Commit 4ebc1c61 authored Aug 18, 2015 by Tejun Heo Committed by Jens Axboe Aug 18, 2015

cfq-iosched: simplify control flow in cfq_get_queue()



cfq_get_queue()'s control flow looks like the following.

	async_cfqq = NULL;
	cfqq = NULL;

	if (!is_sync) {
		...
		async_cfqq = ...;
		cfqq = *async_cfqq;
	}

	if (!cfqq)
		cfqq = ...;

	if (!is_sync && !(*async_cfqq))
		...;

The only thing the local variable init, the second if, and the
async_cfqq test in the third if achieves is to skip cfqq creation and
installation if *async_cfqq was already non-NULL.  This is needlessly
complicated with different tests examining the same condition.
Simplify it to the following.

	if (!is_sync) {
		...
		async_cfqq = ...;
		cfqq = *async_cfqq;
		if (cfqq)
			goto out;
	}

	cfqq = ...;

	if (!is_sync)
		...;
 out:

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent 5634cc2a

block/cfq-iosched.c

+7 −6

Original line number	Diff line number	Diff line
		@@ -3731,8 +3731,8 @@ cfq_get_queue(struct cfq_data cfqd, bool is_sync, struct cfq_io_cq cic,
		{
		int ioprio_class = IOPRIO_PRIO_CLASS(cic->ioprio);
		int ioprio = IOPRIO_PRIO_DATA(cic->ioprio);
		struct cfq_queue **async_cfqq = NULL;
		struct cfq_queue *cfqq = NULL;
		struct cfq_queue **async_cfqq;
		struct cfq_queue *cfqq;

		if (!is_sync) {
		if (!ioprio_valid(cic->ioprio)) {
		@@ -3742,19 +3742,20 @@ cfq_get_queue(struct cfq_data cfqd, bool is_sync, struct cfq_io_cq cic,
		}
		async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
		cfqq = *async_cfqq;
		if (cfqq)
		goto out;
		}

		if (!cfqq)
		cfqq = cfq_find_alloc_queue(cfqd, is_sync, cic, bio, gfp_mask);

		/*
		* pin the queue now that it's allocated, scheduler exit will prune it
		*/
		if (!is_sync && !(*async_cfqq)) {
		if (!is_sync) {
		cfqq->ref++;
		*async_cfqq = cfqq;
		}

		out:
		cfqq->ref++;
		return cfqq;
		}