Optimize andes_clear_page() and andes_copy_page() with prefetch

[linux-2.6/linux-mips.git] / mm / slab.c

/*
 * linux/mm/slab.c
 * Written by Mark Hemment, 1996/97.
 * (markhe@nextd.demon.co.uk)
 *
 * kmem_cache_destroy() + some cleanup - 1999 Andrea Arcangeli
 *
 * Major cleanup, different bufctl logic, per-cpu arrays
 *      (c) 2000 Manfred Spraul
 *
 * An implementation of the Slab Allocator as described in outline in;
 *      UNIX Internals: The New Frontiers by Uresh Vahalia
 *      Pub: Prentice Hall      ISBN 0-13-101908-2
 * or with a little more detail in;
 *      The Slab Allocator: An Object-Caching Kernel Memory Allocator
 *      Jeff Bonwick (Sun Microsystems).
 *      Presented at: USENIX Summer 1994 Technical Conference
 *
 *
 * The memory is organized in caches, one cache for each object type.
 * (e.g. inode_cache, dentry_cache, buffer_head, vm_area_struct)
 * Each cache consists out of many slabs (they are small (usually one
 * page long) and always contiguous), and each slab contains multiple
 * initialized objects.
 *
 * Each cache can only support one memory type (GFP_DMA, GFP_HIGHMEM,
 * normal). If you need a special memory type, then must create a new
 * cache for that memory type.
 *
 * In order to reduce fragmentation, the slabs are sorted in 3 groups:
 *   full slabs with 0 free objects
 *   partial slabs
 *   empty slabs with no allocated objects
 *
 * If partial slabs exist, then new allocations come from these slabs,
 * otherwise from empty slabs or new slabs are allocated.
 *
 * kmem_cache_destroy() CAN CRASH if you try to allocate from the cache
 * during kmem_cache_destroy(). The caller must prevent concurrent allocs.
 *
 * On SMP systems, each cache has a short per-cpu head array, most allocs
 * and frees go into that array, and if that array overflows, then 1/2
 * of the entries in the array are given back into the global cache.
 * This reduces the number of spinlock operations.
 *
 * The c_cpuarray can be changed with a smp_call_function call,
 * it may not be read with enabled local interrupts.
 *
 * SMP synchronization:
 *  constructors and destructors are called without any locking.
 *  Several members in kmem_cache_t and slab_t never change, they
 *      are accessed without any locking.
 *  The per-cpu arrays are never accessed from the wrong cpu, no locking.
 *      smp_call_function() is used if one cpu must flush the arrays from
 *      other cpus.
 *  The non-constant members are protected with a per-cache irq spinlock.
 *
 * Further notes from the original documentation:
 *
 * 11 April '97.  Started multi-threading - markhe
 *      The global cache-chain is protected by the semaphore 'cache_chain_sem'.
 *      The sem is only needed when accessing/extending the cache-chain, which
 *      can never happen inside an interrupt (kmem_cache_create(),
 *      kmem_cache_shrink() and kmem_cache_reap()).
 *
 *      To prevent kmem_cache_shrink() trying to shrink a 'growing' cache (which
 *      maybe be sleeping and therefore not holding the semaphore/lock), the
 *      growing field is used.  This also prevents reaping from a cache.
 *
 *      At present, each engine can be growing a cache.  This should be blocked.
 *
 */

#include        <linux/config.h>
#include        <linux/slab.h>
#include        <linux/interrupt.h>
#include        <linux/init.h>
#include        <asm/uaccess.h>

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

#define DEBUG           0
#define STATS           0
#define FORCED_DEBUG    0

/*
 * Parameters for kmem_cache_reap
 */
#define REAP_SCANLEN    10
#define REAP_PERFECT    10

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

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

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

#define BUFCTL_END 0xffffFFFF
#define SLAB_LIMIT 0xffffFFFE
typedef unsigned int kmem_bufctl_t;

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

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

#define slab_bufctl(slabp) \
        ((kmem_bufctl_t *)(((slab_t*)slabp)+1))

/*
 * cpucache_t
 *
 * Per cpu structures
 * The limit is stored in the per-cpu structure to reduce the data cache
 * footprint.
 */
typedef struct cpucache_s {
        unsigned int avail;
        unsigned int limit;
} cpucache_t;

#define cc_entry(cpucache) \
        ((void **)(((cpucache_t*)cpucache)+1))
#define cc_data(cachep) \
        ((cachep)->cpudata[smp_processor_id()])
/*
 * kmem_cache_t
 *
 * manages a cache.
 */

#define CACHE_NAMELEN   20      /* max name length for a slab cache */

struct kmem_cache_s {
/* 1) each alloc & free */
        /* full, partial first, then free */
        struct list_head        slabs;
        struct list_head        *firstnotfull;
        unsigned int            objsize;
        unsigned int            flags;  /* constant flags */
        unsigned int            num;    /* # of objs per slab */
        spinlock_t              spinlock;
#ifdef CONFIG_SMP
        unsigned int            batchcount;
#endif

/* 2) slab additions /removals */
        /* order of pgs per slab (2^n) */
        unsigned int            gfporder;

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

        size_t                  colour;         /* cache colouring range */
        unsigned int            colour_off;     /* colour offset */
        unsigned int            colour_next;    /* cache colouring */
        kmem_cache_t            *slabp_cache;
        unsigned int            growing;
        unsigned int            dflags;         /* dynamic flags */

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

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

        unsigned long           failures;

/* 3) cache creation/removal */
        char                    name[CACHE_NAMELEN];
        struct list_head        next;
#ifdef CONFIG_SMP
/* 4) per-cpu data */
        cpucache_t              *cpudata[NR_CPUS];
#endif
#if STATS
        unsigned long           num_active;
        unsigned long           num_allocations;
        unsigned long           high_mark;
        unsigned long           grown;
        unsigned long           reaped;
        unsigned long           errors;
#ifdef CONFIG_SMP
        atomic_t                allochit;
        atomic_t                allocmiss;
        atomic_t                freehit;
        atomic_t                freemiss;
#endif
#endif
};

/* internal c_flags */
#define CFLGS_OFF_SLAB  0x010000UL      /* slab management in own cache */
#define CFLGS_OPTIMIZE  0x020000UL      /* optimized slab lookup */

/* c_dflags (dynamic flags). Need to hold the spinlock to access this member */
#define DFLGS_GROWN     0x000001UL      /* don't reap a recently grown */

#define OFF_SLAB(x)     ((x)->flags & CFLGS_OFF_SLAB)
#define OPTIMIZE(x)     ((x)->flags & CFLGS_OPTIMIZE)
#define GROWN(x)        ((x)->dlags & DFLGS_GROWN)

#if STATS
#define STATS_INC_ACTIVE(x)     ((x)->num_active++)
#define STATS_DEC_ACTIVE(x)     ((x)->num_active--)
#define STATS_INC_ALLOCED(x)    ((x)->num_allocations++)
#define STATS_INC_GROWN(x)      ((x)->grown++)
#define STATS_INC_REAPED(x)     ((x)->reaped++)
#define STATS_SET_HIGH(x)       do { if ((x)->num_active > (x)->high_mark) \
                                        (x)->high_mark = (x)->num_active; \
                                } while (0)
#define STATS_INC_ERR(x)        ((x)->errors++)
#else
#define STATS_INC_ACTIVE(x)     do { } while (0)
#define STATS_DEC_ACTIVE(x)     do { } while (0)
#define STATS_INC_ALLOCED(x)    do { } while (0)
#define STATS_INC_GROWN(x)      do { } while (0)
#define STATS_INC_REAPED(x)     do { } while (0)
#define STATS_SET_HIGH(x)       do { } while (0)
#define STATS_INC_ERR(x)        do { } while (0)
#endif

