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Commit 2274b029 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

block: simplify ioc_release_fn() 



Reverse double lock dancing in ioc_release_fn() can be simplified by
just using trylock on the queue_lock and back out from ioc lock on
trylock failure.  Simplify it.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Tested-by: default avatarShaohua Li <shaohua.li@intel.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent d705ae6b

block/blk-ioc.c

+10 −36
Original line number Diff line number Diff line
@@ -79,7 +79,6 @@ static void ioc_release_fn(struct work_struct *work) 
{

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

					      release_work);

	struct request_queue *last_q = NULL;

	unsigned long flags;



	/*
@@ -93,44 +92,19 @@ static void ioc_release_fn(struct work_struct *work) 
	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) {

			/*

			 * Need to switch to @this_q.  Once we release

			 * @ioc->lock, it can go away along with @cic.

			 * Hold on to it.

			 */

			__blk_get_queue(this_q);

		struct request_queue *q = icq->q;



			/*

			 * blk_put_queue() might sleep thanks to kobject

			 * idiocy.  Always release both locks, put and

			 * restart.

			 */

			if (last_q) {

				spin_unlock(last_q->queue_lock);

				spin_unlock_irqrestore(&ioc->lock, flags);

				blk_put_queue(last_q);

		if (spin_trylock(q->queue_lock)) {

			ioc_exit_icq(icq);

			spin_unlock(q->queue_lock);

		} else {

			spin_unlock_irqrestore(&ioc->lock, flags);

			cpu_relax();

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

		}



			last_q = this_q;

			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_irqrestore(&ioc->lock, flags);

		blk_put_queue(last_q);

	} else {

		spin_unlock_irqrestore(&ioc->lock, flags);

	}



	kmem_cache_free(iocontext_cachep, ioc);

}