[mirror_ubuntu-eoan-kernel.git] / include / linux / slab.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Written by Mark Hemment, 1996 (markhe@nextd.demon.co.uk).
 *
 * (C) SGI 2006, Christoph Lameter
 *      Cleaned up and restructured to ease the addition of alternative
 *      implementations of SLAB allocators.
 * (C) Linux Foundation 2008-2013
 *      Unified interface for all slab allocators
 */

#ifndef _LINUX_SLAB_H
#define _LINUX_SLAB_H

#include <linux/gfp.h>
#include <linux/overflow.h>
#include <linux/types.h>
#include <linux/workqueue.h>


/*
 * Flags to pass to kmem_cache_create().
 * The ones marked DEBUG are only valid if CONFIG_DEBUG_SLAB is set.
 */
/* DEBUG: Perform (expensive) checks on alloc/free */
#define SLAB_CONSISTENCY_CHECKS ((slab_flags_t __force)0x00000100U)
/* DEBUG: Red zone objs in a cache */
#define SLAB_RED_ZONE           ((slab_flags_t __force)0x00000400U)
/* DEBUG: Poison objects */
#define SLAB_POISON             ((slab_flags_t __force)0x00000800U)
/* Align objs on cache lines */
#define SLAB_HWCACHE_ALIGN      ((slab_flags_t __force)0x00002000U)
/* Use GFP_DMA memory */
#define SLAB_CACHE_DMA          ((slab_flags_t __force)0x00004000U)
/* DEBUG: Store the last owner for bug hunting */
#define SLAB_STORE_USER         ((slab_flags_t __force)0x00010000U)
/* Panic if kmem_cache_create() fails */
#define SLAB_PANIC              ((slab_flags_t __force)0x00040000U)
/*
 * SLAB_TYPESAFE_BY_RCU - **WARNING** READ THIS!
 *
 * This delays freeing the SLAB page by a grace period, it does _NOT_
 * delay object freeing. This means that if you do kmem_cache_free()
 * that memory location is free to be reused at any time. Thus it may
 * be possible to see another object there in the same RCU grace period.
 *
 * This feature only ensures the memory location backing the object
 * stays valid, the trick to using this is relying on an independent
 * object validation pass. Something like:
 *
 *  rcu_read_lock()
 * again:
 *  obj = lockless_lookup(key);
 *  if (obj) {
 *    if (!try_get_ref(obj)) // might fail for free objects
 *      goto again;
 *
 *    if (obj->key != key) { // not the object we expected
 *      put_ref(obj);
 *      goto again;
 *    }
 *  }
 *  rcu_read_unlock();
 *
 * This is useful if we need to approach a kernel structure obliquely,
 * from its address obtained without the usual locking. We can lock
 * the structure to stabilize it and check it's still at the given address,
 * only if we can be sure that the memory has not been meanwhile reused
 * for some other kind of object (which our subsystem's lock might corrupt).
 *
 * rcu_read_lock before reading the address, then rcu_read_unlock after
 * taking the spinlock within the structure expected at that address.
 *
 * Note that SLAB_TYPESAFE_BY_RCU was originally named SLAB_DESTROY_BY_RCU.
 */
/* Defer freeing slabs to RCU */
#define SLAB_TYPESAFE_BY_RCU    ((slab_flags_t __force)0x00080000U)
/* Spread some memory over cpuset */
#define SLAB_MEM_SPREAD         ((slab_flags_t __force)0x00100000U)
/* Trace allocations and frees */
#define SLAB_TRACE              ((slab_flags_t __force)0x00200000U)

/* Flag to prevent checks on free */
#ifdef CONFIG_DEBUG_OBJECTS
# define SLAB_DEBUG_OBJECTS     ((slab_flags_t __force)0x00400000U)
#else
# define SLAB_DEBUG_OBJECTS     0
#endif

/* Avoid kmemleak tracing */
#define SLAB_NOLEAKTRACE        ((slab_flags_t __force)0x00800000U)