#if STATS && defined(CONFIG_SMP)
#define STATS_INC_ALLOCHIT(x)   atomic_inc(&(x)->allochit)
#define STATS_INC_ALLOCMISS(x)  atomic_inc(&(x)->allocmiss)
#define STATS_INC_FREEHIT(x)    atomic_inc(&(x)->freehit)
#define STATS_INC_FREEMISS(x)   atomic_inc(&(x)->freemiss)
#else
#define STATS_INC_ALLOCHIT(x)   do { } while (0)
#define STATS_INC_ALLOCMISS(x)  do { } while (0)
#define STATS_INC_FREEHIT(x)    do { } while (0)
#define STATS_INC_FREEMISS(x)   do { } while (0)
#endif

#if DEBUG
/* Magic nums for obj red zoning.
 * Placed in the first word before and the first word after an obj.
 */
#define RED_MAGIC1      0x5A2CF071UL    /* when obj is active */
#define RED_MAGIC2      0x170FC2A5UL    /* when obj is inactive */

/* ...and for poisoning */
#define POISON_BYTE     0x5a            /* byte value for poisoning */
#define POISON_END      0xa5            /* end-byte of poisoning */

#endif

/* maximum size of an obj (in 2^order pages) */
#define MAX_OBJ_ORDER   5       /* 32 pages */

/*
 * Do not go above this order unless 0 objects fit into the slab.
 */
#define BREAK_GFP_ORDER_HI      2
#define BREAK_GFP_ORDER_LO      1
static int slab_break_gfp_order = BREAK_GFP_ORDER_LO;

/*
 * Absolute limit for the gfp order
 */
#define MAX_GFP_ORDER   5       /* 32 pages */


/* Macros for storing/retrieving the cachep and or slab from the
 * global 'mem_map'. These are used to find the slab an obj belongs to.
 * With kfree(), these are used to find the cache which an obj belongs to.
 */
#define SET_PAGE_CACHE(pg,x)  ((pg)->list.next = (struct list_head *)(x))
#define GET_PAGE_CACHE(pg)    ((kmem_cache_t *)(pg)->list.next)
#define SET_PAGE_SLAB(pg,x)   ((pg)->list.prev = (struct list_head *)(x))
#define GET_PAGE_SLAB(pg)     ((slab_t *)(pg)->list.prev)

/* Size description struct for general caches. */
typedef struct cache_sizes {
        size_t           cs_size;
        kmem_cache_t    *cs_cachep;
        kmem_cache_t    *cs_dmacachep;
} cache_sizes_t;

static cache_sizes_t cache_sizes[] = {
#if PAGE_SIZE == 4096
        {    32,        NULL, NULL},
#endif
        {    64,        NULL, NULL},
        {   128,        NULL, NULL},
        {   256,        NULL, NULL},
        {   512,        NULL, NULL},
        {  1024,        NULL, NULL},
        {  2048,        NULL, NULL},
        {  4096,        NULL, NULL},
        {  8192,        NULL, NULL},
        { 16384,        NULL, NULL},
        { 32768,        NULL, NULL},
        { 65536,        NULL, NULL},
        {131072,        NULL, NULL},
        {     0,        NULL, NULL}
};

/* internal cache of cache description objs */
static kmem_cache_t cache_cache = {
        slabs:          LIST_HEAD_INIT(cache_cache.slabs),
        firstnotfull:   &cache_cache.slabs,
        objsize:        sizeof(kmem_cache_t),
        flags:          SLAB_NO_REAP,
        spinlock:       SPIN_LOCK_UNLOCKED,
        colour_off:     L1_CACHE_BYTES,
        name:           "kmem_cache",
};

/* Guard access to the cache-chain. */
static struct semaphore cache_chain_sem;

/* Place maintainer for reaping. */
static kmem_cache_t *clock_searchp = &cache_cache;

#define cache_chain (cache_cache.next)

#ifdef CONFIG_SMP
/*
 * chicken and egg problem: delay the per-cpu array allocation
 * until the general caches are up.
 */
static int g_cpucache_up;

static void drain_cache (void *__cachep);
static void enable_cpucache (kmem_cache_t *cachep);
static void enable_all_cpucaches (void);
#endif

/* Cal the num objs, wastage, and bytes left over for a given slab size. */
static void kmem_cache_estimate (unsigned long gfporder, size_t size,
                 int flags, size_t *left_over, unsigned int *num)
{
        int i;
        size_t wastage = PAGE_SIZE<<gfporder;
        size_t extra = 0;
        size_t base = 0;

        if (!(flags & CFLGS_OFF_SLAB)) {
                base = sizeof(slab_t);
                extra = sizeof(kmem_bufctl_t);
        }
        i = 0;
        while (i*size + L1_CACHE_ALIGN(base+i*extra) <= wastage)
                i++;
        if (i > 0)
                i--;

        if (i > SLAB_LIMIT)
                i = SLAB_LIMIT;

        *num = i;
        wastage -= i*size;
        wastage -= L1_CACHE_ALIGN(base+i*extra);
        *left_over = wastage;
}

/* Initialisation - setup the `cache' cache. */
void __init kmem_cache_init(void)
{
        size_t left_over;

        init_MUTEX(&cache_chain_sem);
        INIT_LIST_HEAD(&cache_chain);

        kmem_cache_estimate(0, cache_cache.objsize, 0,
                        &left_over, &cache_cache.num);
        if (!cache_cache.num)
                BUG();

        cache_cache.colour = left_over/cache_cache.colour_off;
        cache_cache.colour_next = 0;
}


/* Initialisation - setup remaining internal and general caches.
 * Called after the gfp() functions have been enabled, and before smp_init().
 */
void __init kmem_cache_sizes_init(void)
{
        cache_sizes_t *sizes = cache_sizes;
        char name[20];
        /*
         * Fragmentation resistance on low memory - only use bigger
         * page orders on machines with more than 32MB of memory.
         */
        if (num_physpages > (32 << 20) >> PAGE_SHIFT)
                slab_break_gfp_order = BREAK_GFP_ORDER_HI;
        do {
                /* For performance, all the general caches are L1 aligned.
                 * This should be particularly beneficial on SMP boxes, as it
                 * eliminates "false sharing".
                 * Note for systems short on memory removing the alignment will
                 * allow tighter packing of the smaller caches. */
                sprintf(name,"size-%Zd",sizes->cs_size);
                if (!(sizes->cs_cachep =
                        kmem_cache_create(name, sizes->cs_size,
                                        0, SLAB_HWCACHE_ALIGN, NULL, NULL))) {
                        BUG();
                }

                /* Inc off-slab bufctl limit until the ceiling is hit. */
                if (!(OFF_SLAB(sizes->cs_cachep))) {
                        offslab_limit = sizes->cs_size-sizeof(slab_t);
                        offslab_limit /= 2;
                }
                sprintf(name, "size-%Zd(DMA)",sizes->cs_size);
                sizes->cs_dmacachep = kmem_cache_create(name, sizes->cs_size, 0,
                              SLAB_CACHE_DMA|SLAB_HWCACHE_ALIGN, NULL, NULL);
                if (!sizes->cs_dmacachep)
                        BUG();
                sizes++;
        } while (sizes->cs_size);
}

void __init kmem_cpucache_init(void)
{
#ifdef CONFIG_SMP
        g_cpucache_up = 1;
        enable_all_cpucaches();
#endif
}

