp && nr <= s->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 0x%p corrupt",
                                                                        fp);
                                page->freelist = NULL;
                                page->inuse = s->objects;
                                printk(KERN_ERR "@@@ SLUB %s: Freelist "
                                        "cleared. Slab 0x%p\n",
                                        s->name, page);
                                return 0;
                        }
                        break;
                }
                object = fp;
                fp = get_freepointer(s, object);
                nr++;
        }

        if (page->inuse != s->objects - nr) {
                slab_err(s, page, "Wrong object count. Counter is %d but "
                        "counted were %d", s, page, page->inuse,
                                                        s->objects - nr);
                page->inuse = s->objects - nr;
                printk(KERN_ERR "@@@ SLUB %s: Object count adjusted. "
                        "Slab @0x%p\n", s->name, page);
        }
        return search == NULL;
}

/*
 * 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);
}

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

        if (object && !on_freelist(s, page, object)) {
                slab_err(s, page, "Object 0x%p already allocated", object);
                goto bad;
        }

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

        if (!object)
                return 1;

        if (!check_object(s, page, object, 0))
                goto bad;

        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.
                 */
                printk(KERN_ERR "@@@ SLUB: %s slab 0x%p. Marking all objects used.\n",
                        s->name, page);
                page->inuse = s->objects;
                page->freelist = NULL;
                /* Fix up fields that may be corrupted */
                page->offset = s->offset / sizeof(void *);
        }
        return 0;
}

static int free_object_checks(struct kmem_cache *s, struct page *page,
                                                        void *object)
{
        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)) {
                slab_err(s, page, "Object 0x%p already free", object);
                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
                        slab_err(s, page, "object at 0x%p belongs "
                                "to slab %s", object, page->slab->name);
                goto fail;
        }
        return 1;
fail:
        printk(KERN_ERR "@@@ SLUB: %s slab 0x%p object at 0x%p not freed.\n",
                s->name, page, object);
        return 0;
}

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();
        }
}

static int __init setup_slub_debug(char *str)
{
        if (!str || *str != '=')
                slub_debug = DEBUG_DEFAULT_FLAGS;
        else {
                str++;
                if (*str == 0 || *str == ',')
                        slub_debug = DEBUG_DEFAULT_FLAGS;
                else
                for( ;*str && *str != ','; str++)
                        switch (*str) {
                        case 'f' : case 'F' :
                                slub_debug |= SLAB_DEBUG_FREE;
                                break;
                        case 'z' : case 'Z' :
                                slub_debug |= SLAB_RED_ZONE;
                                break;
                        case 'p' : case 'P' :
                                slub_debug |= SLAB_POISON;
                                break;
                        case 'u' : case 'U' :
                                slub_debug |= SLAB_STORE_USER;
                                break;
                        case 't' : case 'T' :
                                slub_debug |= SLAB_TRACE;
                                break;
                        default:
                                printk(KERN_ERR "slub_debug option '%c' "
                                        "unknown. skipped\n",*str);
                        }
        }

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

__setup("slub_debug", setup_slub_debug);

static void kmem_cache_open_debug_check(struct kmem_cache *s)
{
        /*
         * The page->offset field is only 16 bit wide. This is an offset
         * in units of words from the beginning of an object. If the slab
         * size is bigger then we cannot move the free pointer behind the
         * object anymore.
         *
         * On 32 bit platforms the limit is 256k. On 64bit platforms
         * the limit is 512k.
         *
         * Debugging or ctor may create a need to move the free
         * pointer. Fail if this happens.
         */
        if (s->size >= 65535 * sizeof(void *)) {
                BUG_ON(s->flags & (SLAB_RED_ZONE | SLAB_POISON |
                                SLAB_STORE_USER | SLAB_DESTROY_BY_RCU));
                BUG_ON(s->ctor);
        }
        else
                /*
                 * Enable debugging if selected on the kernel commandline.
                 */
                if (slub_debug && (!slub_debug_slabs ||
                    strncmp(slub_debug_slabs, s->name,
                        strlen(slub_debug_slabs)) == 0))
                                s->flags |= slub_debug;
}
#else

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

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

static inline void add_full(struct kmem_cache_node *n, struct page *page) {}
static inline void remove_full(struct kmem_cache *s, struct page *page) {}
static inline void trace(struct kmem_cache *s, struct page *page,
                        void *object, int alloc) {}
static inline void init_object(struct kmem_cache *s,
                        void *object, int active) {}
static inline void init_tracking(struct kmem_cache *s, void *object) {}
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 set_track(struct kmem_cache *s, void *object,
                        enum track_item alloc, void *addr) {}
static inline void kmem_cache_open_debug_check(struct kmem_cache *s) {}
#define slub_debug 0
#endif
/*
 * Slab allocation and freeing
 */
static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
{
        struct page * page;
        int pages = 1 << s->order;

        if (s->order)
                flags |= __GFP_COMP;