/* Fault injection mark */
#ifdef CONFIG_FAILSLAB
# define SLAB_FAILSLAB          ((slab_flags_t __force)0x02000000U)
#else
# define SLAB_FAILSLAB          0
#endif
/* Account to memcg */
#ifdef CONFIG_MEMCG_KMEM
# define SLAB_ACCOUNT           ((slab_flags_t __force)0x04000000U)
#else
# define SLAB_ACCOUNT           0
#endif

#ifdef CONFIG_KASAN
#define SLAB_KASAN              ((slab_flags_t __force)0x08000000U)
#else
#define SLAB_KASAN              0
#endif

/* The following flags affect the page allocator grouping pages by mobility */
/* Objects are reclaimable */
#define SLAB_RECLAIM_ACCOUNT    ((slab_flags_t __force)0x00020000U)
#define SLAB_TEMPORARY          SLAB_RECLAIM_ACCOUNT    /* Objects are short-lived */
/*
 * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
 *
 * Dereferencing ZERO_SIZE_PTR will lead to a distinct access fault.
 *
 * ZERO_SIZE_PTR can be passed to kfree though in the same way that NULL can.
 * Both make kfree a no-op.
 */
#define ZERO_SIZE_PTR ((void *)16)

#define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) <= \
                                (unsigned long)ZERO_SIZE_PTR)

#include <linux/kasan.h>

struct mem_cgroup;
/*
 * struct kmem_cache related prototypes
 */
void __init kmem_cache_init(void);
bool slab_is_available(void);

extern bool usercopy_fallback;

struct kmem_cache *kmem_cache_create(const char *name, unsigned int size,
                        unsigned int align, slab_flags_t flags,
                        void (*ctor)(void *));
struct kmem_cache *kmem_cache_create_usercopy(const char *name,
                        unsigned int size, unsigned int align,
                        slab_flags_t flags,
                        unsigned int useroffset, unsigned int usersize,
                        void (*ctor)(void *));
void kmem_cache_destroy(struct kmem_cache *);
int kmem_cache_shrink(struct kmem_cache *);

void memcg_create_kmem_cache(struct mem_cgroup *, struct kmem_cache *);
void memcg_deactivate_kmem_caches(struct mem_cgroup *);
void memcg_destroy_kmem_caches(struct mem_cgroup *);

/*
 * Please use this macro to create slab caches. Simply specify the
 * name of the structure and maybe some flags that are listed above.
 *
 * The alignment of the struct determines object alignment. If you
 * f.e. add ____cacheline_aligned_in_smp to the struct declaration
 * then the objects will be properly aligned in SMP configurations.
 */
#define KMEM_CACHE(__struct, __flags)                                   \
                kmem_cache_create(#__struct, sizeof(struct __struct),   \
                        __alignof__(struct __struct), (__flags), NULL)

/*
 * To whitelist a single field for copying to/from usercopy, use this
 * macro instead for KMEM_CACHE() above.
 */
#define KMEM_CACHE_USERCOPY(__struct, __flags, __field)                 \
                kmem_cache_create_usercopy(#__struct,                   \
                        sizeof(struct __struct),                        \
                        __alignof__(struct __struct), (__flags),        \
                        offsetof(struct __struct, __field),             \
                        sizeof_field(struct __struct, __field), NULL)

/*
 * Common kmalloc functions provided by all allocators
 */
void * __must_check __krealloc(const void *, size_t, gfp_t);
void * __must_check krealloc(const void *, size_t, gfp_t);
void kfree(const void *);
void kzfree(const void *);
size_t ksize(const void *);

#ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR
void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
                        bool to_user);
#else
static inline void __check_heap_object(const void *ptr, unsigned long n,
                                       struct page *page, bool to_user) { }
#endif