/* Interface to system's page allocator. No need to hold the cache-lock.
 */
static inline void * kmem_getpages (kmem_cache_t *cachep, unsigned long flags)
{
        void    *addr;

        /*
         * If we requested dmaable memory, we will get it. Even if we
         * did not request dmaable memory, we might get it, but that
         * would be relatively rare and ignorable.
         */
        flags |= cachep->gfpflags;
        addr = (void*) __get_free_pages(flags, cachep->gfporder);
        /* Assume that now we have the pages no one else can legally
         * messes with the 'struct page's.
         * However vm_scan() might try to test the structure to see if
         * it is a named-page or buffer-page.  The members it tests are
         * of no interest here.....
         */
        return addr;
}

/* Interface to system's page release. */
static inline void kmem_freepages (kmem_cache_t *cachep, void *addr)
{
        unsigned long i = (1<<cachep->gfporder);
        struct page *page = mem_map + MAP_NR(addr);

        /* free_pages() does not clear the type bit - we do that.
         * The pages have been unlinked from their cache-slab,
         * but their 'struct page's might be accessed in
         * vm_scan(). Shouldn't be a worry.
         */
        while (i--) {
                PageClearSlab(page);
                page++;
        }
        free_pages((unsigned long)addr, cachep->gfporder);
}

#if DEBUG
static inline void kmem_poison_obj (kmem_cache_t *cachep, void *addr)
{
        int size = cachep->objsize;
        if (cachep->flags & SLAB_RED_ZONE) {
                addr += BYTES_PER_WORD;
                size -= 2*BYTES_PER_WORD;
        }
        memset(addr, POISON_BYTE, size);
        *(unsigned char *)(addr+size-1) = POISON_END;
}

static inline int kmem_check_poison_obj (kmem_cache_t *cachep, void *addr)
{
        int size = cachep->objsize;
        void *end;
        if (cachep->flags & SLAB_RED_ZONE) {
                addr += BYTES_PER_WORD;
                size -= 2*BYTES_PER_WORD;
        }
        end = memchr(addr, POISON_END, size);
        if (end != (addr+size-1))
                return 1;
        return 0;
}
#endif

/* Destroy all the objs in a slab, and release the mem back to the system.
 * Before calling the slab must have been unlinked from the cache.
 * The cache-lock is not held/needed.
 */
static void kmem_slab_destroy (kmem_cache_t *cachep, slab_t *slabp)
{
        if (cachep->dtor
#if DEBUG
                || cachep->flags & (SLAB_POISON | SLAB_RED_ZONE)
#endif
        ) {
                int i;
                for (i = 0; i < cachep->num; i++) {
                        void* objp = slabp->s_mem+cachep->objsize*i;
#if DEBUG
                        if (cachep->flags & SLAB_RED_ZONE) {
                                if (*((unsigned long*)(objp)) != RED_MAGIC1)
                                        BUG();
                                if (*((unsigned long*)(objp + cachep->objsize
                                                -BYTES_PER_WORD)) != RED_MAGIC1)
                                        BUG();
                                objp += BYTES_PER_WORD;
                        }
#endif
                        if (cachep->dtor)
                                (cachep->dtor)(objp, cachep, 0);
#if DEBUG
                        if (cachep->flags & SLAB_RED_ZONE) {
                                objp -= BYTES_PER_WORD;
                        }       
                        if ((cachep->flags & SLAB_POISON)  &&
                                kmem_check_poison_obj(cachep, objp))
                                BUG();
#endif
                }
        }

        kmem_freepages(cachep, slabp->s_mem-slabp->colouroff);
        if (OFF_SLAB(cachep))
                kmem_cache_free(cachep->slabp_cache, slabp);
}


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

        /*
         * Sanity checks... these are all serious usage bugs.
         */
        if ((!name) ||
                ((strlen(name) >= CACHE_NAMELEN - 1)) ||
                in_interrupt() ||
                (size < BYTES_PER_WORD) ||
                (size > (1<<MAX_OBJ_ORDER)*PAGE_SIZE) ||
                (dtor && !ctor) ||
                (offset < 0 || offset > size))
                        BUG();

#if DEBUG
        if ((flags & SLAB_DEBUG_INITIAL) && !ctor) {
                /* No constructor, but inital state check requested */
                printk("%sNo con, but init state check requested - %s\n", func_nm, name);
                flags &= ~SLAB_DEBUG_INITIAL;
        }

        if ((flags & SLAB_POISON) && ctor) {
                /* request for poisoning, but we can't do that with a constructor */
                printk("%sPoisoning requested, but con given - %s\n", func_nm, name);
                flags &= ~SLAB_POISON;
        }
#if FORCED_DEBUG
        if (size < (PAGE_SIZE>>3))
                /*
                 * do not red zone large object, causes severe
                 * fragmentation.
                 */
                flags |= SLAB_RED_ZONE;
        if (!ctor)
                flags |= SLAB_POISON;
#endif
#endif

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

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

        /* Check that size is in terms of words.  This is needed to avoid
         * unaligned accesses for some archs when redzoning is used, and makes
         * sure any on-slab bufctl's are also correctly aligned.
         */
        if (size & (BYTES_PER_WORD-1)) {
                size += (BYTES_PER_WORD-1);
                size &= ~(BYTES_PER_WORD-1);
                printk("%sForcing size word alignment - %s\n", func_nm, name);
        }
        
#if DEBUG
        if (flags & SLAB_RED_ZONE) {
                /*
                 * There is no point trying to honour cache alignment
                 * when redzoning.
                 */
                flags &= ~SLAB_HWCACHE_ALIGN;
                size += 2*BYTES_PER_WORD;       /* words for redzone */
        }
#endif
        align = BYTES_PER_WORD;
        if (flags & SLAB_HWCACHE_ALIGN)
                align = L1_CACHE_BYTES;

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

        if (flags & SLAB_HWCACHE_ALIGN) {
                /* Need to adjust size so that objs are cache aligned. */
                /* Small obj size, can get at least two per cache line. */
                /* FIXME: only power of 2 supported, was better */
                while (size < align/2)
                        align /= 2;
                size = (size+align-1)&(~(align-1));
        }

        /* Cal size (in pages) of slabs, and the num of objs per slab.
         * This could be made much more intelligent.  For now, try to avoid
         * using high page-orders for slabs.  When the gfp() funcs are more
         * friendly towards high-order requests, this should be changed.
         */
        do {
                unsigned int break_flag = 0;
cal_wastage:
                kmem_cache_estimate(cachep->gfporder, size, flags,
                                                &left_over, &cachep->num);
                if (break_flag)
                        break;
                if (cachep->gfporder >= MAX_GFP_ORDER)
                        break;
                if (!cachep->num)
                        goto next;
                if (flags & CFLGS_OFF_SLAB && cachep->num > offslab_limit) {
                        /* Oops, this num of objs will cause problems. */
                        cachep->gfporder--;
                        break_flag++;
                        goto cal_wastage;
                }