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

        if (node == -1)
                page = alloc_pages(flags, s->order);
        else
                page = alloc_pages_node(node, flags, s->order);

        if (!page)
                return NULL;

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

        return page;
}

static void setup_object(struct kmem_cache *s, struct page *page,
                                void *object)
{
        if (SlabDebug(page)) {
                init_object(s, object, 0);
                init_tracking(s, object);
        }

        if (unlikely(s->ctor))
                s->ctor(object, s, SLAB_CTOR_CONSTRUCTOR);
}

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

        BUG_ON(flags & ~(GFP_DMA | GFP_LEVEL_MASK));

        if (flags & __GFP_WAIT)
                local_irq_enable();

        page = allocate_slab(s, flags & GFP_LEVEL_MASK, node);
        if (!page)
                goto out;

        n = get_node(s, page_to_nid(page));
        if (n)
                atomic_long_inc(&n->nr_slabs);
        page->offset = s->offset / sizeof(void *);
        page->slab = s;
        page->flags |= 1 << PG_slab;
        if (s->flags & (SLAB_DEBUG_FREE | SLAB_RED_ZONE | SLAB_POISON |
                        SLAB_STORE_USER | SLAB_TRACE))
                SetSlabDebug(page);

        start = page_address(page);
        end = start + s->objects * s->size;

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

        last = start;
        for_each_object(p, s, start) {
                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->lockless_freelist = NULL;
        page->inuse = 0;
out:
        if (flags & __GFP_WAIT)
                local_irq_disable();
        return page;
}

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

        if (unlikely(SlabDebug(page))) {
                void *p;

                slab_pad_check(s, page);
                for_each_object(p, s, page_address(page))
                        check_object(s, page, p, 0);
        }

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

        page->mapping = NULL;
        __free_pages(page, s->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)
{
        struct kmem_cache_node *n = get_node(s, page_to_nid(page));

        atomic_long_dec(&n->nr_slabs);
        reset_page_mapcount(page);
        ClearSlabDebug(page);
        __ClearPageSlab(page);
        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_tail(struct kmem_cache_node *n, struct page *page)
{
        spin_lock(&n->list_lock);
        n->nr_partial++;
        list_add_tail(&page->lru, &n->partial);
        spin_unlock(&n->list_lock);
}

static void add_partial(struct kmem_cache_node *n, struct page *page)
{
        spin_lock(&n->list_lock);
        n->nr_partial++;
        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 int lock_and_del_slab(struct kmem_cache_node *n, struct page *page)
{
        if (slab_trylock(page)) {
                list_del(&page->lru);
                n->nr_partial--;
                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_del_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 zone **z;
        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/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->defrag_ratio || get_cycles() % 1024 > s->defrag_ratio)
                return NULL;

        zonelist = &NODE_DATA(slab_node(current->mempolicy))
                                        ->node_zonelists[gfp_zone(flags)];
        for (z = zonelist->zones; *z; z++) {
                struct kmem_cache_node *n;

                n = get_node(s, zone_to_nid(*z));

                if (n && cpuset_zone_allowed_hardwall(*z, flags) &&
                                n->nr_partial > 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 putback_slab(struct kmem_cache *s, struct page *page)
{
        struct kmem_cache_node *n = get_node(s, page_to_nid(page));

        if (page->inuse) {

                if (page->freelist)
                        add_partial(n, page);
                else if (SlabDebug(page) && (s->flags & SLAB_STORE_USER))
                        add_full(n, page);
                slab_unlock(page);

        } else {
                if (n->nr_partial < 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
                         * order to fill them up. That way the size of the
                         * partial list stays small. kmem_cache_shrink can
                         * reclaim empty slabs from the partial list.
                         */
                        add_partial_tail(n, page);
                        slab_unlock(page);
                } else {
                        slab_unlock(page);
                        discard_slab(s, page);
                }
        }
}

/*
 * Remove the cpu slab
 */
static void deactivate_slab(struct kmem_cache *s, struct page *page, int cpu)
{
        /*
         * Merge cpu freelist into freelist. Typically we get here
         * because both freelists are empty. So this is unlikely
         * to occur.
         */
        while (unlikely(page->lockless_freelist)) {
                void **object;