/*
 * Some archs want to perform DMA into kmalloc caches and need a guaranteed
 * alignment larger than the alignment of a 64-bit integer.
 * Setting ARCH_KMALLOC_MINALIGN in arch headers allows that.
 */
#if defined(ARCH_DMA_MINALIGN) && ARCH_DMA_MINALIGN > 8
#define ARCH_KMALLOC_MINALIGN ARCH_DMA_MINALIGN
#define KMALLOC_MIN_SIZE ARCH_DMA_MINALIGN
#define KMALLOC_SHIFT_LOW ilog2(ARCH_DMA_MINALIGN)
#else
#define ARCH_KMALLOC_MINALIGN __alignof__(unsigned long long)
#endif

/*
 * Setting ARCH_SLAB_MINALIGN in arch headers allows a different alignment.
 * Intended for arches that get misalignment faults even for 64 bit integer
 * aligned buffers.
 */
#ifndef ARCH_SLAB_MINALIGN
#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
#endif

/*
 * kmalloc and friends return ARCH_KMALLOC_MINALIGN aligned
 * pointers. kmem_cache_alloc and friends return ARCH_SLAB_MINALIGN
 * aligned pointers.
 */
#define __assume_kmalloc_alignment __assume_aligned(ARCH_KMALLOC_MINALIGN)
#define __assume_slab_alignment __assume_aligned(ARCH_SLAB_MINALIGN)
#define __assume_page_alignment __assume_aligned(PAGE_SIZE)

/*
 * Kmalloc array related definitions
 */

#ifdef CONFIG_SLAB
/*
 * The largest kmalloc size supported by the SLAB allocators is
 * 32 megabyte (2^25) or the maximum allocatable page order if that is
 * less than 32 MB.
 *
 * WARNING: Its not easy to increase this value since the allocators have
 * to do various tricks to work around compiler limitations in order to
 * ensure proper constant folding.
 */
#define KMALLOC_SHIFT_HIGH      ((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
                                (MAX_ORDER + PAGE_SHIFT - 1) : 25)
#define KMALLOC_SHIFT_MAX       KMALLOC_SHIFT_HIGH
#ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW       5
#endif
#endif

#ifdef CONFIG_SLUB
/*
 * SLUB directly allocates requests fitting in to an order-1 page
 * (PAGE_SIZE*2).  Larger requests are passed to the page allocator.
 */
#define KMALLOC_SHIFT_HIGH      (PAGE_SHIFT + 1)
#define KMALLOC_SHIFT_MAX       (MAX_ORDER + PAGE_SHIFT - 1)
#ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW       3
#endif
#endif

#ifdef CONFIG_SLOB
/*
 * SLOB passes all requests larger than one page to the page allocator.
 * No kmalloc array is necessary since objects of different sizes can
 * be allocated from the same page.
 */
#define KMALLOC_SHIFT_HIGH      PAGE_SHIFT
#define KMALLOC_SHIFT_MAX       (MAX_ORDER + PAGE_SHIFT - 1)
#ifndef KMALLOC_SHIFT_LOW
#define KMALLOC_SHIFT_LOW       3
#endif
#endif

/* Maximum allocatable size */
#define KMALLOC_MAX_SIZE        (1UL << KMALLOC_SHIFT_MAX)
/* Maximum size for which we actually use a slab cache */
#define KMALLOC_MAX_CACHE_SIZE  (1UL << KMALLOC_SHIFT_HIGH)
/* Maximum order allocatable via the slab allocagtor */
#define KMALLOC_MAX_ORDER       (KMALLOC_SHIFT_MAX - PAGE_SHIFT)

/*
 * Kmalloc subsystem.
 */
#ifndef KMALLOC_MIN_SIZE
#define KMALLOC_MIN_SIZE (1 << KMALLOC_SHIFT_LOW)
#endif

/*
 * This restriction comes from byte sized index implementation.
 * Page size is normally 2^12 bytes and, in this case, if we want to use
 * byte sized index which can represent 2^8 entries, the size of the object
 * should be equal or greater to 2^12 / 2^8 = 2^4 = 16.
 * If minimum size of kmalloc is less than 16, we use it as minimum object
 * size and give up to use byte sized index.
 */
#define SLAB_OBJ_MIN_SIZE      (KMALLOC_MIN_SIZE < 16 ? \
                               (KMALLOC_MIN_SIZE) : 16)

