block/blk-ioc.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/bootmem.h>	
#include <linux/slab.h>

#include "blk.h"

static struct kmem_cache *iocontext_cachep;

void get_io_context(struct io_context *ioc)
{
	BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
	atomic_long_inc(&ioc->refcount);
}
EXPORT_SYMBOL(get_io_context);

static void icq_free_icq_rcu(struct rcu_head *head)
{
	struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);

	kmem_cache_free(icq->__rcu_icq_cache, icq);
}

static void ioc_exit_icq(struct io_cq *icq)
{
	struct elevator_type *et = icq->q->elevator->type;

	if (icq->flags & ICQ_EXITED)
		return;

	if (et->ops.elevator_exit_icq_fn)
		et->ops.elevator_exit_icq_fn(icq);

	icq->flags |= ICQ_EXITED;
}

static void ioc_destroy_icq(struct io_cq *icq)
{
	struct io_context *ioc = icq->ioc;
	struct request_queue *q = icq->q;
	struct elevator_type *et = q->elevator->type;

	lockdep_assert_held(&ioc->lock);
	lockdep_assert_held(q->queue_lock);

	radix_tree_delete(&ioc->icq_tree, icq->q->id);
	hlist_del_init(&icq->ioc_node);
	list_del_init(&icq->q_node);

	if (rcu_dereference_raw(ioc->icq_hint) == icq)
		rcu_assign_pointer(ioc->icq_hint, NULL);

	ioc_exit_icq(icq);

	icq->__rcu_icq_cache = et->icq_cache;
	call_rcu(&icq->__rcu_head, icq_free_icq_rcu);
}

static void ioc_release_fn(struct work_struct *work)
{
	struct io_context *ioc = container_of(work, struct io_context,
					      release_work);
	unsigned long flags;

	spin_lock_irqsave_nested(&ioc->lock, flags, 1);

	while (!hlist_empty(&ioc->icq_list)) {
		struct io_cq *icq = hlist_entry(ioc->icq_list.first,
						struct io_cq, ioc_node);
		struct request_queue *q = icq->q;

		if (spin_trylock(q->queue_lock)) {
			ioc_destroy_icq(icq);
			spin_unlock(q->queue_lock);
		} else {
			spin_unlock_irqrestore(&ioc->lock, flags);
			cpu_relax();
			spin_lock_irqsave_nested(&ioc->lock, flags, 1);
		}
	}

	spin_unlock_irqrestore(&ioc->lock, flags);

	kmem_cache_free(iocontext_cachep, ioc);
}

void put_io_context(struct io_context *ioc)
{
	unsigned long flags;
	bool free_ioc = false;

	if (ioc == NULL)
		return;

	BUG_ON(atomic_long_read(&ioc->refcount) <= 0);

	if (atomic_long_dec_and_test(&ioc->refcount)) {
		spin_lock_irqsave(&ioc->lock, flags);
		if (!hlist_empty(&ioc->icq_list))
			schedule_work(&ioc->release_work);
		else
			free_ioc = true;
		spin_unlock_irqrestore(&ioc->lock, flags);
	}

	if (free_ioc)
		kmem_cache_free(iocontext_cachep, ioc);
}
EXPORT_SYMBOL(put_io_context);

void exit_io_context(struct task_struct *task)
{
	struct io_context *ioc;
	struct io_cq *icq;
	struct hlist_node *n;
	unsigned long flags;

	task_lock(task);
	ioc = task->io_context;
	task->io_context = NULL;
	task_unlock(task);

	if (!atomic_dec_and_test(&ioc->nr_tasks)) {
		put_io_context(ioc);
		return;
	}

retry:
	spin_lock_irqsave_nested(&ioc->lock, flags, 1);
	hlist_for_each_entry(icq, n, &ioc->icq_list, ioc_node) {
		if (icq->flags & ICQ_EXITED)
			continue;
		if (spin_trylock(icq->q->queue_lock)) {
			ioc_exit_icq(icq);
			spin_unlock(icq->q->queue_lock);
		} else {
			spin_unlock_irqrestore(&ioc->lock, flags);
			cpu_relax();
			goto retry;
		}
	}
	spin_unlock_irqrestore(&ioc->lock, flags);

	put_io_context(ioc);
}

void ioc_clear_queue(struct request_queue *q)
{
	lockdep_assert_held(q->queue_lock);

	while (!list_empty(&q->icq_list)) {
		struct io_cq *icq = list_entry(q->icq_list.next,
					       struct io_cq, q_node);
		struct io_context *ioc = icq->ioc;

		spin_lock(&ioc->lock);
		ioc_destroy_icq(icq);
		spin_unlock(&ioc->lock);
	}
}

void create_io_context_slowpath(struct task_struct *task, gfp_t gfp_flags,
				int node)
{
	struct io_context *ioc;

	ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
				    node);
	if (unlikely(!ioc))
		return;

	
	atomic_long_set(&ioc->refcount, 1);
	atomic_set(&ioc->nr_tasks, 1);
	spin_lock_init(&ioc->lock);
	INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH);
	INIT_HLIST_HEAD(&ioc->icq_list);
	INIT_WORK(&ioc->release_work, ioc_release_fn);

	task_lock(task);
	if (!task->io_context &&
	    (task == current || !(task->flags & PF_EXITING)))
		task->io_context = ioc;
	else
		kmem_cache_free(iocontext_cachep, ioc);
	task_unlock(task);
}

struct io_context *get_task_io_context(struct task_struct *task,
				       gfp_t gfp_flags, int node)
{
	struct io_context *ioc;

	might_sleep_if(gfp_flags & __GFP_WAIT);

	do {
		task_lock(task);
		ioc = task->io_context;
		if (likely(ioc)) {
			get_io_context(ioc);
			task_unlock(task);
			return ioc;
		}
		task_unlock(task);
	} while (create_io_context(task, gfp_flags, node));

	return NULL;
}
EXPORT_SYMBOL(get_task_io_context);

struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q)
{
	struct io_cq *icq;

	lockdep_assert_held(q->queue_lock);

	rcu_read_lock();
	icq = rcu_dereference(ioc->icq_hint);
	if (icq && icq->q == q)
		goto out;

	icq = radix_tree_lookup(&ioc->icq_tree, q->id);
	if (icq && icq->q == q)
		rcu_assign_pointer(ioc->icq_hint, icq);	
	else
		icq = NULL;
out:
	rcu_read_unlock();
	return icq;
}
EXPORT_SYMBOL(ioc_lookup_icq);

struct io_cq *ioc_create_icq(struct request_queue *q, gfp_t gfp_mask)
{
	struct elevator_type *et = q->elevator->type;
	struct io_context *ioc;
	struct io_cq *icq;

	
	ioc = create_io_context(current, gfp_mask, q->node);
	if (!ioc)
		return NULL;

	icq = kmem_cache_alloc_node(et->icq_cache, gfp_mask | __GFP_ZERO,
				    q->node);
	if (!icq)
		return NULL;

	if (radix_tree_preload(gfp_mask) < 0) {
		kmem_cache_free(et->icq_cache, icq);
		return NULL;
	}

	icq->ioc = ioc;
	icq->q = q;
	INIT_LIST_HEAD(&icq->q_node);
	INIT_HLIST_NODE(&icq->ioc_node);

	
	spin_lock_irq(q->queue_lock);
	spin_lock(&ioc->lock);

	if (likely(!radix_tree_insert(&ioc->icq_tree, q->id, icq))) {
		hlist_add_head(&icq->ioc_node, &ioc->icq_list);
		list_add(&icq->q_node, &q->icq_list);
		if (et->ops.elevator_init_icq_fn)
			et->ops.elevator_init_icq_fn(icq);
	} else {
		kmem_cache_free(et->icq_cache, icq);
		icq = ioc_lookup_icq(ioc, q);
		if (!icq)
			printk(KERN_ERR "cfq: icq link failed!\n");
	}

	spin_unlock(&ioc->lock);
	spin_unlock_irq(q->queue_lock);
	radix_tree_preload_end();
	return icq;
}

void ioc_set_icq_flags(struct io_context *ioc, unsigned int flags)
{
	struct io_cq *icq;
	struct hlist_node *n;

	hlist_for_each_entry(icq, n, &ioc->icq_list, ioc_node)
		icq->flags |= flags;
}

void ioc_ioprio_changed(struct io_context *ioc, int ioprio)
{
	unsigned long flags;

	spin_lock_irqsave(&ioc->lock, flags);
	ioc->ioprio = ioprio;
	ioc_set_icq_flags(ioc, ICQ_IOPRIO_CHANGED);
	spin_unlock_irqrestore(&ioc->lock, flags);
}

void ioc_cgroup_changed(struct io_context *ioc)
{
	unsigned long flags;

	spin_lock_irqsave(&ioc->lock, flags);
	ioc_set_icq_flags(ioc, ICQ_CGROUP_CHANGED);
	spin_unlock_irqrestore(&ioc->lock, flags);
}
EXPORT_SYMBOL(ioc_cgroup_changed);

unsigned icq_get_changed(struct io_cq *icq)
{
	unsigned int changed = 0;
	unsigned long flags;

	if (unlikely(icq->flags & ICQ_CHANGED_MASK)) {
		spin_lock_irqsave(&icq->ioc->lock, flags);
		changed = icq->flags & ICQ_CHANGED_MASK;
		icq->flags &= ~ICQ_CHANGED_MASK;
		spin_unlock_irqrestore(&icq->ioc->lock, flags);
	}
	return changed;
}
EXPORT_SYMBOL(icq_get_changed);

static int __init blk_ioc_init(void)
{
	iocontext_cachep = kmem_cache_create("blkdev_ioc",
			sizeof(struct io_context), 0, SLAB_PANIC, NULL);
	return 0;
}
subsys_initcall(blk_ioc_init);