                /* Retrieve object from cpu_freelist */
                object = page->lockless_freelist;
                page->lockless_freelist = page->lockless_freelist[page->offset];

                /* And put onto the regular freelist */
                object[page->offset] = page->freelist;
                page->freelist = object;
                page->inuse--;
        }
        s->cpu_slab[cpu] = NULL;
        ClearPageActive(page);

        putback_slab(s, page);
}

static void flush_slab(struct kmem_cache *s, struct page *page, int cpu)
{
        slab_lock(page);
        deactivate_slab(s, page, cpu);
}

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

        if (likely(page))
                flush_slab(s, page, cpu);
}

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

        __flush_cpu_slab(s, cpu);
}

static void flush_all(struct kmem_cache *s)
{
#ifdef CONFIG_SMP
        on_each_cpu(flush_cpu_slab, s, 1, 1);
#else
        unsigned long flags;

        local_irq_save(flags);
        flush_cpu_slab(s);
        local_irq_restore(flags);
#endif
}

/*
 * 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 slowest path since we may sleep.
 */
static void *__slab_alloc(struct kmem_cache *s,
                gfp_t gfpflags, int node, void *addr, struct page *page)
{
        void **object;
        int cpu = smp_processor_id();

        if (!page)
                goto new_slab;

        slab_lock(page);
        if (unlikely(node != -1 && page_to_nid(page) != node))
                goto another_slab;
load_freelist:
        object = page->freelist;
        if (unlikely(!object))
                goto another_slab;
        if (unlikely(SlabDebug(page)))
                goto debug;

        object = page->freelist;
        page->lockless_freelist = object[page->offset];
        page->inuse = s->objects;
        page->freelist = NULL;
        slab_unlock(page);
        return object;

another_slab:
        deactivate_slab(s, page, cpu);

new_slab:
        page = get_partial(s, gfpflags, node);
        if (page) {
have_slab:
                s->cpu_slab[cpu] = page;
                SetPageActive(page);
                goto load_freelist;
        }

        page = new_slab(s, gfpflags, node);
        if (page) {
                cpu = smp_processor_id();
                if (s->cpu_slab[cpu]) {
                        /*
                         * Someone else populated the cpu_slab while we
                         * enabled interrupts, or we have gotten scheduled
                         * on another cpu. The page may not be on the
                         * requested node even if __GFP_THISNODE was
                         * specified. So we need to recheck.
                         */
                        if (node == -1 ||
                                page_to_nid(s->cpu_slab[cpu]) == node) {
                                /*
                                 * Current cpuslab is acceptable and we
                                 * want the current one since its cache hot
                                 */
                                discard_slab(s, page);
                                page = s->cpu_slab[cpu];
                                slab_lock(page);
                                goto load_freelist;
                        }
                        /* New slab does not fit our expectations */
                        flush_slab(s, s->cpu_slab[cpu], cpu);
                }
                slab_lock(page);
                goto have_slab;
        }
        return NULL;
debug:
        object = page->freelist;
        if (!alloc_object_checks(s, page, object))
                goto another_slab;
        if (s->flags & SLAB_STORE_USER)
                set_track(s, object, TRACK_ALLOC, addr);
        trace(s, page, object, 1);
        init_object(s, object, 1);

        page->inuse++;
        page->freelist = object[page->offset];
        slab_unlock(page);
        return object;
}

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

        local_irq_save(flags);
        page = s->cpu_slab[smp_processor_id()];
        if (unlikely(!page || !page->lockless_freelist ||
                        (node != -1 && page_to_nid(page) != node)))

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

        else {
                object = page->lockless_freelist;
                page->lockless_freelist = object[page->offset];
        }
        local_irq_restore(flags);
        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)
{
        void *prior;
        void **object = (void *)x;

        slab_lock(page);

        if (unlikely(SlabDebug(page)))
                goto debug;
checks_ok:
        prior = object[page->offset] = page->freelist;
        page->freelist = object;
        page->inuse--;

        if (unlikely(PageActive(page)))
                /*
                 * Cpu slabs are never on partial lists and are
                 * never freed.
                 */
                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);

out_unlock:
        slab_unlock(page);
        return;

slab_empty:
        if (prior)
                /*
                 * Slab still on the partial list.
                 */
                remove_partial(s, page);

        slab_unlock(page);
        discard_slab(s, page);
        return;

debug:
        if (!free_object_checks(s, page, x))
                goto out_unlock;
        if (!PageActive(page) && !page->freelist)
                remove_full(s, page);
        if (s->flags & SLAB_STORE_USER)
                set_track(s, x, TRACK_FREE, addr);
        trace(s, page, object, 0);
        init_object(s, object, 0);
        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 void __always_inline slab_free(struct kmem_cache *s,
                        struct page *page, void *x, void *addr)
{
        void **object = (void *)x;
        unsigned long flags;

        local_irq_save(flags);
        if (likely(page == s->cpu_slab[smp_processor_id()] &&
                                                !SlabDebug(page))) {
                object[page->offset] = page->lockless_freelist;
                page->lockless_freelist = object;
        } else
                __slab_free(s, page, x, addr);