/*
 * Whenever changing this, take care of that kmalloc_type() and
 * create_kmalloc_caches() still work as intended.
 */
enum kmalloc_cache_type {
        KMALLOC_NORMAL = 0,
        KMALLOC_RECLAIM,
#ifdef CONFIG_ZONE_DMA
        KMALLOC_DMA,
#endif
        NR_KMALLOC_TYPES
};

#ifndef CONFIG_SLOB
extern struct kmem_cache *
kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1];

static __always_inline enum kmalloc_cache_type kmalloc_type(gfp_t flags)
{
#ifdef CONFIG_ZONE_DMA
        /*
         * The most common case is KMALLOC_NORMAL, so test for it
         * with a single branch for both flags.
         */
        if (likely((flags & (__GFP_DMA | __GFP_RECLAIMABLE)) == 0))
                return KMALLOC_NORMAL;

        /*
         * At least one of the flags has to be set. If both are, __GFP_DMA
         * is more important.
         */
        return flags & __GFP_DMA ? KMALLOC_DMA : KMALLOC_RECLAIM;
#else
        return flags & __GFP_RECLAIMABLE ? KMALLOC_RECLAIM : KMALLOC_NORMAL;
#endif
}

/*
 * Figure out which kmalloc slab an allocation of a certain size
 * belongs to.
 * 0 = zero alloc
 * 1 =  65 .. 96 bytes
 * 2 = 129 .. 192 bytes
 * n = 2^(n-1)+1 .. 2^n
 */
static __always_inline unsigned int kmalloc_index(size_t size)
{
        if (!size)
                return 0;

        if (size <= KMALLOC_MIN_SIZE)
                return KMALLOC_SHIFT_LOW;

        if (KMALLOC_MIN_SIZE <= 32 && size > 64 && size <= 96)
                return 1;
        if (KMALLOC_MIN_SIZE <= 64 && size > 128 && size <= 192)
                return 2;
        if (size <=          8) return 3;
        if (size <=         16) return 4;
        if (size <=         32) return 5;
        if (size <=         64) return 6;
        if (size <=        128) return 7;
        if (size <=        256) return 8;
        if (size <=        512) return 9;
        if (size <=       1024) return 10;
        if (size <=   2 * 1024) return 11;
        if (size <=   4 * 1024) return 12;
        if (size <=   8 * 1024) return 13;
        if (size <=  16 * 1024) return 14;
        if (size <=  32 * 1024) return 15;
        if (size <=  64 * 1024) return 16;
        if (size <= 128 * 1024) return 17;
        if (size <= 256 * 1024) return 18;
        if (size <= 512 * 1024) return 19;
        if (size <= 1024 * 1024) return 20;
        if (size <=  2 * 1024 * 1024) return 21;
        if (size <=  4 * 1024 * 1024) return 22;
        if (size <=  8 * 1024 * 1024) return 23;
        if (size <=  16 * 1024 * 1024) return 24;
        if (size <=  32 * 1024 * 1024) return 25;
        if (size <=  64 * 1024 * 1024) return 26;
        BUG();

        /* Will never be reached. Needed because the compiler may complain */
        return -1;
}
#endif /* !CONFIG_SLOB */

void *__kmalloc(size_t size, gfp_t flags) __assume_kmalloc_alignment __malloc;
void *kmem_cache_alloc(struct kmem_cache *, gfp_t flags) __assume_slab_alignment __malloc;
void kmem_cache_free(struct kmem_cache *, void *);

/*
 * Bulk allocation and freeing operations. These are accelerated in an
 * allocator specific way to avoid taking locks repeatedly or building
 * metadata structures unnecessarily.
 *
 * Note that interrupts must be enabled when calling these functions.
 */
void kmem_cache_free_bulk(struct kmem_cache *, size_t, void **);
int kmem_cache_alloc_bulk(struct kmem_cache *, gfp_t, size_t, void **);

