kmem_cache_alloc()

kmem_cache_alloc() is invoked to obtain objects from a specific cache. Like all malloc functions, it yields either a pointer to the reserved memory area or a null pointer if allocation fails. The function requires two parameters — the cache from which the object is to be obtained and a flag variable to accurately describe the allocation characteristics.

/**
 * 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(struct kmem_cache *cachep, gfp_t flags)
{
    void *ret = __cache_alloc(cachep, flags, __builtin_return_address(0));

    trace_kmem_cache_alloc(_RET_IP_, ret,
             obj_size(cachep), cachep->buffer_size, flags);

    return ret;
}

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

    flags &= gfp_allowed_mask;

    lockdep_trace_alloc(flags);

    if (slab_should_failslab(cachep, flags))
        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);
    kmemleak_alloc_recursive(objp, obj_size(cachep), 1, cachep->flags,
                 flags);
    prefetchw(objp);

    if (likely(objp))
        kmemcheck_slab_alloc(cachep, flags, objp, obj_size(cachep));

    if (unlikely((flags & __GFP_ZERO) && objp))
        memset(objp, 0, obj_size(cachep));

    return objp;
}