        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 = DEFAULT_MAX_ORDER;
static int slub_min_objects = DEFAULT_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 1/8th 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;

        for (order = max(slub_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;
        while (min_objects > 1) {
                fraction = 8;
                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) &&
                        size > cache_line_size() / 2)
                return max_t(unsigned long, align, cache_line_size());

        if (align < ARCH_SLAB_MINALIGN)
                return ARCH_SLAB_MINALIGN;

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

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

#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.
 */
static struct kmem_cache_node * __init early_kmem_cache_node_alloc(gfp_t gfpflags,
                                                                int node)
{
        struct page *page;
        struct kmem_cache_node *n;

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

        page = new_slab(kmalloc_caches, gfpflags | GFP_THISNODE, node);
        /* new_slab() disables interupts */
        local_irq_enable();

        BUG_ON(!page);
        n = page->freelist;
        BUG_ON(!n);
        page->freelist = get_freepointer(kmalloc_caches, n);
        page->inuse++;
        kmalloc_caches->node[node] = n;
        init_object(kmalloc_caches, n, 1);
        init_kmem_cache_node(n);
        atomic_long_inc(&n->nr_slabs);
        add_partial(n, page);
        return n;
}

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

        for_each_online_node(node) {
                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_online_node(node) {
                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);
        }
        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);
        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)
{
        unsigned long flags = s->flags;
        unsigned long size = s->objsize;
        unsigned long align = s->align;

        /*
         * 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;

        /*
         * 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
        /*
         * 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;

#ifdef CONFIG_SLUB_DEBUG
        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 *);
        }

        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;

        s->order = calculate_order(size);
        if (s->order < 0)
                return 0;

        /*
         * Determine the number of objects per slab
         */
        s->objects = (PAGE_SIZE << s->order) / size;

        /*
         * Verify that the number of objects is within permitted limits.
         * The page->inuse field is only 16 bit wide! So we cannot have
         * more than 64k objects per slab.
         */
        if (!s->objects || s->objects > 65535)
                return 0;
        return 1;

}

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 *, struct kmem_cache *, unsigned long))
{
        memset(s, 0, kmem_size);
        s->name = name;
        s->ctor = ctor;
        s->objsize = size;
        s->flags = flags;
        s->align = align;
        kmem_cache_open_debug_check(s);

        if (!calculate_sizes(s))
                goto error;

        s->refcount = 1;
#ifdef CONFIG_NUMA
        s->defrag_ratio = 100;
#endif

        if (init_kmem_cache_nodes(s, gfpflags & ~SLUB_DMA))
                return 1;
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, s->order,
                        s->offset, flags);
        return 0;
}
EXPORT_SYMBOL(kmem_cache_open);

/*
 * 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);

/*
 * Attempt to free all slabs on a node. Return the number of slabs we
 * were unable to free.
 */
static int free_list(struct kmem_cache *s, struct kmem_cache_node *n,
                        struct list_head *list)
{
        int slabs_inuse = 0;
        unsigned long flags;
        struct page *page, *h;

        spin_lock_irqsave(&n->list_lock, flags);
        list_for_each_entry_safe(page, h, list, lru)
                if (!page->inuse) {
                        list_del(&page->lru);
                        discard_slab(s, page);
                } else
                        slabs_inuse++;
        spin_unlock_irqrestore(&n->list_lock, flags);
        return slabs_inuse;
}

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

        flush_all(s);

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

                n->nr_partial -= free_list(s, n, &n->partial);
                if (atomic_long_read(&n->nr_slabs))
                        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);
                if (kmem_cache_close(s))
                        WARN_ON(1);
                sysfs_slab_remove(s);
                kfree(s);
        }
        up_write(&slub_lock);
}
EXPORT_SYMBOL(kmem_cache_destroy);

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

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

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

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

        return 1;
}

__setup("slub_min_order=", setup_slub_min_order);

static int __init setup_slub_max_order(char *str)
{
        get_option (&str, &slub_max_order);