/*
 * Caller must not use kfree_bulk() on memory not originally allocated
 * by kmalloc(), because the SLOB allocator cannot handle this.
 */
static __always_inline void kfree_bulk(size_t size, void **p)
{
        kmem_cache_free_bulk(NULL, size, p);
}

#ifdef CONFIG_NUMA
void *__kmalloc_node(size_t size, gfp_t flags, int node) __assume_kmalloc_alignment __malloc;
void *kmem_cache_alloc_node(struct kmem_cache *, gfp_t flags, int node) __assume_slab_alignment __malloc;
#else
static __always_inline void *__kmalloc_node(size_t size, gfp_t flags, int node)
{
        return __kmalloc(size, flags);
}

static __always_inline void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t flags, int node)
{
        return kmem_cache_alloc(s, flags);
}
#endif

#ifdef CONFIG_TRACING
extern void *kmem_cache_alloc_trace(struct kmem_cache *, gfp_t, size_t) __assume_slab_alignment __malloc;

#ifdef CONFIG_NUMA
extern void *kmem_cache_alloc_node_trace(struct kmem_cache *s,
                                           gfp_t gfpflags,
                                           int node, size_t size) __assume_slab_alignment __malloc;
#else
static __always_inline void *
kmem_cache_alloc_node_trace(struct kmem_cache *s,
                              gfp_t gfpflags,
                              int node, size_t size)
{
        return kmem_cache_alloc_trace(s, gfpflags, size);
}
#endif /* CONFIG_NUMA */

#else /* CONFIG_TRACING */
static __always_inline void *kmem_cache_alloc_trace(struct kmem_cache *s,
                gfp_t flags, size_t size)
{
        void *ret = kmem_cache_alloc(s, flags);

        ret = kasan_kmalloc(s, ret, size, flags);
        return ret;
}

static __always_inline void *
kmem_cache_alloc_node_trace(struct kmem_cache *s,
                              gfp_t gfpflags,
                              int node, size_t size)
{
        void *ret = kmem_cache_alloc_node(s, gfpflags, node);

        ret = kasan_kmalloc(s, ret, size, gfpflags);
        return ret;
}
#endif /* CONFIG_TRACING */

extern void *kmalloc_order(size_t size, gfp_t flags, unsigned int order) __assume_page_alignment __malloc;

#ifdef CONFIG_TRACING
extern void *kmalloc_order_trace(size_t size, gfp_t flags, unsigned int order) __assume_page_alignment __malloc;
#else
static __always_inline void *
kmalloc_order_trace(size_t size, gfp_t flags, unsigned int order)
{
        return kmalloc_order(size, flags, order);
}
#endif

static __always_inline void *kmalloc_large(size_t size, gfp_t flags)
{
        unsigned int order = get_order(size);
        return kmalloc_order_trace(size, flags, order);
}