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

                if ((left_over*8) <= (PAGE_SIZE<<cachep->gfporder))
                        break;  /* Acceptable internal fragmentation. */
next:
                cachep->gfporder++;
        } while (1);

        if (!cachep->num) {
                printk("kmem_cache_create: couldn't create cache %s.\n", name);
                kmem_cache_free(&cache_cache, cachep);
                cachep = NULL;
                goto opps;
        }
        slab_size = L1_CACHE_ALIGN(cachep->num*sizeof(kmem_bufctl_t)+sizeof(slab_t));

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

        /* Offset must be a multiple of the alignment. */
        offset += (align-1);
        offset &= ~(align-1);
        if (!offset)
                offset = L1_CACHE_BYTES;
        cachep->colour_off = offset;
        cachep->colour = left_over/offset;

        /* init remaining fields */
        if (!cachep->gfporder && !(flags & CFLGS_OFF_SLAB))
                flags |= CFLGS_OPTIMIZE;

        cachep->flags = flags;
        cachep->gfpflags = 0;
        if (flags & SLAB_CACHE_DMA)
                cachep->gfpflags |= GFP_DMA;
        spin_lock_init(&cachep->spinlock);
        cachep->objsize = size;
        INIT_LIST_HEAD(&cachep->slabs);
        cachep->firstnotfull = &cachep->slabs;

        if (flags & CFLGS_OFF_SLAB)
                cachep->slabp_cache = kmem_find_general_cachep(slab_size,0);
        cachep->ctor = ctor;
        cachep->dtor = dtor;
        /* Copy name over so we don't have problems with unloaded modules */
        strcpy(cachep->name, name);

#ifdef CONFIG_SMP
        if (g_cpucache_up)
                enable_cpucache(cachep);
#endif
        /* Need the semaphore to access the chain. */
        down(&cache_chain_sem);
        {
                struct list_head *p;

                list_for_each(p, &cache_chain) {
                        kmem_cache_t *pc = list_entry(p, kmem_cache_t, next);

                        /* The name field is constant - no lock needed. */
                        if (!strcmp(pc->name, name))
                                BUG();
                }
        }

        /* There is no reason to lock our new cache before we
         * link it in - no one knows about it yet...
         */
        list_add(&cachep->next, &cache_chain);
        up(&cache_chain_sem);
opps:
        return cachep;
}

/*
 * This check if the kmem_cache_t pointer is chained in the cache_cache
 * list. -arca
 */
static int is_chained_kmem_cache(kmem_cache_t * cachep)
{
        struct list_head *p;
        int ret = 0;

        /* Find the cache in the chain of caches. */
        down(&cache_chain_sem);
        list_for_each(p, &cache_chain) {
                if (p == &cachep->next) {
                        ret = 1;
                        break;
                }
        }
        up(&cache_chain_sem);

        return ret;
}

static int __kmem_cache_shrink(kmem_cache_t *cachep)
{
        slab_t *slabp;
        int ret;

#ifdef CONFIG_SMP
        smp_call_function(drain_cache, cachep, 1, 1);
        local_irq_disable();
        drain_cache(cachep);
        local_irq_enable();
#endif
        spin_lock_irq(&cachep->spinlock);

        /* If the cache is growing, stop shrinking. */
        while (!cachep->growing) {
                struct list_head *p;

                p = cachep->slabs.prev;
                if (p == &cachep->slabs)
                        break;

                slabp = list_entry(cachep->slabs.prev, slab_t, list);
                if (slabp->inuse)
                        break;

                list_del(&slabp->list);
                if (cachep->firstnotfull == &slabp->list)
                        cachep->firstnotfull = &cachep->slabs;

                spin_unlock_irq(&cachep->spinlock);
                kmem_slab_destroy(cachep, slabp);
                spin_lock_irq(&cachep->spinlock);
        }
        ret = !list_empty(&cachep->slabs);
        spin_unlock_irq(&cachep->spinlock);
        return ret;
}

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

        return __kmem_cache_shrink(cachep);
}

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

        /* Find the cache in the chain of caches. */
        down(&cache_chain_sem);
        /* the chain is never empty, cache_cache is never destroyed */
        if (clock_searchp == cachep)
                clock_searchp = list_entry(cachep->next.next,
                                                kmem_cache_t, next);
        list_del(&cachep->next);
        up(&cache_chain_sem);

        if (__kmem_cache_shrink(cachep)) {
                printk(KERN_ERR "kmem_cache_destroy: Can't free all objects %p\n",
                       cachep);
                down(&cache_chain_sem);
                list_add(&cachep->next,&cache_chain);
                up(&cache_chain_sem);
                return 1;
        }
#ifdef CONFIG_SMP
        {
                int i;
                for (i = 0; i < NR_CPUS; i++)
                        kfree(cachep->cpudata[i]);
        }
#endif
        kmem_cache_free(&cache_cache, cachep);

        return 0;
}

/* Get the memory for a slab management obj. */
static inline slab_t * kmem_cache_slabmgmt (kmem_cache_t *cachep,
                        void *objp, int colour_off, int local_flags)
{
        slab_t *slabp;
        
        if (OFF_SLAB(cachep)) {
                /* Slab management obj is off-slab. */
                slabp = kmem_cache_alloc(cachep->slabp_cache, local_flags);
                if (!slabp)
                        return NULL;
        } else {
                /* FIXME: change to
                        slabp = objp
                 * if you enable OPTIMIZE
                 */
                slabp = objp+colour_off;
                colour_off += L1_CACHE_ALIGN(cachep->num *
                                sizeof(kmem_bufctl_t) + sizeof(slab_t));
        }
        slabp->inuse = 0;
        slabp->colouroff = colour_off;
        slabp->s_mem = objp+colour_off;

        return slabp;
}

static inline void kmem_cache_init_objs (kmem_cache_t * cachep,
                        slab_t * slabp, unsigned long ctor_flags)
{
        int i;

        for (i = 0; i < cachep->num; i++) {
                void* objp = slabp->s_mem+cachep->objsize*i;
#if DEBUG
                if (cachep->flags & SLAB_RED_ZONE) {
                        *((unsigned long*)(objp)) = RED_MAGIC1;
                        *((unsigned long*)(objp + cachep->objsize -
                                        BYTES_PER_WORD)) = RED_MAGIC1;
                        objp += BYTES_PER_WORD;
                }
#endif

                /*
                 * Constructors are not allowed to allocate memory from
                 * the same cache which they are a constructor for.
                 * Otherwise, deadlock. They must also be threaded.
                 */
                if (cachep->ctor)
                        cachep->ctor(objp, cachep, ctor_flags);
#if DEBUG
                if (cachep->flags & SLAB_RED_ZONE)
                        objp -= BYTES_PER_WORD;
                if (cachep->flags & SLAB_POISON)
                        /* need to poison the objs */
                        kmem_poison_obj(cachep, objp);
                if (cachep->flags & SLAB_RED_ZONE) {
                        if (*((unsigned long*)(objp)) != RED_MAGIC1)
                                BUG();
                        if (*((unsigned long*)(objp + cachep->objsize -
                                        BYTES_PER_WORD)) != RED_MAGIC1)
                                BUG();
                }
#endif
                slab_bufctl(slabp)[i] = i+1;
        }
        slab_bufctl(slabp)[i-1] = BUFCTL_END;
        slabp->free = 0;
}

