}
EXPORT_SYMBOL(get_io_context);
-/*
- * Releasing ioc may nest into another put_io_context() leading to nested
- * fast path release. As the ioc's can't be the same, this is okay but
- * makes lockdep whine. Keep track of nesting and use it as subclass.
- */
-#ifdef CONFIG_LOCKDEP
-#define ioc_release_depth(q) ((q) ? (q)->ioc_release_depth : 0)
-#define ioc_release_depth_inc(q) (q)->ioc_release_depth++
-#define ioc_release_depth_dec(q) (q)->ioc_release_depth--
-#else
-#define ioc_release_depth(q) 0
-#define ioc_release_depth_inc(q) do { } while (0)
-#define ioc_release_depth_dec(q) do { } while (0)
-#endif
-
static void icq_free_icq_rcu(struct rcu_head *head)
{
struct io_cq *icq = container_of(head, struct io_cq, __rcu_head);
if (rcu_dereference_raw(ioc->icq_hint) == icq)
rcu_assign_pointer(ioc->icq_hint, NULL);
- if (et->ops.elevator_exit_icq_fn) {
- ioc_release_depth_inc(q);
+ if (et->ops.elevator_exit_icq_fn)
et->ops.elevator_exit_icq_fn(icq);
- ioc_release_depth_dec(q);
- }
/*
* @icq->q might have gone away by the time RCU callback runs
struct io_context *ioc = container_of(work, struct io_context,
release_work);
struct request_queue *last_q = NULL;
+ unsigned long flags;
- spin_lock_irq(&ioc->lock);
+ /*
+ * Exiting icq may call into put_io_context() through elevator
+ * which will trigger lockdep warning. The ioc's are guaranteed to
+ * be different, use a different locking subclass here. Use
+ * irqsave variant as there's no spin_lock_irq_nested().
+ */
+ spin_lock_irqsave_nested(&ioc->lock, flags, 1);
while (!hlist_empty(&ioc->icq_list)) {
struct io_cq *icq = hlist_entry(ioc->icq_list.first,
*/
if (last_q) {
spin_unlock(last_q->queue_lock);
- spin_unlock_irq(&ioc->lock);
+ spin_unlock_irqrestore(&ioc->lock, flags);
blk_put_queue(last_q);
} else {
- spin_unlock_irq(&ioc->lock);
+ spin_unlock_irqrestore(&ioc->lock, flags);
}
last_q = this_q;
- spin_lock_irq(this_q->queue_lock);
- spin_lock(&ioc->lock);
+ spin_lock_irqsave(this_q->queue_lock, flags);
+ spin_lock_nested(&ioc->lock, 1);
continue;
}
ioc_exit_icq(icq);
if (last_q) {
spin_unlock(last_q->queue_lock);
- spin_unlock_irq(&ioc->lock);
+ spin_unlock_irqrestore(&ioc->lock, flags);
blk_put_queue(last_q);
} else {
- spin_unlock_irq(&ioc->lock);
+ spin_unlock_irqrestore(&ioc->lock, flags);
}
kmem_cache_free(iocontext_cachep, ioc);
/**
* put_io_context - put a reference of io_context
* @ioc: io_context to put
- * @locked_q: request_queue the caller is holding queue_lock of (hint)
*
* Decrement reference count of @ioc and release it if the count reaches
- * zero. If the caller is holding queue_lock of a queue, it can indicate
- * that with @locked_q. This is an optimization hint and the caller is
- * allowed to pass in %NULL even when it's holding a queue_lock.
+ * zero.
*/
-void put_io_context(struct io_context *ioc, struct request_queue *locked_q)
+void put_io_context(struct io_context *ioc)
{
- struct request_queue *last_q = locked_q;
unsigned long flags;
if (ioc == NULL)
return;
BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
- if (locked_q)
- lockdep_assert_held(locked_q->queue_lock);
-
- if (!atomic_long_dec_and_test(&ioc->refcount))
- return;
/*
- * Destroy @ioc. This is a bit messy because icq's are chained
- * from both ioc and queue, and ioc->lock nests inside queue_lock.
- * The inner ioc->lock should be held to walk our icq_list and then
- * for each icq the outer matching queue_lock should be grabbed.
- * ie. We need to do reverse-order double lock dancing.
- *
- * Another twist is that we are often called with one of the
- * matching queue_locks held as indicated by @locked_q, which
- * prevents performing double-lock dance for other queues.
- *
- * So, we do it in two stages. The fast path uses the queue_lock
- * the caller is holding and, if other queues need to be accessed,
- * uses trylock to avoid introducing locking dependency. This can
- * handle most cases, especially if @ioc was performing IO on only
- * single device.
- *
- * If trylock doesn't cut it, we defer to @ioc->release_work which
- * can do all the double-locking dancing.
+ * Releasing ioc requires reverse order double locking and we may
+ * already be holding a queue_lock. Do it asynchronously from wq.
*/
- spin_lock_irqsave_nested(&ioc->lock, flags,
- ioc_release_depth(locked_q));
-
- while (!hlist_empty(&ioc->icq_list)) {
- struct io_cq *icq = hlist_entry(ioc->icq_list.first,
- struct io_cq, ioc_node);
- struct request_queue *this_q = icq->q;
-
- if (this_q != last_q) {
- if (last_q && last_q != locked_q)
- spin_unlock(last_q->queue_lock);
- last_q = NULL;
-
- if (!spin_trylock(this_q->queue_lock))
- break;
- last_q = this_q;
- continue;
- }
- ioc_exit_icq(icq);
+ 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);
+ spin_unlock_irqrestore(&ioc->lock, flags);
}
-
- if (last_q && last_q != locked_q)
- spin_unlock(last_q->queue_lock);
-
- spin_unlock_irqrestore(&ioc->lock, flags);
-
- /* if no icq is left, we're done; otherwise, kick release_work */
- if (hlist_empty(&ioc->icq_list))
- kmem_cache_free(iocontext_cachep, ioc);
- else
- schedule_work(&ioc->release_work);
}
EXPORT_SYMBOL(put_io_context);
task_unlock(task);
atomic_dec(&ioc->nr_tasks);
- put_io_context(ioc, NULL);
+ put_io_context(ioc);
}
/**
git.openpandora.org / pandora-kernel.git / blobdiff