/**
 * 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
 * for objects smaller than page size in the kernel.
 *
 * The @flags argument may be one of:
 *
 * %GFP_USER - Allocate memory on behalf of user.  May sleep.
 *
 * %GFP_KERNEL - Allocate normal kernel ram.  May sleep.
 *
 * %GFP_ATOMIC - Allocation will not sleep.  May use emergency pools.
 *   For example, use this inside interrupt handlers.
 *
 * %GFP_HIGHUSER - Allocate pages from high memory.
 *
 * %GFP_NOIO - Do not do any I/O at all while trying to get memory.
 *
 * %GFP_NOFS - Do not make any fs calls while trying to get memory.
 *
 * %GFP_NOWAIT - Allocation will not sleep.
 *
 * %__GFP_THISNODE - Allocate node-local memory only.
 *
 * %GFP_DMA - Allocation suitable for DMA.
 *   Should only be used for kmalloc() caches. Otherwise, use a
 *   slab created with SLAB_DMA.
 *
 * Also it is possible to set different flags by OR'ing
 * in one or more of the following additional @flags:
 *
 * %__GFP_HIGH - This allocation has high priority and may use emergency pools.
 *
 * %__GFP_NOFAIL - Indicate that this allocation is in no way allowed to fail
 *   (think twice before using).
 *
 * %__GFP_NORETRY - If memory is not immediately available,
 *   then give up at once.
 *
 * %__GFP_NOWARN - If allocation fails, don't issue any warnings.
 *
 * %__GFP_RETRY_MAYFAIL - Try really hard to succeed the allocation but fail
 *   eventually.
 *
 * There are other flags available as well, but these are not intended
 * for general use, and so are not documented here. For a full list of
 * potential flags, always refer to linux/gfp.h.
 */
static __always_inline void *kmalloc(size_t size, gfp_t flags)
{
        if (__builtin_constant_p(size)) {
#ifndef CONFIG_SLOB
                unsigned int index;
#endif
                if (size > KMALLOC_MAX_CACHE_SIZE)
                        return kmalloc_large(size, flags);
#ifndef CONFIG_SLOB
                index = kmalloc_index(size);

                if (!index)
                        return ZERO_SIZE_PTR;

                return kmem_cache_alloc_trace(
                                kmalloc_caches[kmalloc_type(flags)][index],
                                flags, size);
#endif
        }
        return __kmalloc(size, flags);
}

/*
 * Determine size used for the nth kmalloc cache.
 * return size or 0 if a kmalloc cache for that
 * size does not exist
 */
static __always_inline unsigned int kmalloc_size(unsigned int n)
{
#ifndef CONFIG_SLOB
        if (n > 2)
                return 1U << n;

        if (n == 1 && KMALLOC_MIN_SIZE <= 32)
                return 96;

        if (n == 2 && KMALLOC_MIN_SIZE <= 64)
                return 192;
#endif
        return 0;
}

static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
{
#ifndef CONFIG_SLOB
        if (__builtin_constant_p(size) &&
                size <= KMALLOC_MAX_CACHE_SIZE) {
                unsigned int i = kmalloc_index(size);

                if (!i)
                        return ZERO_SIZE_PTR;

                return kmem_cache_alloc_node_trace(
                                kmalloc_caches[kmalloc_type(flags)][i],
                                                flags, node, size);
        }
#endif
        return __kmalloc_node(size, flags, node);
}

struct memcg_cache_array {
        struct rcu_head rcu;
        struct kmem_cache *entries[0];
};

/*
 * This is the main placeholder for memcg-related information in kmem caches.
 * Both the root cache and the child caches will have it. For the root cache,
 * this will hold a dynamically allocated array large enough to hold
 * information about the currently limited memcgs in the system. To allow the
 * array to be accessed without taking any locks, on relocation we free the old
 * version only after a grace period.
 *
 * Root and child caches hold different metadata.
 *
 * @root_cache: Common to root and child caches.  NULL for root, pointer to
 *              the root cache for children.
 *
 * The following fields are specific to root caches.
 *
 * @memcg_caches: kmemcg ID indexed table of child caches.  This table is
 *              used to index child cachces during allocation and cleared
 *              early during shutdown.
 *
 * @root_caches_node: List node for slab_root_caches list.
 *
 * @children:   List of all child caches.  While the child caches are also
 *              reachable through @memcg_caches, a child cache remains on
 *              this list until it is actually destroyed.
 *
 * The following fields are specific to child caches.
 *
 * @memcg:      Pointer to the memcg this cache belongs to.
 *
 * @children_node: List node for @root_cache->children list.
 *
 * @kmem_caches_node: List node for @memcg->kmem_caches list.
 */
struct memcg_cache_params {
        struct kmem_cache *root_cache;
        union {
                struct {
                        struct memcg_cache_array __rcu *memcg_caches;
                        struct list_head __root_caches_node;
                        struct list_head children;
                        bool dying;
                };
                struct {
                        struct mem_cgroup *memcg;
                        struct list_head children_node;
                        struct list_head kmem_caches_node;

