Commit a43f085f authored by John Ogness's avatar John Ogness Committed by Jens Axboe
Browse files

block: remove unnecessary ioc nested locking 



The legacy CFQ IO scheduler could call put_io_context() in its exit_icq()
elevator callback. This led to a lockdep warning, which was fixed in
commit d8c66c5d ("block: fix lockdep warning on io_context release
put_io_context()") by using a nested subclass for the ioc spinlock.
However, with commit f382fb0b ("block: remove legacy IO schedulers")
the CFQ IO scheduler no longer exists.

The BFQ IO scheduler also implements the exit_icq() elevator callback but
does not call put_io_context().

The nested subclass for the ioc spinlock is no longer needed. Since it
existed as an exception and no longer applies, remove the nested subclass
usage.

Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarDaniel Wagner <dwagner@suse.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 5b642d8b

block/blk-ioc.c

+6 −20
Original line number Diff line number Diff line
@@ -96,15 +96,7 @@ static void ioc_release_fn(struct work_struct *work) 
{

	struct io_context *ioc = container_of(work, struct io_context,

					      release_work);

	unsigned long flags;



	/*

	 * 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);

	spin_lock_irq(&ioc->lock);



	while (!hlist_empty(&ioc->icq_list)) {

		struct io_cq *icq = hlist_entry(ioc->icq_list.first,
@@ -115,13 +107,13 @@ static void ioc_release_fn(struct work_struct *work) 
			ioc_destroy_icq(icq);

			spin_unlock(&q->queue_lock);

		} else {

			spin_unlock_irqrestore(&ioc->lock, flags);

			spin_unlock_irq(&ioc->lock);

			cpu_relax();

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

			spin_lock_irq(&ioc->lock);

		}

	}



	spin_unlock_irqrestore(&ioc->lock, flags);

	spin_unlock_irq(&ioc->lock);



	kmem_cache_free(iocontext_cachep, ioc);

}
@@ -170,7 +162,6 @@ void put_io_context(struct io_context *ioc) 
 */

void put_io_context_active(struct io_context *ioc)

{

	unsigned long flags;

	struct io_cq *icq;



	if (!atomic_dec_and_test(&ioc->active_ref)) {
@@ -178,19 +169,14 @@ void put_io_context_active(struct io_context *ioc) 
		return;

	}



	/*

	 * Need ioc lock to walk icq_list and q lock to exit icq.  Perform

	 * reverse double locking.  Read comment in ioc_release_fn() for

	 * explanation on the nested locking annotation.

	 */

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

	spin_lock_irq(&ioc->lock);

	hlist_for_each_entry(icq, &ioc->icq_list, ioc_node) {

		if (icq->flags & ICQ_EXITED)

			continue;



		ioc_exit_icq(icq);

	}

	spin_unlock_irqrestore(&ioc->lock, flags);

	spin_unlock_irq(&ioc->lock);



	put_io_context(ioc);

}