/*
 * Grow (by 1) the number of slabs within a cache.  This is called by
 * kmem_cache_alloc() when there are no active objs left in a cache.
 */
static int kmem_cache_grow (kmem_cache_t * cachep, int flags)
{
        slab_t  *slabp;
        struct page     *page;
        void            *objp;
        size_t           offset;
        unsigned int     i, local_flags;
        unsigned long    ctor_flags;
        unsigned long    save_flags;

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

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

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

        /* About to mess with non-constant members - lock. */
        spin_lock_irqsave(&cachep->spinlock, save_flags);

        /* Get colour for the slab, and cal the next value. */
        offset = cachep->colour_next;
        cachep->colour_next++;
        if (cachep->colour_next >= cachep->colour)
                cachep->colour_next = 0;
        offset *= cachep->colour_off;
        cachep->dflags |= DFLGS_GROWN;

        cachep->growing++;
        spin_unlock_irqrestore(&cachep->spinlock, save_flags);

        /* A series of memory allocations for a new slab.
         * Neither the cache-chain semaphore, or cache-lock, are
         * held, but the incrementing c_growing prevents this
         * cache from being reaped or shrunk.
         * Note: The cache could be selected in for reaping in
         * kmem_cache_reap(), but when the final test is made the
         * growing value will be seen.
         */

        /* Get mem for the objs. */
        if (!(objp = kmem_getpages(cachep, flags)))
                goto failed;

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

        /* Nasty!!!!!! I hope this is OK. */
        i = 1 << cachep->gfporder;
        page = mem_map + MAP_NR(objp);
        do {
                SET_PAGE_CACHE(page, cachep);
                SET_PAGE_SLAB(page, slabp);
                PageSetSlab(page);
                page++;
        } while (--i);

        kmem_cache_init_objs(cachep, slabp, ctor_flags);

        spin_lock_irqsave(&cachep->spinlock, save_flags);
        cachep->growing--;

        /* Make slab active. */
        list_add_tail(&slabp->list,&cachep->slabs);
        if (cachep->firstnotfull == &cachep->slabs)
                cachep->firstnotfull = &slabp->list;
        STATS_INC_GROWN(cachep);
        cachep->failures = 0;

        spin_unlock_irqrestore(&cachep->spinlock, save_flags);
        return 1;
opps1:
        kmem_freepages(cachep, objp);
failed:
        spin_lock_irqsave(&cachep->spinlock, save_flags);
        cachep->growing--;
        spin_unlock_irqrestore(&cachep->spinlock, save_flags);
        return 0;
}

/*
 * Perform extra freeing checks:
 * - detect double free
 * - detect bad pointers.
 * Called with the cache-lock held.
 */

#if DEBUG
static int kmem_extra_free_checks (kmem_cache_t * cachep,
                        slab_t *slabp, void * objp)
{
        int i;
        unsigned int objnr = (objp-slabp->s_mem)/cachep->objsize;

        if (objnr >= cachep->num)
                BUG();
        if (objp != slabp->s_mem + objnr*cachep->objsize)
                BUG();

        /* Check slab's freelist to see if this obj is there. */
        for (i = slabp->free; i != BUFCTL_END; i = slab_bufctl(slabp)[i]) {
                if (i == objnr)
                        BUG();
        }
        return 0;
}
#endif

static inline void kmem_cache_alloc_head(kmem_cache_t *cachep, int flags)
{
#if DEBUG
        if (flags & SLAB_DMA) {
                if (!(cachep->gfpflags & GFP_DMA))
                        BUG();
        } else {
                if (cachep->gfpflags & GFP_DMA)
                        BUG();
        }
#endif
}

static inline void * kmem_cache_alloc_one_tail (kmem_cache_t *cachep,
                                                         slab_t *slabp)
{
        void *objp;

        STATS_INC_ALLOCED(cachep);
        STATS_INC_ACTIVE(cachep);
        STATS_SET_HIGH(cachep);

        /* get obj pointer */
        slabp->inuse++;
        objp = slabp->s_mem + slabp->free*cachep->objsize;
        slabp->free=slab_bufctl(slabp)[slabp->free];

        if (slabp->free == BUFCTL_END)
                /* slab now full: move to next slab for next alloc */
                cachep->firstnotfull = slabp->list.next;
#if DEBUG
        if (cachep->flags & SLAB_POISON)
                if (kmem_check_poison_obj(cachep, objp))
                        BUG();
        if (cachep->flags & SLAB_RED_ZONE) {
                /* Set alloc red-zone, and check old one. */
                if (xchg((unsigned long *)objp, RED_MAGIC2) !=
                                                         RED_MAGIC1)
                        BUG();
                if (xchg((unsigned long *)(objp+cachep->objsize -
                          BYTES_PER_WORD), RED_MAGIC2) != RED_MAGIC1)
                        BUG();
                objp += BYTES_PER_WORD;
        }
#endif
        return objp;
}

/*
 * Returns a ptr to an obj in the given cache.
 * caller must guarantee synchronization
 * #define for the goto optimization 8-)
 */
#define kmem_cache_alloc_one(cachep)                            \
({                                                              \
        slab_t  *slabp;                                 \
                                                                \
        /* Get slab alloc is to come from. */                   \
        {                                                       \
                struct list_head* p = cachep->firstnotfull;     \
                if (p == &cachep->slabs)                        \
                        goto alloc_new_slab;                    \
                slabp = list_entry(p,slab_t, list);     \
        }                                                       \
        kmem_cache_alloc_one_tail(cachep, slabp);               \
})

#ifdef CONFIG_SMP
void* kmem_cache_alloc_batch(kmem_cache_t* cachep, int flags)
{
        int batchcount = cachep->batchcount;
        cpucache_t* cc = cc_data(cachep);

        spin_lock(&cachep->spinlock);
        while (batchcount--) {
                /* Get slab alloc is to come from. */
                struct list_head *p = cachep->firstnotfull;
                slab_t *slabp;

                if (p == &cachep->slabs)
                        break;
                slabp = list_entry(p,slab_t, list);
                cc_entry(cc)[cc->avail++] =
                                kmem_cache_alloc_one_tail(cachep, slabp);
        }
        spin_unlock(&cachep->spinlock);

        if (cc->avail)
                return cc_entry(cc)[--cc->avail];
        return NULL;
}
#endif

static inline void * __kmem_cache_alloc (kmem_cache_t *cachep, int flags)
{
        unsigned long save_flags;
        void* objp;

        kmem_cache_alloc_head(cachep, flags);
try_again:
        local_irq_save(save_flags);
#ifdef CONFIG_SMP
        {
                cpucache_t *cc = cc_data(cachep);

                if (cc) {
                        if (cc->avail) {
                                STATS_INC_ALLOCHIT(cachep);
                                objp = cc_entry(cc)[--cc->avail];
                        } else {
                                STATS_INC_ALLOCMISS(cachep);
                                objp = kmem_cache_alloc_batch(cachep,flags);
                                if (!objp)
                                        goto alloc_new_slab_nolock;
                        }
                } else {
                        spin_lock(&cachep->spinlock);
                        objp = kmem_cache_alloc_one(cachep);
                        spin_unlock(&cachep->spinlock);
                }
        }
#else
        objp = kmem_cache_alloc_one(cachep);
#endif
        local_irq_restore(save_flags);
        return objp;
alloc_new_slab:
#ifdef CONFIG_SMP
        spin_unlock(&cachep->spinlock);
alloc_new_slab_nolock:
#endif
        local_irq_restore(save_flags);
        if (kmem_cache_grow(cachep, flags))
                /* Someone may have stolen our objs.  Doesn't matter, we'll
                 * just come back here again.
                 */
                goto try_again;
        return NULL;
}