        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);
}

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

        if (!index)
                return NULL;

        /* Allocation too large? */
        BUG_ON(index < 0);

#ifdef CONFIG_ZONE_DMA
        if ((flags & SLUB_DMA)) {
                struct kmem_cache *s;
                struct kmem_cache *x;
                char *text;
                size_t realsize;

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

                /* Dynamically create dma cache */
                x = kmalloc(kmem_size, flags & ~SLUB_DMA);
                if (!x)
                        panic("Unable to allocate memory for dma cache\n");

                if (index <= KMALLOC_SHIFT_HIGH)
                        realsize = 1 << index;
                else {
                        if (index == 1)
                                realsize = 96;
                        else
                                realsize = 192;
                }

                text = kasprintf(flags & ~SLUB_DMA, "kmalloc_dma-%d",
                                (unsigned int)realsize);
                s = create_kmalloc_cache(x, text, realsize, flags);
                kmalloc_caches_dma[index] = s;
                return s;
        }
#endif
        return &kmalloc_caches[index];
}

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

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

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

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

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

        BUG_ON(!page);
        s = page->slab;
        BUG_ON(!s);

        /*
         * 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;

        /*
         * 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;
}
EXPORT_SYMBOL(ksize);

void kfree(const void *x)
{
        struct kmem_cache *s;
        struct page *page;

        if (!x)
                return;

        page = virt_to_head_page(x);
        s = page->slab;

        slab_free(s, page, (void *)x, __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;
        struct list_head *slabs_by_inuse =
                kmalloc(sizeof(struct list_head) * s->objects, GFP_KERNEL);
        unsigned long flags;

        if (!slabs_by_inuse)
                return -ENOMEM;

        flush_all(s);
        for_each_online_node(node) {
                n = get_node(s, node);

                if (!n->nr_partial)
                        continue;

                for (i = 0; i < s->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 {
                                if (n->nr_partial > MAX_PARTIAL)
                                        list_move(&page->lru,
                                        slabs_by_inuse + page->inuse);
                        }
                }

                if (n->nr_partial <= MAX_PARTIAL)
                        goto out;

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

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

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

/**
 * krealloc - reallocate memory. The contents will remain unchanged.
 * @p: object to reallocate memory for.
 * @new_size: how many bytes of memory are required.
 * @flags: the type of memory to allocate.
 *
 * The contents of the object pointed to are preserved up to the
 * lesser of the new and old sizes.  If @p is %NULL, krealloc()
 * behaves exactly like kmalloc().  If @size is 0 and @p is not a
 * %NULL pointer, the object pointed to is freed.
 */
void *krealloc(const void *p, size_t new_size, gfp_t flags)
{
        void *ret;
        size_t ks;

        if (unlikely(!p))
                return kmalloc(new_size, flags);

        if (unlikely(!new_size)) {
                kfree(p);
                return NULL;
        }

        ks = ksize(p);
        if (ks >= new_size)
                return (void *)p;

        ret = kmalloc(new_size, flags);
        if (ret) {
                memcpy(ret, p, min(new_size, ks));
                kfree(p);
        }
        return ret;
}
EXPORT_SYMBOL(krealloc);

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

void __init kmem_cache_init(void)
{
        int i;

#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);
#endif

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

        /* Caches that are not of the two-to-the-power-of size */
        create_kmalloc_cache(&kmalloc_caches[1],
                                "kmalloc-96", 96, GFP_KERNEL);
        create_kmalloc_cache(&kmalloc_caches[2],
                                "kmalloc-192", 192, GFP_KERNEL);

        for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++)
                create_kmalloc_cache(&kmalloc_caches[i],
                        "kmalloc", 1 << i, GFP_KERNEL);

        slab_state = UP;

        /* Provide the correct kmalloc names now that the caches are up */
        for (i = KMALLOC_SHIFT_LOW; i <= KMALLOC_SHIFT_HIGH; i++)
                kmalloc_caches[i]. name =
                        kasprintf(GFP_KERNEL, "kmalloc-%d", 1 << i);

#ifdef CONFIG_SMP
        register_cpu_notifier(&slab_notifier);
#endif

        kmem_size = offsetof(struct kmem_cache, cpu_slab) +
                                nr_cpu_ids * sizeof(struct page *);

        printk(KERN_INFO "SLUB: Genslabs=%d, HWalign=%d, Order=%d-%d, MinObjects=%d,"
                " Processors=%d, Nodes=%d\n",
                KMALLOC_SHIFT_HIGH, cache_line_size(),
                slub_min_order, slub_max_order, slub_min_objects,
                nr_cpu_ids, nr_node_ids);
}

