slab_common.c

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/*
 * Slab allocator functions that are independent of the allocator strategy
 *
 * (C) 2012 Christoph Lameter <[email protected]>
 */
#include <linux/slab.h>

#include <linux/mm.h>
#include <linux/poison.h>
#include <linux/interrupt.h>
#include <linux/memory.h>
#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/page.h>

#include "slab.h"

enum slab_state slab_state;
LIST_HEAD(slab_caches);
DEFINE_MUTEX(slab_mutex);
struct kmem_cache *kmem_cache;

#ifdef CONFIG_DEBUG_VM
static int kmem_cache_sanity_check(const char *name, size_t size)
{
    struct kmem_cache *s = NULL;

    if (!name || in_interrupt() || size < sizeof(void *) ||
        size > KMALLOC_MAX_SIZE) {
        pr_err("kmem_cache_create(%s) integrity check failed\n", name);
        return -EINVAL;
    }

    list_for_each_entry(s, &slab_caches, list) {
        char tmp;
        int res;

        /*
         * This happens when the module gets unloaded and doesn't
         * destroy its slab cache and no-one else reuses the vmalloc
         * area of the module.  Print a warning.
         */
        res = probe_kernel_address(s->name, tmp);
        if (res) {
            pr_err("Slab cache with size %d has lost its name\n",
                   s->object_size);
            continue;
        }

        if (!strcmp(s->name, name)) {
            pr_err("%s (%s): Cache name already exists.\n",
                   __func__, name);
            dump_stack();
            s = NULL;
            return -EINVAL;
        }
    }

    WARN_ON(strchr(name, ' ')); /* It confuses parsers */
    return 0;
}
#else
static inline int kmem_cache_sanity_check(const char *name, size_t size)
{
    return 0;
}
#endif

/*
 * 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.
 * @align: The required alignment for the objects.
 * @flags: SLAB flags
 * @ctor: A constructor for the objects.
 *
 * Returns a ptr to the cache on success, NULL on failure.
 * Cannot be called within a interrupt, but can be interrupted.
 * The @ctor is run when new pages are allocated by the cache.
 *
 * 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_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.
 */

struct kmem_cache *kmem_cache_create(const char *name, size_t size, size_t align,
        unsigned long flags, void (*ctor)(void *))
{
    struct kmem_cache *s = NULL;
    int err = 0;

    get_online_cpus();
    mutex_lock(&slab_mutex);

    if (!kmem_cache_sanity_check(name, size) == 0)
        goto out_locked;


    s = __kmem_cache_alias(name, size, align, flags, ctor);
    if (s)
        goto out_locked;

    s = kmem_cache_zalloc(kmem_cache, GFP_KERNEL);
    if (s) {
        s->object_size = s->size = size;
        s->align = align;
        s->ctor = ctor;
        s->name = kstrdup(name, GFP_KERNEL);
        if (!s->name) {
            kmem_cache_free(kmem_cache, s);
            err = -ENOMEM;
            goto out_locked;
        }

        err = __kmem_cache_create(s, flags);
        if (!err) {

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

        } else {
            kfree(s->name);
            kmem_cache_free(kmem_cache, s);
        }
    } else
        err = -ENOMEM;

out_locked:
    mutex_unlock(&slab_mutex);
    put_online_cpus();

    if (err) {

        if (flags & SLAB_PANIC)
            panic("kmem_cache_create: Failed to create slab '%s'. Error %d\n",
                name, err);
        else {
            printk(KERN_WARNING "kmem_cache_create(%s) failed with error %d",
                name, err);
            dump_stack();
        }

        return NULL;
    }

    return s;
}
EXPORT_SYMBOL(kmem_cache_create);

void kmem_cache_destroy(struct kmem_cache *s)
{
    get_online_cpus();
    mutex_lock(&slab_mutex);
    s->refcount--;
    if (!s->refcount) {
        list_del(&s->list);

        if (!__kmem_cache_shutdown(s)) {
            mutex_unlock(&slab_mutex);
            if (s->flags & SLAB_DESTROY_BY_RCU)
                rcu_barrier();

            kfree(s->name);
            kmem_cache_free(kmem_cache, s);
        } else {
            list_add(&s->list, &slab_caches);
            mutex_unlock(&slab_mutex);
            printk(KERN_ERR "kmem_cache_destroy %s: Slab cache still has objects\n",
                s->name);
            dump_stack();
        }
    } else {
        mutex_unlock(&slab_mutex);
    }
    put_online_cpus();
}
EXPORT_SYMBOL(kmem_cache_destroy);

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