/*
 * Release an obj back to its cache. If the obj has a constructed
 * state, it should be in this state _before_ it is released.
 * - caller is responsible for the synchronization
 */

#if DEBUG
# define CHECK_NR(nr)                                           \
        do {                                                    \
                if (nr >= max_mapnr) {                          \
                        printk(KERN_ERR "kfree: out of range ptr %lxh.\n", \
                                (unsigned long)objp);           \
                        BUG();                                  \
                } \
        } while (0)
# define CHECK_PAGE(page)                                       \
        do {                                                    \
                if (!PageSlab(page)) {                          \
                        printk(KERN_ERR "kfree: bad ptr %lxh.\n", \
                                (unsigned long)objp);           \
                        BUG();                                  \
                }                                               \
        } while (0)

#else
# define CHECK_NR(nr)   do { } while (0)
# define CHECK_PAGE(nr) do { } while (0)
#endif

static inline void kmem_cache_free_one(kmem_cache_t *cachep, void *objp)
{
        slab_t* slabp;

        CHECK_NR(MAP_NR(objp));
        CHECK_PAGE(mem_map + MAP_NR(objp));
        /* reduces memory footprint
         *
        if (OPTIMIZE(cachep))
                slabp = (void*)((unsigned long)objp&(~(PAGE_SIZE-1)));
         else
         */
        slabp = GET_PAGE_SLAB(mem_map + MAP_NR(objp));

#if DEBUG
        if (cachep->flags & SLAB_DEBUG_INITIAL)
                /* Need to call the slab's constructor so the
                 * caller can perform a verify of its state (debugging).
                 * Called without the cache-lock held.
                 */
                cachep->ctor(objp, cachep, SLAB_CTOR_CONSTRUCTOR|SLAB_CTOR_VERIFY);

        if (cachep->flags & SLAB_RED_ZONE) {
                objp -= BYTES_PER_WORD;
                if (xchg((unsigned long *)objp, RED_MAGIC1) != RED_MAGIC2)
                        /* Either write before start, or a double free. */
                        BUG();
                if (xchg((unsigned long *)(objp+cachep->objsize -
                                BYTES_PER_WORD), RED_MAGIC1) != RED_MAGIC2)
                        /* Either write past end, or a double free. */
                        BUG();
        }
        if (cachep->flags & SLAB_POISON)
                kmem_poison_obj(cachep, objp);
        if (kmem_extra_free_checks(cachep, slabp, objp))
                return;
#endif
        {
                unsigned int objnr = (objp-slabp->s_mem)/cachep->objsize;

                slab_bufctl(slabp)[objnr] = slabp->free;
                slabp->free = objnr;
        }
        STATS_DEC_ACTIVE(cachep);
        
        /* fixup slab chain */
        if (slabp->inuse-- == cachep->num)
                goto moveslab_partial;
        if (!slabp->inuse)
                goto moveslab_free;
        return;

moveslab_partial:
        /* was full.
         * Even if the page is now empty, we can set c_firstnotfull to
         * slabp: there are no partial slabs in this case
         */
        {
                struct list_head *t = cachep->firstnotfull;

                cachep->firstnotfull = &slabp->list;
                if (slabp->list.next == t)
                        return;
                list_del(&slabp->list);
                list_add_tail(&slabp->list, t);
                return;
        }
moveslab_free:
        /*
         * was partial, now empty.
         * c_firstnotfull might point to slabp
         * FIXME: optimize
         */
        {
                struct list_head *t = cachep->firstnotfull->prev;

                list_del(&slabp->list);
                list_add_tail(&slabp->list, &cachep->slabs);
                if (cachep->firstnotfull == &slabp->list)
                        cachep->firstnotfull = t->next;
                return;
        }
}

#ifdef CONFIG_SMP
static inline void __free_block (kmem_cache_t* cachep,
                                                        void** objpp, int len)
{
        for ( ; len > 0; len--, objpp++)
                kmem_cache_free_one(cachep, *objpp);
}

static void free_block (kmem_cache_t* cachep, void** objpp, int len)
{
        spin_lock(&cachep->spinlock);
        __free_block(cachep, objpp, len);
        spin_unlock(&cachep->spinlock);
}
#endif

/*
 * __kmem_cache_free
 * called with disabled ints
 */
static inline void __kmem_cache_free (kmem_cache_t *cachep, void* objp)
{
#ifdef CONFIG_SMP
        cpucache_t *cc = cc_data(cachep);

        CHECK_NR(MAP_NR(objp));
        CHECK_PAGE(mem_map + MAP_NR(objp));
        if (cc) {
                int batchcount;
                if (cc->avail < cc->limit) {
                        STATS_INC_FREEHIT(cachep);
                        cc_entry(cc)[cc->avail++] = objp;
                        return;
                }
                STATS_INC_FREEMISS(cachep);
                batchcount = cachep->batchcount;
                cc->avail -= batchcount;
                free_block(cachep,
                                        &cc_entry(cc)[cc->avail],batchcount);
                cc_entry(cc)[cc->avail++] = objp;
                return;
        } else {
                free_block(cachep, &objp, 1);
        }
#else
        kmem_cache_free_one(cachep, objp);
#endif
}

/**
 * kmem_cache_alloc - Allocate an object
 * @cachep: The cache to allocate from.
 * @flags: See kmalloc().
 *
 * Allocate an object from this cache.  The flags are only relevant
 * if the cache has no available objects.
 */
void * kmem_cache_alloc (kmem_cache_t *cachep, int flags)
{
        return __kmem_cache_alloc(cachep, flags);
}

/**
 * kmalloc - allocate memory
 * @size: how many bytes of memory are required.
 * @flags: the type of memory to allocate.
 *
 * kmalloc is the normal method of allocating memory
 * in the kernel.  The @flags argument may be one of:
 *
 * %GFP_BUFFER - XXX
 *
 * %GFP_ATOMIC - allocation will not sleep.  Use inside interrupt handlers.
 *
 * %GFP_USER - allocate memory on behalf of user.  May sleep.
 *
 * %GFP_KERNEL - allocate normal kernel ram.  May sleep.
 *
 * %GFP_NFS - has a slightly lower probability of sleeping than %GFP_KERNEL.
 * Don't use unless you're in the NFS code.
 *
 * %GFP_KSWAPD - Don't use unless you're modifying kswapd.
 */
void * kmalloc (size_t size, int flags)
{
        cache_sizes_t *csizep = cache_sizes;

        for (; csizep->cs_size; csizep++) {
                if (size > csizep->cs_size)
                        continue;
                return __kmem_cache_alloc(flags & GFP_DMA ?
                         csizep->cs_dmacachep : csizep->cs_cachep, flags);
        }
        BUG(); // too big size
        return NULL;
}

/**
 * kmem_cache_free - Deallocate an object
 * @cachep: The cache the allocation was from.
 * @objp: The previously allocated object.
 *
 * Free an object which was previously allocated from this
 * cache.
 */
void kmem_cache_free (kmem_cache_t *cachep, void *objp)
{
        unsigned long flags;
#if DEBUG
        CHECK_NR(MAP_NR(objp));
        CHECK_PAGE(mem_map + MAP_NR(objp));
        if (cachep != GET_PAGE_CACHE(mem_map + MAP_NR(objp)))
                BUG();
#endif

        local_irq_save(flags);
        __kmem_cache_free(cachep, objp);
        local_irq_restore(flags);
}