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

        if (s->ctor)
                return 1;

        return 0;
}

static struct kmem_cache *find_mergeable(size_t size,
                size_t align, unsigned long flags,
                void (*ctor)(void *, struct kmem_cache *, unsigned long))
{
        struct list_head *h;

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

        if (ctor)
                return NULL;

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

        list_for_each(h, &slab_caches) {
                struct kmem_cache *s =
                        container_of(h, struct kmem_cache, list);

                if (slab_unmergeable(s))
                        continue;

                if (size > s->size)
                        continue;

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

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

                return s;
        }
        return NULL;
}

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

        BUG_ON(dtor);
        down_write(&slub_lock);
        s = find_mergeable(size, align, flags, ctor);
        if (s) {
                s->refcount++;
                /*
                 * Adjust the object sizes so that we clear
                 * the complete object on kzalloc.
                 */
                s->objsize = max(s->objsize, (int)size);
                s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));
                if (sysfs_slab_alias(s, name))
                        goto err;
        } else {
                s = kmalloc(kmem_size, GFP_KERNEL);
                if (s && kmem_cache_open(s, GFP_KERNEL, name,
                                size, align, flags, ctor)) {
                        if (sysfs_slab_add(s)) {
                                kfree(s);
                                goto err;
                        }
                        list_add(&s->list, &slab_caches);
                } else
                        kfree(s);
        }
        up_write(&slub_lock);
        return s;

err:
        up_write(&slub_lock);
        if (flags & SLAB_PANIC)
                panic("Cannot create slabcache %s\n", name);
        else
                s = NULL;
        return s;
}
EXPORT_SYMBOL(kmem_cache_create);

void *kmem_cache_zalloc(struct kmem_cache *s, gfp_t flags)
{
        void *x;

        x = slab_alloc(s, flags, -1, __builtin_return_address(0));
        if (x)
                memset(x, 0, s->objsize);
        return x;
}
EXPORT_SYMBOL(kmem_cache_zalloc);

#ifdef CONFIG_SMP
static void for_all_slabs(void (*func)(struct kmem_cache *, int), int cpu)
{
        struct list_head *h;

        down_read(&slub_lock);
        list_for_each(h, &slab_caches) {
                struct kmem_cache *s =
                        container_of(h, struct kmem_cache, list);

                func(s, cpu);
        }
        up_read(&slub_lock);
}

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

        switch (action) {
        case CPU_UP_CANCELED:
        case CPU_UP_CANCELED_FROZEN:
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                for_all_slabs(__flush_cpu_slab, cpu);
                break;
        default:
                break;
        }
        return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata slab_notifier =
        { &slab_cpuup_callback, NULL, 0 };

#endif

void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, void *caller)
{
        struct kmem_cache *s = get_slab(size, gfpflags);

        if (!s)
                return NULL;

        return slab_alloc(s, gfpflags, -1, caller);
}

void *__kmalloc_node_track_caller(size_t size, gfp_t gfpflags,
                                        int node, void *caller)
{
        struct kmem_cache *s = get_slab(size, gfpflags);

        if (!s)
                return NULL;

        return slab_alloc(s, gfpflags, node, caller);
}

#if defined(CONFIG_SYSFS) && defined(CONFIG_SLUB_DEBUG)
static int validate_slab(struct kmem_cache *s, struct page *page)
{
        void *p;
        void *addr = page_address(page);
        DECLARE_BITMAP(map, s->objects);

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

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

        for_each_free_object(p, s, page->freelist) {
                set_bit(slab_index(p, s, addr), map);
                if (!check_object(s, page, p, 0))
                        return 0;
        }

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

static void validate_slab_slab(struct kmem_cache *s, struct page *page)
{
        if (slab_trylock(page)) {
                validate_slab(s, page);
                slab_unlock(page);
        } else
                printk(KERN_INFO "SLUB %s: Skipped busy slab 0x%p\n",
                        s->name, page);

        if (s->flags & DEBUG_DEFAULT_FLAGS) {
                if (!SlabDebug(page))
                        printk(KERN_ERR "SLUB %s: SlabDebug not set "
                                "on slab 0x%p\n", s->name, page);
        } else {
                if (SlabDebug(page))
                        printk(KERN_ERR "SLUB %s: SlabDebug set on "
                                "slab 0x%p\n", s->name, page);
        }
}

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

        spin_lock_irqsave(&n->list_lock, flags);