                        void (*deact_fn)(struct kmem_cache *);
                        union {
                                struct rcu_head deact_rcu_head;
                                struct work_struct deact_work;
                        };
                };
        };
};

int memcg_update_all_caches(int num_memcgs);

/**
 * kmalloc_array - allocate memory for an array.
 * @n: number of elements.
 * @size: element size.
 * @flags: the type of memory to allocate (see kmalloc).
 */
static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
{
        size_t bytes;

        if (unlikely(check_mul_overflow(n, size, &bytes)))
                return NULL;
        if (__builtin_constant_p(n) && __builtin_constant_p(size))
                return kmalloc(bytes, flags);
        return __kmalloc(bytes, flags);
}

/**
 * kcalloc - allocate memory for an array. The memory is set to zero.
 * @n: number of elements.
 * @size: element size.
 * @flags: the type of memory to allocate (see kmalloc).
 */
static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
{
        return kmalloc_array(n, size, flags | __GFP_ZERO);
}

/*
 * kmalloc_track_caller is a special version of kmalloc that records the
 * calling function of the routine calling it for slab leak tracking instead
 * of just the calling function (confusing, eh?).
 * It's useful when the call to kmalloc comes from a widely-used standard
 * allocator where we care about the real place the memory allocation
 * request comes from.
 */
extern void *__kmalloc_track_caller(size_t, gfp_t, unsigned long);
#define kmalloc_track_caller(size, flags) \
        __kmalloc_track_caller(size, flags, _RET_IP_)

static inline void *kmalloc_array_node(size_t n, size_t size, gfp_t flags,
                                       int node)
{
        size_t bytes;

        if (unlikely(check_mul_overflow(n, size, &bytes)))
                return NULL;
        if (__builtin_constant_p(n) && __builtin_constant_p(size))
                return kmalloc_node(bytes, flags, node);
        return __kmalloc_node(bytes, flags, node);
}

static inline void *kcalloc_node(size_t n, size_t size, gfp_t flags, int node)
{
        return kmalloc_array_node(n, size, flags | __GFP_ZERO, node);
}


#ifdef CONFIG_NUMA
extern void *__kmalloc_node_track_caller(size_t, gfp_t, int, unsigned long);
#define kmalloc_node_track_caller(size, flags, node) \
        __kmalloc_node_track_caller(size, flags, node, \
                        _RET_IP_)

#else /* CONFIG_NUMA */

#define kmalloc_node_track_caller(size, flags, node) \
        kmalloc_track_caller(size, flags)

#endif /* CONFIG_NUMA */

/*
 * Shortcuts
 */
static inline void *kmem_cache_zalloc(struct kmem_cache *k, gfp_t flags)
{
        return kmem_cache_alloc(k, flags | __GFP_ZERO);
}

/**
 * kzalloc - allocate memory. The memory is set to zero.
 * @size: how many bytes of memory are required.
 * @flags: the type of memory to allocate (see kmalloc).
 */
static inline void *kzalloc(size_t size, gfp_t flags)
{
        return kmalloc(size, flags | __GFP_ZERO);
}

/**
 * kzalloc_node - allocate zeroed memory from a particular memory node.
 * @size: how many bytes of memory are required.
 * @flags: the type of memory to allocate (see kmalloc).
 * @node: memory node from which to allocate
 */
static inline void *kzalloc_node(size_t size, gfp_t flags, int node)
{
        return kmalloc_node(size, flags | __GFP_ZERO, node);
}

unsigned int kmem_cache_size(struct kmem_cache *s);
void __init kmem_cache_init_late(void);

#if defined(CONFIG_SMP) && defined(CONFIG_SLAB)
int slab_prepare_cpu(unsigned int cpu);
int slab_dead_cpu(unsigned int cpu);
#else
#define slab_prepare_cpu        NULL
#define slab_dead_cpu           NULL
#endif

#endif  /* _LINUX_SLAB_H */