cfq-iosched.c

		 * other queues with pending requests
		 */
		if (!cfqd->busy_queues) {
			cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);
			add_timer(&cfqd->idle_slice_timer);
			goto out_cont;
		}

		/*
		 * not expired and it has a request pending, let it dispatch
		 */
		if (!RB_EMPTY(&cfqq->sort_list)) {
			cfq_mark_cfqq_must_dispatch(cfqq);
			goto out_kick;
		}
	}
expire:
	cfq_slice_expired(cfqd, 0);
out_kick:
	cfq_schedule_dispatch(cfqd);
out_cont:
	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}

/*
 * Timer running if an idle class queue is waiting for service
 */
static void cfq_idle_class_timer(unsigned long data)
{
	struct cfq_data *cfqd = (struct cfq_data *) data;
	unsigned long flags, end;

	spin_lock_irqsave(cfqd->queue->queue_lock, flags);

	/*
	 * race with a non-idle queue, reset timer
	 */
	end = cfqd->last_end_request + CFQ_IDLE_GRACE;
	if (!time_after_eq(jiffies, end)) {
		cfqd->idle_class_timer.expires = end;
		add_timer(&cfqd->idle_class_timer);
	} else
		cfq_schedule_dispatch(cfqd);

	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}

static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
{
	del_timer_sync(&cfqd->idle_slice_timer);
	del_timer_sync(&cfqd->idle_class_timer);
	blk_sync_queue(cfqd->queue);
}

static void cfq_put_cfqd(struct cfq_data *cfqd)
{
	request_queue_t *q = cfqd->queue;

	if (!atomic_dec_and_test(&cfqd->ref))
		return;

	cfq_shutdown_timer_wq(cfqd);
	blk_put_queue(q);

	mempool_destroy(cfqd->crq_pool);
	kfree(cfqd->crq_hash);
	kfree(cfqd->cfq_hash);
	kfree(cfqd);
}

static void cfq_exit_queue(elevator_t *e)
{
	struct cfq_data *cfqd = e->elevator_data;

	cfq_shutdown_timer_wq(cfqd);
	cfq_put_cfqd(cfqd);
}

static int cfq_init_queue(request_queue_t *q, elevator_t *e)
{
	struct cfq_data *cfqd;
	int i;

	cfqd = kmalloc(sizeof(*cfqd), GFP_KERNEL);
	if (!cfqd)
		return -ENOMEM;

	memset(cfqd, 0, sizeof(*cfqd));

	for (i = 0; i < CFQ_PRIO_LISTS; i++)
		INIT_LIST_HEAD(&cfqd->rr_list[i]);

	INIT_LIST_HEAD(&cfqd->busy_rr);
	INIT_LIST_HEAD(&cfqd->cur_rr);
	INIT_LIST_HEAD(&cfqd->idle_rr);
	INIT_LIST_HEAD(&cfqd->empty_list);

	cfqd->crq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_MHASH_ENTRIES, GFP_KERNEL);
	if (!cfqd->crq_hash)
		goto out_crqhash;

	cfqd->cfq_hash = kmalloc(sizeof(struct hlist_head) * CFQ_QHASH_ENTRIES, GFP_KERNEL);
	if (!cfqd->cfq_hash)
		goto out_cfqhash;

	cfqd->crq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, crq_pool);
	if (!cfqd->crq_pool)
		goto out_crqpool;

	for (i = 0; i < CFQ_MHASH_ENTRIES; i++)
		INIT_HLIST_HEAD(&cfqd->crq_hash[i]);
	for (i = 0; i < CFQ_QHASH_ENTRIES; i++)
		INIT_HLIST_HEAD(&cfqd->cfq_hash[i]);

	e->elevator_data = cfqd;

	cfqd->queue = q;
	atomic_inc(&q->refcnt);

	cfqd->max_queued = q->nr_requests / 4;
	q->nr_batching = cfq_queued;

	init_timer(&cfqd->idle_slice_timer);
	cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
	cfqd->idle_slice_timer.data = (unsigned long) cfqd;

	init_timer(&cfqd->idle_class_timer);
	cfqd->idle_class_timer.function = cfq_idle_class_timer;
	cfqd->idle_class_timer.data = (unsigned long) cfqd;