/**
 * kfree - free previously allocated memory
 * @objp: pointer returned by kmalloc.
 *
 * Don't free memory not originally allocated by kmalloc()
 * or you will run into trouble.
 */
void kfree (const void *objp)
{
        kmem_cache_t *c;
        unsigned long flags;

        if (!objp)
                return;
        local_irq_save(flags);
        CHECK_NR(MAP_NR(objp));
        CHECK_PAGE(mem_map + MAP_NR(objp));
        c = GET_PAGE_CACHE(mem_map + MAP_NR(objp));
        __kmem_cache_free(c, (void*)objp);
        local_irq_restore(flags);
}

kmem_cache_t * kmem_find_general_cachep (size_t size, int gfpflags)
{
        cache_sizes_t *csizep = cache_sizes;

        /* This function could be moved to the header file, and
         * made inline so consumers can quickly determine what
         * cache pointer they require.
         */
        for ( ; csizep->cs_size; csizep++) {
                if (size > csizep->cs_size)
                        continue;
                break;
        }
        return (gfpflags & GFP_DMA) ? csizep->cs_dmacachep : csizep->cs_cachep;
}

#ifdef CONFIG_SMP
/*
 * called with local interrupts disabled
 */
static void drain_cache (void* __cachep)
{
        kmem_cache_t *cachep = __cachep;
        cpucache_t *cc = cc_data(cachep);

        if (cc && cc->avail) {
                free_block(cachep, cc_entry(cc), cc->avail);
                cc->avail = 0;
        }
}

typedef struct ccupdate_struct_s
{
        kmem_cache_t* cachep;
        cpucache_t* new[NR_CPUS];
} ccupdate_struct_t;

/*
 * called with local interrupts disabled
 */
static void ccupdate_callback (void* __new)
{
        ccupdate_struct_t* new = __new;
        cpucache_t *old = cc_data(new->cachep);

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

/* called with cache_chain_sem acquired.  */
static int kmem_tune_cpucache (kmem_cache_t* cachep, int limit, int batchcount)
{
        ccupdate_struct_t new;
        int i;

        /*
         * These are admin-provided, so we are more graceful.
         */
        if (limit < 0)
                return -EINVAL;
        if (batchcount < 0)
                return -EINVAL;
        if (batchcount > limit)
                return -EINVAL;
        if (limit != 0 && !batchcount)
                return -EINVAL;

        memset(&new.new,0,sizeof(new.new));
        if (limit) {
                for (i = 0; i< smp_num_cpus; i++) {
                        cpucache_t* ccnew;


                        ccnew = kmalloc(sizeof(void*)*limit+
                                        sizeof(cpucache_t), GFP_KERNEL);
                        if (!ccnew)
                                goto oom;
                        ccnew->limit = limit;
                        ccnew->avail = 0;
                        new.new[cpu_logical_map(i)] = ccnew;
                }
        }
        new.cachep = cachep;
        spin_lock_irq(&cachep->spinlock);
        cachep->batchcount = batchcount;
        spin_unlock_irq(&cachep->spinlock);

        smp_call_function(ccupdate_callback,&new,1,1);
        local_irq_disable();
        ccupdate_callback(&new);
        local_irq_enable();

        for (i = 0; i < smp_num_cpus; i++) {
                cpucache_t* ccold = new.new[cpu_logical_map(i)];
                if (!ccold)
                        continue;
                local_irq_disable();
                free_block(cachep, cc_entry(ccold), ccold->avail);
                local_irq_enable();
                kfree(ccold);
        }
        return 0;
oom:
        for (i--; i >= 0; i--)
                kfree(new.new[cpu_logical_map(i)]);
        return -ENOMEM;
}

static void enable_cpucache (kmem_cache_t *cachep)
{
        int err;
        int limit;

        /* FIXME: optimize */
        if (cachep->objsize > PAGE_SIZE)
                return;
        if (cachep->objsize > 1024)
                limit = 60;
        else if (cachep->objsize > 256)
                limit = 124;
        else
                limit = 252;

        err = kmem_tune_cpucache(cachep, limit, limit/2);
        if (err)
                printk(KERN_ERR "enable_cpucache failed for %s, error %d.\n",
                                        cachep->name, -err);
}

static void enable_all_cpucaches (void)
{
        struct list_head* p;

        down(&cache_chain_sem);

        p = &cache_cache.next;
        do {
                kmem_cache_t* cachep = list_entry(p, kmem_cache_t, next);

                enable_cpucache(cachep);
                p = cachep->next.next;
        } while (p != &cache_cache.next);

        up(&cache_chain_sem);
}
#endif

/**
 * kmem_cache_reap - Reclaim memory from caches.
 * @gfp_mask: the type of memory required.
 *
 * Called from try_to_free_page().
 */
void kmem_cache_reap (int gfp_mask)
{
        slab_t *slabp;
        kmem_cache_t *searchp;
        kmem_cache_t *best_cachep;
        unsigned int best_pages;
        unsigned int best_len;
        unsigned int scan;

        if (gfp_mask & __GFP_WAIT)
                down(&cache_chain_sem);
        else
                if (down_trylock(&cache_chain_sem))
                        return;

        scan = REAP_SCANLEN;
        best_len = 0;
        best_pages = 0;
        best_cachep = NULL;
        searchp = clock_searchp;
        do {
                unsigned int pages;
                struct list_head* p;
                unsigned int full_free;

                /* It's safe to test this without holding the cache-lock. */
                if (searchp->flags & SLAB_NO_REAP)
                        goto next;
                /* FIXME: is this really a good idea? */
                if (gfp_mask & GFP_DMA) {
                        if (!(searchp->gfpflags & GFP_DMA))
                                goto next;
                } else {
                        if (searchp->gfpflags & GFP_DMA)
                                goto next;
                }
                spin_lock_irq(&searchp->spinlock);
                if (searchp->growing)
                        goto next_unlock;
                if (searchp->dflags & DFLGS_GROWN) {
                        searchp->dflags &= ~DFLGS_GROWN;
                        goto next_unlock;
                }
#ifdef CONFIG_SMP
                {
                        cpucache_t *cc = cc_data(searchp);
                        if (cc && cc->avail) {
                                __free_block(searchp, cc_entry(cc), cc->avail);
                                cc->avail = 0;
                        }
                }
#endif

                full_free = 0;
                p = searchp->slabs.prev;
                while (p != &searchp->slabs) {
                        slabp = list_entry(p, slab_t, list);
                        if (slabp->inuse)
                                break;
                        full_free++;
                        p = p->prev;
                }