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

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

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

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

static unsigned long validate_slab_cache(struct kmem_cache *s)
{
        int node;
        unsigned long count = 0;

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

                count += validate_slab_node(s, n);
        }
        return count;
}

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

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

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

        validate_slab_cache(kmalloc_caches + 4);

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

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

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

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

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

/*
 * Generate lists of code addresses where slabcache objects are allocated
 * and freed.
 */

struct location {
        unsigned long count;
        void *addr;
        long long sum_time;
        long min_time;
        long max_time;
        long min_pid;
        long max_pid;
        cpumask_t cpus;
        nodemask_t nodes;
};

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

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

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

        if (!max)
                max = PAGE_SIZE / sizeof(struct location);

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

        l = (void *)__get_free_pages(GFP_KERNEL, order);

        if (!l)
                return 0;

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

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

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

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

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

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

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

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

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

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

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

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

static void process_slab(struct loc_track *t, struct kmem_cache *s,
                struct page *page, enum track_item alloc)
{
        void *addr = page_address(page);
        DECLARE_BITMAP(map, s->objects);
        void *p;

        bitmap_zero(map, s->objects);
        for_each_free_object(p, s, page->freelist)
                set_bit(slab_index(p, s, addr), map);

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

static int list_locations(struct kmem_cache *s, char *buf,
                                        enum track_item alloc)
{
        int n = 0;
        unsigned long i;
        struct loc_track t;
        int node;

        t.count = 0;
        t.max = 0;

        /* Push back cpu slabs */
        flush_all(s);

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

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

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

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

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

                if (l->addr)
                        n += sprint_symbol(buf + n, (unsigned long)l->addr);
                else
                        n += sprintf(buf + n, "<not-available>");

                if (l->sum_time != l->min_time) {
                        unsigned long remainder;

                        n += sprintf(buf + n, " age=%ld/%ld/%ld",
                        l->min_time,
                        div_long_long_rem(l->sum_time, l->count, &remainder),
                        l->max_time);
                } else
                        n += sprintf(buf + n, " age=%ld",
                                l->min_time);

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

                if (num_online_cpus() > 1 && !cpus_empty(l->cpus)) {
                        n += sprintf(buf + n, " cpus=");
                        n += cpulist_scnprintf(buf + n, PAGE_SIZE - n - 50,
                                        l->cpus);
                }

                if (num_online_nodes() > 1 && !nodes_empty(l->nodes)) {
                        n += sprintf(buf + n, " nodes=");
                        n += nodelist_scnprintf(buf + n, PAGE_SIZE - n - 50,
                                        l->nodes);
                }

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

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

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

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

enum slab_stat_type {
        SL_FULL,
        SL_PARTIAL,
        SL_CPU,
        SL_OBJECTS
};

#define SO_FULL         (1 << SL_FULL)
#define SO_PARTIAL      (1 << SL_PARTIAL)
#define SO_CPU          (1 << SL_CPU)
#define SO_OBJECTS      (1 << SL_OBJECTS)

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

        nodes = kzalloc(2 * sizeof(unsigned long) * nr_node_ids, GFP_KERNEL);
        per_cpu = nodes + nr_node_ids;

        for_each_possible_cpu(cpu) {
                struct page *page = s->cpu_slab[cpu];
                int node;

                if (page) {
                        node = page_to_nid(page);
                        if (flags & SO_CPU) {
                                int x = 0;

                                if (flags & SO_OBJECTS)
                                        x = page->inuse;
                                else
                                        x = 1;
                                total += x;
                                nodes[node] += x;
                        }
                        per_cpu[node]++;
                }
        }

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

                if (flags & SO_PARTIAL) {
                        if (flags & SO_OBJECTS)
                                x = count_partial(n);
                        else
                                x = n->nr_partial;
                        total += x;
                        nodes[node] += x;
                }

                if (flags & SO_FULL) {
                        int full_slabs = atomic_read(&n->nr_slabs)
                                        - per_cpu[node]
                                        - n->nr_partial;

                        if (flags & SO_OBJECTS)
                                x = full_slabs * s->objects;
                        else
                                x = full_slabs;
                        total += x;
                        nodes[node] += x;
                }
        }

        x = sprintf(buf, "%lu", total);
#ifdef CONFIG_NUMA
        for_each_online_node(node)
                if (nodes[node])
                        x += sprintf(buf + x, " N%d=%lu",
                                        node, nodes[node]);
#endif
        kfree(nodes);
        return x + sprintf(buf + x, "\n");
}

static int any_slab_objects(struct kmem_cache *s)
{
        int node;
        int cpu;

        for_each_possible_cpu(cpu)
                if (s->cpu_slab[cpu])
                        return 1;