	INIT_WORK(&cfqd->unplug_work, cfq_kick_queue, q);

	atomic_set(&cfqd->ref, 1);

	cfqd->cfq_queued = cfq_queued;
	cfqd->cfq_quantum = cfq_quantum;
	cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
	cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
	cfqd->cfq_back_max = cfq_back_max;
	cfqd->cfq_back_penalty = cfq_back_penalty;
	cfqd->cfq_slice[0] = cfq_slice_async;
	cfqd->cfq_slice[1] = cfq_slice_sync;
	cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
	cfqd->cfq_slice_idle = cfq_slice_idle;
	cfqd->cfq_max_depth = cfq_max_depth;

	return 0;
out_crqpool:
	kfree(cfqd->cfq_hash);
out_cfqhash:
	kfree(cfqd->crq_hash);
out_crqhash:
	kfree(cfqd);
	return -ENOMEM;
}

static void cfq_slab_kill(void)
{
	if (crq_pool)
		kmem_cache_destroy(crq_pool);
	if (cfq_pool)
		kmem_cache_destroy(cfq_pool);
	if (cfq_ioc_pool)
		kmem_cache_destroy(cfq_ioc_pool);
}

static int __init cfq_slab_setup(void)
{
	crq_pool = kmem_cache_create("crq_pool", sizeof(struct cfq_rq), 0, 0,
					NULL, NULL);
	if (!crq_pool)
		goto fail;

	cfq_pool = kmem_cache_create("cfq_pool", sizeof(struct cfq_queue), 0, 0,
					NULL, NULL);
	if (!cfq_pool)
		goto fail;

	cfq_ioc_pool = kmem_cache_create("cfq_ioc_pool",
			sizeof(struct cfq_io_context), 0, 0, NULL, NULL);
	if (!cfq_ioc_pool)
		goto fail;

	return 0;
fail:
	cfq_slab_kill();
	return -ENOMEM;
}

/*
 * sysfs parts below -->
 */
struct cfq_fs_entry {
	struct attribute attr;
	ssize_t (*show)(struct cfq_data *, char *);
	ssize_t (*store)(struct cfq_data *, const char *, size_t);
};

static ssize_t
cfq_var_show(unsigned int var, char *page)
{
	return sprintf(page, "%d\n", var);
}

static ssize_t
cfq_var_store(unsigned int *var, const char *page, size_t count)
{
	char *p = (char *) page;

	*var = simple_strtoul(p, &p, 10);
	return count;
}

#define SHOW_FUNCTION(__FUNC, __VAR, __CONV)				\
static ssize_t __FUNC(struct cfq_data *cfqd, char *page)		\
{									\
	unsigned int __data = __VAR;					\
	if (__CONV)							\
		__data = jiffies_to_msecs(__data);			\
	return cfq_var_show(__data, (page));				\
}
SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
SHOW_FUNCTION(cfq_queued_show, cfqd->cfq_queued, 0);
SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
SHOW_FUNCTION(cfq_back_max_show, cfqd->cfq_back_max, 0);
SHOW_FUNCTION(cfq_back_penalty_show, cfqd->cfq_back_penalty, 0);
SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
SHOW_FUNCTION(cfq_max_depth_show, cfqd->cfq_max_depth, 0);
#undef SHOW_FUNCTION

#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV)			\
static ssize_t __FUNC(struct cfq_data *cfqd, const char *page, size_t count)	\
{									\
	unsigned int __data;						\
	int ret = cfq_var_store(&__data, (page), count);		\
	if (__data < (MIN))						\
		__data = (MIN);						\
	else if (__data > (MAX))					\
		__data = (MAX);						\
	if (__CONV)							\
		*(__PTR) = msecs_to_jiffies(__data);			\
	else								\
		*(__PTR) = __data;					\
	return ret;							\
}
STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
STORE_FUNCTION(cfq_queued_store, &cfqd->cfq_queued, 1, UINT_MAX, 0);
STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_back_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
STORE_FUNCTION(cfq_back_penalty_store, &cfqd->cfq_back_penalty, 1, UINT_MAX, 0);
STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0);
STORE_FUNCTION(cfq_max_depth_store, &cfqd->cfq_max_depth, 1, UINT_MAX, 0);
#undef STORE_FUNCTION

