kmem_cache_alloc

/**
 * 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.
 *
 * Return: pointer to the new object or %NULL in case of error
 */
void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
{
    void *ret = slab_alloc(cachep, flags, _RET_IP_);

    trace_kmem_cache_alloc(_RET_IP_, ret,
                   cachep->object_size, cachep->size, flags);

    return ret;
}

static __always_inline void *
slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller)
{
    unsigned long save_flags;
    void *objp;

    flags &= gfp_allowed_mask;
    cachep = slab_pre_alloc_hook(cachep, flags);
    if (unlikely(!cachep))
        return NULL;

    cache_alloc_debugcheck_before(cachep, flags);
    local_irq_save(save_flags);
    objp = __do_cache_alloc(cachep, flags);
    local_irq_restore(save_flags);
    objp = cache_alloc_debugcheck_after(cachep, flags, objp, caller);
    prefetchw(objp);

    if (unlikely(slab_want_init_on_alloc(flags, cachep)) && objp)
        memset(objp, 0, cachep->object_size);

    slab_post_alloc_hook(cachep, flags, 1, &objp);
    return objp;
}

static __always_inline void *
__do_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
{
    return ____cache_alloc(cachep, flags);
}