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

                if (n->nr_partial || atomic_read(&n->nr_slabs))
                        return 1;
        }
        return 0;
}

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

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

#define SLAB_ATTR_RO(_name) \
        static struct slab_attribute _name##_attr = __ATTR_RO(_name)

#define SLAB_ATTR(_name) \
        static struct slab_attribute _name##_attr =  \
        __ATTR(_name, 0644, _name##_show, _name##_store)

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

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

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

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

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

static ssize_t ctor_show(struct kmem_cache *s, char *buf)
{
        if (s->ctor) {
                int n = sprint_symbol(buf, (unsigned long)s->ctor);

                return n + sprintf(buf + n, "\n");
        }
        return 0;
}
SLAB_ATTR_RO(ctor);

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

static ssize_t slabs_show(struct kmem_cache *s, char *buf)
{
        return slab_objects(s, buf, SO_FULL|SO_PARTIAL|SO_CPU);
}
SLAB_ATTR_RO(slabs);

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

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

static ssize_t objects_show(struct kmem_cache *s, char *buf)
{
        return slab_objects(s, buf, SO_FULL|SO_PARTIAL|SO_CPU|SO_OBJECTS);
}
SLAB_ATTR_RO(objects);

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

static ssize_t validate_store(struct kmem_cache *s,
                        const char *buf, size_t length)
{
        if (buf[0] == '1')
                validate_slab_cache(s);
        else
                return -EINVAL;
        return length;
}
SLAB_ATTR(validate);

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

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

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

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

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

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

static ssize_t defrag_ratio_store(struct kmem_cache *s,
                                const char *buf, size_t length)
{
        int n = simple_strtoul(buf, NULL, 10);

        if (n < 100)
                s->defrag_ratio = n * 10;
        return length;
}
SLAB_ATTR(defrag_ratio);
#endif

static struct attribute * slab_attrs[] = {
        &slab_size_attr.attr,
        &object_size_attr.attr,
        &objs_per_slab_attr.attr,
        &order_attr.attr,
        &objects_attr.attr,
        &slabs_attr.attr,
        &partial_attr.attr,
        &cpu_slabs_attr.attr,
        &ctor_attr.attr,
        &aliases_attr.attr,
        &align_attr.attr,
        &sanity_checks_attr.attr,
        &trace_attr.attr,
        &hwcache_align_attr.attr,
        &reclaim_account_attr.attr,
        &destroy_by_rcu_attr.attr,
        &red_zone_attr.attr,
        &poison_attr.attr,
        &store_user_attr.attr,
        &validate_attr.attr,
        &shrink_attr.attr,
        &alloc_calls_attr.attr,
        &free_calls_attr.attr,
#ifdef CONFIG_ZONE_DMA
        &cache_dma_attr.attr,
#endif
#ifdef CONFIG_NUMA
        &defrag_ratio_attr.attr,
#endif
        NULL
};

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

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

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

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

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

        return err;
}

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

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

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

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

        return err;
}

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

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

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

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

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

decl_subsys(slab, &slab_ktype, &slab_uevent_ops);

#define ID_STR_LENGTH 64

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

        BUG_ON(!name);

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

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

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

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

        kobj_set_kset_s(s, slab_subsys);
        kobject_set_name(&s->kobj, name);
        kobject_init(&s->kobj);
        err = kobject_add(&s->kobj);
        if (err)
                return err;

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

static void sysfs_slab_remove(struct kmem_cache *s)
{
        kobject_uevent(&s->kobj, KOBJ_REMOVE);
        kobject_del(&s->kobj);
}

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

struct saved_alias *alias_list;

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

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

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

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

static int __init slab_sysfs_init(void)
{
        struct list_head *h;
        int err;

        err = subsystem_register(&slab_subsys);
        if (err) {
                printk(KERN_ERR "Cannot register slab subsystem.\n");
                return -ENOSYS;
        }

        slab_state = SYSFS;

        list_for_each(h, &slab_caches) {
                struct kmem_cache *s =
                        container_of(h, struct kmem_cache, list);

                err = sysfs_slab_add(s);
                BUG_ON(err);
        }

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

                alias_list = alias_list->next;
                err = sysfs_slab_alias(al->s, al->name);
                BUG_ON(err);
                kfree(al);
        }

        resiliency_test();
        return 0;
}

__initcall(slab_sysfs_init);
#endif