static struct cfq_fs_entry cfq_quantum_entry = {
	.attr = {.name = "quantum", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_quantum_show,
	.store = cfq_quantum_store,
};
static struct cfq_fs_entry cfq_queued_entry = {
	.attr = {.name = "queued", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_queued_show,
	.store = cfq_queued_store,
};
static struct cfq_fs_entry cfq_fifo_expire_sync_entry = {
	.attr = {.name = "fifo_expire_sync", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_fifo_expire_sync_show,
	.store = cfq_fifo_expire_sync_store,
};
static struct cfq_fs_entry cfq_fifo_expire_async_entry = {
	.attr = {.name = "fifo_expire_async", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_fifo_expire_async_show,
	.store = cfq_fifo_expire_async_store,
};
static struct cfq_fs_entry cfq_back_max_entry = {
	.attr = {.name = "back_seek_max", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_back_max_show,
	.store = cfq_back_max_store,
};
static struct cfq_fs_entry cfq_back_penalty_entry = {
	.attr = {.name = "back_seek_penalty", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_back_penalty_show,
	.store = cfq_back_penalty_store,
};
static struct cfq_fs_entry cfq_slice_sync_entry = {
	.attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_slice_sync_show,
	.store = cfq_slice_sync_store,
};
static struct cfq_fs_entry cfq_slice_async_entry = {
	.attr = {.name = "slice_async", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_slice_async_show,
	.store = cfq_slice_async_store,
};
static struct cfq_fs_entry cfq_slice_async_rq_entry = {
	.attr = {.name = "slice_async_rq", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_slice_async_rq_show,
	.store = cfq_slice_async_rq_store,
};
static struct cfq_fs_entry cfq_slice_idle_entry = {
	.attr = {.name = "slice_idle", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_slice_idle_show,
	.store = cfq_slice_idle_store,
};
static struct cfq_fs_entry cfq_max_depth_entry = {
	.attr = {.name = "max_depth", .mode = S_IRUGO | S_IWUSR },
	.show = cfq_max_depth_show,
	.store = cfq_max_depth_store,
};

static struct attribute *default_attrs[] = {
	&cfq_quantum_entry.attr,
	&cfq_queued_entry.attr,
	&cfq_fifo_expire_sync_entry.attr,
	&cfq_fifo_expire_async_entry.attr,
	&cfq_back_max_entry.attr,
	&cfq_back_penalty_entry.attr,
	&cfq_slice_sync_entry.attr,
	&cfq_slice_async_entry.attr,
	&cfq_slice_async_rq_entry.attr,
	&cfq_slice_idle_entry.attr,
	&cfq_max_depth_entry.attr,
	NULL,
};

#define to_cfq(atr) container_of((atr), struct cfq_fs_entry, attr)

static ssize_t
cfq_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
{
	elevator_t *e = container_of(kobj, elevator_t, kobj);
	struct cfq_fs_entry *entry = to_cfq(attr);

	if (!entry->show)
		return -EIO;

	return entry->show(e->elevator_data, page);
}

static ssize_t
cfq_attr_store(struct kobject *kobj, struct attribute *attr,
	       const char *page, size_t length)
{
	elevator_t *e = container_of(kobj, elevator_t, kobj);
	struct cfq_fs_entry *entry = to_cfq(attr);

	if (!entry->store)
		return -EIO;

	return entry->store(e->elevator_data, page, length);
}

static struct sysfs_ops cfq_sysfs_ops = {
	.show	= cfq_attr_show,
	.store	= cfq_attr_store,
};

static struct kobj_type cfq_ktype = {
	.sysfs_ops	= &cfq_sysfs_ops,
	.default_attrs	= default_attrs,
};

static struct elevator_type iosched_cfq = {
	.ops = {
		.elevator_merge_fn = 		cfq_merge,
		.elevator_merged_fn =		cfq_merged_request,
		.elevator_merge_req_fn =	cfq_merged_requests,
		.elevator_dispatch_fn =		cfq_dispatch_requests,
		.elevator_add_req_fn =		cfq_insert_request,
		.elevator_activate_req_fn =	cfq_activate_request,
		.elevator_deactivate_req_fn =	cfq_deactivate_request,
		.elevator_queue_empty_fn =	cfq_queue_empty,
		.elevator_completed_req_fn =	cfq_completed_request,
		.elevator_former_req_fn =	cfq_former_request,
		.elevator_latter_req_fn =	cfq_latter_request,
		.elevator_set_req_fn =		cfq_set_request,
		.elevator_put_req_fn =		cfq_put_request,
		.elevator_may_queue_fn =	cfq_may_queue,
		.elevator_init_fn =		cfq_init_queue,
		.elevator_exit_fn =		cfq_exit_queue,
	},
	.elevator_ktype =	&cfq_ktype,
	.elevator_name =	"cfq",
	.elevator_owner =	THIS_MODULE,
};

static int __init cfq_init(void)
{
	int ret;

	/*
	 * could be 0 on HZ < 1000 setups
	 */
	if (!cfq_slice_async)
		cfq_slice_async = 1;
	if (!cfq_slice_idle)
		cfq_slice_idle = 1;

	if (cfq_slab_setup())
		return -ENOMEM;

	ret = elv_register(&iosched_cfq);
	if (ret)
		cfq_slab_kill();

	return ret;
}

static void __exit cfq_exit(void)
{
	elv_unregister(&iosched_cfq);
	cfq_slab_kill();
}

module_init(cfq_init);
module_exit(cfq_exit);

MODULE_AUTHOR("Jens Axboe");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");