                /*
                 * Try to avoid slabs with constructors and/or
                 * more than one page per slab (as it can be difficult
                 * to get high orders from gfp()).
                 */
                pages = full_free * (1<<searchp->gfporder);
                if (searchp->ctor)
                        pages = (pages*4+1)/5;
                if (searchp->gfporder)
                        pages = (pages*4+1)/5;
                if (pages > best_pages) {
                        best_cachep = searchp;
                        best_len = full_free;
                        best_pages = pages;
                        if (full_free >= REAP_PERFECT) {
                                clock_searchp = list_entry(searchp->next.next,
                                                        kmem_cache_t,next);
                                goto perfect;
                        }
                }
next_unlock:
                spin_unlock_irq(&searchp->spinlock);
next:
                searchp = list_entry(searchp->next.next,kmem_cache_t,next);
        } while (--scan && searchp != clock_searchp);

        clock_searchp = searchp;

        if (!best_cachep)
                /* couldn't find anything to reap */
                goto out;

        spin_lock_irq(&best_cachep->spinlock);
perfect:
        /* free only 80% of the free slabs */
        best_len = (best_len*4 + 1)/5;
        for (scan = 0; scan < best_len; scan++) {
                struct list_head *p;

                if (best_cachep->growing)
                        break;
                p = best_cachep->slabs.prev;
                if (p == &best_cachep->slabs)
                        break;
                slabp = list_entry(p,slab_t,list);
                if (slabp->inuse)
                        break;
                list_del(&slabp->list);
                if (best_cachep->firstnotfull == &slabp->list)
                        best_cachep->firstnotfull = &best_cachep->slabs;
                STATS_INC_REAPED(best_cachep);

                /* Safe to drop the lock. The slab is no longer linked to the
                 * cache.
                 */
                spin_unlock_irq(&best_cachep->spinlock);
                kmem_slab_destroy(best_cachep, slabp);
                spin_lock_irq(&best_cachep->spinlock);
        }
        spin_unlock_irq(&best_cachep->spinlock);
out:
        up(&cache_chain_sem);
        return;
}

#ifdef CONFIG_PROC_FS
/* /proc/slabinfo
 *      cache-name num-active-objs total-objs
 *      obj-size num-active-slabs total-slabs
 *      num-pages-per-slab
 */
#define FIXUP(t)                                \
        do {                                    \
                if (len <= off) {               \
                        off -= len;             \
                        len = 0;                \
                } else {                        \
                        if (len-off > count)    \
                                goto t;         \
                }                               \
        } while (0)

static int proc_getdata (char*page, char**start, off_t off, int count)
{
        struct list_head *p;
        int len = 0;

        /* Output format version, so at least we can change it without _too_
         * many complaints.
         */
        len += sprintf(page+len, "slabinfo - version: 1.1"
#if STATS
                                " (statistics)"
#endif
#ifdef CONFIG_SMP
                                " (SMP)"
#endif
                                "\n");
        FIXUP(got_data);

        down(&cache_chain_sem);
        p = &cache_cache.next;
        do {
                kmem_cache_t    *cachep;
                struct list_head *q;
                slab_t          *slabp;
                unsigned long   active_objs;
                unsigned long   num_objs;
                unsigned long   active_slabs = 0;
                unsigned long   num_slabs;
                cachep = list_entry(p, kmem_cache_t, next);

                spin_lock_irq(&cachep->spinlock);
                active_objs = 0;
                num_slabs = 0;
                list_for_each(q,&cachep->slabs) {
                        slabp = list_entry(q, slab_t, list);
                        active_objs += slabp->inuse;
                        num_objs += cachep->num;
                        if (slabp->inuse)
                                active_slabs++;
                        else
                                num_slabs++;
                }
                num_slabs+=active_slabs;
                num_objs = num_slabs*cachep->num;

                len += sprintf(page+len, "%-17s %6lu %6lu %6u %4lu %4lu %4u",
                        cachep->name, active_objs, num_objs, cachep->objsize,
                        active_slabs, num_slabs, (1<<cachep->gfporder));

#if STATS
                {
                        unsigned long errors = cachep->errors;
                        unsigned long high = cachep->high_mark;
                        unsigned long grown = cachep->grown;
                        unsigned long reaped = cachep->reaped;
                        unsigned long allocs = cachep->num_allocations;

                        len += sprintf(page+len, " : %6lu %7lu %5lu %4lu %4lu",
                                        high, allocs, grown, reaped, errors);
                }
#endif
#ifdef CONFIG_SMP
                {
                        unsigned int batchcount = cachep->batchcount;
                        unsigned int limit;

                        if (cc_data(cachep))
                                limit = cc_data(cachep)->limit;
                         else
                                limit = 0;
                        len += sprintf(page+len, " : %4u %4u",
                                        limit, batchcount);
                }
#endif
#if STATS && defined(CONFIG_SMP)
                {
                        unsigned long allochit = atomic_read(&cachep->allochit);
                        unsigned long allocmiss = atomic_read(&cachep->allocmiss);
                        unsigned long freehit = atomic_read(&cachep->freehit);
                        unsigned long freemiss = atomic_read(&cachep->freemiss);
                        len += sprintf(page+len, " : %6lu %6lu %6lu %6lu",
                                        allochit, allocmiss, freehit, freemiss);
                }
#endif
                len += sprintf(page+len,"\n");
                spin_unlock_irq(&cachep->spinlock);
                FIXUP(got_data_up);
                p = cachep->next.next;
        } while (p != &cache_cache.next);
got_data_up:
        up(&cache_chain_sem);

got_data:
        *start = page+off;
        return len;
}

/**
 * slabinfo_read_proc - generates /proc/slabinfo
 * @page: scratch area, one page long
 * @start: pointer to the pointer to the output buffer
 * @off: offset within /proc/slabinfo the caller is interested in
 * @count: requested len in bytes
 * @eof: eof marker
 * @data: unused
 *
 * The contents of the buffer are
 * cache-name
 * num-active-objs
 * total-objs
 * object size
 * num-active-slabs
 * total-slabs
 * num-pages-per-slab
 * + further values on SMP and with statistics enabled
 */
int slabinfo_read_proc (char *page, char **start, off_t off,
                                 int count, int *eof, void *data)
{
        int len = proc_getdata(page, start, off, count);
        len -= (*start-page);
        if (len <= count)
                *eof = 1;
        if (len>count) len = count;
        if (len<0) len = 0;
        return len;
}

#define MAX_SLABINFO_WRITE 128
/**
 * slabinfo_write_proc - SMP tuning for the slab allocator
 * @file: unused
 * @buffer: user buffer
 * @count: data len
 * @data: unused
 */
int slabinfo_write_proc (struct file *file, const char *buffer,
                                unsigned long count, void *data)
{
#ifdef CONFIG_SMP
        char kbuf[MAX_SLABINFO_WRITE], *tmp;
        int limit, batchcount, res;
        struct list_head *p;
        
        if (count > MAX_SLABINFO_WRITE)
                return -EINVAL;
        if (copy_from_user(&kbuf, buffer, count))
                return -EFAULT;

        tmp = strchr(kbuf, ' ');
        if (!tmp)
                return -EINVAL;
        *tmp = '\0';
        tmp++;
        limit = simple_strtol(tmp, &tmp, 10);
        while (*tmp == ' ')
                tmp++;
        batchcount = simple_strtol(tmp, &tmp, 10);

        /* Find the cache in the chain of caches. */
        down(&cache_chain_sem);
        res = -EINVAL;
        list_for_each(p,&cache_chain) {
                kmem_cache_t *cachep = list_entry(p, kmem_cache_t, next);

                if (!strcmp(cachep->name, kbuf)) {
                        res = kmem_tune_cpucache(cachep, limit, batchcount);
                        break;
                }
        }
        up(&cache_chain_sem);
        if (res >= 0)
                res = count;
        return res;
#else
        return -EINVAL;
#endif
}
#endif